Paroxysmal AV block Acute Management

2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: Recommendations for Acute Management of Reversible Causes of Bradycardia Attributable to Atrioventricular Block

Recommendations for Acute Management of Reversible Causes of Bradycardia Attributable to Atrioventricular Block

"1. Patients with transient or reversible causes of atrioventricular block, such as Lyme carditis or drug toxicity, should have medical therapy and supportive care, including temporary transvenous pacing if necessary, before determination of need for permanent pacing. (Level of Evidence: B-NR 2. In selected patients with symptomatic second-degree or third-degree atrioventricular block who are on chronic stable doses of medically necessary antiarrhythmic or etablocker therapy, it is reasonable to proceed to permanent pacing without further observation for drug washout or reversibility. (Level of Evidence: B-NR) 3. In patients with second-degree or thirddegree atrioventricular block associated with cardiac sarcoidosis, permanent pacing, with additional defibrillator capability if needed and meaningful survival of greater than 1 year is expected, without further observation for reversibility is reasonable. (Level of Evidence: B-NR) 4. In patients with symptomatic seconddegree or third-degree atrioventricular block associated with thyroid function abnormalities but without clinical myxedema, permanent pacing without further observation for reversibility may be considered. (Level of Evidence: C-LD)"

2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: Recommendations for Acute Medical Therapy for Bradycardia Attributable to Atrioventricular Block

Recommendations for Acute Medical Therapy for Bradycardia Attributable to Atrioventricular Block

"1. For patients with second-degree or third degree atrioventricular block believed to be at the atrioventricular nodal level associated with symptoms or hemodynamic compromise, atropine is reasonable to improve atrioventricular conduction,increase ventricular rate, and improve symptoms (Level of Evidence: C-LD 2. For patients with second-degree or thirddegree atrioventricular block associated with symptoms or hemodynamic compromise and who have low likelihood for coronary ischemia, beta-adrenergic agonists, such as isoproterenol, dopamine, dobutamine, or epinephrine, may be considered to improve atrioventricular conduction, increase ventricular rate, and improve symptoms.(Level of Evidence: B-NR) 3.For patients with second-degree or thirddegree atrioventricular block associated with symptoms or hemodynamic compromise in the setting of acute inferior MI, intravenous aminophylline may be considered to improve atrioventricular conduction, increase ventricular rate, and improve symptoms. (Level of Evidence: C-LD) "

• The acute treatment of bradycardia attributable to atrioventricular block will often begin with timely identification and removal of potential causative factors as well as medical therapy.

Atropine

• Atropine has a long track record of use for this indication because of ease of administration and relatively low risk of adverse reactions.
• It is more likely to be useful for atrioventricular block at the atrioventricular nodal level and for bradycardia attributable to excess vagal tone.
• Because of its short duration of action, it is generally used as a bridge to longer-lasting therapy, such as infusion of a beta-adrenergic drug or temporary pacing.
• Atropine is a parasympatholytic drug that enhances atrioventricular nodal conduction and automaticity, generally given in 0.5- to 1.0-mg IV increments.
• Current advanced cardiac life support recommendations advise early use of atropine for medical treatment of hemodynamically significant bradycardia, including atrioventricular block.
• Uncontrolled cohort studies suggest efficacy and clinical benefit, particularly in the setting of acute inferior MI.
• Atropine is unlikely to improve atrioventricular block at the His bundle or His-Purkinje level and isolated reports have suggested occasional worsened atrioventricular conduction and/or hemodynamic compromise in such patients.
  • For this reason, atropine should be used judiciously in patients with atrioventricular block and wide QRS complexes that suggest the presence of significant His Purkinje disease.
• Adverse effects of atropine include dry mouth, blurred vision, anhidrosis, urinary retention, and delirium. Excessive increase in heart rate may be problematic, particularly in patients with acute MI.

Beta-adrenergic agonists

• Beta-adrenergic agonists such as isoproterenol, dopamine, dobutamine, and epinephrine exert direct effects to enhance atrioventricular nodal and, to a lesser degree, His-Purkinje conduction.
• These drugs may also enhance automaticity of subsidiary atrioventricular junctional and ventricular pacemakers in the setting of complete atrioventricular block.
• Adverse effects of beta-adrenergic agonists may include elicitation of ventricular arrhythmias and induction of coronary ischemia, particularly in the setting of acute MI or unstable coronary artery disease.
• In addition, isoproterenol may exacerbate hypotension because of the vasodilatory effects.

Amminophylline

• Aminophylline is a methylxanthine compound that is a nonselective adenosine receptor antagonist and phosphodiesterase inhibitor.
• It is used clinically as a bronchodilator and as a reversal drug for dipyridamole, adenosine, and regadenoson in pharmacologic nuclear stress testing.
• Aminophylline and glucagon have a possible role in treatment of atrioventricular block in the setting of acute MI and beta-blocker toxicity, respectively, but data are sparse.

• Experimental evidence suggests a role of increased adenosine production in development of atrioventricular block in acute inferior MI.

Acute Medical Management of AV Block or Sinus node dysfunction