Pharmacological Effects of Botanical Drugs on Myocardial Metabolism in Chronic Heart Failure

Although there have been significant advances in the treatment of heart failure in recent years, chronic heart failure remains a leading cause of cardiovascular disease-related death. Many studies have found that targeted cardiac metabolic remodeling has good potential for the treatment of heart failure. However, most of the drugs that increase cardiac energy are still in the theoretical or testing stage. Some research has found that botanical drugs not only increase myocardial energy metabolism through multiple targets but also have the potential to restore the balance of myocardial substrate metabolism. In this review, we summarized the mechanisms by which botanical drugs (the active ingredients/formulas/Chinese patent medicines) improve substrate utilization and promote myocardial energy metabolism by activating AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptors (PPARs) and other related targets. At the same time, some potential protective effects of botanical drugs on myocardium, such as alleviating oxidative stress and dysbiosis signaling, caused by metabolic disorders, were briefly discussed.

Assessing a Myocardial Area at Risk in Non-ST Elevation Acute Myocardial Infarction Without Wall Motion Abnormalities Using Cardiac Magnetic Resonance and Radionuclide Imaging

Evaluation of a myocardial area at risk is clinically important because it contributes to clinical decision-making and management of patients with acute myocardial infarction (AMI). Herein, we reported a case of non-ST-elevation AMI (non-STEMI) without wall motion abnormalities on echocardiography, in which the myocardial area at risk was evaluated by two modalities; cardiac magnetic resonance (CMR) and radionuclide imaging. Coronary angiography revealed significant luminal stenosis in the diagonal branch and the obtuse marginal branch. It remained unclear which branch was the culprit. T2-weighted CMR revealed myocardial edema in the left ventricular anterolateral area. Based on the extent of myocardial edema, the patient was diagnosed with non-STEMI in the area corresponding to the diagonal branch. The area exhibiting impaired fatty acid metabolism on iodine-123-beta-methyl-p-iodophenyl penta-decanoic acid (123I-BMIPP) imaging matched well with the area showing myocardial edema on T2-weighted CMR. In conclusion, both CMR and BMIPP imaging are powerful tools in identifying a myocardial area at risk even in non-STEMI without wall motion abnormalities. This should contribute to clinical decision-making and management of patients with AMI.

The Role of Ranolazine in Heart Failure-Current Concepts

Heart failure is a complex clinical syndrome with a detrimental impact on mortality and morbidity. Energy substrate utilization and myocardial ion channel regulation have gained research interest especially after the introduction of sodium-glucose co-transporter 2 inhibitors in the treatment of heart failure. Ranolazine or N-(2,6-dimethylphenyl)-2-(4-[2-hydroxy-3-(2-methoxyphenoxy) propyl] piperazin-1-yl) acetamide hydrochloride is an active piperazine derivative which inhibits late sodium current thus minimizing calcium overload in the ischemic cardiomyocytes. Ranolazine also prevents fatty acid oxidation and favors glycose utilization ameliorating the "energy starvation" of the failing heart. Heart failure with preserved ejection fraction is characterized by diastolic impairment; according to the literature ranolazine could be beneficial in the management of increased left ventricular end-diastolic pressure, right ventricular systolic dysfunction and wall shear stress which is reflected by the high natriuretic peptides. Fewer data is evident regarding the effects of ranolazine in heart failure with reduced ejection fraction and mainly support the control of the sodium-calcium exchanger and function of sarcoendoplasmic reticulum calcium adenosine triphosphatase. Ranolazine's therapeutic mechanisms in myocardial ion channels and energy utilization are documented in patients with chronic coronary syndromes. Nevertheless, ranolazine might have a broader effect in the therapy of heart failure and further mechanistic research is required.

Quantitative Profiling of Serum Carnitines Facilitates the Etiology Diagnosis and Prognosis Prediction in Heart Failure

BACKGROUND

The perturbation of fatty acid metabolism in heart failure (HF) has been a critical issue. It is unclear whether the amounts of circulating carnitines will benefit primary etiology diagnosis and prognostic prediction in HF. This study was designed to assess the diagnostic and prognostic values of serum carnitine profiles between ischemic and non-ischemic derived heart failure.

METHODS

HF patients (non-ischemic dilated cardiomyopathy: DCM-HF, n = 98; ischemic heart disease: IHD-HF, n = 63) and control individuals (n = 48) were enrolled consecutively. The serum carnitines were quantitatively measured using the UHPLC-MS/MS method. All patients underwent a median follow-up of 28.3 months. Multivariate Cox regression analysis was performed during the prognosis evaluation.

RESULTS

Amongst 25 carnitines measured, all of them were increased in HF patients, and 20 acylcarnitines were associated with HF diagnosis independently. Seven acylcarnitines were confirmed to increase the probability of DCM diagnosis independently. The addition of isobutyryl-L-carnitine and stearoyl-L-carnitine to conventional clinical factors significantly improved the area under the receiver operating characteristic curve (ROC) from 0.771 to 0.832 (p = 0.023) for DCM-HF diagnosis (calibration test for the composite model: Hosmer-Lemeshow χ² = 7.376, p = 0.497 > 0.05). Using a multivariate COX survival analysis adjusted with clinical factors simultaneously, oleoyl L-carnitine >300 nmol/L (HR = 2.364, 95% CI = 1.122-4.976, p = 0.024) and isovaleryl-L-carnitine <100 nmol/L (HR = 2.108, 95% CI = 1.091-4.074, p = 0.026) increased the prediction of all-cause mortality independently, while linoleoyl-L-carnitine >420 nmol/L, succinyl carnitine >60 nmol/L and isovaleryl-L-carnitine <100 nmol/L increased the risk of HF rehospitalization independently.

CONCLUSIONS

Serum carnitines could not only serve as diagnostic and predictive biomarkers in HF but also benefit the identification of HF primary etiology and prognosis.

Progressive Cardiac Metabolic Defects Accompany Diastolic and Severe Systolic Dysfunction in Spontaneously Hypertensive Rat Hearts

Background Cardiac metabolic abnormalities are present in heart failure. Few studies have followed metabolic changes accompanying diastolic and systolic heart failure in the same model. We examined metabolic changes during the development of diastolic and severe systolic dysfunction in spontaneously hypertensive rats (SHR). Methods and Results We serially measured myocardial glucose uptake rates with dynamic 2-[18F] fluoro-2-deoxy-d-glucose positron emission tomography in vivo in 9-, 12-, and 18-month-old SHR and Wistar Kyoto rats. Cardiac magnetic resonance imaging determined systolic function (ejection fraction) and diastolic function (isovolumetric relaxation time) and left ventricular mass in the same rats. Cardiac metabolomics was performed at 12 and 18 months in separate rats. At 12 months, SHR hearts, compared with Wistar Kyoto hearts, demonstrated increased isovolumetric relaxation time and slightly reduced ejection fraction indicating diastolic and mild systolic dysfunction, respectively, and higher (versus 9-month-old SHR decreasing) 2-[18F] fluoro-2-deoxy-d-glucose uptake rates (Ki). At 18 months, only few SHR hearts maintained similar abnormalities as 12-month-old SHR, while most exhibited severe systolic dysfunction, worsening diastolic function, and markedly reduced 2-[18F] fluoro-2-deoxy-d-glucose uptake rates. Left ventricular mass normalized to body weight was elevated in SHR, more pronounced with severe systolic dysfunction. Cardiac metabolite changes differed between SHR hearts at 12 and 18 months, indicating progressive defects in fatty acid, glucose, branched chain amino acid, and ketone body metabolism. Conclusions Diastolic and severe systolic dysfunction in SHR are associated with decreasing cardiac glucose uptake, and progressive abnormalities in metabolite profiles. Whether and which metabolic changes trigger progressive heart failure needs to be established.

Oral ketone esters acutely improve myocardial contractility in post-hospitalized COVID-19 patients: A randomized placebo-controlled double-blind crossover study

Background

COVID-19 is associated with subclinical myocardial injury. Exogenous ketone esters acutely improve left myocardial function in healthy participants and patients with heart failure, but the effects have not been investigated in participants previously hospitalized for COVID-19.

Methods

This is a randomized placebo-controlled double-blind crossover study comparing a single oral ketone ester dose of 395 mg/kg with placebo. Fasting participants were randomized to either placebo in the morning and oral ketone ester in the afternoon or vice versa. Echocardiography was performed immediately after intake of the corresponding treatment. Primary outcome was left ventricular ejection fraction (LVEF). Secondary outcomes were absolute global longitudinal strain (GLS), cardiac output and blood oxygen saturation. Linear mixed effects models were used to assess differences.

Results

We included 12 participants previously hospitalized for COVID-19 with a mean (±SD) age of 60 ± 10 years. The mean time from hospitalization was 18 ± 5 months. Oral ketone esters did not increase LVEF between placebo and oral ketone ester [mean difference: -0.7% (95% CI -4.0 to 2.6%), p = 0.66], but increased GLS [1.9% (95% CI: 0.1 to 3.6%), p = 0.04] and cardiac output [1.2 L/min (95% CI: -0.1 to 2.4 L/min), p = 0.07], although non-significant. The differences in GLS remained significant after adjustment for change in heart rate (p = 0.01). There was no difference in blood oxygen saturation. Oral ketone esters increased blood ketones over time (peak level 3.1 ± 4.9 mmol/L, p < 0.01). Ketone esters increased blood insulin, c-peptide, and creatinine, and decreased glucose and FFA (all p ≤ 0.01) but did not affect glucagon, pro-BNP, or troponin I levels (all p > 0.05).

Conclusion

In patients previously hospitalized with COVID-19, a single oral dose of ketone ester had no effect on LVEF, cardiac output or blood oxygen saturation, but increased GLS acutely.

