Left ventricular contractile reserve in asymptomatic primary mitral regurgitation

Abstract

There are very few data regarding the assessment and prognostic value of left ventricular contractile reserve (LVCR) in asymptomatic patients with primary mitral regurgitation (MR). We aimed to quantify LVCR and to evaluate its usefulness for risk stratification in asymptomatic patients with primary MR. Comprehensive resting and exercise (EX) transthoracic echocardiography, including two-dimensional speckle tracking quantification, were performed in 115 consecutive asymptomatic patients with ≥ moderate degenerative MR and no LV dysfunction/dilatation. Left ventricular contractile reserve was defined as an EX-induced increase in LV ejection fraction (LVCR(LVEF)) ≥ 4% or in LV global longitudinal strain (LVCR(GLS)) ≥ 2%. LVCR(LVEF) was present in 54 patients (47%) and LVCR(GLS) in 58 (50%). The brain natriuretic peptide (BNP) level was significantly correlated with EX-induced changes in GLS (r = 0.45, P < 0.0001), but not in LVEF (r = 0.09, P = 0.31). Patients with no LVCR(GLS) had significant lower 3-year cardiac event-free survival (42 ± 8 vs. 69 ± 7%, P = 0.0008). In contrast, there was no significant difference in outcome regarding to the presence or absence of LVCR(LVEF) (60 ± 7 vs. 51 ± 8%, P = 0.40). The multivariable Cox proportional hazard model showed that the absence of LVCR(GLS) was a strong independent predictor of cardiac events (HR = 2.27, 95% CI: 1.05-4.76, P = 0.037), even after adjustment for Ex-echo variables and BNP level. The association between LVCR(GLS) and outcome remained significant (HR = 1.6, 95% CI: 1.1-2.3, P = 0.01) after further adjustment for the resting echocardiographic parameters included in the ESC Guidelines. In asymptomatic primary MR, LVCR seems to be better assessed using EX-induced changes in LV myocardial longitudinal function rather than in LVEF. In patients with preserved LV function, the absence of LVCR is independently associated with two-fold increase in risk of cardiac events. Left ventricular contractile reserve may be useful to improve risk stratification and clinical decision-making in these patients.