Improved perfusion and contractile reserve after transmyocardial laser revascularization in a model of hibernating myocardium

Background. Transmyocardial laser revascularization (TMR) has been demonstr ated effective for relieving angina, although prior studies have yielded in consistent results regarding postoperative myocardial perfusion and functio n. This study evaluated long-term changes in myocardial perfusion and contr actile reserve after TMR in a model of hibernating myocardium. Methods. Miniswine had subtotal left circumflex coronary artery occlusion t o reduce resting blood now to 10% of baseline. After 2 weeks in the low-flo w state, positron emission tomography and dobutamine stress echocardiograph y were performed to document ischemic, viable (hibernating) myocardium in t he left circumflex distribution. Animals then had sham redo thoracotomy (n = 4) or TMR (n = 6). Six months later the positron emission tomography and dobutamine stress echocardiography studies were repeated. Results. Myocardial blood now in the left circumflex distribution as measur ed by positron emission tomography was significantly reduced in all animals after 2 weeks in the low-flow state. In animals that had TMR, there was si gnificant improvement in myocardial blood flow to the lased regions 6 month s postoperatively. No significant change in myocardial blood flow was seen in sham animals at 6 months. Dobutamine stress echocardiography after 2 wee ks of low-now demonstrated severe hypocontractility at rest in the left cir cumflex region of all animals, with a biphasic response to dobutamine consi stent with hibernating myocardium. In animals that had TMR, there was a tre nd toward improved resting function and significantly improved regional str ess function in the lased segments 6 months postoperatively, consistent wit h a reduction in ischemia. Global left ventricular wall motion at peak stre ss improved significantly as well. There was no change in wall motion 6 mon ths postoperatively in sham-operated animals. Conclusions. This study found improvements in myocardial perfusion and regi onal and global contractile reserve 6 months after TMR in a porcine model o f hibernating myocardium. This improved perfusion and function likely accou nts for the clinical benefits of the procedure. (C) 1999 by The Society of Thoracic Surgeons.