Utility of wearable physical activity monitors in cardiovascular disease: a systematic review of 11 464 patients and recommendations for optimal use

Aims

Physical activity (PA) plays an important role in primary and secondary prevention of cardiovascular disease (CVD), functioning as a marker of disease progression and response to therapy. Real-world measurement of habitual PA is now possible through wearable activity monitors, however, their use in cardiovascular patients is not well described.

Methods and results

We performed a systematic review to summarize how wearable activity monitors have been used to measure PA in patients with CVD, with 11 464 patients included across 108 studies. Activity monitors were primarily used in the setting of cardiac rehabilitation (46, 43%). Most often, triaxial accelerometers (70, 65%) were instructed to be worn at the hip (58, 54%) for 7 days (n = 54, 50%). Thirty-nine different activity monitors were used, with a range of accelerometer specific settings for collection and reporting of activity data. Activity was reported most commonly as time spent in metabolic equivalent-defined activity levels (49, 45%), while non-wear time was defined in just 16 (15%) studies.

Conclusion

The collecting, processing, and reporting of accelerometer-related outcomes were highly heterogeneous. Most validation studies are limited to healthy young adults, while the paucity of methodological information disclosed renders interpretation of results and cross-study comparison challenging. While accelerometers are promising tools to measure real-world PA, we highlight current challenges facing their use in elderly multimorbid cardiology patients. We suggest recommendations to guide investigators using these devices in cardiovascular research. Future work is required to determine optimal methodology and consensus-based development of meaningful outcomes using raw acceleration data.

Cardiac myosin-binding protein C in the diagnosis and risk stratification of acute heart failure

AIMS

Cardiac myosin-binding protein C (cMyC) seems to be even more sensitive in the quantification of cardiomyocyte injury vs. high-sensitivity cardiac troponin, and may therefore have diagnostic and prognostic utility.

METHODS AND RESULTS

In a prospective multicentre diagnostic study, cMyC, high-sensitivity cardiac troponin T (hs-cTnT), and N-terminal pro-B-type natriuretic peptide (NT-proBNP) plasma concentrations were measured in blinded fashion in patients presenting to the emergency department with acute dyspnoea. Two independent cardiologists centrally adjudicated the final diagnosis. Diagnostic accuracy for acute heart failure (AHF) was quantified by the area under the receiver operating characteristic curve (AUC). All-cause mortality within 360 days was the prognostic endpoint. Among 1083 patients eligible for diagnostic analysis, 51% had AHF. cMyC concentrations at presentation were higher among AHF patients vs. patients with other final diagnoses [72 (interquartile range, IQR 39-156) vs. 22 ng/L (IQR 12-42), P < 0.001)]. cMyC's AUC was high [0.81, 95% confidence interval (CI) 0.78-0.83], higher than hs-cTnT's (0.79, 95% CI 0.76-0.82, P = 0.081) and lower than NT-proBNP's (0.91, 95% CI 0.89-0.93, P < 0.001). Among 794 AHF patients eligible for prognostic analysis, 28% died within 360 days; cMyC plasma concentrations above the median indicated increased risk of death (hazard ratio 2.19, 95% CI 1.66-2.89; P < 0.001). cMyC's prognostic accuracy was comparable with NT-proBNP's and hs-cTnT's. cMyC did not independently predict all-cause mortality when used in validated multivariable regression models. In novel multivariable regression models including medication, age, left ventricular ejection fraction, and discharge creatinine, cMyC remained an independent predictor of death and had no interactions with medical therapies at discharge.

CONCLUSION

Cardiac myosin-binding protein C may aid physicians in the rapid triage of patients with suspected AHF.

Cardiac troponin and defining myocardial infarction

The 4th Universal Definition of Myocardial Infarction has stimulated considerable debate since its publication in 2018. The intention was to define the types of myocardial injury through the lens of their underpinning pathophysiology. In this review, we discuss how the 4th Universal Definition of Myocardial Infarction defines infarction and injury and the necessary pragmatic adjustments that appear in clinical guidelines to maximize triage of real-world patients.

Baseline NT-proBNP Accurately Predicts Symptom Response to Transcatheter Aortic Valve Implantation

Background

Up to 30% of patients undergoing transcatheter aortic valve implantation (TAVI) experience minimal symptomatic benefit or die within 1 year, indicating an urgent need for enhanced patient selection. Previous analyses of baseline NT‐proBNP (N‐terminal pro‐brain natriuretic peptide) and TAVI outcomes have assumed a linear relationship, yielding conflicting results. We reexamined the relationship between baseline NT‐proBNP and symptomatic improvement after TAVI.

