Abnormal Coronary Flow Velocity Reserve After Coronary Intervention Is Associated With Cardiac Marker Elevation

Health position paper and redox perspectives on reactive oxygen species as signals and targets of cardioprotection

The present review summarizes the beneficial and detrimental roles of reactive oxygen species in myocardial ischemia/reperfusion injury and cardioprotection. In the first part, the continued need for cardioprotection beyond that by rapid reperfusion of acute myocardial infarction is emphasized. Then, pathomechanisms of myocardial ischemia/reperfusion to the myocardium and the coronary circulation and the different modes of cell death in myocardial infarction are characterized. Different mechanical and pharmacological interventions to protect the ischemic/reperfused myocardium in elective percutaneous coronary interventions and coronary artery bypass grafting, in acute myocardial infarction and in cardiotoxicity from cancer therapy are detailed. The second part keeps the focus on ROS providing a comprehensive overview of molecular and cellular mechanisms involved in ischemia/reperfusion injury. Starting from mitochondria as the main sources and targets of ROS in ischemic/reperfused myocardium, a complex network of cellular and extracellular processes is discussed, including relationships with Ca2+ homeostasis, thiol group redox balance, hydrogen sulfide modulation, cross-talk with NAPDH oxidases, exosomes, cytokines and growth factors. While mechanistic insights are needed to improve our current therapeutic approaches, advancements in knowledge of ROS-mediated processes indicate that detrimental facets of oxidative stress are opposed by ROS requirement for physiological and protective reactions. This inevitable contrast is likely to underlie unsuccessful clinical trials and limits the development of novel cardioprotective interventions simply based upon ROS removal.

Prolonged infusion of bivalirudin after elective percutaneous coronary intervention protects against procedural myocardial injury (a COBER study)-a randomized trial

Procedural myocardial injury (PMI), which is the most common complication of elective percutaneous coronary intervention (ePCI), is associated with future adverse cardiac events. In this randomized pilot trial, we assessed the effects of prolonged use of the anti-coagulant bivalirudin on PMI after ePCI. Patients undergoing ePCI were randomized into the following two groups: the bivalirudin use during operation group (BUDO, 0.75 mg/kg bolus plus 1.75 mg/kg/h) and the bivalirudin use during and after operation for 4 h (BUDAO, 0.75 mg/kg bolus plus 1.75 mg/kg/h). Blood samples were collected before and 24 h after ePCI (per 8 h). The primary outcome, PMI, was defined as an increase in post-ePCI cardiac troponin I (cTnI) levels of > 1 × 99th% upper reference limit (URL) when the pre-PCI cTnI was normal or a rise in cTnI of > 20% of the baseline value when it was above the 99th percentile URL, but it was stable or falling. Major PMI (MPMI) was defined as a post-ePCI cTnI increase of > 5 × 99th% URL. A total of 330 patients were included (n = 165 per group). The incidences of PMI and MPMI were not significantly higher in the BUDO group than in the BUDAO group (PMI: 115 [69.70%] vs. 102 [61.82%], P = 0.164; MPMI: 81 [49.09%] vs. 70 [42.42%], P = 0.269). However, the absolute change in cTnI levels (calculated as the peak value 24 h post-PCI minus the pre-PCI value) was notably larger in the BUDO group (0.13 [0.03, 1.95]) than in the BUDAO group (0.07 [0.01, 0.61]) (P = 0.045). Moreover, the incidence of bleeding events was similar between the two groups (BUDO: 0 [0.00%]; BUDAO: 2 [1.21%], P = 0.498). Prolonged infusion of bivalirudin for 4 h after ePCI reduces PMI severity without increasing the risk of bleeding.ClinicalTrials.gov.Number: NCT04120961, 09/10/2019.

Empagliflozin inhibits coronary microvascular dysfunction and reduces cardiac pericyte loss in db/db mice

Background

Coronary microvascular dysfunction (CMD) is a pathophysiological feature of diabetic heart disease. However, whether sodium-glucose cotransporter 2 (SGLT2) inhibitors protect the cardiovascular system by alleviating CMD is not known.

Objective

We observed the protective effects of empagliflozin (EMPA) on diabetic CMD.

Materials and methods

The mice were randomly divided into a db/db group and a db/db + EMPA group, and db/m mice served as controls. At 8 weeks of age, the db/db + EMPA group was given empagliflozin 10 mg/(kg⋅d) by gavage for 8 weeks. Body weight, fasting blood glucose and blood pressure were dynamically observed. Cardiac systolic and diastolic function and coronary flow reserve (CFR) were detected using echocardiography. The coronary microvascular structure and distribution of cardiac pericytes were observed using immunofluorescence staining. Picrosirius red staining was performed to evaluate cardiac fibrosis.

Results

Empagliflozin lowered the increased fasting blood glucose levels of the db/db group. The left ventricular ejection fraction, left ventricular fractional shortening, E/A ratio and E/e' ratio were not significantly different between the three groups. CFR was decreased in the db/db group, but EMPA significantly improved CFR. In contrast to the sparse and abnormal expansion of coronary microvessels observed in the db/db group, the number of coronary microvessels was increased, and the capillary diameter was decreased in the db/db + EMPA group. The number and microvascular coverage of cardiac pericytes were reduced in the db/db mice but were improved by EMPA. The cardiac fibrosis was increased in db/db group and may alleviate by EMPA.

Conclusion

Empagliflozin inhibited CMD and reduced cardiac pericyte loss in diabetic mice.

Atorvastatin attenuates ferroptosis-dependent myocardial injury and inflammation following coronary microembolization via the Hif1a/Ptgs2 pathway

Objectives: Coronary microembolization (CME) represents a serious periprocedural complication after percutaneous coronary intervention. Ferroptosis has been identified in multiple cardiovascular diseases. In this study, we aimed to investigate the effects of atorvastatin (ATV) on ferroptosis and inflammation following CME and elucidate the underlying mechanism. Methods: We established a rat model of CME by injecting microspheres into the left ventricle. Deferoxamine (DFO), a selective ferroptosis inhibitor, or ATV was pretreated before modeling. Cardiac function and cardiac troponin T (cTnT) levels were detected. Levels of ferroptosis-associated genes, malondialdehyde (MDA), glutathione (GSH), and ferrous iron (Fe²⁺) were measured to validate ferroptosis. Levels of tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) were assayed to determine the inflammation. Chromatin immunoprecipitation was performed to determine the binding of hypoxia-inducible factor 1 subunit alpha (Hif1a) to the promoter of prostaglandin-endoperoxide synthase-2 (Ptgs2). Results: Ferroptosis and inflammation were induced following CME with increased levels of MDA (∼2.5 fold, p < 0.01), Fe²⁺ (∼1.5 fold, p < 0.01), TNF-α, and IL-1β and decreased GSH levels (∼42%, p < 0.01). Meanwhile, the level of Ptgs2 was significantly increased, while those of glutathione peroxidase 4 (Gpx4) and solute carrier family 7 member 11 (Slc7a11) were decreased. The level of cTnT was increased by 7-fold (p < 0.01). Left ventricular ejection fraction (LVEF) was significantly reduced (∼85% in the sham group versus ∼45% in the CME group, p < 0.01). DFO or Ptgs2 silencing inhibited the increase of MDA, Ptgs2, TNF-α, and IL-1β, and induced the levels of GSH and Gpx4, followed by reduction in cTnT levels by approximately 50% (p < 0.01). LVEF was improved by approximately 2 fold (p < 0.01). Mechanistically, the transcription factor Hif1a bound to the promoter of Ptgs2 and upregulated its expression. In addition, ATV inhibited the activation of the Hif1a/Ptgs2 axis and attenuated cardiac ferroptosis and inflammation, thus ameliorating CME-induced myocardial injury (LVEF, ∼34% elevation; cTnT, ∼1.8 fold decrease, p < 0.01). Conclusion: Atorvastatin ameliorates ferroptosis-mediated myocardial injury and inflammation following CME via the Hif1a/Ptgs2 pathway.

Advances and Challenges in Biomarkers Use for Coronary Microvascular Dysfunction: From Bench to Clinical Practice

Coronary microvascular dysfunction (CMD) is related to a broad variety of clinical scenarios in which cardiac microvasculature is morphologically and functionally affected, and it is associated with impaired responses to vasoactive stimuli. Although the prevalence of CMD involves about half of all patients with chronic coronary syndromes and more than 20% of those with acute coronary syndrome, the diagnosis of CMD is often missed, leading to the underestimation of its clinical importance. The established and validated techniques for the measurement of coronary microvascular function are invasive and expensive. An ideal method to assess endothelial dysfunction should be accurate, non-invasive, cost-effective and accessible. There are varieties of biomarkers available, potentially involved in microvascular disease, but none have been extensively validated in this heterogeneous clinical population. The investigation of potential biomarkers linked to microvascular dysfunction might improve the assessment of the diagnosis, risk stratification, disease progression and therapy response. This review article offers an update about traditional and novel potential biomarkers linked to CMD.

Coronary blood flow in heart failure: cause, consequence and bystander

Heart failure is a clinical syndrome where cardiac output is not sufficient to sustain adequate perfusion and normal bodily functions, initially during exercise and in more severe forms also at rest. The two most frequent forms are heart failure of ischemic origin and of non-ischemic origin. In heart failure of ischemic origin, reduced coronary blood flow is causal to cardiac contractile dysfunction, and this is true for stunned and hibernating myocardium, coronary microembolization, myocardial infarction and post-infarct remodeling, possibly also for the takotsubo syndrome. The most frequent form of non-ischemic heart failure is dilated cardiomyopathy, caused by genetic mutations, myocarditis, toxic agents or sustained tachyarrhythmias, where alterations in coronary blood flow result from and contribute to cardiac contractile dysfunction. Hypertrophic cardiomyopathy is caused by genetic mutations but can also result from increased pressure and volume overload (hypertension, valve disease). Heart failure with preserved ejection fraction is characterized by pronounced coronary microvascular dysfunction, the causal contribution of which is however not clear. The present review characterizes the alterations of coronary blood flow which are causes or consequences of heart failure in its different manifestations. Apart from any potentially accompanying coronary atherosclerosis, all heart failure entities share common features of impaired coronary blood flow, but to a different extent: enhanced extravascular compression, impaired nitric oxide-mediated, endothelium-dependent vasodilation and enhanced vasoconstriction to mediators of neurohumoral activation. Impaired coronary blood flow contributes to the progression of heart failure and is thus a valid target for established and novel treatment regimens.

A fresh look at coronary microembolization

Mechanical stress from haemodynamic perturbations or interventional manipulation of epicardial coronary atherosclerotic plaques with inflammatory destabilization can release particulate debris, thrombotic material and soluble substances into the coronary circulation. The physical material obstructs the coronary microcirculation, whereas the soluble substances induce endothelial dysfunction and facilitate vasoconstriction. Coronary microvascular obstruction and dysfunction result in patchy microinfarcts accompanied by an inflammatory reaction, both of which contribute to progressive myocardial contractile dysfunction. In clinical studies, the benefit of protection devices to retrieve atherothrombotic debris during percutaneous coronary interventions has been modest, and the treatment of microembolization has mostly relied on antiplatelet and vasodilator agents. The past 25 years have witnessed a relative proportional increase in non-ST-segment elevation myocardial infarction in the presentation of acute coronary syndromes. An associated increase in the incidence of plaque erosion rather than rupture has also been recognized as a key mechanism in the past decade. We propose that coronary microembolization is a decisive link between plaque erosion at the culprit lesion and the manifestation of non-ST-segment elevation myocardial infarction. In this Review, we characterize the features and mechanisms of coronary microembolization and discuss the clinical trials of drugs and devices for prevention and treatment.

Immediate post-procedural functional assessment of percutaneous coronary intervention: current evidence and future directions

Percutaneous coronary intervention (PCI) guided by coronary physiology provides symptomatic benefit and improves patient outcomes. Nevertheless, over one-fourth of patients still experience recurrent angina or major adverse cardiac events following the index procedure. Coronary angiography, the current workhorse for evaluating PCI efficacy, has limited ability to identify suboptimal PCI results. Accumulating evidence supports the usefulness of immediate post-procedural functional assessment. This review discusses the incidence and possible mechanisms behind a suboptimal physiology immediately after PCI. Furthermore, we summarize the current evidence base supporting the usefulness of immediate post-PCI functional assessment for evaluating PCI effectiveness, guiding PCI optimization, and predicting clinical outcomes. Multiple observational studies and post hoc analyses of datasets from randomized trials demonstrated that higher post-PCI functional results are associated with better clinical outcomes as well as a reduced rate of residual angina and repeat revascularization. As such, post-PCI functional assessment is anticipated to impact patient management, secondary prevention, and resource utilization. Pre-PCI physiological guidance has been shown to improve clinical outcomes and reduce health care costs. Whether similar benefits can be achieved using post-PCI physiological assessment requires evaluation in randomized clinical outcome trials.

