What is the management of second-degree atrioventricular (AV) block Mobitz type 2?

Management of Mobitz Type II Second-Degree AV Block

All patients with Mobitz Type II second-degree AV block require permanent pacemaker implantation regardless of symptoms, as this is a Class I indication due to the unpredictable and potentially life-threatening risk of progression to complete heart block. 1

Immediate Stabilization

Acute Management Steps

• Place transcutaneous pacing pads immediately upon recognition of Mobitz Type II, as this rhythm carries high risk of sudden progression to complete heart block 1
• Initiate continuous cardiac monitoring until permanent pacemaker is implanted 1
• Assess hemodynamic status for signs of compromise including hypotension or low cardiac output 1

Temporizing Measures for Symptomatic Patients

• Atropine 0.5 mg IV every 3-5 minutes up to maximum 3 mg total dose may be attempted, though it is often ineffective since Mobitz Type II occurs in the His-Purkinje system below the AV node where atropine has limited effect 1
• Arrange urgent transvenous temporary pacing for hemodynamically unstable patients, with transcutaneous pacing serving as a bridge until transvenous access is obtained via femoral, internal jugular, or subclavian veins to the right ventricular apex 1

Diagnostic Confirmation

Key ECG Features

• Constant PR intervals before and after blocked P waves, distinguishing it from Mobitz Type I which shows progressive PR prolongation 1
• Periodic single nonconducted P waves with constant rate 1

Essential Workup

• Obtain electrolyte panel to rule out reversible causes 1
• Perform transthoracic echocardiography (Class I recommendation) to assess for underlying structural heart disease 1

Definitive Management: Permanent Pacemaker

Indications (Class I)

• Pacemaker implantation is mandatory for all patients with Mobitz Type II, even if completely asymptomatic 1
• The block occurs in the His-Purkinje system with unpredictable progression and slower, unreliable escape mechanisms compared to Mobitz Type I 1
• Risk of sudden progression to complete heart block with Adams-Stokes attacks and sudden death 1

Device Selection and Programming

• Dual-chamber pacemakers should be programmed to maintain native AV conduction when possible to prevent pacing-induced ventricular dysfunction 1
• For patients with neuromuscular diseases (myotonic dystrophy, Kearns-Sayre syndrome), permanent pacing with defibrillator capability is recommended if meaningful survival >1 year is expected 1
• For infiltrative cardiomyopathies (cardiac sarcoidosis, amyloidosis), consider pacemaker with defibrillator capability 1

Special Clinical Scenarios

Postoperative Mobitz Type II

• Pacemaker implantation is recommended for postoperative Mobitz Type II that persists beyond 7-10 days 1
• Most postoperative AV block recovers within 7-10 days; monitor during this period 1
• Pacemaker should be implanted before discharge for patients who develop Mobitz Type II after alcohol septal ablation, surgical myectomy, tricuspid valve surgery, or transcatheter aortic valve replacement 1

Acute MI Setting

• Mobitz Type II represents a Class Ia indication for temporary transvenous pacing, followed by permanent pacemaker if block persists 1

Critical Pitfalls to Avoid

• Do not delay pacemaker placement, as Mobitz Type II can progress rapidly and unexpectedly to complete heart block with hemodynamic collapse 1
• Do not confuse with Mobitz Type I (Wenckebach), which typically occurs at the AV node with more reliable escape rhythms and generally benign prognosis 1
• Do not assume the rhythm is benign based on lack of symptoms—asymptomatic patients still require pacemaker 1
• Exercise testing may reveal exercise-induced worsening of AV block in some patients 1

Post-Implantation Follow-up

• Regular device checks are needed to ensure proper pacemaker function 1
• Studies show permanent pacing improves survival in patients with high-grade AV block, especially if syncope has occurred 1