Methods and Results

Symptom status, clinical and echocardiographic data, and baseline NT‐proBNP were reviewed from 144 consecutive patients undergoing TAVI for severe symptomatic aortic stenosis. The primary end point was change in New York Heart Association functional class at 1 year. There was a nonlinear, inverted‐U relationship between log‐baseline NT‐proBNP and post‐TAVI change in NYHA class (R²=0.4559). NT‐proBNP thresholds of <800 and >10 000 ng/L accurately predicted no symptomatic improvement at 1 year (sensitivity 88%, specificity 83%, positive predictive value 72%, negative predictive value 93%). In adjusted analyses, baseline NT‐proBNP outside this “sweet‐spot” range was the only factor independently associated with poor functional outcome (high: NT‐proBNP >10 000 ng/L, odds ratio [OR], 65; 95% CI, 6–664; low: NT‐proBNP <800 ng/L, OR, 73; 95% CI, 7–738).

Conclusions

Baseline NT‐proBNP is a useful prognostic marker to predict poor symptom relief after TAVI and may indicate when intervention is likely to be futile. Both low (<800 ng/L) and very high (>10 000 ng/L) levels are strongly associated with poor functional outcome, suggesting an alternative cause for symptoms in the former scenario and an irrevocably diseased left ventricle in the latter. Further evaluation of this relationship is warranted.

Improving translational research in sex-specific effects of comorbidities and risk factors in ischaemic heart disease and cardioprotection: position paper and recommendations of the ESC Working Group on Cellular Biology of the Heart

Ischaemic heart disease (IHD) is a complex disorder and a leading cause of death and morbidity in both men and women. Sex, however, affects several aspects of IHD, including pathophysiology, incidence, clinical presentation, diagnosis as well as treatment and outcome. Several diseases or risk factors frequently associated with IHD can modify cellular signalling cascades, thus affecting ischaemia/reperfusion injury as well as responses to cardioprotective interventions. Importantly, the prevalence and impact of risk factors and several comorbidities differ between males and females, and their effects on IHD development and prognosis might differ according to sex. The cellular and molecular mechanisms underlying these differences are still poorly understood, and their identification might have important translational implications in the prediction or prevention of risk of IHD in men and women. Despite this, most experimental studies on IHD are still undertaken in animal models in the absence of risk factors and comorbidities, and assessment of potential sex-specific differences are largely missing. This ESC WG Position Paper will discuss: (i) the importance of sex as a biological variable in cardiovascular research, (ii) major biological mechanisms underlying sex-related differences relevant to IHD risk factors and comorbidities, (iii) prospects and pitfalls of preclinical models to investigate these associations, and finally (iv) will provide recommendations to guide future research. Although gender differences also affect IHD risk in the clinical setting, they will not be discussed in detail here.

Cardiac Myosin-Binding Protein C-From Bench to Improved Diagnosis of Acute Myocardial Infarction

Chest pain is responsible for 6-10% of all presentations to acute healthcare providers. Triage is inherently difficult and heavily reliant on the quantification of cardiac Troponin (cTn), as a minority of patients with an ultimate diagnosis of acute myocardial infarction (AMI) present with clear diagnostic features such as ST-elevation on the electrocardiogram. Owing to slow release and disappearance of cTn, many patients require repeat blood testing or present with stable but elevated concentrations of the best available biomarker and are thus caught at the interplay of sensitivity and specificity.We identified cardiac myosin-binding protein C (cMyC) in coronary venous effluent and developed a high-sensitivity assay by producing an array of monoclonal antibodies and choosing an ideal pair based on affinity and epitope maps. Compared to high-sensitivity cardiac Troponin (hs-cTn), we demonstrated that cMyC appears earlier and rises faster following myocardial necrosis. In this review, we discuss discovery and structure of cMyC, as well as the migration from a comparably insensitive to a high-sensitivity assay facilitating first clinical studies. This assay was subsequently used to describe relative abundance of the protein, compare sensitivity to two high-sensitivity cTn assays and test diagnostic performance in over 1900 patients presenting with chest pain and suspected AMI. A standout feature was cMyC's ability to more effectively triage patients. This distinction is likely related to the documented greater abundance and more rapid release profile, which could significantly improve the early triage of patients with suspected AMI.

Secondary mitral regurgitation: pathophysiology, proportionality and prognosis

Secondary mitral regurgitation (SMR) occurs as a result of multifactorial left atrioventricular dysfunction and maleficent remodelling. It is the most common and undertreated form of mitral regurgitation (MR) and is associated with a very poor prognosis. Whether SMR is a bystander reflecting the severity of the cardiomyopathy disease process has long been the subject of debate. Studies suggest that SMR is an independent driver of prognosis in patients with an intermediate heart failure (HF) phenotype and not those with advanced HF. There is also no universal agreement regarding the quantitative thresholds defining severe SMR and indeed there are challenges with echocardiographic quantification. Until recently, no surgical or transcatheter intervention for SMR had demonstrated prognostic benefit, in contrast with HF medical therapy and cardiac resynchronisation therapy. In 2018, the first two randomised controlled trials (RCTs) of edge-to-edge transcatheter mitral valve repair versus guideline-directed medical therapy in HF (Percutaneous Repair with the MitraClip Device for Severe (MITRA-FR), Transcather mitral valve repair in patients with heart failure (COAPT)) reported contrasting yet complimentary results. Unlike in MITRA-FR, COAPT demonstrated significant prognostic benefit, largely attributed to the selection of patients with disproportionately severe MR relative to their HF phenotype. Consequently, quantifying the degree of SMR in relation to left ventricular volume may be a useful discriminator in predicting the success of transcatheter intervention. The challenge going forward is the identification and validation of such parameters while in parallel maintaining a heart-team guided holistic approach.

