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Objective: The early benefits resulting from transmyocardial revascularization (TMR) may be related to acute sympathetic dennervation. We hypothesized that TMR in conjunction with coronary artery bypass grafting would improve local coronary flow reserve thereby increasing myocardial runoff and blood flow within bypass grafts placed to TMR treated areas.
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Robert S. Poston, Junyan Gu, Seeta Kallam, James Brown.
Division of Cardiac Surgery, University of Maryland School of Medicine, Baltimore, MD, USA.
Methods: Bypass grafts were placed in 125 OPCAB patients. Intraoperative blood flow was measured in each graft using transit time technology (Medistim) 10 minutes after protamine administration with blood pressure controlled between 110-130 mmHg systolic (timepoint1). Fourteen of these patients that were noted to have a graft blood flow <40 ml/min then underwent TMR (10-12 holes) in the myocardial region served by that graft. Following another 10 minute stabilization period after TMR, blood flow was reassessed (timepoint2) and compared to flow in grafts placed outside the treated region. A control group (n=14) was selected from the cohort based on having a graft with flow <40 ml/min and similar age, incidence of comorbidities, ejection fraction, and inotropic requirements. A second graft flow measurement was obtained just prior to chest closure (timepoint2) without TMR treatment.
Results: In 14 patients that underwent TMR for an initial graft flow <40 ml/min, there was a 48% increase in flow noted between the two timepoints (figure). Flow increased 23% in grafts placed in the nontreated regions of TMR-treated patients and decreased by 2% between timepoints in those that did not undergo TMR.
Conclusions: TMR acutely improves venous bypass graft blood flow in territories with reduced myocardial runoff.Acute sympathetic dennervation following TMR may provide further mechanistic insight into the acute clinical benefits that have been documented when TMR is utilized as an adjunct to coronary artery bypass grafting. 
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