Multiform ventricular ectopic rhythm by combined parasystolic and reentrant activities

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Arrhythmias

Background:

• Multiform ventricular ectopic rhythm (MVER) is characterized by ventricular ectopic beats (VEBs) with varying QRS morphologies.
• Ventricular parasystole (VP) involves an independent ventricular pacemaker with entrance block.
• Understanding the mechanisms of MVER, especially in the presence of VP, is crucial for arrhythmia management.

Observation:

• Four patients with ventricular parasystole (VP) and MVER were studied using 24-hour ambulatory ECG.
• Two patients exhibited coexisting VEBs with fixed coupling and VP beats of different configurations.
• Case 1 showed VEBs coupled identically to sinus and VP beats, suggesting reentry from both pacemakers.
• Case 2 presented intermittent VP with type II second-degree entrance block, where VEBs were coupled to sinus and fusion beats.

Findings:

• VEBs in Case 1 suggested a reentry mechanism initiated by both sinus and VP pacemakers.
• In Case 2, coupled VEBs appeared dependent on sinus beats reaching the VP focus, indicating reentry with prematurity-dependent aberrancy.
• The study proposes that MVER can result from the interplay of an automatic ventricular ectopic focus and reentrant activity originating from an area of automaticity.

Implications:

• These findings highlight complex electrophysiological mechanisms underlying MVER in specific patient populations.
• The coexistence of automaticity and reentry provides a potential explanation for MVER in patients with VP.
• Further research into these mechanisms may lead to improved diagnostic and therapeutic strategies for complex ventricular arrhythmias.