Survival Characteristics and Prognostic Variables of Dogs with Preclinical Chronic Degenerative Mitral Valve Disease Attributable to Myxomatous Degeneration

Abstract

Background: Preclinical myxomatous mitral valve degeneration (MMVD) includes a heterogeneous group of dogs. Therefore, identifying risk factors for progression of the disease is of clinical importance.Objectives: To investigate survival time and risk factors for clinical and echocardiographic variables taken at initial examination for clinical progression in preclinical MMVD dogs.Animals: A total of 256 dogs with stage B1 or B2 MMVD. Materials and Methods: Medical records of 256 dogs with preclinical MMVD were reviewed retrospectively. Long-term outcome was assessed by telephone interview. Dogs alive at the time of phone interview were asked to return to the hospital for re-evaluation of their cardiac status.Results: Seventy of 256 (27.3%) dogs died during the observation period. The median survival time, regardless of cause of death, was 588 (range 75-1,668) days. The presence of a murmur was associated with an increased risk of death (AHR 2.14; 95% CI 1.12, 4.11; P = 0.022). Thirty (12%) deaths were considered cardiac related. LA/Ao > 1.4 was the only negative predictor (AHR 2.64; 1.13, 6.13; P = 0.024) for cardiac-related deaths. Eighty-three dogs were reexamined, of which 34 progressed to a more advanced stage of MMVD. The presence of Emax > 1.2 (AHR 2.75; 95% CI 1.01, 7.48; P = 0.047) and cough (AHR 7.89; 95% CI 3.18, 20.07; P < 0.001) were significant in the multivariate analysis.Conclusions and Clinical Importance: Preclinical MMVD represents a relatively benign condition in dogs. Clinicians might find stratification of this dog population according to risk factors based on clinical and echocardiographic findings helpful in determining treatment.

Increased NT-proANP predicts risk of congestive heart failure in Cavalier King Charles spaniels with mitral regurgitation caused by myxomatous valve disease

“…3,46 In a meta-analysis of 256 dogs with MMVD, 42 heart rate was not among the variables associated with a progression of heart failure class or survival. In cross-sectional studies, heart rate variability 47 and mean heart rate 48 changed with progression of MR, but heart rate itself and increase in heart rate, as a predictors of CHF, have to date not been evaluated in longitudinal models (Fig.…”

“…These findings are in concordance with earlier reports. 30,42,45 Although both predictors were significant as baseline variables in the Cox model, the baseline analysis is biased because one study inclusion criterion was an audible heart murmur; thus, we know that these animals are at risk before inclusion. 2 …”

“…The weak significance of heart rate in the univariable baseline analysis (HR ¼ 1.21, p ¼ 0.03) is in agreement with the previous meta-analysis. 42 Some dogs entering our study had a low-grade murmur with no heart enlargement and the heart rate of these dogs was not expected to be increased, 48 as reflected in a low baseline hazard of all dogs included. On the other hand, in the longitudinal model, which analyzed the change in absolute heart rate for every individual, and specifically when this HR was split into intervals, a heart rate >130 was identified as a significant risk (Fig.…”

Historical review, epidemiology and natural history of degenerative mitral valve disease

“…The same study showed that 13% of dogs progressed to a more advanced stage of MMVD during the observation period. 54 Another recent study reported that 82% of pre-clinical dogs were still asymptomatic 12 months later. 55 Because the assessment of MMVD severity is not universally standardadized, reports on the natural history and prognosis of dogs with MMVD are somewhat variable.…”

Selected echocardiographic variables change more rapidly in dogs that die from myxomatous mitral valve disease

“…3 However, MMVD also has a variable natural history, with heterogeneity of the rate of disease progression. 7 We wished to examine whether dogs that went on to die of their heart disease would have a different rate of change of echocardiographic indices compared to a sample of dogs at various stages of their disease process. Assuming that death due to a non-cardiac disease process is just as likely to occur at any stage in the progression of mitral valve disease we could consider these dogs as representing a random cross section of dogs at various points in the progression of their valvular heart disease (albeit affected by a co-morbidity).…”