No differences in rest myocardial blood flow in stunned and hibernating myocardium: insights into the pathophysiology of ischemic cardiomyopathy

Prediction of major arrhythmic outcomes in ischaemic cardiomyopathy: value of hibernating myocardium in positron emission tomography/computed tomography

AIMS

Known predictors of major arrhythmic events (MAEs) in patients with ischaemic cardiomyopathy (ICM) include previous MAE and left ventricular ejection fraction (LVEF) ≤ 35%. Myocardial scars detected by perfusion imaging in ICM have been linked to MAE, but the prognostic significance of hibernating myocardium (HM) is unclear. The objective was to predict MAEs from combined 13N-ammonia (NH3) and 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in ICM.

METHODS AND RESULTS

Consecutive patients with ICM undergoing combined NH3- and FDG-PET/CT were included. HM was quantified in relation to total left ventricular myocardium (i.e. ≥7% is large). The primary outcome was MAEs [sudden cardiac death, implantable cardioverter defibrillator (ICD) therapy, and sustained ventricular tachycardia/fibrillation].Among 254 patients, median baseline LVEF was 35% [interquartile range (IQR) 28-45] and 10% had an ICD. PET/CT identified ischaemia in 94 (37%), scar in 229 (90%), and HM in 195 (77%) patients. Over a median follow-up of 5.4 (IQR 2.2-9.5) years, MAE occurred in 34 patients (13%). Large HM was associated with a lower incidence of MAE (hazard ratio 0.31, 95% confidence interval 0.1-0.8, P = 0.001). After multivariate adjustment for history of MAE, LVEF ≤35%, and scar ≥10%, large HM remained significantly associated with a lower incidence of MAE (P = 0.016). LVEF improved over time among patients with large HM (P = 0.006) but did not change in those without (P = 0.610) or small HM (P = 0.240).

CONCLUSION

HM conveys a lower risk of MAE in patients with ICM. This may be explained by an increase in LVEF when a large extent of HM is present.

Long-term impact of myocardial inflammation on quantitative myocardial perfusion-a descriptive PET/MR myocarditis study

PURPOSE

Whether myocardial inflammation causes long-term sequelae potentially affecting myocardial blood flow (MBF) is unknown. We aimed to assess the effect of myocardial inflammation on quantitative MBF parameters, as assessed by 13N-ammonia positron emission tomography myocardial perfusion imaging (PET-MPI) late after myocarditis.

METHODS

Fifty patients with a history of myocarditis underwent cardiac magnetic resonance (CMR) imaging at diagnosis and PET/MR imaging at follow-up at least 6 months later. Segmental MBF, myocardial flow reserve (MFR), and 13N-ammonia washout were obtained from PET, and segments with reduced 13N-ammonia retention, resembling scar, were recorded. Based on CMR, segments were classified as remote (n = 469), healed (inflammation at baseline but no late gadolinium enhancement [LGE] at follow-up, n = 118), and scarred (LGE at follow-up, n = 72). Additionally, apparently healed segments but with scar at PET were classified as PET discordant (n = 18).

RESULTS

Compared to remote segments, healed segments showed higher stress MBF (2.71 mL*min-1*g-1 [IQR 2.18-3.08] vs. 2.20 mL*min-1*g-1 [1.75-2.68], p < 0.0001), MFR (3.78 [2.83-4.79] vs. 3.36 [2.60-4.03], p < 0.0001), and washout (rest 0.24/min [0.18-0.31] and stress 0.53/min [0.40-0.67] vs. 0.22/min [0.16-0.27] and 0.46/min [0.32-0.63], p = 0.010 and p = 0.021, respectively). While PET discordant segments did not differ from healed segments regarding MBF and MFR, washout was higher by ~ 30% (p < 0.014). Finally, 10 (20%) patients were diagnosed by PET-MPI as presenting with a myocardial scar but without a corresponding LGE.

