Echocardiographic contrast agents: effect of microbubbles and carrier solutions on left ventricular contractility

Recently, there has been a resurgence of interest in the use of contrast-enhanced echocardiography as a means of noninvasively assessing myocardial perfusion. However, if injections of echocardiographic contrast agents are to be used for this purpose it is essential that they are not intrinsically toxic to the heart. In this study, the left ventricular end-systolic wall stress-rate-corrected velocity of fiber shortening relation, a load independent index of contractility, was studied in nine dogs. Two-dimensional and targeted M-mode echocardiographic as well as central aortic pressure tracings were made during echocardiographically gated, pressure- and volume-controlled aortic root injections of nonsonicated and sonicated Renografin-76, saline and dextrose 70% (n = 6), and sonicated and hand-agitated Renografin-76/saline mixture (n = 5). Two of nine dogs received all agents. Off-line computer videodensitometric analysis documented myocardial perfusion. In all cases, data were obtained at control and 5 and 15 seconds after injection. Additional data were collected at 25 seconds after injection for the Renografin-76/saline mixture. Alterations in contractility were measured relative to control as changes in rate-corrected velocity of fiber shortening after afterload (measured as end-systolic wall stress) was eliminated as a confounding variable. Under no condition did saline or Renografin-76 cause alterations in left ventricular contractility. Nonsonicated and sonicated dextrose 70% increased left ventricular contractility at 15 seconds but not at 5 seconds after injection. Hand-agitated Renografin-76/saline mixture induced a negative inotropic effect at 5 and 15 seconds after injection.(ABSTRACT TRUNCATED AT 250 WORDS)