Clinical trial registration

https://clinicaltrials.gov/, identifier NCT04377035.

Left ventricular assist device mode: Co-pulse left ventricular unloading in a working mode of ex vivo heart perfusion

BACKGROUND

For normothermic ex vivo heart perfusion (EVHP), a resting mode and working mode have been proposed. We newly developed a left ventricular assist device (LVAD) mode that supports heart contraction by co-pulse synchronized LVAD.

METHODS

Following resting mode during time 0 to 1 hour, pig hearts (n = 18) were perfused in either resting, working, or LVAD mode during time 1 to 5 hour, and then myocardial function was evaluated in working mode at 6 hour. The preservation ratio was defined as the myocardial mechanical function at 330 minute divided by the function at 75 minute. In LVAD mode, LVAD unloaded the pressure and the volume in the left ventricle in the systolic phase.

RESULTS

The LVAD group was significantly associated with higher preservation ratios in cardiac output (resting, 33 ± 3; working, 35 ± 5; LVAD, 76% ± 5%; p < 0.001), stroke work, dP/dt maximum, and dP/dt minimum compared with the other groups. Glucose consumption was significantly reduced in the resting group. The LVAD group was significantly associated with higher myocardial oxygen consumption (resting, 2.2 ± 0.3; working; 4.6 ± 0.5; LVAD, 6.1 ± 0.5 mL O₂/min/100 g, p < 0.001) and higher adenosine triphosphate (ATP) levels (resting, 1.1 ± 0.1; working, 0.7 ± 0.1; LVAD, 1.6 ± 0.2 μmol/g, p = 0.001) compared with the others.

CONCLUSION

These data suggest that myocardial mechanical function was better preserved in LVAD mode than in resting and working modes. Although our data suggested similar glycolysis activity in the LVAD and working groups, the higher final ATP in the LVAD group might be explained by reduced external work in LVAD.

Insights Into the Metabolic Aspects of Aortic Stenosis With the Use of Magnetic Resonance Imaging

Pressure overload in aortic stenosis (AS) encompasses both structural and metabolic remodeling and increases the risk of decompensation into heart failure. A major component of metabolic derangement in AS is abnormal cardiac substrate use, with down-regulation of fatty acid oxidation, increased reliance on glucose metabolism, and subsequent myocardial lipid accumulation. These changes are associated with energetic and functional cardiac impairment in AS and can be assessed with the use of cardiac magnetic resonance spectroscopy (MRS). Proton MRS allows the assessment of myocardial triglyceride content and creatine concentration. Phosphorous MRS allows noninvasive in vivo quantification of the phosphocreatine-to-adenosine triphosphate ratio, a measure of cardiac energy status that is reduced in patients with severe AS. This review summarizes the changes to cardiac substrate and high-energy phosphorous metabolism and how they affect cardiac function in AS. The authors focus on the role of MRS to assess these metabolic changes, and potentially guide future (cellular) metabolic therapy in AS.

Right ventricular energy metabolism in a porcine model of acute right ventricular pressure overload after weaning from cardiopulmonary bypass

Acute right ventricular pressure overload (RVPO) occurs following congenital heart surgery and often results in low cardiac output syndrome. We tested the hypothesis that the RV exhibits limited ability to modify substrate utilization in response to increasing energy requirements during acute RVPO after cardiopulmonary bypass (CPB). We assessed the RV fractional contributions (Fc) of substrates to the citric acid cycle in juvenile pigs exposed to acute RVPO by pulmonary artery banding (PAB) and CPB. Sixteen Yorkshire male pigs (median 38 days old, 12.2 kg of body weight) were randomized to SHAM (Ctrl, n = 5), 2-h CPB (CPB, n = 5) or CPB with PAB (PAB-CPB, n = 6). Carbon-13 (13 C)-labeled lactate, medium-chain, and mixed long-chain fatty acids (MCFA and LCFAs) were infused as metabolic tracers for energy substrates. After weaning from CPB, RV systolic pressure (RVSP) doubled baseline in PAB-CPB while piglets in CPB group maintained normal RVSP. Fc-LCFAs decreased significantly in order PAB-CPB > CPB > Ctrl groups by 13 C-NMR. Fc-lactate and Fc-MCFA were similar among the three groups. Intragroup analysis for PAB-CPB showed that the limited Fc-LCFAs appeared prominently in piglets exposed to high RVSP-to-left ventricular systolic pressure ratio and high RV rate-pressure product, an indicator of myocardial oxygen demand. Acute RVPO after CPB strongly inhibits LCFA oxidation without compensation by lactate oxidation, resulting in energy deficiency as determined by lower (phosphocreatine)/(adenosine triphosphate) in PAB-CPB. Adequate energy supply but also metabolic interventions may be required to circumvent these RV energy metabolic abnormalities during RVPO after CPB.

Chimeric Agonist of Galanin Receptor GALR2 Reduces Heart Damage in Rats with Streptozotocin-Induced Diabetes

Neuropeptide galanin and its N-terminal fragments reduce the generation of reactive oxygen species and normalize metabolic and antioxidant states of myocardium in experimental cardiomyopathy and ischemia/reperfusion injury. The aim of this study was to elucidate the effect of WTLNSAGYLLGPβAH-OH (peptide G), a pharmacological agonist of the galanin receptor GalR2, on the cardiac injury induced by administration of streptozotocin (STZ) in rats. Peptide G was prepared by solid phase peptide synthesis using the Fmoc strategy and purified by preparative HPLC; its structure was confirmed by 1H-NMR spectroscopy and MALDI-TOF mass spectrometry. Experimental animals were randomly distributed into five groups: C, control; S, STZ-treated; SG10, STZ + peptide G (10 nmol/kg/day); SG50, STZ + peptide G (50 nmol/kg/day); G, peptide G (50 nmol/kg/day). Administration of peptide G prevented hyperglycemia in SG50 rats. By the end of the experiment, the ATP content, total pool of adenine nucleotides, phosphocreatine (PCr) content, and PCr/ATP ratio in the myocardium of animals of the SG50 group were significantly higher than in rats of the S group. In the SG50 and SG10 groups, the content of lactate and lactate/pyruvate ratio in the myocardium were reduced, while the glucose content was increased vs. the S group. Both doses of peptide G reduced the activation of creatine kinase-MB and lactate dehydrogenase, as well as the concentration of thiobarbituric acid reactive products in the blood plasma of STZ-treated rats to the control values. Taken together, these results suggest that peptide G has cardioprotective properties in type 1 diabetes mellitus. Possible mechanisms of peptide G action in the STZ-induced diabetes are discussed.

New insights into the role of melatonin in diabetic cardiomyopathy

Diabetic cardiovascular complications and impaired cardiac function are considered to be the main causes of death in diabetic patients worldwide, especially patients with type 2 diabetes mellitus (T2DM). An increasing number of studies have shown that melatonin, as the main product secreted by the pineal gland, plays a vital role in the occurrence and development of diabetes. Melatonin improves myocardial cell metabolism, reduces vascular endothelial cell death, reverses microcirculation disorders, reduces myocardial fibrosis, reduces oxidative and endoplasmic reticulum stress, regulates cell autophagy and apoptosis, and improves mitochondrial function, all of which are the characteristics of diabetic cardiomyopathy (DCM). This review focuses on the role of melatonin in DCM. We also discuss new molecular findings that might facilitate a better understanding of the underlying mechanism. Finally, we propose potential new therapeutic strategies for patients with T2DM.

Novel effects of the gastrointestinal hormone secretin on cardiac metabolism and renal function

The cardiac benefits of gastrointestinal hormones have been of interest in recent years. The aim of this study was to explore the myocardial and renal effects of the gastrointestinal hormone secretin in the GUTBAT trial (NCT03290846). A placebo-controlled crossover study was conducted on 15 healthy males in fasting conditions, where subjects were blinded to the intervention. Myocardial glucose uptake was measured with [18F]2-fluoro-2-deoxy-d-glucose ([18F]FDG) positron emission tomography. Kidney function was measured with [18F]FDG renal clearance and estimated glomerular filtration rate (eGFR). Secretin increased myocardial glucose uptake compared with placebo (secretin vs. placebo, means ± SD, 15.5 ± 7.4 vs. 9.7 ± 4.9 μmol/100 g/min, 95% confidence interval (CI) [2.2, 9.4], P = 0.004). Secretin also increased [18F]FDG renal clearance (44.5 ± 5.4 vs. 39.5 ± 8.5 mL/min, 95%CI [1.9, 8.1], P = 0.004), and eGFR was significantly increased from baseline after secretin, compared with placebo (17.8 ± 9.8 vs. 6.0 ± 5.2 ΔmL/min/1.73 m2, 95%CI [6.0, 17.6], P = 0.001). Our results implicate that secretin increases heart work and renal filtration, making it an interesting drug candidate for future studies in heart and kidney failure.NEW & NOTEWORTHY Secretin increases myocardial glucose uptake compared with placebo, supporting a previously proposed inotropic effect. Secretin also increased renal filtration rate.

