Assessment of Stress-induced Pulmonary Interstitial Edema by Chest Ultrasound During Exercise Echocardiography and its Correlation with Left Ventricular Function

Abstract

Ultrasound lung comet images (ULC) are useful for the noninvasive assessment of extravascular lung water (EVLW). We investigated the modification of EVLW, its relation to indices of left ventricular systolic and diastolic function, and noninvasively determined pulmonary capillary wedge pressure (PCWP) (PCWP = 1.24 ratio of early diastolic mitral inflow velocity to early diastolic velocity of the mitral annulus [E/Em] + 1.9) at rest and its variation during exercise echocardiography. A total of 72 patients (mean age 66.4 +/- 8.4 years) with mean ejection fraction of 41.2 +/- 14.4% underwent symptoms-limited exercise echocardiography. The sum of the ULC yielded a score of EVLW. The ULC increased significantly from baseline to postexercise (5.9 +/- 14.9 vs 11 +/- 20.7, P = .0001). Positive linear correlations were found between baseline ULC score and baseline ejection fraction (r = -0.37, P = .002), systolic pulmonary artery pressure (r = 0.69, P = .0001), E/Em (r = 0.70, P = .0001), and estimated PCWP (r = 0.69, P = .0001). The variation between postexercise and baseline ULC score correlated significantly with the variation between peak stress and rest PCWP (r = 0.62, P = .0001), systolic pulmonary artery pressure (r = 0.44, P = .0001), wall-motion score index (r = 0.30, P = .01), and peak stress E/Em (r = 0.71, P = .0001), whereas no significant correlations were found between variations of ULC score and ejection fraction. This study shows that ULC represents a simple way to assess the presence of excess EVLW. Increased EVLW is associated with estimated PCWP and indices of left ventricular systolic and diastolic dysfunction. The additional exercise-induced increase of PCWP, the worsening of left ventricular diastolic function, and extensive wall-motion abnormalities correlate with variations of EVLW.