CMR Determination of Outcomes in Mitral Regurgitation
Can cardiac magnetic resonance (CMR) imaging-derived quantification of regurgitant volume and fraction identify patients with asymptomatic moderate to severe mitral regurgitation (MR) who progress to symptoms or other surgical indications?
This was a retrospective review of data from four centers (n = 109 subjects) of asymptomatic adults with moderate or severe chronic MR on transthoracic echocardiography. Patients with MR secondary to annular dilation or left ventricular dysfunction, other significant valvular disease, and those with clinical or angiographic evidence of coronary disease were excluded. Patients underwent CMR imaging using one of several vendors’ scanners and analysis software. The primary outcome was mitral valve repair or replacement for symptoms or conventional echocardiographic indications. Patients who underwent surgery for nonconventional indications were censored at the time of surgery.
A total of 109 patients were followed for a median of 1.6 years (interquartile range, 0.8-3.5 years). During this time, 25 patients (23%) underwent mitral valve repair or replacement after a median of 1.1 years due to symptoms (n = 19) or echocardiographic indications for surgery (n = 6). Regurgitant volume (p = 0.01) and regurgitant fraction (p = 0.01) were both independent predictors of development of indications for surgery. Regurgitant volume of >55 ml and regurgitant fraction of >40% maximized the c-index. While 95% of those with regurgitant volume ≤55 ml were free of symptoms or surgery at median follow-up of 1.6 years, by this time point, 46% of those with regurgitant volumes >55 ml had developed symptoms or indications for surgery. Echocardiography performed less well with many patients having regurgitant volume by CMR ≤55 ml despite severe grading on echocardiography (n = 28). These patients remained asymptomatic. Approximately one in three patients (30%) were reclassified by CMR compared with echocardiography. Echocardiography parameters were unable to separate subjects based on clinical outcome. Overall, quantification of MR performed better than chamber quantification or ejection fractions.
CMR-derived quantification of MR showed improved discriminatory capability for development of symptoms or surgical indications over echocardiography and gold-standard chamber dimensions by CMR imaging.
There is a growing body of literature supporting the application of CMR in the assessment of mitral valve disease. First, it has become clear that CMR-derived parameters of left ventricular dimensions and regurgitant volumes often differ from echocardiography and are generally more accurate. Second, CMR-derived parameters appear to have important prognostic value in terms of development of indications for surgery, as in this study. Other studies have demonstrated that CMR-derived parameters are also able to risk-stratify postoperative prognosis. It appears that CMR may have an important role in further risk-stratifying patients with moderate to severe MR on echocardiography.
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