Trimetazidine Attenuates Heart Failure by Improving Myocardial Metabolism via AMPK

Energic deficiency of cardiomyocytes is a dominant cause of heart failure. An antianginal agent, trimetazidine improves the myocardial energetic supply. We presumed that trimetazidine protects the cardiomyocytes from the pressure overload-induced heart failure through improving the myocardial metabolism. C57BL/6 mice were subjected to transverse aortic constriction (TAC). After 4 weeks of TAC, heart failure was observed in mice manifested by an increased left ventricular (LV) chamber dimension, an impaired LV ejection fraction evaluated by echocardiography analysis, which were significantly restrained by the treatment of trimetazidine. Trimetazidine restored the mitochondrial morphology and function tested by cardiac transmission electron microscope and mitochondrial dynamic proteins analysis. Positron emission tomography showed that trimetazidine significantly elevated the glucose uptake in TAC mouse heart. Trimetazidine restrained the impairments of the insulin signaling in TAC mice and promoted the translocation of glucose transporter type IV (GLUT4) from the storage vesicle to membrane. However, these cardioprotective effects of trimetazidine in TAC mice were notably abolished by compound C (C.C), a specific AMPK inhibitor. The enlargement of neonatal rat cardiomyocyte induced by mechanical stretch, together with the increased expression of hypertrophy-associated proteins, mitochondria deformation and dysfunction were significantly ameliorated by trimetazidine. Trimetazidine enhanced the isolated cardiomyocyte glucose uptake in vitro. These benefits brought by trimetazidine were also removed with the presence of C.C. In conclusion, trimetazidine attenuated pressure overload-induced heart failure through improving myocardial mitochondrial function and glucose uptake via AMPK.

Effects of Bergamot Polyphenols on Mitochondrial Dysfunction and Sarcoplasmic Reticulum Stress in Diabetic Cardiomyopathy

Cardiovascular disease is the leading cause of death and disability in the Western world. In order to safeguard the structure and the functionality of the myocardium, it is extremely important to adequately support the cardiomyocytes. Two cellular organelles of cardiomyocytes are essential for cell survival and to ensure proper functioning of the myocardium: mitochondria and the sarcoplasmic reticulum. Mitochondria are responsible for the energy metabolism of the myocardium, and regulate the processes that can lead to cell death. The sarcoplasmic reticulum preserves the physiological concentration of the calcium ion, and triggers processes to protect the structural and functional integrity of the proteins. The alterations of these organelles can damage myocardial functioning. A proper nutritional balance regarding the intake of macronutrients and micronutrients leads to a significant improvement in the symptoms and consequences of heart disease. In particular, the Mediterranean diet, characterized by a high consumption of plant-based foods, small quantities of red meat, and high quantities of olive oil, reduces and improves the pathological condition of patients with heart failure. In addition, nutritional support and nutraceutical supplementation in patients who develop heart failure can contribute to the protection of the failing myocardium. Since polyphenols have numerous beneficial properties, including anti-inflammatory and antioxidant properties, this review gathers what is known about the beneficial effects of polyphenol-rich bergamot fruit on the cardiovascular system. In particular, the role of bergamot polyphenols in mitochondrial and sarcoplasmic dysfunctions in diabetic cardiomyopathy is reported.

Therapeutic Manipulation of Myocardial Metabolism: JACC State-of-the-Art Review

The mechanisms responsible for the positive and unexpected cardiovascular effects of sodium-glucose cotransporter-2 inhibitors and glucagon-like peptide-1 receptor agonists in patients with type 2 diabetes remain to be defined. It is likely that some of the beneficial cardiac effects of these antidiabetic drugs are mediated, in part, by altered myocardial metabolism. Common cardiometabolic disorders, including the metabolic (insulin resistance) syndrome and type 2 diabetes, are associated with altered substrate utilization and energy transduction by the myocardium, predisposing to the development of heart disease. Thus, the failing heart is characterized by a substrate shift toward glycolysis and ketone oxidation in an attempt to meet the high energetic demand of the constantly contracting heart. This review examines the metabolic pathways and clinical implications of myocardial substrate utilization in the normal heart and in cardiometabolic disorders, and discusses mechanisms by which antidiabetic drugs and metabolic interventions improve cardiac function in the failing heart.

Quantification of Myocardial Creatine and Triglyceride Content in the Human Heart: Precision and Accuracy of in vivo Proton Magnetic Resonance Spectroscopy

Background

Proton magnetic resonance spectroscopy (¹H‐MRS) of the human heart is deemed to be a quantitative method to investigate myocardial metabolite content, but thorough validations of in vivo measurements against invasive techniques are lacking.

Purpose

To determine measurement precision and accuracy for quantifications of myocardial total creatine and triglyceride content with localized ¹H‐MRS.

Study type

Test–retest repeatability and measurement validation study.

Subjects

Sixteen volunteers and 22 patients scheduled for open‐heart aortic valve replacement or septal myectomy.

Field Strength/Sequence

Prospectively ECG‐triggered respiratory‐gated free‐breathing single‐voxel point‐resolved spectroscopy (PRESS) sequence at 3 T.

Assessment

Myocardial total creatine and triglyceride content were quantified relative to the total water content by fitting the ¹H‐MR spectra. Precision was assessed with measurement repeatability. Accuracy was assessed by validating in vivo ¹H‐MRS measurements against biochemical assays in myocardial tissue from the same subjects.

Statistical Tests

Intrasession and intersession repeatability was assessed using Bland–Altman analyses. Agreement between ¹H‐MRS measurements and biochemical assay was tested with regression analyses.

Results

The intersession repeatability coefficient for myocardial total creatine content was 41.8% with a mean value of 0.083% ± 0.020% of the total water signal, and 36.7% for myocardial triglyceride content with a mean value of 0.35% ± 0.13% of the total water signal. Ex vivo myocardial total creatine concentrations in tissue samples correlated with the in vivo myocardial total creatine content measured with ¹H‐MRS: n = 22, r = 0.44; P < 0.05. Likewise, ex vivo myocardial triglyceride concentrations correlated with the in vivo myocardial triglyceride content: n = 20, r = 0.50; P < 0.05.

Data Conclusion

We validated the use of localized ¹H‐MRS of the human heart at 3 T for quantitative assessments of in vivo myocardial tissue metabolite content by estimating the measurement precision and accuracy.

Level of Evidence

2

Technical Efficacy Stage

2

The Degree of Cardiac Remodelling before Overload Relief Triggers Different Transcriptome and miRome Signatures during Reverse Remodelling (RR)-Molecular Signature Differ with the Extent of RR

This study aims to provide new insights into transcriptome and miRome modifications occurring in cardiac reverse remodelling (RR) upon left ventricle pressure-overload relief in mice. Pressure-overload was established in seven-week-old C57BL/6J-mice by ascending aortic constriction. A debanding (DEB) surgery was performed seven weeks later in half of the banding group (BA). Two weeks later, cardiac function was evaluated through hemodynamics and echocardiography, and the hearts were collected for histology and small/bulk-RNA-sequencing. Pressure-overload relief was confirmed by the normalization of left-ventricle-end-systolic-pressure. DEB animals were separated into two subgroups according to the extent of cardiac remodelling at seven weeks and RR: DEB1 showed an incomplete RR phenotype confirmed by diastolic dysfunction persistence (E/e' ≥ 16 ms) and increased myocardial fibrosis. At the same time, DEB2 exhibited normal diastolic function and fibrosis, presenting a phenotype closer to myocardial recovery. Nevertheless, both subgroups showed the persistence of cardiomyocytes hypertrophy. Notably, the DEB1 subgroup presented a more severe diastolic dysfunction at the moment of debanding than the DEB2, suggesting a different degree of cardiac remodelling. Transcriptomic and miRomic data, as well as their integrated analysis, revealed significant downregulation in metabolic and hypertrophic related pathways in DEB1 when compared to DEB2 group, including fatty acid β-oxidation, mitochondria L-carnitine shuttle, and nuclear factor of activated T-cells pathways. Moreover, extracellular matrix remodelling, glycan metabolism and inflammation-related pathways were up-regulated in DEB1. The presence of a more severe diastolic dysfunction at the moment of pressure overload-relief on top of cardiac hypertrophy was associated with an incomplete RR. Our transcriptomic approach suggests that a cardiac inflammation, fibrosis, and metabolic-related gene expression dysregulation underlies diastolic dysfunction persistence after pressure-overload relief, despite left ventricular mass regression, as echocardiographically confirmed.

Increased myocardial 18F-FDG uptake as a marker of Doxorubicin-induced oxidative stress

BACKGROUND

Oxidative stress and its interference on myocardial metabolism play a major role in Doxorubicin (DXR) cardiotoxic cascade.

METHODS

Mice models of neuroblastoma (NB) were treated with 5 mg DXR/kg, either free (Free-DXR) or encapsulated in untargeted (SL[DXR]) or in NB-targeting Stealth Liposomes (pep-SL[DXR] and TP-pep-SL[DXR]). Control mice received saline. FDG-PET was performed at baseline (PET1) and 7 days after therapy (PET2). At PET2 Troponin-I and NT-proBNP were assessed. Explanted hearts underwent biochemical, histological, and immunohistochemical analyses. Finally, FDG uptake and glucose consumption were simultaneously measured in cultured H9c2 in the presence/absence of Free-DXR (1 μM).

RESULTS

Free-DXR significantly enhanced the myocardial oxidative stress. Myocardial-SUV remained relatively stable in controls and mice treated with liposomal formulations, while it significantly increased at PET2 with respect to baseline in Free-DXR. At this timepoint, myocardial-SUV was directly correlated with both myocardial redox stress and hexose-6-phosphate-dehydrogenase (H6PD) enzymatic activity, which selectively sustain cellular anti-oxidant mechanisms. Intriguingly, in vitro, Free-DXR selectively increased FDG extraction fraction without altering the corresponding value for glucose.

CONCLUSION

The direct correlation between cardiac FDG uptake and oxidative stress indexes supports the potential role of FDG-PET as an early biomarker of DXR oxidative damage.

Empagliflozin Ameliorates Diastolic Dysfunction and Left Ventricular Fibrosis/Stiffness in Nondiabetic Heart Failure: A Multimodality Study

OBJECTIVES

The purpose of this study was to investigate the effect of empagliflozin on diastolic function in a nondiabetic heart failure with reduced ejection fraction (HFrEF) scenario and on the pathways causing diastolic dysfunction.

