RESUMO
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.
RESUMO
BACKGROUND: Active fixation leads have provided stable atrial and ventricular pacing; however, long-term follow-up data have not been satisfactory. The purpose of this study was to investigate the long-term reliability of active fixation leads and their electrical characteristic stability. METHODS: A total of 1196 pacing leads were implanted in 830 patients consecutively between 2002 and 2013. In this retrospective study, we were able to trace 1092 leads in 750 patients to investigate the prognosis of implanted leads. The measurement values (including pacing thresholds, sensing amplitudes, and lead impedances of both the atrial and ventricular leads) were obtained from medical records at the time of implantation and during follow up at the outpatient device clinic. All pacing leads were FINELINE II Sterox EZ Leads (Boston Scientific, MN, USA), which are sweet-tip type screw-in active fixation leads, except for the shock leads in patients with implantable cardioverter defibrillator. RESULTS: The mean follow-up period was 51.3±29.2 months (median, 48 months). A total of 1092 leads were implanted in either the atrium (682 leads) or the ventricle (410 leads). Venous access was achieved through cephalic vein cut down (CVC) method (914 leads) or the subclavian vein puncture (SVP) method (178 leads). The overall lead survival rate was 99.6% at both 5 and 10 years. Lead fracture was observed in 4 of 1092 leads (0.37%), all of which were implanted by the SVP method. No lead fracture occurred among patients wherein CVC method was applied (p<0.01). Device-related infection was observed in four patients (0.53%). CONCLUSIONS: The overall reliability and stability of sweet-tip type screw-in leads were satisfactory throughout the long-term follow-up period (median, 4 years). Because it was associated with less lead fractures, cut-down access from the cephalic vein may be recommended as the first-line approach when considering the importance of long-term durability of pacing leads.
