Maria Piera Petretta

Genetic Deletion of Uncoupling Protein 3 Exaggerates Apoptotic Cell Death in the Ischemic Heart Leading to Heart Failure

Background Uncoupling protein 3 (ucp3) is a member of the mitochondrial anion carrier superfamily of proteins uncoupling mitochondrial respiration. In this study, we investigated the effects of ucp3 genetic deletion on mitochondrial function and cell survival under low oxygen conditions in vitro and in vivo. Methods and Results To test the effects of ucp3 deletion in vitro, murine embryonic fibroblasts and adult cardiomyocytes were isolated from wild‐type (WT, n=67) and ucp3 knockout mice (ucp3−/−, n=70). To test the effects of ucp3 genetic deletion in vivo, myocardial infarction (MI) was induced by permanent coronary artery ligation in WT and ucp3−/− mice. Compared with WT, ucp3−/− murine embryonic fibroblasts and cardiomyocytes exhibited mitochondrial dysfunction and increased mitochondrial reactive oxygen species generation and apoptotic cell death under hypoxic conditions in vitro (terminal deoxynucleotidyl transferase‐dUTP nick end labeling–positive nuclei: WT hypoxia, 70.3±1.2%; ucp3−/− hypoxia, 85.3±0.9%; P<0.05). After MI, despite similar areas at risk in the 2 groups, ucp3−/− hearts demonstrated a significantly larger infarct size compared with WT (infarct area/area at risk: WT, 48.2±3.7%; ucp3−/−, 65.0±2.9%; P<0.05). Eight weeks after MI, cardiac function was significantly decreased in ucp3−/− mice compared with WT (fractional shortening: WT MI, 42.7±3.1%; ucp3−/− MI, 24.4±2.9; P<0.05), and this was associated with heightened apoptotic cell death (terminal deoxynucleotidyl transferase‐dUTP nick end labeling–positive nuclei: WT MI, 0.7±0.04%; ucp3−/− MI, 1.1±0.09%, P<0.05). Conclusions Our data indicate that ucp3 levels regulate reactive oxygen species levels and cell survival during hypoxia, modulating infarct size in the ischemic heart.

PET/CT Imaging in Mouse Models of Myocardial Ischemia

Different species have been used to reproduce myocardial infarction models but in the last years mice became the animals of choice for the analysis of several diseases, due to their short life cycle and the possibility of genetic manipulation. Many techniques are currently used for cardiovascular imaging in mice, including X-ray computed tomography (CT), high-resolution ultrasound, magnetic resonance imaging, and nuclear medicine procedures. Cardiac positron emission tomography (PET) allows to examine noninvasively, on a molecular level and with high sensitivity, regional changes in myocardial perfusion, metabolism, apoptosis, inflammation, and gene expression or to measure changes in anatomical and functional parameters in heart diseases. Currently hybrid PET/CT scanners for small laboratory animals are available, where CT adds high-resolution anatomical information. This paper reviews mouse models of myocardial infarction and discusses the applications of dedicated PET/CT systems technology, including animal preparation, anesthesia, radiotracers, and images postprocessing.

Effects of volume loading on strain rate and tissue Doppler velocity imaging in patients with idiopathic dilated cardiomyopathy.

BackgroundStrain rate is a promising echocardiographic technique which adds further information to that obtained with two-dimensional echocardiography and tissue Doppler imaging (TDI). The present study aimed to evaluate the effects of acute isotonic volume expansion on left ventricular function in patients with idiopathic dilated cardiomyopathy (DCM) utilizing TDI and strain rate measurements. MethodsTen patients with DCM and a left ventricular ejection fraction (LVEF) ≤ 40% underwent two-dimensional echocardiography during volume expansion (0.9% NaCl; 0.25 ml/kg/min for 120 min). Peak systolic tissue velocity and peak systolic strain rate were measured at baseline and at the end of volume loading. ResultsMean LVEF was 32 ± 9% at baseline and remained unchanged after volume loading. Similarly, peak systolic velocity was 2.21 cm/s at baseline and remained unchanged after volume expansion. By contrast, peak systolic strain rate significantly reduced from −1.08 ± 0.37/s to −0.76 ± 0.12/s (P < 0.05). ConclusionsIn patients with DCM, peak systolic strain rate significantly reduces with volume loading in the absence of change in LVEF or peak systolic velocities at TDI. Because strain rate is a relative load-independent index of systolic function, the reduction observed is probably related to the decrease in left ventricular systolic performance that follows volume loading in heart failure patients. Thus, peak systolic strain rate appears to be more useful than TDI velocities to evaluate left ventricular dynamics during volume loading in patients with depressed left ventricular function.