CONCLUSION

In patients with a history of myocarditis, quantitative measurements of myocardial perfusion as obtained from PET-MPI remain altered in areas initially affected by inflammation. CMR = cardiac magnetic resonance; PET = positron emission tomography; LGE = late gadolinium enhancement.

Quantitative myocardial perfusion SPECT/CT for the assessment of myocardial tracer uptake in patients with three-vessel coronary artery disease: Initial experiences and results

BACKGROUND

To evaluate quantitative myocardial perfusion SPECT/CT datasets for routine clinical reporting and the assessment of myocardial tracer uptake in patients with severe TVCAD.

METHODS

MPS scans were reconstructed as quantitative SPECT datasets using CTs from internal (SPECT/CT, Q_INT) and external (PET/CT, Q_EXT) sources for attenuation correction. TPD was calculated and compared to the TPD from non-quantitative SPECT datasets of the same patients. SUVmax, SUVpeak, and SUVmean were compared between Q_INT and Q_EXT SPECT datasets. Global SUVmax and SUVpeak were compared between patients with and without TVCAD.

RESULTS

Quantitative reconstruction was feasible. TPD showed an excellent correlation between quantitative and non-quantitative SPECT datasets. SUVmax, SUVpeak, and SUVmean showed an excellent correlation between Q_INT and Q_EXT SPECT datasets, though mean SUVmean differed significantly between the two groups. Global SUVmax and SUVpeak were significantly reduced in patients with TVCAD.

CONCLUSIONS

Absolute quantification of myocardial tracer uptake is feasible. The method seems to be robust and principally suitable for routine clinical reporting. Quantitative SPECT might become a valuable tool for the assessment of severe coronary artery disease in a setting of balanced ischemia, where potentially life-threatening conditions might otherwise go undetected.

Growth Differentiation Factor 15 is Related with Left Ventricular Recovery in Patients with ST-Elevation Myocardial Infarction after Successful Reperfusion by Primary Percutaneous Intervention

Background

The determinants of left ventricular (LV) recovery after successful revascularization in ST-elevation myocardial infarction (STEMI) patients are not clear. In addition, the relationship between growth differentiation factor15 (GDF-15) and left ventricular ejection fraction (LVEF) improvement is also unknown. This study hypothesizes that a low GDF-15 level would be associated with LVEF recovery.

Methods

One hundred and sixty-one STEMI patients were included in this study. Echocardiographic examinations were performed before and 12-18 weeks after discharge. The patients were divided into three groups according to the changes in LVEF as 62 patients with ≥ 10% change, 47 patients with 1-9% change, and 52 patients ≤ 0% change. LV recovery was defined as ≥ 10% LVEF improvement and the predictors of LV recovery were investigated. Moreover, two groups were created according to GDF-15 values, and the follow-up/baseline echocardiographic parameters were compared between these groups.

Results

LV recovery was detected in 38.5% of the patients. Low baseline LVEF [odds ratio (OR): 0.85, 95% confidence interval (CI) 0.82-0.94, p = 0.001], low GDF-15 (OR: 0.79, 95% CI 0.68-0.93, p = 0.004), previous angina (OR: 2.34, 95% CI 1.10-4.96, p = 0.027), and symptom-to-balloon time (OR: 0.97, 95% CI 0.95-1.00, p = 0.043) were independent predictors of LV recovery. The ratios of follow-up/baseline LV end-diastolic volume index, LV end-systolic volume index and wall motion score index were lower in the low GDF-15 group (0.96 vs. 1.04, p < 0.001; 0.96 vs. 1.10, p < 0.001; 0.89 vs. 0.96, p < 0.001). Moreover, being in the low GDF-15 group was associated with LV recovery (OR: 2.93, 95% CI 1.43-6.02, p = 0.001).

Conclusions

Lower GDF-15 level was associated with better LV improvement and less adverse remodeling in STEMI patients.

Prognostic Value of Quantitative Metrics From Positron Emission Tomography in Ischemic Heart Failure

OBJECTIVES

The aim of this study was to investigate the prognostic and clinical value of quantitative positron emission tomographic (PET) metrics in patients with ischemic heart failure.

