engleski

Clinical significance and natural history of exercise-induced atrioventricular block

Exercise-induced atrioventricular (AV) block is rarly observed and, thereofer, its significance and natural history are not well known. We studied 11 patients (pts) with sinus rhythm and without previously documented AV block who develope Mobitz type II or 2:1 AV block during graded exercise testing. There were 8 mles and 3 females aged 42 to 75 years (mean 60). All pts had presyncopes. Nine pts had a bundlebranch block and 2 pts had normal QRS configuration. During exercise testing AV block appeared at sinus rates of 100-140 beats/min (mean 120+-14). AV conduction returned to normal after exercise whena sinus rate decreased from 110-64 beats/min (mean 80). In 6 pts, an eletrophysiologic study was performed and infranodal site of AV block was found. Zhe mechanism of AV blokc may be expalined by abnormal refractoriness of the His bundle (1 pt) or His-Purkinje system (5 pts), which fails to decrease sufficiently for allowing 1:1 conduction. During a follow-up pewriod of 12 to 68 moths (mean30+-18), 3 pots devedloped spontaneous AV block and 7 pts complete AV block. Only 1 pt remiand in sinus rhythm. The period of spontaneous AV block occurrence ranged from 1 to 24 months (mean 12). two pts died due to cancer and 1 pt died due to cardiac failure. We conclude that the appearance of AV block during exercise reflects conduction disease of His bundle orHis-Purkinje system. because pts with this conduction disease had high risk of progression to adavnced or complete AV block, preventive cardiac pacing is indicated.

Exercise testing; AV block

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