Atypical Wenckebach periodicity simulating Mobitz II AV block

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Arrhythmias

Background:

• Wenckebach periodicity describes a pattern of heart block.
• Distinguishing between typical and atypical forms is clinically relevant.
• Atypical variants can mimic more severe block types, complicating diagnosis.

Purpose of the Study:

• To determine the incidence of typical and atypical Wenckebach periodicity.
• To analyze Wenckebach cycles in the AV node and His-Purkinje system.
• To characterize a specific atypical Wenckebach variant that simulates Mobitz type II block.

Main Methods:

• Analysis of 144 Wenckebach cycles in the AV node and 118 in the His-Purkinje system from 11 patients.
• Definition and identification of a 'pseudo-Mobitz II' pattern based on PR interval variations and post-block intervals.
• Comparison of the frequency of typical versus atypical Wenckebach cycles.

Main Results:

• Atypical Wenckebach cycles were more prevalent: 67% in the AV node and 69% in the His-Purkinje system.
• The pseudo-Mobitz II pattern was observed in 19% of atypical AV nodal and 17% of atypical His-Purkinje Wenckebach periods.
• Atypical Wenckebach is more common than typical Wenckebach periodicity.

Conclusions:

• Atypical Wenckebach periodicity is more common than typical Wenckebach.
• A pseudo-Mobitz II pattern can arise from atypical Wenckebach, mimicking Mobitz type II block.
• Accurate differentiation is crucial, particularly in acute myocardial infarction settings.