Heterogeneous Expression of Potassium Currents and Pacemaker Currents Potentially Regulates Arrhythmogenesis of Pulmonary Vein Cardiomyocytes

Introduction: The relationship between the determining factors and beating rates of pulmonary vein (PV) pacemaker cardiomyocytes has not been fully elucidated. The purposes of this study were to compare the electrophysiological characteristics between PV fast and slow pacemaker cardiomyocytes. Methods: Whole-cell patch clamp was used to investigate the action potentials, transient outward currents (I-to), sustained outward potassium currents (I-Ksus), rapid delayed rectifier potassium currents (I-Kr), inward rectifier potassium current (I-K1), pacemaker currents (I-f), and transient inward currents in isolated rabbit PV single fast (>= 2.5 Hz) and slow (< 2.5 Hz) pacemaker cardiomyocytes. Results: The fast PV pacemaker cardiomyocytes (n = 66) had lesser negative maximum diastolic potential (-53 +/- 1 mV vs -59 +/- 1 mV, P < 0.001) and larger slope of diastolic depolarization (0.31 +/- 0.02 V/sec vs 0.09 +/- 0.01 V/sec, P < 0.001) than slow PV pacemaker cardiomyocytes (n = 65). Moreover, the PV beating rates correlated well with the slope of diastolic depolarization and maximum diastolic potential with a linear regression. As compared to those in slow PV pacemaker cardiomyocytes, the fast PV pacemaker cardiomyocytes had smaller I-to and I-K1, and larger I-f but with similar I-Ksus,I- I-Kr, and transient inward currents. However, only few fast (2/34) and slow (1/23) PV pacemaker cardiomyocytes contained barium-sensitive hyperpolarization-activated time-dependent current (I-KH)(.) Conclusions and Implications: The fast and slow PV pacemaker had different electrophysiological characteristics. I-to, I-K1, and I-f may regulate the beating rates of PV pacemaker cardiomyocytes. (J Cardiovasc Electrophysiol, Vol. 20, pp. 1039-1045).