The recording of monophasic action potentials with fractal-coated iridium electrodes in humans.

The present study was designed to evaluate the feasibility of the recording of monophasic action potentials (MAP) with fractal-coated iridium electrodes in a clinical setting. In 18 patients who underwent an electrophysiological study for various arrhythmias, we performed MAP recordings with both 1.3-mm2 and 6-mm2 tip surface area fractal-coated iridium and standard silver--silver chloride (Ag/AgCl) electrodes in the high right atrium and two ventricular positions. Amplitude and MAP duration at 90%, 50%, and 25% of repolarization were calculated during steady-state pacing at 600, 500, and 400 ms cycle lengths with extrastimuli application. Morphology comparisons of MAP signals recorded with both types of electrodes were performed by regression analysis using 5% of the repolarization segments of the MAP trajectory. Differences between MAP duration at 90%, 50%, and 25% of repolarization recorded with fractal-coated and Ag/AgCl electrodes were statistically insignificant. Amplitude values recorded with 6-mm2 tip electrodes were significantly smaller than those recorded with Ag/AgCl electrodes for all comparisons. During steady-state pacing, the correlation coefficients between Ag/AgCl and fractal-coated 1.3-mm2 and 6-mm2 tip electrodes were within the range of 0.93-0.999 and 0.87-0.999, respectively. The correlation of MAP amplitude and duration at 90%, 50%, and 25% of repolarization following the extrastimulus S2, recorded with both types of electrodes, was significantly weaker for right atrial recordings (r value range 0.78-0.92) as compared to ventricular recordings (r value range 0.92-0.99). The MAP sensing features of fractal-coated iridium and Ag/AgCl electrodes are comparable. The best results for recording of MAPs with fractal-coated electrodes can be achieved with small surface area tip electrodes.