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.