BACKGROUND

This group demonstrated that empagliflozin ameliorates adverse cardiac remodeling, enhances myocardial energetics, and improves left ventricular systolic function in a nondiabetic porcine model of HF. Whether empagliflozin also improves diastolic function remains unknown. Hypothetically, empagliflozin would improve diastolic function in HF mediated both by a reduction in interstitial myocardial fibrosis and an improvement in cardiomyocyte stiffness (titin phosphorylation).

METHODS

HF was induced in nondiabetic pigs by 2-h balloon occlusion of proximal left anterior descending artery. Animals were randomized to empagliflozin or placebo for 2 months. Cardiac function was evaluated with cardiac magnetic resonance (CMR), 3-dimensional echocardiography, and invasive hemodynamics. In vitro relaxation of cardiomyocytes was studied in primary culture. Myocardial samples were obtained for histological and molecular evaluation. Myocardial metabolite consumption was analyzed by simultaneous blood sampling from coronary artery and coronary sinus.

RESULTS

Despite similar initial ischemic myocardial injury, the empagliflozin group showed significantly improved diastolic function at 2 months, assessed by conventional echocardiography (higher e' and color M-mode propagation velocity, lower E/e' ratio, myocardial performance Tei index, isovolumic relaxation time, and left atrial size), echocardiography-derived strain imaging (strain imaging diastolic index, strain rate at isovolumic relaxation time and during early diastole, and untwisting), and CMR (higher peak filling rate, larger first filling volume). Invasive hemodynamics confirmed improved diastolic function with empagliflozin (better peak LV pressure rate of decay (-dP/dt), shorter Tau, lower end-diastolic pressure-volume relationship (EDPVR), and reduced filling pressures). Empagliflozin reduced interstitial myocardial fibrosis at the imaging, histological and molecular level. Empagliflozin improved nitric oxide signaling (endothelial nitric oxide synthetase [eNOS] activity, nitric oxide [NO] availability, cyclic guanosine monophosphate (cGMP) content, protein kinase G [PKG] signaling) and enhanced titin phosphorylation (which is responsible for cardiomyocyte stiffness). Indeed, isolated cardiomyocytes exhibited better relaxation in empagliflozin-treated animals. Myocardial consumption of glucose and ketone bodies negatively and positively correlated with diastolic function, respectively.

CONCLUSIONS

Empagliflozin ameliorates diastolic function in a nondiabetic HF porcine model, mitigates histological and molecular remodeling, and reduces both left ventricle and cardiomyocyte stiffness.

Metabolic Changes in Spontaneously Hypertensive Rat Hearts Precede Cardiac Dysfunction and Left Ventricular Hypertrophy

Background

Sustained pressure overload leads to changes in cardiac metabolism, function, and structure. Both time course and causal relationships between these changes are not fully understood. Therefore, we studied spontaneously hypertensive rats (SHR) during early hypertension development and compared them to control Wistar Kyoto rats.

Methods and Results

We serially evaluated myocardial glucose uptake rates (Ki) with dynamic 2‐[¹⁸F] fluoro‐2‐deoxy‐D‐glucose positron emission tomography, and ejection fraction and left ventricular mass to body weight ratios with cardiac magnetic resonance imaging in vivo, determined glucose uptake and oxidation rates in isolated perfused hearts, and analyzed metabolites, mammalian target of rapamycin activity and endoplasmic reticulum stress in dissected hearts. When compared with Wistar Kyoto rats, SHR demonstrated increased glucose uptake rates (Ki) in vivo, and reduced ejection fraction as early as 2 months of age when hypertension was established. Isolated perfused SHR hearts showed increased glucose uptake and oxidation rates starting at 1 month. Cardiac metabolite analysis at 2 months of age revealed elevated pyruvate, fatty acyl‐ and branched chain amino acid‐derived carnitines, oxidative stress, and inflammation. Mammalian target of rapamycin activity increased in SHR beginning at 2 months. Left ventricular mass to body weight ratios and endoplasmic reticulum stress were elevated in 5 month‐old SHR.

Conclusions

Thus, in a genetic hypertension model, chronic cardiac pressure overload promptly leads to increased myocardial glucose uptake and oxidation, and to metabolite abnormalities. These coincide with, or precede, cardiac dysfunction while left ventricular hypertrophy develops only later. Myocardial metabolic changes may thus serve as early diagnostic markers for hypertension‐induced left ventricular hypertrophy.

Exercise Training Adds Cardiometabolic Benefits of a Paleolithic Diet in Type 2 Diabetes Mellitus

Background

The accumulation of myocardial triglycerides and remodeling of the left ventricle are common features in type 2 diabetes mellitus and represent potential risk factors for the development of diastolic and systolic dysfunction. A few studies have investigated the separate effects of diet and exercise training on cardiac function, but none have investigated myocardial changes in response to a combined diet and exercise intervention. This 12‐week randomized study assessed the effects of a Paleolithic diet, with and without additional supervised exercise training, on cardiac fat, structure, and function.

Methods and Results

Twenty‐two overweight and obese subjects with type 2 diabetes mellitus were randomized to either a Paleolithic diet and standard‐care exercise recommendations (PD) or to a Paleolithic diet plus supervised exercise training 3 hours per week (PD‐EX). This study includes secondary end points related to cardiac structure and function, ie, myocardial triglycerides levels, cardiac morphology, and strain were measured using cardiovascular magnetic resonance, including proton spectroscopy, at baseline and after 12 weeks. Both groups showed major favorable metabolic changes. The PD‐EX group showed significant decreases in myocardial triglycerides levels (−45%, P=0.038) and left ventricle mass to end‐diastolic volume ratio (−13%, P=0.008) while the left ventricle end‐diastolic volume and stroke volume increased significantly (+14%, P=0.004 and +17%, P=0.008, respectively). These variables were unchanged in the PD group.

Conclusions

Exercise training plus a Paleolithic diet reduced myocardial triglycerides levels and improved left ventricle remodeling in overweight/obese subjects with type 2 diabetes mellitus.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01513798.

The Mechanisms of Cardiac Protection Using a Synthetic Agonist of Galanin Receptors during Chronic Administration of Doxorubicin

The use of the anticancer drug doxorubicin (Dox) is limited by its cardiotoxic effect. The aim of this work was to study the effect of a new synthetic agonist of the galanin receptor GalR1-3 [βAla14, His15]-galanine (2–15) (G) on the metabolism, antioxidant enzyme activity, and cardiac function in rats with cardiomyopathy (CM) caused by chronic administration of Dox. Coadministration of peptide G and Dox significantly increased the fractional shortening (FS) and ejection fraction (EF) by an average of 30 ± 4% compared with the indices in the Dox group. The reduced severity of cardiac dysfunction under the action of G was accompanied by a 2.5-fold decrease in the activity of creatine kinase-MB (CK-MB) in blood plasma. The protective mechanism of the action of peptide G is caused by a reduced lipid peroxidation (LP) that is due to the increased activity of Cu,Zn superoxide dismutase (Cu,Zn-SOD) and glutathione peroxidase (GSH-Px) in the damaged heart. Administration of peptide G significantly increased the adenine nucleotide pool (ΣAH), ATP content, and the levels of phosphocreatine (PCr) and total creatine (ΣCr) in the damaged myocardium. It also reduced lactate accumulation relative to its content in the Dox group. The better energy supply of cardiomyocytes after treatment with peptide G prevented the accumulation of cytotoxic ammonia and disruption in the metabolism of the key myocardial amino acids (glutamic acid (Glu), aspartic acid (Asp), and alanine (Ala)). Peptide G significantly improved the morphological parameters of the heart in rats treated with Dox. The results show promise in using peptide G to efficiently correct functional, morphological, and metabolic damage to the heart caused by anthracycline chemotherapy.

Myocardial Oxygen Consumption and Efficiency in Patients With Cardiac Amyloidosis

Background

This study evaluated myocardial oxygen consumption (MVO₂) and myocardial external efficiency (MEE) in patients with cardiac amyloidosis (CA). Furthermore, we compared MEE and MVO₂ in subjects with light chain amyloidosis versus transthyretin (ATTR) amyloidosis.

Methods and Results

The study population comprised 40 subjects: 25 patients with confirmed CA and 15 control subjects. All subjects underwent an ¹¹C‐acetate positron emission tomography. Furthermore, the CA patients underwent comprehensive echocardiography and right heart catheterization during a symptom‐limited, semi‐supine exercise test. MEE was calculated from ¹¹C‐acetate positron emission tomography as the ratio of left ventricular (LV) stroke work and the energy equivalent of MVO₂. Myocardial work efficiency was calculated as echocardiography‐derived work pressure product divided by three‐dimensional LV mass. CA patients had significantly lower LV‐ejection fraction (54±13% versus 63±4%, P<0.05) and LV‐global longitudinal strain (LVGLS) (12±4% versus 19±2%, P<0.0001) and a more restrictive filling pattern (E/e′‐ratio 18 [12–25] versus 8 [7–9], P<0.0001) than controls. MEE was severely reduced (13±5% versus 22±5%, P<0.0001) whereas total MVO₂ was higher (18±6 mL/min versus 13±3 mL/min, P<0.01) in CA patients than controls. MEE decreased with increasing New York Heart Association symptom burden (P<0.0001). We found a good relationship between MEE and peak exercise systolic performance (LVGLS: R²=0.60, P<0.0001; myocardial work efficiency: R²=0.48, P<0.0001; cardiac index: R²=0.52, P<0.0001) and between MEE and myocardial blood flow (R²=0.44, P<0.0001).

Conclusion

Myocardial oxidative metabolism is disturbed in CA patients with increased total MVO₂ and reduced MEE. MEE correlated significantly with echocardiographic derived systolic parameters such as myocardial work efficiency and LVGLS that might be used as surrogate MEE markers.

