A percutaneous method for single catheter recording of multiple Monophasic action potentials from the epicardial surface in intact anesthetized rodents

A surgical method for programmed electrical stimulation (PES) in mice has been reported by Gutstein et al (2003). We developed a percutaneous approach to record multiple epicardial monophasic action potentials (multi-MAP) in rodents, with a single amagnetic catheter (AC). Methods: Under 6 ECG leads monitoring the AC was introduced with a sub-xyphoid puncture, in 5 anesthetized, spontaneously breathing, Wistar rats (WR) and 5 guinea pigs (GP). The AC was moved at several epicardial sites. 4 MAPs were simultaneously recorded at each site with a fixed (1 mm) inter-electrode distance. MAP signals, differentially amplified and filtered at DC-500 Hz were digitized at 1kHz. The same AC was used for PES at pacing cycles between 200 and 250 ms. Ventricular effective refractory period (VERP) was evaluated with the accuracy of 2 ms. MAP duration (MAPd), at 50% and 90% levels of repolarization, and local activation time among the four MAPs were calculated. Results: All but one animal tolerated the procedure and survived. One rat died for respiratory arrest at the moment of the puncture. One rat was restudied after 6 months and survived also the second procedure. MAPd 90% (ms) were: 69\ub15.6 (WR) and 172\ub112.3 (GP). VERP were: 67\ub19.4 (WR) and 155\ub115.6 (GP). Conclusion: The percutaneous approach avoids cut-down, is well tolerated and keeps animals alive and available for longitudinal investigations. The multi-MAP method provides information about arrhythmogenic mechanisms (i.e. MAPd/ERP ratio, detection of ventricular repolarization (VR) inhomogeneity and of local block), with high spatial resolution. This animal model can be used for correlative studies between dispersion of MAP duration and surface estimate of QT dispersion and T wave abnormalities