Left atrial inflow propagation rate derived by transesophageal color M-mode echocardiography is a promising index of preload

Abstract

Background: Pulmonary capillary wedge pressure (PCWP) is a useful index of preload and an important determinant of cardiac function. Hypothesis: We postulated that the rate of blood propagating into the left atrium (LAIF-PR) would be a useful measure of PCWP in critically ill patients. Methods: Fifty-two critically ill patients (36 men/16 women) receiving mechanical ventilation were studied by multiplane transesophageal echocardiography (TEE). Left atrial inflow propagation rate was measured in systole and diastole as the slope of the color M-mode signal entering the left atrium from the right upper pulmonic vein. Results: Systolic and diastolic LAIF-PRs were feasible in 49 and 44 patients, respectively. Mean (± 1 standard deviation) LAIF-PR in systole was 40 ± 26 cm/s (range 11-132) and in diastole 34 ± 22 cm/s (range 5-102). Negative correlations with PCWP (mean 19 ± 9 mmHg; range 3-40) were good for LAIF-PR in systole (r = -0.71, standard error of estimate [SEE] = 6 mmHg; p<0.0001) and diastole (r= -0.71, SEE= 6 mmHg; p<0.0001). Mean ejection fraction was 52 ± 22% (range. 15-88) and cardiac output was 6.97 ± 3.52 l/min (range 2.26-17.93). Multivariate regression showed PCWP as the only independent predictor of systolic (p < 0.0001) and diastolic (p < 0.0001) LAIF-PR among age, heart rate, cardiac output, ejection fraction, or left atrial diameter. Conclusions: Left atrial inflow propagation rate derived by color M-mode TEE aligned with the right upper pulmonic vein is a promising new index of preload. Future studies addressing the determinants of LAIF-PR, such as left atrial compliance, are needed.