Incremental Prognosis by Left Atrial Functional Assessment: The Left Atrial Coupling Index in Patients With Floppy Mitral Valves

Abstract

Background Emerging data suggest important prognostic value to left atrial (LA) characteristics, but the independent impact of LA function on outcome remains unsubstantiated. Thus, we aimed to define the incremental prognostic value of LA coupling index (LACI), coupling volumetric and mechanical LA characteristics and calculated as the ratio of left atrial volume index to tissue Doppler imaging a′, in a large cohort of patients with isolated floppy mitral valve. Methods and Results All consecutive 4792 patients (61±16 years, 48% women) with isolated floppy mitral valve in sinus rhythm diagnosed at Mayo Clinic from 2003 to 2011, comprehensively characterized and with prospectively measured left atrial volume index and tissue Doppler imaging a′ in routine practice, were enrolled, and their long‐term survival analyzed. Overall, LACI was 5.8±3.7 and was <5 in 2422 versus ≥5 in 2370 patients. LACI was independently higher with older age, more mitral regurgitation (no 3.8±2.3, mild 5.1±3.0, moderate 6.5±3.8, and severe 7.8±4.3), and with diastolic (higher E/e′) and systolic (higher end‐systolic dimension) left ventricular dysfunction (all P ≤0.0001). At diagnosis, higher LACI was associated with more severe presentation (more dyspnea, more severe functional tricuspid regurgitation, and elevated pulmonary artery pressure, all P ≤0.0001) independently of age, sex, comorbidity index, ventricular function, and mitral regurgitation severity. During 7.0±3.0 years follow‐up, 1146 patients underwent mitral valve surgery (94% repair, 6% replacement), and 880 died, 780 under medical management. In spline curve analysis, LACI ≥5 was identified as the threshold for excess mortality, with much reduced 10‐year survival under medical management (60±2% versus 85±1% for LACI <5, P <0.0001), even after comprehensive adjustment (adjusted hazard ratio, 1.30 [95% CI, 1.10–1.53] for LACI ≥5; P =0.002). Association of LACI ≥5 with higher mortality persisted, stratifying by mitral regurgitation severity of LA enlargement grade (all P <0.001) and after propensity‐score matching ( P =0.02). Multiple statistical methods confirmed the significant incremental predictive power of LACI over left atrial volume index (all P <0.0001). Conclusions LA functional assessment by LACI in routine practice is achievable in a large number of patients with floppy mitral valve using conventional Doppler echocardiographic measurements. Higher LACI is associated with worse clinical presentation, but irrespective of baseline characteristics, LACI is strongly, independently, and incrementally determinant of outcome, demonstrating the crucial importance of LA functional response to mitral valve disease.

Primary Atriopathy in Mitral Valve Prolapse: Echocardiographic Evidence and Clinical Implications

“…28 Consequently, while LA volume and the parameters derived from LA volume are reliable indices of LA function, they may not be able to capture the entirety of LA mechanics. 13 The interdependency of LA and LV strains observed in our study has been previously reported. 29 Our results suggest that the contribution of MAD to LA strain is independent of LV longitudinal function.…”

Watchful surgery in asymptomatic mitral valve prolapse

“…Left atrial coupling index (LACI) (represented by the ratio between LA volume index and tissue Doppler myocardial velocity during atrial contraction), emerged as a strong and independent determinant of the outcome under non-surgical treatment. LACI ≥ 5 was identified as a threshold for excess mortality ( 42 ). The novel finding that LA functional assessment is a meaningful marker of clinical outcomes underscores the need to standardize the atrial function assessment beyond morphology.…”

“…LA function provides information (40). Among asymptomatic patients with preserved LVEF, both peaks of atrial longitudinal strain and reservoir strain may predict adverse outcomes (41). Left atrial coupling index (LACI) (represented by the ratio between LA volume index and tissue Doppler myocardial velocity during atrial contraction), emerged as a strong and independent determinant of the outcome under nonsurgical treatment.…”

The Left Atrium

“… 4 Such individual variability in LA response to MR remains poorly defined in term of genetic mechanisms 5 but is remarkable in that LA dilatation severity is highly predictive of long-term outcome, 6 independently of all the baseline characteristics, particularly of those linked to LA enlargement. 7 Furthermore, the intrinsic LA function is now measurable and is even more strongly associated with long-term outcome than LA enlargement, in all types and degrees of MR. 8 , 9 Thus, LA characteristics are truly crucial to consider, particularly in patients with MR.…”

“… 21 Although LA volume measurements are now widely accepted, LA functional assessment and the degree of fibrosis affecting the atrial wall warrant consistent evaluation. 8 , 9 , 22 A-FMR represents a sizable proportion of MR, 13 the most frequent valve disease affecting the population, 23 and the transition from LA enlargement to FMR warrants analysis in large cohorts. A-FMR is a troubling entity with modest regurgitant volume and a small left ventricle of generally normal function but nevertheless is associated with excess mortality and high incidence of heart failure.…”