Metabolic Response to Stress by the Immature Right Ventricle Exposed to Chronic Pressure Overload

Background

The right ventricle exposed to chronic pressure overload exhibits hypertrophy and decompensates when exposed to stress. We hypothesize that impaired ability to increase myocardial oxidative flux through pyruvate dehydrogenase leads to hypertrophied right ventricular (RV) dysfunction when exposed to hemodynamic stress, and pyruvate dehydrogenase stimulation can improve RV function.

Methods and Results

Infant male Yorkshire piglets (13.5±0.6 kg weight, n=19) were used to assess substrate fractional contribution to the citric acid cycle after sustained pulmonary artery banding (PAB). Carbon 13–labeled glucose, lactate, and leucine, oxidative substrate tracers for the citric acid cycle, were infused into the right coronary artery on 7 to 10 days after PAB. RV systolic pressure, RV free wall thickness, and individual cardiomyocyte cell size after PAB were significantly elevated compared with the sham group. Both fractional glucose and lactate oxidations in the PAB group were >2‐fold higher than in the sham group. Pigs with overdrive atrial pacing (≈80% increase in heart rate) stress after PAB showed only a 22% increase in rate‐pressure product from baseline before atrial pacing and limited carbohydrate oxidation rate in the right ventricle. Intracoronary infusion of dichloroacetate, a pyruvate dehydrogenase agonist, produced higher rate‐pressure product (59% increase) in response to increased workload by atrial pacing in association with a marked increase in lactate oxidation.

Conclusions

The immature hypertrophied right ventricle shows limited ability to increase carbohydrate oxidation in response to tachycardia stress leading to energy supply/utilization imbalance and decreased systolic function. Enhanced pyruvate dehydrogenase activation by dichloroacetate increases energy supply and preserves hypertrophied RV contractile function during hemodynamic stress.

[Protective action of a modified fragment of galanine in rats with doxorubicin-induced heart failure]

The use of the anticancer drug doxorubicin (Dox) is limited due to its cardiotoxic effect. Using the method of automatic solid-phase peptide synthesis, we obtained a synthetic agonist of galanin receptors GalR1-3 [RAla14, His15]-galanine (2-15) (G), exhibiting cardioprotective properties. It was purified by high performance liquid chromatography (HPLC). The homogeneity and structure of the peptide was confirmed by HPLC, 1H-NMR spectroscopy and mass spectroscopy. The purpose of this study was to study the effect of G on the metabolism and cardiac function of rats with chronic heart failure (CHF) caused by Dox. Experiments were performed using male Wistar rats weighing 280-300 g. The control group of animals (C) was intraperitoneally treated with saline for 8 weeks; the doxorubicin group (D) of rats was intraperitoneally treated with Doх; the group of Doх + peptide G (D+G) received intraperitoneally injections of Doх and subcutaneously injections of peptide G; the peptide G group (G) was subcutaneously treated with G. At the beginning and at the end of the study, the concentration of thiobarbituric acid reactive substances (TBARS) and the activity of creatine kinase-MB (CK-MB) were determined in blood plasma; the animals were weighed, and cardiac function was assessed using echocardiography. At the end of the experiments, the hearts were used for determination of metabolites and assessment of oxidative phosphorylation in mitochondria. After 8-week treatment, animals of group D were characterized by severe heart failure, the lack of weight gain and an increase in plasma TBARS concentration and CK-MB activity. These disorders were accompanied by a decrease in the content of myocardial high-energy phosphates, a reduction inmitochondrial respiratory parameters, accumulation of lactate and glucose in the heart, and disturbances in the metabolism of alanine and glutamic and aspartic acids. Coadministration of G and Dox prevented the increase in plasma CK-MB activity and significantly reduced the plasma TBARS concentration. At the end of the experiments animals of group D+G had higher myocardial energy state and the respiratory control index of mitochondria than animals of group D, there was a decrease in anaerobic glycolysis and no changes in the amino acid content compared to the control. The peptide G significantly improved the parameters of cardiac function and caused weight gain in animals of group D+G in comparison with these parameters in group D. The obtained results demonstrate the ability of a novel agonist of galanin receptors GalR1-3 to attenuate Dox-indiced cardiotoxicity.

Effects of on-pump versus off-pump coronary artery bypass grafting on myocardial metabolism

BACKGROUND

On-pump coronary artery bypass grafting (ON-PCABG) and off-pump coronary artery bypass grafting (OF-PCABG) greatly affect myocardial metabolism (MCMB). However, no study has systematically explored and compared the impacts of ON-PCABG and OF-PCABG on MCMB. This study will aim to explore and to compare the effects of ON-PCABG and OF-PCABG on MCMB systematically.

METHODS

We will conduct the comprehensive literature search from the following electronic databases from inception to the present: Cochrane Library, EMBASE, MEDILINE, CINAHL, AMED and 4 Chinese databases without language restrictions. This systematic review will only concern randomized controlled trials (RCTs) and case-control studies of ON-PCABG and OF-PCABG on MCMB. The methodological quality of each entered study will be assessed by using Cochrane risk of bias tool.

RESULTS

Primary outcomes include myocardial cellular markers, myocardial lactate, oxygen utilization, pyruvate, and intramyocardial concentrations of glucose, urea and lactate. Secondary outcome comprises of glutathione, superoxide dismutase, myeloperoxidase, and oxidative stress and any other complications post surgery.

CONCLUSION

This study will provide a high-quality synthesis and will assess and compare the effects of ON-PCABG and OF-PCABG on MCMB based on the current relevant literature evidence.

DISSEMINATION AND ETHICS

The results will be submitted to peer-reviewed journals for publication. This study does not require ethic approval, because it only analyzes the data from published literature.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019125381.

Noninvasive evaluation of fat-carbohydrate metabolic switching in heart and contracting skeletal muscle

The ability of heart and skeletal muscle (SM) to switch between fat and carbohydrate oxidation is of high interest in the study of metabolic diseases and exercise physiology. Positron emission tomography (PET) imaging with the glucose analog 2-[¹⁸F]fluoro-2-deoxy-glucose (¹⁸F-FDG) provides a noninvasive means to quantitate glucose metabolic rates. However, evaluation of fatty acid oxidation (FAO) rates by PET has been limited by the lack of a suitable FAO probe. We have developed a metabolically trapped oleate analog, ( Z)-18-[¹⁸F]fluoro-4-thia-octadec-9-enoate (¹⁸F-FTO), and investigated the feasibility of using ¹⁸F-FTO and ¹⁸F-FDG to measure FAO and glucose uptake, respectively, in heart and SM of rats in vivo. To enhance the metabolic rates in SM, the vastus lateralis (VL) muscle was electrically stimulated in fasted rats for 30 min before and 30 min following radiotracer injection. The responses of radiotracer uptake patterns to pharmacological inhibition of FAO were assessed by pretreatment of the rats with the carnitine palmitoyl-transferase-1 (CPT-1) inhibitor sodium 2-[5-(4-chlorophenyl)-pentyl]oxirane-2-carboxylate (POCA). Small-animal PET images and biodistribution data with ¹⁸F-FTO and ¹⁸F-FDG demonstrated profound metabolic switching for energy provision in the myocardium from exogenous fatty acids to glucose in control and CPT-1-inhibited rats, respectively. Uptake of both radiotracers was low in unstimulated SM. In stimulated VL muscle, ¹⁸F-FTO and ¹⁸F-FDG uptakes were increased 4.4- and 28-fold, respectively, and CPT-1 inhibition only affected ¹⁸F-FTO uptake (66% decrease). ¹⁸F-FTO is a FAO-dependent PET probe that may allow assessment of energy substrate metabolic switching in conjunction with ¹⁸F-FDG and other metabolic probes.

Effect of prolonged fasting and low molecular weight heparin or warfarin therapies on 2-deoxy-2-[18F]-fluoro-D-glucose PET cardiac uptake

BACKGROUND

Whether anticoagulants other than unfractionated heparin are able to suppress cardiac PET uptake of 2-deoxy-2-[18F]-fluoro-D-glucose (18F-FDG) is unknown.

METHODS

One-hundred-seventy-four patients without history and clinical evidence of cardiac dysfunction and/or coronary heart disease underwent a 18F-FDG PET/CT study. All patients were studied with a >12-hours fasting and divided into 2 groups: group-1 without anticoagulant therapy (n:75); group-2 patients on low molecular weight heparin (n:60) or warfarin therapy (n:39). Cardiac 18F-FDG uptake was estimated qualitatively using a 4-point scale and semiquantitatively as total LV glycolysis (LVG) and metabolic volume (MV), drawing isocontour volume of interest (VOI) including the whole LV.

RESULTS

Qualitatively, LV 18-FDG uptake was scored 0 or 1, indicating a good suppression, in 10/75 (13%) patients of group-1 and 77/99 (78%) of group-2 (p < .001). Semiquantitatively, patients of group-1 showed higher values of 18-FDG uptake than patients of group-2, assessed as LVG (802,649 ± 468,442 vs 198,989 ± 261,439, p < .0001) or MV (219 ± 77 vs 57 ± 48 cm3, p < .0001). Subanalysis for anticoagulant drugs showed similar results.

CONCLUSIONS

Prolonged fasting combined to anticoagulants other than unfractionated heparin is able to minimize glucose cardiac metabolism. Our data confirm previous observation on the possibility to influence the metabolic pattern of the heart before the PET scan and broadens the spectrum of pharmacological options.

Metabolic Response of the Immature Right Ventricle to Acute Pressure Overloading

BACKGROUND

Surgical palliation or repair of complex congenital heart disease in early infancy can produce right ventricular (RV) pressure overload, often leading to acute hemodynamic decompensation. The mechanisms causing this acute RV dysfunction remain unclear. We tested the hypothesis that the immature right ventricle lacks the ability to modify substrate metabolism in order to meet increased energy demands induced by acute pressure overloading.

