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Positron emission tomography absolute stress myocardial blood flow for risk stratification in nonischemic
Thomas G Middour1, Todd M Rosenthal1, Freddy M Abi-Samra1
1Department of Cardiology, Division of Electrophysiology, Ochsner Medical Center, New Orleans, Louisiana.
Insights
Lower stress myocardial blood flow (sMBF) measured by PET imaging predicts ventricular arrhythmias (VA) in nonischemic cardiomyopathy (NICM) patients. This finding aids risk stratification for implantable cardioverter-defibrillator (ICD) decisions.
Area of Science:
- Cardiology
- Nuclear Medicine
- Medical Imaging
Background:
- Sudden cardiac death is a significant risk in cardiomyopathy patients.
- Risk stratification for implantable cardioverter-defibrillator (ICD) implantation is less robust in nonischemic cardiomyopathy (NICM) compared to ischemic cardiomyopathy.
- Improved methods are needed to identify NICM patients at high risk for ventricular arrhythmias (VA).
Purpose of the Study:
- To assess if absolute quantification of stress myocardial blood flow (sMBF) using positron emission tomography (PET) can predict VA and/or death in NICM patients.
- To evaluate sMBF as a risk stratification tool for primary prevention in NICM.
- To determine the utility of sMBF in guiding ICD implantation decisions.
Main Methods:
- Prospective pilot study of 37 NICM patients with left ventricular ejection fraction ≤35% and an ICD.
- Cardiac PET stress imaging was performed for sMBF quantification.
- Patients were followed for appropriate device therapy for VA and all-cause mortality, with subgroup analysis for primary prevention.
Main Results:
- Lower sMBF was a significant predictor of VA in both the overall NICM population (HR 0.84, P=.015) and the primary prevention subset (HR 0.81, P=.049).
- Patients with sMBF below the median experienced significantly more VA compared to those with higher sMBF (P=.004 overall, P=.046 primary prevention).
- Estimated 3-year VA rates were substantially higher in low-flow patients (67% overall, 39% primary prevention) versus high-flow patients (13% overall, 8% primary prevention). sMBF did not predict all-cause mortality.
Conclusions:
- Reduced stress myocardial blood flow (sMBF) independently predicts ventricular arrhythmias (VA) in patients with nonischemic cardiomyopathy (NICM).
- sMBF quantification by PET is a promising tool for risk stratification in NICM.
- These findings support the use of sMBF to guide implantable cardioverter-defibrillator (ICD) implantation decisions in NICM patients.
Introduction:
Sudden cardiac death is a substantial cause of mortality in patients with cardiomyopathy, but evidence supporting implantable cardioverter-defibrillator (ICD) implantation is less robust in nonischemic cardiomyopathy (NICM) than in ischemic cardiomyopathy. Improved risk stratification is needed. We assessed whether absolute quantification of stress myocardial blood flow (sMBF) measured by positron emission tomography (PET) predicts ventricular arrhythmias (VA) and/or death in patients with NICM.
Methods:
In this pilot study, we prospectively followed patients with NICM (left ventricular ejection fraction ≤ 35%) and an ICD who underwent cardiac PET stress imaging with sMBF quantification. NICM was defined as the absence of angiographic obstructive coronary stenosis, significant relative perfusion defects on imaging, coronary revascularization, or acute coronary syndrome. Endpoints were appropriate device therapy for VA and all-cause mortality. Subgroup analysis was performed in patients who had no prior history of VA (ie, the primary prevention population).
Results:
We followed 37 patients (60 ± 14 years, 46% male) for 41 ± 23 months. The median sMBF was 1.56 mL/g/min (interquartile range: 1.00-1.82). Lower sMBF predicted VA, both in the whole population (hazard ratio [HR] for each 0.1 mL/g/min increase: 0.84, P = .015) and in the primary prevention subset (n = 27; HR for each 0.1 mL/g/min increase: 0.81, P = .049). Patients with sMBF below the median had significantly more VA than those above the median, both in the whole population (P = .004) and in the primary prevention subset (P = .046). Estimated 3-year VA rates in the whole population were 67% among low-flow patients vs 13% among high-flow patients, and 39% vs 8%, respectively, among primary-prevention patients. sMBF did not predict all-cause mortality.
Conclusions:
In patients with NICM, lower sMBF predicts VA. This relationship may be useful for risk stratification for ventricular arrhythmia and decision making regarding ICD implantation.
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