[The internal thoracic artery in myocardial revascularization in patients with severely depressed left ventricular function].

Introduction: In most prospective, randomized studies, severely depressed left ventricular function is found to be the independent predictor of increased morbidity and mortality after myocardial revascularization [3]. Surgical treatment in this particular group of patients results in superior long-term results [1, 2]. Internal thoracic artery (ITA) is considered to be superior compared to venous grafts in myocardial revascularization for the majority of patients with ischaemic heart disease. However, its value in patients with already severely depressed left ventricular function (EF < or = 30%) is still a matter of debate. There are no prospective, randomized studies, so far. In some studies it was shown that revascularization with ITA graft resulted in superior long-term results (10- and 15-year follow-up) in all subgroups of patients, including those with severely depressed left ventricular function [4, 5]. Some authors find it still unacceptable, if this result would be possible at the expense of higher early mortality (due to use of ITA). The purpose of this study is to analyze the early and long-term results of myocardial revascularization using ITA graft in patients with severely depressed left ventricular function (EF < 30%).

Material And Methods: Over the period from November 1986 through March 1999, 2860 pts have received ITA (alone or with additional vein grafts) for myocardial revascularization. In 431 pts EF was < or = 30% (15.1%), average EF being 25.7% (by echocardiography); 33 were women, 29 were diabetics, while average age was 56.7 +/- 8.4 years. The control group consisted of 430 pts, with similar preoperative characteristics, who received vein grafts alone.

Results: Operative mortality in the ITA group was 2.55% (11/431), and postoperative morbidity was 7.4% (32/431). In the group with vein grafts only the mortality was 3.25% (14/430) and morbidity 6.7% (29/430)--Table 2. The average postoperative hospital stay was 9.1 days (range 7-32). There was no difference in operative and postoperative parameters (extracorporeal time, ischaemic time, duration of mechanical ventilation, need for inotropic support, mortality, morbidity and hospital stay) compared to the group with vein grafts alone, except for the blood drainage--significantly higher in the ITA group--p < 0.00001)--Table 3. Multivariate analysis showed that independent predictors of unfavorable outcome were the presence of peripheral vascular disease (beta--0.9; p = 0.02) and aortic cross-clamp time (beta--0.02; p = 0.01). Long-term results in 14 pts with ITA graft operated on from 1986 to 1992 (6-12 years of follow-up) showed the survival of 92.7%.

Discussion: Superior long-term patency of ITA graft resulted in its practically routine use in myocardial revascularization. However, in some studies it was shown that ITA flow might be insufficient during the maximal effort [6]. This may result in hypoperfusion, low cardiac output syndrome and cardiac arrest. This frequently happens at the end of the operation, and may be accentuated with the use of vasopressors that can further decrease the ITA flow [9]. In patients with already severely depressed left ventricular function preoperatively, the use of vasopressors at the end of procedure when the myocardium may be quite vulnerable, is to be expected. Friesewinkel et al., [18] showed that there was an impairment of the regional contractility of the left ventricle early (up to 4 hours) after myocardial revascularization, when one or both ITA grafts were used. Since this was not the case if vein grafts were used, they advised to be careful in patients with "depressed left ventricular function". However, Elefteriades et al., [1] found no higher mortality in patients with "bad left ventricle" in whom ITA was used, but point out that patients with elective operation and without need for intensive care treatment preoperatively had much better outcome. Jagaden et al., [19] found very good results in these patients, after the routine use of ITA, during a 20-year follow-up. In our study EF < or = 30% was present in 861 patients, 431 with ITA graft and 430 with vein grafts only. There was no difference between groups considering all possible preoperative and operative factors of importance for the outcome. We found no increased early morbidity and mortality in patients in whom ITA was used compared to patients with vein grafts only. In patients operated on from 1986-1992 (follow-up of 6-12 years), we noted the survival of 92.7%. This was not statistically different compared to patients with vein grafts (survival of 88.9%). Despite the small number of patients, we found these long-term results very encouraging.

Conclusion: ITA graft is a very good and absolutely acceptable choice in patients with severely damaged left ventricular function, particularly if we consider its long-term superiority. These pts should not be deprived of the long-term benefit of ITA graft, since early results are very good.