The use of a small intra-aortic balloon to increase coronary flow.

A small spherical balloon, mounted on a catheter, was positioned, via an arteriotomy, in the ascending aorta 1 cm above the aortic valve in 10 dogs. The balloon was inflated for 60 ms, through the equipment of the intra-aortic balloon pump, during various parts of the cardiac cycle. When the inflation occurred during the rapid ejection phase, the systolic component of the coronary flow increased by 32.57 +/- 5.4 per cent (P less than 0.001), resulting in a 6.69 +/- 1.14 per cent (P less than 0.001) increase of the total (effective forward) flow. The tension time index increased by 9.01 +/- 0.85 per cent (P less than 0.001). The left ventricular end-diastolic pressure and indexes of contractility did not change. When the inflation occurred during the reduced ejection phase the increase in coronary flow and tension time index was less. When the inflation occurred during the first third of diastole, there were no significant changes in the pressures and flow. In the middle third of diastole, the inflation of the balloon produced a 6.5 +/- 0.99 per cent (P less than 0.001) increase of the total flow, without significant changes in the pressures, except for a small increase in the mean diastolic aortic pressure. When the inflation occurred in the last third of diastole, the total coronary flow increased by 10.47 +/- 1.06 per cent (P less than 0.001). There was a decrease in the aortic end diastolic pressure and a 1.08 +/- 0.42 per cent (P less than 0.02) increase in the time tension index. In five dogs, additional observations were made using another mode of inflation. The balloon remained inflated during the entire diastolic period. The total coronary flow increased by 17.46 +/- 4.8 per cent (P less than 0.01), along with a small increase in the diastolic aortic pressure. Indexes of contractility did not change. In conclusion, a small spherical balloon functioning as a pump in the ascending aorta, in close proximity to the coronary ostia, can significantly increase the coronary blood flow.