METHODS AND RESULTS

Twenty-two infant male mixed breed Yorkshire piglets were randomized to a sham operation (Control) or pulmonary artery banding yielding >2-fold elevation over baseline RV systolic pressure. We used carbon 13 (¹³C)-labeled substrates and proton nuclear magnetic resonance to assess RV energy metabolism. [Phosphocreatine]/[ATP] was significantly lower after pulmonary artery banding. [Phosphocreatine]/[ATP] inversely correlated with energy demand indexed by maximal sustained RV systolic pressure/left ventricular systolic pressure. Fractional contributions of fatty acids to citric acid cycle were significantly lower in the pulmonary artery banding group than in the Control group (medium-chain fatty acids; 14.5±1.6 versus 8.2±1.0%, long-chain fatty acids; 9.3±1.5 versus 5.1±1.1%). ¹³C-flux analysis showed that flux via pyruvate decarboxylation did not increase during RV pressure overloading.

CONCLUSIONS

Acute RV pressure overload yielded a decrease in [phosphocreatine]/[ATP] ratio, implying that ATP production did not balance the increasing ATP requirement. Relative fatty acids oxidation decreased without a reciprocal increase in pyruvate decarboxylation. The data imply that RV inability to adjust substrate oxidation contributes to energy imbalance, and potentially to contractile failure. The data suggest that interventions directed at increasing RV pyruvate decarboxylation flux could ameliorate contractile dysfunction associated with acute pressure overloading.

Metabolomic Profiling in Acute ST-Segment-Elevation Myocardial Infarction Identifies Succinate as an Early Marker of Human Ischemia-Reperfusion Injury

BACKGROUND

Ischemia-reperfusion injury following ST-segment-elevation myocardial infarction (STEMI) is a leading determinant of clinical outcome. In experimental models of myocardial ischemia, succinate accumulation leading to mitochondrial dysfunction is a major cause of ischemia-reperfusion injury; however, the potential importance and specificity of myocardial succinate accumulation in human STEMI is unknown. We sought to identify the metabolites released from the heart in patients undergoing primary percutaneous coronary intervention for emergency treatment of STEMI.

METHODS AND RESULTS

Blood samples were obtained from the coronary artery, coronary sinus, and peripheral vein in patients undergoing primary percutaneous coronary intervention for acute STEMI and in control patients undergoing nonemergency coronary angiography or percutaneous coronary intervention for stable angina or non-STEMI. Plasma metabolites were analyzed by targeted liquid chromatography and mass spectrometry. Metabolite levels for coronary artery, coronary sinus, and peripheral vein were compared to derive cardiac and systemic release ratios. In STEMI patients, cardiac magnetic resonance imaging was performed 2 days and 6 months after primary percutaneous coronary intervention to quantify acute myocardial edema and final infarct size, respectively. In total, 115 patients undergoing acute STEMI and 26 control patients were included. Succinate was the only metabolite significantly increased in coronary sinus blood compared with venous blood in STEMI patients, indicating cardiac release of succinate. STEMI patients had higher succinate concentrations in arterial, coronary sinus, and peripheral venous blood than patients with non-STEMI or stable angina. Furthermore, cardiac succinate release in STEMI correlated with the extent of acute myocardial injury, quantified by cardiac magnetic resonance imaging.

CONCLUSION

Succinate release by the myocardium correlates with the extent of ischemia.

Physical Exercise and Its Protective Effects on Diabetic Cardiomyopathy: What Is the Evidence?

As one of the most serious complications of diabetes, diabetic cardiomyopathy (DCM) imposes a huge burden on individuals and society, and represents a major public health problem. It has long been recognized that physical exercise has important health benefits for patients with type 2 diabetes, and regular physical exercise can delay or prevent the complications of diabetes. Current studies show that physical exercise has been regarded as an importantly non-pharmacological treatment for diabetes and DCM, with high efficacy and low adverse events. It can inhibit the pathological processes of myocardial apoptosis, myocardial fibrosis, and myocardial microvascular diseases through improving myocardial metabolism, enhancing the regulation of Ca²⁺, and protecting the function of mitochondria. Eventually, it can alleviate the occurrence and development of diabetic complications. Describing the mechanisms of physical exercise on DCM may provide a new theory for alleviating, or even reversing the development of DCM, and prevent it from developing to heart failure.

A Score-Based Approach to 18F-FDG PET Images as a Tool to Describe Metabolic Predictors of Myocardial Doxorubicin Susceptibility

Purpose: To verify the capability of ¹⁸F-fluorodeoxy-glucose positron emission tomography/computed tomography (FDG-PET/CT) to identify patients at higher risk of developing doxorubicin (DXR)-induced cardiotoxicity, using a score-based image approach. Methods: 36 patients underwent FDG-PET/CT. These patients had shown full remission after DXR-based chemotherapy for Hodgkin’s disease (DXR dose: 40–50 mg/m² per cycle), and were retrospectively enrolled. Inclusion criteria implied the presence of both pre- and post-chemotherapy clinical evaluation encompassing electrocardiogram (ECG) and echocardiography. Myocardial metabolism at pre-therapy PET was evaluated according to both standardized uptake value (SUV)- and score-based approaches. The capability of the score-based image assessment to predict the occurrence of cardiac toxicity with respect to SUV measurement was then evaluated. Results: In contrast to the SUV-based approach, the five-point scale method does not linearly stratify the risk of the subsequent development of cardiotoxicity. However, converting the five-points scale to a dichotomic evaluation (low vs. high myocardial metabolism), FDG-PET/CT showed high diagnostic accuracy in the prediction of cardiac toxicity (specificity = 100% and sensitivity = 83.3%). In patients showing high myocardial uptake at baseline, in which the score-based method is not able to definitively exclude the occurrence of cardiac toxicity, myocardial SUV mean quantification is able to further stratify the risk between low and intermediate risk classes. Conclusions: the score-based approach to FDG-PET/CT images is a feasible method for predicting DXR-induced cardiotoxicity. This method might improve the inter-reader and inter-scanner variability, thus allowing the evaluation of FDG-PET/CT images in a multicentral setting.

Doxorubicin Effect on Myocardial Metabolism as a Prerequisite for Subsequent Development of Cardiac Toxicity: A Translational 18F-FDG PET/CT Observation

The present translational study aimed to verify whether serial ¹⁸F-FDG PET/CT predicts doxorubicin cardiotoxicity. Methods: Fifteen athymic mice were treated intravenously with saline (n = 5) or with 5 or 7.5 mg of doxorubicin per kilogram (n = 5 each) and underwent dynamic small-animal PET beforehand and afterward to estimate left ventricular (LV) metabolic rate of glucose (MRGlu). Thereafter, we retrospectively identified 69 patients who had been successfully treated with a regimen of doxorubicin, bleomycin, vinblastine, and dacarbazine for Hodgkin disease (HD) and had undergone 4 consecutive ¹⁸F-FDG PET/CT scans. Volumes of interest were drawn on LV myocardium to quantify mean SUV. All patients were subsequently interviewed by telephone (median follow-up, 30 mo); 36 of them agreed to undergo electrocardiography and transthoracic echocardiography. Results: In mice, LV MRGlu was 17.9 ± 4.4 nmol × min^-1 × g^-1 at baseline. Doxorubicin selectively and dose-dependently increased this value in the standard-dose (27.9 ± 9 nmol × min^-1 × g^-1, P < 0.05 vs. controls) and high-dose subgroups (37.2 ± 7.8 nmol × min^-1 × g^-1, P < 0.01 vs. controls, P < 0.05 vs. standard-dose). In HD patients, LV SUV showed a progressive increase during doxorubicin treatment that persisted at follow-up. New-onset cardiac abnormalities appeared in 11 of 36 patients (31%). In these subjects, pretherapy LV SUV was markedly lower with respect to the remaining patients (1.53 ± 0.9 vs. 3.34 ± 2.54, respectively, P < 0.01). Multivariate analysis confirmed the predictive value of baseline LV SUV for subsequent cardiac abnormalities. Conclusion: Doxorubicin dose-dependently increases LV MRGlu, particularly in the presence of low baseline ¹⁸F-FDG uptake. These results imply that low myocardial ¹⁸F-FDG uptake before the initiation of doxorubicin chemotherapy in HD patients may predict the development of chemotherapy-induced cardiotoxicity, suggesting that prospective clinical trials are warranted to test this hypothesis.

Does young age really put the heart at risk?

Despite significant advances in the management and treatment of heart disease in children, there continue to be patients who have worse outcomes than might be expected. A number of risk factors that could be responsible have been identified. Evidence-based findings will be reviewed, including whether young age and (or) reduced body weight exacerbate these responses. For example, newborn children undergoing congenital cardiac surgery are known to have worse outcomes than older children. Evidence exists that newborn hearts do not tolerate ischemia as well as adult hearts, developing irreversible injury sooner and exhibiting at-risk metabolic profiles. As well, in response to the administration of heparin, elevations in free fatty acids occur during congenital heart surgery in children, which can have detrimental effects on the heart. Furthermore, myocardial energetic state has also been suggested to impact outcomes. Unfavourable energetic profiles were correlated to lower body weights in the same age healthy newborn piglet model. Newborn children suffering from congenital heart disease, with lower body weights, also had lower myocardial energetic state and this correlated with longer postoperative ventilatory support as well as a trend to longer intensive care unit stay. These findings imply that unfavourable myocardial metabolic profiles could contribute to postoperative complications.

Myocardial Oxygen Consumption and Efficiency in Aortic Valve Stenosis Patients With and Without Heart Failure

Background

Myocardial oxygen consumption (MVO₂) and its coupling to contractile work are fundamentals of cardiac function and may be involved causally in the transition from compensated left ventricular hypertrophy to failure. Nevertheless, these processes have not been studied previously in patients with aortic valve stenosis (AS).