Molecular imaging of atherosclerosis in translational medicine

Functional characterization of atherosclerosis is a promising application of molecular imaging. Radionuclide-based techniques for molecular imaging in the large arteries (e.g. aorta and carotids), along with ultrasound and magnetic resonance imaging (MRI), have been studied both experimentally and in clinical studies. Technical factors including cardiac and respiratory motion, low spatial resolution and partial volume effects mean that noninvasive molecular imaging of atherosclerosis in the coronary arteries is not ready for prime time. Positron emission tomography imaging with fluorodeoxyglucose can measure vascular inflammation in the large arteries with high reproducibility, and signal change in response to anti-inflammatory therapy has been described. MRI has proven of value for quantifying carotid artery inflammation when iron oxide nanoparticles are used as a contrast agent. Macrophage accumulation of the iron particles allows regression of inflammation to be measured with drug therapy. Similarly, contrast-enhanced ultrasound imaging is also being evaluated for functional characterization of atherosclerotic plaques. For all of these techniques, however, large-scale clinical trials are mandatory to define the prognostic importance of the imaging signals in terms of risk of future vascular events.

Transient Ischemic Dilation in Diabetic Patients: Prognostic Value and Impact on Clinical Outcome after Coronary Revascularization

Background—We prospectively evaluated the incremental prognostic value of transient ischemic dilation (TID) in patients with type 2 diabetes mellitus during long-term follow-up and estimated cardiac death and nonfatal myocardial infarction (MI) using traditional approaches of prognostication to more recent methods. Methods and Results—A total of 672 consecutive diabetic patients with available rest and stress gated myocardial perfusion single-photon emission computed tomographic data were enrolled. Stepwise Cox regression analysis was used to estimate cardiac death or nonfatal MI. Risk reclassification was calculated, and an exploratory analysis was performed to evaluate the effect of coronary revascularization on event-free survival. Adding TID to a multivariable model, including age, history of MI, stress type, poststress left ventricular ejection fraction, and stress-induced myocardial ischemia, improved discrimination of cardiac death or nonfatal MI (C statistic, 0.74–0.82; P=0.01; adjusted hazard ratio, 3.6; P<0.0001) and led to a net reclassification improvement of 0.39 (95% confidence interval, 0.14–0.64). Revascularization had a significant effect on event-free survival (adjusted hazard ratio, 0.25; P<0.001), with significant interactions between revascularization and poststress left ventricular ejection fraction, revascularization and stress-induced myocardial ischemia, and revascularization and TID (all P<0.01) Conclusions—TID provides independent and incremental prognostic information for the prediction of cardiac death or nonfatal MI in patients with diabetes mellitus. The addition of TID to a prediction model based on cardiovascular risk factors, left ventricular ejection fraction, and ischemia significantly improves risk discrimination and reclassification for incident cardiac events. The effect of revascularization seems to be influenced by left ventricular systolic function, stress-induced myocardial ischemia, and TID.

Transient Ischemic Dilation in Patients With Diabetes Mellitus: Prognostic Value and Effect on Clinical Outcome After Coronary Revascularization

Background—We prospectively evaluated the incremental prognostic value of transient ischemic dilation (TID) in patients with type 2 diabetes mellitus during long-term follow-up and estimated cardiac death and nonfatal myocardial infarction (MI) using traditional approaches of prognostication to more recent methods. Methods and Results—A total of 672 consecutive diabetic patients with available rest and stress gated myocardial perfusion single-photon emission computed tomographic data were enrolled. Stepwise Cox regression analysis was used to estimate cardiac death or nonfatal MI. Risk reclassification was calculated, and an exploratory analysis was performed to evaluate the effect of coronary revascularization on event-free survival. Adding TID to a multivariable model, including age, history of MI, stress type, poststress left ventricular ejection fraction, and stress-induced myocardial ischemia, improved discrimination of cardiac death or nonfatal MI (C statistic, 0.74–0.82; P=0.01; adjusted hazard ratio, 3.6; P<0.0001) and led to a net reclassification improvement of 0.39 (95% confidence interval, 0.14–0.64). Revascularization had a significant effect on event-free survival (adjusted hazard ratio, 0.25; P<0.001), with significant interactions between revascularization and poststress left ventricular ejection fraction, revascularization and stress-induced myocardial ischemia, and revascularization and TID (all P<0.01) Conclusions—TID provides independent and incremental prognostic information for the prediction of cardiac death or nonfatal MI in patients with diabetes mellitus. The addition of TID to a prediction model based on cardiovascular risk factors, left ventricular ejection fraction, and ischemia significantly improves risk discrimination and reclassification for incident cardiac events. The effect of revascularization seems to be influenced by left ventricular systolic function, stress-induced myocardial ischemia, and TID.

