Anesthesia for laser transmyocardial revascularization

Abstract

NAKE MYOCARDIUM receives its blood supply through a network of channels that communicate directly with ventricle, rather than through epicardial vessels seen in humans. Transmyocardial revascularization (TMR) is an experimental procedure that attempts to duplicate this anatomy in patients with diffuse distal coronary artery disease unamenable to coronary artery bypass grafting (CABG) or angioplasty. For this reason, procedure has been called the snake and was first attempted in 1965 by Sen et al, 1 who used needle acupuncture to create multiple channels through ischemic myocardium. Unfortunately, these channels fibrosed and closed within weeks, offering little long-term benefit. More recently, carbon dioxide (CO2) and holmium:yttrium-aluminum garnet (Ho:YAG) lasers are being used as an alternative to needle perforations in hope that channels created by laser might epithelialize and remain patent longer. 24 If successful, this technique would provide an alternative treatment for patients with coronary artery disease refractory to conventional therapies. The following case is presented to illustrate anesthetic considerations for such a procedure. A 49-year-old, 80-kg man was experiencing class IV (Canadian Heart Association) angina, despite a four-vessel CABG operation 5 years ago and maximal medical therapy. Medical history was significant for an inferior myocardial infarction, and medications included nifedipine (20 mg three times daily), metoprolol (50 mg twice daily), isosorbide dinitrate (40 mg four times daily), amiodipine (10 mg/day), and aspirin (375 mg/ day). Recent cardiac angiography showed small, diffusely diseased coronaries, occluded vein grafts, and a patent internal mammary artery graft. Ejection fraction was 40%, and mild pulmonary hypertension was noted. Persantine-thallium scanning showed, on poststress images, defects in lateral and inferior walls of left ventricle. Reperfusion of lateral wall occurred, but inferior defect was fixed. Wall motion studies showed good motion of septum, but other walls showed considerable dyskinesia. Because patient was not considered an appropriate candidate for repeat CABG or angioplasty and his symptoms were persisting despite medical management, he was enrolled in a protocol for TMR treatment with holmium laser. Inclusion criteria for protocol were as follows: class IV angina (Canadian Heart Association); ejection fraction greater than 25%; greater than 10% reversibility in a myocardial defect located in inferior two thirds of left ventricle; and unsuitable for CABG or angioplasty. Patients were randomly assigned to either a TMR or medical treatment. In TMR group, entire left ventricle was treated with laser, not just areas of reversible ischemia.