Indices of intraoperative flowmetry, determining patency of grafts in the remote period after revascularization of the right coronary artery

Bazylev V.V., Nemchenko E.V., Pavlov A.A., Karnakhin V.A.

Federal Centre of Cardiovascular Surgery under the RF Public Health Ministry, Penza, Russia

The authors studied the threshold values of ultrasound flowmetry concerning composite T-grafts, combined I-grafts, and autovenous shunts during revascularization of the right coronary artery (RCA), determining high risk for the development of shunt occlusion in the remote postoperative period.

The retrospective study included a total of 223 patients subjected to revascularization of the RCA’s basin with the help of composite T-grafts, combined I-grafts, and autovenous shunts. Depending on the method of bypass grafting of the RCA and its branches, all patients were subdivided into 3 groups: Group 1 was composed of 65 patients in whom the RCA basin was revascularized by a branch of the composite T-graft, Group 2 comprised 112 patients who endured autovenous aortocoronary bypass grafting, and Group 3 consisted of 46 patients in whom the RCA basin was shunted by a combined mammarovenous I-graft. The groups had no statistically significant differences on the main clinical and demographic parameters. Intraoperative assessment of the blood flow through the coronary shunts was carried out by means of ultrasound flowmetry. The remote results were evaluated based on the findings of the control coronaroshuntography which was carried out in all patients within the terms varying from 16 to 43 months.

In the remote period in Group 1 patients (T-graft), 59 (90%) mammary shunts were patent, in Group 2 – 99 (88.4%) autovenous shunts, and in Group 3 (I-graft) 42 (95.5%) shunt were patent. Cumulative probability of freedom from shunt occlusion within the terms up to 3 years after surgery in Group 1 amounted to 82±0.5%, in Group 2 to 58±2.1%, and in Group 3 to 86±1.9%, with the differences between Group 2 and other groups being statistically significant (p=0.01). The Poisson regression analysis showed that the risk for graft occlusion increased by 10% with the resistance index in the branch of the T-graft from 4.0; by 8% with the resistance index in the autovein from 2.9; and by 3% with the index of resistance in the I-graft from 3.2.

The conclusion was made that composite T-grafts and combined I-grafts demonstrated similar results of patency within the terms up to 3 years, possessing advantages over autovenous conduits while shunting the RCA basin. The optimal index of peripheral resistance for the autovein during revascularization of the RCA basin is up to 2.9; for the combined T-graft – up to 3.2, and for the composite T-graft – up to 4.0. Probability of shunt occlusion in the remote period does not depend upon the average volumetric blood velocity (Q_mean) but is directly proportional to the value of the pulsatility index (Pi) which reflects the state of the distal bed.

KEY WORDS: coronary artery bypass grafting, right coronary artery, composite conduit, combined I-graft, autovenous shunt, average volumetric blood velocity, pulsatility index, patency of shunts.

P. 66

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