Strain Echocardiography and Functional Capacity in Asymptomatic Primary Mitral Regurgitation With Preserved Ejection Fraction

Abstract

Background: The potential additive utility of baseline resting left ventricular global longitudinal strain (LV-GLS) and exercise stress testing in risk stratification of patients with significant mitral regurgitation (MR) has not been studied.

Objectives: The goal of this study was to determine whether resting LV-GLS and exercise testing provide incremental prognostic utility in asymptomatic patients with ≥3+ primary MR and preserved left ventricular ejection fraction.

Methods: Between 2000 and 2011, resting and exercise echocardiography data, Society of Thoracic Surgeons (STS) scores, and death were recorded in 737 patients (mean age 58 ± 13 years; 68% men).

Results: Coronary artery disease and flail leaflet were seen in 10% and 28% of patients, respectively. STS score, resting left ventricular ejection fraction, mitral effective regurgitant orifice, resting right ventricular systolic pressure (RVSP), exercise metabolic equivalents (METs), and percentage of age-/sex-predicted METs were 1.5 ± 1%, 62 ± 2%, 0.45 ± 0.2 cm², 31 ± 12 mm Hg, 9.8 ± 3, and 115 ± 27, respectively. Median LV-GLS was -21.7%. Within 3 months (interquartile range: 1 to 15 months), 65% underwent mitral valve surgery. At 8.3 ± 3 years, 64 (9%) patients died (0% 30-day post-operative deaths). On multivariable Cox survival analysis, higher STS score (hazard ratio [HR]: 1.14), more abnormal resting LV-GLS (HR: 1.60), higher baseline RVSP (HR: 1.35), and lower percentage of age-/sex-predicted METs (HR: 1.13) were associated with higher mortality, whereas mitral valve surgery (HR: 0.82) was associated with improved survival (all p < 0.01). Addition of predicted METs and resting LV-GLS to STS, resting RVSP, left ventricular end-systolic dimension, and mitral effective regurgitant orifice increased the C-statistic for longer-term mortality from 0.61 to 0.69 and 0.78, respectively (all p < 0.01). On quadratic spline analysis, the risk of death progressively increased as resting LV-GLS worsened below -21%.

Conclusions: Reduced exercise capacity and worsening resting LV-GLS were associated with mortality, providing additive prognostic utility.

Keywords: global longitudinal strain; outcomes; post-exercise echocardiography.