Papillary muscle abnormalities in a hypertrophic cardiomyopathy population: a cardiovascular magnetic resonance study

Background: Hypertrophic Cardiomyopathy (HCM) is a common genetic disorder with a wide variability in anatomic and clinical expression. However, data on Papillary Muscles (PMs) are scarce. Therefore, we aimed to analyze PMs characteristics by magnetic resonance imaging in a HCM population. Methods: We retrospectively evaluated 50 HCM patients (pts) who performed Cardiac Magnetic Resonance (CMR) in our institution, between 2008 and 2012. All pts had preserved Left Ventricular Ejection Fraction (LVEF) and were on sinus rhythm. Cine and Delayed Enhancement (DE) images were acquired on a 3T scanner and analyzed using a commercial workstation. All statistics analyses were performed using SPSS 20.0 version. Results: HCM pts were predominantly male (66%), with a mean age 47±18 years. Fifty-eight percent were in NYHA class I and the remaining in NYHA class II. The most common morphological presentation was septal HCM (68%) followed by apical HCM (14%). LV outflow gradient ≥30 mmHg was present only in 9 pts. LVEF (70±6%) and LV volumes (VTD=80±15 ml/m2; VTS=24±7ml/m2) were in the normal range. Right ventricular EF was 63±6%. In the majority of pts LV wall mass (LVWM) was increased (107±45g/m2). The maximal LV Wall Thickness (LVWT) was 20±6mm, with hypertrophy involving 6±4 segments. Hypertrabeculation was also a common feature (32%), but a non-compacted/compacted myocardium ratio >2.3 was found only in 6 pts (involving ≤2 segments). Eighty-four percent of pts had DE in LV wall, mainly in the hypertrophied segments and with a focal pattern (60%). The RV insertions points also represent a common location (62%). Subendocardial or transmural DE occurred only in 9 pts. We identified > 2 PMs in two cases. The mean PMs mass was 6±2g/m2, slightly higher in PMs in anterior location. We found a significant correlation between PMs mass and LVWM (rho 0.64, p<0.0001), maximal LVWT (p=0.01) and the number of hypertrophied segments (rho 0.55, p<0.0001). PMs DE was present in 34% of the pts, with equal distribution to PMs and in one case confined to them. There was no correlation between PMs DE and the numbers of segments with DE in LV wall. Finally, pts with PMs DE had significantly increased PMs mass compared with other pts (7±3 vs 5±2g/m2, p=0.04). Conclusions: In our population, PMs hypertrophy paralleled that of the LV wall and DE was identified in a significant proportion of pts. These findings suggest PMs enrolment in the cardiomyopathic process of HCM with potencial clinical consequences in some pts.