Should a temporary transvenous pacemaker be placed in a patient who has achieved return of spontaneous circulation after cardiac arrest and is found to have a high‑grade atrioventricular block causing hemodynamic instability?

Temporary Transvenous Pacing After ROSC with High-Grade AV Block

In a patient with return of spontaneous circulation (ROSC) after cardiac arrest who has high-grade atrioventricular block causing hemodynamic instability, temporary transvenous pacing is indicated immediately as a bridge to either permanent pacemaker placement or resolution of the conduction disturbance. 1, 2, 3

Immediate Management Algorithm

Step 1: Stabilize and Assess Reversibility

• Initiate temporary pacing immediately for persistent hemodynamically unstable bradycardia refractory to medical therapy while evaluating for reversible causes 1, 2
• Rule out reversible etiologies first: acute MI, electrolyte abnormalities (especially hyperkalemia), drug toxicity, Lyme disease, hypothyroidism, myocarditis, and ischemia 3
• Atropine 0.5-1 mg IV (repeated every 3-5 minutes to maximum 3 mg total) is reasonable for AV nodal-level block but is completely ineffective for infranodal (His-Purkinje) blocks with wide QRS escape rhythms 1, 2, 3

Step 2: Choose Pacing Modality

• Transcutaneous pacing should be initiated immediately in unstable patients—do not delay for additional atropine doses 2, 3
• Transition to temporary transvenous pacing for anticipated prolonged support, as transcutaneous pacing has high complication rates (14-40%) and patient discomfort 2
• For extended temporary pacing needs, an externalized permanent active-fixation lead is preferred over standard passive-fixation temporary leads 3

Step 3: Determine Need for Permanent Pacing

Mandatory waiting period: Patients with AV block in the setting of cardiac arrest should undergo observation before determining permanent pacing need, as the block may be transient 1

Proceed to permanent pacing if:

• Persistent second-degree Mobitz type II, high-grade AV block, or third-degree AV block (especially infranodal) after the waiting period 1, 3
• Symptomatic or hemodynamically significant second- or third-degree AV block that does not resolve 1
• Recurrent episodes of transient high-grade AV block during the observation period 1

Do NOT place permanent pacemaker if:

• Transient AV block that completely resolves after treatment of reversible causes 1, 3
• AV block resolves within the observation period without recurrence 1

Critical Anatomic Distinction

The location of the block determines urgency and prognosis:

• Infranodal (His-Purkinje) blocks with wide QRS escape rhythms are high-risk, may progress rapidly to asystole, and require continuous monitoring until permanent pacing 3
• AV nodal-level blocks with narrow QRS junctional escape rhythms are more stable and may respond to atropine or aminophylline 3

Special Considerations in Post-Cardiac Arrest Context

• In acute MI with AV block, temporary pacing does not by itself constitute an indication for permanent pacing—the transient nature must be assessed 1
• Inferior wall MI with AV block may be vagally mediated or due to transient AV nodal ischemia and often responds to atropine or aminophylline 1, 3
• 88% of patients with third-degree AV block still require permanent pacemaker even after correction of reversible causes, so maintain high suspicion 3

Pharmacologic Adjuncts (While Preparing for Pacing)

• Beta-adrenergic agonists (isoproterenol, dopamine, dobutamine, epinephrine) may be used when coronary ischemia likelihood is low 3
• Aminophylline/theophylline can be considered for inferior MI-associated blocks or when atropine fails 2, 3
• Avoid atropine in post-cardiac transplant patients—it may cause paradoxical high-degree AV block due to denervation; use aminophylline or epinephrine instead 2

Common Pitfalls to Avoid

• Do not delay transcutaneous pacing while giving additional atropine doses in unstable patients—pacing should be initiated immediately when atropine fails 2, 3
• Do not use atropine for wide-QRS (infranodal) blocks—it is ineffective and wastes critical time 2, 3
• Do not discharge asymptomatic patients with high-grade AV block and high-risk features (escape rate <40 bpm, pauses ≥3 seconds, ventricular escape rhythm) without pacemaker placement 3
• Doses <0.5 mg of atropine may paradoxically worsen the block and should be avoided 2
• Do not remove temporary pacing capability until you have confirmed sustained resolution of the conduction disturbance over at least 24 hours 1