Coronary Microvascular Dysfunction Is Associated With Myocardial Ischemia and Abnormal Coronary Perfusion During Exercise

BACKGROUND

Coronary microvascular dysfunction (MVD) is defined by impaired flow augmentation in response to a pharmacological vasodilator in the presence of nonobstructive coronary artery disease. It is unknown whether diminished coronary vasodilator response correlates with abnormal exercise physiology or inducible myocardial ischemia.

METHODS

Patients with angina and nonobstructive coronary artery disease had simultaneous coronary pressure and flow velocity measured using a dual sensor-tipped guidewire during rest, supine bicycle exercise, and adenosine-mediated hyperemia. Microvascular resistance (MR) was calculated as coronary pressure divided by flow velocity. Wave intensity analysis quantified the proportion of accelerating wave energy (perfusion efficiency). Global myocardial blood flow and subendocardial:subepicardial perfusion ratio were quantified using 3-Tesla cardiac magnetic resonance imaging during hyperemia and rest; inducible ischemia was defined as hyperemic subendocardial:subepicardial perfusion ratio <1.0. Patients were classified as having MVD if coronary flow reserve <2.5 and controls if coronary flow reserve ≥2.5, with researchers blinded to the classification.

RESULTS

Eighty-five patients were enrolled (78% female, 57±10 years), 45 (53%) were classified as having MVD. Of the MVD group, 82% had inducible ischemia compared with 22% of controls (P<0.001); global myocardial perfusion reserve was 2.01±0.41 and 2.68±0.49 (P<0.001). In controls, coronary perfusion efficiency improved from rest to exercise and was unchanged during hyperemia (59±11% vs 65±14% vs 57±18%; P=0.02 and P=0.14). In contrast, perfusion efficiency decreased during both forms of stress in MVD (61±12 vs 44±10 vs 42±11%; both P<0.001). Among patients with a coronary flow reserve <2.5, 62% had functional MVD, with normal minimal MR (hyperemic MR<2.5 mmHg/cm/s), and 38% had structural MVD with elevated hyperemic MR. Resting MR was lower in those with functional MVD (4.2±1.0 mmHg/cm/s) than in those with structural MVD (6.9±1.7 mmHg/cm/s) or controls (7.3±2.2 mmHg/cm/s; both P<0.001). During exercise, the structural group had a higher systolic blood pressure (188±25 mmHg) than did those with functional MVD (161±27 mmHg; P=0.004) and controls (156±30 mmHg; P<0.001). Functional and structural MVD had similar stress myocardial perfusion and exercise perfusion efficiency values.

CONCLUSION

In patients with angina and nonobstructive coronary artery disease, diminished coronary flow reserve characterizes a cohort with inducible ischemia and a maladaptive physiological response to exercise. We have identified 2 endotypes of MVD with distinctive systemic vascular responses to exercise; whether endotypes have a different prognosis or require different treatments merits further investigation.

P792Cardiac myosin-binding protein C for the diagnosis and long-term prognosis of acute heart failure

Background

Cardiac myosin-binding protein C (cMyC) is a novel biomarker quantifying cardiac injury. Its utility for the diagnosis, prognosis, and therapy guidance in acute heart failure (AHF) is unclear.

Methods

In a prospective diagnostic multicentre study, unselected patients presenting with acute dyspnoea to the emergency department were enrolled. cMyC, high-sensitive cardiac troponin T (hs-cTnT), and N-terminal pro-B-type natriuretic peptide (NT-proBNP) plasma concentrations were measured. Two independent cardiologists/internists centrally adjudicated the final diagnosis using all individual patient's information. Co-primary outcome measures were cMyC's: diagnostic safety and efficacy; prognostic accuracy.

Results

Among 1,330 recruited patients, 247 from an AHF substudy were not included in the diagnostic analysis. Accordingly, 548 patients (51%) in this analysis had an adjudicated diagnosis of AHF. For the rapid rule-out of AHF, the cMyC cut-off concentration at 16 ng/L achieved a sensitivity of 95% (95% CI, 93–97%), a negative predictive value of 88% (95% CI, 84–92%), and allowed to rule-out 21% of the patients. Correspondingly, cMyC's efficacy and safety in the triage of AHF were slightly lower than NT-proBNP's. Of the 790 AHF patients in the prognostic analysis, 222 (28%) died during the 360 days' follow-up. Patients with cMyC plasma concentrations above the median had significantly shorter mean time to death (274 versus 320 days, p=0.001). Compared to hs-cTnT and discharge NT-proBNP, cMyC showed non-inferior prognostic accuracy. No significant interactions between cMyC and cardiac medical therapies at discharge in predicting 360 days survival were present.

