Left ventricular mass in hypertrophic cardiomyopathy: assessment by three-dimensional and geometric MR methods

The goals of this work were to evaluate the practical utility of MRI to quantify myocardial mass in patients with hypertrophic cardiomyopathy (HCM), define the differences in myocardial mass measurements obtained with three-dimensional and geometric MR methods in patients with normal left ventricular morphology and in patients with wall thickening, and establish the correlation between the two MR methods and the geometric echocardiographic method (GEM).

The same protocol was followed to conduct prospective MR examinations on 72 patients. In 60 of the subjects suspected to have HCM, imaging was performed to confirm or rule out the preliminary clinical diagnosis; the other 12 were healthy volunteers. Multislice SE, single slice multiphase, and multislice multiphase GRE sequences were performed in all cases. Left ventricle mass was calculated using formulas that assume an ellipsoid geometry for the left ventricle (geometric method), and the results were compared with the mass found using the three-dimensional method and subsequent application of Simpson rule. Tests were run to evaluate intraobserver variability in the MR data obtained with the three-dimensional method. The measurements obtained with the two MR methods were compared with the results obtained with GEM.

Although the mean left myocardial mass values obtained using the three-dimensional MR method were smaller than the mean values found with the geometric MR method in all patients, the difference was significant only in patients with HCM. The correlation between the geometric MR method and GEM was very good both in patients with HCM and in those with normal wall thickening. The correlation between the three-dimensional MR method and GEM was good in patients whose left ventricle morphology was normal and poor in patients with HCM. Intraobserver agreement for three-dimensional mass values was excellent.

MR examinations should be a standard technique for calculating myocardial ventricular mass. In patients with normal ventricle wall thickness, the geometric method can be used to calculate myocardial mass because it is less time consuming. However, in patients with abnormal morphology of the left ventricle and/or asymmetric wall thickening such as found in HCM, in whom the geometric method overestimates myocardial mass, measurements should be made using the three-dimensional method.