[Block of the atrioventricular trunk: diagnosis of the site by Holter monitoring].

Twelve patients with intrahisian AV block, confirmed later by electrophysiological investigations had Holter recordings showing the block (paroxysmal in 11 cases, permanent in 1 case). The diagnosis of the site of the block was made before endocavitary investigation in all cases on the following criteria: narrow QRS complexes in 10 out of 11 paroxysmal blocks (1 with phase III LBBB) with a sudden transition from 1/1 to 2/1 conduction. Only 3 patients had rare sequences of lower degree, Mobitz II block. Only 3 patients had 2 or more consecutive blocked P waves. The role of sinus tachycardia (block in phase III) was demonstrated in 10 out of 11 cases. The block was found on the first 24 hour Holter recording in all but 1 patient. This contrasts with paroxysmal trifascicular block: out of 46 patients recruited during the same period, only 4 had Holter recordings showing the block and this was not reproducible. The 12th patient had permanent AV block with wide QRS complexes and narrow sinus captures in the supernormal period in the morning. The sudden transition from 1/1 to 2/1 conduction in phase III is characteristic of intrahisian block and distinguishes it from intranodal AV block. All patients were improved by VDD mode pacing.