Methods and Results

Participants underwent ¹¹C‐acetate positron emission tomography, cardiovascular magnetic resonance, and echocardiography to measure MVO₂ and myocardial external efficiency (MEE) defined as the ratio of left ventricular stroke work and the energy equivalent of MVO₂. We studied 10 healthy controls (group A), 37 asymptomatic AS patients with left ventricular ejection fraction ≥50% (group B), 12 symptomatic AS patients with left ventricular ejection fraction ≥50% (group C), and 9 symptomatic AS patients with left ventricular ejection fraction <50% (group D). MVO₂ did not differ among groups A, B, C, and D (0.105±0.02, 0.117±0.024, 0.129±0.032, and 0.104±0.026 mL/min per gram, respectively; P=0.07), whereas MEE was reduced in group D (21.0±1.6%, 22.3±3.3%, 22.1±4.2%, and 17.3±4.7%, respectively; P<0.05). Similarly, patients with global longitudinal strain greater than −12% and paradoxical low‐flow, low‐gradient AS had impaired MEE (P<0.05 versus controls). The ability to discriminate between symptomatic and asymptomatic patients was superior for global longitudinal strain compared with MVO₂ and MEE (area under the curve 0.98, 0.48, and 0.61, respectively; P<0.05).

Conclusions

AS patients display a persistent ability to maintain normal MVO₂ and MEE (ie, the ability to convert energy into stroke work); however, patients with left ventricular ejection fraction <50%; global longitudinal strain greater than −12%; or paradoxical low‐flow, low‐gradient AS demonstrate reduced MEE. These findings suggest that mitochondrial uncoupling contributes to the dismal prognosis in patients with reduced contractile function or paradoxical low‐flow, low‐gradient AS.

Deranged Cardiac Metabolism and the Pathogenesis of Heart Failure

Activation of the neuro-hormonal system is a pathophysiological consequence of heart failure. Neuro-hormonal activation promotes metabolic changes, such as insulin resistance, and determines an increased use of non-carbohydrate substrates for energy production. Fasting blood ketone bodies as well as fat oxidation are increased in patients with heart failure, yielding a state of metabolic inefficiency. The net result is additional depletion of myocardial adenosine triphosphate, phosphocreatine and creatine kinase levels with further decreased efficiency of mechanical work. In this context, manipulation of cardiac energy metabolism by modification of substrate use by the failing heart has produced positive clinical results. The results of current research support the concept that shifting the energy substrate preference away from fatty acid metabolism and towards glucose metabolism could be an effective adjunctive treatment in patients with heart failure. The additional use of drugs able to partially inhibit fatty acids oxidation in patients with heart failure may therefore yield a significant protective effect for clinical symptoms and cardiac function improvement, and simultaneously ameliorate left ventricular remodelling. Certainly, to clarify the exact therapeutic role of metabolic therapy in heart failure, a large multicentre, randomised controlled trial should be performed.

Myosin Activator Omecamtiv Mecarbil Increases Myocardial Oxygen Consumption and Impairs Cardiac Efficiency Mediated by Resting Myosin ATPase Activity

BACKGROUND

Omecamtiv mecarbil (OM) is a novel inotropic agent that prolongs systolic ejection time and increases ejection fraction through myosin ATPase activation. We hypothesized that a potentially favorable energetic effect of unloading the left ventricle, and thus reduction of wall stress, could be counteracted by the prolonged contraction time and ATP-consumption.

METHODS AND RESULTS

Postischemic left ventricular dysfunction was created by repetitive left coronary occlusions in 7 pigs (7 healthy pigs also included). In both groups, systolic ejection time and ejection fraction increased after OM (0.75 mg/kg loading for 10 minutes, followed by 0.5 mg/kg/min continuous infusion). Cardiac efficiency was assessed by relating myocardial oxygen consumption to the cardiac work indices, stroke work, and pressure-volume area. To circumvent potential neurohumoral reflexes, cardiac efficiency was additionally assessed in ex vivo mouse hearts and isolated myocardial mitochondria. OM impaired cardiac efficiency; there was a 31% and 23% increase in unloaded myocardial oxygen consumption in healthy and postischemic pigs, respectively. Also, the oxygen cost of the contractile function was increased by 63% and 46% in healthy and postischemic pigs, respectively. The increased unloaded myocardial oxygen consumption was confirmed in OM-treated mouse hearts and explained by an increased basal metabolic rate. Adding the myosin ATPase inhibitor, 2,3-butanedione monoxide abolished all surplus myocardial oxygen consumption in the OM-treated hearts.

CONCLUSIONS

Omecamtiv mecarbil, in a clinically relevant model, led to a significant myocardial oxygen wastage related to both the contractile and noncontractile function. This was mediated by that OM induces a continuous activation in resting myosin ATPase.

Improvement in cardiac energetics by perhexiline in heart failure due to dilated cardiomyopathy

OBJECTIVES

The aim of this study was to determine whether short-term treatment with perhexiline improves cardiac energetics, left ventricular function, and symptoms of heart failure by altering cardiac substrate utilization.

BACKGROUND

Perhexiline improves exercise capacity and left ventricular ejection fraction (LVEF) in patients with heart failure (HF). (31)P cardiac magnetic resonance spectroscopy can be used to quantify the myocardial phosphocreatine/adenosine triphosphate ratio. Because improvement of HF syndrome can improve cardiac energetics secondarily, we investigated the effects of short-term perhexiline therapy.

METHODS

Patients with systolic HF of nonischemic etiology (n = 50, 62 ± 1.8 years of age, New York Heart Association functional class II to IV, LVEF: 27.0 ± 1.44%) were randomized to receive perhexiline 200 mg or placebo for 1 month in a double-blind fashion. Clinical assessment, echocardiography, and (31)P cardiac magnetic resonance spectroscopy were performed at baseline and after 1 month. A substudy of 22 patients also underwent cross-heart blood sampling at completion of the study to quantify metabolite utilization.

RESULTS

Perhexiline therapy was associated with a 30% increase in the phosphocreatine/adenosine triphosphate ratio (from 1.16 ± 0.39 to 1.51 ± 0.51; p < 0.001) versus a 3% decrease with placebo (from 1.36 ± 0.31 to 1.34 ± 0.31; p = 0.37). Perhexiline therapy also led to an improvement in New York Heart Association functional class compared with placebo (p = 0.036). Short-term perhexiline therapy did not change LVEF. Cross-heart measures of cardiac substrate uptake and respiratory exchange ratio (which reflects the ratio of substrates used) did not differ between patients who received perhexiline versus placebo.

CONCLUSIONS

Perhexiline improves cardiac energetics and symptom status with no evidence of altered cardiac substrate utilization. No change in LVEF is seen at this early stage. (Metabolic Manipulation in Chronic Heart Failure; NCT00841139).

Triiodothyronine activates lactate oxidation without impairing fatty acid oxidation and improves weaning from extracorporeal membrane oxygenation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) provides a rescue for children with severe cardiac failure. It has previously been shown that triiodothyronine (T3) improves cardiac function by modulating pyruvate oxidation during weaning. This study focused on fatty acid (FA) metabolism modulated by T3 for weaning from ECMO after cardiac injury. METHODS AND RESULTS: Nineteen immature piglets (9.1-15.3 kg) were separated into 3 groups with ECMO (6.5 h) and wean: normal circulation (Group-C); transient coronary occlusion (10 min) for ischemia-reperfusion (IR) followed by ECMO (Group-IR); and IR with T3 supplementation (Group-IR-T3). 13-Carbon ((13)C)-labeled lactate, medium-chain and long-chain FAs, was infused as oxidative substrates. Substrate fractional contribution (FC) to the citric acid cycle was analyzed by(13)C-nuclear magnetic resonance. ECMO depressed circulating T3 levels to 40% of the baseline at 4 h and were restored in Group-IR-T3. Group-IR decreased cardiac power, which was not fully restorable and 2 pigs were lost because of weaning failure. Group-IR also depressed FC-lactate, while the excellent contractile function and energy efficiency in Group-IR-T3 occurred along with a marked FC-lactate increase and [adenosine triphosphate]/[adenosine diphosphate] without either decreasing FC-FAs or elevating myocardial oxygen consumption over Group-C or -IR.

CONCLUSIONS

T3 releases inhibition of lactate oxidation following IR injury without impairing FA oxidation. These findings indicate that T3 depression during ECMO is maladaptive, and that restoring levels improves metabolic flux and enhances contractile function during weaning.

In vivo proton T1 relaxation times of mouse myocardial metabolites at 9.4 T

PURPOSE

Proton magnetic resonance spectroscopy ((1) H-MRS) for quantitative in vivo assessment of mouse myocardial metabolism requires accurate acquisition timing to minimize motion artifacts and corrections for T1 -dependent partial saturation effects. In this study, mouse myocardial water and metabolite T1 relaxation time constants were quantified.

METHODS

Cardiac-triggered and respiratory-gated PRESS-localized (1) H-MRS was employed at 9.4 T to acquire signal from a 4-µL voxel in the septum of healthy mice (n = 10) while maintaining a steady state of magnetization using dummy scans during respiratory gates. Signal stability was assessed via standard deviations (SD) of zero-order phases and amplitudes of water spectra. Saturation-recovery experiments were performed to determine T1 values.

RESULTS

Phase SD did not vary for different repetition times (TR), and was 13.1° ± 4.5°. Maximal amplitude SD was 14.2% ± 5.1% at TR = 500 ms. Myocardial T1 values (mean ± SD) were quantified for water (1.71 ± 0.25 s), taurine (2.18 ± 0.62 s), trimethylamine from choline-containing compounds and carnitine (1.67 ± 0.25 s), creatine-methyl (1.34 ± 0.19 s), triglyceride-methylene (0.60 ± 0.15 s), and triglyceride-methyl (0.90 ± 0.17 s) protons.

