Electrocardiographic findings in 130 hospitalized neonatal calves with diarrhea and associated potassium balance disorders.

Abstract

BACKGROUND: Hyperkalemia in neonatal diarrheic calves can potentially result in serious cardiac conduction abnormalities and arrhythmias. OBJECTIVES: To document electrocardiographic (ECG) findings and the sequence of ECG changes that are associated with increasing plasma potassium concentrations (cK) in a large population of neonatal diarrheic calves. ANIMALS: One hundred and thirty neonatal diarrheic calves (age &#x2264;21 days). METHODS: Prospective observational study involving calves admitted to a veterinary teaching hospital. RESULTS: Hyperkalemic calves (cK: 5.8-10.2, blood pH: 6.55-7.47) had significantly (P&#x2009;<&#x2009;.05) longer QRS durations as well as deeper S wave, higher T wave, and higher ST segment amplitudes in lead II than calves, which had both venous blood pH and cKwithin the reference range. The first ECG changes in response to an increase in cKwere an increase in voltages of P, Ta, S, and T wave amplitudes. Segmented linear regression indicated that P wave amplitude decreased when cK>6.5 mmol/L, S wave amplitude voltage decreased when cK>7.4 mmol/L, QRS duration increased when cK>7.8 mmol/L, J point amplitude increased when cK>7.9 mmol/L, and ST segment angle increased when cK>9.1 mmol/L. P wave amplitude was characterized by a second common break point at cK&#x2009;=&#x2009;8.2 mmol/L, above which value the amplitude was 0. CONCLUSIONS AND CLINICAL IMPORTANCE: Hyperkalemia in neonatal diarrheic calves is associated with serious cardiac conduction abnormalities. In addition to increased S and T wave amplitude voltages, alterations of P and Ta wave amplitudes are early signs of hyperkalemia, which is consistent with the known sensitivity of atrial myocytes to increased cK.