Complete AV block in a neonatal foal suffering from nutritional myodegeneration

Abstract

This case report concerns a 1-day-old, full-term Quarter Horse colt presented due to a progressive inability to rise and nurse. Besides the general weakness, a marked bradycardia was evident, which was caused by a third-degree atrioventricular (AV) block. Subsequently, the diagnosis of acute nutritional myodegeneration (NMD) was made based on clinical signs, elevated muscle enzymes, ECG findings, as well as low serum selenium and vitamin E values. Despite intensive care and supportive therapy, the foal´s condition deteriorated, and euthanasia was elected. Necropsy confirmed the diagnosis of NMD and revealed diffuse necrosis and inflammatory infiltration of the skeletal and myocardial musculature, as well as the cardiac conduction system which might have resulted in complete AV block.

Cardiac arrhythmias as a potential sign of systemic disease: Which laboratory tests are useful?

“…The clinical signs could be attributed to massive rhabdomyolysis, although they could also be associated with the pathological bradycardia. The arrhythmia detected in this case was a rather unusual consequence of cardiac involvement with myocardial inflammation and necrosis (Conze et al., 2022). Third‐degree AV block in itself can cause lethargy, syncope and episodic collapse (Keen, 2020).…”

“…In the case report by Conze et al. (2022), echocardiography revealed a hyperechoic zone in the atrioventricular node region which was indicative for myocardial damage. This should be differentiated from the normal echogenic appearance of the ventral part of the interatrial septum which can often be seen on a four‐chamber view in healthy individuals ( Figure ).…”

“…Nutritional myodegeneration was suspected in the case report by Conze et al. (2022) based on the markedly increased muscle enzymes. The diagnosis was confirmed by the analysis of vitamin E and selenium concentrations in blood samples of the foal and dam, which revealed remarkably low selenium levels.…”

“…Serum biochemistry to assess muscle enzymes, renal function and hepatic function is helpful to identify the presence of systemic disease or to assess the consequences of primary cardiac disease. Nutritional myodegeneration was suspected in the case report by Conze et al (2022) based on the markedly increased muscle enzymes. The diagnosis was confirmed by the analysis of vitamin E and selenium concentrations in blood samples of the foal and dam, which revealed remarkably low selenium levels.…”

“…However, the clinical presentation is often unspecific and primary cardiac disease may also result in systemic clinical signs. For example, the case report by Conze et al (2022) in this issue of Equine Veterinary Education describes a foal presented due to progressive inability to rise and nurse, which showed bradycardia caused by third-degree atrioventricular (AV) block at presentation. While the foal's weakness and apathy could also be caused by other conditions, blood work confirmed underlying nutritional myodegeneration.…”