Abstract 11380: Reproducibility and Diagnostic Potential of Pulmonary Transit Time Derived from Contrast Echocardiography

Abstract

Background: Pulmonary transit time (PTT) may reflect global cardiopulmonary function and thus could be useful in practice. PTT can be measured using contrast-echocardiography, but limited clinical data are available. Hypothesis: We hypothesize that PTT measured by contrast-echocardiography is reproducible, correlates with echocardiographic measures of left and right ventricular (LV, RV) function, and is prolonged in patients with ventricular dysfunction compared to normals.

Methods: In patients undergoing clinically indicated contrast-echocardiography, intensity-time curves were generated by the passage of contrast through standardized regions of interest within the RV and left-atrium (LA). PTT was measured as the time between peaks of the RV and LA curves. To assess reproducibility, contrast injection was repeated after complete washout of the initial dose. Reproducibility was quantified by correlating the initial and follow-up measurements. The relationships between PTT and echocardiographic parameters were evaluated using linear regression.

Results: PTT was measured in 13 patients, 6 of whom had abnormal LV and/or RV function and 10 of whom had repeat measurements. The correlation between pairs of PTT measurements was strong (Figure). PTT correlated with LV ejection fraction (r = -0.86; p < 0.001) and LA volume index (r = 0.71, p = 0.007). There was a trend toward correlation with E/E’ (r = 0.63, p = 0.07). PTT also correlated with RV function as measured by the velocity of the lateral tricuspid annulus (S’; r = -0.77; p = 0.01) and tricuspid annular excursion (TAPSE; r = -0.61, p = 0.03). PTT was prolonged in those with ventricular dysfunction compared to normals (7.5 ± 1.8 vs. 4.1 ± 0.6 s; p = 0.004).

Conclusions: PTT measured by contrast-echocardiography is highly reproducible and can identify abnormalities in left and right ventricular function. Further study of this technique in the evaluation of the RV-pulmonary vascular circuit appears reasonable.