HorseSport.com - Full Article
Irregularities in heart rhythm are normal in horses; lub dub, lub dub, pause, lub dub is perfectly natural. There are some irregularities cause concern.
By: Teresa Pitman | July 24, 2012
That comes as no surprise to Ontario Veterinary College professor Dr. Peter Physick-Sheard, who has been studying how equine hearts function in his research with some other equine athletes – Standardbred racehorses. “I tell my students that if the horse’s heart is beating steadily like a metronome, step back – because he might fall over on them,” Physick-Sheard says. Irregularities in heart rhythm are normal in horses; hearing lub dub, lub dub, pause, lub dub is perfectly natural. However, there are some types of irregularities that can cause concern.
Physick-Sheard explains that each contraction or beat of the heart is preceded by electrical activity initiated in a special area of the heart (called the pacemaker) triggering biochemical changes that signal the heart muscle to contract. ECGs (electrocardiograms) detect that electrical signal. “Every wiggle on the ECG screen means a cardiac contraction,” explains Physick-Sheard. The data from an ECG can also indicate whether or not the heart muscle is healthy or whether the heart’s internal conduction system is normal, and can provide other information about heart function...
Read more here: