Assessment of left ventricular function with gated myocardial perfusion SPECT and gated myocardial FDG PET in patients with left ventricular mechanical dyssynchrony

BACKGROUND

Left ventricular mechanical dyssynchrony (LVMD) and left ventricular function are intertwined. Gated myocardial perfusion SPECT (MPS) and gated fluorodeoxyglucose positron emission computed tomography (FDG PET) is an elegant way for repeated assessment of myocardial dyssynchrony and myocardial function. To the knowledge of the authors at the time this manuscript was prepared, there was no comprehensive evaluation of the interplay of LVMD and left ventricular function as measured by gated MPS and gated FDG PET; as well as no evaluation of the agreement between the two methods.

METHODS

Patients were assigned to the reference cohort (RC) and the dyssynchrony cohort (DC) based on the phase analysis results of gated MPS datasets. Subsequently left ventricular function was analyzed.

RESULTS

We demonstrated that LVMD as detected by gated MPS is associated with a significantly higher end-diastolic volume (EDV) and end-systolic volume (ESV) as well as a significantly reduced left ventricular ejection fraction (LVEF) both in gated MPS and gated FDG PET imaging. In the RC and the DC SPECT and PET showed good agreement and generally high linear correlations with regard to left ventricular volumes and LVEF. In the combined cohort (RC and DC) increasing amounts of LVMD were associated with increasing left ventricular volumes as well as a decreasing LVEF. The association was strongest for the dyssynchrony parameter Entropy.

CONCLUSIONS

We demonstrated that gated SPECT and gated PET are useful tools in the evaluation of left ventricular function in patients with LVMD as detected by gated MPS. Increasing amounts of dyssynchrony were associated with an increasingly reduced myocardial function. For repeated measurements or therapy monitoring, the methods should not be used interchangeably.

Cardiac Magnetic Resonance Left Ventricular Mechanical Uniformity Alterations for Risk Assessment After Acute Myocardial Infarction

Background Despite limitations as a stand-alone parameter, left ventricular (LV) ejection fraction is the preferred measure of myocardial function and marker for postinfarction risk stratification. LV myocardial uniformity alterations may provide superior prognostic information after acute myocardial infarction, which was the subject of this study. Methods and Results Consecutive patients with acute myocardial infarction (n=1082; median age: 63 years; 75% male) undergoing cardiac magnetic resonance at a median of 3 days after infarction were included in this multicenter observational study. Circumferential and radial uniformity ratio estimates were derived from cardiac magnetic resonance feature tracking as markers of mechanical uniformity alterations (values between 0 and 1 with 1 reflecting perfect uniformity). The clinical end point was the 12-month rate of major adverse cardiac events, consisting of all-cause death, reinfarction, and new congestive heart failure. Patients with major adverse cardiac events (n=73) had significantly impaired circumferential uniformity ratio estimates (0.76 [interquartile range: 0.67-0.86] versus 0.84 [interquartile range: 0.76-0.89]; P<0.001) and radial uniformity ratio estimates (0.69 [interquartile range: 0.60-0.79] versus 0.76 [interquartile range: 0.67-0.83]; P<0.001) compared with patients without events. Although uniformity estimates did not provide independent prognostic information in the overall cohort, a circumferential uniformity ratio estimate below the median of 0.84 emerged as an independent predictor of outcome in postinfarction patients with LV ejection fraction >35% (n=959), even after adjustment for established risk factors (hazard ratio: 1.99; 95% CI, 1.06-3.74; P=0.033 in multivariable Cox regression analysis). In contrast, LV ejection fraction was not associated with adverse events in this subgroup of patients with acute myocardial infarction. Conclusions Cardiac magnetic resonance-derived estimates of mechanical uniformity alterations are novel markers for risk assessment after acute myocardial infarction, and the circumferential uniformity ratio estimate provides independent prognostic information for patients with preserved or only moderately reduced LV ejection fraction.

Accuracy of three-dimensional systolic dyssynchrony and sphericity indexes for identifying early left ventricular remodeling after acute myocardial infarction

Objective:

Left ventricle (LV) geometry and dyssynchrony are associated with LV remodeling after acute myocardial infarction (AMI). The aim of this prospective study was to assess the diagnostic value of new three-dimensional echocardiography (3DE) parameters [sphericity (SI) and systolic dyssynchrony indexes (SDI)] for the prediction of LV remodeling after AMI and to compare them with two-dimensional echocardiography (2DE) parameters.

