Augmentation of coronary bypass graft flow induced by dipyridamole and its relation to bypass graft patency

To evaluate the effect of dipyridamole on coronary bypass graft flow, 10 mg of dipyridamole was injected intravenously, during the measurement of graft flow, at the time of surgery. Its concentration in serum was measured and compared with that after oral administration. In 50 individual vein grafts performed on 35 patients, graft flow increased from 65 +/- 37 to 96 +/- 55 ml/min (p less than 0.001) after the dipyridamole injection and the arterial pressure decreased slightly. In 40 grafts whose graft flow was increased by more than 10 ml/min by dipyridamole, the patency rate (at 5 weeks) was 98 per cent, whereas that of the 10 other grafts, which responded poorly, was only 50 per cent (p less than 0.01). The serum concentration of dipyridamole, 3 minutes after intravenous injection, was 1.46 +/- 0.68 micrograms/ml, while the level of orally administered dipyridamole, in 3 groups of patients who were given 50 mg, 75 mg and 100 mg, three times a day, respectively, was steady, being 0.68 +/- 0.20 micrograms/ml, 1.43 +/- 0.41 micrograms/ml and 1.73 +/- 0.50 micrograms/ml, 2 hours following ingestion. We concluded that intravenous dipyridamole increases the graft flow and that a better patency is obtained in those grafts in which the graft flow is increased by more than 10 ml/min. It is also expected that routine doses of oral dipyridamole possibly increase the graft flow after coronary bypass surgery.