Does Type 2 heart block require urgent medical care?

Type 2 Heart Block Requires Urgent Medical Care

Type II second-degree (Mobitz) AV block is abnormal and generally requires urgent medical care as it is considered an indication for permanent pacemaker implantation due to high risk of progression to complete heart block and potential for sudden death. 1

Understanding Type II Second-Degree AV Block

Type II second-degree AV block differs significantly from Type I (Wenckebach) in several important ways:

• Anatomical location: Type II block occurs below the AV node in the His-Purkinje system, while Type I typically occurs within the AV node 2
• Risk profile: Type II block has a worse prognosis with frequent symptoms and high likelihood of progression to complete heart block 1
• ECG characteristics: Type II shows dropped beats without progressive PR interval prolongation before the blocked beat

Urgent Evaluation and Management Algorithm

1. Immediate assessment:

   • Assess for symptoms (syncope, presyncope, dizziness, fatigue)
   • Check vital signs with focus on heart rate and blood pressure
   • Obtain 12-lead ECG to confirm diagnosis
   • Continuous cardiac monitoring

2. Urgent consultation:

   • Cardiology consultation should be obtained immediately
   • Consider transfer to higher level of care with cardiac monitoring

3. Pacemaker indication assessment:

   • Class I indication (should receive pacemaker):
     • All symptomatic patients with Type II second-degree AV block 1
     • All asymptomatic patients with Type II second-degree AV block (permanent or intermittent) 1
     • Patients with Type II block after myocardial infarction with block in His-Purkinje system 1

Special Considerations

Acute Myocardial Infarction

In the setting of acute MI, Type II block carries particularly poor prognosis and requires immediate attention:

• Persistent advanced second-degree AV block or complete heart block after MI with block in His-Purkinje system is a Class I indication for permanent pacing 1
• Patients with acute MI who have intraventricular conduction defects have unfavorable short- and long-term prognosis with increased incidence of sudden death 1

Bundle Branch Block

The presence of bundle branch block with Type II second-degree AV block significantly increases risk:

• Type II block with coexisting bundle branch block requires electrophysiologic study (EPS) to identify intra-His-Purkinje or infra-His-Purkinje block 1
• Progression to complete heart block is more likely if left anterior fascicular block accompanies right bundle branch block 1

Pitfalls to Avoid

1. Misdiagnosis: Do not confuse Type II block with:

   • Non-conducted premature atrial contractions
   • Atrial tachycardia with block
   • Type I (Wenckebach) block with 2:1 conduction

2. Delayed intervention: Do not delay pacemaker implantation in asymptomatic patients with Type II block, as it is a Class I indication 1

3. Inadequate monitoring: Patients with Type II block require continuous cardiac monitoring until definitive treatment

4. Overlooking underlying causes: Always evaluate for potential reversible causes (drug toxicity, hyperkalemia, myocarditis) 2

5. Underestimating risk in younger patients: Even children with concerning second-degree block have a 30% risk of progressing to complete heart block or requiring a pacemaker 3