Transmyocardial revascularization: an industry perspective.

e s t e r d a y . The concept of what is now called transmyocardial revascularization actually precedes the evolution of coronary artery bypass (CABG) surgery and percutaneous transluminal coronary angioplasty (PTCA). Wearn described the myocardial microanatomy (most notably the arterioluminal sinusoids, which are poorly developed in humans but a major myocardial blood supply to reptiles) as early as 1933. Soon after publication by Wearn, researchers embarked upon a fascinating, and not always successful, journey to resupply arterial blood flow to ischemic myocardium. In 1935, Beck published his animal experiments on grafting vascularized tissue, such as the parietal pericardium, to the surface of the heart as well as the effect of mechanical and non-mechanical abrasion of the epicardial surfaces , 3 as part of the grafting procedure. In 1954, Vineberg described an improvement to the technically difficult and success-limited Beck procedure. As in Beck’s procedure, Vineberg attempted to achieve indirect revascularization of the myocardium. However, Vineberg implanted the internal mammary artery into the myocardial wall, whereas Beck used vascularized flaps. Vineberg continued to refine his procedure, and gradual adoption of his technique for humans followed. The Vineberg procedure was soon to be eclipsed by a direct revascularization method: coronary artery bypass grafting. This did not, however, deter others from seeking alternative ways to indirectly revascularize the myocardium. Goldman suggested perforated U-shaped arterial grafts, with the body of the “U” positioned in the left ventricle and the ends of the “U” anastomosed into the endomyocardial surface of the ventricle. From Italy, Massimo published his work on achieving collateral circulation in the canine model using T-shaped plastic tubes. The tube was surgically implanted, with the top of the “T” placed into the myocardium and the base of the “T” protruding into the left ventricular chamber. In 1965, Sen tried less complex methods to communicate oxygenated blood supply to ischemic myocardium by perforating the heart wall with a variety of surgical tools, including coring and acupuncture needles. , 8 A few years later, in 1969, Kuzela published the results of his animal experiments using a biopsy punch to core a channel in the myocardium. Again, limited procedural success with these mechanical myocardial perforation techniques led another creative researcher, Mirhoseini, to employ a carbon dioxide laser to produce transmyocardial chann e l s . 0 , 1 1 These channels, it was speculated, would remain open and create a connection between the oxygen rich blood supply of the left ventricle and the oxygen deficient ischemic myocardium. It is remarkable to note that the larger part of transmyocardial revascularization research prior to Mirhoseini’s work was not supported by industry.