OBJECTIVETo find the characteristic parameters from electrocardiogram (ECG) which is most related to pathological progress, surface ECG was performed in mice at 2, 5, 9 and 13 week post surgery.

METHODSElectrocardiogram recordings: The mice were anaesthetized with tribromoethanol (250 mg/kg, i.p.). Lead II surface ECG were acquired by using the Biopac System MP150 at a rate of 5 kHz.

RESULTS(1) No arrhythmia was observed in Sham and 2-week Band mice. Spontaneous arrhythmias were observed in ECG recordings, with an incidence of 15%, 28% and 63% in 5-, 9- and 13-week Band mice, respectively. Tachyarrhythmias, such as frequent premature ventricular extrasystole, bigeminy, trigeminy, and paroxysmal tachycardia were found. (2) Analysis of ECG recordings revealed a significant prolongation of QT and QTc intervals. Compared with age-matched Sham mice, the increment in QT and QTc intervals was 20.4%, 32.7%, 49.7%, 61.0% and 27.1%, 32.1%, 43.9%, 59.1% at 2, 5, 9 and 13 week, respectively (P < 0.01). (3) The characteristic change in electrocardiogram was on the J wave. The amplitude of J wave was upward in Sham mice, and it was significantly flattened or inverted in Band mice. (4) Except that RR interval at 2 week showed a slight decrease, there was no significant change in PR interval and RR interval in Band mice.

CONCLUSIONIn the present study, we found that the increase incidence of spontaneous arrhythmias, prologation of QT interval and changes in the amplitude of the J wave in the surface ECG during progression of mouse cardiac hypertrophy and failure, and the progressive pattern indicated that a gradual aggravation of the ventricular repolarization delay in this mouse model.