Isolated posterior mitral leaflet elongation-related dynamic left ventricular outflow obstruction

A 31-year-old male presented with complaints of mild exertional dyspnoea (NYHA II) and atypical chest pain for 2 months. Cardiovascular examination revealed a systolic murmur, increasing in intensity on standing and decreasing with isometric handgrip. Electrocardiography showed poor precordial R wave progression without left ventricular hypertrophy or ST-T changes. On transthoracic echocardiography, he had a normal left ventricular wall thickness and systolic function. Color doppler interrogation revealed a turbulence in the left ventricular outflow tract (LVOT), with a resting gradient of 21 mm Hg (Panel A) which increased to 43 mm Hg on standing (Panel B). Systolic anterior motion of the posterior mitral leaflet (PML) was seen (Panel C and D) without any mitral regurgitation. Cardiac catheterization was notable for a spike- and dome-shaped pulse (Panel E) and a Brockenbrough – Braunwald – Morrow sign1 (Panel F). Left ventricular hypertrophy2 and papillary muscle abnormalities3 have been described to cause dynamic LVOT obstruction; cardiac magnetic resonance imaging ruled these out. Transesophageal echocardiography showed an elongated PML measuring 20 mm (Panel G). The initial point of turbulence on colour doppler imaging was precisely at the site of the tip of the PML (Panel H). The systolic anterior motion of the PML was also better visualized (Panel I). A final diagnosis of LVOT obstruction secondary to an elongated PML was made. The patient was started on oral beta-blockers before discharge and follow-up echocardiography done a month later showed a reduction in the LVOT gradient with a significant symptomatic relief.