We note a tripling of the heart sounds. This may be due to splitting of the first or second heart sounds, presence of a systolic click, or a gallop rhythm (presence of an S3 or S4 sound). When the heart rate is fast it can be difficult to differentiate between some of these causes particularly the split sounds versus the gallops. A phonocardiogram can help differentiate these etiologies.
This case is an example of a gallop rhythm, specifically an S3 gallop. The finding of a gallop rhythm is usually a very strong “clue” to the presence of severe underlying heart disease. Recall that finding a heart murmur on a dog does not usually help us determine whether severe disease is present but finding a gallop rhythm is almost always evidence of severe underlying heart disease.
There are three premature beats present. The premature beats interrupt the cardiac rhythm. Based solely on auscultation we cannot differentiate between a ventricular or a supraventricular origin to these premature beats. Sometimes, as in this case, we are struck by the presence of the pause that follows the premature beat and not by the premature beat itself. Recall that premature beats are usually followed by a pause. Some clinicians note only the presence of pauses in the cardiac rhythm and are compelled to conclude that “dropped beats” have occurred which may not be the case.
As with the previous Heart Sound of the Month, based soley on the auscultation findings one cannot differentiate between supraventricular and ventricular premature beats.