Degenerative mitral valve disease: Survival of dogs attending primary-care practice in England

Abstract

This study aimed to evaluate survival of dogs with degenerative mitral valve disease (DMVD). A retrospective cohort study of dogs with DMVD attending primary-care practices in England was undertaken. Cases of DMVD were identified within the electronic patient records (EPRs) of practices sharing data with VetCompass. Kaplan-Meier curves were used to explore survival and Cox regression models identified factors associated with hazard of death. The EPRs from 111,967 dogs, attending 93 veterinary practices between January 2010 and December 2011 identified 405 cases diagnosed with DMVD giving a prevalence of diagnosed DMVD of 0.36% (95% CI: 0.29-0.45%). A further 3557 dogs were classified as possible cases (heart murmurs consistent with DMVD). Overall, a total of 3962 dogs were classified as heart murmur cases (possible and diagnosed DMVD), giving a prevalence of 3.54% (95% CI: 3.26-3.84%). One hundred and sixteen (28.6%) of the diagnosed DMVD cases were incident, newly diagnosed with DMVD. The mean age at diagnosis was 9.52 years (95% CI: 8.98-10.14 years). Fifty-eight (50.0%) of the incident cases died during the study period. The median survival time (MST) for all-cause mortality was 25.4 months (95% CI: 20.4-34.4 months) after disease detection for DMVD cases. For possible cases, 121 (29.7%) from a random sample of 407 possible DMVD cases were incident cases (newly detected heart murmur consistent with DMVD during the study period). The mean age at which a heart murmur was first recorded in possible cases was 9.73 years (95% CI: 9.02-10.44 years). Forty-nine (40.5%) possible cases died during the study period. The MST for all-cause mortality was 33.8 months (95% CI: 23.7-43.1 months) after a heart murmur was initially detected. In the multivariable survival analysis for possible and diagnosed cases, Cavalier King Charles Spaniels (CKCSs) and other purebreds had higher hazards of death than crossbreds. Dogs weighing ≥20.0kg and older dogs had an increased hazard of death compared with those <20.0kg and younger dogs, respectively. The study highlights poorer survival for all-cause mortality in CKCSs and larger dogs. The reported survival characteristics could aid veterinary surgeons' advice on the prognosis for dogs with DMVD and help the assessment of the impact of the condition at a population level.

Keywords: Canine; Cardiac; Epidemiology; Primary-care practice; Survival.