Mechanical transmyocardial revascularization fails to improve myocardial function

NEW YORK (Reuters Health) – While transmyocardial revascularization (TMR) with a laser is known to improve the function of chronically ischemic myocardium, mechanical methods of creating an injury similar to that of the laser do not have the same effect.

Dr. Keith A. Horvath, from Northwestern University Medical School in Chicago, and colleagues established an area of chronic myocardial ischemia in 25 domestic pigs. The pigs were then randomized to undergo laser TMR, hot needle TMR, normothermic needle TMR, ultrasonic needle TMR, or no treatment.

Laser TMR was associated with a 75% increase in the contractility of the ischemic zone (p < 0.01), while the mechanical TMR methods did not produce a significant improvement. In fact, ultrasonic needle TMR was actually associated with a 40% decrease in contractility (p < 0.05).

Histologic analysis revealed a significant increase in ischemic zone blood vessels in the laser TMR group only, the researchers note in the December issue of The Annals of Thoracic Surgery. Furthermore, significant scarring was noted in the transmural channels created by mechanical means.

Simple mechanical or kinetic energy may not stimulate angiogenesis as profoundly as laser energy does, the authors postulate. In addition, it is possible that the injury created by mechanical means actually does more harm than good. New blood vessel formation is of little value if the myocardium is damaged so much that it cannot contract.

Ann Thorac Surg 2001;72:1997-2002.

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