Endocardial electro-anatomic mapping in healthy horses: Normal sinus impulse propagation in the left and right atrium and the ventricles.

The research examines the normal patterns of electrical impulse conduction in the atria and ventricles of the hearts of healthy horses, through the use of a three-dimensional mapping system. The study provides crucial insights into the connection between the physiological electric activity in the heart and electrocardiogram (ECG) readings, which can support further research into complex heart rhythm abnormalities in horses.

Research Methodology

• The researchers used a 3D electro-anatomical mapping system, a technology that gives a detailed understanding of the heart’s electrical system, to evaluate the depolarisation patterns (process of nerve impulse transmission) in both the atrial and ventricular sections of the heart.
• The study was conducted on seven healthy horses under general anaesthesia.
• The team analysed the bipolar activation maps of the endocardium, the interior lining of the heart.

Results and Observations

• The initial atrial activation was located at the peak of the terminal crest.
• Only one pathway conducting impulses between the two atria was identified.
• The first and second deflections of the P wave represented the right and left atrial depolarisation respectively.
• Electrograms of the Bundle of His, a collection of heart muscle cells specialized for electrical conduction, were recorded in 5 out of 7 horses.
• The onset of left ventricular activation began at the mid-septum while the right ventricular activation started apically from the supraventricular crest.
• Additional separate depolarisations happened at the mid free wall level.
• Further ventricular depolarisation exploded in a specific pattern.
• Electrically active tissues were found in all pulmonary veins.

Findings and Conclusion

• In contrast to prior studies, all parts of the ventricular depolarisation contributed to the surface ECG QRS complex, the graphical deflections seen on an ECG indicating the depolarisation of the ventricles.
• The study provides a foundational reference for the normal sinus impulse endocardial propagation pattern and conduction velocities in equine atria and ventricles.
• This baseline understanding of the normal electric activity in healthy equine hearts is critical for further research into the pathophysiology of complex heart arrhythmias in horses.