A proposal of clinical ECG index “vagal score” for determining the mechanism of paroxysmal atrioventricular block

Background Paroxysmal atrioventricular block (P‐AVB) is a well‐known cause of syncope; however, its underlying mechanism is difficult to determine. This study aimed to evaluate a new ECG index, the “vagal score (VS),” to determine the mechanism of P‐AVB. Methods We evaluated the VS in 20 patients with P‐AVB (13 men, 7 women; aged 25–78 years [mean, 59.3 years]). The VS was developed by assigning 1 point each for the following: (1) no AVB or intraventricular conduction disturbance on the baseline ECG, (2) PR prolongation immediately before P‐AVB, (3) sinus slowing immediately before P‐AVB, (4) initiation of P‐AVB by PP prolongation, (5) sinus slowing during ventricular asystole, and (6) resumption of AV conduction with PP shortening, and by assigning −1 point each for (7) the initiation of P‐AVB by a premature beat, and (8) resumption of AV conduction by an escape beat. Based on the clinical situations and electrophysiologic findings, we considered the mechanism of P‐AVB as vagally mediated or intrinsic conduction disease (ICD). Results The VS ranged from 5 to −2 points for each patient. Five patients with a definite vagally mediated P‐AVB had high VSs (3–5 points). We observed characteristic ECG findings of ICD consisting of changes in AV conduction by an extrasystole and/or escape beat in only 5 of the 6 patients (83%) with a low VS (1 to −2). Conclusions The VS is simple and potentially useful for determining the mechanism of P‐AVB. P‐AVB with a VS ≥3 strongly suggested a vagally mediated mechanism.