A new single catheter technique for simultaneous measurement of action potential duration and refractory period in vivo

In vivo correlations of action potential duration measured by a monophasic action potential catheter and effective refractory period measured by a separate pacing catheter have been poor, probably because of the known variability of both action potential duration and effective refractory period between different ventricular sites. In this study, a new quadripolar contact electrode catheter designed for simultaneous pacing and monophasic action potential recording at closely adjacent sites (2 mm separation between recording electrodes and pacing electrodes) was tested in five closed chest dogs and four patients. Dog studies:Pacing thresholds were extremely low, ranging from 0.02 to 0.25 mA (mean ± SD 0.099 ± 0.051, n = 36) and were stable over time (<20% increase during 1 h of continuous pacing). Because of the close proximity of pacing and recording electrodes, the pacing artifact nearly coincided with the monophasic action potential upstroke. Because of the low pacing threshold, however, pacing artifacts were small (33 ± 17% of the monophasic action potential amplitude at twice diastolic threshold strength) and did not affect the duration or configuration of the simultaneously recorded monophasic action potential. The short stimulus response time and the undisturbed monophasic action potential signal fidelity during pacing allowed precise simultaneous measurements of action potential duration and effective refractory period at the same endocardial site. Linear regression analysis of 34 paired recordings made at various right ventricular locations and cycle lengths demonstrated a close correlation between action potential duration (measured at 90% repolarization) and effective refractory period (r = 0.87, p = 0.0001) and even better correlation for cycle length-dependent changes in action potential duration and effective refractory period (r = 0.92, p = 0.0001). At a single ventricular site, both action potential duration and effective refractory period showed a linear and parallel decrease with paced steady state cycle length, thus maintaining a near constant ratio between effective refractory period and action potential duration over a wide range of cycle lengths. Human studies:Use of this new pacing-monophasic action potential recording catheter in patients produced essentially similar results. In addition, the technique was found to be useful during programmed electrical stimulation, allowing on-line evaluation of the relation between changes in act