Abstract
The purpose of this study is to evaluate the left ventricular contractility and diastolic compliance in experimental chronic volume overloading. After cardiac catheterization studies obtaining control data, dogs were divided into 2 groups. An infrarenal aorto-caval fistula was created in 14 dogs (Group I) and a left subclavian arterial-left atrial shunt was constructed in 7 dogs (Group II). These 2 groups were further divided into 7 subgroups according to the time of data acquisition.
Results in both groups showed that the left ventricular end-diastolic pressure (LVEDP), end-diastolic volume (LVEDV), and end-diastolic volume index (LVEDVI) increased in the postshunt groups compared with the preshunt groups. In a subgroup (Group Ic) in which data were obtained 58±11 days after creation of the infrarenal aorto-caval fistula, the max dP/dt, maximal contractile element velocity at zero load (Vmax), peak measured contractile element velocity (Vpm), ejection fraction (EF), and mean velocity of circumferential fiber shortening (mean VCF) decreased significantly from 3680mmHg/sec, 1.08ML/sec, 0.90ML/sec, 0.65 and 2.52circ/sec in the preshunt group to 2970mmHg/sec, 0.94ML/sec, 0.70ML/sec, 0.57 and 1.74circ/sec, respectively. On the other hand, values of these indices did not decrease but increased in animals of the left subclavian arterial-left atrial shunt in the postshunt groups (Groups IIb, IIc), although the differences revealed no statistical significance.
Since no single index of ventricular compliance has been accepted as standard, left ventricular distensibility was assessed by using 5 formulae. ΔV/ESV/ΔP decreased significantly from 0.056mmHg-1 in the preshunt group (Group Ia) to 0.027 and 0.025mmHg-1 in postshunt groups (Groups Ic, Id). Although the diastolic compliance decreased in Group I, it showed no variation in Group II.
