Second-degree atrioventricular block in a diarrheic calf-camel (Camelus dromedarius)

Atrioventricular block (AVB) is a type of heart block in which the conduction between the atria and ventricles of the heart is impaired. The purpose of the present paper is to report the occurrence of second-degree AVB in a diarrheic calf-camel. A 7-day-old female calf-camel (Camelus dromedarius) weighting approximately 50 kg was referred to the veterinary hospital with a 5-day history of diarrhea, prostration, tremors, sternal recumbency, and muscular weakness. Clinical examination revealed increases in rectal temperature (RT 39.9 °C), heart rate (HR 124 beats min⁻¹), and respiratory rate (RR 49 breaths min⁻¹) with hyperemic mucous membranes. Incidentally, in precise cardiac auscultation, the clinicians found out irregularities in the rhythm and recognized the random absence of S₁ and S₂ heart sounds. Moreover, no palpable pulse and jugular pulsation (JP) could be detected during the cardiac irregularities. Other clinical examinations showed no sign of cardiovascular insufficiency such as edema and jugular distension (JD) and no murmur was auscultated. Before the treatment, serum levels of magnesium were significantly lower than the reference values, while the concentration of potassium was significantly higher than the reference value (P < 0.05). Two days after treatment, serum electrolyte levels were within reference ranges. There were no significant differences in the serum levels of other electrolytes (sodium, chloride, calcium, and phosphorous) and all cardiovascular biomarkers (homocysteine, cardiac troponin I, and enzymes such as creatine kinase isoenzyme MB and lactate dehydrogenase) before and 2 days after the treatment (P > 0.05). Based on the cardiovascular examination (observation, palpation, and auscultation), heart block was suspected. ECG recording confirmed the presence of sinus arrhythmia (SA) and heart block including first-degree and Mobitz type 1 (Wenkebach) second-degree. Finally, since the AVB was resolved after correction of serum electrolyte imbalance, it can be suggested that electrolyte disturbance was the main cause of Mobitz I second-degree AVB in the above described diarrheic calf-camel.