Lung Ultrasound Density Score Index Performed With Cardiopulmonary Exercise Echocardiography Testing Is Associated With Impaired Exercise Capacity

Abstract

Background

Exercise stress echocardiography and cardiopulmonary exercise testing (CPET) are frequently used for the evaluation of patients with dyspnea and exercise intolerance. Lung ultrasound (LUS) has been shown to increase the prognostic utility of stress echocardiography. Integration of LUS into stress echocardiography for undifferentiated ambulatory patients undergoing clinically indicated simultaneous CPET has not been previously evaluated.

Objectives

To determine whether LUS, when performed immediately before and after exercise testing, is associated with reduced exercise capacity, as defined by peak oxygen consumption ($\dot{V}$O_2peak), in patients undergoing clinically indicated stress echocardiography with CPET.

Methods

Lung ultrasound performed pre- and postexercise in a retrospective cohort of 261 consecutive patients with normal left ventricular ejection fraction undergoing simultaneous stress echocardiography and CPET. Lung ultrasound was performed in 4 lung zones, and a semiquantitative assessment of B-line burden was accomplished using the novel LUS density score index (LUDSI).

Results

Lung ultrasound was feasible in 100% of patients pre- and postexercise. An LUDSI ≥0.5 was associated with impaired exercise capacity ($\dot{V}$O_2peak of <90% predicted) at rest (area under the curve [AUC] = 0.75) and poststress (AUC = 0.76) after adjusting for age and sex. The association of LUDSI ≥0.5 and impaired exercise capacity was only incrementally improved with the integration of diastolic function (E/e’) performed at rest (AUC = 0.77) and poststress (AUC = 0.78).

Conclusions

The LUDSI is a simple and highly feasible measure of B-line burden that can be performed pre- and postexercise. A LUDSI ≥0.5 was associated with impaired exercise capacity in patients with normal left ventricular ejection fraction undergoing simultaneous stress echocardiography and CPET.