Objectives: To retrospectively assess the long-term outcome for dogs that were presented with collapse, syncope or exercise intolerance for which an underlying cause is not identified.
Methods: The clinical records of animals presenting to two practices were assessed. Dogs which presented for collapse, syncope or exercise intolerance at least 6 months previously and did not receive a definitive diagnosis despite investigation were included. Follow-up of these cases was carried out by conducting telephone interviews with the owners.
Results: One hundred and fifty-three cases were successfully followed up. Clinical signs had resolved in 64 cases (42%), 35 dogs (23%) were continuing to exhibit clinical signs, although 22 of these had improved without medical intervention. In 17 cases (11%), a diagnosis had subsequently been made or treatment was being administered and 37 dogs (24%) had died. Of the deaths, 18 (12%) were considered to be related to the original presentation. The overall prevalence of death and deterioration related to the problems investigated was 16·2% of cases. Death in boxers was significantly more common than in other breeds (36%).
Clinical Significance: Death and deterioration are uncommon outcomes for dogs other than boxers presenting with collapse, syncope and exercise intolerance for which a definitive diagnosis cannot be made.