BACKGROUND

Although myocardial flow reserve (MFR) is a strong predictor of cardiac risk in patients without heart failure, it is unknown whether quantitative PET metrics improve risk stratification in patients with ischemic heart failure.

METHODS

The study included 254 patients referred for stress and rest myocardial perfusion imaging and viability testing using PET. Major adverse cardiac event(s) (MACE) consisted of death, resuscitated sudden cardiac death, heart transplantation, acute coronary syndrome, hospitalization for heart failure, and late revascularization.

RESULTS

MACE occurred in 170 patients (67%) during a median follow-up of 3.3 years. In a multivariate Cox proportional hazards model including multiple quantitative PET metrics, only MFR predicted MACE significantly (p = 0.013). Beyond age, symptom severity, diabetes mellitus, previous myocardial infarction or revascularization, 3-vessel disease, renal insufficiency, ejection fraction, as well as presence and burden of ischemia, scar, and hibernating myocardium, MFR was strongly associated with MACE (adjusted hazard ratio per increase in MFR by 1: 0.63; 95% confidence interval: 0.45 to 0.91). Incorporation of MFR into a risk assessment model incrementally improved the prediction of MACE (likelihood ratio chi-square test [16] = 48.61 vs. chi-square test [15] = 39.20; p = 0.002).

CONCLUSIONS

In this retrospective analysis of a single-center cohort, quantitative PET metrics of myocardial blood flow all improved risk stratification in patients with ischemic heart failure. However, in a hypothesis-generating analysis, MFR appears modestly superior to the other metrics as a prognostic index.

Myocardial Viability Testing by Positron Emission Tomography: Basic Concepts, Mini-Review of the Literature and Experience From a Tertiary PET Center

Ischemic heart disease ranges in severity from slightly reduced myocardial perfusion with preserved contractile function to chronic occlusion of coronary arteries with myocardial cells replaced by acontractile scar tissue-ischemic heart failure (iHF). Progression towards scar tissue is thought to involve a period in which the myocardial cells are acontractile but still viable despite severely reduced perfusion. This state of reduced myocardial function that can be reversed by revascularization is termed "hibernation." The concept of hibernating myocardium in iHF has prompted an increasing amount of requests for preoperative patient workup, but while the concept of viability is widely agreed upon, no consensus on clinical testing of hibernation has been established. Therefore, a variety of imaging methods have been used to assess hibernation including morphology based (MRI and ultrasound), perfusion based (MRI, SPECT, or PET) and/or methods to assess myocardial metabolism (PET). Regrettably, the heterogeneous body of literature on the subject has resulted in few robust prospective clinical trials designed to assess the impact of preoperative viability testing prior to revascularization. However, the PARR-2 trial and sub-studies has indicated that >5% hibernating myocardium favors revascularization over optimized medical therapy. In this paper, we review the basic concepts and current evidence for using PET to assess myocardial hibernation and discuss the various methodologies used to process the perfusion/metabolism PET images. Finally, we present our experience in conducting PET viability testing in a tertiary referral center.

Noninvasive Assessment of Coronary Artery Disease - Anatomical versus Functional Imaging and the Marginal Role of Exercise Electrocardiograms

Coronary artery disease (CAD) is the leading cause of morbidity and mortality in the industrialized countries. Assessment of symptomatic patients with suspected obstructive CAD is a common reason for a clinical visit. Noninvasive anatomical and functional imaging are established tools to rule-in and rule-out CAD, to assess the severity of disease and to determine the potential risk of future cardiovascular events. In this review, we discuss the updated Guidelines from the European Society of Cardiology on Chronic Coronary Syndromes and explore the different imaging modalities used in current clinical practice for the noninvasive assessment of CAD. The pros and cons of each method, especially comparing anatomical and functional testing, are presented. Furthermore we we address the practical clinical aspects in the selection of the optimal noninvasive tests according to clinical need.