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Patent ductus arteriosus in cats | VETgirl Veterinary CE Podcasts

In this VETgirl online veterinary CE podcast, we review patent ductus arteriosus (PDA). Left-to right patent ductus arteriosus (PDA) is the most common congenital heart defect in dogs. PDA also occurs in cats but with much lower incidence. If PDA is left untreated, it results in left-sided volume cardiac overload, with a high incidence of congestive heart failure (CHF) within the first year of life. Definitive treatment usually carries a good prognosis and consists of attenuation of flow across the PDA by either surgical ligation (e.g., via thoracotomy) or placement of occlusion devices (e.g., such as coils, plugs or occluders) from within the vascular space via a transcatheter/transvascular approach. Both methods are highly successful in dogs, with transvascular methods preferred as they are less invasive and have a lower rate of major complications. So what about cats? Unfortunately, these approaches can both be more difficult in cats due to their small size. To date, minimal data exists in veterinary literature about correction of PDAs versus medical management in cats.

So, Hutton et al from UC Davis and Penn wanted to evaluate this. In the study called “Surgical and nonsurgical management of patent ductus arteriosus in cats: 28 cases (1991-2012)“, they retrospectively evaluated 28 cats that were diagnosed with PDA based on echocardiography. In this study, they found no breed or sex predilection. 65% of the cats were initially presented to their veterinarian for non-cardiac reasons (such as vaccination, neutering, etc) at the time of diagnosis with PDA, and did not have any overt clinical signs. 90% of the cats (19/21) had generalized cardiomegaly on radiographs. 26% of cats (6 of 23 cats) had more than one congenital cardiac detect identified on echocardiography.

15/17 cats that underwent attenuation had open surgical ligation performed, with a median age for surgical attenuation being 5 months (super small critically ill patients to anesthetize!). Of those having open surgical ligation performed, 4/15 experienced intraoperative complications, all related to hemorrhage (including 2 deaths). 3 out of the 15 cats experience post-operative laryngeal complications (paralysis or voice change) post-operatively. Other less common complications reported include fever (1) and  chylothorax (1).

Overall, follow up information was only available in 16 of 28 cats (57%), with 11/16 having had surgical ligation. There was no significant difference reported for surgical ligation versus medical management (most of the latter group receiving no treatment at all, with only 2 of the cats receiving either ACE inhibitors or loop diuretics).

So, what can we take from this VETgirl podcast? Results indicate that PDA is relatively uncommon in cats and the majority of cats do not have clinical signs (murmur detection only) at the time of diagnosis. One key point is that although no difference was seen in survival times between surgery and medical management (which involved no treatment in most cases), it is very possible, if not likely, that these results were skewed because of the very small number of cats in the medical management group for whom any follow-up was able to be obtained. Small sample size also prevented any real comparison of surgical ligation vs. transvascular attenuation.

So, before you recommend medical management of PDA in cats, keep in mind that the small sample size is a major flaw in this retrospective study. Note that the small sample size is the key factor in this study that makes us exercise caution in interpreting the outcome results in this study. The authors acknowledge this as well; that the reason that no difference was seen in outcome between surgical ligation and medical management is far more likely that minimal follow-up existed in the latter group (in other words, the medical group). There is no reason to think that cats whose PDAs are left untreated will fare better or the same as PDA undergoing definitive closure based on the well established physiology (and risk of CHF) of PDA across species. Where I DO think this study has some value is in identifying the clinical characteristics of cats presenting with PDA, confirmation that surgical ligation remains a highly effective method of closure (when non-complicated), and that intraoperative hemorrhage remains the greatest risk associated with surgical ligation. So when in doubt, consult with your local cardiologist, but a chance to cut is a chance to cure!

References:
1. Hutton JE, Steffey MA, Runge JR et al. Surgical and nonsurgical management of patent ductus arteriosus in cats: 28 cases (1991-2012).  J Am Vet Med Assoc 2015;247:278-285.

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