Measurement of myocardial blood flow with positron emission tomography before and after transmyocardial laser revascularization

Background-Transmyocardial laser revascularization (TMLR) has been proposed for treatment of refractory angina. It has been hypothesized that transmur al left ventricular channels created by laser improve myocardial blood flow (MBF) in the treated zones. We aimed to assess the effect of TMLR on MBF a nd coronary vasodilator reserve (CVR). Methods and Results-We measured MBF by means of PET with O-15-labeled water in 7 patients with refractory angina, Canadian Cardiovascular Society (CCS ) class 3.6+/-0.5, on 3 occasions: before and at 7.5+/-2.8 weeks (FU-1) and 34.6+/-4.7 weeks (FU-2) after TMLR performed with a synchronized, high-pow ered CO2 laser. In each study, MBF was measured at rest and during maximal intravenous dobutamine, CVR was computed as dobutamine divided by resting M BF. After TMLR, CCS class was 2.2+/-1.7 at FU-1 and 2.4+/-1 at FU-2 (P=0.04 versus pre-TMLR). Resting MBF in both lasered and nonlasered regions was u nchanged after TMLR. Dobutamine MBF at baseline was 1.45+/-0.52 and 1.55+/- 0.52 mL.min(-1).g(-1) in lasered and nonlasered regions, respectively (P=NS ), At FU-I, dobutamine MBF in nonlasered regions had increased significantl y to 1.89+/-0.82 mL. min(-1). g(-1) (P<0.05) and was higher than in lasered regions (1.51+/-0.61 mL. min(-1). g(-1); P<0.05 versus nonlasered). At FU- 2, dobutamine MBF in nonlasered regions was still higher than in lasered re gions (1.56+/-0.54 versus 1.21+/-0.72 mL. min(-1). g(-1); P<0.01). CVR was comparable in nonlasered and lasered regions at baseline and FU-1, whereas it was higher in nonlasered regions at FU-2 (1.86+/-0.67 versus 1.53+/-0.72 mL. min(-1). g(-1); P<0.05), Conclusions-TMLR has been shown to reduce angina in severely diseased patie nts. The results of our study do not support the hypothesis that the sympto matic benefit of TMLR can be ascribed to improved myocardial perfusion or C VR in lasered areas.