Intra-aortic balloon pumping recruits graft flow reserve by lowering coronary resistances.

BACKGROUND

The intra-aortic balloon pump (IABP) is used worldwide as an anti-ischemic strategy and to reduce myocardial workload. However, whether IABP augments coronary flow after coronary bypass via a passive increase in diastolic pressure or an active response of the coronary bed remains uncertain.

METHODS

We analyzed transit-time flow measurements and the contemporary changes in coronary resistances obtained during 1:1 IABP and during its cessation in 144 consecutive patients receiving prophylactic IABP before isolated coronary artery bypass grafting (n=340 graft segments).

RESULTS

Normally functioning grafts showed lower coronary resistances, greater percentage decrease in resistance, and greater increases in average maximum diastolic and mean flow during 1:1 IABP compared with IABP cessation (P<.001). Arterial and sequential saphenous vein grafts showed better flowmetry and greater reductions in coronary resistances compared with single venous grafts. Accordingly, graft flow reserve (defined as mean flow during 1:1 IABP/mean flow with IABP off) was recruited (graft flow reserve >1) during 1:1 IABP in all normally functioning grafts, with higher values in single arterial or sequential saphenous vein grafts than in single venous grafts (both P<.001). Coronary resistances were higher in 7 failed grafts versus normal-functioning grafts at baseline; these did not decrease during 1:1 IABP and showed worse transit-time flow results.

CONCLUSIONS

IABP recruits graft flow reserve by lowering coronary resistance in functioning grafts. Arterial and sequential venous grafts showed greater reduction in coronary resistance compared with single saphenous grafts.