Clinical decision-making: Challenging traditional assumptions

Clinical decision-making that best serves the interests of our patients requires the synthesis of evidence-based medicine, sound clinical judgment and guidelines. However, a relatively low percentage of clinical guidelines are based on well-designed prospective randomized clinical trials. Thus the foundation on which good clinical outcomes can be reasonably expected should be based on i) data derived from the most applicable and highest quality clinical studies available, and ii) 'tried and tested' clinical maxims acquired through experience that are, in turn, those ideas that are in keeping with a reasonable body of medical opinion. It follows that poor decision-making and unfavorable clinical outcomes can be linked to inappropriate or inferior quality evidence, or incorrectly conceived or implemented clinical judgment. Here we review selected areas of recent controversy in clinical cardiology, highlighting the critical role of evidence-based medicine when making informed clinical decisions to help avoid harm in our patients.

The many faces of myocardial ischaemia and angina

Obstructive disease of the epicardial coronary arteries is the main cause of angina. However, a number of patients with anginal symptoms have normal coronaries or non-obstructive coronary artery disease (CAD) despite electrocardiographic evidence of ischaemia during stress testing. In addition to limited microvascular vasodilator capacity, the coronary microcirculation of these patients is particularly sensitive to vasoconstrictor stimuli, in a condition known as microvascular angina. This review briefly summarizes the determinants and control of coronary blood flow (CBF) and myocardial perfusion. It subsequently analyses the mechanisms responsible for transient myocardial ischaemia: obstructive CAD, coronary spasm and coronary microvascular dysfunction in the absence of epicardial coronary lesions, and variable combinations of structural anomalies, impaired endothelium-dependent and/or -independent vasodilation, and enhanced perception of pain. Lastly, we exemplify mechanism of angina during tachycardia. Distal to a coronary stenosis, coronary dilator reserve is already recruited and can be nearly exhausted at rest distal to a severe stenosis. Increased heart rate reduces the duration of diastole and thus CBF when metabolic vasodilation is no longer able to increase CBF. The increase in myocardial oxygen consumption and resulting metabolic vasodilation in adjacent myocardium without stenotic coronary arteries further acts to divert blood flow away from the post-stenotic coronary vascular bed through collaterals.

Fractional Flow Reserve following Percutaneous Coronary Intervention

Fractional flow reserve (FFR) is routinely used to determine lesion severity prior to percutaneous coronary intervention (PCI). However, there is an increasing recognition that FFR may also be useful following PCI to identify mechanisms leading to restenosis and the need for repeat revascularization. Post-PCI FFR is associated with the presence and severity of stent under-expansion and may help identify peri-stent-related complications. FFR pullback may also unmask other functionally significant lesions within the target vessel that were not appreciable on angiography. Recent studies have confirmed the prognostic utility of performing routine post-PCI FFR and suggest possible interventional targets that would improve stent durability. In this review, we detail the theoretical basis underlying post-PCI FFR, provide practical tips to facilitate measurement, and discuss the growing evidence supporting its use.

Perturbations in myocardial perfusion and oxygen balance in swine with multiple risk factors: a novel model of ischemia and no obstructive coronary artery disease

Comorbidities of ischemic heart disease, including diabetes mellitus (DM), hypercholesterolemia (HC) and chronic kidney disease (CKD), are associated with coronary microvascular dysfunction (CMD). Increasing evidence suggests that CMD may contribute to myocardial ‘Ischemia and No Obstructive Coronary Artery disease’ (INOCA). In the present study, we tested the hypothesis that CMD results in perturbations in myocardial perfusion and oxygen delivery using a novel swine model with multiple comorbidities. DM (streptozotocin), HC (high-fat diet) and CKD (renal embolization) were induced in 10 female swine (DM + HC + CKD), while 12 healthy female swine on a normal diet served as controls (Normal). After 5 months, at a time when coronary atherosclerosis was still negligible, myocardial perfusion, metabolism, and function were studied at rest and during treadmill exercise. DM + HC + CKD animals showed hyperglycemia, hypercholesterolemia, and impaired kidney function. During exercise, DM + HC + CKD swine demonstrated perturbations in myocardial blood flow and oxygen delivery, necessitating a higher myocardial oxygen extraction—achieved despite reduced capillary density—resulting in lower coronary venous oxygen levels. Moreover, myocardial efficiency was lower, requiring higher oxygen consumption for a given level of myocardial work. These perturbations in myocardial oxygen balance were associated with lower myocardial lactate consumption, stroke volume, and LVdP/dt_max, suggestive of myocardial ischemia and dysfunction. Further analyses showed a reduction in adenosine-recruitable coronary flow reserve, but this was exclusively the result of an increase in basal coronary blood flow, while maximal coronary flow per gram of myocardium was maintained; the latter was consistent with the unchanged arteriolar wall/lumen ratio, arteriolar density and peri-arteriolar collagen content. However, isolated small arteries displayed selective blunting of endothelium-dependent vasodilation in response to bradykinin in DM + HC + CKD swine, suggesting that changes in coronary microvascular function rather than in structure contributed to the perturbations in myocardial oxygen delivery. In conclusion, common comorbidities in swine result in CMD, in the absence of appreciable atherosclerosis, which is severe enough to produce perturbations in myocardial oxygen balance, particularly during exercise, resembling key features of INOCA.

The coronary circulation in acute myocardial ischaemia/reperfusion injury: a target for cardioprotection

The coronary circulation is both culprit and victim of acute myocardial infarction. The rupture of an epicardial atherosclerotic plaque with superimposed thrombosis causes coronary occlusion, and this occlusion must be removed to induce reperfusion. However, ischaemia and reperfusion cause damage not only in cardiomyocytes but also in the coronary circulation, including microembolization of debris and release of soluble factors from the culprit lesion, impairment of endothelial integrity with subsequently increased permeability and oedema formation, platelet activation and leucocyte adherence, erythrocyte stasis, a shift from vasodilation to vasoconstriction, and ultimately structural damage to the capillaries with eventual no-reflow, microvascular obstruction (MVO), and intramyocardial haemorrhage (IMH). Therefore, the coronary circulation is a valid target for cardioprotection, beyond protection of the cardiomyocyte. Virtually all of the above deleterious endpoints have been demonstrated to be favourably influenced by one or the other mechanical or pharmacological cardioprotective intervention. However, no-reflow is still a serious complication of reperfused myocardial infarction and carries, independently from infarct size, an unfavourable prognosis. MVO and IMH can be diagnosed by modern imaging technologies, but still await an effective therapy. The current review provides an overview of strategies to protect the coronary circulation from acute myocardial ischaemia/reperfusion injury. This article is part of a Cardiovascular Research Spotlight Issue entitled 'Cardioprotection Beyond the Cardiomyocyte', and emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Myocardial ischemia: lack of coronary blood flow, myocardial oxygen supply-demand imbalance, or what?

