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Echo vs. MRI Assessment of Mitral Regurgitation | Journal Scan
Study Questions:
How do echocardiography/Doppler and cardiac magnetic resonance imaging (CMR) compare in the assessment of mitral regurgitation (MR)?
Methods:
In a prospective, multicenter trial, the severity of MR was assessed in 103 patients using both echocardiography and CMR. On echo, MR regurgitant volume was calculated using the proximal isovelocity surface area with angle-correction, and overall severity (mild/moderate/severe) was assessed using an integrated approach. On CMR, MR volume was calculated as the difference between left ventricular (LV) stroke volume and forward flow; and severity was based on these values with thresholds of 30 ml and 60 ml for mild, moderate, and severe MR. Of 103 patients, 38 patients subsequently underwent isolated mitral valve surgery; 26 of these patients underwent a second CMR 5-7 months after surgery. The preoperative estimate of MR severity was correlated with the postoperative decrease in LV end-diastolic volume.
Results:
Agreement between CMR and echo estimates of MR severity was modest in the whole cohort (r = 0.6, p < 0.0001), and was worse in the subset of patients who underwent surgery (r = 0.4, p = 0.01). There was a strong correlation between postoperative LV remodeling and MR severity assessed with CMR (r = 0.85, p < 0.0001), and no correlation between post-surgical LV remodeling and MR severity assessed with echo (r = 0.32, p = 0.1).
Conclusions:
The authors concluded that CMR appears more accurate than echo/Doppler in the assessment of MR severity, and suggest that CMR should be considered in patients when the assessment of MR severity would influence important clinical decisions (such as the decision to undergo mitral surgery).
Perspective:
This is a provocative study that seems to suggest that echo/Doppler is of little value in the simple assessment of whether or not MR is severe––striking in light of the substantial history and data that support its use for that very thing. Methodological decisions are worth considering.
- The method used with CMR to assess MR volume (stroke volume–forward flow) is feasible on echo/Doppler, yet regurgitant volume was quantified on echo using the PISA method. If anything, this might serve as further indictment of the problematic PISA method for MR quantification.
- Postoperative LV remodeling was used to determine the ‘correctness’ of MR assessment. Few data points were available (26 patients, reflecting 68% of operated patients and 25% of patients studied). Of greater concern, multiple factors (including MR chronicity and degree of preoperative LV changes) also would be expected to affect postoperative LV reverse remodeling, making it a crude measure of MR severity. The mixed study population (including both primary MR and secondary MR (with pre-existing LV dysfunction unrelated to MR severity) dramatically undermines the validity of this outcome measurement.
Although these data might provoke thought, echo/Doppler likely will (and should) remain the mainstay for MR assessment, including when important clinical decisions follow. Less time machinating over PISA might be justified.
Keywords: Heart Valve Diseases, Echocardiography, Echocardiography, Doppler, Magnetic Resonance Imaging, Cardiac Surgical Procedures, Mitral Valve, Mitral Valve Insufficiency, Ventricular Dysfunction, Ventricular Dysfunction, Left, Prospective Studies, Stroke Volume
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