Conclusion

cMyC performs well in the rapid triage and prognosis of AHF.

Acknowledgement/Funding

European Union, Swiss National Science Foundation, Swiss Heart Foundation, Cardiovascular Research Foundation Basel, University Hospital of Basel

2380Mechanisms of myocardial ischemia during exercise in microvascular angina

Background

Coronary microvascular dysfunction (MVD) is defined by impaired flow augmentation in response to a vasodilator, the pathophysiological basis of which is unclear. This study sought to address two major gaps in our understanding of MVD: firstly, whether diminished flow reserve is due to structural changes within the microvasculature or potentially reversible dysfunction and secondly to unravel the mechanism of exercise-induced ischemia in the absence of obstructive disease.

Methods

Simultaneous intracoronary pressure and flow velocity recordings were made in the left anterior descending artery of patients with angina and no obstructive epicardial disease (Fractional Flow Reserve >0.80). Measurements were made at rest, during adenosine-mediated hyperaemia and supine bicycle exercise. Wave intensity analysis was used to quantify waves that accelerate and decelerate coronary blood flow, coronary perfusion efficiency being defined as the proportion of total wave energy that accelerates blood flow. Patients were prospectively classified into MVD (coronary flow reserve <2.5) and controls with researchers blinded to the classification throughout the protocol. Myocardial perfusion and vascular function were assessed by 3T cardiac MRI and venous occlusion plethysmography with forearm blood flow (FBF) assessment during serial infusions of acetylcholine, adenosine and the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA).

Results

78 patients were enrolled (42 patients had MVD and 36 were controls), with no differences in cardiovascular risk factors between groups. The MVD group had elevated coronary blood flow (21.3±6.4 vs. 15.1±4.5cm s–1; p<0.001) and global myocardial perfusion (1.36±0.37 vs. 1.13±0.22ml/min/g; p=0.01) at rest. Maximum coronary and myocardial blood flow during hyperaemia was similar in both groups. During exercise, MVD patients achieved similar peak flow (30.5±10.0 vs. 26.3±7.7cm s–1; p=0.07) despite a higher rate-pressure product (20777±5205 vs. 17450±4710bpm.mmHg; p=0.01). Coronary perfusion efficiency, decreased with exercise in the MVD group (61±11% vs. 44±10% p<0.001) but was unchanged in controls. On MRI, MVD had lower hyperaemic endo-epicardial perfusion ratio than controls (0.94±0.08 vs. 1.04±0.13; p=0.001). Augmentation of FBF with acetylcholine was attenuated in MVD patients compared to controls (p=0.02) but the response to adenosine was similar (p=0.13). Infusion of L-NMMA caused a significantly greater reduction in FBF in MVD patients compared to controls (p<0.001).

Exercise Physiology in MVD

Conclusion

Impaired flow reserve in MVD represents a dysfunctional state, characterised by inappropriately elevated resting flow due to increased nitric-oxide synthase mediated vasodilatation. There is abnormal flow distribution in the myocardium predisposing to subendocardial ischaemia, associated with and exacerbated by impaired cardiac-coronary coupling during exercise. These novel findings may represent distinct therapeutic targets.

Acknowledgement/Funding

British Heart Foundation

P6484Invasive and non-invasive characterisation of low gradient aortic stenosis

Background

Low gradient severe aortic stenosis (LGAS) is associated with unfavourable outcomes when compared to high gradient aortic stenosis (HGAS), yet the contributing pathophysiology is poorly understood.

Methods

Symptomatic LGAS and HGAS patients undergoing trans-catheter aortic valve implantation (TAVI) underwent 3T stress perfusion cardiac magnetic resonance imaging (CMR) pre-(within 24 hours) and post-(4–6 months) TAVI. Left ventricular (LV) contractility and coronary flow/pressure were measured during hyperaemia and rapid pacing, immediately before and after TAVI, using a conductance LV catheter and dual-pressure and Doppler sensor–tipped guidewire in the mid-left anterior descending coronary artery.

