DIFFERENTIAL RESPONSE OF THE RIGHT AND LEFT-VENTRICLE TO BETA-ADRENERGIC STIMULATION - AN ECHO-PLANAR MR STUDY IN INTACT ANIMALS

Purpose: The purpose of this study was to compare the response in cont ractility of the right (RV) and left (LV) ventricle of the heart to P- adrenergic stimulation using an echo planar MR technique. Method: In s ix sheep, RV and LV pressure-volume (P-V) relationships were construct ed simultaneously using intraventricular pressures and volumes measure d with echo planar MRI at rest and during dobutamine stress. Contracti lity changes were quantified by assessment of the end-systolic P-V rel ationship (ESPVR) and the preload recruitable stroke work (PRSW). Resu lts: Both the ESPVR and the PRSW showed a significant increase in cont ractility for both ventricles after dobutamine administration. The inc rease in contractility was significantly larger for the LV than for th e RV, both measured with the ESPVR (p < 0.0003) and the PRSW (p < 0.00 7). Conclusion: This study shows the usefulness of echo planar MRI to assess myocardial contractility of both ventricles simultaneously. Fur thermore, the study shows that P-adrenergic stimulation has a signific antly greater positive inotropic effect on LV contractility than on RV contractility.