Ultrastructural and immunohistochemical analysis of early myocardial changes following transmyocardial laser...

Transmyocardial laser revascularization (TMR) has demonstrated significant relief in patients presenting with refractory angina. However, the mechanism by which TMR improves clinical symptoms is unclear. This study analyzes the early immunohistochemical and ultrastructural features of the human myocardium following TMR.

Specimens of myocardium that contained laser channels were removed in toto at autopsy from three male patients, ages 41, 57, and 65 (mean age 55.8) who had died 1 to 11 days (mean 6.8) following laser revascularization. Consecutive parallel sections of specimens were stained with cell-type specific antibodies to CD3 (to identify T-lymphocytes), CD68 (macrophages), Factor VIII (endothelial cells), and myosin (myocytes). Additionally, adjacent areas of myocardium that contained laser channels were processed and analyzed by transmission electron microscopy.

The internal lining surface of laser channels was composed of vacuolized and condensed myocardial debris. No obvious connections were noted between laser channels and the ventricular cavity. No endothelialization of channels was observed, whereas the adjacent noninjured myocardium demonstrated microvessels lined by well-preserved endothelial cells. The laser channels were surrounded by zones of necrotic cardiomyocytes.

Our observations suggest that laser channels are not lined by endothelial cells during the early stages following TMR. Mechanisms other than direct myocardial perfusion from the ventricular cavity by patent endothelialized channels may explain the immediate relief from angina provided by TMR.