Left ventricular relaxation in dilated cardiomyopathy: relation to loading conditions and regional nonuniformity

Department of Internal Medicine, Faculty of Medicine, Kyoto University, Japan.

OBJECTIVES. The purpose of the present study was to investigate how loading conditions and regional nonuniformity affect left ventricular relaxation in dilated cardiomyopathy. BACKGROUND. Left ventricular relaxation is impaired in dilated cardiomyopathy. It has been suggested that relaxation abnormality is related to loading conditions and regional nonuniformity in the diseased heart. METHODS. Left ventriculography with simultaneous pressure manometry was performed in 10 patients with dilated cardiomyopathy before and during nitroprusside infusion. Ten normal subjects served as a control group. Left ventricular hemodynamics, regional wall motion (assessed by the area method) and regional wall stress (Janz method) were analyzed. RESULTS. When compared with control subjects, the patients with dilated cardiomyopathy had a reduced left ventricular ejection fraction (p < 0.01) and prolonged relaxation time constants (p < 0.01). Left ventricular wall motion was both hypokinetic and asynchronous in the patient group. In addition, systolic regional wall stress was significantly greater, the time to peak wall stress was longer and the regional myocardial relaxation time constant was greater for each ventricular area assessed in the patient group (each p < 0.01). Administration of nitroprusside reduced left ventricular pressure and increased ejection fraction in the 10 patients with dilated cardiomyopathy. For each region, systolic regional wall stress and the time to peak wall stress decreased, and both regional hypokinesia and asynchrony lessened. These changes in loading conditions and regional nonuniformity were accompanied by an improvement in both regional and global ventricular relaxation that was significant, particularly during the early to midrelaxation phase when regional asynchrony was greatest. CONCLUSIONS. These results suggest that myocardial relaxation is sensitive to loading conditions and regional nonuniformity in dilated cardiomyopathy and that load reduction can improve both relaxation and systolic performance of the left ventricle.

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