Abstract 3019: MRI Detects High Prevalence of Altered Papillary Muscle Morphology in Patients with Obstructive Hypertrophic Cardiomyopathy
Introduction: Morphologic alterations (including apical insertion) of papillary muscles (PM) in patients with hypertrophic cardiomyopathy (HCM) can potentially contribute to left ventricle outflow tract (LVOT) obstruction. Magnetic resonance imaging (MRI) can accurately characterize morphologic aspects of HCM, including PM anatomy. We sought to assess the prevalence of morphologic alterations of PM in HCM patients and its hemodynamic sequelae.
Methods: Forty-three patients (mean age 43±18 years, 63% males) with echocardiography (echo)-confirmed HCM and 21 controls (no cardiac pathology on MRI, mean age 35±13years, 86% males) underwent MRI on 1.5T scanner (Siemens Sonata, Erlangen, Germany). TrueFISP (TE=1.6 msec, TR=3.5 msec, flip angle=70°, slice thickness-8–10 mm) cine images were obtained in short axis (base to apex), along with 2, 3 & 4 chamber views. Presence of bifid PM (involving none, one or double PM) was recorded if the PM had > 1 head seen on multiple cine images. Minimum distance between septum and PM was determined in 4-chamber view at end-diastole, along with maximum PM thickness. Apical insertion was defined when the PM were displaced distally in 2 or 4 chamber views and visible on the distal-most apical short axis image. Resting LVOT gradients and systolic anterior motion (SAM) of mitral valve was recorded (both by echo) in HCM patients.
Results: Double bifid PM [31(74%) vs. 3 (14%)] and apical PM insertion [25 (60%) vs. 4 (19%)] were more prevalent in HCM patients vs. controls, both p <0.0001. Mean distance from PM to septum (cm) was lower (0.5±0.2 vs. 1.1±0.2, p<0.0001), and septal thickness (cm) was greater (2.4±0.7 vs. 1.2±0.2, p<0.001) in HCM vs. controls. Resting LVOT gradient (mm Hg) trended higher in HCM patients with apical PM insertion vs. those without (45±46 vs.25±23, p<0.1). Prevalence of SAM (66% vs. 33%, P<0.05) and resting LVOT gradient (70% vs. 30%, p<0.05) was higher in HCM patients with double bifid PM vs none or single bifid PM.
Conclusions: Apical insertion of PM and double bifid PM are significantly more prevalent in patients with HCM, along with increased PM thickness and reduced distance between PM and septum. Double bifid PM is more prevalent in those HCM patients with SAM and resting LVOT dynamic obstruction.