Effects of Trypanosoma Brucei on some Electrocardiographic Repolarisation Indices of Dogs.
The effect of acute T.brucei infection on some ECG repolarisation indices like QT dispersion (QTD), heart rate corrected QT dispersion (QTCD), T wave voltage expressed as T/R, Mean electrical axis (MEA), Heart rate (HR) and plasma potassium concentration was evaluated in dogs. Ten dogs inoculated with 1 ml of Phosphate buffered saline diluted blood containing 1×106 of the federe strain of the parasite had their ECG recorded on weekly basis for three weeks. Plasma potassium concentration was assayed in each dog before the electrocardiogram. Supraventricular arrhythmia, ventricular premature contraction, ventricular tachycardia and various degrees of Atrioventricular blocks were recorded from the eighth day of infection. T. brucei infected dogs had elevated heart rate during the period of infection in all the six leads studied. At various times during the infection, QT and QTC of the infected dogs were significantly lower than the uninfected ones in leads II and AVF. Although the T wave voltage was also increased in the infected dogs, the QTD QTCD, and the MEA were not affected by the infection. The QTD and the QTCD indices of arrhythmic dogs were however found to be significantly lower than in the non-arrhythmic dogs. The serum potassium concentration of the infected dogs was significantly lowered in the first two weeks of infection and then rose to the control level during the third week of infection. Serum potassium concentration in arrhythmic dogs was however not different from the non-arrhythmic ones. The increased heart rate and the shortened QT and QTC width seen during the course of the infection reflect the enhanced state of sympathetic activity and the propensity for arrhythmia in the infected dog. This result has shown that ECG changes and arrhythmia seen in this study may not strictly reflect structural and functional cardiac involvement but changes in ANS functions coupled with perturbation in electrolyte and the metabolic statues of the infected dogs may
