Management and treatment of AV blocks (first, second and third-degree AV block)
Evaluation of patients with suspected AV blocks requires a thorough medical history (with emphasis on causes of AV blocks, refer to the Causes of AV blocks) and physical examination. It is also reasonable to analyse cardiac troponins if there is any probability of acute ischemic heart disease as the underlying cause of the AV block. Holter ECG may be valuable if the diagnosis is uncertain. Otherwise, no further examination is needed beyond the 12-lead ECG. Echocardiography is generally not necessary. Management of AV blocks aims to restore atrioventricular conduction either pharmacologically or by means of artificial pacemakers. Both methods may be used in the acute setting, whereas long-term management only includes pacemaker therapy.
Treatment of AV block in the acute setting
Treatment in the acute setting is directed at managing bradycardia and reduced cardiac output. Start with atropine 0.5 mg iv (may be repeated). Atropine will have effect if the block is located in the AV node. Note that atropine may aggravate the block if it is located distal to the AV node. Isoprenaline (isoproterenol, 5 micrograms per minute) may also be administered (with caution in case of acute coronary syndromes, as isoprenaline may trigger ventricular tachycardia). If sinus bradycardia or asystole persists despite attempts with atropine and isoprenaline, transcutaneous or transvenous pacemaker should be implemented. Transcutaneous pacemaker is a painful method which mandates sedation but should not be withdrawn if the situation is life-threatening. Any medications causing or aggravating the block must be withdrawn.
AV blocks due to reversible causes does not need permanent pacemaker. High-degree AV block without reversible cause mandates pacemaker in the majority of cases.
Long-term treatment of AV block: permanent artificial pacemaker
- First-degree AV block and second-degree AV block Mobitz type I: Only necessitates pacemaker if symptomatic. The indication is stronger if the QRS complexes are wide.
- Second-degree AV block Mobitz type II and third-degree AV block: These patients should almost invariably receive a pacemaker. In case of Mobitz type 2 with wide QRS complexes, pacemaker is indicated even in the absence of symptoms. All cases of third-degree AV block necessitates pacemaker.