Dilated cardiomyopathy is a feature of Duchenne and Becker muscular dystrophies and occasionally of sarcoglycanopathies. Its pathogenesis is unknown. Patients with myotonic dystrophy have an impairment of coronary smooth muscle and this could contribute to their cardiomyopathy. We used positron emission tomography (PET) to study myocardial blood flow and coronary vasodilator reserve at baseline and during hyperemia in 7 Duchenne, 8 Becker, and 5 sarcoglycanopathy patients. The study was normal in all Becker patients. In contrast, baseline myocardial blood flow was increased and coronary vasodilator reserve blunted in Duchenne and sarcoglycanopathy patients despite normal hyperemic myocardial blood flow. The reduction of coronary vasodilator reserve was due to an increased baseline myocardial blood flow. In Duchenne dystrophy, but not in sarcoglycanopathies, correction for cardiac workload normalized the coronary vasodilator reserve. In the latter patients, abnormal baseline myocardial blood flow could be due to vascular smooth muscle dysfunction.
Copyright 1999 John Wiley & Sons, Inc.