Concealed ventricular extrasystoles due to interference and due to exit block

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Arrhythmias

Background:

• Ventricular extrasystoles can occur in patients with normal sinus rhythm.
• The relationship between sinus cycle length and the manifestation of these extrasystoles is complex.
• Existing rules, such as "concealed bigeminy" and the "rule of bigeminy," describe patterns of extrasystole appearance.

Purpose of the Study:

• To report two cases illustrating "concealed bigeminy" and the "rule of bigeminy" in sinus rhythm with ventricular extrasystoles.
• To propose a novel mechanism explaining the governing principles of both rules.
• To elucidate the role of the ventricular-ectopic (V-E) junction in the genesis of these arrhythmias.

Main Methods:

• Case report analysis of two patients with sinus rhythm and ventricular extrasystoles.
• Observation of extrasystole patterns in relation to sinus cycle length.
• Theoretical modeling of the proposed mechanism involving the V-E junction.

Main Results:

• In rapid sinus rhythm, shortened cycles favor extrasystoles obeying "concealed bigeminy" (even intervening sinus impulses).
• In slow sinus rhythm, lengthened cycles favor extrasystoles obeying the "rule of bigeminy" (odd intervening sinus impulses).
• A proposed mechanism suggests alternating concealed extrasystoles due to V-E junction interference or exit block.

Conclusions:

• Sinus cycle length significantly influences the manifestation of ventricular extrasystoles.
• A unified mechanism involving interference and exit block at the V-E junction explains both observed rules.
• Understanding these mechanisms is crucial for interpreting complex ventricular arrhythmias in sinus rhythm.