The presence of a particular cardiac protein in a colicking horse’s blood may reveal important information about his condition and prognosis, according to a new study.
Researchers at the University of Pennsylvania tracked 111 horses admitted to the clinic for colic, drawing blood when the horses arrived and again 12 and 24 hours later---or 12 and 24 hours after surgery if that was required. The researchers also performed a 24-hour electrocardiogram (ECG) on each horse, either the day after admission or the day after surgery, to detect any arrhythmia (irregular heartbeats). The data showed that horses admitted for colic with elevated levels of the protein cardiac troponin I (cTnI) were 24 times more likely to require surgical treatment, 3.86 times more likely to have irregular heartbeats and 4.17 times more likely to die or be euthanatized. “cTnI is a protein released from damaged myocardial cells, so it should be detected in circulating plasma/serum only in the face of cardiac damage,” explains Olga Seco, LV. “It has been a useful marker to detect cardiac damage in emergency situations in humans, as it can be detected in blood very early.”
The researchers believe this finding points to a possible chain of physiological events: “We know horses with colic frequently sustain cardiac arrhythmias,” says Seco. “[The arrhythmias] could be due simply to electrolyte imbalances, to endotoxemia, or to cardiac damage, so we tried to determine which was more likely.” Given the fact that cTnI is released only by damaged myocardial cells and that a high percentage of horses in the study had a high cTnI detected, the researchers concluded that a high percentage of horses with colic sustain myocardial injury that can be the cause of the arrhythmias. The study wasn’t designed to determine if the arrhythmias were present prior to colic, but the two conditions have been closely associated in other studies.
Seco says that blood tests for cTnI could provide valuable clues to the prognosis of colicking horses, particularly those with detected arrhythmias: “I don’t think we should be checking the heart in all colicky horses, but we need to be aware that certain severe diseases are causing cardiac damage and will also affect the prognosis.”
This article first appeared in EQUUS issue #444, September 2014.