Circ: Size of left atrium is mortality predictor in mitral regurgitation

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In mitral regurgitation caused by flail leaflets, left atrium with a diameter of 55 mm or more is associated with increased mortality under medical treatment, independent of the presence of symptoms or left ventricular dysfunction, according to a multicenter study published in the September issue of Circulation: Cardiovascular Imaging.

Left atrium enlargement is common in organic mitral regurgitation (MR) and is an emerging prognostic indicator, according to the study; however, outcome implications of left atrium enlargement have not been analyzed in the context of routine clinical practice.

“Guidelines recommend mitral surgery in patients with MR and overt symptoms, left ventricular dysfunction, pulmonary hypertension, or atrial fibrillation because these patients are at high risk of death and cardiac events under medical treatment,” Dan Rusinaru, MD, of the University Hospital Amiens in Amiens, France, and his fellow Mitral Regurgitation International Database (MIDA)  investigators wrote. “However, patients with ‘guideline surgical indications’ may incur excess mortality even after successful surgery, and therefore, additional markers of risk are needed to better identify high-risk groups and define the optimal timing of surgery.

“Left atrium enlargement and remodeling in various cardiac conditions are mainly the consequence of volume overload, as in valvular regurgitation or pressure overload reflecting increased left ventricular filling pressures," they continued.

The MIDA registry enrolls patients with organic MR due to flail leaflets, diagnosed in routine clinical practice, in five U.S. and European centers.

Rusinaru and colleagues investigated the relation between left atrium diameter and mortality under medical treatment and after mitral surgery in 788 patients in sinus rhythm (average age, 64 years; median left atrium, 48 mm).

Left atrium diameter was independently associated with survival after diagnosis. Compared with patients with left atrium of less than 55 mm, those with a left atrium of 55 mm or greater had lower eight-year overall survival, the study authors reported. In fact, a left atrium of 55 mm or greater independently predicted overall mortality and cardiac mortality under medical treatment.

They also noted that the association of a left atrium of 55 mm or greater and mortality was consistent in subgroups. Similar excess mortality associated with a left atrium of 55 mm or greater was observed in both asymptomatic and symptomatic patients.

In patients who underwent mitral surgery, a left atrium of 55 mm or greater had no impact on postoperative outcomes, Rusinaru and colleagues found. Mitral surgery was associated with greater survival benefit in patients with a left atrium of 55 mm or greater, compared with a left atrium of less than 55 mm.

“Our results show that left atrium diameter is a marker of increased risk of death under conservative treatment and that it does not affect postoperative survival of patients undergoing surgery,” they wrote. “The evaluation of left atrium size should therefore be systematically performed and considered when discussing surgery together with left ventricular dimensions, ejection fraction and symptoms.”

Left atrium diameter represents “a simple and easily obtainable echocardiographic measurement that might improve risk stratification in chronic organic mitral regurgitation,” Rusinaru and colleagues concluded.