Determinants of forward pulmonary vein flow - An open pericardium pig model

OBJECTIVE To elucidate determinants of pulmonary venous (PV) flow. BACKGROUND Right ventricular (RV) systolic pressure (vis a tergo), left atr ial (LA) relaxation and left ventricular (LV) systole and relaxation (vis a fronte) have been suggested as determinants of the pulmonary venous (PV) a nterograde Doppler flow velocities, but their relative contributions to tho se flow velocities have not been quantified. METHODS We analyzed, by multiple regression analysis, the determinants of P V anterograde velocities in an open-pericardium, paced (70 and 90 beats/min ) pig model in which LA afterload was modified by creating LV regional isch emia (left anterior descending coronary artery constriction). We measured h igh fidelity LA, LV and RV pressures and Doppler flow velocities (epicardia l echocardiography). We calculated LV tau, LA relaxation (a through x press ure difference divided by time, normalized by a pressure), LA peak v throug h x and RV systolic through LA peak v (RVSP-v) pressure differences, LV eje ction fraction, long-axis shortening, stroke volume (LV outflow integral x outflow area) and LA four-chamber dimensions, Doppler transmitral and PV fl ow velocities and velocity-time integrals. RESULTS Left ventricular regional ischemia increased mildly LA y trough pre ssure (8 +/- 1 vs. 6 +/- 1 mm Hg, p = 0.001). Left ventricular stroke volum e (coefficient: 0.5 cm/ml, SE: 0.2, p = 0.005) and LA peak v pressure (coef ficient: -0.8 cm/mm Hg, SE: 0.3, p = 0.008) determined the PV total systoli c integral. Left atrial relaxation determined both PV early systolic peak v elocity and integral (coefficient: -0.8 cm/mm Hg, SE: 0.3, p = 0.04). Left atrial maxiumum area (coefficient: 2 cm(-1) SE: 0.7, p = 0.01) and RVSP-v ( coefficient: 0.1 cm/mm Hg, SE: 0.05, p = 0.03) determined the late systolic integral. The PV total systolic integral determined both PV early diastoli c peak velocity and integral (coefficient: 1.2, SE: 0.2, p = 0.001). CONCLUSIONS In an experimental model of LV acute ischemia of limited durati on, the main independent predictors of PV systolic anterograde flow velocit ies are LA relaxation and compliance (LA peak v pressure) and LV systole-al l vis a fronte factors. In the setting of mildly increased LA pressures, PV systolic flow (LA reservoir filling) is an independent predictor of PV ear ly diastolic flow (LA early conduit). (J Am Coll Cardiol 2000;35:1947-59) ( C) 2000 by the American College of Cardiology.