Myocardial Viability Assessment Before Surgical Revascularization in Ischemic Cardiomyopathy: JACC Review Topic of the Week.

Ischemic cardiomyopathy results from the combination of scar with fibrosis replacement and areas of dysfunctional but viable myocardium that may improve contractile function with revascularization. Observational studies reported that only patients with substantial amounts of myocardial viability had better outcomes following surgical revascularization. Accordingly, dedicated noninvasive techniques have evolved to quantify viable myocardium with the objective of selecting patients for this form of therapeutic intervention. However, prospective trials have not confirmed the interaction between myocardial viability and the treatment effect of revascularization. Furthermore, recent observations indicate that recovery of left ventricular function is not the principal mechanism by which surgical revascularization improves prognosis. In this paper, the authors describe a more contemporary application of viability testing that is founded on the alternative concept that the main goal of surgical revascularization is to prevent further damage by protecting the residual viable myocardium from subsequent acute coronary events.

Functional Assessment of Myocardial Bridging With Conventional and Diastolic Fractional Flow Reserve: Vasodilator Versus Inotropic Provocation.

Background Functional assessment of myocardial bridging (MB) remains clinically challenging because of the dynamic nature of the extravascular coronary compression with a certain degree of intraluminal coronary reduction. The aim of our study was to assess performance and diagnostic value of diastolic-fractional flow reserve (d-FFR) during dobutamine provocation versus conventional-FFR during adenosine provocation with exercise-induced myocardial ischemia as reference. Methods and Results This prospective study includes 60 symptomatic patients (45 men, mean age 57±9 years) with MB on the left anterior descending artery and systolic compression ≥50% diameter stenosis. Patients were evaluated by exercise stress-echocardiography test, and both conventional-FFR and d-FFR in the distal segment of left anterior descending artery during intravenous infusion of adenosine (140 µg/kg per minute) and dobutamine (10-50 µg/kg per minute), separately. Exercise-stress-echocardiography test was positive for myocardial ischemia in 19/60 patients (32%). Conventional-FFR during adenosine and peak dobutamine had similar values (0.84±0.04 versus 0.84±0.06, P=0.852), but d-FFR during peak dobutamine was significantly lower than d-FFR during adenosine (0.76±0.08 versus 0.79±0.08, P=0.018). Diastolic-FFR during peak dobutamine was significantly lower in the exercise-stress-echocardiography test -positive group compared with the exercise- stress-echocardiography test -negative group (0.70±0.07 versus 0.79±0.06, P<0.001), but not during adenosine (0.79±0.07 versus 0.78±0.09, P=0.613). Among physiological indices, d-FFR during peak dobutamine was the only independent predictor of functionally significant MB (odds ratio, 0.870; 95% CI, 0.767-0.986, P=0.03). Receiver-operating characteristics curve analysis identifies the optimal d-FFR during peak dobutamine cut-off ≤0.76 (area under curve, 0.927; 95% CI, 0.833-1.000; P<0.001) with a sensitivity, specificity, and positive and negative predictive value of 95%, 95%, 90%, and 98%, respectively, for identifying MB associated with stress-induced ischemia. Conclusions Diastolic-FFR, but not conventional-FFR, during inotropic stimulation with high-dose dobutamine, in comparison to vasodilatation with adenosine, provides more reliable functional significance of MB in relation to stress-induced myocardial ischemia.

SARS-CoV 2 Infection (Covid-19) and Cardiovascular Disease in Africa: Health Care and Socio-Economic Implications.

The current pandemic of SARS-COV 2 infection (Covid-19) is challenging health systems and communities worldwide. At the individual level, the main biological system involved in Covid-19 is the respiratory system. Respiratory complications range from mild flu-like illness symptoms to a fatal respiratory distress syndrome or a severe and fulminant pneumonia. Critically, the presence of a pre-existing cardiovascular disease or its risk factors, such as hypertension or type II diabetes mellitus, increases the chance of having severe complications (including death) if infected by the virus. In addition, the infection can worsen an existing cardiovascular disease or precipitate new ones. This paper presents a contemporary review of cardiovascular complications of Covid-19. It also specifically examines the impact of the disease on those already vulnerable and on the poorly resourced health systems of Africa as well as the potential broader consequences on the socio-economic health of this region.

