TDK conference 2019

Background: Published data of incidence of reflex bradycardia (Branham sign) following surgical closure of patent ductus arteriosus (PDA) is very limited.

Objective: Our goal was to find a correlation between clinical data of dogs undergoing PDA ligation hypothesising that (1) younger dogs are less likely to suffer from reflex bradycardia over the course of 10 minutes after complete ligation of PDA, and (2) younger dogs undergo more pronounced left atrial remodelling after surgery.

Animals: Twenty-one referred dogs.

Materials and methods: Prospective analysis of clinical data of 21 referred cases with PDA. Outcome was determined by contacting owners and referring veterinarians as well as cardiologists performing the post-surgical echocardiography. All dog owners were asked to do a control echocardiography four weeks post-surgery.

Results: Anaesthesiologic data of changes in heart rate during the surgery could be assessed in thirteen cases, of which five animals showed an immediate drop in heart rate after the ligation. By logistic regression there was no found significant association between the age and Branham sign (p= 0.749). For the bodyweight the result is similar (p=0.340). Based on the sex ratio (6 male and 7 female) males had the sign with 9 times higher odds than females, but the result was statistically not significant (p=0.1026). Regarding the cardiac remodelling, the data could be retrieved from 12 patients. It shows a direct relation between the age of the animal and the increased Left Atrium/Aorta value (LA/Ao) postoperatively. In other words, one-month increase of age increases the post-surgical LA/Ao value by 0.0015 mm comparing to the presurgical value (p=0.8238). Another finding was that 1.0 kg increase of body weight decreases postsurgical LA/Ao value by 0.0088 mm comparing to the presurgical value (p=0 .43777).

Conclusion: The collected data rejected our first hypothesis, as there appeared to be no correlation between the age and occurrence of reflex bradycardia following the closure of a PDA. Our second hypothesis was confirmed, showing that younger animals in our study appeared to have faster remodelling compared to older ones. Interestingly, large breed dogs seemed to benefit more as an increase in bodyweight was accompanied by a decrease in LA/Ao ratio after the ligation of the PDA.

Clinical importance: We could not see any association between the age and the appearance of a positive Branham sign. As for the cardiac remodelling, one might suspect that younger animals benefit from their overall increased healing capacity also in case of a distended left atrium.