ASSESSMENT OF VENTRICULAR VOLUMES USING CINE MAGNETIC-RESONANCE IN THE INTACT DOG - A COMPARISON OF MEASUREMENT METHODS

RATIONALE, OBJECTIVE AND METHODS. The authors recently combined magnet ic resonance imaging with high-fidelity left ventricular (LV) pressure measurement in a closed-chested, intact animal model. However, LV vol umes derived from summated serial short axis slices require long imagi ng times and make it difficult to record LV volumes in response to acu te alterations in load. In this study, geometry-based LV endsystolic v olume estimates calculated from a single long-axis image (Area-Length formula) and from a long-axis and short-axis image (Bullet formula) we re compared to those derived from summated short-axis images of the le ft ventricle (Simpson's rule) during altered loading conditions in six anesthetized, intact dogs. RESULTS. Angiotensin infusion produced thr ee different LV systolic pressures (89 +/- 8 vs. 123 +/- 12 vs. 151 +/ - 10 mmHg, P < .001). Area-Length and Bullet formula end-systolic volu mes correlated with Simpson's rule volumes (r = .95 and .97; respectiv ely). However, Bullet formula end-systolic volumes provided a signific antly better agreement with Simpson's rule end-systolic volumes. CONCL USIONS. The Bullet formula can be substituted for Simpson's rule to re cord magnetic resonance LV volumes during steady-state alterations in load in our intact animal model.