Commentary: A riddle wrapped in a mystery inside an enigma

Abstract

Central MessageAtrial functional mitral regurgitation is an important prognostic indicator in patients being treated surgically for mitral regurgitation.See Article page XXX.See Article page 1821. Hirji and colleagues1Hirji A.S. Cote C.L. Javadikasgar H.S. Malarczyk A. McGurk S. Kaneko T. Atrial functional versus ventricular functional mitral regurgitation: prognostic implications.J Thorac Cardiovasc Surg. December 31, 2020; ([Epub ahead of print])Abstract Full Text Full Text PDF Scopus (4) Google Scholar from Brigham and Women's Hospital report their nearly 20-year experience with mitral valve surgery in patients with atrial functional mitral regurgitation (A-FMR). The study details their experience with 94 patients who underwent mitral valve surgery in the setting of atrial fibrillation or left atrial dilatation and preserved left ventricular function. In comparing this cohort of patients with a group of 84 patients who underwent mitral valve surgery for ventricular FMR, the authors found rather interesting and thought-provoking results. First, and quite importantly, the authors identify important baseline cardiac morphological and functional differences between the 2 cohorts. Patients with A-FMR have more atrial fibrillation and right heart dysfunction and less left-sided heart failure with smaller left ventricle cavities and normal ejection fraction. Second, and also important, the authors demonstrate that patients with A-FMR have significantly better outcomes compared with their counterparts with ventricular FMR, which they identified as a significant predictor of midterm mortality in risk-adjusted analysis. Given these differences, the authors deliver a message that is singular but not entirely simple. Early discrimination between these 2 etiologies of MR is important and may allow for better management of patients in the short and long-term. Unfortunately, as the authors adeptly allude to, A-FMR may be an elusive diagnosis often camouflaged by myriad other pathophysiologic issues that affect the cardio-respiratory system, including atrial fibrillation, heart failure with preserved ejection fraction, and potentially other coexisting cardiomyopathies that may complicate its diagnosis. Lack of concrete guidelines for the diagnosis of A-FMR further frustrate clinicians' ability to identify this pathology. Other issues remain as well, including, as pointed out by the authors, the role of left atrial and annular dynamics in causing and perpetuating MR in these patients. This is especially important in patients with longstanding atrial fibrillation, where a strategy of rate control over rhythm control may expose the patient to higher left atrial pressures and lead to long-term remodeling of the atria with resultant valvular dysfunction. Whereas surgical therapies, as suggested by the authors, enjoy excellent short- and midterm outcomes, one must ask what role electrophysiology therapies and achievement of sinus rhythm should play in the therapeutic management of these patients. Because there are many questions and not so many data-driven answers, Hirji and colleagues1Hirji A.S. Cote C.L. Javadikasgar H.S. Malarczyk A. McGurk S. Kaneko T. Atrial functional versus ventricular functional mitral regurgitation: prognostic implications.J Thorac Cardiovasc Surg. December 31, 2020; ([Epub ahead of print])Abstract Full Text Full Text PDF Scopus (4) Google Scholar are to be congratulated on their efforts to elucidate the surgical outcomes in patients with A-FMR. Despite its observational, single-center, and nonrandomized nature, the data paint an important picture for surgeons and cardiologists alike depicting the importance of studying not only postoperative outcomes but also cardiac morphology and function at presentation. For most of us, A-FMR will continue to remain a riddle wrapped in a mystery inside an enigma until there is better understanding of how left atrial dysfunction influences cardiac—and especially mitral valvular—function. Atrial functional versus ventricular functional mitral regurgitation: Prognostic implicationsThe Journal of Thoracic and Cardiovascular SurgeryVol. 164Issue 6PreviewAtrial functional mitral regurgitation (FMR) occurs because of left atrial dilatation or atrial fibrillation in heart failure with preserved left ventricular (LV) function, contrary to ventricular FMR, which occurs because of LV dysfunction. Despite pathophysiological differences, current guidelines do not discriminate between these 2 entities. Full-Text PDF