Abnormal papillary muscle morphology is independently associated with increased left ventricular outflow tract obstruction in hypertrophic cardiomyopathy

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Background:Abnormal papillary muscles (PM) are often found in hypertrophic cardiomyopathy (HCM).Objective:To assess the relationship between morphological alterations of PM in patients with HCM and left ventricular outflow tract (LVOT) obstruction, using magnetic resonance imaging (MRI) and echocardiography.Methods:Fifty-six patients with HCM (mean age 42 years (interquartile range 27, 51), 70% male) and 30 controls (mean age (42 (30, 53) years, 80% male) underwent MRI on a 1.5 T scanner (Siemens, Erlangen, Germany). Standard cine images were obtained in short-axis (base to apex), along with two-, three- and four-chamber views. The presence of bifid PM (none, one or both) and anteroapical displacement of anterolateral PM was recorded by MRI and correlated with resting LVOT gradients obtained by echocardiography.Results:Double bifid PM (70% vs 17%) and anteroapical displacement of anterolateral PM (77% vs 17%) were more prevalent in patients with HCM than in controls (p<0.001). Subjects with anteroapically displaced PM and double bifid PM had higher resting LVOT gradients than 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 patients with HCM, the odds ratio of having significant (≥30 mm Hg) peak resting gradient was 7.1 (95% CI 1.4 to 36.7) for anteroapically displaced anterolateral PM and 10.4 (95% CI 1.2 to 91.2) for double bifid PM (both p = 0.005), independent of septal thickness, use of β-blockers and/or calcium blockers and resting heart rate.Conclusions:Patients with HCM with abnormal PM have a higher degree of resting LVOT gradient, which is independent of septal thickness.

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