Objective

This study was conducted to determine if cardiotoxicity could be detected, before other clinical signs, by measures of heart rate variability.

Materials & Methods

Seven healthy beagle hounds were given intracoronary injections of doxorubicin at a dose of 0.75 mg/kg once a week for 4 weeks. 5-minute ECG's were recorded at baseline and at the ninth week, and heart rate variability was expressed in both time and frequency domains. Ventricular function was quantified using shortening fraction and systolic time intervals (PEP/ET) obtained from M-mode echocardiograms when dogs were mildly sedated with butorphanol.

Results

Animals received doxorubicin had significantly lower the standard deviation of RR intervals (SDNN) and the square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD) at the ninth week compared to the baseline. The fractional shortening decreased significantly (p<0.05) while PEP/ET ratio increased significantly (p<0.05). SDNN was correlated with fractional shortening (r = 0.76, P<0.05) and PEP/ET ratio(r = 0.75, P<0.05) at the ninth week.

Conclusion

The present study suggests that the total power expression of heart rate variability is useful for prediction of the cardiotoxicity produced by doxorubicin.