Results

24 patients were recruited resulting in 19 suitable datasets (LGAS N=9, HGAS N=10, equally matched for comorbidities and B-natriuretic peptide level). LGAS patients had a smaller LV end diastolic volume index (p=0.035) and lower LV mass index (LVMI) (p=0.037). Pre-TAVI stress global endocardium-epicardium gradient was 0.88±0.09 and global myocardial perfusion reserve (MPR) 2.0±0.48 in 14 patients (6 LGAS and 8 HGAS patients, no difference between groups). Pre-TAVI, baseline coronary data demonstrated lower augmentation pressure (AP, p=0.035) and augmentation index (AIx, p=0.02) in the LGAS group. LGAS patients also exhibited a shorter ejection time (p=0.015), larger forward compression waves during rest, hyperaemia and rapid pacing, and smaller backward expansion waves (BEW) (p=0.001). Lower baseline end systolic pressure (p=0.004), inotropy (dP/dt+, p=0.045), lusitropy (dP/dt-, p=0.069), and stroke work (p=0.019) were observed in the LGAS group. Whilst LV size was smaller the LGAS group, rapid pacing induced a more significant drop in end systolic volume (p=0.045) and ejection fraction (p=0.015) in patients with HGAS. Post-TAVI, the hyperaemic BEW fell sharply (p<0.001), along with coronary VTI (p=0.02), and average pulse velocity (p=0.028), and AP and AIx remained lower (p=0.034 and p=0.031, respectively). The forward expansion wave was reduced in LGAS during rapid pacing. The HGAS group displayed a more profound drop in dP/dt+ (p=0.011) and dP/dt- p=0.014) at rest following intervention. Repeat CMR demonstrated statistically significant reduction in LV size and LVMI (p=0.012 and p<0.001, respectively) with significant increase in 3D global peak radial, circumferential and longitudinal strain (p=0.004, p=0.001 and p=0.018, respectively). Post-TAVI stress global endocardium-epicardium gradient was 0.88±0.13 and MPR 2.46±0.59 (improved from pre-TAVI, p=0.05). There was no difference in remodelling patterns or perfusion between the two groups.

Conclusion

This is the first study detailing the combined invasive and CMR pathophysiological changes in LGAS. Despite invasive parameters indicating a disease of less severe AS, the level of perfusion abnormality is disproportionate which may in part, relate to their adverse prognosis.

Acknowledgement/Funding

This research is funded by a Clinical Research Training Fellowship grant from the British Heart Foundation (FS/16/51/32365).

Coronary Microcirculation in Aortic Stenosis

Aortic stenosis is a heterogeneous disorder. Variations in the pathological and physiological responses to pressure overload are incompletely understood and generate a range of flow and pressure gradient patterns, which ultimately cause varying microvascular effects. The impact of cardiac-coronary coupling depends on these pressure and flow effects. In this article, we explore important concepts concerning cardiac physiology and the coronary microcirculation in aortic stenosis and their impact on myocardial remodeling, aortic valve flow patterns, and clinical progression.

Cardiac Myosin-Binding Protein C to Diagnose Acute Myocardial Infarction in the Pre-Hospital Setting

Background Early triage is essential to improve outcomes in patients with suspected acute myocardial infarction (AMI). This study investigated whether cMyC (cardiac myosin-binding protein), a novel biomarker of myocardial necrosis, can aid early diagnosis of AMI and risk stratification. Methods and Results cMyC and high-sensitivity cardiac troponin T were retrospectively quantified in blood samples obtained by ambulance-based paramedics in a prospective, diagnostic cohort study. Patients with ongoing or prolonged periods of chest discomfort, acute dyspnoea in the absence of known pulmonary disease, or clinical suspicion of AMI were recruited. Discrimination power was evaluated by calculating the area under the receiver operating characteristics curve; diagnostic performance was assessed at predefined thresholds. Diagnostic nomograms were derived and validated using bootstrap resampling in logistic regression models. Seven hundred seventy-six patients with median age 68 [58;78] were recruited. AMI was the final adjudicated diagnosis in 22%. Median symptom to sampling time was 70 minutes. cMyC concentration in patients with AMI was significantly higher than with other diagnoses: 98 [43;855] versus 17 [9;42] ng/L. Discrimination power for AMI was better with cMyC than with high-sensitivity cardiac troponin T (area under the curve, 0.839 versus 0.813; P=0.005). At a previously published rule-out threshold (10 ng/L), cMyC reaches 100% sensitivity and negative predictive value in patients after 2 hours of symptoms. In logistic regression analysis, cMyC is superior to high-sensitivity cardiac troponin T and was used to derive diagnostic and prognostic nomograms to evaluate risk of AMI and death. Conclusions In patients undergoing blood draws very early after symptom onset, cMyC demonstrates improved diagnostic discrimination of AMI and could significantly improve the early triage of patients with suspected AMI.

Magnetic Resonance Perfusion or Fractional Flow Reserve in Coronary Disease

BACKGROUND

In patients with stable angina, two strategies are often used to guide revascularization: one involves myocardial-perfusion cardiovascular magnetic resonance imaging (MRI), and the other involves invasive angiography and measurement of fractional flow reserve (FFR). Whether a cardiovascular MRI-based strategy is noninferior to an FFR-based strategy with respect to major adverse cardiac events has not been established.