This opinionated article reviews current concepts of myocardial ischemia. Specifically, the historical background is briefly presented. Then, the prevailing paradigm of myocardial oxygen-supply-demand imbalance is criticized since demand is a virtual parameter that cannot be measured and data on measurements of myocardial blood flow and contractile function rather support matching between flow and function. Finally, a concept of myocardial ischemia that focusses on the reduction of coronary blood flow to below 8-10 µl/g per beat with consequences for myocardial electrical, metabolic, contractile and morphological features is advocated.

Coronary microembolization and microvascular dysfunction

Plaque erosion, fissuring or rupture occurs spontaneously or during coronary interventions. At some residual blood flow, the atherothrombotic debris is washed into the coronary microcirculation, causing physical obstruction, vasoconstriction, inflammation and ultimately microinfarction. Coronary microembolization also contributes to microvascular obstruction in reperfused acute myocardial infarction. Patients with microvascular obstruction after reperfused myocardial infarction have worse prognosis. Cardioprotective strategies to avoid acute coronary microembolization and rescue myocardium from microvascular obstruction have not yet been established in clinical practice. Subclinical coronary microembolization together with release of thrombogenic, vasoconstrictor and inflammatory substances from a culprit lesion can sensitize the coronary microcirculation and contribute to angina in the absence of major epicardial coronary obstruction. Repetitive coronary microembolization can induce progressive loss of functional cardiomyocytes and induce heart failure in the absence of overt myocardial infarction.

Novel biomarkers of coronary microvascular disease

Coronary microvascular disease in the absence of myocardial diseases has traditionally been diagnosed through coronary reactivity testing in the cardiac catheterization laboratory. Compared with invasive procedures, blood-based biomarkers may have reduced cost, less risk of physical harm and greater accessibility, making them ideal for an outpatient management strategy. There are a variety of biomarkers available with potential utility in the management of microvascular disease; however, none have yet been extensively validated or established in this clinical patient population.

Coronary artery dominance and the risk of adverse clinical events following percutaneous coronary intervention: insights from the prospective, randomised TWENTE trial

AIMS

To investigate the prognostic value of coronary dominance for various adverse clinical events following the implantation of drug-eluting stents.

METHODS AND RESULTS

We assessed two-year follow-up data of 1,387 patients from the randomised TWENTE trial. Based on the origin of the posterior descending coronary artery, coronary circulation was categorised into left and non-left dominance (i.e., right and balanced). Target vessel-related myocardial infarction (MI) was defined according to the updated Academic Research Consortium (ARC) definition (2x upper reference limit of creatine kinase [CK], confirmed by CK-MB elevation), and periprocedural MI (PMI) as MI ≤48 hours following PCI. One hundred and thirty-six patients (9.8%) had left and 1,251 (90.2%) non-left dominance. Target lesions were more frequently located in dominant arteries (p<0.005). Left dominance was associated with more severe calcifications (p=0.006) and more bifurcation lesions (p=0.031). Non-left dominance tended to be less frequent in men (p=0.09). Left coronary dominance was associated with more target vessel-related MI (14 [10.3%] vs. 62 [5.0%], p=0.009). Left dominance independently predicted PMI (adjusted HR 2.19, 95% CI: 1.15-4.15, p=0.017), while no difference in other clinical endpoints was observed between dominance groups.

CONCLUSIONS

In the population of the TWENTE trial, we observed a higher incidence of periprocedural myocardial infarction in patients who had left coronary dominance.

Coronary microvascular obstruction in acute myocardial infarction

The success of a primary percutaneous intervention (PCI) in the setting of ST elevation myocardial infarction depends on the functional and structural integrity of coronary microcirculation. Coronary microvascular dysfunction and obstruction (CMVO) occurs in up to half of patients submitted to apparently successful primary PCI and is associated to a much worse outcome. The current review summarizes the complex mechanisms responsible for CMVO, including pre-existing coronary microvascular dysfunction, and highlights the current limitations in the assessment of microvascular function. More importantly, at the light of the substantial failure of trials hitherto published on the treatment of CMVO, this review proposes a novel integrated therapeutic approach, which should overcome the limitations of previous studies.

Fundamentals in clinical coronary physiology: why coronary flow is more important than coronary pressure

Wide attention for the appropriateness of coronary stenting in stable ischaemic heart disease (IHD) has increased interest in coronary physiology to guide decision making. For many, coronary physiology equals the measurement of coronary pressure to calculate the fractional flow reserve (FFR). While accumulating evidence supports the contention that FFR-guided revascularization is superior to revascularization based on coronary angiography, it is frequently overlooked that FFR is a coronary pressure-derived estimate of coronary flow impairment. It is not the same as the direct measures of coronary flow from which it was derived, and which are critical determinants of myocardial ischaemia. This review describes why coronary flow is physiologically and clinically more important than coronary pressure, details the resulting limitations and clinical consequences of FFR-guided clinical decision making, describes the scientific consequences of using FFR as a gold standard reference test, and discusses the potential of coronary flow to improve risk stratification and decision making in IHD.

Cardioprotective effect of high-dose intragraft adenosine infusion on microvascular function and prevention of no-reflow during saphenous vein grafts intervention

BACKGROUND

Despite the use of embolic protection devices, no-reflow can still occur during saphenous vein grafts (SVGs) intervention. High-dose intracoronary adenosine infusion preconditions the myocardium, improves coronary flow, and prevents no-reflow. The role of high-dose intragraft adenosine infusion on protection of microvascular function and prevention of no-reflow has not been investigated

OBJECTIVES

We investigated the cardioprotective effect of high-dose intragraft adenosine infusion, compared with placebo, on microvascular function and prevention of no-reflow during SVGs intervention.

