Arrhythmic Mitral Valve Prolapse With Only Mild or Moderate MR
- In a small, single-center study of patients with MVP and mild or moderate MR referred to an electrophysiologist, 10 (83%) of 12 patients had evidence of focal or multi-focal 18F-FDG uptake on PET (a surrogate marker of myocardial inflammation), of whom nine (75% of total) had coexistent LGE on MRI (a surrogate marker of replacement fibrosis).
- Only two patients had abnormal extracellular volume on MRI (a surrogate marker of diffuse interstitial fibrosis, typically associated with MR severity but not with replacement fibrosis).
- If the findings are reproduced in larger studies, they could help define the role of chronic myocardial inflammation in the pathophysiology of replacement fibrosis in patients with MVP, and help explain why a majority of sudden deaths among patients with MVP occur in the absence of severe MR.
What are the characteristics of myocardial replacement fibrosis, interstitial fibrosis, inflammation, and ventricular arrhythmia complexity among patients with mitral valve prolapse (MVP) and only mild or moderate mitral regurgitation (MR)?
In a single-center study, patients referred to an electrophysiologist with a history of premature ventricular contractions (PVCs) and MVP with only mild or moderate MR were prospectively enrolled and underwent transthoracic echocardiography for confirmation of the presence of MVP, measurement of mitral annular disjunction (MAD) length, and assessment for a ‘Pickelhaube’ sign; hybrid 18F-fluorodeoxyglucose (18F-FDG)–positron emission tomography (PET) and magnetic resonance imaging (MRI) for evidence of inflammation and late gadolinium enhancement (LGE); and ambulatory ECG monitoring for PVC burden and complexity. Ventricular arrhythmias were considered complex in the setting of pleomorphic PVCs (grade 3), couplets (grade 4A), or triplets or nonsustained ventricular tachycardia (VT; grade 4B). The presence and coexistence of 18F-FDG uptake and LGE were characterized as PET+ / MRI+, PET+ / MRI–, PET– / MRI+, or PET– / MRI–. Extracellular volume (ECV) was calculated from T1 mapping after gadolinium administration, and considered abnormal if the highest-value myocardial segment was >2 standard deviations above an institutional reference defined using seven normal control subjects.
Of 12 patients (eight [67%] women) studied, six (50%) had bileaflet MVP and six (50%) had posterior leaflet MVP. MR was mild in seven (58%) and moderate in five (42%); MAD was present in nine patients (75%) and a Pickelhaube sign was present in four (33%). Ten patients (83%) had complex ventricular arrhythmias (pleomorphic PVCs in seven, couplets in eight, nonsustained VT in six); the mean PVC burden was 5.1 ± 6.8%, and >10% in only two patients. Focal (papillary muscles and/or the inferior or inferolateral segments of the left ventricle [LV], n = 6) or multi-focal (n = 4) 18F-FDG uptake was present in 10 patients (83%), of whom nine (75% of total) had coexistent LGE (PET+ / LGE+). Abnormal ECV was seen in only two patients.
The authors conclude that a majority of patients with degenerative MVP, ventricular ectopy, and mild or moderate MR exhibit evidence of myocardial inflammation that is concordant with myocardial scar, and that further study is needed to determine whether these findings contribute to the observation that a majority of MVP-related sudden deaths occur in patients with less than severe MR.
18F-FDG uptake on PET is a surrogate marker for inflammation, LGE on MRI is a surrogate marker for myocardial scar, and abnormal ECV on MRI is a surrogate marker for diffuse interstitial fibrosis. This very small, single-center study found that nine (75%) of 12 patients with MVP and only mild or moderate MR who had been referred to an electrophysiologist had coexistent LV 18F-FDG uptake and LGE, suggesting that chronic myocardial inflammation might contribute to the pathogenesis of myocardial injury in patients with MVP, and that that process can occur in the absence of severe MR. In contrast, abnormal ECV, which typically is associated with MR severity but not with replacement fibrosis, was uncommon among these patients with less-than-severe MR. In addition to its small size, the study is limited by its biased population of patients referred to an electrophysiologist, and the findings should not be extrapolated to the general population of patients with MVP. If these findings are reproduced in larger studies, they could help define the role of chronic myocardial inflammation in the pathophysiology of replacement fibrosis in patients with MVP, and help explain why a majority of sudden deaths among patients with MVP occur in the absence of severe MR.
Clinical Topics: Arrhythmias and Clinical EP, Noninvasive Imaging, Valvular Heart Disease, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Computed Tomography, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Nuclear Imaging, Mitral Regurgitation
Keywords: Arrhythmias, Cardiac, Contrast Media, Diagnostic Imaging, Echocardiography, Electrocardiography, Fibrosis, Fluorodeoxyglucose F18, Gadolinium, Heart Valve Diseases, Inflammation, Magnetic Resonance Imaging, Mitral Valve Insufficiency, Mitral Valve Prolapse, Positron-Emission Tomography, Tachycardia, Ventricular, Ventricular Premature Complexes
< Back to Listings