Hybrid Positron Emission Tomography/Magnetic Resonance Imaging in Arrhythmic Mitral Valve Prolapse

Abstract

Importance: Myocardial replacement fibrosis has been reported to occur in one-third of patients with mitral valve prolapse (MVP) and significant mitral regurgitation (MR). However, it remains unknown whether there are detectable changes in myocardial metabolism suggestive of inflammation or ischemia that accompany the development of fibrosis.

Objectives: To characterize the burden and distribution of fluorine 18-labeled (18F) fluorodeoxyglucose (FDG) uptake and late gadolinium enhancement (LGE) in patients with degenerative MVP and ventricular ectopy.

Design, setting, and participants: Prospective observational study of 20 patients with MVP and significant primary degenerative MR who were referred for mitral valve repair and underwent hybrid positron emission tomography/magnetic resonance imaging (PET/MRI). Ventricular arrhythmias were categorized as either complex (n = 12) or minor (n = 8). Coregistered hybrid 18F FDG-PET and MRI LGE images were assessed and categorized. Recruitment occurred in the new patient clinic of a mitral valve repair reference center. This study was conducted from January 11, 2018, to June 26, 2019.

Exposures: Simultaneous cardiac 18F FDG-PET and MRI with LGE imaging on a hybrid PET/MRI system and ambulatory rhythm monitoring.

Main outcomes and measures: Patients were categorized by the presence and pattern of FDG uptake and LGE, the severity of ventricular arrhythmias, and the indication for mitral valve surgery.

Results: In the cohort of 20 patients, the median age was 59.5 years (interquartile range, 52.5-63.2 years). Focal, or focal-on-diffuse uptake, of 18F-FDG (PET positive) was detected in 17 of 20 patients (85%). The FDG uptake coexisted with areas of LGE (PET/MRI positive) in 14 patients (70%). Of the 5 asymptomatic patients with normal ventricular indices and absence of any surgical indications, all were PET/MRI positive.

Conclusions and relevance: In this pilot study, we demonstrate a novel association between degenerative MVP and FDG uptake, a surrogate for myocardial inflammation and/or ischemia. Such evidence of myocardial injury, even in asymptomatic patients, suggests an ongoing subclinical disease process. These findings warrant further investigation into whether imaging for myocardial inflammation, ischemia, and scar has a role in arrhythmic risk stratification and whether it provides incremental prognostic value in patients with chronic severe mitral regurgitation undergoing active surveillance.

Figure 1.. Hybrid Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) of 3 Different Patients

A, Example of fluorine 18–labeled fluorodeoxyglucose (¹⁸F-FDG) uptake that colocalizes with regions of late gadolinium enhancement (LGE) (PET+/MRI+) in a focal-on-diffuse pattern (maximum standardized uptake value [SUVmax], 3.5; maximum tissue-to-background ratio [TBRmax], 1.8; target-normal-myocardium ratio [TNMR], 1.8). These images were obtained from a man in his early 60s with asymptomatic degenerative mitral valve prolapse, significant mitral regurgitation (3+), and complex ventricular ectopy (nonsustained ventricular tachycardia and pleomorphic premature ventricular contractions) but without any objective surgical indications. The patient is being followed up with active surveillance. B, Example of diffuse uptake (SUVmax, 9.6; TBRmax, 4.2; TNMR, 1.3), which was interpreted as physiological or nonspecific uptake. C, Example of concordant ¹⁸F-FDG uptake and LGE in an asymptomatic patient with chronic severe degenerative mitral regurgitation and absent left ventricular remodeling (left ventricular ejection fraction, 60% and end-systolic dimension, 38 mm). The top 2 images are LGE imaging sequences and the bottom 2 images are ¹⁸F-FDG imaging. The yellow arrowheads indicate areas of either LGE or FDG uptake, respectively. LA indicates left atrial; LV, left ventricular.

Figure 2.. Representative Images of 2 Different Patterns of Fluorodeoxyglucose (FDG) Uptake on Hybrid Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) From 2 Different Patients

A, Focal FDG uptake and late gadolinium enhancement (LGE) in the inferolateral and basal inferior segments of the left ventricle in a man in his mid 50s with severe mitral regurgitation and posterior-leaflet prolapse who was asymptomatic with normal ventricular indices (left ventricular ejection fraction, 65%; left ventricular end-systolic dimension, 34 mm) and no objective indications for surgery. He developed episodes of nonsustained ventricular tachycardia (>15 beats) at peak exercise. B, Multifocal pattern of FDG uptake and LGE, in this case involving the septum, inferior, and lateral walls, in a woman in her mid 60s with symptomatic severe mitral regurgitation and bileaflet prolapse. She had infrequent premature ventricular contractions (burden = 0.5%), but they were pleomorphic (at least 3 different morphologies).