Methods:

2DE and 3DE were performed in 75 patients with AMI within 3 days from the onset of MI and 6 months later. LV remodeling was defined as a ≥15% increase in the LV end-diastolic volume (EDV) at follow-up. 3D SI was calculated by dividing EDV by the volume of a sphere whose diameter was derived from the major end-diastolic LV long axis. SDI was considered as a standard deviation of the time from cardiac cycle onset to minimum systolic volume in 16 LV segments.

Results:

LV remodeling was identified in 34 (45%) patients using the 2DE method and in 22 (29%) patients using the 3DE method. Evaluated 3DE parameters, such as EDV [area under the receiver operating characteristic (ROC) curve (AUC) 0.742, sensitivity 71%, specificity 79%], end-systolic volume (AUC 0.729, sensitivity 69%, specificity 78%), SDI (AUC 0.777, sensitivity 73%, specificity 77%), and SI, had significant prognostic value for LV remodeling. According to the AUC, the highest predictive value had 3D SI (AUC 0.957, sensitivity 90%, specificity 91%).

Conclusion:

3DE parameters, especially 3D SI and SDI, play important roles in the prediction of LV remodeling after AMI and can be used in clinical practice.

Prevalence, Correlates, and Prognostic Relevance of Myocardial Mechanical Dispersion as Assessed by Feature-Tracking Cardiac Magnetic Resonance After a First ST-Segment Elevation Myocardial Infarction

Postinfarction mechanical dispersion (MD), that is, the regional heterogeneity of myocardial contraction throughout the cardiac cycle, has detrimental effects on left ventricular (LV) function and is related to the occurrence of heart failure and ventricular arrhythmias. However, its prevalence, pathophysiological determinants, and clinical utility are still unknown. The aim of the present study is to clarify these issues. In total, 130 consecutive patients (mean age 60 ± 12 years, 75% male) with a first ST-segment elevation myocardial infarction (STEMI) were included. Cardiac magnetic resonance (CMR) with late gadolinium enhancement imaging was performed to assess LV function, infarct size, and microvascular obstruction. Feature-tracking analysis was applied to cine-CMR short-axis images to assess MD, defined as the SD of the time-to-peak circumferential strain of the LV segments expressed as percent cardiac cycle. For comparison purpose, 40 control subjects similar in age and gender to the STEMI group were also included. Patients were followed-up for a median of 95 months; the outcome event was defined as a composite of cardiovascular death, aborted sudden cardiac death, and hospitalization for heart failure. STEMI patients had significantly higher MD compared with controls (12.0 ± 5.35% vs 3.85 ± 0.99%, p <0.001). At multivariate analysis, heart rate (β = 0.20, p = 0.008), LV end-systolic volume index (β = 0.37, p <0.001), and infarct size (β = 0.23, p = 0.017) were significantly and independently related to MD. The outcome event occurred in 26 (20%) patients. At multivariate Cox proportional hazards analysis, MD was significantly and independently related to the outcome event (p <0.001). MD provided significant incremental value over the other clinical and CMR variables in predicting the outcome event (p <0.001 for the chi-square change). In conclusion, MD after STEMI is a marker of the extent of myocardial damage; its assessment by feature-tracking CMR provides significant, independent, and incremental long-term prognostic information.

Predictors of ventricular remodelling in patients with reperfused acute myocardial infarction and left ventricular dysfunction candidates for bone marrow cell therapy: insights from the BONAMI trial

PURPOSE

Few data are available regarding the relation of left ventricular (LV) mechanical dyssynchrony to remodelling after acute myocardial infarction (MI) and stem cell therapy. We evaluated the 1-year time course of both LV mechanical dyssynchrony and remodelling in patients enrolled in the BONAMI trial, a randomized, multicenter controlled trial assessing cell therapy in patients with reperfused MI.

METHODS

Patients with acute MI and ejection fraction (EF) ≤ 45 % were randomized to cell therapy or to control and underwent thallium single-photon emission computed tomography (SPECT), radionuclide angiography, and echocardiography at baseline, 3 months, and 1 year. Eighty-three patients with a comprehensive 1-year follow-up were included. LV dyssynchrony was assessed by the standard deviation (SD) of the LV phase histogram using radionuclide angiography. Remodelling was defined as a 20 % increase in LV end-systolic volume index (LVESVI) at 1 year.

