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Asymptomatic Severe Mitral Regurgitation
Mitral regurgitation (MR) may result from primary abnormalities of the mitral valve (MV) apparatus (primary or degenerative MR) or from left ventricular (LV) dysfunction and remodeling (functional or secondary MR). The current American College of Cardiology (ACC)/American Heart Association (AHA) guidelines recommend surgery in symptomatic patients with chronic severe MR; ACC/AHA stage D in all patients with primary (degenerative) MR and only in selected patients with secondary (functional) MR (those with persistent marked heart failure symptoms).
The severity of either primary or secondary MR is based on the presence of an effective regurgitant orifice area (EROA) 0.4 cm 2 or greater, regurgitant volume 60 mL or greater, and regurgitant fraction 50% or greater, which applies for both primary or secondary MR. One should keep in mind that in secondary MR, EROA and regurgitant volume can be lower because of the crescent shape of the flow convergence (when using the Proximal Isovelocity Surface Area (PISA) method) or low-flow conditions. Per the American Society of Echocardiography guidelines on valvular regurgitation, when multiple parameters are concordant, MR severity can be determined with high probability, especially for mild or severe MR.
Approach to Asymptomatic Severe Mitral Regurgitation
The paucity of high-quality studies in asymptomatic patients with chronic severe MR makes management controversial between watchful waiting versus early surgery. Indications for surgical treatment of MR are summarized in Table 99.1 . Historically, the defendants of the primum non nocere concept suggest that a watchful waiting strategy is reasonable given the overall low annual mortality rate in this group. Recent growing evidence (albeit consisting only of observational studies) shows better outcomes in surgically treated asymptomatic patients, specifically in the setting of flail leaflets when the operative mortality rate is low in experienced valve centers. One study has shown that in asymptomatic MR patients with normal ventricular function, the 5-year combined incidence of atrial fibrillation, heart failure, or cardiovascular death was 42% ± 8%.
TABLE 99.1
Indications for Surgery in Asymptomatic Severe Mitral Regurgitation
| ESC 2017 | ACC/AHA 2017 | |
|---|---|---|
| LV dysfunction (LVESD ≥45 mm and/or LVEF ≤60%) | Class I; LOE: B | |
| LV dysfunction (LVESD ≥40 mm and/or LVEF ≤60%) | Class I; LOE: B | |
| Preserved LVEF >60% and LVESD <45 mm with atrial fibrillation or pulmonary hypertension (PASP >50 mm Hg) | Class IIa; LOE: B | Class IIa; LOE: B |
| Preserved LVEF >60% and LVESD 40–44 mm when durable repair is likely, surgical risk is low, and repair is performed in a heart valve center with at least flail leaflet or significant LA dilatation (LA volume index ≥60 mL/m 2 ) | Class IIa; LOE: C | |
| Preserved LVEF >60% and LVESD <40 mm when successful and durable repair likelihood is >95% and low mortality | Class IIa, LOE: B | |
| Preserved LVEF >60% and LVESD <40 mm with a progressive increase in LV size or decrease in EF on serial imaging studies | Class IIa; LOE: C |
ACC, American College of Cardiology; AHA, American Heart Association; EF, ejection fraction; ESC, European Society of Cardiology; LA, left atrial; LV, left ventricular; LVESD, left ventricular end-systolic diameter; LVEF, left ventricular ejection fraction; LOE, level of evidence; PASP, pulmonary artery systolic pressure.
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