From the Guidelines
For sinus rhythm second-degree atrioventricular (AV) block, the treatment recommendation is to consider permanent pacemaker implantation, especially for symptomatic patients or those with Mobitz type II block, as it is usually infranodal and associated with a higher risk of progression to complete heart block. The approach to treatment depends on the type of block and the presence of symptoms.
Key Considerations
- For asymptomatic Mobitz type I (Wenckebach) block, observation without specific treatment may be sufficient, as this type is usually benign and may be transient 1.
- For symptomatic Mobitz type I or any Mobitz type II block, permanent pacemaker implantation is the definitive treatment, considering the higher risk of progression to complete heart block and the potential for significant symptoms 1.
Temporary Measures
- Atropine (0.5-1 mg IV, repeated every 3-5 minutes if needed, maximum 3 mg) can be used to increase heart rate in symptomatic patients.
- Isoproterenol infusion (2-10 mcg/min titrated to heart rate) may be considered in emergency situations while awaiting pacemaker placement.
Addressing Underlying Causes
- Discontinuation of AV nodal blocking medications (beta-blockers, calcium channel blockers, digoxin) is crucial.
- Correction of electrolyte abnormalities and treatment of myocardial ischemia are important.
- Management of infectious causes like Lyme disease should be addressed. The decision for permanent pacing should consider whether the AV block is likely to be permanent, and reversible causes should be corrected first 1.
From the Research
Treatment Recommendations for Sinus Rhythm Second-Degree AV Block
The treatment recommendations for sinus rhythm second-degree atrioventricular (AV) block depend on the type of block and the presence of symptoms.
- For Mobitz type II second-degree AV block, pacing is generally recommended, regardless of QRS duration or symptoms, as it is almost always infranodal and can progress to complete heart block 2, 3, 4.
- Infranodal block presenting with either type I or II manifestations requires pacing, regardless of QRS duration or symptoms 2.
- The distinction between type I and type II block is descriptive, but the anatomic site of the block and the prognosis are more important to the clinician 3.
- Correctly identified Mobitz type II AV block is invariably at the level of the His-Purkinje system and is an indication for a pacemaker 4.
Important Considerations
- A stable sinus rate is required for the diagnosis of type II block, and absence of sinus slowing is an important criterion 2, 4.
- A vagal surge can cause simultaneous sinus slowing and AV nodal block, which can superficially resemble type II block 2, 4.
- Concealed His bundle or ventricular extrasystoles may mimic both type I and/or type II block (pseudo AV block) 2, 4.
- A 2:1 AV block cannot be classified in terms of type I or type II block, but it can be nodal or infranodal 2, 4.