Background: Angiotensin-converting enzyme inhibitors (ACEIs) improve quality of life and extend the life span of dogs with naturally acquired ISACHC class II-III congestive heart failure (CHF). However, their effects on asymptomatic heart disease remain controversial.

Hypothesis: Benazepril (BNZ), an ACEI, could have beneficial effects at the asymptomatic stage of degenerative mitral valve disease (MVD).

Animals: Dogs with ISACHC class Ia MVD and moderate-to-severe mitral regurgitation (MR) assessed by the color Doppler mapping technique at entry (Day 0) were retrospectively included.

Methods: Dogs were assigned to the treated group (BNZ group) if they received BNZ (and no other cardiac medication) from Day 0 or to the untreated group (UT group) if they did not receive any cardioactive treatment until occurrence of CHF.

Results: A total of 141 dogs were included in the study, 66 in the BNZ group (dosage: 0.30 ± 0.13 mg/kg) and 75 in the UT group. In the population (n = 93) including all breeds except Cavalier (CKC) and King Charles Spaniels (KC), median survival time to all causes of death in the BNZ group (n = 34, 3.3 years) was significantly longer than in the UT group (n = 59, 1.9 years) as was time to cardiac event (P < .05). Conversely, no effect of the BNZ treatment was observed in the CKC and KC population.

Conclusions and Clinical Relevance: BNZ had beneficial effects in asymptomatic dogs other than CKC and KC affected by MVD with moderate-to-severe MR. Breed distribution should be taken into account for interpretation of clinical trials performed in dogs with cardiac disease.

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