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

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 ( c K + ) in a large population of neonatal diarrheic calves. Animals One hundred and thirty neonatal diarrheic calves (age ≤21 days). Methods Prospective observational study involving calves admitted to a veterinary teaching hospital. Results Hyperkalemic calves ( c K + : 5.8‐10.2, blood pH: 6.55‐7.47) had significantly ( P  < .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 c K + within the reference range. The first ECG changes in response to an increase in c K + were an increase in voltages of P, Ta, S, and T wave amplitudes. Segmented linear regression indicated that P wave amplitude decreased when c K + >6.5 mmol/L, S wave amplitude voltage decreased when c K + >7.4 mmol/L, QRS duration increased when c K + >7.8 mmol/L, J point amplitude increased when c K + >7.9 mmol/L, and ST segment angle increased when c K + >9.1 mmol/L. P wave amplitude was characterized by a second common break point at c K +  = 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 c K + .