The use of cardio-green for intraoperative visualization of the coronary circulation: evaluation of myocardial toxicity.

Direct visualization of the extent and adequacy of the coronary blood flow distribution can be performed intraoperatively with an intracoronary injection of indocyanine green dye (Cardio-Green). Because Cardio-Green is potentially toxic to the myocardium, we studied its effects on the mechanical performance of cardiac muscle, using human right atrial trabeculae contracting in vitro. In the first series of experiments, muscles were exposed to 25 mg/ml of Cardio-Green (a concentration 100 times greater than what would be used clinically); no significant alteration in cardiac mechanics was found when evaluated by the force-frequency relationship. To establish the concentration at which Cardio-Green would be toxic, an accumulated dose-response relationship was determined. When a polynomial regression analysis was done, the results best fit a parabolic curve: At high doses, Cardio-Green was found to be negatively inotropic. The estimated concentration that would evoke a 50% decrease in developed force was 41.96 mg/ml. The results show that intracoronary injection of Cardio-Green at clinical doses up to 0.3 mg/ml does not affect myocardial muscle performance. Safe intraoperative use depends on appropriate low doses.