Wolff-Parkinson-White (Ventricular Pre-excitation) Syndrome in a Thoroughbred

Abstract

1. WPW syndrome was incidentally observed in a clinically healthy thoroughbred yearling during the recording of electrocardiograms for the purpose of studying electro cardiography in the race horse. 2. The horse was first examined in November at the age of one year. Thereafter, he was examined three times until February at the age of three years. WPW syndrome was observed at every examination. 3. Frequency of occurrence of the syndrome at rest tends to increase with advancing years. Also, it increased after ten minutes exercise. 4. WPW syndrome appeared successively in one occasion, while it appeared sporadi cally in another occasion. 5. PQ interval of normal pattern in A-S lead was 0.30-0.50 sec., showing first degree partial block at the third and the fourh experiments. That of WPW was shortened to 0.24-0.27 sec. in all the experiments. 6. Duration of QRS complex in A-S lead was prolonged from 0.08-0.11 sec. in normal pattern to 0.16-0.20 sec. in WPW. 7. QT interval in A-S lead was prolonged from 0.480.56 sec. in normal pattern to 0.53-0.64 sec. in WPW. 8. Configurations of QRS complex in A-S lead were rS or QS in normal pattern and Rs in WPW. Configuration of QRS complex in WPW was stabilized in some occasion and changed gradually in another occasion. 9. Configuration of T wave in A-S lead was small negative-large positive diphasic or positive monophasic in normal and large negative-small positive diphasic in WPW. 10. Neither paroxysmal tachycardia, nor auricular fibrillation was associated in the case.