Abstract

Introduction: Abnormal papillary muscles (PM) are frequently observed in hypertrophic cardiomyopathy (HCM). We sought to assess the relationship between morphologic alterations of PM in HCM patients and left ventricular outflow tract (LVOT) obstruction, using magnetic resonance imaging (MRI) and echocardiography (echo).

Methods: Fifty-six HCM patients (mean age 42 [27, 51] years, 70 % male) and 30 controls (mean age (42 [30, 53] years, 80% male) underwent MRI on 1.5T scanner (Siemens, Erlangen, Germany). Standard cine images were obtained in short axis (base to apex), along with 2, 3 & 4 chamber views. The presence of bifid PM (none, one, or both) and antero-apical displacement of anterolateral PM were recorded by MRI and correlated with resting LVOT gradients obtained by echo.

Results: Double bifid PM (70% vs. 17%) and antero-apical displacement of anterolateral PM (77%) vs. 17%) were more prevalent in HCM patients vs. controls (p <0.0001). Subjects with antero-apically displaced PM and double bifid PM had higher resting LVOT gradients compared to controls (45 [6, 81] vs. 12 [0, 12] mm Hg, (p < 0.01) and 42 [6, 64] vs. 11 [0, 17] mm Hg, (p=0.02) respectively. In HCM patients, the odds ratio of having significant (> 30 mm Hg) peak resting gradient) was 7.1 (CI 1.4-36.7) for antero-apically displaced anterolateral PM and 10.4 (CI 1.2-91.2) for double bifid PM (both p = 0.005), independent of septal thickness, use of beta-blockers and/or calcium blockers and resting heart rate.

Conclusions: HCM patients with abnormal PM have a higher degree of resting LVOT gradient, independent of septal thickness.