Functional comparison of transmyocardial revascularization by mechanical and laser means

Background. As a result of the clinical benefit observed in angina patients treated by transmyocardial revascularization (TMR) with a laser, interest in mechanical TMR has been renewed. Although the injury induced by mechanic al TMR is similar to laser TMR, the resultant impact on myocardial contract ility is unknown. The purpose of this study was to determine whether mechan ical TMR improves ventricular function as compared with laser TMR in chroni cally ischemic myocardium. Methods. After establishing an area of chronic myocardial ischemia, 25 dome stic pigs were randomized to treatment by: excimer laser (group I), a hot n eedle (50 degreesC) (group II), a normothermic needle (group III), an ultra sonic needle (40 KHz) (group IV), or no treatment (group V). All devices cr eate a transmural channel of the same diameter; 22 +/- 1 transmural channel s were created in each animal. Regional myocardial contractility was assess ed by measuring ventricular wall thickening at rest and with dobutamine str ess echocardiography. Six weeks after revascularization, the animals were r estudied at rest and with stress. Postsacrifice and histologic analysis of angiogenesis and TMR effects was then assessed. Results. Laser TMR provided significant recovery of ischemic myocardial fun ction. This improvement in contractility after laser TMR was a 75% increase over the baseline function of the ischemic zone (p < 0.01). Mechanical TMR provided no significant improvement in function posttreatment. In fact, TM R achieved with an ultrasonic needle demonstrated a 40% worsening of the co ntractility versus the pretreatment baseline (p < 0.05). Histologic analysi s demonstrated a significant increase in new blood vessels in the ischemic zone after laser TMR, which was not demonstrated for any of the other group s (p < 0.05). Additionally, evaluation of the mechanical TMR channels demon strated significant scarring, which correlated with the functional results. Conclusions. Using devices to create an injury analogous to the laser, mech anical TMR failed to improve the function of chronically ischemic myocardiu m. Only laser TMR significantly improved myocardial function. (C) 2001 by T he Society of Thoracic Surgeons.