Long-term follow-up in patients with intra-Hisian atrioventricular block

Long-term follow-up was performed in patients with intra-Hisian atrioventricular (AV) block who were implanted with permanent pacemakers. Subjects were 14 consecutive patients (3 men and 11 women, 65.4±9.7 [SD] years old), who exhibited intra-Hisian block at the time of pacemaker generators were replaced due to battery depletion. Electrophysiological examinations were performed at both the initial implantation and pacemaker replacement. The mean duration from the initial implantation to the replacement was 9.4±4.3 years. All patients had severe symptoms such as syncope, dizziness, or dyspnea, and these symptoms were relieved by pacemaker implantation. Seven patients had complete AV block, and the other seven had advanced or paroxysmal AV block at the time of implantation. Seven patients, who had advanced AV block at the time of implantation, developed complete AV block. Five of the seven patients who had complete AV block at the time of implantation remained in complete AV block, one patient had advanced AV block, and one patient of complete AV block increased significantly from 50% to 93% during the two electrophysiological examinations (P<0.05). A mean heart rate of 40.3±7.5 beats/min was observed during complete AV block. At the time of implantation, two patients were misdiagnosed as having AH block, and the other two patients were misdiagnosed as having HV block. In conclusion, intra-Hisian AV block gradually developed from advanced or paroxysmal AV block into complete AV block. Because the diagnosis of intra-Hisian block is sometimes difficult, we should always consider the possibility of intra-Hisian block in patients with severely symptomatic AV block.