Transmyocardial laser revascularization - Morphology, pathophysiology and historical background of indirect myocardial revascularization

Under normal conditions the coronary system of the human heart is not hermetically isolated from the surrounding structures nor the ventricles, but is in various ways connected to the adjacent arteries and the cardiac chambers. These natural connections have been models for most surgical efforts to revascularize the myocardium. Numerous anastomoses between the aorta and the coronary branches functionally resemble aorto-coronary bypass grafts. Coronaro-ventricular anastomoses do also exist in the myocardium and therefore transmyocardial laser revascularization should allow blood to penetrate from the ventricle into the myocardium. This process should not be called ''reptilization'' of the human heart, as in large reptilian hearts the nutrition of an extensive amount of myocardium only by diffusion is highly unlikely. Transmyocardial laser revascularization results in a relevant reduction of clinical symptoms and an increase of exercise capacity in approximately two thirds of the patients treated. Objective data of enhanced myocardial perfusion as assessed by positron emission tomography and stress echocardiography has up to now only been presented by smaller studies. Open laser channels are rarely visualized by conventional ventriculography for the limited resolution of the technique. Possibly contrast-echocardiography may offer a more appropriate option to proof the systolic filling of the laser channels, as recently reported in patients. This would allow a correlation between clinically successful revascularization and functioning channels in contrast to an early or late failure due to the closure of the channels. As to the current opinion, transmyocardial laser revascularization is no alternative to established medical, interventional or surgical therapies but may in conjunction with bypass surgery or as a sole procedure offer a new option for those patients, who were recently considered to be refractory to conventional treatment. Experimental studies in particular should contribute to the understanding of therapeutic mechanisms and lead to standardized indications in the surgical treatment of end-stage coronary heart disease. Even though in transmyocardial laser revascularization the perioperative risk depends mainly on the degree of cardiac disease and the overall state of the patient, an impaired left ventricular function is per se no exclusion criterium, if viable myocardium is detectable. Many questions concerning indications, long-term prognosis and pathophysiological mechanisms are still open to discussion and have to be answered in order to find standardized applications for treatment of end-stage coronary artery disease.