METHODS

We randomized 22 patients with SVGs stenoses to receive either a 10-min intragraft adenosine infusion (200 μg/min; total dose = 2,000 μg) or normal saline prior to stenting. Average peak velocity (APV), coronary flow velocity reserve (CVR), thrombolysis in myocardial infarction (TIMI) frame count (TFC), TIMI myocardial perfusion grade (TMPG), and the rate of no-reflow were compared between the two groups before adenosine or saline infusions and after stenting

RESULTS

After stenting, hyperemic APV, CVR, and TMPG were significantly higher in the adenosine-treated group than in the control group (60 ± 18 vs. 35 ± 10 cm/sec; 2.6 ± 0.54 vs. 1.8 ± 0.47; and 2.8 ± 0.90 vs. 2.1 ± 0.80, respectively; P < 0.05. TFC was significantly lower in the adenosine-treated group than in the control group (14 ± 3.0 vs. 26 ± 13; P < 0.05). In the control group, four patients (36%) developed no-reflow compared to none in the adenosine-treated patient; P < 0.05 CONCLUSIONS: This study provides the first evidence that high-dose intragraft adenosine infusion compared with placebo protects microvascular function and prevents no-reflow during SVGs intervention.

Endothelial dysfunction over the course of coronary artery disease

The vascular endothelium regulates blood flow in response to physiological needs. Endothelial dysfunction is closely related to atherosclerosis and its risk factors, and it constitutes an intermediate step on the progression to adverse events throughout the natural history of coronary artery disease (CAD), often affecting clinical outcomes. Understanding the relation of endothelial function with CAD provides an important pathophysiological insight, which can be useful both in clinical and research management. In this review, we summarize the current knowledge on endothelial dysfunction and its prognostic influence throughout the natural history of CAD, from early atherosclerosis to post-transplant management.

Effects of intravenous diltiazem in a rat model of experimental coronary thrombotic microembolism

The aim of this study was to assess the feasibility of evaluating the therapeutic effects of intravenous diltiazem in a newly established rat model of coronary thrombotic micro-embolism (CME). CME was induced by injecting 0.199 ml saline containing 5 mg of automicrothrombotic particulates (∼10 μm) into the aorta of Sprague Dawley rats. The injection was carried out over 10 sec using a tuberculin syringe with a 28-gauge needle. The CME model rats were randomly divided into untreated (CME, n=38) and diltiazem-treated (CME+DIL, n=38) groups. Diltiazem (1 mg/ml, 50 μg/min/kg) was intravenously injected using an infusion pump through the tail vein for 175 min, 5 min following the injection of the automicrothrombotic particulates. Hemodynamic measurements, echocardiography and pathohistological examinations were performed at various time-points (3 h, 24 h and 7 and 28 days) postoperatively. Arteriolar thrombosis, multifocal myocardial necrosis, inflammatory cell infiltration with markedly increased myocardial tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) expression, reduced left ventricular (LV) systolic function and increased plasma von Willebrand factor (vWF), endothelin-1 (ET-1) and serum c-troponin I (c-TnI) levels (indicating vascular endothelial injury and myocardial necrosis) were observed in the CME model rats. These pathological responses in CME rats were partly attenuated by intravenous diltiazem treatment. The present CME model is suitable for evaluating the therapeutic effects of intravenous diltiazem; intravenous diltiazem treatment significantly improved cardiac function through alleviating inflammatory responses and microvascular thrombotic injury in this rat model of CME.

Coronary aspirate TNFα reflects saphenous vein bypass graft restenosis risk in diabetic patients

BACKGROUND

Patients with diabetes mellitus (DM) have an increased risk for periprocedural complications and adverse cardiac events after percutaneous coronary intervention. We addressed the potential for coronary microvascular obstruction and restenosis in patients with and without DM undergoing stenting for saphenous vein bypass graft (SVG) stenosis under protection with a distal occlusion/aspiration device.

METHODS

SVG plaque volume and composition were analyzed using intravascular ultrasound before stent implantation. Percent diameter stenosis was determined from quantitative coronary angiography before, immediately after and 6 months after stent implantation. Coronary aspirate was retrieved during stent implantation and divided into particulate debris and plasma. Total calcium, several vasoconstrictors, and tumor necrosis factor (TNF)α in particulate debris and coronary aspirate plasma were determined.

RESULTS

Patients with and without DM had similar plaque volume, but larger necrotic core and greater particulate debris release in patients with than without DM (20.3±2.7 vs. 12.7±2.6% and 143.9±19.3 vs. 75.1±10.4 mg, P<0.05). The TNFα concentration in particulate debris and coronary aspirate plasma was higher in patients with than without DM (15.9±6.6 vs. 5.1±2.4 pmol/mg and 2.2±0.7 vs. 1.1±0.2 pmol/L, P<0.05), whereas total calcium and vasoconstrictors were not different. Patients with DM had a greater percent diameter stenosis 6 months after stent implantation than those without DM (22.17±5.22 vs. 6.34±1.11%, P<0.05). The increase in TNFα immediately after stent implantation correlated with restenosis 6 months later (r=0.69, P<0.05).

CONCLUSION

In diabetics, particulate debris and coronary aspirate plasma contained more TNFα, which might reflect the activity of the underlying atherosclerotic process.

TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov/ct2/results?term=NCT01430884; unique identifier: NCT01430884.

Saphenous vein aorto-coronary graft atherosclerosis in patients with chronic kidney disease: more plaque calcification and necrosis, but less vasoconstrictor potential

Atherosclerotic coronary arteries are more calcified in patients with than without chronic kidney disease (CKD). We addressed the potential for coronary microvascular obstruction in patients with and without CKD during stenting for saphenous vein aorto-coronary graft (SVG) stenosis under protection with a distal occlusion/aspiration device. In patients with and without CKD (n = 20/20), SVG plaque composition was analyzed from virtual histology using intravascular ultrasound analysis before stent implantation. There was more dense calcium and more necrotic core in patients with than without CKD (14 ± 3 vs. 3 ± 1 % and 21 ± 3 vs. 12 ± 2 % of plaque volume, respectively). Coronary aspirate was retrieved during stent implantation and divided into particulate debris and plasma. Patients with CKD had more particulate debris and calcium release than patients without CKD. In contrast, the release of serotonin was less in patients with than without CKD (0.4 ± 0.1 vs. 1.2 ± 0.3 μmol/L), whereas that of catecholamines, endothelin, tissue factor, thromboxane, tumor necrosis factor α, and C reactive protein was not significantly different. Confirming the biochemical results, aspirate plasma from patients with CKD induced less vasoconstriction of rat mesenteric arteries than that from patients without CKD (with endothelium (+E), 26 ± 7 %; without endothelium (-E): 28 ± 7 % vs. +E, 68 ± 12 %; -E: 95 ± 16 % of maximum KCl-induced vasoconstriction). Graft atherosclerosis of patients with CKD is more degenerated and releases more particulate debris and calcium, but the aspirate has surprisingly less serotonin and vasoconstrictor potential.

