Procainamide and retrograde atrioventricular nodal conduction in man.

Abstract

SUMMARY Recent studies that show a depressant effect of procainamide (PA) on retrograde conduction in patients with atrioventricular (AV) nodal reentrant tachycardia (RT) have suggested possible incorporation of AV nodal bypass tracts. Electrophysiologic effects of i.v. PA, 10 mg/kg, on retrograde AV nodal conduction were examined in 13 patients without RT, demonstrable AV nodal refractory period curves, or accessory pathways. Ventriculoatrial (VA) conduction was recorded before and after PA using intracardiac electrograms, incremental ventricular pacing and extrastimulation. With incremental pacing during the control, VA block occurred at a mean cycle length (CL) of 364.6 ± 87.9 msec. After PA, VA conduction was abolished in five of 13 patients due to onset ages 53-82 years (mean + SD 66.2 ± 9.9 years), were studied because of recurrent ventricular arrhythmias, dizziness or syncope. Eight patients had arteriosclerotic heart disease and five had no clinically detectable heart disease. Ten had normal intraventricular conduction and three had right bundle branch block. Four patients had ventricular premature complexes and one patient had an old inferior myocardial infarction.Patients gave informed, signed consent for the study.Right-heart catheterization was performed in a nonsedated, postabsorptive state. With the patients under local anesthesia, quadripolar electrode catheters were percutaneously introduced through the femoral and antecubital veins and positioned under fluoroscopic guidance across the tricuspid valve near the AV junction to permit recording of the His bundle potential. The catheters were also advanced to the high right atrium and the right ventricle to permit recordings and electrical stimulation as previously described.3The intracardiac electrograms (filtered at 30-500Hz) and three sufrace lead ECGs (usually leads I, II, and V,) and a time line were simultaneously displayed on a multichannel oscilloscope (Electronics for Medicine VR-12) and recorded on a magnetic tape (Honeywell model 96). Recordings were reproduced on photographic paper at 100 or 150 mm/sec. Electrical stimulation was performed using a digital stimulator (DTU; Bloom Associated, Ltd.). During these studies, patients were isolated and all equipment was grounded at equipotential. The following protocol for electrical stimulation was performed:(1) incremental atrial pacing to achieve the antegrade AV nodal Wenckebach cycle; (2) antegrade refractory periods using atrial basic drive of eight beats (A1A,), followed by premature atrial stimulation (A2); (3) incremental ventricular pacing to achieve ventriculoatrial (VA) block; and (4)

Atrioventricular nodal reentry. Clinical, electrophysiological, and therapeutic considerations.

“…Class 1 agents such as procainamide can terminate the same arrhythmia by blocking the conduction in the retrograde direction. 31,57,58 Chronic Management Pharmacological therapy. Figure 12 depicts the likely site of drug action of various therapeutic agents in the common form of AV nodal reentrant tachycardia.…”