The effect of time and of vasoactive drugs on capillary leakage induced during myocardial contrast echocardiography.

BACKGROUND Premature ventricular contractions (PVC), capillary leakage, and petechial hemorrhage can occur during myocardial contrast echocardiography (MCE). The effects occur as a result of the interaction of contrast agent microbubbles and the ultrasound, but the detailed etiology of the effects is not yet clear. This study tested the hypothesis that the capillary leakage results from a physiological response to injury, which might be protracted and modulated by vasoactive drugs. METHODS Hairless rats were anesthetized and transthoracically scanned with a diagnostic ultrasound system (GE Vingmed System V) at 1.7 MHz with 1:4 triggered frames at end systole. The scan head and rats were mounted in a 37 degrees C water bath to assure free-field conditions and placement of the heart at a similar focal distance as humans. A tail vein was cannulated for injections of Optison contrast agent, vasoactive medications, and Evans Blue dye (EB). EB was injected as a marker of capillary leakage before or after scanning. RESULTS PVCs, petechia, and capillary leakage occurred during ultrasound exposure of microbubbles in myocardium, with no effects detected in shams. The influence of the vasoactive medications propranolol and isoproterenol on the effects did not support the hypothesis. Capillary leakage occurred during and postexposure, but diminished for EB injection 20 minutes after scanning with or without isoproterenol pretreatment. CONCLUSION MCE induced PVCs, petechia, and capillary leakage, all of which ended immediately or within 20 minutes after the examination. Contrary to the hypothesis of a physiological mechanism, the capillary leakage appears to be primarily a mechanical effect rather than a physiological response.