Transcoronary pacing: Reliability during myocardial ischemia and after implantation of a coronary stent

BACKGROUND: Transcoronary pacing is a useful therapeutic option for the treatment of unheralded bradycardias in the setting of percutaneous coronary interventions (PCI). OBJECTIVES: In the present study, we investigated the influence of stent implantation and transient myocardial ischemia on the feasibility of transcoronary pacing in a porcine model. METHODS: 7 adult pigs underwent a percutaneous coronary intervention with implantation of a coronary stent under general anaesthesia in an animal catheterization laboratory. Transcoronary pacing was established by using a standard guidewire isolated with an angioplasty balloon positioned in the periphery of the right coronary artery serving as the cathode. As the indifferent anode, a skin patch electrode at the back of the animal was used. The reliability of transcoronary pacing was assessed by measurement of threshold and impedance data and the magnitude of the epicardial electrogram at baseline, after implantation of a coronary stent and finally during myocardial ischemia. RESULTS: Effective transcoronary pacing could be demonstrated in all cases with the standard unipolar transcoronary pacing setup yielding a low pacing threshold at baseline of 1.3+/- 0.8V with an impedance of 283+/- 67Omega. Implantation of a coronary stent did not influence the pacing threshold (1.0+/- 0.4V) and impedance (262+/- 63Omega). Acute myocardial ischemia lead to a significant but clinically nonrelevant increase of the pacing threshold to 2.0+/- 0.6V and a drop in pacing impedance (137+/- 39Omega). CONCLUSIONS: Transcoronary pacing in the animal model is not affected by implantation of a coronary stent in the same vessel used for pacing. Despite a significant increase in pacing threshold, the transcoronary pacing approach is reliable in acute myocardial ischemia during a percutaneous coronary intervention.