ECHOCARDIOGRAPHIC MID-VENTRICULAR LINEAR DIMENSIONS ARE MORE ACCURATE THAN TRADITIONAL BASAL-LEVEL LINEAR DIMENSIONS: AN MRI VALIDATION STUDY

Echocardiographic assessment of left ventricular (LV) size begins with the simple measurement of linear dimensions that approximate its volume based on the ellipsoid model. One of the fundamental limitations is that linear dimensions are - based on antiquated conventions - measured at the basal level of the LV that does not represent the true diameter of the ellipsoid. The objective of this study was to determine the optimal level to measure the LV cavity diameter and wall thickness which would provide the most accurate estimate of LV end-diastolic and end-systolic volumes (LVEDV, LVESV), LV mass (LVM), and LV ejection fraction (LVEF). To determine the optimal level to measure linear dimensions, a derivation cohort of 75 patients having undergone a clinically-indicated cardiac MRI at the Jewish General Hospital was assembled. Patients had ischemic heart disease (N=25), nonischemic cardiomyopathy (N=25), or no structural heart disease (N=25). The 3-chamber view was analyzed using a custom MATLAB program to measure the LV cavity diameter and wall thickness at 15 equidistant levels from base to apex. The volumetric estimates derived from each of these levels was compared against the method of discs from the short-axis stack (reference standard). The optimal level was found to be the mid LV at the inflection point of the septum, having a stronger correlation with the method of discs than the basal LV for LVEF (R 0.83 vs. 0.78), LVEDV (R 0.86 vs. 0.84), and LVM (R 0.83 vs. 0.80), A validation cohort of 100 patients having undergone a clinically-indicated echocardiogram before cardiac surgery was extracted from the POSSE study. The mid LV cavity diameter yielded a stronger correlation with the method of discs than the basal LV cavity diameter for LVEF (R 0.96 vs. 0.80) and LVESV (R 0.90 vs. 0.86). Measurement of LV dimensions at the optimal mid-ventricular level provides a more accurate estimate of LV size and function as compared to the traditionally recommended basal level. In particular, calculation of LVEF based on measurements at the mid-ventricular level appears to be more robust and less vulnerable to sigmoid septum variants or regional wall motion anomalies.