Atrial alternans: experimental echocardiographic and hemodynamic demonstration during programmed pacing

Area of Science:

• Cardiology
• Physiology

Background:

• Atrial alternans, a beat-to-beat variation in atrial contraction, is not well understood.
• Its hemodynamic significance and clinical recognition require further investigation.

Purpose of the Study:

• To demonstrate mechanical atrial alternans during programmed atrioventricular pacing in a canine model.
• To explore the utility of this method for recognizing atrial alternans and its hemodynamic impact.

Main Methods:

• Simultaneous hemodynamic and echocardiographic recordings were performed in five open-chest dogs.
• Measurements were taken during two phases: intact atrioventricular (A-V) conduction and experimentally induced complete A-V block.
• Atrial alternans was induced and observed during rapid atrial stimulation at varying cycle lengths (250-120 ms).

Main Results:

• Mechanical atrial alternans was successfully demonstrated in dogs under programmed A-V pacing.
• Phase I (intact A-V conduction) showed complex A-V conduction disturbances with superimposed atrial and ventricular alternans.
• Phase II (complete A-V block) allowed observation of atrial alternans during programmed ventricular pauses.

Conclusions:

• Programmed A-V pacing is an effective method for demonstrating mechanical atrial alternans.
• This technique is anticipated to improve the recognition of atrial alternans in clinical scenarios.
• Further research is warranted to elucidate the hemodynamic significance of atrial alternans.