Effects of steal-prone anatomy on intraoperative myocardial ischemia. The SPI Research Group

Our study objective was to determine whether the presence of steal-prone anatomy conferred an increased risk in the development of intraoperative myocardial ischemia.

Coronary artery steal of collateral blood flow has been demonstrated for many vasodilators, including isoflurane, the most commonly used inhalational anesthetic agent in the United States. It has been postulated that patients with steal-prone anatomy (total occlusion of one coronary artery that is supplied distally by collateral flow from another coronary artery with a > or = 50% stenosis) may be particularly at risk for the development of intraoperative myocardial ischemia when an anesthetic with a vasodilator property is being administered.

We evaluated the risk of myocardial ischemia under isoflurane anesthesia (vs. a high dose narcotic technique using sufentanil) using continuous intraoperative electrocardiography and transesophageal echocardiography in patients with and without steal-prone anatomy undergoing coronary artery bypass graft surgery.

Sixty-two (33%) of the 186 patients had steal-prone anatomy: in 5 (8%) the collateral-supplying vessel was > or = 50% to 69% stenosed, in 24 (39%) it was > or = 70% to 89% stenosed and in 33 (53%) it was > or = 90% stenosed. The incidence of ischemia (transesophageal echocardiography or intraoperative electrocardiography, or both) was similar in patients with and without steal-prone coronary anatomy (18 [29%] of 62 patients vs. 39 [31%] of 124 patients, p = 0.87, 95% confidence interval = -0.13 to 0.17). The incidence of intraoperative ischemia was similar in patients who received isoflurane or sufentanil anesthesia (20 [32%] of 62 patients vs. 37 [30%] of 124 patients, p = 0.87). The incidence of tachycardia and hypotension was low (increases in heart rate = 9.8%, and decreases in systolic blood pressure = 10.8% of total monitoring time during the prebypass period compared with preoperative baseline values). The incidence of adverse cardiac outcome was similar in patients with and without preoperative steal-prone coronary anatomy (4 [7%] of 62 patients vs. 14 [11%] of 124 patients, p = 0.53).

These findings demonstrate that under strict hemodynamic control the presence of steal-prone anatomy does not confer an increased risk in the development of intraoperative myocardial ischemia.