METHODS

We performed an unblinded, multicenter, clinical-effectiveness trial by randomly assigning 918 patients with typical angina and either two or more cardiovascular risk factors or a positive exercise treadmill test to a cardiovascular MRI-based strategy or an FFR-based strategy. Revascularization was recommended for patients in the cardiovascular-MRI group with ischemia in at least 6% of the myocardium or in the FFR group with an FFR of 0.8 or less. The composite primary outcome was death, nonfatal myocardial infarction, or target-vessel revascularization within 1 year. The noninferiority margin was a risk difference of 6 percentage points.

RESULTS

A total of 184 of 454 patients (40.5%) in the cardiovascular-MRI group and 213 of 464 patients (45.9%) in the FFR group met criteria to recommend revascularization (P = 0.11). Fewer patients in the cardiovascular-MRI group than in the FFR group underwent index revascularization (162 [35.7%] vs. 209 [45.0%], P = 0.005). The primary outcome occurred in 15 of 421 patients (3.6%) in the cardiovascular-MRI group and 16 of 430 patients (3.7%) in the FFR group (risk difference, -0.2 percentage points; 95% confidence interval, -2.7 to 2.4), findings that met the noninferiority threshold. The percentage of patients free from angina at 12 months did not differ significantly between the two groups (49.2% in the cardiovascular-MRI group and 43.8% in the FFR group, P = 0.21).

CONCLUSIONS

Among patients with stable angina and risk factors for coronary artery disease, myocardial-perfusion cardiovascular MRI was associated with a lower incidence of coronary revascularization than FFR and was noninferior to FFR with respect to major adverse cardiac events. (Funded by the Guy's and St. Thomas' Biomedical Research Centre of the National Institute for Health Research and others; MR-INFORM ClinicalTrials.gov number, NCT01236807.).

Comparative Analysis of Circulating Noncoding RNAs Versus Protein Biomarkers in the Detection of Myocardial Injury

RATIONALE

Noncoding RNAs (ncRNAs), including microRNAs (miRNAs), circular RNAs (circRNAs), and long noncoding RNAs (lncRNAs), are proposed novel biomarkers of myocardial injury. Their release kinetics have not been explored without confounding by heparin nor has their relationship to myocardial protein biomarkers.

OBJECTIVE

To compare ncRNA types in heparinase-treated samples with established and emerging protein biomarkers for myocardial injury.

METHODS AND RESULTS

Screening of 158 circRNAs and 21 lncRNAs in human cardiac tissue identified 12 circRNAs and 11 lncRNAs as potential biomarkers with cardiac origin. Eleven miRNAs were included. At low spike-in concentrations of myocardial tissue, significantly higher regression coefficients were observed across ncRNA types compared with cardiac troponins and cMyBP-C (cardiac myosin-binding protein C). Heparinase treatment of serial plasma and serum samples of patients undergoing transcoronary ablation of septal hypertrophy removed spurious correlations between miRNAs in non-heparinase-treated samples. After transcoronary ablation of septal hypertrophy, muscle-enriched miRNAs (miR-1 and miR-133a) showed a steeper and earlier increase than cardiac-enriched miRNAs (miR-499 and miR-208b). Putative cardiac lncRNAs, including LIPCAR (long intergenic noncoding RNA predicting cardiac remodeling and survival), did not rise, refuting a predominant cardiac origin. Cardiac circRNAs remained largely undetectable. In a validation cohort of acute myocardial infarction, receiver operating characteristic curve analysis revealed noninferiority of cardiac-enriched miRNAs, but miRNAs failed to identify cases presenting with low troponin values. cMyBP-C was validated as a biomarker with highly sensitive properties, and the combination of muscle-enriched miRNAs with high-sensitive cardiac troponin T and cMyBP-C returned the highest area under the curve values.

CONCLUSIONS

In a comparative assessment of ncRNAs and protein biomarkers for myocardial injury, cMyBP-C showed properties as the most sensitive cardiac biomarker while miRNAs emerged as promising candidates to integrate ncRNAs with protein biomarkers. Sensitivity of current miRNA detection is inferior to cardiac proteins but a multibiomarker combination of muscle-enriched miRNAs with cMyBP-C and cardiac troponins could open a new path of integrating complementary characteristics of different biomarker types.

Percutaneous Revascularization for Ischemic Ventricular Dysfunction: Rationale and Design of the REVIVED-BCIS2 Trial: Percutaneous Coronary Intervention for Ischemic Cardiomyopathy

OBJECTIVES

Evaluate whether PCI in combination with optimal medical therapy (OMT) will reduce all-cause death and hospitalization for HF compared to a strategy of OMT alone.

BACKGROUND

Ischemic cardiomyopathy (ICM) is the most common cause of heart failure (HF) and is associated with significant mortality and morbidity. Surgical revascularization has been shown to improve long-term outcomes in some patients, but surgery itself carries a major early hazard. Percutaneous coronary intervention (PCI) may allow a better balance between risk and benefit.

