Metabolic imaging of patients with cardiomyopathy

The cardiomyopathies comprise a diverse group of illnesses that can be characterized functionally by several techniques. However, the delineation of derangements of regional perfusion and metabolism have been accomplished only relatively recently with positron emission tomography (PET). Regional myocardial accumulation and clearance of ¹¹C-palmitate, the primary myocardial substrate under most conditions, demonstrate marked spatial heterogeneity when studied under fasting conditions or with glucose loading. PET with ¹¹C-palmitate permits the noninvasive differentiation of patients with nonischemic from ischemic dilated cardiomyopathy, since patients with ischemic cardiomyopathy demonstrate large zones of intensely depressed accumulation of ¹¹C-palmitate, probably reflecting prior infarction. Patients with hypertrophic cardiomyopathy and Duchenne's muscular dystrophy demonstrate relatively unique patterns of myocardial abnormalities of perfusion and metabolism. The availability of new tracers and techniques for the evaluation of myocardial metabolism (¹¹C-acetate), perfusion (H₂¹⁵O), and autonomic tone (¹¹C-hydroxyephedrine) should facilitate further understanding of the pathogenesis of the cardiomyopathies.