Effects of transmyocardial laser revascularization using a prototype pulsed CO₂ laser on contractility and perfusion of chronically ischemic myocardium in a porcine model

The purpose of this study was to test a new prototype pulsed CO₂ laser to be used for transmyocardial laser revascularization (TMR). We want to determine whether it can reduce thermal damage and mitigate induced ischemia with improvement in contractile reserve of the heart as evidenced by contrast echocardiography at rest and under dobutamine stress. TMR is an emerging surgical strategy for treatment of myocardial ischemia not amenable to conventional percutaneous or surgical revascularization. Eleven pigs underwent ameroid occluder placement on the origin of the circumflex coronary artery. Six weeks later occlusion of the circumflex coronary artery was documented. TMR was then done on ten pigs using a prototype pulsed CO₂ laser that delivered 8-12 joules energy in 1.5 ms with a spot size of 1 mm. Six weeks after TMR the pigs were restudied and sacrificed. The animals developed significant ischemia after six weeks of ameroid occlusion, at rest (p = 0.01) and at peak stress (p = 0.004). Wall motion for the ischemic segments improved significantly six weeks after TMR at peak stress (p = 0.02). TMR results in an improvement in wall motion in our model of chronic ischemia and improves WMSI significantly during induced stress than at rest.