Author + information
- Seth Uretsky, MD∗ ( and )
- Steven D. Wolff, MD, PhD
- ↵∗Department of Cardiovascular Medicine, Gagnon Administration, Meade B, 100 Madison Avenue, Morristown, New Jersey 07960
We read with interest the letter to the editor by Sachdev et al. (1). The authors present data correlating the severity of mitral regurgitation (MR) as assessed by echocardiography and magnetic resonance imaging (MRI), and compare and contrast their results with those from a prospective multicenter trial we published last year (2). We have a few comments for the readers of iJACC.
Sachdev et al. (1) present purely comparative data with no reference standard. Agreement between the 2 techniques does not validate either of them. In contrast, our study correlated regurgitant volumes by echo and MRI with a reference standard, namely the response to surgery (change in left ventricular end-diastolic volume), and included measurements of interobserver variation.
The authors state that “MR severity using PISA RV alone compared well with CMR.” Yet, they report a correlation coefficient range of r = 0.64 to r = 0.88 (r2 = 0.41 to r2 = 0.77), which implies that 41% to 77% of the observed variation in the echocardiographic regurgitant volume is related to the MRI-derived regurgitant volume. That leaves a lot of room for error. It is consistent with their wide limits of agreement between echocardiography and MRI: -44 to 43 ml, which corresponds to 1.5 grades of regurgitation.
Most importantly, in their final paragraph they conclude “Our correlation between techniques was better and did not show a systematic overestimation by echo.” Yet, data derived from their own table (Table 1) clearly show an overestimation bias. Namely, in 15 patients echo estimated MR severity to be greater than MRI and in only 3 patients was it less (Table 1).
The results from our prospective, blinded multicenter trial are based on echocardiographic review by nationally and internationally renowned echocardiographers (Gillam, Lang, and Chaudhry). Our results show not just poor agreement between echo and MRI, but also poor interobserver agreement with echocardiography, a finding that has been replicated by others (3). Two-thirds of the patients that had isolated mitral valve surgery did not have severe MR on MRI, and did not meet American College of Cardiology/American Heart Association guidelines for surgery.
Even if one accepts the Sachdev proximal isovelocity surface area data at face value, American Society of Echocardiography guidelines recommend an integrated approach to assessing MR severity. With that approach, Sachdev et al. (1) show that 56% (15 of 27) of their patients that have moderate-to-severe or severe MR on echo have only mild or mild-to-moderate MR by MRI. That is a bias that has real world consequences and should not be trivialized.
The misdiagnosis of severe MR is not just of academic interest. It has profound consequences in terms of patient morbidity and mortality, as well as health care costs. A claim of good correlation between proximal isovelocity surface area and echocardiography by a single site, even if true, misses the implications of our study. We live in a world where not all echocardiographers quantify MR severity by proximal isovelocity surface area, and those who do, use an integrated approach to determine its severity. More than a year has elapsed since our results were published.
The Public Health Service has an obligation to the taxpayers of this country. It could and should do more to improve the cost and quality of health care with respect to the misdiagnosis of chronic severe MR. As soon as practically possible, it should sponsor a National Institutes of Health–funded prospective multicenter trial to determine the efficacy of cardiac MRI for improving patient outcomes and decreasing healthcare costs. Our results suggest mitral valve surgeries would decrease by more than 50%, patient morbidity and mortality would decrease, and the healthcare system would save hundreds of million dollars annually. That is the kind of research that seems worthy of taxpayer support.
Please note: Dr. Uretsky has reported that he has no relationships relevant to the contents of this paper to disclose. Dr. Wolff is a Member of NeoSoft, LLC.
- 2017 American College of Cardiology Foundation
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