Duration of the QT interval in healthy cats
Ware, W.A.; Christensen, W.F.
American Journal of Veterinary Research 60(11): 1426-1429
1999
ISSN/ISBN: 0002-9645 PMID: 10566821 Document Number: 498360
20 healthy cats were used to develop a clinically useful model for predicting QT interval duration as a function of heart rate. For all cats, results of a physical examination, electrocardiography and echocardiography were normal. 24-h heart rate and rhythm data were collected by ambulatory electrocardiography. Hourly ECG segments were obtained from the 24-h recordings. Mean heart rate and the mean of 5 QT interval measurements were calculated for each of 479 usable ECG segments. Analysis of covariance was used to develop models to describe variability in QT interval duration. Prediction equations (Rsuperscript 2=0.81) including terms for heart rate, (heart rate)superscript 2, age group (1 to 4 vs 8 to 14 years old) and their interactions were developed. Sex, individual cat and time of day were of little value in predicting QT interval duration. A simplified prediction equation without age group (Rsuperscript 2=0.71) also was developed and had better predictive ability than reported correction formulas for QT interval duration. Prediction equations with 95% prediction intervals for expected QT interval duration in healthy cats were generated. Abnormal QT interval duration can be associated with cardiac electrical instability, yet QT interval duration is greatly influenced by heart rate.