Evaluation of the indirect revascularization method after 3 months chronic myocardial ischemia.

Abstract

The long-term effectiveness of transmyocardial laser revascularization (TMLR) was evaluated in the setting of a severe left anterior descending artery (LAD) stenosis. To employ the chronic ischemic model, pigs underwent three operative procedures over a 13-week period. In the first operation, an operative stenosis of the LAD was created. One week later, the animals were studied at baseline by analyzing different parameters of perfusion (microspheres), function and ECG changes. Afterwards, pigs were randomized into one of three different experimental groups: animals in laser group 1 received one laser channel (n=9) and laser group 2 two channels per cm(2) (n=6) in the LAD territory (using a CO(2)-laser). Animals of the ischemic group (n=12) underwent the same procedures without TMLR-treatment. Twelve weeks later, the animals were re-studied (third operation) and killed. Additional analysis of myocardial water content and histochemistry was performed. Chronic myocardial ischemia and regional myocardial blood flow (RMBF) in laser group 2 revealed relatively higher RMBF values compared with the ischemic group (P=0.015), after 3 months, but no absolute improvement of perfusion at rest compared with baseline was observed in all experimental groups. Left ventricular stroke work index (LVSWI) at rest and under stress did not show any improvement compared with initial values in all study groups (P not significant). However, laser group 1 demonstrated relatively higher LVSWI(max) values in comparison with the ischemic group (P=0.013) as did laser group 2 (P=0.017). Regional contractility of the laser groups recovered after 3 months (which was deteriorated shortly after TMLR, P<0.001) and increased under stress compared with baseline (laser 1: P=0.015, laser 2: P=0.017). In contrast, the ischemic group did not show any difference from initial values (P not significant). The lased pigs of group 2 were less prone to intractable ventricular fibrillation (P=0.036 vs. ischemic group), and showed a significant smaller area of necrosis in the area at risk (P=0.012 vs. ischemic group). This model of chronic regional ischemia demonstrates that CO(2)-laser revascularization significantly ameliorates microperfusion and regional contractility, and diminishes the incidence of ventricular fibrillation and necrosis in the area at risk. However, it does not change the overall perfusion and global LV function.