RESULTS

At baseline, LVEF, wall motion score index, and perfusion defect size were significantly impaired in the 43 patients (52 %) with LV remodelling (all p < 0.001), without significant increase in LV mechanical dyssynchrony. During follow-up, there was a progressive increase in LV SD (p = 0.01). Baseline independent predictors of LV remodelling were perfusion SPECT defect size (p = 0.001), LVEF (p = 0.01) and a history of hypertension (p = 0.043). Bone marrow cell therapy did not affect the time-course of LV remodelling and dyssynchrony.

CONCLUSIONS

LV remodelling 1 year after reperfused MI is associated with progressive LV dyssynchrony and is related to baseline infarct size and ejection fraction, without impact of cell therapy on this process.

The 7-year teesside experience of primary prevention ICD indications following primary PCI (PPCI) and the potential impact of a change in NICE guidance

INTRODUCTION

The recovery of LV function in patients with severe LV impairment in the acute phase following primary percutaneous coronary intervention (PPCI) is not well established. The indication for a primary prevention ICD post-STEMI is dependent on which screening guidance, NICE or ESC, is followed. The potential impact of the new NICE guidance is estimated.

METHODS

We performed a retrospective analysis of all patients presenting with a STEMI over a 7-year period (2005-2012) treated with PPCI to determine in-hospital mortality, LV function at index presentation, at 3 months and the predicted primary prevention ICD implantation rate using NICE (TA095) and ESC 2006 guidelines. Predicted implant rates using the new NICE guidance (TA314) and actual implantation rates were also assessed.

RESULTS

3902 patients with a mean age of 65±13 years underwent PPCI. Of those patients surviving until discharge, 332 (10%) had LVEF ≤35%. 254 of 332 patients (76%) with a severely impaired ventricle were followed up at participating centres. 210 of 254 (83%) patients had a repeat echocardiogram within 3 months post-MI; among these patients, 89 (42%) remained to have LVEF ≤35%. The number of patients fulfilling NICE and ESC criteria for primary prevention ICD implantation was 14 (16%) and 84 (94%), respectively. The actual number of patients receiving an ICD was 17 (19%). The number of patients fulfilling the new NICE (TA314) guidance was 84 (94%).

CONCLUSIONS

A small proportion of patients with STEMIs undergoing PPCI have a severely impaired LV systolic function. A large proportion of these patients will have improved LV systolic function at 3 months. There is a five-fold difference in the predicted ICD implantation rates depending on which guidance is followed-NICE versus ESC. The potential impact of the new NICE (TA314) guidance on ICD implantation will be a significant increase in ICD implantation rates.

A nonthoracotomy myocardial infarction model in an ovine using autologous platelets

Objective. There is a paucity of a biological large animal model of myocardial infarction (MI). We hypothesized that, using autologous-aggregated platelets, we could create an ovine model that was reproducible and more closely mimicked the pathophysiology of MI. Methods. Mepacrine stained autologous platelets from male sheep (n = 7) were used to create a myocardial infarction via catheter injection into the mid-left anterior descending (LAD) coronary artery. Serial daily serum troponin measurements were taken and tissue harvested on post-embolization day three. Immunofluorescence microscopy was used to detect the mepacrine-stained platelet-induced thrombus, and histology performed to identify three distinct myocardial (infarct, peri-ischemic “border zone,” and remote) zones. Results. Serial serum troponin levels (μg/mL) measured 0.0 ± 0.0 at baseline and peaked at 297.4 ± 58.0 on post-embolization day 1, followed by 153.0 ± 38.8 on day 2 and 76.7 ± 19.8 on day 3. Staining confirmed distinct myocardial regions of inflammation and fibrosis as well as mepacrine-stained platelets as the cause of intravascular thrombosis. Conclusion. We report a reproducible, unique model of a biological myocardial infarction in a large animal model. This technique can be used to study acute, regional myocardial changes following a thrombotic injury.

The year 2012 in the European Heart Journal-Cardiovascular Imaging. Part II

The part II of the best of the European Heart Journal - Cardiovascular Imaging in 2012 specifically focuses on studies of valvular heart diseases, heart failure, cardiomyopathies, and congenital heart diseases.