Mitral Valve Prolapse: Multimodality Imaging and Genetic Insights

Abstract

Mitral valve prolapse (MVP) is a common heritable valvulopathy affecting approximately 2.4% of the population. It is the most important cause of primary mitral regurgitation (MR) requiring surgery. MVP is characterized by fibromyxomatous changes and displacement of one or both mitral leaflets into the left atrium. Echocardiography represents the primary diagnostic modality for assessment of MVP. Accurate quantitation of ventricular volumes and function for surgical planning in asymptomatic severe MR can be provided with both echocardiography and cardiac magnetic resonance. In addition, assessment of myocardial fibrosis using late gadolinium enhancement and T1 mapping allows better understanding of the impact of MVP on the myocardium. Imaging in MVP is important not only for diagnostic and prognostic purposes, but is also essential for detailed phenotyping in genetic studies. Genotype-phenotype studies in MVP pedigrees have allowed the identification of milder, non-diagnostic MVP morphologies by echocardiography. Such morphologies represent early expression of MVP in gene carriers. This review focuses on multimodality imaging and the phenotypic spectrum of MVP. Moreover, the review details the recent genetic discoveries that have increased our understanding of the pathophysiology of MVP, with clues to mechanisms and therapy.

Keywords: Cardiac magnetic resonance; Echocardiography; Genetics; Mitral regurgitation; Mitral valve prolapse.

Figure 1

Example of bileaflet mitral valve prolapse (A–D). Prolapse of the anterior and posterior mitral valve leaflets demonstrated in (A) a long-axis view of a 2-dimensional (2D) transthoracic echocardiogram (leaflets are displaced more than 2 mm beyond the annulus, shown as a dotted line), (B) a mid-esophageal 4-chamber view of a 2D transesophageal (TEE) echocardiogram, (C) a 3-dimensional (3D) TEE en face or surgical view (A1, A2, A3 and P1, P2, P3 are the lateral, middle, and medial anterior and posterior scallops, respectively), and (D) a cardiac magnetic resonance (CMR) steady state free processing (SSFP) long-axis view. AO = aorta; LA = left atrium; LV = left ventricle; RV = right ventricle; MAD = mitral-annular disjunction (separation between the left atrial wall at the level of mitral valve junction and the LV free wall).

Figure 2

Examples of focal and diffuse myocardial fibrosis in mitral valve prolapse (MVP). Short-axis view with three-dimensional late-gadolinium enhancement showing fibrosis of the papillary muscle tips (arrows) in a patient with bileaflet MVP and mild mitral regurgitation (A); precontrast T1 map with increased native T1 (1145 ms) indicating interstitial myocardial fibrosis in a different MVP patient with moderate-severe mitral regurgitation (B).

Figure 3

Phenotypic spectrum of mitral valve prolapse (MVP). 2-dimensional echocardiographic parasternal long-axis images demonstrating (A) minimal systolic displacement, (B) anterior abnormal coaptation, and (C) posterior MVP. All show posterior leaflet bulging (arrows) relative to the anterior leaflet, but only MVP shows diagnostic superior leaflet displacement relative to the mitral annulus (dotted line) into the left atrium (LA). Posterior MVP and abnormal anterior coaptation are similar with regards to an increased coaptation height and an elongated posterior leaflet. Minimal systolic displacement shows posteriorly coapting leaflets, as seen in normal patients. AO = aorta; LV = left ventricle; RV = right ventricle.