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Role of Cardiac MRI and PET in Predicting Ventricular Arrhythmias
Quick Takes
- In a prospective cohort study of 74 patients with ischemic cardiomyopathy and LVEF ≤35% with primary prevention ICD, cardiac MRI-based markers of cardiac function and scar border zone predicted incidence of ventricular arrhythmias (VA).
- PET-based coronary perfusion and sympathetic innervation did not correlate with incidence of VA. However, lower coronary flow reserve correlated with all-cause mortality.
Study Questions:
Are cardiac magnetic resonance imaging (MRI)-assessed scar burden and cardiac function and positron emission tomography (PET)-assessed myocardial perfusion and sympathetic innervation predictors of ventricular arrhythmias (VA) in patients with an implantable cardioverter-defibrillator (ICD) for ischemic cardiomyopathy?
Methods:
This was a prospective analysis of 74 patients with ischemic cardiomyopathy (history of percutaneous coronary intervention/myocardial infarction/coronary artery bypass grafting) and left ventricular ejection fraction (LVEF) ≤35% who had a primary prevention ICD placed. Patients with sustained VA, nonsinus rhythm, or unable to undergo cardiac MRI/PET were excluded. Late gadolinium-enhanced cardiac MRI was performed to assess LV function and scar. PET using [15O]H2O and [11C]hydroxyephedrine was used to assess resting and hyperemic myocardial blood flow, coronary flow reserve (CFR), and sympathetic innervation. Outcomes of interest included VA and all-cause mortality at follow-up.
Results:
Mean age for the cohort was 66 ± 9 years and 88% were male. Over a mean follow-up period of 5.4 ± 1.9 years, 20 (26%) patients had VA. Baseline characteristics did not differ significantly between patients who had VA versus not. A total of 11 (15%) patients died with six patients dying without experiencing VA. Cardiac MRI was performed in 73 patients. In patients with VA, mean LVEF on cardiac MRI was lower (26 ± 6% vs. 30 ± 6%; p < 0.01), with higher LV end-diastolic volume index (LVEDVi) and LV end-systolic volume index. The total amount of scar border zone was significantly higher in patients who experienced VA compared to those without (11 ± 5 vs. 9 ± 4 g; p < 0.01). A complete cardiac PET was performed in 64 patients. There were no significant differences in CFR, resting and hyperemic myocardial blood flow, and sympathetic innervation between patients with and without VA. In univariate analyses, a lower LVEF, higher LVEDVi, and higher scar border zone were associated with increased hazard for VA. Higher LVEDVi, lower CFR, and higher N-terminal pro–B-type natriuretic peptide were significantly associated with combination of VA or all-cause mortality.
Conclusions:
In this small, prospective cohort of patients with ischemic cardiomyopathy with a primary prevention ICD, cardiac MRI-assessed LVEF, LVEDVi, and scar border zone were significantly associated with VA. PET-based coronary perfusion and sympathetic innervation were not associated with VA. However, LVEDVi and CFR were associated with a combined endpoint of VA and mortality.
Perspective:
Primary prevention ICDs are widely used in heart failure patients with an EF of ≤35% for prevention of sudden cardiac death. However, a small minority of these patients experience life-threatening VA needing ICD therapy. In this small study, the authors attempt to identify predictors of VA using cardiac MRI-based cardiac function and scar characteristics and PET-based perfusion and sympathetic innervation. While cardiac MRI-based EF, cardiac dimensions, and scar border zones predicted VA, PET-based characteristics did not correlate with VA. Major limitations of this study include its small cohort size, limiting the variables that could be assessed. Accordingly, this does not provide evidence against the value of PET in risk stratification of VA. However, these findings suggest that improved prediction of VA using advanced imaging has challenges, and additional studies in larger populations are needed to reliably identify predictors of sudden cardiac death.
Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Heart Failure and Cardiac Biomarkers, Computed Tomography, Magnetic Resonance Imaging, Nuclear Imaging
Keywords: Arrhythmias, Cardiac, Cardiomyopathies, Death, Sudden, Cardiac, Defibrillators, Implantable, Diagnostic Imaging, Gadolinium, Heart Failure, Magnetic Resonance Imaging, Myocardial Infarction, Myocardial Ischemia, Natriuretic Peptide, Brain, Perfusion Imaging, Positron-Emission Tomography, Primary Prevention, Stroke Volume, Ventricular Function, Left
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