A quantitative analysis of reservoir function of the human pulmonary "venous" system for the left ventricle

By definition, the pulmonary "venous" system consists of the pulmonary veins and the left atrium. The stiffness of the pulmonary "venous" (P'V') system and the left ventricle (LV) at the end of the slow filling period (at the point of pre-a) were estimated sequentially in a total of 26 patients, divided into a control group and mitral stenosis (MS), angina pectoris (AP), hypertrophic cardiomyopathy (HCM) groups. The stiffness (delta P/delta V) of the P'V' system was estimated from the pulmonary artery wedge (PAW) pressure tracings and the stroke volume. The stiffness (dP/dV) of LV was obtained from the pressure-volume (P-V) relationship of LV with a model of P = beaV. The present study is aimed primarily at obtaining factual information. The stiffness of the P'V' system was 0.063 +/- 0.022 mmHg/ml (mean +/- SD) in the control group and 0.052 +/- 0.006 mmHg/ml in the HCM group (p greater than 0.1). The stiffness of LV in diastole was 0.091 +/- 0.016 mmHg/ml in the control group and 0.199 +/- 0.056 mmHg/ml in the HCM group (p less than 0.01). The ratio of the stiffness of LV in diastole to that of the P'V' system was 1.6 +/- 0.6 in the control group and 3.8 +/- 0.7 in the HCM group. The volume elastic constant (a) of the P'V' system was 0.008 +/- 0.005 ml-1 in the control group and the values of (a) occupied a range of 0.007 to 0.008 ml-1 in the remaining 3 groups of patients. The values of (a) of LV were 0.011 +/- 0.004 ml-1 in the control group and 0.022 +/- 0.007 ml-1 in the HCM group (p less than 0.01). The present study suggests that the P'V' system is usually 2 to 3 times more complaint than LV in diastole. On the other hand, the P'V' system remained compliant in spite of the decreased compliance of LV in diastole in the HCM group, maintaining the reservoir function with which pulmonary edema is prevented.