BS10 Cardiac pacing location- optimisation of optical mapping protocols and pacemaker lead position

Introduction Whole heart optical mapping allows fluorescent based cardiac electrophysiology measurement at high spatial-temporal resolution. Epicardial pacing site during optical mapping may affect conduction and repolarisation dynamics, altering action potential morphology. The effect of pacing site on overall ventricular electrophysiology and apico-basal dispersion was investigated to 1) determine the optimal epicardial pacing site for improved cardiac electrophysiology assessment, and 2) to consider clinical implications of epicardial pacing location. Methods Isolated mouse whole hearts were optically mapped using voltage-sensitive dye, di-4-ANEPPS. Hearts were paced epicardially using bipolar electrodes at the apex, centre or base of the ventricles, incrementally from 150 ms to 80 ms pacing cycle length. Results Activation time was qualitatively inversely correlated with action potential duration. Apex paced hearts exhibited significantly higher conduction velocity compared to central (76.53 ± 5.474 cm/s vs 58.53 ± 2.758 cm/s, p<0.01) and base (76.53 ± 5.474 cm/s vs 56.66 ± 2.913 cm/s, p<0.05) pacing respectively (figure 1). Furthermore, apex pacing demonstrated significantly increased conduction velocity heterogeneity compared to central pacing (1.625 ± 0.190 vs 1.108 ± 0.094, p<0.05), indicating greater incidence of epicardial breakthrough and inaccurate conduction velocity measurement (figure 1). Action potential duration and time-to-peak were unaffected by pacing location (figure 2). Conclusion Our findings suggest central pacing offers optimal conduction and repolarisation dynamics with the lowest incidence of epicardial breakthrough and inaccurate velocity measurements. Conflict of Interest None