Pulmonary veins (PVs) are thought to play an important role in the initiation of atrial fibrillation. However, systematic microelectrode studies from different regions of the left atria and PV myocardium remain limited.
Methods and results: A 2-microelectrode technique was used to characterize electrophysiological properties of rat left atrial and PV myocardium, at baseline and during electrical stimulation. PV myocardium was characterized by prolonged action potential duration (APD) (74+/-2 ms in the PV mouth vs. 59+/-3 ms in the left atriul, p<0.01), high degree of APD alternans, and spontaneous depolarizations of resting membrane potential recorded without electrical stimulation. In the distal part of the PV, we found an unexcitable area which was characterized by a depolarized resting potential (50+/-4 mV vs. 82+/-2 mV in the left atrium, p<0.01) and conduction blocks.
Conclusion: PV myocardium demonstrates a high degree of action potential duration heterogeneity and conduction discontinuities which may form a functional substrate for reentrant arrhythmias and provoke atrial fibrillation.
Keywords: acetylcholine; action potential; norepinephrine; pulmonary vein.