Abstract 4363343: Papillary Muscle Anatomy in Hypertrophic Cardiomyopathy: Comparison to Normal and Impact on Outcomes of Septal Myectomy

Background: Several studies have described anteroapical displacement of the anterolateral papillary muscle (PM) in patients with hypertrophic cardiomyopathy (HCM), implying a role in left ventricular outflow tract obstruction. Some surgeons address PM position during myectomy, but no quantitative imaging measures of abnormal versus normal PM anatomy exist. Objective: To quantify PM anatomy in HCM using cardiac magnetic resonance imaging (CMR) and determine if differences in PM anatomy alter myectomy outcomes. Methods: 143 patients with HCM (median age 58 (IQR 48-65) years, 64% male) who had undergone CMR were compared to 50 healthy controls (median age 32 (IQR 28-50) years, 40% male). The HCM cohort included 50 patients with non-obstructive HCM, 50 with obstructive HCM requiring transaortic myectomy, and 43 with obstructive HCM requiring transapical myectomy. Six independent measurements of PM anatomy were performed (Figure), comprising both established and novel measurements. Intergroup comparisons were made, and correlative analysis of PM measurements was performed using echocardiographic data and surgical outcomes. Results: There was significant variability in PM anatomy in all patients. The SXAd measurement was smaller (26.76 +/- 6.10 mm vs 32.10 +/- 4.85 mm, p < 0.001) in HCM patients versus controls. The 4Cd measurement was smaller in patients with apical HCM than in all other groups (p < 0.001). D_PM, d_apex, and the ratio between these measurements were consistent among all groups. No PM quantification in HCM patients correlated to pre-, intra-, or postoperative LVOT obstruction, NYHA class, or postoperative length of stay. Conclusions: Although there were some statistically significant differences between healthy patients and those with HCM, analysis of six different PM measurements yielded no associations with LVOT obstruction or outcomes of septal myectomy.