What is the medical management for Mobitz II (second-degree atrioventricular block type II)?

Medical Management of Mobitz II Second-Degree Atrioventricular Block

Permanent pacemaker implantation is the definitive treatment for Mobitz Type II second-degree atrioventricular block, regardless of symptoms, due to high risk of progression to complete heart block and sudden death. 1, 2

Initial Assessment and Stabilization

• Place transcutaneous pacing pads immediately as Mobitz Type II has high risk of progression to complete heart block 2
• Obtain 12-lead ECG to confirm diagnosis and evaluate for coexisting conduction abnormalities 2
• Assess for signs of hemodynamic compromise including hypotension or evidence of low cardiac output 1
• Perform transthoracic echocardiography to assess for underlying structural heart disease (Class I recommendation) 2
• Obtain laboratory tests including electrolyte panel to rule out reversible causes 2

Acute Management Algorithm

For Symptomatic Patients:

• Atropine 0.5 mg IV every 3-5 minutes to a maximum total dose of 3 mg for temporary management 1
  • Caution: Doses <0.5 mg may paradoxically worsen bradycardia 1
  • Use cautiously in acute coronary ischemia as increased heart rate may worsen ischemia 1
• If atropine is ineffective or symptoms persist, initiate transcutaneous pacing 1
• Arrange for urgent transvenous temporary pacing for hemodynamically unstable patients 1

For All Patients with Mobitz Type II:

• Continuous cardiac monitoring is essential until permanent pacemaker is placed 2
• Arrange for permanent pacemaker implantation (Class I indication) 1, 2

Indications for Permanent Pacemaker

• Mobitz Type II second-degree AV block is a Class I indication for permanent pacing according to ACC/AHA guidelines, even in asymptomatic patients 1, 2
• Pacemaker implantation is recommended before discharge for patients who develop Mobitz Type II block after procedures such as:
  • Alcohol septal ablation or surgical myectomy 1
  • Tricuspid valve surgery 1
  • Transcatheter aortic valve replacement 1

Important Distinctions and Considerations

• Mobitz Type II is characterized by:
  • Constant PR intervals before and after blocked P waves 2
  • Usually associated with wide QRS complexes 1
  • Block typically occurs below the AV node in the His-Purkinje system 1, 3
• Must be distinguished from Mobitz Type I (Wenckebach), which has progressive PR prolongation before blocked beats and generally better prognosis 2, 4
• In patients with 2:1 AV block, determining if it's Mobitz I or II may require stress testing or electrophysiological study 4

Special Considerations

• Medication-induced Mobitz II (e.g., lithium) may require permanent pacing if block persists despite medication adjustment 5
• Rare causes like bee stings can induce Mobitz II block that may be reversible 6
• Exercise testing may reveal exercise-induced worsening of AV block in some patients 2
• After pacemaker implantation, regular device checks are needed to ensure proper function 2

Prognosis

• Without pacemaker implantation, Mobitz Type II has high risk of progression to complete heart block with potential for Adams-Stokes syndrome and sudden death 7, 3
• Studies show permanent pacing improves survival in patients with high-grade AV block, especially if syncope has occurred 1