Abstract 11623: Strain by Echocardiography is Superior to Ejection Fraction in Detection of Reduced Exercise Capacity

Abstract

Background: Exercise capacity obtained by cardiopulmonary exercise testing (CPET) is considered a gold standard for estimating prognosis in patients with all grades of myocardial dysfunction. Global longitudinal strain (GLS) is shown to be more accurate than left ventricular (LV) ejection fraction (EF) for quantification of myocardial function. We explored the relationship between exercise capacity and myocardial function by LVEF and strain. We hypothesized that strain can detect reduced myocardial function in patients with reduced exercise capacity, with and without preserved LVEF.

Methods: CPET (by bicycle ergometry) detemined maximal oxygen uptake (VO2max) as a measure of exercise capacity. GLS was assessed by 2D speckle-tracking echocardiography in a 16 LV and 6 right ventricular (RV) segment model. LVEF was assessed by the Simpson biplane method.

Results: We included 100 patients with suspected or verified cardiovascular disease (mean age 56±12 years, 26% females, NYHA class 2.3±1.1 and LVEF 42±19%). In all patients LVEF, LV and RV GLS correlated to VO2max (R=0.64, -0.65 and -0.60 respectively, p <0.001 for all). Importantly, in patients with preserved LVEF (≥55%, n=34), only LV and RV GLS correlated to VO2max, (R=-0.52, p=0.002 and -0.44, p=0.01, respectively) while LVEF did not (R=0.23, p=0.19). By ROC analyses (n=100), LV GLS was better to identify patients with VO2max < 20 ml/kg/min compared to LVEF (AUC: 0.94 vs. 0.88, p=0.04). (Figure).

Conclusion: In general, all measurements of LV and RV functions were correlated with exercise capacity. LV GLS analyses, however, were superior in identifying patients with decreased exercise capacity, including patients with normal LVEF. Considering the strong relationship between exercise capacity and cardiac prognosis, evaluation of myocardial strain may help detect patients with poor prognosis, including those with mildly decreased myocardial function.