Effect of venous retroperfusion on experimental myocardial ischemia in the open-chest pig.

Venous retroperfusion, by arterialization of the coronary sinus or the vein accompanying an ischemic artery, has been suggested as an alternative method of myocardial revascularization in patients with severe coronary disease in whom direct revascularization would be an unacceptable risk or technically impossible. This study was carried out to assess whether or not venous retroperfusion can increase myocardial blood flow in the area of ischemia after sudden occlusion of a normal coronary artery in an animal, the pig, with a coronary vasculature similar to that of humans. It was found that net flow measured with an electromagnetic flowmeter through either an aorta-to-coronary sinus shunt or an aorta-to-left anterior descending coronary vein shunt after occlusion of the left anterior descending artery was at first high but rapidly decreased toward zero flow within 1 hr. Blood flow in the ischemic region measured by the microsphere method 20 min after coronary occlusion did not increase. This disparity between electromagnetic flow and regional flow suggests that there are venous-to-thebesian or venous-to-venous shunts into the systemic and pulmonary circulation through vessels greater than 14 micron. It is unlikely that effective oxygen or metabolite exchange would occur in vessels this size.

Acute vasodilator therapy increases renal clearance of digoxin in patients with congestive heart failure.

We studied the effect of vasodilator therapy on renal digoxin clearance in patients with chronic congestive heart failure. Intravenous administration of nitroprusside or hydralazine to eight patients with severe heart failure produced the expected increase in cardiac output and a decrease in central circulatory pressure. Renal clearance of sodium para-aminohippurate and estimated renal blood flow increased without a change in glomerular filtration rate. Total renal clearance of digoxin increased by 50% during vasodilator therapy. Thus, acute administration of vasodilator increases renal digoxin clearance without changing glomerular filtration rate, suggesting an increase in tubular secretion of digoxin. Long-term vasodilator therapy may alter the maintenance dosage of digoxin required for optimal treatment of patients in congestive heart failure.

Renal effects of nitroprusside and hydralazine in patients with congestive heart failure.

The acute effects of nitroprusside infusion and intravenous hydralazine on renal hemodynamics and function were evaluated in nine male patients with severe, low cardiac output, congestive heart failure (CHF). Both drugs resulted in marked systemic hemodynamic improvement. Nitroprusside had a more profound effect on pulmonary artery pressure, while hydralazine produced a greater elevation in cardiac output. Significant decreases in both systemic and pulmonary vascular resistance and pulmonary capillary wedge pressure with increases in stroke volume and stroke work index were noted with both drugs. Total renal resistance decreased and renal blood flow (RBF) significantly increased with both drugs, while the distribution of cardiac output to the kidney remained depressed. Glomerular filtration rate (GFR) did not change significantly with either drug, although increases in GFR were seen in selected patients in whom RBF increased by more than 10% from control. The fraction of plasma filtered decreased toward normal with both drugs and excretion of total cations was significantly increased. These changes all represent improvements in systemic and renal hemodynamic abnormalities occurring in patients with CHF; their maintenance during long-term therapy would facilitate patient management.