Dissociation between improvement in angina pectoris and myocardial perfusion after transmyocardial revascularization with an excimer laser.

The original goal of creating myocardial channels was to revascularize ischemic tissue, and hence the term transmyocardial revascularization (TMR) was used. Although clinical trials have consistently reported a reduction in angina, 1,2 the evidence for revascularization has been conflicting. 1‐3 The first revascularization hypothesis was that channels would create a reptilian-like circulation in mammalian hearts, allowing immediate blood flow from the ventricular cavity through channels and into the tissue via sinusoidal spaces. 4 The hypothesis was discredited because (1) many studies found no acute perfusion, 5 (2) the existence of sinusoids in normal human hearts has never been documented, 6 and (3) channels made with carbon dioxide and holmium:yttrium-aluminiumgarnet (YAG) lasers, the devices most often used, become occluded by fibrosis. 7,8 TMR with these infrared lasers provokes a vasculogenic/angiogenic response and thus generates a second revascularization hypothesis. However, whether such vascular growth increases perfusion is unknown. In contrast to the closed channels found after infrared laser TMR, some animal studies have reported open channels with vascular connections to surrounding myocardium several months after TMR with ultraviolet lasers. 9,10 We speculated that after ultraviolet laser TMR, increased blood flow might be detected in patients. Two trials using ultraviolet excimer lasers reported a 2-class reduction in patients’ Canadian Cardiovascular Society (CCS) functional class; however, neither study assessed perfusion. 11,12 On the other hand, a case report, in which excimer laser TMR was performed together with bypass graft surgery, claimed improved perfusion. 13 Thus, we examined the effect of excimer laser TMR with an emphasis on perfusion assessment. ••• Ultraviolet laser TMR was performed in 7 patients (4 men and 3 women, aged 62 6 4 years). Patients selected for the study had regions of reversibly ischemic myocardium identified by single-photon emission computed tomography (SPECT). In addition, catheterization revealed arteries that were considered unsuitable candidates for either bypass surgery or angioplasty and that supplied viable tissue. The patients’ CCS functional class and treadmill exercise time were determined before TMR and at follow-up. A xenon chloride excimer laser (l 5 308 nm; AccuLase, Inc., Carlsbad, California) was used to make channels at a pulse energy of 9 mJ, a pulse width of 40 ns, and a pulse rate of 240 Hz. The energy was coupled into a 600-mm diameter optic-fiber system, which was advanced at a velocity of 1.55 cm s 21 . Patients were prepared for anesthesia and surgery in a standard manner. Hearts were exposed by a left thoracotomy, usually through the fifth intercostal space. Any adhesions were dissected and the heart exposed. The number of channels made was determined by the size of the apparent perfusion defect on stress. Transesophageal echocardiography was used to assess myocardial wall thickness and hence set the advancement distance of the fiber delivery system. In addition, transesophageal echocardiography was used to assess transmural penetration of the optic fiber, as indicated by the presence of bubbles in the ventricular cavity. SPECT data were acquired as previously described. 14 Briefly, a single-detector camera (Orbiter, Siemens, Hoffman Estates, Illinois) fitted with a lowenergy high-resolution collimator was used in a stepand-shoot rotation mode with 32 projections over a 180° range. For each projection, data were collected over 40 seconds for gated SPECT. The patients’ cardiac images were collected from a rest thallium-201