Abstract 1585: Echocardiographic Left Ventricular Volumes are Optimally Indexed to Fat Free Mass to Adjust for Differences in Body Size

Abstract

Introduction Echocardiographic left ventricular (LV) size and structure are commonly indexed to body surface area (BSA) to adjust for body size. However, BSA may not be the optimal variable to adjust measurements to. While previous studies have demonstrated that the best determinant of LV mass is fat free mass (FFM), the relationship of LV volumes with body composition is uncertain. Objectives To determine the relationships between LV size and body composition. Methods Normal subjects (Caucasian, Maori, Samoan, Chinese and Indian ethnicity) free of cardiac disease underwent medical history, ECG, blood test (cholesterol/glucose), echocardiography for LV volumes (2D biplane methods of discs) and DEXA scans (body composition). Results 166 subjects were assessed: 96 (56%) were women, median age 26yrs, mean BMI 25.4 (SD 6.0), BSA 1.85m 2 (SD 0.28), LVEDV 88ml (SD 27), LVESV 33ml (SD 14). Significant correlations were observed between LV size and measures of body size in all ethnic groups. However, FFM was the best independent predictor of LV volumes (LVEDV partial R 2 0.48 – 0.60). Body size was smallest among Asian subjects and highest among Maori & Samoan subjects. A significant difference in unindexed LVEDV was observed across the groups which persisted when indexed to BSA or height (all P<0.01). However, when LVEDV was indexed to FFM the ethnic differences were reduced (figure ). Conclusions Among normal subjects LV size is strongly related to FFM. Indexing LV volumes to FFM largely eliminated the differences in LVEDV between subjects with varying body composition. Reference and partition values for normal LV size should be based on LV volumes indexed to fat free mass.