Impact of papillary and trabecular muscles on quantitative analyses of cardiac function in hypertrophic cardiomyopathy

PURPOSE: To examine the impact of cardiovascular magnetic resonance (CMR) partitioning methods on volumetric analysis in hypertrophic cardiomyopathy (HCM) patients. The standard CMR method for partitioning ventricular myocardium from ventricular cavity includes the myocardial papillary and trabecular muscles in the cavity volume. This approach may misrepresent ventricular mass and volume in patients with HCM due to large papillary muscles and extensive trabeculations. MATERIALS AND METHODS: Ventricular volume and mass analyses were performed in 30 patients with HCM using the standard method and a detailed method that excluded papillary and trabecular muscles from the left ventricular (LV) volume while including them in LV mass. We also analyzed the degree of mitral regurgitation and compared the results with Doppler echocardiography in a subgroup of 12 patients. Interobserver variability was assessed. RESULTS: The detailed method yielded 17% higher indexed LV mass, 20% lower indexed LV diastolic volume, 13% higher LV ejection fraction (EF) (all P < 0.0001). The resultant mitral regurgitant volumes using the detailed method had less discrepancy with Doppler echocardiography results compared with the results from the standard methods. Interobserver variability was similar by both methods. CONCLUSION: For patients with HCM, a detailed analysis in which the ventricular papillary and trabecular muscles are excluded from LV volume is preferred.