Electrophysiologic effects of intravenous nicardipine on sinus node function and conduction in humans.

We conducted an intracardiac study of the electrophysiologic effects and kinetics of intravenous nicardipine (N) in 16 patients with or without impaired cardiac conduction, using a randomized, double-blind, crossover design versus placebo (P). N or P were infused intravenously over 5 min: the dose of N was 9.46 +/- 3.85 mg. Standard electrophysiologic parameters of atrioventricular (AV) conduction and sinus function were measured under basal conditions, between 10 and 25 min, and at 65 min, after beginning the first infusion of N or P, and between 10 and 25 min after beginning the second infusion of N or P. Treatment with N significantly reduced systolic (S) and diastolic (D) blood pressure (BP) at 10 min (35 +/- 19 and 25 +/- 17 mm Hg, respectively). N significantly shortened sinus cycle length (SCL), corrected sinus recovery time (CSNRT), AH interval, AV node (AVN) Wenckebach cycle length, and anterograde and retrograde effective (ERPs) and functional refractory periods (FRPs) of the AVN. Infranodal parameters were unaffected. Mean plasma N concentrations at 10 min were 18.5 +/- 7.7 ng/ml/kg and 5.3 +/- 3 ng/ml/kg at 60 min. Two patients experienced slight adverse effects (anginal pain and nausea); another with sick sinus syndrome developed a sinus pause. We conclude that intravenous N affects nodal, but not His conduction, and that it should be administered with care in the presence of SSS.