Whether the aldosterone antagonist spironolactone has beneficial survival effects in dogs with dilated cardiomyopathy (DCM) is not known. The primary objective of the study was to evaluate the effect of spironolactone, when added to conventional therapy, on survival time in Doberman pinschers with congestive heart failure (CHF) due to DCM.
Sixty-seven client-owned Doberman pinschers with CHF due to DCM.
The trial design was prospective, randomized, blinded, and placebo controlled. Dogs were randomized to receive 50-75 mg of spironolactone twice daily (n = 34) or a placebo (n = 33), in addition to standard CHF therapy. Follow-up visits were targeted every 1-6 weeks until endpoint. Quality-of-life questionnaire and physical examination were performed at every visit, while renal biochemistry, ECG, echocardiography, and thoracic radiography were reassessed as needed. The primary endpoint was time to cardiac death, defined as death or euthanasia from CHF or sudden death.
Median time to primary endpoint in the spironolactone group (183 days) was not statistically significantly different than that for the placebo group (124 days) (p = 0.254). The development of atrial fibrillation (AF) was significantly less frequent in the spironolactone group (n = 7) than the placebo group (n = 15, p = 0.037).
While median time to cardiac death in the spironolactone group was not statistically significantly different than that in the placebo group, adding spironolactone to conventional therapy resulted in reduced occurrence of AF.

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