Functional assessment of myocardial ischaemia by intracoronary ECG.

INTRODUCTION: In patients with chronic coronary syndrome, percutaneous coronary intervention targets haemodynamically significant stenoses, that is, those thought to cause ischaemia. Intracoronary ECG (icECG) detects ischaemia directly where it occurs. Thus, the goal of this study was to test the accuracy of icECG during pharmacological inotropic stress to determine functional coronary lesion severity in comparison to the structural parameter of quantitative angiographic per cent diameter stenosis (%S), as well as to the haemodynamic indices of fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR). METHOD: The primary study endpoint of this prospective trial was the maximal change in icECG ST-segment shift during pharmacological inotropic stress induced by dobutamine plus atropine obtained within 1 min after reaching maximal heart rate(=220 - age). IcECG was acquired by attaching an alligator clamp to the angioplasty guidewire positioned downstream of the stenosis. For the pressure-derived stenosis severity ratios, coronary perfusion pressure and simultaneous aortic pressure were continuously recorded. RESULTS: There was a direct linear relation between icECG ST-segment shift and %S: icECG=-0.8+0.03*%S (r2=0.164; p<0.0001). There were inverse linear correlations between FFR and %S: FFR=1.1-6.1*10-3*%S (r2=0.494; p<0.0001), and between iFR and %S: iFR=1.27-8.6*10-3*%S (r2=0.461; p<0.0001). Using a %S-threshold of ≥50% as the reference for structural stenosis relevance, receiver operating characteristics-analysis of absolute icECG ST-segment shift during hyperemia showed an area under the curve (AUC) of 0.678±0.054 (p=0.002; sensitivity=85%, specificity=50% at 0.34 mV). AUC for FFR was 0.854±0.037 (p<0.0001; sensitivity=64%, specificity=96% at 0.78), and for iFR it was 0.816±0.043 (p<0.0001;sensitivity=62%, specificity=96% at 0.83). CONCLUSIONS: Hyperaemic icECG ST-segment shift detects structurally relevant coronary stenotic lesions with high sensitivity, while they are identified highly specific by FFR and iFR.

Incremental value of myocardial wall motion and thickening to perfusion alone by gated SPECT myocardial perfusion imaging for viability assessment in patients with ischemic heart failure.

PURPOSE: The objective of this study was to assess the incremental value of myocardial wall motion and thickening compared with perfusion alone obtained from gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) in diagnosing myocardial viability in patients with ischemic heart failure. METHODS: Eighty-three consecutive patients with ischemic heart failure who underwent both 99mTc-MIBI gated SPECT MPI and 18F-FDG positron emission tomography (PET) myocardial metabolic imaging were retrospectively enrolled. SPECT/PET myocardial viability was defined as the reference standard. Segmental myocardial perfusion, wall motion, and thickening were measured by an automated algorithm from gated SPECT MPI. Univariate and stepwise multivariate analysis were conducted to establish an optimal multivariate model for predicting hibernating myocardium and scar. RESULTS: Among the 1411 segments evaluated, 774 segments had normal perfusion and 637 segments had decreased perfusion. The latter were classified by 18F-FDG PET into 338 hibernating segments and 299 scarred segments. The multivariate regression analysis showed that the model that combined myocardial perfusion uptake with wall motion and thickening scores had the optimal predictive efficiency to distinguish hibernating myocardium from scar in the segments with decreased perfusion. The model had the largest C-statistic (0.753 vs 0.666, P < 0.0001), and the global chi-square was increased from 53.281 to 111.234 when compared with perfusion alone (P < 0.001). CONCLUSIONS: Assessment of myocardial wall motion and thickening in addition to conventional perfusion uptake in the segments with decreased perfusion enables better differentiation of hibernating myocardium from scar in patients with ischemic heart failure. Considering wide availability and high cost-effectiveness, regional myocardial function integrated with perfusion on gated SPECT MPI has great promise to become a clinical tool in the assessment of myocardial viability.

Clinical characteristics and outcomes of patients with severe left ventricular dysfunction undergoing cardiac MRI viability assessment prior to revascularization.