A review of troponins in ischemic heart disease and other conditions

Measuring cardiac troponin (cTn) I and T levels is currently considered to be a cornerstone for making the diagnosis of acute coronary syndrome (ACS).Based on current literature, cTnI and cTnT are known to be very sensitive and specific for myocardial damage, regardless of the underlying cause. Lately, it has been found that cTns can be elevated and reflect worse prognoses in many situations where ACS is excluded. Such information can affect the validity of cTns as markers for ACS without classic symptoms. This may call for a revision of the troponin cutoff values to make a diagnosis of ACS. Furthermore, it opens a new field of study to determine appropriate management of patients with elevated cTn levels in whom ACS has been excluded.

Coronary microvascular dysfunction in the clinical setting: from mystery to reality

Far more extensive than the epicardial coronary vasculature that can be visualized angiographically is the coronary microcirculation, which foregoes routine imaging. Probably due to the lack of techniques able to provide tangible evidence of its crucial role, the clinical importance of coronary microvascular dysfunction is not fully appreciated. However, evidence gathered over the last several decades indicates that both functional and structural abnormalities of the coronary microvasculature can lead to myocardial ischaemia, often comparable with that caused by obstructive coronary artery disease. Indeed, a marked increase in coronary microvascular resistance can impair coronary blood flow and trigger angina pectoris, ischaemic ECG shifts, and myocardial perfusion defects, and lead to left ventricular dysfunction in patients who otherwise have patent epicardial coronary arteries. This condition--often referred to as 'chest pain with normal coronary arteries' or 'cardiac syndrome X'--encompasses several pathogenic mechanisms involving the coronary microcirculation. Of importance, coronary microvascular dysfunction can occur in conjunction with several other cardiac disease processes. In this article, we review the pathogenic mechanisms leading to coronary microvascular dysfunction and its diagnostic assessment, as well as the different clinical presentations and prognostic implications of microvascular angina. As such, this review aims to remove at least some of the mystery surrounding the notion of coronary microvascular dysfunction and to show why it represents a true clinical entity.

Detection of coronary microembolization by Doppler ultrasound in patients with stable angina pectoris during percutaneous coronary interventions under an adjunctive antithrombotic therapy with abciximab: design and rationale of the High Intensity Transient Signals ReoPro (HITS-RP) study

Background

Embolization of atherosclerotic debris from the rupture of a vulnerable atherosclerotic plaque occurs iatrogenically during percutaneous coronary interventions (PCI) and can induce myocardial necrosis. These microembolizations are detected as high intensity transient signals (HITS) using intracoronary Doppler technology.

Presentation of the hypothesis

In the presented study we will test if abciximab (ReoPro®) infusion reduces high intensity transient signals in patients with stable angina pectoris undergoing PCI in comparison to standard therapy alone.

Testing the hypothesis

The High Intensity Transient Signals ReoPro® (HITS-RP) study will enroll 60 patients. It is a prospective, single center, randomized, double-blinded, controlled trial. The study is designed to compare the efficacy of intravenous abciximab administration for reduction of microembolization during elective PCI. Patients will be randomized in a 1:1 fashion to abciximab or placebo infusion. The primary end point of the HITS-RP-Study is the number of HITS during PCI measured by intracoronary Doppler wire. Secondary endpoints are bleeding complications, elevation of cardiac biomarkers or ECG changes after percutaneous coronary interventions, changes in coronary flow velocity reserve, hs-CRP elevation, any major adverse cardio-vascular event during one month follow-up.

Implications of the hypothesis

The HITS-RP-Study addresses important questions regarding the efficacy of intravenous abciximab administration in reducing microembolization and periprocedural complications in stable angina pectoris patients undergoing PCI.

Trial registration

The trial is registered under http://www.drks-neu.uniklinik-freiburg.de/drks_web/:DRKS00000603.

Changes in left ventricular ejection fraction and coronary flow reserve after coronary microembolization

INTRODUCTION

Although coronary microembolization (CME) is a frequent phenomenon in patients undergoing percutaneous coronary intervention, few data are available on the changes in left ventricular ejection fraction (LVEF) and coronary flow reserve (CFR) after CME.

MATERIAL AND METHODS

In this study, six miniature swine of either sex (body weight 21-25 kg) were used to prepare a CME model. After coronary angiography, 1.2 × 10(5) microspheres (42 µm) were selectively infused into the left anterior descending artery via an infusion catheter. Left ventricular ejection fraction was evaluated using transthoracic echocardiography; myocardial blood flow was measured using coloured microspheres; and CFR and coronary pressure were measured using Doppler and a pressure wire.

RESULTS

Left ventricular ejection fraction was 0.77 ±0.08 at baseline, 0.69 ±0.08 at 2 h, 0.68 ±0.08 at 6 h, and 0.76 ±0.06 at 1 week (2 h vs. baseline p < 0.05; 6 h vs. baseline p < 0.01). After CME, left ventricular end systolic volume (LVESV) and end diastolic volume (LVEDV) were significant larger 1 week later (p < 0.01 for both), while CFR was significantly reduced at 6 h (1.24 ±0.10 at 6 h vs. 1.77 ±0.30 at baseline, p < 0.01) and myocardial blood flow remained unchanged. Serum ET-1 level was significantly higher only at 6 h after CME (6 h vs. baseline p < 0.05).

CONCLUSIONS

Reduction of CFR and LVEF is significant at 6 h after CME and recovers 1 week later with left ventricular dilation.

Efficacy of dual antiplatelet therapy combined with Naoxintong capsules [see text] following coronary microembolization induced by homologous microthrombi in rats

OBJECTIVE

To evaluate the effificacy of dual antiplatelet therapy combined with Naoxintong Capsule ([see text], NXTC) in a rat model of coronary microembolization (CME).

METHODS

A total of 95 rats were randomly divided into 6 groups: control, sham-operation, CME model, NXTC, dual antiplatelet (clopidogrel and aspirin) intervention (DA), and NXTC combined with DA (NDA) groups. The complete data in 69 rats were obtained. The number of CME, myocardial apoptosis rate, bleeding time, clotting time, and adensosine diphosphate (ADP)-induced platelet aggregation were assessed.

