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Background-Depressed myocardial blood flow (MBF) has been reported in dilated cardiomyopathy. The aim of this study was to investigate whether MBF impairment is an independent predictor of prognosis in patients with idiopathic left ventricular (LV) dysfunction. Methods and Results-Sixty-seven patients (52 male, mean age 52Ϯ12 years) with different degrees of idiopathic LV systolic dysfunction (average LV ejection fraction, 0.34Ϯ0.10; range, 0.07 to 0.49) were prospectively enrolled. Thirty-four subjects (51%) had no history of heart failure symptoms at enrollment (NYHA class I). All patients underwent clinical and functional evaluation and a PET study to measure absolute MBF at rest and after intravenous dipyridamole. During a mean follow-up of 45Ϯ37 months, 24 patients had major cardiac events, including cardiac death in 8 and development or progression of heart failure in 16 patients. Multivariate regression analysis (Cox proportional hazards model) revealed heart rate ( 2 11.06, PϽ0.001), LV end-diastolic dimension ( 2 11.73, PϽ0.001), and dipyridamole MBF ( 2 11.04, PϽ0.001) as independent predictors of subsequent cardiac events. Dipyridamole MBF Յ1.36 mL ⅐ min Ϫ1 ⅐ g Ϫ1 was associated with an increase in the relative risk of death, development, or progression of heart failure of 3.5 times over other more common clinical and functional variables. Conclusions-The present study demonstrates that severely depressed MBF is a predictor of poor prognosis in patients with idiopathic LV dysfunction independently of the degree of LV functional impairment and of the presence of overt heart failure.

In patients with DCM without overt heart failure, myocardial perfusion is impaired both at rest and in response to vasodilating stimuli. The abnormalities in vasodilating capability can be present despite normal hemodynamics; progression of the disease is associated with more depressed myocardial perfusion.