Coronary artery bypass grafting improves survival in patients with ischemic cardiomyopathy, however, these patients are at high risk for morbidity and mortality. The role of viability testing to guide revascularization in these patients is unclear. Cardiac magnetic resonance imaging (CMR) has not been studied adequately in this population despite being considered a reference standard for infarct imaging. We performed a multicenter retrospective analysis of patients (n = 154) with severe left ventricular systolic dysfunction [ejection fraction (EF) < 35%] on CMR who underwent CMR viability assessment prior to consideration for revascularization. Using the AHA16-segment model, percent total myocardial viability was determined depending on the degree of transmural scar thickness. Patients with or without revascularization had similar clinical characteristics and were prescribed similar medical therapy. Overall, 43% of patients (n = 66) experienced an adverse event during the median 3 years follow up. For the composite outcome (death, myocardial infarction, heart failure hospitalization, stroke, ventricular tachycardia) patients receiving revascularization were less likely to experience an adverse event compared to those without revascularization (HR 0.53, 95% CI 0.33-0.86, p = 0.01). Patients with > 50% viability on CMR had a 47% reduction in composite events when undergoing revascularization opposed to medical therapy alone (HR 0.53, p = 0.02) whereas patients with a viability < 50% were 2.7 times more likely to experience an adverse event (p = 0.01). CMR viability assessment may be an important tool in the shared decision-making process when considering revascularization options in patients with severe ischemic cardiomyopathy.

Strain analysis using feature tracking cardiac magnetic resonance (FT-CMR) in the assessment of myocardial viability in chronic ischemic patients.

The purpose of this study is to test the capability of a commercially available feature tracking-cardiac magnetic resonance (FT-CMR) strain analysis software module in differentiating between viable and non-viable myocardium in chronic ischemic patients. Thirty chronic ischemic patients and 10 healthy volunteers were enrolled. Cine images were used for peak circumferential and radial strains quantification using dedicated FT-CMR software. Global strain was compared between patients and controls. In patients, segmental strain was compared in viable and non-viable myocardium determined by late gadolinium enhancement (LGE); and in segments with wall abnormalities. Among 480 myocardial segments analyzed in patients, 76 segments were non-viable on LGE. The mean left ventricular ejection fraction (LVEF) of the patients (87% males, mean age 55 ± 12 years) was 40 ± 12% vs. 61 ± 5% for the controls (80% males, mean age 39 ± 11 years). Peak global circumferential strain (GCS) and global radial strain (GRS) were significantly impaired in patients compared to controls (-13.89 ± 4.12% vs. -19.84 ± 1.47%), p < 0.001 and (23.11 ± 6.59% vs. 31.72 ± 5.52%), p = 0.001. Segmental circumferential strain (SCS) and segmental radial strain (SRS) were significantly impaired in non-viable compared to viable segments (-9.47 ± 7.26% vs. -14.72 ± 7.5%), p < 0.001 and (15.67 ± 12.11% vs. 24.51 ± 16.22%), p < 0.001. Cut-off points of -9.36% for the SCS (AUC = 0.7, 95% CI = 0.63-0.77) and 19.5% for the SRS (AUC = 0.67, 95%CI = 0.61-0.73) were attained above which the segment is considered viable.SCS was able to discriminate between normokinetic, hypokinetic and akinetic segments (mean = 27.6 ± 17.13%, 18.66 ± 12.88% and 15.24 ± 10.70% respectively, p < 0.001). Circumferential and radial segmental strain analysis by FT-CMR was able to discriminate between viable and non-viable segments of the myocardium defined by LGE and between normokinetic, hypokinetic and akinetic segments, using routinely acquired cine images, and thus can provide a more objective metric for risk stratification in chronic ischemic patients.

Coronary microvascular dysfunction in hypertrophic cardiomyopathy: Pathophysiology, assessment, and clinical impact.

