An 82-Year-Old Man with Palpitations

Differential Diagnosis

• Sinus tachycardia
• AV block second degree ─ Mobitz I (Wenkebach)
• Multifocal atrial tachycardia
• Atrial fibrillation
• Third-degree AV block

Diagnosis
This patient has a Mobitz I (Wenkebach) second-degree AV block, revealed in the ECG by progressive lengthening of the PR interval until there is a nonconducted P wave. The first two arrows below show the PR interval lengthening and then the last arrows a nonconducted P wave.

Learnings

• There is a progressive lengthening of the PR interval, until there is a nonconducted P wave (see arrows above)
• The P-P interval is typically constant
• Medical conditions which may cause Wenkebach include myocardial infarction, myocarditis, electrolyte abnormalities, and postcardiac surgery
• Medications include beta-blockers, calcium channel blockers, and digoxin 

Pearls for initial management and considerations for transfer:

• Compare to previous ECG, if available
• Patients without identifiable cause after history do not require further testing
• Patients who are asymptomatic without an identifiable cause do not require treatment
• Patients who are symptomatic with tachycardia, hypotension, chest pain, shortness of breath, or altered consciousness should be transferred
• Distinguish from Mobitz II second-degree AV block and third-degree AV block, which are not benign rhythms