All patients had standard 12-lead electrocardiogram (ECG) recordings made at the time of electrophysiological testing using the Prucka CardioLab (GE Healthcare, Waukesha, WI) recording system using low-frequency and high-frequency filters of 0.05 and 150 Hz, respectively. Measurements were performed with electronic calipers at © 2015 American Heart Association, Inc.

Introduction Mesenchymal stem cells (MSCs) have been associated with reduced arrhythmias; however, the mechanism of this action is unknown. In addition, limited retention and survival of MSCs can significantly reduce efficacy. We hypothesized that MSCs can improve impulse conduction and that alginate hydrogel will enhance retention of MSCs in a model of healed myocardial infarction (MI). Methods and results Four weeks after temporary occlusion of the left anterior descending artery (LAD), pigs (n=13) underwent a sternotomy to access the infarct and then were divided into two studies. In study 1, designed to investigate impulse conduction, animals were administered, by border zone injection, 9–15 million MSCs (n=7) or phosphate-buffered saline (PBS) (control MI, n=5). Electrogram width measured in the border zone 2 weeks after injections was significantly decreased with MSCs (−30±8 ms, p<0.008) but not in shams (4±10 ms, p=NS). Optical mapping from border zone tissue demonstrated that conduction velocity was higher in regions with MSCs (0.49±0.03 m/s) compared to regions without MSCs (0.39±0.03 m/s, p<0.03). In study 2, designed to investigate MSC retention, animals were administered an equal number of MSCs suspended in either alginate (2 or 1 % w/v) or PBS (n=6/group) by border zone injection. Greater MSC retention and survival were observed with 2 % alginate compared to PBS or 1 % alginate. Confocal immunofluorescence demonstrated that MSCs survive and are associated with expression of connexin-43 (Cx43) for either PBS (control), 1 %, or 2 % alginate. Conclusions For the first time, we are able to directly associate MSCs with improved impulse conduction and increased retention and survival using an alginate scaffold in a clinically relevant model of healed MI.

Costa AR, Panda NC, Yong S, Mayorga ME, Pawlowski GP, Fan K, Penn MS, Laurita KR. Optical mapping of cryoinjured rat myocardium grafted with mesenchymal stem cells.