Disproportionate shortening of diastolic time and cardiac performance in asymptomatic patients with aortic regurgitation.

BACKGROUND AND AIM OF THE STUDY: Exercise-induced abnormalities of the systolic-diastolic phase proportion and their impact on hemodynamic variables have been investigated only minimally in asymptomatic patients with chronic aortic regurgitation (AR). METHODS: A group of 33 asymptomatic patients with severe AR and preserved left ventricular (LV) systolic function was studied during incremental exercise, using a combined hemodynamic-radionuclide angiographic approach. The phases of the cardiac cycle were derived with high temporal resolution from the LV time-activity curve. The loss of diastolic time per beat (LDT) was quantified using a regression equation obtained from a healthy control group (n=26). Based on the median LDT at peak exercise, patients were allocated to two groups with LDT < or = 12.4 ms (group A) and LDT > 12.4 ms (group B). RESULTS: At peak exercise the relative duration of LV diastole was significantly shorter in AR patients than in controls (31.4 +/- 3.0 versus 33.1 +/- 2.4 s/min; p = 0.02) and a significant LDT (12.1 +/- 19 ms; p = 0.003) was observed. Group A patients had a higher peak cardiac output (9.2 +/- 2.0 versus 7.4 +/- 2 l/min/m2; p < 0.03), a longer exercise duration (18 +/- 5 min versus 13 +/- 6 min; p < 0.02) and a lesser extent of mean pulmonary artery pressure rise (27 +/- 10 versus 34 +/- 12 mmHg; p = 0.03) than group B patients. CONCLUSION: Cardiac exercise performance in asymptomatic patients with AR is influenced not only by the ability of the cardiovascular system to favorably redistribute total stroke volume, but also to handle volume overload without changing the systole and diastole phase proportions.

Loss of diastolic time as a mechanism of exercise-induced diastolic dysfunction in dilated cardiomyopathy.

BACKGROUND: Cardiac performance can be characterized in terms of the relative duration of left ventricular systole and diastole. Little is known about exercise-induced abnormalities of the systolic-diastolic phase proportion and its impact on hemodynamic variables in patients with idiopathic dilated cardiomyopathy (IDCM). METHODS: The phases of the cardiac cycle were derived with high temporal resolution from the left ventricular time-activity curve simultaneous with hemodynamic measurements. In patients with IDCM, the loss of diastolic time (LDT) per beat was quantified using a regression equation obtained from a healthy control group (n = 26). According to the median LDT at peak exercise, patients were divided into 2 subgroups: subgroup A with an LDT 22 milliseconds (n = 27). RESULTS: The relative duration of left ventricular systole was increased in patients with IDCM during peak exercise compared to healthy subjects (29.3 vs 26.7 s/min, P < .02). This abnormality translated into a significant LDT when observed, and predicted values of diastolic time were compared. Subgroup B patients had a higher increment in mean pulmonary capillary wedge pressure but a smaller increase in stroke volume index from rest to peak exercise (14.3 vs 8.6 mm Hg [P = .007] and 12.5 vs 7.2 mL/m(2) [P = .04]) compared to subgroup A patients. CONCLUSION: An abnormal shortening of diastolic time during exercise can restrict left ventricular filling to an extent that is sufficient to limit left ventricular stroke volume reserve and to cause pulmonary congestion.