METHODS

REVIVED-BCIS2 is a prospective, multi-center, open-label, randomized controlled trial, funded by the National Institute for Health Research in the United Kingdom. Follow-up will be for at least 2 years from randomization. Secondary outcomes include left ventricular ejection fraction (LVEF), quality of life scores, appropriate implantable cardioverter defibrillator therapy and acute myocardial infarction. Patients with LVEF ≤35%, extensive coronary disease and demonstrable myocardial viability are eligible for inclusion and those with a myocardial infarction within 4 weeks, decompensated HF or sustained ventricular arrhythmias within 72 h are excluded. A trial of 700 patients has more than 85% power to detect a 30% relative reduction in hazard.

RESULTS

A total of 400 patients have been enrolled to date.

CONCLUSIONS

International guidelines do not provide firm recommendations on the role of PCI in managing severe ICM, because of a lack of robust evidence. REVIVED-BCIS2 will provide the first randomized data on the efficacy and safety of PCI in ICM and has the potential to inform guidelines pertaining to both revascularization and HF. (Study of Efficacy and Safety of Percutaneous Coronary Intervention to Improve Survival in Heart Failure [REVIVED-BCIS2]; NCT01920048) (REVascularisation for Ischaemic VEntricular Dysfunction; ISRCTN45979711).

In mammalian skeletal muscle, phosphorylation of TOMM22 by protein kinase CSNK2/CK2 controls mitophagy

In yeast, Tom22, the central component of the TOMM (translocase of outer mitochondrial membrane) receptor complex, is responsible for the recognition and translocation of synthesized mitochondrial precursor proteins, and its protein kinase CK2-dependent phosphorylation is mandatory for TOMM complex biogenesis and proper mitochondrial protein import. In mammals, the biological function of protein kinase CSNK2/CK2 remains vastly elusive and it is unknown whether CSNK2-dependent phosphorylation of TOMM protein subunits has a similar role as that in yeast. To address this issue, we used a skeletal muscle-specific Csnk2b/Ck2β-conditional knockout (cKO) mouse model. Phenotypically, these skeletal muscle Csnk2b cKO mice showed reduced muscle strength and abnormal metabolic activity of mainly oxidative muscle fibers, which point towards mitochondrial dysfunction. Enzymatically, active muscle lysates from skeletal muscle Csnk2b cKO mice phosphorylate murine TOMM22, the mammalian ortholog of yeast Tom22, to a lower extent than lysates prepared from controls. Mechanistically, CSNK2-mediated phosphorylation of TOMM22 changes its binding affinity for mitochondrial precursor proteins. However, in contrast to yeast, mitochondrial protein import seems not to be affected in vitro using mitochondria isolated from muscles of skeletal muscle Csnk2b cKO mice. PINK1, a mitochondrial health sensor that undergoes constitutive import under physiological conditions, accumulates within skeletal muscle Csnk2b cKO fibers and labels abnormal mitochondria for removal by mitophagy as demonstrated by the appearance of mitochondria-containing autophagosomes through electron microscopy. Mitophagy can be normalized by either introduction of a phosphomimetic TOMM22 mutant in cultured myotubes, or by in vivo electroporation of phosphomimetic Tomm22 into muscles of mice. Importantly, transfection of the phosphomimetic Tomm22 mutant in muscle cells with ablated Csnk2b restored their oxygen consumption rate comparable to wild-type levels. In sum, our data show that mammalian CSNK2-dependent phosphorylation of TOMM22 is a critical switch for mitophagy and reveal CSNK2-dependent physiological implications on metabolism, muscle integrity and behavior.

Doppler Versus Thermodilution-Derived Coronary Microvascular Resistance to Predict Coronary Microvascular Dysfunction in Patients With Acute Myocardial Infarction or Stable Angina Pectoris

Coronary microvascular resistance is increasingly measured as a predictor of clinical outcomes, but there is no accepted gold-standard measurement. We compared the diagnostic accuracy of 2 invasive indices of microvascular resistance, Doppler-derived hyperemic microvascular resistance (hMR) and thermodilution-derived index of microcirculatory resistance (IMR), at predicting microvascular dysfunction. A total of 54 patients (61 ± 10 years) who underwent cardiac catheterization for stable coronary artery disease (n = 10) or acute myocardial infarction (n = 44) had simultaneous intracoronary pressure, Doppler flow velocity and thermodilution flow data acquired from 74 unobstructed vessels, at rest and during hyperemia. Three independent measurements of microvascular function were assessed, using predefined dichotomous thresholds: (1) coronary flow reserve (CFR), the average value of Doppler- and thermodilution-derived CFR; (2) cardiovascular magnetic resonance (CMR) derived myocardial perfusion reserve index; and (3) CMR-derived microvascular obstruction. hMR correlated with IMR (rho = 0.41, p <0.0001). hMR had better diagnostic accuracy than IMR to predict CFR (area under curve [AUC] 0.82 vs 0.58, p <0.001, sensitivity and specificity 77% and 77% vs 51% and 71%) and myocardial perfusion reserve index (AUC 0.85 vs 0.72, p = 0.19, sensitivity and specificity 82% and 80% vs 64% and 75%). In patients with acute myocardial infarction, the AUCs of hMR and IMR at predicting extensive microvascular obstruction were 0.83 and 0.72, respectively (p = 0.22, sensitivity and specificity 78% and 74% vs 44% and 91%). We conclude that these 2 invasive indices of coronary microvascular resistance only correlate modestly and so cannot be considered equivalent. In our study, the correlation between independent invasive and noninvasive measurements of microvascular function was better with hMR than with IMR.

