C C Canver1, D M Heisey, R D Nichols, S D Cooler, G M Kroncke. 1. Section of Cardiothoracic Surgery, William S. Middleton Memorial Veterans Hospital, University of Wisconsin School of Medicine, Madison 53792-3236, USA.
Abstract
BACKGROUND: Although the internal thoracic artery (ITA) graft is well known for its benefit of enhancing patient longevity after coronary artery bypass grafting (CABG), whether its superior patency is associated with improved patient survival at all levels of left ventricular function is unknown. The purpose of this study was to determine whether the use of ITA grafting during CABG confers improved survival benefit to patients with impaired preoperative left ventricular function. METHODS: A retrospective chart review was performed in 966 patients who had undergone isolated primary CABG between 1984 and 1995. The study population included 320 patients with only venous conduits (no-ITA group) and 646 patients with at least one ITA conduit (ITA group). A Cox partial likelihood approach was used to model the instantaneous mortality risk ratios as functions of ITA use and preoperative ejection fraction (EF). The forward stepwise regression model specifically examined the following potential confounders in the risk analyses: year of operation, patient age, weight, body surface area, graft location, number of grafts, perfusion time, ischemia time and Veterans Administration preoperative cardiac surgical risk estimates. RESULTS: Early (30-day) mortality in the ITA group (0.5%) was lower than the no-ITA group (4.1%) (p=0.0004). While 91% of the ITA group patients were still alive, only 70% of the no-ITA group patients were long-term survivors (p=0.0001). The ITA risk ratios for the increasing proportions of EF were not the same. In patients with E<0.40, the ITA risk ratio, 2.96, was significantly different (p=0.0001). It was only for EF >0.46, a significant survival benefit due to an ITA graft could be detected. The ITA-EF relationship was not confounded by the inclusion of those potential confounding variables in the model. CONCLUSIONS: Patient survival after CABG using an ITA graft may be affected by the level of preoperative EF. The internal thoracic artery-specific patient survival benefit appears to be less in a patient with poor left ventricular function.
BACKGROUND: Although the internal thoracic artery (ITA) graft is well known for its benefit of enhancing patient longevity after coronary artery bypass grafting (CABG), whether its superior patency is associated with improved patient survival at all levels of left ventricular function is unknown. The purpose of this study was to determine whether the use of ITA grafting during CABG confers improved survival benefit to patients with impaired preoperative left ventricular function. METHODS: A retrospective chart review was performed in 966 patients who had undergone isolated primary CABG between 1984 and 1995. The study population included 320 patients with only venous conduits (no-ITA group) and 646 patients with at least one ITA conduit (ITA group). A Cox partial likelihood approach was used to model the instantaneous mortality risk ratios as functions of ITA use and preoperative ejection fraction (EF). The forward stepwise regression model specifically examined the following potential confounders in the risk analyses: year of operation, patient age, weight, body surface area, graft location, number of grafts, perfusion time, ischemia time and Veterans Administration preoperative cardiac surgical risk estimates. RESULTS: Early (30-day) mortality in the ITA group (0.5%) was lower than the no-ITA group (4.1%) (p=0.0004). While 91% of the ITA group patients were still alive, only 70% of the no-ITA group patients were long-term survivors (p=0.0001). The ITA risk ratios for the increasing proportions of EF were not the same. In patients with E<0.40, the ITA risk ratio, 2.96, was significantly different (p=0.0001). It was only for EF >0.46, a significant survival benefit due to an ITA graft could be detected. The ITA-EF relationship was not confounded by the inclusion of those potential confounding variables in the model. CONCLUSIONS:Patient survival after CABG using an ITA graft may be affected by the level of preoperative EF. The internal thoracic artery-specific patient survival benefit appears to be less in a patient with poor left ventricular function.