Korean Journal of
Veterinary Service

Patent ductus arteriosus (PDA) is one of the most common congenital cardiac defects in dogs (Buchanan and Patterson, 2003). Closure of ductus arteriosus typically occurs within 48 hours to 1 month after birth (Broaddus and Tillson, 2010). In dogs with PDA, blood flows from the systemic circulation into the pulmonary circulation, resulting in volume overload in the pulmonary system and, eventually, left-sided congestive heart failure (CHF) (Broaddus and Tillson, 2010). This can lead to clinical signs that are similar to those of left-sided CHF, such as exercise intolerance, tachypnea, or cough (Broaddus and Tillson, 2010; Nelson and Couto, 2019). In diagnosis, cardiac auscultation is a useful tool to detect PDA (Buchanan, 2001). The presence of a continuous machinery murmur at the left base, often accompanied by a palpable precordial thrill, indicates the likelihood of PDA (Buchanan, 2001). Radiographs usually show left atrial enlargement and evidence of pulmonary overcirculation (Nelson and Couto, 2019). Echocardiography also reveals left atrial enlargement and dilation of the pulmonary trunk, and it may visualize the duct itself (Nelson and Couto, 2019). PDA can be treated with surgical ligation of the duct (Goodrich et al, 2007). However, transcatheter occlusion with devices, such as the Amplatz canine duct occlude (ACDO), coils, and vascular plugs, has become a popular procedure (Nguyenba and Tobias, 2007; Stauthammer et al, 2015).

Maltese, Pomeranians, Cocker Spaniels, Bichon Frisés, Yorkshire Terriers, Collies, and German Shepherd dogs (GSD) are known breeds with a hereditary predisposition to PDA (Broaddus and Tillson, 2010). In South Korea, the most popularly owned breeds are Maltese, Poodles, and Pomeranians. Therefore, PDA is commonly observed in these breeds (Kim et al, 2018). However, PDA in GSD is rarely seen, and there are no reports about treating PDA with ductal occlusion via transcatheterization in South Korea. This case report presents a GSD that had PDA and was successfully treated with vascular plug occlusion.

A 4-year-old, spayed female German Shepherd dog weighing 22.4 kg was referred to Chungnam National University Veterinary Medicine Teaching Hospital with the chief complaint of a cardiac murmur. A soft continuous murmur was detected at the left basilar region upon auscultation. A complete blood count and serum biochemistry examination showed no significant findings. In the thoracic radiographs (MDXP-40TG, Medien International Co., Gyeonggi-do, South Korea), slight bulging of the main pulmonary artery was observed in the ventrodorsal view. Additionally, the bulgings of the aorta and left atrium were observed from the right lateral view. The vertebral heart score was 10.2 v, which is within the normal range (Fig. 1). Echocardiography (GE vivid E90, GE Healthcare, Gyeonggi-do, South Korea) was conducted. In the right parasternal (RPS) long-axis 4-chamber view and left parasternal (LPS) apical 4-chamber view, no distinct degeneration or prolapse of the mitral valve, tricuspid valve, or aortic valve was found. In the RPS short-axis view at the level of the pulmonary trunk, the pulmonary artery-to-aorta ratio was approximately 0.95, showing no clear evidence of pulmonary artery enlargement. The M-mode indicated a left ventricular internal diameter at diastole, normalized for a body weight of 1.97 and a left atrium-to-aortic root ratio of 1.62, suggesting volume overload in the left heart. In the RPS short-axis view at the level of the pulmonary trunk, color Doppler imaging showed continuous turbulent flow directed from the main pulmonary artery towards the pulmonary valve. This pattern was observed consistently within the main pulmonary artery in the LPS cranial long-axis view (Fig. 2). Based on all the results, a diagnosis of PDA was made, and plans were established to treat it with transcatheter occlusion.

Figure 1. Thoracic radiography of the GSD with PDA. (A) Ventrodorsal view showing slight bulging of the main pulmonary artery. (Arrow) (B) Right lateral view showing bulgings of the aorta and the left atrium (Arrows). GSD, German Shepherd dog; PDA, patent ductus arteriosus.

Figure 2. Color Doppler imaging showing turbulent flow (arrow) from the aorta to main pulmonary artery in the LPS cranial long-axis view. LPS, left parasternal.

A computed tomography (CT) (Alexion Advance Edition Model TSX-034A, TOSHIBA, Tokyo, Japan) scan was conducted to obtain more precise measurements and assess the shape of the duct. CT imaging revealed a vessel extending from the descending aorta to the pulmonary trunk, suggestive of PDA. The entire length of the duct measured approximately 25 mm. At the proximal part adjacent to the descending aorta, the diameter was 8 mm, while the main body of the duct maintained a consistent diameter before abruptly narrowing towards the distal part at the pulmonary trunk, where its minimal ductal diameter (MDD) measured approximately 4 mm, indicating a type II A PDA (Fig. 3) (Miller et al, 2006).

Figure 3. CT images of the GSD with PDA. Image showing a vessel extending from the descending aorta to the pulmonary trunk, suggestive of PDA (arrow). CT, computed tomography; GSD, German Shepherd dog; PDA, patent ductus arteriosus.