Myocardial ischemia constitutes one of the most important pathophysiological features in hypertrophic cardiomyopathy. Chronic and recurrent myocardial ischemia leads to fibrosis, which may culminate in myocardial dysfunction. Since the direct visualization of coronary microcirculation in vivo is not possible, its function must be studied indirectly. Invasive and noninvasive techniques allow microcirculatory dysfunction to be evaluated, including echocardiography, magnetic resonance, positron emission tomography, and cardiac catheterization. Blunted myocardial blood flow and coronary flow reserve have been suggested to associate with unfavorable prognosis. Microcirculatory dysfunction may be one additional important parameter to take into account for risk stratification beyond the conventional risk factors.

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.

Borderline coronary lesion assessment with quantitative flow ratio and its relation to the instantaneous wave-free ratio.

PURPOSE: Quantitative flow ratio (QFR) is a recently developed image-based index for the assessment of borderline coronary artery disease. We sought to investigate a correlation between QFR and instantaneous wave-free ratio (iFR) for the assessment of intermediate coronary stenoses. MATERIALS AND METHODS: Patients with borderline coronary lesions (40-90% by visual assessment) undergoing iFR assessment were enrolled. QFR was derived from a modeled hyperemic flow velocity derived from angiography without adenosine-induced hyperemia. Pressure wire-derived iFR served as the reference. RESULTS: Values of QFR and iFR from 110 vessels with a mean percent diameter stenosis of 44.6 â€‹± â€‹12.0% were compared. Mean iFR was 0.90 â€‹± â€‹0.07 and 38 (34.5%) had iFR ≤0.89. Mean QFR was 0.81 â€‹± â€‹0.10 and 44 (40%) had QFR ≤0.80. A good agreement between QFR and iFR measurements was confirmed with a mean difference of 0.09 (95%CI -0.027 to 0.207) and intraclass correlation coefficient of 0.87 (95%CI 0.81-0.91). The overall diagnostic accuracy (AUC in ROC analysis) of QFR in detecting iFR ≤0.89 was 0.87 (95%CI 0.79-0.93; p â€‹< â€‹0.001). Regarding iFR ≤0.89, the optimal cutoff value of QFR was 0.79 with sensitivity, specificity, and accuracy of 76.3%, 83.3%, and 80.0%, respectively. A 100% sensitivity was observed for a QFR cutoff value of 0.88 and a 100% specificity for a QFR cutoff value of 0.69. CONCLUSIONS: Our study confirmed good QFR diagnostic performance and correlation with iFR for detecting the functional ischemia caused by intermediate lesions in coronary arteries. However, the pressure wire assessment with iFR might be warranted in 2/3 of patients after QFR assessment.

PET Perfusion and Flow Assessment: Tomorrows' Technology Today.

Quantitative myocardial perfusion PET/CT imaging is one of the most accurate tests for diagnosis and risk stratification of patients with suspected or known CAD. The test provides a comprehensive evaluation of patients with ischemic heart disease including quantitative assessments of regional myocardial perfusion, LV volumes and ejection fraction, calcified atherosclerotic burden, and myocardial blood flow and flow reserve (MFR). A normal stress myocardial blood flow and MFR (>2.0) has a very high negative predictive value and reliably excludes high-risk obstructive CAD. A global normal MFR (>2.0) identifies patients at consistently lower clinical risk. Conversely, a severely reduced MFR (<1.5) identifies patients at high clinical risk for adverse events regardless of whether this is due to obstructive CAD, microvascular dysfunction, or a combination of the 2. On the other hand, the delineation of atherosclerotic burden with either a formal quantitative coronary calcium score or by a semiquantitative assessment of the CT transmission scan is very helpful to guide the need for intensive preventive therapies. Recent evidence suggests that patients with angiographically obstructive CAD and a severe reduction in flow reserve (<1.6) may have a prognostic advantage from revascularization. This finding awaits confirmation by randomized clinical trials.

Clinical quantitative cardiac imaging for the assessment of myocardial ischaemia.

