Electrophysiologic effects of lidocaine on sinus node and atrium in patients with and without sinoatrial dysfunction

Electrophysiological studies were conducted in 13 patients with normal sinus node function and 14 with sinus node dysfunction before and after intravenous lidocaine. Mean ± SEM sinus cycle length significantly shortened from 810 ± 34.3 to 774 ± 34.3 msec in patients with normal sinus node (P < 0.001) and from 1061 ± 67.6 to 1016 ± 64.5 msec in patients with sinus node dysfunction (P < 0.025) after lidocaine. Mean sinus recovery time was 1027 ± 49.4 before and 1026 ± 52.5 msec after lidocaine in patients with normal sinus node (NS) and 1269 ± 97.7 before and 1170 ± 73.8 msec after lidocaine in patients with sinus node dysfunction (P < 0.05). Mean calculated sinoatrial conduction time was 87 ± 9.5 before and 90 ± 9.2 msec after lidocaine in patients with normal sinus node (NS) and 80 ± 10.3 before and 96 ± 10.2 msec after lidocaine in patients with sinus node dysfunction (P < 0.001). Mean atrial effective and functional refractory periods were not significantly changed with lidocaine. Thus lidocaine shortened sinus cycle length in both groups, without affecting atrial refractoriness. Lidocaine appeared to depress perinodal tissue only in patients with sinus node dysfunction. The abbreviation of sinus recovery time in patients with sinus node dysfunction could reflect increased sinus automaticity and/or increased perinodal refractoriness, allowing entrance block to occur. This mechanism may explain why sinus arrest has been noted in some patients during lidocaine administration.