Biventricular distribution of cold blood cardioplegic solution administered by different retrograde techniques

Although retrograde cardioplegia has been shown to provide adequate overall protection to the myocardium, delivery of cardioplegic solution to the right ventricle and septum is poor. We used an animal model of occlusion of the left anterior descending coronary artery to study the effects of modifying the conditions of retrograde cardioplegia administration on delivery to the right and left ventricles. Adult mongrel dogs (n = 12) were each given five retrograde injections of microsphere-labeled cardioplegic solution at 10-minute intervals. Four injections were made directly into the coronary sinus with ostial balloon occlusion at the following dosages and pressures: (1) 10 ml/kg at 30 mm Hg, (2) 20 ml/kg at 30 mm Hg, (3) 10 ml/kg at 50 mmHg, and (4) 20 ml/kg at 50 mm Hg. A fifth dose (20 ml/kg) was given directly into the right atrium at 50 mm Hg. Delivery of cardioplegic solution to the left and right ventricles was significantly reduced when the right atrial route was compared with the coronary sinus route at the same dosage and pressure (for left ventricle, 6.0% +/- 1.4% versus 22.7% +/- 11.4%/100 gm, p less than 0.001; for right ventricle, 0.7% +/- 0.2% versus 4.1% +/- 0.4%/100 gm, p less than 0.001). Septal delivery was less than that to the anterior and posterior left ventricle (10.4% +/- 1.3% versus 30.3% +/- 3.9% and 27.9% +/- 3.1%/100 gm, p less than 0.0001) for all injections. Delivery to the body of the right ventricle was less than that to the inflow and outflow tracts (1.8% +/- 0.2% versus 4.5% +/- 0.7% and 8.4% +/- 1.5%/100 gm, p less than 0.0001). These results indicate that, in this model, (1) the right atrial route provides less overall cardioplegic solution to both ventricles than direct retrograde coronary sinus cardioplegia and (2) regional abnormalities in distribution with direct retrograde coronary sinus cardioplegia are not affected by changes in the dosage or pressure of injection.