Dilated Cardiomyopathy and QRS Complex Duration in Dogs

Dilated cardiomyopathy (DCM) is a common cause of cardiac disease in both humans and dogs. Several studies have shown that a prolonged QRS complex duration is correlated to ventricular chamber enlargement, systolic dysfunction and higher chances of heart failure in humans.
Keeping this in mind, the authors of this article decided to explore the prognostic value of QRS complex duration in dogs with dilated cardiomyopathy (DCM). This retrospective study was based on the medical records of 266 dogs diagnosed with DCM, which included ECG tracings and the dogs’ survival times.
After the QRS complex duration was measured, these dogs were distributed into 2 groups. Dogs with a QRS complex duration of <60 ms were placed in Group 1 and dogs with a QRS complex duration of ≥60 ms were assigned to Group 2. The 75 dogs in Group 1 had a considerably higher average survival time (25 weeks) than the 191 dogs in Group 2 (13 weeks). This association was also verified when the QRS complex duration was analyzed as a continuous variable and not just the cut-off value of 60 ms.
The authors concluded that prolonged QRS complex duration in dogs with DCM is related to a decreased survival time, and that breed also has a huge influence in these dogs’ longevity. Cocker Spaniels with DCM presented the longer lifespans while Dobermans showed the shortest survival times. According to this study, measuring QRS complex duration provides a meaningful prognostic factor of cardiac disease mortality.
In Pedro, Brigite & V Alves, Joana & Cripps, Peter & J Stafford Johnson, Mike & Martin, Mike. (2011). Association of QRS duration and survival in dogs with dilated cardiomyopathy: A retrospective study of 266 clinical cases. Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology. 13. 243-9. 10.1016/j.jvc.2011.09.003.