RESULTS

Compared with the CME group, the number of CME and myocardial apoptosis rates were signifificantly decreased in the NXTC, DA, and NDA groups (P <0.01). Compared with other intervention groups, the number of CME and myocardial apoptosis rates were the least in the NDA group (P <0.01), and the incidence of surgical bleeding was the highest in the DA group (P <0.01). Compared with the CME group, ADP-induced maximum platelet aggregation rate was significantly inhibited in the NXTC, DA, and NDA groups (P <0.01), both bleeding time and clotting time were signifificantly increased in the NXTC, DA, and NDA groups (P <0.01), while the above parameters were the highest in the DA group (P <0.05).

CONCLUSION

The combination therapy of NXTC and DA enhanced the anti-CME effect of either therapy alone and reduced the risk of the DA therapy-associated bleeding, demonstrating an improved benefifit/ risk ratio in the rat model of CME.

Microvascular dysfunction in the spectrum of coronary instability

The term "coronary instability" commonly refers to the sequence of events that lead from plaque erosion or rupture to the occurrence of acute coronary syndromes (ACS). However, evidence indicates that coronary microvascular dysfunction plays a relevant pathophysiologic and prognostic role in the setting of ACS, both in ST-segment elevation myocardial infarction and in non-ST-segment elevation ACS. Our group have recently demonstrated that Tako-Tsubo syndrome, which clinically mimics ACS, is sustained by a common pathophysiologic mechanism represented by reversible coronary microvascular dysfunction. Given this evidence, we propose a reappraisal of the concept of coronary instability, extending this notion from the dramatic event represented by plaque erosion or rupture to a more diffuse process that can acutely affect each segment of the coronary circulation.

Role of inflammation in the regulation of coronary blood flow in ischemia and reperfusion: mechanisms and therapeutic implications

A multitude of factors, including increased coronary vascular resistance and dysregulated coronary microcirculatory function, contribute to the impairment of coronary blood flow (CBF) regulation and the pathogenesis of myocardial ischemia/reperfusion (I/R) injury. CBF is primarily determined by coronary vascular resistance, which is affected by the balance between various vasodilators and vasoconstrictors. Myocardial I/R causes reduced production of endogenous vasodilators, such as nitric oxide (NO), leaving unopposed vasoconstriction that is caused mainly by continued presence of endothelin-1 (ET-1) and serotonin (5-HT); this imbalance in turn enhances vascular tone, triggers inflammatory response, decreases CBF and exacerbates reperfusion injury. Various inflammatory cytokines participate in the regulation of coronary vasomotor function by affecting the balance between vasodilators and vasoconstrictors. In addition to the enhanced coronary vasoconstriction, coronary microembolization, inflammatory cell infiltration and post-ischemic hyperpermeability contribute to the impairment of coronary microcirculatory function and myocardial perfusion during I/R. Ongoing research examining the role of inflammation in the regulation of CBF and coronary microcirculatory function in myocardial I/R is expected to yield new insights that will lead to therapies for ameliorating the vascular inflammatory response in coronary artery diseases (CADs) in the clinical setting. This article is part of a Special Issue entitled "Coronary Blood Flow".

Subtle myocardial damage associated with diagnostic coronary angiography alone

AIMS

To evaluate the frequency, predictors and prognostic significance of elevation in cardiac troponin I (cTnI) after coronary angiography (CAG).

METHODS AND RESULTS

A series of 296 consecutive patients with normal pre-procedural cTnI levels and undergoing elective CAG at our centre were prospectively analysed. Positive cTnI elevation was defined as >0.06 ng/ml. Positive cTnI elevation was observed in 44 patients (14.8%), but CK-MB was elevated in only four patients (1.3%) after the procedure. The risk of cTnI elevation was independently associated with left ventricular hypertrophy (odds ratio [OR] 5.52; 95% confidence interval [CI], 2.54 to 12.02; P<0.001), inexperienced operator (OR 10.83; 95% CI, 2.47 to 47.43; P=0.002) and the amount of contrast agent (OR 1.12; 95% CI, 1.03 to 1.23; P=0.009 for each 10 ml increase), whereas it was not associated with the severity of coronary artery disease. At one year, however, postprocedural elevation of cTnI was not associated with an increased risk of death (2.3% vs. 0.8%, P=0.384) or myocardial infarction (2.3% vs. 2.0%, P=0.623).

CONCLUSIONS

A minor elevation of cTnI is observed commonly after CAG, which might be associated with left ventricular hypertrophy, operator's experience and the amount of contrast used; however, it does not influence 1-year events rates.

Microvascular obstruction after percutaneous coronary intervention

Successful revascularization of the epicardial coronary artery can be achieved in over 90% of percutaneous coronary intervention (PCI) procedures. However, postprocedural microvascular obstruction, despite the presence of normal epicardial flow, remains an important limitation which substantially reduces the beneficial effects of PCI. In this review article, a number of different methods available to diagnose microvascular obstruction after PCI are outlined. We also discussed the various pharmacological and mechanical strategies to reduce the occurrence of microvascular obstruction. In this regard, pretreatment with antiplatelet therapy remains crucial. In urgent PCI for acute myocardial infarction, available data suggest that manual thrombus aspiration device is beneficial in reducing the occurrence of procedure-related microvascular obstruction and possibly improve long-term clinical outcomes.

Selective endothelin A-receptor blockade attenuates coronary microvascular dysfunction after coronary stenting in patients with type 2 diabetes

BACKGROUND

Endothelin-1 may be involved in the development of diabetic microangiopathy. We studied the effect of endothelin-1 blockade on myocardial microcirculation during coronary stenting.

PATIENTS AND METHODS

Patients with type 2 diabetes and stable coronary artery disease undergoing elective percutaneous coronary intervention (PCI) were randomized to bolus dose of 500 mg bosentan (n = 4), a dual endothelin receptor blocker, or intracoronary administration of 0.03 mmol BQ123 (n = 6), a selective endothelin A-receptor blocker, or placebo (n = 5), respectively. Coronary flow reserve (CFR) was measured immediately post-PCI. CFR was also measured in five nondiabetic controls post-coronary stenting.

RESULTS

Patients in the placebo group had (P < 0.05) lower values of CFR (2.3 +/- 1.2) as compared to those who received endothelin blockade (n = 10; 3.1 +/- 0.7) and nondiabetic controls (4.9 +/- 2.3). Patients who received BQ123 showed significantly higher CFR (3.3 +/- 0.5; P < 0.05) as compared to those on placebo. Nondiabetic patients had significantly higher CFR as compared to patients with diabetes (4.9 +/- 2.3 and 2.8 +/- 1.0, respectively; P < 0.05).

