CHANGES OF CONDUCTIVITY IN PATIENTS WITH 2ND-DEGREE OR 3RD-DEGREE ATRIOVENTRICULAR-BLOCK AFTER PACEMAKER IMPLANTATION

The purpose of this study was to examine the long-term course of condu ctivity in patients with second- or third-degree atrioventricular (AV) block after pacemaker implantation. Fifty-four patients (30 males and 24 females, mean age 59.5 years) had a 12-lead electrocardiogram (EGG ) recorded prior to pacemaker implantation and again after a follow-up of more than 5 years (mean 108 months). The degree of AV block and th e morphology of the QRS complex in the two ECGs were compared. Twenty- eight (85%) of the 33 patients with complete AV block and 15 (71%) of the 21 patients with second-degree AV block before implantation showed complete AV block after the follow-up period. The progression of AV b lock was recognized only in patients with intra-His (BH) or infra-His (H-V) block. In 29 patients, escape QRS complexes were recorded in bot h ECGs. A change in the QRS complex was noted in 6 patients (21%), inc luding 2 with new bundle branch block (BBB), 2 with wider BBB, 1 with new left axis deviation, and 1 with a change to another BBB. This chan ge was particularly notable in the H-V block group (44%). In conclusio n: (1) Most patients with complete AV block did not recover AV conduct ivity after the long-term follow-up. (2) Second-degree BH and H-V bloc k tended to progress to complete AV block.