3.5.4 Other abnormal heart sounds
Systolic clicks are short, sharp sounds heard in mid-systole. They are uncomClicks are usually of unknown significance, although they are seldom associated with significant disease. There are a variety of causes including minor abnormalities of the chordae tendineae and AV valve prolapse. If a systolic click is heard, an echocardiographic examination may be helpful, in order to rule out significant cardiac disease.
Pericardial friction rubs
Pericardial disease is uncommon in the horse and there are few specific clinical findings which indicate its presence. However, a pericardial friction rub is a specific indication of the presence of pericardial disease, although not indicative of its severity. The sound is fairly distinctive and has been likened to the creaking of a door or the branch of a tree. It may be a single sound but it is usually biphasic or sometimes triphasic, occurring in systole and diastole. Subjectively, it sounds extracardiac, but it is in time with the cardiac cycle. It is caused by rubbing of the visceral pericardial surface with the epicardium. If a pericardial rub is heard, echocardiography is indicated as the most specific method of diagnosis of pericardial disease.
Gallop sounds are a combination of the third and fourth heart sounds, resulting in a three component sound to the cardiac cycle similar to the sound of the footfall of a galloping horse. While these sounds are abnormal in humans and small animals, in which they usually indicate the presence of significant myocardial disease, they are normal at higher heart rates in the horse.