Cardiac imaging has a pivotal role in the prevention, diagnosis and treatment of ischaemic heart disease. SPECT is most commonly used for clinical myocardial perfusion imaging, whereas PET is the clinical reference standard for the quantification of myocardial perfusion. MRI does not involve exposure to ionizing radiation, similar to echocardiography, which can be performed at the bedside. CT perfusion imaging is not frequently used but CT offers coronary angiography data, and invasive catheter-based methods can measure coronary flow and pressure. Technical improvements to the quantification of pathophysiological parameters of myocardial ischaemia can be achieved. Clinical consensus recommendations on the appropriateness of each technique were derived following a European quantitative cardiac imaging meeting and using a real-time Delphi process. SPECT using new detectors allows the quantification of myocardial blood flow and is now also suited to patients with a high BMI. PET is well suited to patients with multivessel disease to confirm or exclude balanced ischaemia. MRI allows the evaluation of patients with complex disease who would benefit from imaging of function and fibrosis in addition to perfusion. Echocardiography remains the preferred technique for assessing ischaemia in bedside situations, whereas CT has the greatest value for combined quantification of stenosis and characterization of atherosclerosis in relation to myocardial ischaemia. In patients with a high probability of needing invasive treatment, invasive coronary flow and pressure measurement is well suited to guide treatment decisions. In this Consensus Statement, we summarize the strengths and weaknesses as well as the future technological potential of each imaging modality.

[Invasive functional assessment of coronary artery stenosis using fractional flow reserve]. / Valutazione funzionale invasiva delle stenosi coronariche mediante riserva frazionale di flusso coronarico.

The presence of myocardial ischemia significantly affects prognosis of patients with coronary artery disease. The fractional flow reserve (FFR) allows interventional cardiologists to evaluate whether an equivocal coronary artery stenosis is associated or not with myocardial ischemia, and therefore deserve to be properly treated. The present article has the purpose to provide the readers with an overview about the role of FFR in the diagnosis and management of coronary artery disease, as well as the potential related controversies. The coronary physiology on the basis of this tool is also provided together with all the procedural aspects useful in the catheterization laboratory. In addition, the landmark trials on the basis of the FFR application in different clinical settings and coronary anatomies will be described, together with the main improvements aiming at favoring a more extensive use of this invasive tool.

Semi-quantitative myocardial perfusion MRI in heart transplant recipients at rest: repeatability in healthy controls and assessment of cardiac allograft vasculopathy.

BACKGROUND: Cardiac Allograft Vasculopathy (CAV) is a major cause of chronic cardiac allograft failure. Invasive coronary angiography (ICA) and intravascular ultrasound (IVUS) are the current diagnostic methods. Myocardial perfusion MRI has become a promising non-invasive method to evaluate myocardial ischemia, but has not been thoroughly validated in CAV. Our objective was to assess the repeatability of myocardial rest-perfusion MRI in healthy volunteers and its feasibility in detecting CAV in transplant patients (Tx). METHODS: Twelve healthy volunteers and twenty transplant patients beyond the first year post- transplant underwent cardiac MRI at 1.5 T at rest including first-pass perfusion imaging in short axis (base, mid, apex) after injection of gadolinium. Volunteers underwent repeated cardiac MRI on different days (interval = 15.6 ± 2.4 days) to assess repeatability. Data analysis included semi-automatic contouring of endocardial and epicardial borders of the left ventricle (LV) and quantification of peak perfusion, time-to-peak (TTP) perfusion, and upslope of the perfusion curve. RESULTS: Between scans and re-scans in healthy volunteers, peak signal intensity, slope, and TTP demonstrated moderate agreement (ICC = 0.53, 0.48, and 0.59, respectively; all, p < .001). Peak signal intensity, slope, and TTP were moderately variable with COV values of 23%, 42%, and 35%, respectively. Peak perfusion was significantly reduced in CAV positive (n = 9 Tx patients) compared to CAV negative (n = 11 Tx patients) groups (90.7 ± 27.0 vs 139.5 ± 30.2, p < .001). CONCLUSION: Cardiac MRI is a moderately repeatable method for the semi-quantitative assessment of first-pass myocardial perfusion at rest. Semi-quantitative surrogate markers of LV perfusion could play a role in CAV detection.

Sex and Gender Differences in Ischemic Heart Disease: Endocrine Vascular Disease Approach (EVA) Study Design.

