title: Direct endocardial recording from an accessory atrioventricular pathway: localization of the site of block, effect of antiarrhythmic drugs, and attempt at nonsurgical ablation.
abstract: We recorded a discrete 0.95 mV potential consistent with accessory atrioventricular pathway (AP) activation during serial electrophysiologic studies in a patient with Ebstein's anomaly and Wolff-Parkinson-White syndrome. Bipolar pacing from the catheter electrode in which the AP potential was recorded resulted in a stimulus-ventricle interval identical to the AP-ventricle interval during antegrade conduction, and a stimulus-atrium interval identical to the AP-atrium interval during retrograde conduction. With the patient in the drug-free state, antegrade AP block during atrial pacing and retrograde AP block during ventricular pacing occurred distal to the AP potential (AP-ventricle junction and AP-atrium junction, respectively), supporting the "impedance mismatch" hypothesis. Procainamide and disopyramide each lengthened the antegrade AP effective refractory period by affecting the AP-ventricle junction (possibly by decreasing the current generated by the AP). Both drugs also lengthened the retrograde AP effective refractory period but produced a greater effect on the ventricle-AP junction than on the AP-atrium junction, suggesting marginal geometry of the former. R wave synchronous shocks of 160 and 320 W-sec delivered between the catheter electrode recording the largest unipolar AP potential and a skin electrode produced transient, complete, antegrade block over the AP, suggesting the feasibility of this new nonsurgical technique for AP ablation.
mesh_terms: D000328:Adult; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D001283:Atrioventricular Node / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D004206:Disopyramide / Q000627:therapeutic use; D004437:Ebstein Anomaly / Q000503:physiopathology; D004599:Electric Stimulation Therapy; D004562:Electrocardiography; D004594:Electrophysiology; D004699:Endocardium; D005260:Female; D006327:Heart Block / Q000503:physiopathology* / Q000628:therapy; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D011342:Procainamide / Q000627:therapeutic use; D011433:Propranolol / Q000627:therapeutic use; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology
chemical_list: D000889:Anti-Arrhythmia Agents; D011433:Propranolol; D004206:Disopyramide; D011342:Procainamide