Ventricular performance in relation to heart rate and AV delay at rest

The influence of heart rate (HR) and AV delay (AVD) on left ventricular haemodynamics was studied in 12 patients classified as having coronary heart disease (CHD), hypertensive heart disease (HHD), dilated cardiomyopathy (DCM) or who served as controls. Using the conductance catheter technique, haemodynamics were measured during pacing rates of 80 to 180 beat.min-1 at AV delays of 0 to 240 ms. A 3-D linear regression analysis of the data quantified the influence of HR and AVD in principle for each group. An increase in HR resulted in a rise in the cardiac index without changing ejection fraction in the control group only, but led to a decrease in these parameters in HHD and DCM; cardiac index remained constant in CHD. CHD patients frequently had a more pronounced left ventricular end-diastolic pressure (LVEDP) elevation with higher HR, whereas left ventricular end-diastolic volume (LVEDV) and stroke volume decreased. In patients with HHD, lengthening of the AVD resulted in an increase in LVEDV and a decrease in LVEDP and left ventricular end-systolic volume (LVESV) leading to a higher ratio of stroke volume to LVEDP than in the other subsets. In DCM, longer AVD also resulted in a higher SV/LVEDP ratio, but in contrast to HHD the influence of AVD variation on LVEDP and therefore on the LVEDV/LVEDP ratio was missing.