7.8.7 Pre-excitation syndromes
Pre-excitation syndromes, including the electrocardiographic equivalent of Wolff-Parkinson-White syndrome, (a well-recognised condition in humans), have been reported in a number of horses. These syndromes are associated with an abnormal conduction pathway which bypasses the AV node. This is recogelectrocardiographically by a short PR interval and a wide QRS complex, with a small notch at the initial portion of the complex (a delta wave). The clinical significance of the condition is unclear. In some animals it may not be associated with any clinical signs and is only detected if an ECG is recorded. In other anithe aberrant conduction pathway may allow re-entrant supraventricular tachydysrhythmias to develop.