Systolic time intervals in domestic ponies: alterations in a case of coarctation of the aorta.

This report describes the measurement of systolic time intervals in a nine year old female domestic pony which was found at necropsy to show coarctation of the aorta and bilateral ventricular hypertrophy. Electrocardiogram, phonocardiogram and direct arterial blood pressure were recorded from the pony in a standing unmedicated state and systolic time intervals were measured from the resulting tracings. A prolongation of left ventricular ejection time and shortening of the pre-ejection period were observed in comparison to a group of normal ponies similarly examined. Such changes are consistent with outflow tract obstruction. The pony was also hypotensive and this condition was interpreted as a long-term compensation for the obstructive lesion. It is likely that the changes in systolic time intervals were at this stage predominantly affected by the hypotension. The report notes that the existence of such a case of spontaneous cardiovascular disease in the pony population might suggest the utility of the animal as a resource in comparative cardiovascular physiology and medicine.