Abstract
The aim of this work was to retrospectively evaluate the influence of different therapeutic protocols (loop diuretics, ACE-inhibitors, spironolactone +/- pimobendan) on the survival time (ST) of dogs with myxomatous mitral valve disease at different stages using an Inverse Probability Weighting (IPW) analysis. An IPW method was used to minimize confounding and IPW weighted time-repeated logistic model was used to approximate survival curves (SCs) and calculate survival differences. Subjects were allocated into cases (CA) and controls (CO). Dogs in American College of Veterinary Internal Medicine (ACVIM) B2 class treated with pimobendan (+/- ACE-inhibitors) were selected for the CA group, as well as symptomatic patients (ACVIM class C) threated with triple (furosemide, ACE-inhibitor, pimobendan) or quadruple (furosemide, ACE-inhibitor, pimobendan and spironolactone) therapy. The CO group included ACVIM class B2 dogs not treated with any medication and ACVIM C dogs treated with a combination of furosemide and ACE-inhibitor/spironolactone without pimobendan.The SC of the CA group crossed the CO group at 1634 days. The difference between the two SCs at the time of maximum survival difference in favour of the CO group was 11.3% (CI 1.7%–20.9%) (significant), in favour of the CA group was 3.9% (CI -8.6%–16.4%) (not significant) and at the mean ST was 3.6% (CI -8.5%–15.7%) (not significant) in favour of the CA group. For times greater than 1634 days the survival was in favour of the CA group, there were no statistically significant differences in survival in favour of the CA group in this clinical population.
Database development and survival analysis in a clinical and historical cohort of dogs affected by myxomatous mitral valve disease treated or not with pimobendan using causal inference techniques
