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Effect of intravenous and oral acebutolol in patients with bundle branch block

P A Crean, D O Williams

    International Journal of Cardiology
    |February 1, 1986
    PubMed

    Insights

    Acebutolol, a beta-blocker, was studied for its effects on atrioventricular conduction in patients with bundle branch block. The drug prolonged conduction times and, in some patients with prior heart block, induced temporary atrioventricular block.

    Area of Science:

    • Cardiology
    • Electrophysiology
    • Pharmacology

    Background:

    • Idiopathic bundle branch block (BBB) can affect cardiac conduction.
    • Patients with BBB may have varying degrees of atrioventricular (AV) conduction abnormalities.
    • The impact of beta-blockers on AV conduction in BBB patients requires further investigation.

    Purpose of the Study:

    • To evaluate the effects of intravenous and oral acebutolol on atrioventricular conduction in patients with idiopathic bundle branch block.
    • To compare the effects in patients with and without a history of symptomatic complete heart block.
    • To assess the incidence of induced atrioventricular block following acebutolol administration.

    Main Methods:

    • Twenty-two patients with idiopathic BBB and 1:1 AV conduction were enrolled.
    • Seven patients had a history of symptomatic complete heart block (Group 1), 15 were asymptomatic (Group 2).
    • Intravenous (1 mg/kg) and oral (400 mg) acebutolol were administered, with electrophysiological parameters monitored.

    Main Results:

    • Intravenous acebutolol decreased heart rate and prolonged A-H and H-V intervals in both groups.
    • No significant difference in basal or induced conduction changes was observed between the two groups.
    • Temporary atrioventricular block distal to His was induced by intravenous acebutolol in 2/6 patients with prior heart block and by oral acebutolol in 4/7 patients with prior heart block.

    Conclusions:

    • Acebutolol significantly affects atrioventricular conduction in patients with bundle branch block.
    • Patients with a history of symptomatic heart block may be more susceptible to acebutolol-induced atrioventricular block.
    • Careful electrophysiological assessment is warranted when prescribing acebutolol to patients with bundle branch block, especially those with prior heart block history.

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