INFLUENCE OF HEART-RATE AND LEFT ATRIAL PRESSURE ON PULMONARY VENOUS FLOW PATTERN IN DOGS

In six open-chest anesthetized dogs we investigated the effect of heart rate (HR) on the relationship between left atrial pressure (LAP) and pulmonary venous flow (Q(PV)). Q(PV) was measured by ultrasonic transit time during volume loading and right atrial pacing. Consistent with previous studies, we found a negative correlation between LAP and mean flow rate during atrial systole divided by mean flow rate in the R-R interval. However, this relationship was shifted upward by tachycardia. The Q(PV) maximum amplitude divided by mean flow rate in the R-R interval increased with loading but decreased with tachycardia. Mean flow rate during ventricular systole divided by mean flow rate during the R-R interval increased with both loading and tachycardia. Regression coefficients for HR and LAP as predictors of these indexes were all significantly different from zero (P = 0.0001). We conclude that HR significantly influences the relationship between the Q(PV) pattern and LAP. This could be a limitation of the pulmonary venous flow pattern as an indicator of left ventricular diastolic function.