To perform transcatheter occlusion, a vascular plug (K-easy PDA PLUG, S&G Biotech Inc., Gyeonggi-do, South Korea) (plug diameter, 8 mm; wire thickness, 0.090 mm; length, 10 mm) was prepared. The patient was placed in the right lateral recumbency after anesthesia, and the right femoral artery was exposed. The artery was atraumatically isolated for sole exposure, and black silk 1-0 was used to ligate the proximal and distal ends to facilitate vascular access. Femoral arterial access was achieved using the modified Seldinger’s technique after surgical isolation (Stern et al, 2020). Using the Micropuncture set (COMPACT Micropuncture set, JUNG SUNG MEDICAL, Seoul, Korea), an initial entry into the artery was made with a 21 G needle, and a 0.018” guidewire was inserted. Subsequently, the needle was removed, and the puncture site was dilated using 4 Fr and 5 Fr dilators. After placing the introducer sheath, the 0.018” guidewire was reinserted, advancing through the descending aorta, passing through the PDA, and reaching the main pulmonary artery. Then, the sheath was inserted to access the proximal descending aorta. After removing the guidewire, an angiographic syringe was used for manual injection of 1 ml/kg of iodinated contrast to reconfirm the size and location of the PDA. The delivery sheath tip was positioned in the main pulmonary artery, and the vascular plug was deployed, ensuring its fixation to the PDA before displacing it.

The murmur heard on auscultation disappeared immediately after the occlusion of the PDA. Following the removal of all devices, the femoral artery was sutured and cut down, followed by closure of the surgical site. Immediately after the intervention, the positioning of the vascular plug in the PDA was confirmed through thoracic radiography (Fig. 4). Echocardiography was performed again and no residual ductal flow was observed 24 hours after the interventional procedure. Also, the patient did not exhibit any complications.

Figure 4. Thoracic radiography after transcatheter occlusion of PDA (arrow). PDA, patent ductus arteriosus.

This is the case of successful treatment of PDA in a GSD using vascular a plug via transcatheterization.

The patient was referred due to the presence of a cardiac murmur. No other specific clinical signs were observed. Typically, dogs with PDA may present clinical signs similar to left-sided CHF. However, according to a study by Wesselowski et al. (2019), 50% of GSD did not exhibit clinical symptoms until presentation (Nelson and Couto, 2019). In the same study, symptomatic GSD exhibited lethargy, exercise intolerance, cough, and tachypnea (Wesselowski et al, 2019). PDA generates a volume overload in the pulmonary system because it creates a flow of blood from the higher-pressure systemic circulation to the relatively lower-pressure pulmonary circulation (Broaddus and Tillson, 2010). This causes dilation of the pulmonary arteries and veins as well as the left atrium and ventricle, creating left-sided overload leading to the onset of CHF clinical signs (Broaddus and Tillson, 2010). However, the manifestation of clinical signs depends on the size of the PDA; if the size is small, clinical signs may not be present (Broaddus and Tillson, 2010). Therefore, in South Korea, even if a GSD shows no signs of CHF, it is necessary to periodically conduct cardiac examinations, including auscultation and echocardiography to confirm the presence of PDA.

The patient was a spayed female. In the Wesselovski et al. study (2018), 57% of GSDs were female, and according to several studies, females have a higher likelihood of having PDA; however, the precise genetic transmission mechanism remains unclear (Bomassi et al, 2011; Saunders et al, 2014). Further studies on the genetic mechanism of PDA are necessary. Moreover, in previous studies, the likelihood of dogs with PDA also having concurrent congenital cardiac disease was 35.7% among GSDs, compared to an occurrence of 8.8% for dogs with PDA and congenital cardiac disease in general (Saunders et al, 2014; Wesselowski et al, 2019). The most frequently observed disease among them was subaortic stenosis (Wesselowski et al, 2019). In this patient, no other congenital cardiac diseases besides PDA were identified. Since the underlying mechanism or genetic predisposition for these co-occurrences remains unclear, further study is needed.

The median MDD in GSD is between 4.4∼4.9 mm (range, 1.6∼9.2 mm), which is generally larger compared to other dog breeds (Wesselowski et al, 2019). However, according to the study by Nguyenba and Tobias, (2007), using an ACDO device with a waist diameter twice the size of the MDD resulted in successful procedural outcomes (Wesselowski et al, 2019). The MDD in this patient was 4 mm. The device used in this patient was a new device, K-easy PDA PLUG, which is offered in three sizes based on disc diameter (6 mm, 8 mm, and 10 mm). The vascular plug (K-easy PDA PLUG), developed in South Korea, is approximately half the price compared to the commonly used ACDO. Therefore, it is may be more accessible when treating PDA. Considering the patient’s PDA with an MDD of 4 mm and a proximal portion diameter of 7 mm, an 8-mm disc diameter device was selected and resulted in a successful outcome. Further research on selecting the device in GSD is needed.

In the Wesselowski et al. study (2019), 17 out of 21 GSDs were found to have type II A PDA. According to a study by Miller et al. (2006), type II A accounted for 54.5% of dogs with PDA. Type II A PDA demonstrates an abrupt and dramatic distal narrowing, representing 50% or more of the ductal diameter, while the proximal portion of the ductus maintains constant (Miller et al, 2006). This patient exhibited a similar shape and was diagnosed with type II A PDA. Type II A PDAs typically respond well to transcatheter occlusion using ACDO or vascular plug; thus, the patient underwent the procedure (Nguyenba and Tobias, 2007; Hulsman et al, 2021).

As GSDs are relatively less common compared to small breed dogs in South Korea, identifying PDA in GSDs may also be challenging. However, considering that GSDs are predisposed to PDA, it is crucial to periodically assess the presence of PDA through auscultation and echocardiography, even in the absence of clinical signs. If PDA is detected, transcatheter occlusion using a vascular plug can be performed for treatment, yielding favorable outcomes. To the authors’ knowledge, this is the first case report of PDA occlusion in GSD and also of using a vascular plug (K-easy PDA PLUG) in South Korea.

No potential conflict of interest relevant to this article was reported.