Ventricular activation process in minipigs

Area of Science:

• Veterinary Cardiology
• Cardiac Electrophysiology
• Comparative Mammalian Anatomy

Background:

• Surface electrocardiogram (ECG) patterns in pigs differ from carnivores and ungulates.
• Ventricular activation pathways significantly influence the surface ECG.
• Understanding these pathways is crucial for interpreting pig cardiac function.

Purpose of the Study:

• To elucidate the specific pathways of ventricular activation in pigs.
• To compare pig ventricular activation with that of other mammalian groups.

Main Methods:

• Anesthetized pigs underwent hemithoracotomy for cardiac exposure.
• Epicardial and intramural electrograms were recorded using button and plunge electrodes.
• Simultaneous Z-axis ECGs were recorded for precise timing relative to QRS onset.

Main Results:

• Initial septal activation (0-10 ms) proceeds left-to-right.
• Epicardial activation spreads from cranial right and caudal left ventricles towards the septum (10-50 ms).
• Late septal activation (50-80 ms) occurs in an apical-basilar direction; endocardial-to-epicardial activation observed in ventricular free walls.

Conclusions:

• Pig ventricular activation pathways exhibit unique characteristics.
• These pathways are attributed to extensive Purkinje fiber penetration, similar to ungulates but unlike carnivores and primates.
• Findings provide insights into species-specific cardiac electrophysiology.