Background and purpose: Cardiac performance can be characterized in terms of the relative duration of systole and diastole. In pediatric patients with dilated cardiomyopathy (DCM), a disproportionate shortening of left ventricular diastole was observed. The present study was intended to reproduce these findings in an adult patient group and to evaluate exercise-related changes of both time intervals.
Patients and methods: Exercise radionuclide angiography was used in 61 patients with DCM NYHA (New York Heart Association) stage II-III. The phases of the cardiac cycle were derived from a radionuclide time-activity curve with high temporal resolution. The control group consisted of 26 patients referred for ventricular function assessment with radionuclide angiography before cardiotoxic cancer treatment.
Results: When the duration of systole was expressed as the product of systolic time and heart rate, DCM patients exhibited a significant increase in left ventricular systolic time at rest (23.9 vs. 21.5 s/min; p = 0.006) and during peak exercise (29.2 vs. 26.7 s/min; p = 0.01). The prolongation of left ventricular systole at peak exercise was evident, although the peak heart rate was significantly lower in the patient group than in the control group (118 vs. 127/min; p = 0.04). In DCM patients the diastolic time loss per beat was further quantified using a regression equation obtained from the healthy control group. A significant shortening of left ventricular diastolic time was confirmed during peak exercise. Furthermore, a progressive loss in diastolic time per beat from rest to peak exercise was noted.
Conclusion: Cardiac cycle abnormalities of patients with DCM are characterized by a prolongation of left ventricular systole and an abnormal shortening of left ventricular diastole. The systolic-diastolic mismatch is accentuated during exercise and has the potential to impair the cardiac reserve in these patients by restricting ventricular filling and perfusion.