What is the treatment for second-degree heart block?

Treatment of Second-Degree Heart Block

The treatment of second-degree heart block depends on the type (Mobitz I vs. Mobitz II), symptoms, and anatomical location of the block, with permanent pacemaker implantation being the definitive treatment for symptomatic patients and those with Mobitz type II block. 1

Types of Second-Degree Heart Block and Their Significance

• Mobitz Type I (Wenckebach): Characterized by progressive PR interval prolongation before a blocked P wave, usually occurring at the AV node level 1
• Mobitz Type II: Characterized by constant PR intervals before and after blocked P waves, usually occurring within or below the His bundle 1
• 2:1 AV Block: Cannot be classified as Type I or II but can be nodal or infranodal 2, 3

Treatment Algorithm Based on Type and Symptoms

For Mobitz Type I (Wenckebach)

• Asymptomatic patients without structural heart disease:

  • Observation is generally recommended as progression to higher-degree block is uncommon 1
  • Discontinuation of causative medications (beta-blockers, calcium channel blockers, digoxin) if applicable 4

• Symptomatic patients:

  • Permanent pacemaker implantation is recommended for patients with symptoms attributable to the block (syncope, presyncope, fatigue) 1
  • Electrophysiological study (EPS) may be considered to determine the site of block if unclear from ECG 1

For Mobitz Type II

• All patients (symptomatic or asymptomatic):

  • Permanent pacemaker implantation is strongly recommended due to high risk of progression to complete heart block and sudden cardiac death 1
  • Atropine is not effective and should not be relied upon for Mobitz type II block with wide QRS complexes 5

• Emergency management:

  • Temporary pacing may be required until permanent pacemaker can be implanted 1

For 2:1 AV Block

• Determine the level of block:
  • If narrow QRS: Likely AV nodal (treat as Mobitz I) 1, 3
  • If wide QRS: Likely infranodal (treat as Mobitz II) 1, 3
  • Electrophysiological study may be required for definitive diagnosis 1

Special Considerations

• Lyme carditis with AV block:

  • Parenteral antibiotics (ceftriaxone) recommended for hospitalized patients 1
  • Temporary pacemaker may be required for advanced heart block 1
  • Oral antibiotics for completion of therapy and for outpatients 1

• Exercise-induced AV block:

  • Permanent pacing is recommended as this indicates disease in the His-Purkinje system and has poor prognosis 1

• Athletes with AV block:

  • Athletes with Wenckebach block who do not develop type II or complete heart block during exercise can participate in competitive sports 1
  • Athletes with Wenckebach block and coexisting bundle-branch block should undergo EPS 1

Monitoring and Follow-up

• For patients with Mobitz I not receiving pacemaker:

  • Regular ECG monitoring to detect progression to higher-degree block 1
  • Holter monitoring may be useful to detect intermittent higher-degree block 1

• For patients with pacemakers:

  • Regular device checks as per standard pacemaker follow-up protocols 1

Prognosis

• Untreated Mobitz type II block has poor prognosis with high risk of progression to complete heart block 1, 6
• Paced patients have significantly better five-year survival (78%) compared to unpaced patients (41%) 7
• Even patients with Mobitz type I block may have similar poor prognosis to those with Mobitz type II if left untreated 7

Common Pitfalls to Avoid

• Misdiagnosing Mobitz type II as type I or vice versa - careful examination of PR intervals is essential 2, 8
• Failing to recognize pseudo-AV block caused by concealed His bundle or ventricular extrasystoles 3
• Relying on atropine in type II second-degree or third-degree AV block with wide QRS complexes 5
• Assuming all Mobitz type I blocks are benign - chronic Mobitz I may have similar prognosis to Mobitz II 7