Stress cardiac single-photon emission computed tomographic imaging late after coronary artery bypass surgery for risk stratification and estimation of time to cardiac events.

OBJECTIVE We assessed predictors and temporal characteristics of cardiac risk in patients undergoing stress single-photon emission computed tomography after coronary artery bypass grafting. METHODS Stress cardiac tomography was performed in 362 patients 5 years after coronary artery bypass grafting. Cardiac death and myocardial infarction were considered as events. Cox proportional hazards analysis was used to identify predictors of events and parametric survival analysis to predict time to events. RESULTS During a median follow-up of 27 months, 22 cardiac events occurred (6.1% cumulative event rate). At multivariable Cox analysis, ischemia at cardiac tomography (hazards ratio 3.7, 95% confidence interval 1.5-9.1; P = .004), and diabetes (hazards ratio 3.6, 95% confidence interval 1.5-8.5; P = .006) resulted in independent predictors of events. Event-free survival was 96% in patients with normal cardiac tomography, 86% in those with abnormal tomography without ischemia, and 70% in those with (log-rank 10.6, P for trend = .008). The parametric survival model revealed that the cardiac risk was greater for all time intervals and accelerated more over time in patients with ischemia than in those without (chi(2) 21.4, P < .0001). Patients without diabetes and normal cardiac tomography remained below a defined risk level (5%) for the entire follow-up period. CONCLUSION Stress cardiac tomography performed 5 years after coronary artery bypass grafting is useful to characterize the risk of cardiac events and its temporal variation. Parametric survival model estimates the predicted time to risk and the level of risk at specific time intervals after coronary artery bypass grafting.

Prognostic value of reduced kidney function and anemia in patients with chronic heart failure.

Objectives The present study aimed to evaluate the prognostic value of B-type natriuretic peptide (N-proBNP), renal dysfunction and anemia in chronic heart failure (CHF) patients. Methods We analyzed data from a prospective cohort of 153 patients (mean age 64 years) with CHF referred to our hospital center. Clinical, echocardiographic and laboratory data were drawn during hospital recovery in all patients. Kidney dysfunction was defined as a glomerular filtration rate (GFR) < 60 ml/min and anemia as a hematocrit < 35%. After discharge, patients attended the outpatient clinic of our institution. Results Kidney dysfunction was diagnosed in 37% of cases, whereas anemia was present in 25% of patients. During follow-up (median time 456 days), 32 patients died. Multivariate Cox proportional hazard model revealed that N-proBNP [hazard ratio (HR) = 1.002; P < 0.001] and GFR (HR = 0.972; P < 0.005) were significant predictors for mortality after adjustment for confounding variables. Kaplan–Maier analysis demonstrated a progressive decrease in survival from lowest to highest tertiles of N-proBNP values (log rank = 28.7; P < 0.001) and from higher to lower GFR values (log rank = 5.63; P < 0.01). Moreover, parametric survival analysis by the Weibull model demonstrated that the estimated probability of survival adjusted for N-proBNP values was higher in patients with GFR ≥ 60 ml/min than in those with GFR < 60 ml/min (P < 0.001). Conclusion Increased N-proBNP and decreased kidney function, but not anemia, are independent risk factors for mortality in patients with CHF.

