Effect of transmyocardial laser revascularization on chronic ischemic hearts in sheep

We investigated the effect of transmyocardial laser revascularization (TMR) on myocardial function and regional blood flow in an animal model of ischemic heart disease.

Chronic ischemia was induced in 11 sheep by the application of coronary stenosis on the left anterior descending (LAD) and circumflex coronary artery (LCX). Ten weeks later, in six of them, transmyocardial channels were created in the anterior free wall and in the posterior wall of the left ventricle. Five animals served as controls. The myocardial function was assessed by echocardiography taken at baseline and every 2 weeks after coronary stenosis and after TMR. Myocardial perfusion was measured by colored microspheres, injected at baseline, immediately after coronary stenosis, before and after TMR, and at 20 weeks after coronary stenosis. The hearts were retrieved at 20 weeks for light microscopic examination.

The left ventricular end-diastolic and end-systolic cavity area was elevated 20 weeks after coronary stenosis in the control and TMR groups. There was no difference between groups (analysis of variance; ANOVA, non-significant). The wall thickening fraction (WTF) decreased progressively and significantly after coronary stenosis in both groups. The WTF was further acutely reduced by TMR, and recovered gradually to the pre-TMR level. No significant difference in WTF was observed between the TMR and control groups. The resting myocardial blood flow was significantly increased by TMR at 20 weeks (P=0.03). Light microscopic examination revealed channel patency in 49% of the laser scars at 10 weeks post-TMR. A dense capillary network was observed at the edges of the surrounding scar.

In an experimental model of ischemic heart disease, TMR developed angiogenesis in the lased channels, but, however, failed to improve myocardial function.