What is the primary treatment for a patient with Mobitz type II (second-degree) atrioventricular (AV) block?

Primary Treatment for Mobitz Type II AV Block

Permanent pacemaker implantation is the primary treatment for patients with Mobitz type II second-degree atrioventricular block, regardless of whether symptoms are present. 1

Understanding Mobitz Type II AV Block

Mobitz type II AV block is characterized by:

• Intermittent non-conducted P waves without progressive PR interval prolongation
• Usually occurs at the level of the His-Purkinje system (infranodal)
• Often associated with a wide QRS complex
• High risk of progression to complete heart block
• Potential for sudden cardiac death due to asystole

Evaluation Before Pacemaker Implantation

Before proceeding with pacemaker implantation, a thorough evaluation should include:

• Assessment for symptoms (syncope, presyncope, dizziness, fatigue, exercise intolerance)
• ECG to confirm diagnosis and assess QRS width
• Echocardiogram to evaluate cardiac structure and function
• Exclusion of reversible causes (medication effects, electrolyte abnormalities)

Treatment Algorithm

1. Acute/Temporary Management:

   • For symptomatic bradycardia: Transcutaneous pacing may be used as an urgent expedient 1
   • IV atropine may be considered for temporary management of bradycardia but is not definitive treatment 2
   • Temporary transvenous pacing for hemodynamically unstable patients

2. Definitive Treatment:

   • Permanent pacemaker implantation is indicated for all patients with Mobitz type II AV block 1
   • This recommendation applies to both symptomatic and asymptomatic patients 1

Evidence Supporting Permanent Pacing

The recommendation for permanent pacing in Mobitz type II AV block is based on:

• High risk of progression to complete heart block 1, 3
• Significant risk of Adams-Stokes syndrome and sudden death 3
• Location of block in the His-Purkinje system rather than AV node 3
• Poor prognosis without intervention 1

Special Considerations

• Asymptomatic patients: Permanent pacing is still recommended as a Class IIa indication due to risk of progression to complete heart block 1
• Post-myocardial infarction: Persistent Mobitz type II AV block after MI is a Class I indication for permanent pacing 1
• Athletes: Mobitz type II AV block is considered abnormal in athletes and requires permanent pacemaker implantation before resuming competitive sports 1
• Congenital heart disease: Pacemaker implantation is recommended for any patient with postoperative Mobitz II second-degree AV block that is not expected to resolve 1

Common Pitfalls

1. Misdiagnosis: Ensure accurate differentiation between Mobitz type I (Wenckebach) and Mobitz type II AV block. In cases of 2:1 AV block, it may be difficult to distinguish between the two types without electrophysiological study 1

2. Delayed treatment: Do not wait for symptoms to develop before considering pacemaker implantation in patients with confirmed Mobitz type II AV block 3

3. Inadequate follow-up: Even after pacemaker implantation, patients require regular follow-up to ensure proper device function and to monitor for progression of underlying conduction disease

4. Overlooking reversible causes: While permanent pacing is typically required, always consider potentially reversible causes such as medication effects, electrolyte abnormalities, or inflammatory conditions 4, 5