[Usefulness of the measurement of the left-ventricular isometric relaxation time by echo-Doppler during the administration of dipyridamole or dobutamine as a method of inducing myocardial ischemia].

Myocardial isquemia prolongs ventricular relaxation. The purpose of this study was to assess the isovolumetric relaxation time of the left ventricle (IVRT) as a parameter of global ventricular relaxation, during the administration of Dipyridamol or Dobutamine intravenously. We studied 58 patients with ischemic heart disease uncovered by the administration of pharmacological agents. They were divided in two groups: 22 patients in the group of Dipyridamole, which was administered intravenously at a dose of 0.84 mg/kg during 10 minutes and 36 patients in the group of Dobutamine administered at a dose of 5, 10, 20, 30 and 40 mcg/kg/min in stepping fashion every three minutes. Coronariography was performed in all patients. The measurements of the maximal velocities of the E and A waves, as well as the deceleration time of the E wave and the pressure half time of the mitral flow did not show significant changes in both groups. If the study was positive by criterion of alteration of the wall motion, the IVRT corrected from the heart rate (IVRT/C) had an increase in 54% (p < 0.01) with respect to baseline values in the same patient in the Dipyridamole group and in the Dobutamine group the increment of the IVRT/C was 26% (p < 0.20). The sensibility (Sen), specificity (Sp) and positive predictive value (PPV) of the IVRT/C increments in detecting proximal significant obstruction of the left anterior descending coronary artery of trivascular disease in the Dipyridamole group was of 50%, 100% and 100% respectively. In the Dobutamine group the Sen was of 74%, the Sp of 60% and the PPV of 89%. Nor Dipyridamol neither Dobutamine produced a significant prolongation of IVRT/C when alterations of wall motion were absent or when the existing alterations were not exacerbated. On the basis of these results we concluded that the measurement of the IVRT/C in studies of myocardial ischemia with pharmacological provocative maneuvers is an additional useful parameter together with segmental alterations of wall motion to differentiate positive from negative studies.