Dynamic determinants of left ventricular diastolic pressure volume relations in man

Left ventricular (LV) diastolic pressure (P), volume (V), and rate of change of volume (dV/dt) were determined at 16.7 msec intervals in 17 patients (stimultaneous micromanometer and signel plane volume angiography). Four patients had mitral stenosis with atrial fibrillation and 13 patients (3 normal, 2 congestive cardiomyopathy, 3 LV hypertrophy, and 5 coronary artery disease) were in normal sinus rhythm. Maximum early diastolic filling rates (max dV/dt) in the normal and cardiomyopathy patients were similar and ranged from 269 to 370 cc/m²/sec; in coronary artery disease and LV hypertrophy, max dV/dt ranged from 197 to 290 cc/m²/sec and 213 to 255 cc/m²/sec respectively; in mitral stenosis, max dV/dt ranged from 215 to 270 cc/m²/sec. The peak filling rate during atrial systole ranged from 60 to 240 cc/m²/sec in the 13 patients with sinus rhythm. The instantaneous diastolic PV data were fit by an exponential equation (P = be(KV))and the PV relation throughout diastole was represented by the best fit line. The rate constant (k) in the equation was highest in the patient with idiopathic hypertrophic subaortic stenosis and lowest in those with large dilated hearts. In mitral stenosis with atrial fibrillation the fit on the equation to the PV data appeared better than in the patients with normal sinus rhythm. Peak ventricular filling rate during atrial systole varied directly with LV volume distensibility at the onset of atrial systole (r = 0.64). Data suggest that dynamic mechanical properties of the LV influence the diastolic PV relations and that pressure 'deviations' (ΔP) from the best fit line during atrial systole may be related to viscous drag. In a given ventricle the velocity dependence of AP appears to be modified by the volume distensibility of the ventricle. Variable rates of filling may preclude the assumption of an exponential relation between P and V throughout diastole and therefore may limit estimates of diastolic distensibility or compliance which rely on such an assumption.