Improvements in ischemic heart disease (IHD) management have been unbalanced between sexes, with coronary microvascular dysfunction considered the likely underlying reason. The Endocrine Vascular disease Approach (EVA) is an observational study (Clinicaltrial.gov NCT02737982) aiming to assess sex and gender interactions between coronary circulation, sexual hormones, and platelet function. Consecutive patients with IHD undergoing coronary angiography will be recruited: (1) to assess sex and gender differences in angiographic reperfusion indexes; (2) to evaluate the effects of estrogen/androgen on sex-related differences in myocardial ischemia; (3) to investigate the platelet biology differences between men and women with IHD; (4) to verify sex- and gender-driven interplay between response to percutaneous coronary intervention, platelets, sex hormones, and myocardial damage at baseline and its impact on 12-month outcomes. The integration of sex and gender in this translational project on IHD will contribute to the identification of new targets for further innovative clinical interventions.

Optimizing the Assessment of Patient Clinical Risk at the Time of Cardiac Stress Testing.

Due to a marked temporal decline in inducible myocardial ischemia over recent decades, most diagnostic patients now referred for cardiac stress testing have nonischemic studies. Among nonischemic patients, however, long-term risk is heterogeneous and highly influenced by a variety of clinical parameters. Herein, we review 8 factors that can govern long-term clinical risk: coronary risk factor burden; patient symptoms; exercise capacity and exercise test responses; the need for pharmacologic stress testing; autonomic function; musculoskeletal status; subclinical atherosclerosis; and psychosocial risk. To capture the clinical benefit provided by both assessing myocardial ischemia and these additional parameters, the authors propose that a cardiac stress tests report have an additional component beyond statements as to the likelihood of obstructive coronary artery disease and/or magnitude of ischemia. This added component could be a comment section designed to make referring physicians aware of aspects of long-term risk that may influence clinical management and potentially lead to changes in the intensity of risk factor management, frequency of follow-up, need for further testing, or other management decisions. In this manner, the increasingly frequent normal stress test result might more commonly influence treatment recommendations and even patient behavior, thus leading to improvement in patient outcomes even in the setting of normal stress test results.

Optimal ECG Lead System for Exercise Assessment of Ischemic Heart Disease.

The diagnostic value of an ECG exercise test in diagnosis of ischemic heart disease (IHD) is limited. We investigated whether it is possible to develop a method for diagnosis of IHD which uses a low number of optimal ECG leads and has a higher diagnostic efficiency than conventional exercise ECG. This study was carried out on 43 patients. The 67-lead high-resolution ECG was recorded at rest and during exercise. The diagnostic value of ST segment depression (ΔST60) and T-wave morphology change (δT) determined in optimized ECG lead configurations was higher than for the standard 12-lead ECG. The best results were obtained for δT determined from 6 ECG electrode locations where sensitivity and specificity were 70% and 69% whereas for the standard exercise ECG were 63% and 62%, respectively. The small number of ECG leads used allows for easy hardware implementation of the methods for use in clinical settings.

Heart Rate Variability for Risk Assessment of Myocardial Ischemia in Patients Without Known Coronary Artery Disease: The HRV-DETECT (Heart Rate Variability for the Detection of Myocardial Ischemia) Study.

Background Detecting significant coronary artery disease (CAD) in the general population is complex and relies on combined assessment of traditional CAD risk factors and noninvasive testing. We hypothesized that a CAD-specific heart rate variability (HRV) algorithm can be used to improve detection of subclinical or early ischemia in patients without known CAD. Methods and Results Between 2014 and 2018 we prospectively enrolled 1043 patients with low to intermediate pretest probability for CAD who were screened for myocardial ischemia in tertiary medical centers in the United States and Israel. Patients underwent 1-hour Holter testing, with immediate HRV analysis using the HeartTrends DyDx algorithm, followed by exercise stress echocardiography (n=612) or exercise myocardial perfusion imaging (n=431). The threshold for low HRV was identified using receiver operating characteristic analysis based on sensitivity and specificity. The primary end point was the presence of myocardial ischemia detected by exercise stress echocardiography or exercise myocardial perfusion imaging. The mean age of patients was 61 years and 38% were women. Myocardial ischemia was detected in 66 (6.3%) patients. After adjustment for CAD risk factors and exercise stress testing results, low HRV was independently associated with a significant 2-fold increased likelihood for myocardial ischemia (odds ratio, 2.00; 95% CI, 1.41-2.89 [P=0.01]). Adding HRV to traditional CAD risk factors significantly improved the pretest probability for myocardial ischemia. Conclusions Our data from a large prospective international clinical study show that short-term HRV testing can be used as a novel digital-health modality for enhanced risk assessment in low- to intermediate-risk individuals without known CAD. Clinical Trial Registration URL: http://www.ClinicalTrials.gov. Unique identifiers: NCT01657006, NCT02201017).

