Doming Volume in Mitral Valve Prolapse: Pathophysiology, Imaging Implications and Clinical Relevance.

Mitral valve prolapse represents the most common cause of primary mitral regurgitation in Western countries and has traditionally been viewed as a disorder driven by valvular incompetence and chronic volume overload. Within this paradigm, left ventricular enlargement was expected to correlate with regurgitant severity. However, patients with myxomatous bileaflet prolapse often exhibit left ventricular dilatation disproportionate to the degree of regurgitation, leading to the hypothesis of an intrinsic myocardial disease process. Cardiovascular magnetic resonance imaging has challenged this concept through the identification of doming volume, a previously unrecognized systolic blood compartment located between the mitral annular plane and the ventricular surface of prolapsing leaflets. This volume is mechanically coupled to ventricular contraction and contributes to total ventricular volume load independently of transvalvular regurgitation. Recognition of doming volume provides a physiological explanation for excessive ventricular remodeling observed in bileaflet prolapse and Barlow disease. Doming volume has important implications for imaging assessment. Its common exclusion from echocardiographic volumetric measurements may result in underestimation of left ventricular end-systolic volume, overestimation of ejection fraction, and underestimation of regurgitant burden, contributing to discordance between echocardiographic and cardiovascular magnetic resonance-derived measurements. Cardiovascular magnetic resonance enables comprehensive assessment, allowing accurate quantification of ventricular volumes, mitral regurgitation severity, doming volume, and myocardial tissue characteristics. Integration of doming volume into the evaluation of mitral valve prolapse improves physiological consistency between imaging findings and ventricular remodeling. However, further evidence is required before doming volume assessment can be incorporated into operative clinical indications or decision-making thresholds.