Opposite determinants of left atrial (LA) systolic inflow (during the LA reservoir phase) have been proposed: right ventricular (RV) systolic pressure transmitted through the pulmonary circulation (vis a tergo) as opposed to LA relaxation and left ventricular (LV) systole (vis a fronte). We quantified the roles of vis a tergo and vis a fronte as determinants of the pulmonary venous LA inflow pattern (pulsed Doppler echo) in open pericardium pigs, paced at 70, 90 b/min (right atrium), at baseline and after acute occlusion of the left coronary artery to modify LA and LV loading conditions. We measured high fidelity LA, LV, and RV pressures, and Doppler flow velocities (epicardial echocardiography). We calculated LA relaxation (a-x pressure difference divided by time, normalized by a pressure); LA peak v-x trough and RV systolic-LA peak v (RVSP-v) pressure differences; LA mean pressure; LV ejection fraction, long-axis shortening, stroke volume (LV outlow tract area x flow integral), and LA 4-chamber maximum and minimum areas; Doppler pulmonary venous flow velocities and velocity-time integrals. We identified the independent predictors of LA inflow with multiple regression analysis (accounting for between pig differences using effects-coded dummy variables). LV stroke volume (coefficient 0.5 cm/ml, SE 0.2; p = 0.005) and LA peak v pressure (coefficient -0.8 cm/mmHg, SE 0.3; p = 0.008) determined pulmonary venous total systolic integral. LA relaxation determined both pulmonary venous early systolic peak velocity and integral (coefficient -0.8 cm/mmHg, SE 0.3; p = 0.04). LA maximum area (coefficient 2 cm-1, SE 0.7; p = 0.01) and RVSP-v (coefficient 0.1 cm/mmHg, SE 0.05; p = 0.03) determined late systolic integral. In conclusion, in our animal model, the strongest independent predictors of systolic LA inflow are related to LA function (relaxation and compliance) and LV systole.
|Number of pages||6|
|Publication status||Published - 1999|
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Radiology Nuclear Medicine and imaging