OBJECTIVE To evaluate the effect of coronary sinus diastolic balloon pulsation (CSDBP) on acute myocardial ischemia and infarction. It was hypothesized that this procedure would improve retrograde flow to ischemic areas and allow for more complete oxygen exchange and venous washout of metabolites, with elevated coronary sinus pressure and retrograde pulsation. METHODS This two-part study was done on 10 dogs. First, CSDBP was applied to normal myocardium by a balloon catheter and a pump system at beat to beat cardiac cycles of 1:1, 2:1 and 3:1. Then coronary ischemia was obtained by coronary artery ligation and the procedure was repeated. Electrocardiographic (ECG), arterial and coronary sinus pressure alterations were monitored continuously, and arterial, mixed venous and coronary sinus blood lactate concentrations were measured at each stage of the study. RESULTS In the first stage no hemodynamic deterioration was observed. In the second stage, mean ECG-ST segment elevation was 6.30+/-0.95 mm (P<0.01) and coronary sinus blood lactate concentration increased to 5.37+/-0.37 mmol/L from 1.95+/-0.31 mmol/L (P<0.01). ECG-ST segment elevation decreased to 3.73+/-0.64 mm and coronary sinus blood lactate concentration decreased to 4.79+/-0.28 mmol/L (P<0.05) with 1:1 beat to beat CSDBP. ECG-ST segment elevation decreased to 2.95+/-0.73 mm and coronary sinus blood lactate concentration decreased to 4.4+/-0.22 mmol/L with 2:1 CSDBP. ECG-ST segment elevation decreased to 3.6+/-0.42 mm and coronary sinus blood lactate concentration decreased to 4.17+/-0.22 mmol/L with 3:1 CSDBP as well. CONCLUSIONS Results showed that CSDBP technique lowered the increased ECG-ST segment elevation and myocardial lactate production.