Preoperative risk models for minimally invasive coronary bypass: a preliminary study

Available risk assessment models are designed for standard coronary artery bypass grafting. We hypothesized that minimally invasive coronary bypass could improve on predicted outcome in extremely high-risk patients (Parsonnet score > 20%) by the current risk models.

From September 1996 to September 1997, 27 consecutive extremely high-risk patients underwent minimally invasive coronary bypass. Seventeen patients were male; age was 73 +/- 12 years, and 63% of patients were older than 75 years. Left ventricular ejection fraction was 33.7% +/- 15% and 63% had an ejection fraction of less than 35%. The predicted 30-day mortality according to the System 97 model was 25.6% +/- 11.3%. The Parsonnet risk score was 36.2% +/- 11%; the predicted length of stay in the hospital was 15.3 +/- 3 days. The predicted risk of stroke according to the Multicenter Perioperative Stroke Risk Index was 22.3% +/- 11.7%.

Minimally invasive coronary bypass was isolated in 20 patients and integrated with angioplasty and stenting in 7 patients. The observed 30-day mortality was 0% (P < .01 vs predicted): at an average follow-up of 10.8 +/- 4.1 months, 26 patients (96.3%) are alive without angina; one patient with acquired immunodeficiency syndrome died on postoperative day 40 of acute pancreatitis. No patient had a stroke or neurologic deficit (P < .01 vs predicted). Patency of internal thoracic artery anastomosis was confirmed by angiography in all 27 patients. No patient required reoperation. Eighteen patients (67%) were extubated in the operating room. The observed length of hospital stay after minimally invasive coronary bypass was 3.8 +/- 2.6 days (P < .01 vs predicted).

On the basis of our results on a relatively small series of patients, we suggest that risk models geared for standard coronary bypass grafting may not be appropriate for minimally invasive coronary bypass.