Assessment of myocardial viability by PET.

PURPOSE OF REVIEW: Viability assessment has a key role in the management of patients with ischemic heart disease. Positron emission tomography (PET) is a unique modality that evaluates myocardial viability via assessing the tissues metabolic and perfusion properties. The mainstay of metabolic imaging relies on glucose metabolism using fluorodeoxyglucose, a radiolabeled glucose analog. Mismatch in perfusion metabolism data denotes hibernating myocardium with a high likelihood of functional recovery following revascularization. Matched absence or reduction in perfusion metabolism data represents scar with a low likelihood of functional recovery following revascularization. This review will focus on PET radiotracers and techniques used to assess myocardial viability. RECENT FINDINGS: Single-center studies have shown that patients with PET mismatch undergoing bypass grafting had improved survival compared with those on medical therapy. In addition to survival benefit, the patients who underwent PET-guided revascularization had significant improvement in angina and heart failure symptomology. Recent technological advancements in the field of PET-magnetic resonance (MR) opens a new frontier in the field of advanced imaging as it combines anatomical, functional, tissue characterization, and metabolic perfusion data obtained in one setting. The incremental value of PET/MRI is best established in diagnosing and monitoring disease activity in patients with cardiac sarcoidosis and occult malignancies, but more studies are needed to assess it value in viability assessment. SUMMARY: In conclusion, imaging myocardial viability by PET provides assessment of both physiological perfusion and myocardial tissue's metabolic activity to differentiate hibernating from scarred myocardium.

Assessment of Myocardial Ischemic Memory Using Three-Dimensional Speckle-Tracking Echocardiography: A Novel Integrated Analysis of Early Systolic Lengthening and Postsystolic Shortening.

BACKGROUND: Persistence of subtle abnormal myocardial deformation such as postsystolic shortening (PSS) after transient ischemia can be used to diagnose a history of myocardial ischemia (myocardial ischemic memory). Furthermore, early systolic lengthening (ESL) has recently attracted attention as another marker of myocardial ischemia. However, it is unclear whether the persistence of such abnormal deformation can be detected by three-dimensional (3D) speckle-tracking echocardiography, which has relatively low spatial and temporal resolution compared with two-dimensional echocardiography. The aim of this study was to evaluate the diagnostic accuracy of myocardial ischemic memory and its spatial extent using 3D speckle-tracking echocardiography. METHODS: The left circumflex coronary artery was occluded for 2 min, followed by reperfusion, in 33 dogs. Their hemodynamic and 3D echocardiographic data were chronologically acquired. Peak systolic strain, early systolic strain index as a parameter of ESL, postsystolic strain index as a parameter of PSS, and myocardial dysfunction index as a combined parameter of ESL and PSS were analyzed in all left ventricular segments. RESULTS: At the center of the risk area, early systolic strain index and postsystolic strain index significantly increased until 20 min after reperfusion compared with baseline, although peak systolic strain recovered by 20 min. Myocardial dysfunction index significantly increased for >20 min after reperfusion and allowed better diagnostic accuracy of ischemic memory than the other parameters. In the 147 risk segments, abnormal values of myocardial dysfunction index remained in 49 segments (33%) at 20 min after reperfusion, whereas abnormal peak systolic strain was observed in only 13 segments (9%). CONCLUSIONS: ESL and PSS persisted after transient ischemia and could be detected by 3D speckle-tracking echocardiography. Integrated analysis of ESL and PSS provided higher diagnostic accuracy of ischemic memory. This method may be useful for detecting transient ischemic insults in patients after the disappearance of anginal attack.