AbstractRATIONALE, OBJECTIVE AND METHODS
The authors recently combined magnetic resonance imaging with high-fidelity left ventricular (LV) pressure measurement in a closed-chested, intact animal model. However, LV volumes derived from summated serial short axis slices require long imaging times and make it difficult to record LV volumes in response to acute alterations in load. In this study, geometry-based LV end-systolic volume estimates calculated from a single long-axis image (Area-Length formula) and from a long-axis and short-axis image (Bullet formula) were compared to those derived from summated short-axis images of the left ventricle (Simpson's rule) during altered loading conditions in six anesthetized, intact dogs.RESULTS
Angiotensin infusion produced three different LV systolic pressures (89 ± 8 vs. 123 ± 12 vs. 151 ± 10 mmHg, P < .001). Area-Length and Bullet formula end-systolic volumes correlated with Simpson's rule volumes (r = .95 and .97; respectively). However, Bullet formula end-systolic volumes provided a significantly better agreement with Simpson's rule end-systolic volumes.CONCLUSIONS
The Bullet formula can be substituted for Simpson's rule to record magnetic resonance LV volumes during steady-state alterations in load in our intact animal model.