Management of Mobitz Type II Second-Degree Atrioventricular Block
Patients with Mobitz Type II second-degree atrioventricular block require immediate placement of transcutaneous pacing pads and evaluation for permanent pacemaker implantation due to high risk of progression to complete heart block and hemodynamic compromise. 1
Initial Management Steps
- Place transcutaneous pacing pads immediately as Mobitz Type II has high risk of progression to complete heart block 1
- Perform transthoracic echocardiography (Class I recommendation) to assess for underlying structural heart disease 1
- Obtain laboratory tests including electrolyte panel to rule out reversible causes 1
- Arrange for permanent pacemaker implantation, especially if the patient is symptomatic 2, 3
Diagnostic Criteria and Recognition
- Mobitz Type II is characterized by P waves with a constant rate (<100 bpm) with periodic single nonconducted P waves and constant PR intervals before and after the blocked P wave 2, 4
- Must be distinguished from Mobitz Type I (Wenckebach), which has progressive PR prolongation before the blocked beat 5
- Typically occurs below the AV node in the His-Purkinje system, unlike Mobitz Type I which occurs in the AV node 5, 4
Indications for Permanent Pacemaker
- Pacemaker implantation is recommended as a Class I indication for any patient with Mobitz II second-degree AV block 2
- Prophylactic pacemaker implantation is indicated in all patients with Mobitz Type II block, even if asymptomatic, due to high risk of progression to complete heart block 3
- Pacemaker implantation is also recommended for postoperative Mobitz II that persists beyond 7-10 days 2
Special Considerations
- Patients with bifascicular block (such as RBBB with left anterior hemiblock) who develop Mobitz Type II are at particularly high risk for complete heart block 6
- ECG often shows intraventricular conduction abnormalities such as LBBB, RBBB with left axis deviation, or other bundle branch blocks 3
- Exercise testing may reveal exercise-induced worsening of AV block in some patients 2, 6
- In rare cases where a reversible cause is identified (e.g., medication effect, pembrolizumab-induced cardiotoxicity), temporary pacing may be needed until the cause is addressed 7
Monitoring and Follow-up
- Continuous cardiac monitoring is essential until permanent pacemaker is placed 1
- After pacemaker implantation, regular device checks are needed to ensure proper function 2
- Patients with dual-chamber pacemakers should have programming aimed at maintaining native AV conduction when possible to prevent pacing-induced ventricular dysfunction 2