Management of Second Degree Heart Block Type 1 (Wenckebach)

Initial Assessment

Assess for signs of hemodynamic compromise including hypotension or evidence of low cardiac output, as recommended by the American College of Cardiology 1
Obtain a 12-lead ECG to confirm the diagnosis and evaluate for coexisting conduction abnormalities, as suggested by the American Heart Association, published in Circulation 2
Perform an echocardiogram to exclude underlying structural heart disease, according to the guidelines in Circulation 2

Patients without structural heart disease can participate in all competitive sports and normal activities, as stated in Circulation 2
Activity restrictions should be recommended based on the type of structural heart disease, as advised in Circulation 2
More frequent monitoring may be warranted for patients with structural heart disease, as recommended in Circulation 2

Atropine 0.5 mg IV can be administered, repeated every 5 minutes as needed up to a total dose of 2 mg, as recommended by the American College of Cardiology 3, 1
Atropine is indicated for symptomatic type I second-degree AV block associated with acute inferior myocardial infarction, as stated by the American College of Cardiology 3, 1
Temporary transvenous pacing should be initiated for hemodynamically unstable patients or those not responding to atropine, as recommended by the American College of Cardiology 3, 1

It's essential to distinguish 2:1 Wenckebach physiology from true Mobitz Type II block, which can usually be achieved with a stress test, as suggested in Circulation 2

Electrophysiological study may be indicated in athletes with Wenckebach AV block and coexisting bundle-branch block, as recommended in Circulation 2
Electrophysiological study may be warranted when there is concern for progression to higher-degree AV block, as advised in Circulation 2

Doses of atropine <0.5 mg may paradoxically worsen AV block due to central reflex stimulation of the vagus, as warned by the American College of Cardiology 1
Atropine is not indicated for asymptomatic patients with sinus bradycardia >40 beats/min, as stated by the American College of Cardiology 1
Repeated administration of atropine may produce adverse central nervous system effects, including hallucinations and fever, as cautioned by the American College of Cardiology 1

Second degree Mobitz type I (Wenckebach) heart block is characterized by progressive lengthening of the PR interval before a blocked P wave and generally reflects disease within the atrioventricular (AV) node, with a typically benign prognosis that rarely requires intervention in asymptomatic individuals 4, 5
Mobitz type I (Wenckebach) is a form of second-degree AV block where some, but not all, atrial impulses are conducted to the ventricles 4, 5
The block typically occurs within the AV node (proximal conduction system) rather than below it 4, 5

Wenckebach block generally has a benign prognosis compared to Mobitz type II block 4, 5
It is commonly observed in well-trained endurance athletes, especially during sleep 6
Unlike Mobitz type II, Wenckebach rarely progresses to complete heart block or sudden death 4, 5

For patients with Wenckebach block, evaluation should include assessment for symptoms attributable to the block (syncope, presyncope, dizziness) 6
Echocardiogram to exclude underlying structural heart disease is recommended 6
Exercise stress test to observe the response of the conduction system to increased sympathetic tone is suggested 6
Asymptomatic patients with isolated Wenckebach block generally require no specific treatment 4, 5
For symptomatic patients with marked first-degree or second-degree Mobitz type I AV block with symptoms clearly attributable to the block, permanent pacing may be reasonable, according to the American College of Cardiology 7
In athletes with Wenckebach block who have no symptoms or structural heart disease, participation in all competitive athletics is generally permitted 6

Mobitz type II typically occurs below the AV node and is considered abnormal 6
Mobitz type II has a worse prognosis and is generally considered an indication for permanent pacemaker implantation 6
It's essential to distinguish 2:1 Wenckebach physiology from true Mobitz type II block, which can usually be achieved with a stress test 6