189: Clinical and electrophysiological data of patients with first degree AV block and AV node reentrant tachycardia

Abstract

Typical atrioventricular (AV) node re-entrant tachycardia (AVNRT) occurs in patients with dual AV nodal pathway, a rapid pathway used for retrograde conduction and a slow pathway used for the anterograde conduction. In sinus rhythm, the patients have generally the signs of conduction through the rapid pathway with a normal or short PR interval. The purpose of the study was to evaluate the prevalence of patients with 1 st degree AV block and with AVNRT and their clinical characteristics. 973 patients, 348 males, 625 females, were admitted for typical AVNRT. They were aged from 6 to 90 years (mean age 50±19). Initial ECG and clinical data were collected. Electrophysiological study was systematic. Spontaneous 1 st degree AV block (AVB) was rare and noted in 7 patients. The prevalence of the association 1 st degree AV block and AVNRT was 0.7%. Five patients complained of AVNRT at exercise. Two patients had an ischemic heart disease. Patients with AVB were significantly older (71.5± 16 years) than patients without AVB (50±19)(p<0.002). AVNRT was induced in control state in 4 patients. The rate of tachycardia was slow between 130 and 150 bpm. AVNRT was induced after isoproterenol in 3 patients and the rate was higher (180 to 200 bpm). Ablation of slow pathway was performed in 6 patients. Transitory 2 nd degree AVB was noted in 1 patient. AVNRT was not inducible after ablation. PR interval remained unchanged. At atrial pacing, the rate of 2 nd degree AVB occurrence decreased, due to the disappearance of the conduction through the slow pathway. Two patients developed transitory well-tolerated 2 nd degree AVB one day after ablation. One patient presented apparent sinus bradycardia related to a concealed conduction through AV node. One year after ablation none of the patients required pacemaker implantation and patients were free of tachycardia. The occurrence of AVNRT in patients with 1 st degree AV block is exceptional and concerns old patients. Ablation of slow pathway might be safely performed without a need of pacemaker implantation. Transitory 2 nd degree AVB can be noted the day after ablation.