Optimizing of transcoronary pacing in a porcine model.

Background: Transcoronary pacing for the treatment of bradycardia during percutaneous coronary intervention (PCI) is not well established, but may be a useful technique in interventional cardiology. We developed a porcine model to examine the feasibility and efficacy of transcoronary pacing during PCI.

Methods And Results: Eight pigs under general anesthesia underwent unipolar transcoronary pacing with a standard floppy guidewire in a coronary artery (as the cathode) and a skin patch electrode (as the anode). We examined the effect of skin-patch position (groin vs. anterior or posterior chest wall), the presence of an angioplasty balloon on the guidewire and also which coronary artery was "wired" on the efficacy of pacing as assessed by capture and threshold data. Pacing with the bare guidewire and a maximum output of 10 V was successful in 54% of the animals with a groin patch and the anterior chestwall patch, but in 100% with a posterior chest-wall patch. The pacing thresholds were 8.3 +/- 2.2 V, 7.6 +/- 2.8 V and 3.4 +/- 2.4 V with the patch in these sites, respectively. With an angioplasty balloon over the guidewire, pacing efficacy increased to 100% (irrespective of the target vessel or patch location) and pacing thresholds were significantly reduced (p < 0.05) to 2.7 +/- 1.5 (with a groin patch) and 1.0 +/- 0.7 V (with a posterior chestwall patch). With optimal pacing set-up (posterior chest-wall patch and angioplasty-balloon insulation), pacing thresholds were similar to those obtained with standard bipolar transvenous pacing at 1.2 +/- 0.8 V. We did not observe any adverse effects of coronary pacing. Skeletal muscle contraction was only generated at high-output levels.

Conclusions: This pig model examines the practicalities of transcoronary pacing and shows that this technique can produce 100% capture at thresholds comparable to the transvenous approach. This technique may have a role during PCI, particularly in an emergency situation.