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Myocardial Fibrosis in Mitral Valve Prolapse
Study Questions:
What is the relationship of left ventricular (LV) fibrosis, as detected by late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMR), to the etiology of primary mitral regurgitation (MR) and prognosis in patients with and without mitral valve prolapse (MVP)?
Methods:
CMR was performed in 705 patients referred for assessment of chronic MR. After excluding patients with other concurrent forms of cardiac disease, 356 patients with primary MR remained. Patients were evaluated between 2009 in 2014 and followed for clinical events until February 2018. MVP was defined on CMR when there was >2 mm displacement of any mitral valve scallop into the left atrium on a three-chamber view. LV volumes, stroke volume, and MR fraction and volume were also calculated from CMR. LGE was assessed in 17 LV segments, and its transmural extent was categorized as four quartiles of wall thickness.
Results:
For the final population, 51.7% were men and the mean age was 61.9 ± 14.3 years. MVP was noted in 177 (47.9%), of whom posterior mitral leaflet prolapse was noted in 100. LGE was present in 77 patients (21.6%), mostly in noncoronary distributions. A mid-wall location was noted in 45 (12.6%), and a patchy pattern in 29 (8.1%). Two or fewer segments were involved in 79.2% of affected patients, and the average LGE burden was 2.2 ± 0.9% of the left ventricle. LGE was noted in 36.7% of MVP patients compared to 6.7% of non-MVP patients (p < 0.001). The most common locations for LGE were the basal inferolateral (31.1%) and basal inferior walls (10.7%), which are areas adjacent to the posteromedial papillary muscle insertion. MVP was noted in 58 of 60 patients with LGE in segments adjacent to the posteromedial papillary muscle. On multivariable analysis, LGE was associated with age, LV ejection fraction, MR regurgitant fraction, and presence of MVP. An incremental increase in the prevalence of LGE was noted with increasing MR fraction (p = 0.006) in patients with MVP, but not in patients without MVP. There was no significant relationship between the prevalence of LGE and LV end-diastolic volume index. Over a median follow-up of 1,354 days, 96 patients underwent mitral valve surgery, of whom 72 had MVP. Arrhythmic events occurred in nine patients (2.5%), eight of whom had MVP. LGE had been noted in five of the eight arrhythmic patients with MVP and one non-MVP patient. The arrhythmic event rate was 7.7% in MVP patients with LGE, 2.7% in MVP patients without LGE, and 0.6% in non-MVP patients (p < 0.01).
Conclusions:
LV fibrosis, as manifest by LGE, is more prevalent in MVP than other patients with primary MR. LGE in the presence of primary MR and especially MVP may confer an incremental risk for arrhythmic events.
Perspective:
Several small studies have noted an increased prevalence of myocardial fibrosis in patients with MVP. This large prospectively identified population nicely demonstrates an incremental prevalence of myocardial fibrosis in MVP compared to other forms of primary MR. The most common location of fibrosis was at the base of the posteromedial papillary muscle suggesting cause-and-effect between mitral prolapse and the presence of fibrosis. A link between prolapse and fibrosis in this location previously has been suggested and proposed to be related to excess traction on the posteromedial papillary muscle related to the prolapsing motion of the valve. This study also suggested an increased risk of arrhythmic events in patients with MVP and myocardial fibrosis, although the small number of events precludes a broad conclusion in this area. Although there was a link between regurgitant fraction and prevalence of fibrosis in patients with MVP, but not those without, fibrosis appeared independent of LV volume and remodeling, suggesting a unique link to the actual valve prolapse and fibrosis. Of note, patients were identified as either having or not having MVP by a single dichotomous measurement of >2 mm of scallop displacement. Whether further refinements such as magnitude of displacement, number of displaced scallops, and posterior versus bi-leaflet prolapse categorization would confer further prognostic information when combined with LGE remains conjectural.
Clinical Topics: Arrhythmias and Clinical EP, Cardiac Surgery, Cardiovascular Care Team, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Valvular Heart Disease, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Cardiac Surgery and Arrhythmias, Cardiac Surgery and VHD, Interventions and Imaging, Interventions and Structural Heart Disease, Magnetic Resonance Imaging, Mitral Regurgitation
Keywords: Arrhythmias, Cardiac, Cardiac Surgical Procedures, Diagnostic Imaging, Fibrosis, Gadolinium, Heart Valve Diseases, Magnetic Resonance Imaging, Mitral Valve Insufficiency, Mitral Valve Prolapse, Papillary Muscles, Prolapse, Stroke Volume
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