Prognostic Value of Quantitative Stress Perfusion Cardiac Magnetic Resonance

OBJECTIVES

This study sought to evaluate the prognostic usefulness of visual and quantitative perfusion cardiac magnetic resonance (CMR) ischemic burden in an unselected group of patients and to assess the validity of consensus-based ischemic burden thresholds extrapolated from nuclear studies.

BACKGROUND

There are limited data on the prognostic value of assessing myocardial ischemic burden by CMR, and there are none using quantitative perfusion analysis.

METHODS

Patients with suspected coronary artery disease referred for adenosine-stress perfusion CMR were included (n = 395; 70% male; age 58 ± 13 years). The primary endpoint was a composite of cardiovascular death, nonfatal myocardial infarction, aborted sudden death, and revascularization after 90 days. Perfusion scans were assessed visually and with quantitative analysis. Cross-validated Cox regression analysis and net reclassification improvement were used to assess the incremental prognostic value of visual or quantitative perfusion analysis over a baseline clinical model, initially as continuous covariates, then using accepted thresholds of ≥2 segments or ≥10% myocardium.

RESULTS

After a median 460 days (interquartile range: 190 to 869 days) follow-up, 52 patients reached the primary endpoint. At 2 years, the addition of ischemic burden was found to increase prognostic value over a baseline model of age, sex, and late gadolinium enhancement (baseline model area under the curve [AUC]: 0.75; visual AUC: 0.84; quantitative AUC: 0.85). Dichotomized quantitative ischemic burden performed better than visual assessment (net reclassification improvement 0.043 vs. 0.003 against baseline model).

CONCLUSIONS

This study was the first to address the prognostic benefit of quantitative analysis of perfusion CMR and to support the use of consensus-based ischemic burden thresholds by perfusion CMR for prognostic evaluation of patients with suspected coronary artery disease. Quantitative analysis provided incremental prognostic value to visual assessment and established risk factors, potentially representing an important step forward in the translation of quantitative CMR perfusion analysis to the clinical setting.

Direct Comparison of Cardiac Myosin-Binding Protein C With Cardiac Troponins for the Early Diagnosis of Acute Myocardial Infarction

BACKGROUND

Cardiac myosin-binding protein C (cMyC) is a cardiac-restricted protein that is more abundant than cardiac troponins (cTn) and is released more rapidly after acute myocardial infarction (AMI). We evaluated cMyC as an adjunct or alternative to cTn in the early diagnosis of AMI.

METHODS

Unselected patients (N=1954) presenting to the emergency department with symptoms suggestive of AMI, concentrations of cMyC, and high-sensitivity (hs) and standard-sensitivity cTn were measured at presentation. The final diagnosis of AMI was independently adjudicated using all available clinical and biochemical information without knowledge of cMyC. The prognostic end point was long-term mortality.

RESULTS

Final diagnosis was AMI in 340 patients (17%). Concentrations of cMyC at presentation were significantly higher in those with versus without AMI (median, 237 ng/L versus 13 ng/L, P<0.001). Discriminatory power for AMI, as quantified by the area under the receiver-operating characteristic curve (AUC), was comparable for cMyC (AUC, 0.924), hs-cTnT (AUC, 0.927), and hs-cTnI (AUC, 0.922) and superior to cTnI measured by a contemporary sensitivity assay (AUC, 0.909). The combination of cMyC with hs-cTnT or standard-sensitivity cTnI (but not hs-cTnI) led to an increase in AUC to 0.931 (P<0.0001) and 0.926 (P=0.003), respectively. Use of cMyC more accurately classified patients with a single blood test into rule-out or rule-in categories: Net Reclassification Improvement +0.149 versus hs-cTnT, +0.235 versus hs-cTnI (P<0.001). In early presenters (chest pain <3 h), the improvement in rule-in/rule-out classification with cMyC was larger compared with hs-cTnT (Net Reclassification Improvement +0.256) and hs-cTnI (Net Reclassification Improvement +0.308; both P<0.001). Comparing the C statistics, cMyC was superior to hs-cTnI and standard sensitivity cTnI (P<0.05 for both) and similar to hs-cTnT at predicting death at 3 years.

CONCLUSIONS

cMyC at presentation provides discriminatory power comparable to hs-cTnT and hs-cTnI in the diagnosis of AMI and may perform favorably in patients presenting early after symptom onset.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00470587.