CONCLUSION

Coronary microvascular dysfunction is present during coronary stenting in patients with type 2 diabetes and may be reversed by selective endothelin A-receptor blockade. Targeting endothelin system may be of importance in protecting the myocardium against ischemic events during elective PCI in type 2 diabetic patients.

Prognostic value of megatroponinemia after myocardial infarction

PURPOSE

The purpose of this study is to investigate the prognostic value of megatroponinemia (troponins >100 ng/mL), as a predictor of major adverse cardiac events such as recurrent angina, myocardial infarction, and death in patients presenting with acute myocardial infarction.

METHODS

Over a period of 2 years, we identified 27 patients admitted with acute myocardial infarction and troponin I values >100 ng/mL. These patients were followed-up for the short term during their hospitalization as well as for an intermediate term of 18+/-14 months after their initial presentation with acute myocardial infarction for major adverse cardiac events including recurrent angina, myocardial infarction, and death.

RESULTS

Of the 27 patients, one died 5 days after myocardial infarction and 26 were discharged home in stable condition, with few requiring timely intervention. Six patients were lost to follow-up. Five patients died during follow-up, 4 from recurrent myocardial infarction and 1 died from metastatic renal cell carcinoma. Twelve patients had non-fatal myocardial infarction, with 10 being acute ST elevation; 3 patients had recurrent angina.

CONCLUSION

Patients presenting with an acute myocardial infarction and troponins >100 ng/mL have continued incremental risk of excessive major adverse cardiac events during short and intermediate follow-up period.

Vascular control in humans: focus on the coronary microcirculation

Myocardial perfusion is regulated by a variety of factors that influence arteriolar vasomotor tone. An understanding of the physiological and pathophysiological factors that modulate coronary blood flow provides the basis for the judicious use of medications for the treatment of patients with coronary artery disease. Vasomotor properties of the coronary circulation vary among species. This review highlights the results of recent studies that examine the mechanisms by which the human coronary microcirculation is regulated in normal and disease states, focusing on diabetes. Multiple pathways responsible for myogenic constriction and flow-mediated dilation in human coronary arterioles are addressed. The important role of endothelium-derived hyperpolarizing factors, their interactions in mediating dilation, as well as speculation regarding the clinical significance are emphasized. Unique properties of coronary arterioles in human vs. other species are discussed.

Myocardial microinfarction after coronary microembolization in swine: MR imaging characterization

PURPOSE

To use first-pass perfusion and delayed-enhanced (DE) magnetic resonance (MR) imaging for the detection of the early effects of coronary microembolization on myocardial perfusion and viability.

MATERIALS AND METHODS

Approval was obtained from the institutional committee on animal research. A hybrid x-ray and MR imaging system was used to guide the endovascular catheter and quantify the left anterior descending coronary artery (LAD) perfusion territory before microembolization and ischemic myocardium and microinfarction after microembolization. The embolic agent was selectively delivered in the LAD in six pigs. First-pass perfusion MR imaging was performed 1 hour and 1 week after microembolization. Microinfarction was measured on DE MR images in beating and nonbeating hearts (high-spatial-resolution sequence) by using extracellular and blood pool MR contrast media and after death. The Wilcoxon signed rank test and correlation analysis were used.

RESULTS

The LAD perfusion territory was 35% of left ventricular (LV) mass +/- 2 (standard error of the mean). Microembolization caused perfusion deficit in 15.7% of LV mass +/- 2.6 compared with that of LAD territory (P = .03). At 1 week, perfusion parameters improved and the extent of hypoperfused territory declined (4.6% of LV mass +/- 1.4, P = .03). Microinfarction size expanded from 1.4% of LV mass +/- 0.2 at 1 hour to 7.5% of LV mass +/- 1.2 at 1 week. In nonbeating hearts and at triphenyltetrazolium chloride staining at 1 week, microinfarction size was 7.6% of LV mass +/- 1.4 and 7.2% of LV mass +/- 1.5, respectively. There was no correlation between the ejection fraction and the extents of microinfarction or hypoperfused territory. Histopathologic findings confirmed the presence of patchy microinfarction.

CONCLUSION

Coronary microembolization caused persistent decline in myocardial perfusion at first-pass perfusion imaging. DE MR imaging has the potential to help reliably quantify subacute microinfarction. The magnitude of LV dysfunction is not related to the extents of microinfarction or hypoperfused territory.

How much myocardial damage is necessary to enable detection of focal late gadolinium enhancement at cardiac MR imaging?

PURPOSE

To assess the visibility of small myocardial lesions at magnetic resonance (MR) imaging and to estimate how much myocardial damage is necessary to enable detection of late gadolinium enhancement (LGE) in vivo.

MATERIALS AND METHODS

The study was approved by the local bioethics committee. Coronary microembolization was performed by injecting 300,000 microspheres into the distal portion of the left anterior descending artery in 18 anesthetized minipigs to create multifocal areas of myocardial damage. In vivo MR imaging was performed a mean of 6 hours after microembolization by using an inversion-recovery spoiled gradient-echo sequence (repetition time msec/echo time msec, 8/4; inversion time, 240-320 msec; flip angle, 20 degrees; spatial resolution, 1.3 x 1.7 x 5.0 mm(3)) after injection of 0.2 mmol gadopentetate dimeglumine per kilogram of body weight. High-spatial-resolution imaging of the explanted heart was performed by using the same sequence with a higher spatial resolution (0.5 x 0.5 x 2.0 mm(3)). Imaging results were verified with histologic examination. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of in vivo and ex vivo images were calculated, and a t test was used to analyze observed differences.

RESULTS

Multifocal myocardial damage was successfully induced in all animals. Areas of LGE with low SNR (mean, 36.3 +/- 29.4 [standard deviation]) and CNR (23.7 +/- 19.8) were observed in vivo in 12 (67%) of 18 animals, whereas ex vivo imaging revealed spotted to streaky areas of LGE with higher SNR (91.4 +/- 27.8, P < .0001) and CNR (72.1 +/- 25.4, P < .0001) among normal-appearing myocardium in all cases (100%). Focal myocardial lesions exceeding 5% of myocardium per slice at histologic examination were detected in vivo with a sensitivity of 83%.

CONCLUSION

Focal myocardial damage exceeding 5% of myocardium within the region of interest seems to be necessary for detection of LGE in vivo in an experimental model of coronary microembolization.