Transmyocardial laser revascularization preserves regional myocardial perfusion: An MRI first pass perfusion study

Objective: It is controversial whether transmyocardial laser revascularization (TMLR) improves myocardial perfusion. Therefore, we assessed myocardial perfusion before and after TMLR with quantitative magnetic resonance perfusion imaging (MRPI) in an animal study. Methods: One week after partial occlusion of the left circumflex artery (LCx) in 12 pigs, resting perfusion (ml/g/min), perfusion reserve (PR) with adenosine, regional wall thickening (RWT), cardiac output (CO) were quantified with MRI in the LCx (lateral) and LAD (septal) dependent myocardium. Subsequently, six animals were treated with TMLR of the lateral left ventricle (LV). Six animals were left untreated. A final MR was performed 8 weeks later. MRPI data were compared to microsphere-derived blood flow and % LV necrosis (TTC). 'Normal' myocardial perfusion was assessed with MRPI in 12 non-instrumented animals. Results: Resting perfusion prior to TMLR (0.7-0.9±0.3) in the LV-lateral myocardium was preserved after TMLR (1.0±0.3) and decreased without TMLR (0.3±0.1, P<0.05). There was a significant difference (P<0.01) between the TMLR treated and untreated group. Compared to 'normals' (1.2±0.2) perfusion of the LV-lateral wall was not different after TMLR but reduced (P<0.02) without TMLR. PR was not different between TMLR-treated (1.4±0.9) and untreated (1.9±0.6) group but was reduced (P<0.04) compared to PR of 'normals' (2.7±0.8). MRPI data and microsphere-derived perfusion were significantly correlated (P<0.01). RWT in the LCx-dependent myocardium improved (P<0.02) after TMLR. CO decreased (P<0.02) and TTC-staining indicated more LV-necrosis without TMLR (6.6±1.6 vs. 3.7±1.5, P<0.01). Conclusion: TMLR preserves regional myocardial perfusion and improves function as shown with MRPI.