Michelena, Héctor I.

Abstract Aims To define the hitherto unknown aetiology/mechanism distributions of mitral regurgitation (MR) in the community and the linked clinical characteristics/outcomes. Methods and results We identified all isolated, moderate/severe MR diagnosed in our community (Olmsted County, MN, USA) between 2000 and 2010 and classified MR aetiology/mechanisms. Eligible patients (n = 727) were 73 ± 18 years, 51% females, with ejection fraction (EF) 49 ± 17%. MR was functional (FMR) in 65%, organic (OMR) in 32% and 2% mixed. Functional MR was linked to left ventricular remodelling (FMR-v) 38% and isolated atrial dilatation (FMR-a) 27%. At diagnosis FMR-v vs. FMR-a, vs. OMR displayed profound differences (all P < 0.0001) in age (73 ± 14, 80 ± 10, 68 ± 21years), male-sex (59, 33, 51%), atrial-fibrillation (28, 54, 13%), EF (33 ± 14, 57 ± 11, 61 ± 10%), and regurgitant-volume (38 ± 13, 37 ± 11, 51 ± 24 mL/beat). Dominant MR mechanism was Type I (normal valve-movement) 38%, Type II (excessive valve-movement) 25%, Type IIIa (diastolic movement-restriction) 3%, and Type IIIb (systolic movement-restriction) 34%. Outcomes were mediocre with excess-mortality vs. general-population in FMR-v [risk ratio 3.45 (2.98–3.99), P < 0.0001] but also FMR-a [risk ratio 1.88 (1.52–2.25), P < 0.0001] and OMR [risk ratio 1.83 (1.50–2.22), P < 0.0001]. Heart failure was frequent, particularly in FMR-v (5-year 83 ± 3% vs. 59 ± 4% FMR-a, 40 ± 3% OMR, P < 0.0001). Mitral surgery during patients’ lifetime was performed in 4% of FMR-v, 3% of FMR-a, and 37% of OMR. Conclusion Moderate/severe isolated MR in the community displays considerable aetiology/mechanism heterogeneity. Functional MR dominates, mostly FMR-v but FMR-a is frequent and degenerative MR dominates OMR. Outcomes are mediocre with excess-mortality particularly with FMR-v but FMR-a, despite normal EF incurs notable excess-mortality and frequent heart failure. Pervasive undertreatment warrants clinical trials of therapies tailored to specific MR cause/mechanisms.

Background: Echocardiographic quantitation of degenerative mitral regurgitation (DMR) is recommended whenever possible in clinical guidelines but is criticized and its scalability to routine clinical practice doubted. We hypothesized that echocardiographic DMR quantitation, performed in routine clinical practice by multiple practitioners, predicts independently long-term survival and thus is essential to DMR management. Methods: We included patients diagnosed with isolated mitral valve prolapse from 2003 to 2011 and any degree of mitral regurgitation quantified by any physician/sonographer in routine clinical practice. Clinical/echocardiographic data acquired at diagnosis were retrieved electronically. The end point was mortality under medical treatment analyzed by Kaplan-Meier method and proportional hazard models. Results: The cohort included 3914 patients (55% male) mean age (±standard deviation) 62±17 years with left ventricular ejection fraction 63±8% and median after routinely-measured effective regurgitant orifice area (EROA) [interquartile range], 19 [0–40] mm 2 . During follow-up (6.7±3.1 years), 696 patients died under medical management, and 1263 underwent mitral surgery. In multivariate analysis, routinely-measured EROA was associated with mortality (adjusted hazard ratio, 1.19; 95% confidence interval, 1.13–1.24; P <0.0001 per 10 mm 2 ) independently of left ventricular ejection fraction and end-systolic diameter, symptoms, and age/comorbidities. The association between routinely-measured EROA and mortality persisted with competitive risk modeling (adjusted hazard ratio, 1.15; 95% confidence interval, 1.10–1.20; P <0.0001 per 10 mm 2 ), or in patients without guideline-based class I/II surgical triggers (adjusted hazard ratio, 1.19; 95% confidence interval, 1.10–1.28; P <0.0001 per 10 mm 2 ) and in all subgroups examined (all P <0.01). Spline curve analysis showed that, compared with general population mortality, excess mortality appears for moderate DMR (EROA ≥20 mm 2 ), becomes notable at EROA ≥30 mm 2 , and steadily increases with higher EROA levels (eg, higher EROA levels beyond the 40 mm 2 threshold). Conclusions: Echocardiographic DMR quantitation is scalable to routine practice and is independently associated with clinical outcome. Routinely-measured EROA is strongly associated with long-term survival under medical treatment. Excess mortality versus the general population appears in the moderate DMR range and steadily increases with higher EROA. Hence, individual EROA values should be integrated into therapeutic considerations, in addition to categorical DMR grading.

Despite its high prevalence, little is known about mechanisms of mitral regurgitation in degenerative mitral valve disease apart from the leaflet prolapse itself. Mitral valve is a complex structure, including mitral annulus, mitral leaflets, papillary muscles, chords, and left ventricular walls. All these structures are involved in physiological and pathological functioning of this valvuloventricular complex but up to now were difficult to analyze because of inherent limitations of 2-dimensional imaging. The advent of 3-dimensional echocardiography, computed tomography, and cardiac magnetic resonance imaging overcoming these limitations provides new insights into mechanistic analysis of degenerative mitral regurgitation. This review will detail the contribution of quantitative and qualitative dynamic analysis of mitral annulus and mitral leaflets by new imaging methods in the understanding of degenerative mitral regurgitation pathophysiology.