CONCLUSION

This work provides in vivo quantifications of proton T1 values for mouse myocardial water and metabolites at 9.4 T.

Impact of sex on the heart's metabolic and functional responses to diabetic therapies

Increased myocardial lipid delivery is a determinant of myocardial substrate metabolism and function in animal models of type 2 diabetes (T2DM). Sex also has major effects on myocardial metabolism in the human heart. Our aims were to determine whether 1) sex affects the myocardial metabolic response to lipid lowering in T2DM, 2) altering lipid [fatty acid (FA) or triglyceride] delivery to the heart would lower the elevated myocardial lipid metabolism associated with T2DM, and 3) decreasing lipid delivery improves diastolic dysfunction in T2DM. To this end, we studied 78 T2DM patients (43 women) with positron emission tomography, echocardiography, and whole body tracer studies before and 3 mo after randomization to metformin (MET), metformin + rosiglitazone (ROSI), or metformin + Lovaza (LOV). No treatment main effects were found for myocardial substrate metabolism, partly because men and women often had different responses to a given treatment. In men, MET decreased FA clearance, which was linked to increased plasma FA levels, myocardial FA utilization and oxidation, and lower myocardial glucose utilization. In women, ROSI increased FA clearance, thereby decreasing plasma FA levels and myocardial FA utilization. Although LOV did not change triglyceride levels, it improved diastolic function, particularly in men. Group and sex also interacted in determining myocardial glucose uptake. Thus, in T2DM, different therapeutic regimens impact myocardial metabolism and diastolic function in a sex-specific manner. This suggests that sex should be taken into account when designing a patient's diabetes treatment.

Decreased long-chain fatty acid oxidation impairs postischemic recovery of the insulin-resistant rat heart

Diabetic patients with acute myocardial infarction are more likely to die than nondiabetic patients. In the present study we examined the effect of insulin resistance on myocardial ischemia tolerance. Hearts of rats, rendered insulin resistant by high-sucrose feeding, were subjected to ischemia/reperfusion ex vivo. Cardiac power of control hearts from chow-fed rats recovered to 93%, while insulin-resistant hearts recovered only to 80% (P<0.001 vs. control). Unexpectedly, impaired contractile recovery did not result from an impairment of glucose oxidation (576±36 vs. 593±42 nmol/min/g dry weight; not significant), but from a failure to increase and to sustain oxidation of the long-chain fatty acid oleate on reperfusion (1878±56 vs. 2070±67 nmol/min/g dry weight; P<0.05). This phenomenon was due to a reduced ability to transport oleate into mitochondria and associated with a 38-58% decrease in the mitochondrial uncoupling protein 3 (UCP3) levels. Contractile function was rescued by replacing oleate with a medium-chain fatty acid or by restoring UCP3 levels with 24 h of food withdrawal. Lastly, the knockdown of UCP3 in rat L6 myocytes also decreased oleate oxidation by 13-18% following ischemia. Together the results expose UCP3 as a critical regulator of long-chain fatty acid oxidation in the stressed heart postischemia and identify octanoate as an intervention by which myocardial metabolism can be manipulated to improve function of the insulin-resistant heart.

Assessing mitochondrial respiration in isolated hearts using (17)O MRS

The application of (17)O MRI and MRS for the evaluation of cardiac mitochondrial function has been limited because of the challenge of detecting metabolic H(2)(17)O in the vast background of naturally abundant H(2)(17)O. In this study, we have developed a direct (17)O MRS approach to examine the feasibility and sensitivity of detecting metabolically produced H(2)(17)O in isolated rat hearts perfused with (17)O(2)-enriched Krebs-Henseleit buffer containing normal (1.5 mm) and high (2.5 mm) calcium (Ca(2+)) concentrations to induce high workload. Consistent with increased workload at high Ca(2+) concentration, the measured myocardial oxygen consumption rate (MVO(2)) increased by 82%. Dynamic (17)O MRS showed an accelerated increase in the H(2)(17)O signal at high Ca(2+) concentration, suggesting increased mitochondrial production of H(2)(17)O in concordance with the increased workload. A compartment model was developed to describe the kinetics of H(2)(17)O production as a function of MVO(2). The myocardial (17)O(2) consumption rate (MV(17)O(2) was determined by least-squares fitting of the model to the NMR-measured H(2)(17)O concentration. Consistent with the measured MVO(2), the model-determined MV(17)O(2) showed a 92% increase at high Ca(2+) concentration. The increase in metabolic activity at high workload allowed the balance between ATP production and utilization to be maintained, leading to a similar phosphocreatine to ATP ratio. These results demonstrate that dynamic (17)O MRS can provide a valuable tool for the detection of an altered metabolic rate associated with a change in cardiac workload.

Peroxisome proliferator activated receptor-alpha (PPARα) and PPAR gamma coactivator-1alpha (PGC-1α) regulation of cardiac metabolism in diabetes

Cardiovascular disease is a leading cause of mortality among patients with diabetes, and heart failure exists even in the absence of coronary disease. Myocardial metabolism is altered in the diabetic heart as a result of changes in substrate availability secondary to insulin resistance. The nuclear receptor peroxisome proliferator activated receptor-alpha (PPARα) and PPAR-gamma coactivator-1alpha (PGC-1α) play important roles in transcriptional regulation of myocardial metabolism and contribute significantly to the changes that occur in the diabetic heart. This review summarizes the role of PPARα and PGC-1α in myocardial metabolism in the normal heart and in the diabetic heart.

Transcapillary adenosine transport and interstitial adenosine concentration in guinea pig hearts

We used the multiple-indicator-dilution technique to observe the capillary transport of adenosine in isolated Krebs-Henseleit-perfused guinea pig hearts. Tracer concentrations of radiolabeled albumin, sucrose, and adenosine were injected into the coronary inflow; outflow samples were collected for 10-25 s and analyzed by high-performance liquid chromatography (HPLC) and by gamma- and beta-counting. The albumin data define the intravascular transport characteristics; the sucrose data define permeation through interendothelial clefts and dilution in interstitial fluid (ISF). Parameters calculated from adenosine data include permeability-surface area products for endothelial cell uptake at the luminal and abluminal membranes and intraendothelial metabolism. We found that in situ endothelial cells avidly take up and metabolize adenosine. Tracer adenosine in the capillary lumen is twice as likely to enter an endothelial cell as it is to permeate the clefts. There was no adenosine in the arterial perfusate. Under control conditions, the steady-state venous adenosine concentration was 3.6 +/- 0.8 nM, which from the flow and the parameters estimated from the tracer data gave a calculated ISF concentration of 6.8 +/- 1.5 nM. During dipyridamole infusion (10 microM) at constant pressure, the cell permeabilities went essentially to zero, whereas the venous adenosine concentration increased to 44.0 +/- 12.6 nM, giving an estimated ISF concentration of 191 +/- 53 nM. With constant flow perfusion, venous concentration during dipyridamole infusion was 30.9 +/- 6.3 nM, and estimated ISF concentration was 88 +/- 20 mM. We conclude that in this preparation, at rest, the ISF adenosine concentration is about twice the venous concentration and the ISF adenosine concentration increases with dipyridamole administration.

Temporal fluctuations in regional myocardial flows

Considerable spatial heterogeneity has been observed in regional myocardial blood flow in isolated hearts and in both anesthetized and conscious animals. In order to study how local blood flow varies with time, the data obtained by King et al. (1985) from ten awake, healthy baboons were analyzed to estimate the role of temporal fluctuations. Four to six distributions of regional flows were estimated at intervals of 4 min to 27 h, using 15 mu diameter microspheres and dividing each heart into 204 locatable pieces (average piece mass = 0.17 g). The technique averages over the 40 s of the injection giving no measure of fluctuations over a few seconds. The temporal variation in regional blood flow, expressed as the relative dispersion (SD/mean) of the temporally separated measurements about the mean flow for each piece and corrected for methodological noise, was 12% for the whole heart (10828 observations). For the left ventricle, the temporal variation was 10% (8806 observations), for the right ventricle 14% (1455 observations), and for the atria 22% (567 observations). On a relative basis, temporal fluctuation was greatest in regions having low flows. Since the magnitude of the changes in flow distributions was the same after 4 min as it was in several hours, we conclude that much of the "twinkling" is a high frequency phenomenon occurring over seconds to a few minutes. Further, it is concluded that regional myocardial blood flow in conscious primates is relatively stable with time, temporal fluctuations causing only about one third of the variation between regions.

Effects of nicardipine on coronary blood flow, left ventricular inotropic state and myocardial metabolism in patients with angina pectoris

The effects of intravenous nicardipine (2.5 mg) on the left ventricular (LV) inotropic state, LV metabolism, and coronary haemodynamics were analysed in 22 patients with angina pectoris. Measurements were made at fixed heart rate (atrial pacing), under basal state, and during a cold pressor test. After nicardipine, coronary blood flow and oxygen content in the coronary sinus increased significantly. The indices of inotropic state increased slightly, and the rate of isovolumic LV pressure fall improved. Myocardial oxygen consumption was unchanged despite the significant reduction in pressure-rate product, but LV lactate uptake increased, particularly during the cold pressor test. When nicardipine was administered after propranolol, the indices of inotropic state were unaffected. The lack of direct effect of nicardipine on LV inotropic state was further confirmed by intracoronary injection of 0.1 and 0.2 mg in a separate group of 10 patients. It is concluded that the nicardipine-induced coronary dilatation seems to improve perfusion and aerobic metabolism in areas with chronic ischaemia, resulting in reduced lactate production and augmented oxygen consumption.