Spironolactone added to standard therapy in canine MMVD heart failure — LIKELY

In dogs with congestive heart failure from myxomatous mitral valve disease on standard therapy, does adding spironolactone vs placebo reduce cardiac death and clinical deterioration?

Shelf #207 · gate-verified and approved by the developer

LIKELY: Adding spironolactone to conventional therapy reduces cardiac death, euthanasia and severe worsening in dogs with moderate-to-severe mitral regurgitation from myxomatous mitral valve disease. In the single claim-carrying trial — a double-blinded, randomised, placebo-controlled field study of 212 dogs in Europe — the primary composite endpoint was reached by 10.8% of spironolactone dogs versus 25.5% of controls (absolute difference 14.7 percentage points; hazard ratio 0.45, a 55% relative risk reduction; P = .017), and the risk of cardiac-related death or euthanasia was reduced by 69% in relative terms (HR 0.31; P = .0071; 6 of 102 dogs vs 22 of 110 on the record's event breakdown). The limits are real: roughly two-thirds of dogs in each group did not complete the study, and the composite leans partly on euthanasia and worsening judgements rather than death alone — a single strong trial, not a decisive one, so LIKELY rather than PROBABLE. Drafted Nov 10, 2026 (VetMed build, topic #207); all figures from abstracts fetched and verified at drafting.

Bernay 2010: composite cardiac endpoint 10.8% on spironolactone vs 25.5% on placebo (HR 0.45, P = .017)

Double-blinded, randomised, placebo-controlled field study (record's own abstract wording; indexed as Randomized Controlled Trial, Multicenter Study)

Who: Dogs: 221 dogs recruited in Europe between February 2003 and March 2005; 9 excluded from analysis, leaving 212 dogs with moderate to severe mitral regurgitation caused by myxomatous mitral valve disease (ISACHC classes II [n = 190] and III [n = 21]). Dogs were randomized to spironolactone (2 mg/kg once a day) or placebo in addition to conventional therapy (an angiotensin converting enzyme inhibitor, plus furosemide and digoxin if needed). The primary endpoint was a composite of cardiac-related death, euthanasia, or severe worsening of mitral regurgitation.

Result: The primary endpoint was reached by 11 of 102 dogs (10.8%) in the spironolactone group (6 deaths, 5 worsening) versus 28 of 110 (25.5%) in the control group (14 deaths, 8 euthanasia, 6 worsening) — an absolute difference of 14.7 percentage points. The risk of reaching the composite endpoint significantly decreased by 55% in relative terms (hazard ratio = 0.45; 95% confidence limits, 0.22–0.90; log rank test, P = .017). The risk of cardiac-related death or euthanasia was significantly reduced by 69% in relative terms (HR = 0.31; 95% CL, 0.13–0.76; P = .0071); on the record's event breakdown that is 6 of 102 spironolactone dogs versus 22 of 110 control dogs. The number of dogs not completing the study for cardiac and other miscellaneous reasons was similar in the spironolactone (67/102) and control (66/110) groups.

Watch out: Attrition is the big caveat: about two-thirds of each group did not complete the study, even though non-completion was balanced between groups. The composite endpoint includes euthanasia and severe worsening — decisions and judgements, not death alone — and most enrolled dogs were ISACHC class II, so the evidence is thinnest for advanced (class III) failure. Single trial; the class counts in the record (II n = 190, III n = 21) are quoted exactly as the record gives them.

Bernay F, Bland JM, Häggström J, Baduel L, Combes B, Lopez A, Kaltsatos V. Efficacy of spironolactone on survival in dogs with naturally occurring mitral regurgitation caused by myxomatous mitral valve disease. J Vet Intern Med. 2010;24(2):331-41. PMID: 20102506. Registry ID: none in the record. MeSH: Angiotensin-Converting Enzyme Inhibitors · Animals · Cardiotonic Agents · Digoxin · Diuretics · Dog Diseases · Dogs · Double-Blind Method · Drug Therapy, Combination · Female · Furosemide · Male · Mitral Valve Insufficiency · Proportional Hazards Models · Spironolactone

Synthesis: one blinded trial supports adding spironolactone — with heavy attrition on the record

Synthesis

Who: Synthesis of the card above: Bernay et al. 2010 (double-blinded, randomised, placebo-controlled field study; 212 dogs analysed with moderate-to-severe MMVD mitral regurgitation on conventional therapy, Europe).

Result: The direction and size of effect are consistent across the composite endpoint (HR 0.45; 10.8% vs 25.5% absolute) and its hardest component, cardiac-related death or euthanasia (HR 0.31; 6/102 vs 22/110), which is what carries this shelf to LIKELY on a cardiac-death claim. What keeps it from PROBABLE is the trial's own record: a single study in which roughly two-thirds of dogs in both arms did not complete, and a composite in which euthanasia and worsening judgements do much of the work alongside death.

Watch out: Background therapy in the trial was an ACE inhibitor with furosemide and digoxin if needed — the result is an add-on claim on that conventional base, not evidence for spironolactone as a stand-alone or first-line drug.

Synthesis of Bernay F et al. PMID: 20102506. Registry ID as on the individual card.

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