Myocardial perfusion imaging after coronary revascularization: a clinical appraisal

Revascularization procedures, including percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG), are performed in many patients with coronary artery disease. Despite the effectiveness of these procedures, different follow-up strategies need to be considered for the management of patients after revascularization. Stress myocardial perfusion single-photon emission computed tomography (MPS) is a suitable imaging method for the evaluation of patients who have undergone PCI or CABG, and it has been used in the follow-up of such patients. Radionuclide imaging is included in the follow-up strategies after PCI and CABG in patients with symptoms, but guidelines warn against routine testing of all asymptomatic patients after revascularization. After PCI, in the absence of symptoms, radionuclide imaging is recommended and indicated as appropriate after incomplete or suboptimal revascularization and in specific asymptomatic patient subsets. On the other hand, the value of MPS late after CABG in risk stratification has been demonstrated even in the absence of symptoms. Thus, given the adverse outcome associated with silent ischaemia, it can be speculated that all patients regardless of clinical status should undergo stress testing late after revascularization. Larger prospective studies are needed to assess whether stress MPS will have an impact on the outcome in asymptomatic patients after revascularization.

Detection of silent myocardial ischemia: Is it clinically relevant?

Silent myocardial ischemia is defined as objective documentation of myocardial ischemia in the absence of angina or anginal equivalents. The first description of silent ischemia date to the 1970s, but despite intensive investigation, its pathophysiology, detection, prevalence, and clinical significance are still debated. The need and the benefit of treating silent ischemia, particularly in patients without history of coronary artery disease (CAD) and who are asymptomatic, remain questionable. Asymptomatic (silent) myocardial ischemia may be identified during routine daily activities or during stress testing in patients without or with known CAD. One of the earliest investigations addressing the prevalence and significance of silent myocardial ischemia in asymptomatic subjects is the United States Air Force study, conducted in 1,390 men, 111 of whom had positive exercise tests. Thirty-four of these 111 (about 2.5% of the total) had coronary artery lesions of at least 50% stenosis. Thaulow et al studied 2014 Norwegian male office workers between 40 and 59 years of age (mean age 50 year). Coronary angiography in men with positive exercise tests demonstrated that 69 had stenoses of 50% or greater in one coronary artery; 50 of these (2.7% of the total) patients were completely asymptomatic, a percentage similar to that found in the United States Air Force study. He et al reported in nearly 4,000 subjects studied, that the severity of coronary artery calcification by electron-beam computed tomography (CT) can predict silent myocardial ischemia on stress single-photon emission computed tomography (MPS). Silent myocardial ischemia was present in 2.6% of patients with coronary calcium score between 11 and 100, 11.3% of patients with scores between 101 and 399, and 46% of patients with scores above 400. In this issue of the Journal, Malhotra et al evaluated the relationship between silent myocardial ischemia and CAD risk factors in a retrospective analysis of 1,354 asymptomatic patients without known CAD referred for stress MPS. The most common reasons for referral of these patients without chest pain or dyspnea were CAD risk factors, atrial fibrillation, and pre-operative evaluation. As expected, the prevalence of silent myocardial ischemia in these asymptomatic subjects was very low (7.2%). The authors identified a positive relationship between the number of CAD risk factors and the prevalence of silent myocardial ischemia. However in older patients ([74 years), who had a significantly greater prevalence of silent ischemia, the presence and number of risk factors were not predictive. The positive predictive value of an abnormal MPS for predicting angiographic CAD was only 53% and, among all asymptomatic patients referred for stress MPS, significant anatomical CAD was found in only 31 of 1,354 (2%) patients. Malhotra et al concluded that their findings support current guidelines, which generally advocate against routine testing in asymptomatic patients. Unfortunately, they did not provide outcome information for these patients, in particular for the 60 patients (4.4% of overall study population) defined to have ‘‘prognostically significant ischemia’’ (i.e., [10% of left ventricular myocardium). Previous studies have found that silent myocardial ischemia detected in healthy individuals without known CAD has been shown to predict adverse events. The Lipid Research Clinic’s Coronary Primary Prevention Trial (LRCPPT) and the Multiple Risk Factor Intervention Trial (MRFIT) showed that the presence of asymptomatic myocardial ischemia detected during baseline treadmill exercise testing in subjects without known CAD predicted a more than fivefold increased risk of coronary events and cardiac death during the 7to 10-year follow-up period. Other studies evaluated From the Department of Translational Medical Sciences, University Federico II, Institute of Diagnostic and Nuclear Development, SDN Foundation; and Department of Advanced Biomedical Sciences, University Federico II, Naples, Italy. Reprint requests: Alberto Cuocolo, MD, Department of Advanced Biomedical Sciences, University Federico II, Via Pansini 5, 80131 Naples, Italy; cuocolo@unina.it. J Nucl Cardiol 2013;20:707–10. 1071-3581/