PDA

Case example

When the heart sounds like a machine

A 10 week-old, female Dalmatian was presented for a machinery cardiac murmur and chronic, transparent nasal discharge.

Radiographic findings

Left ventricular enlargement is characterized by an increased apicobasilar size of the cardiac silhouette and dorsal deviation of the thoracic trachea on the laterolateral image (image 1), as well as elongation of the cardiac silhouette on the ventrodorsal image at the 3 to 6 o’clock position. Left atrial enlargement is indicated by straightening of the caudodorsal cardiac contour on the laterolateral image (image 1) and a rounded increase in soft tissue opacity between the mainstem bronchi on the ventrodorsal image – also termed “double opacity sign” (image 2a). A large convexity is at the level of the left cranial aspect of the descending aorta on the ventrodorsal image in the region of the ductus arteriosus Botalli, characterizing a ductal aneurysm or “ductus bump” (image 2a). The pulmonary vasculature is moderately enlarged (image 2b).

On the follow-up images an occluder has been placed in the PDA lumen (image 3) and the cardiovascular changes are markedly decreased in severity.

Conclusions

  • Severe left cardiomegaly with evidence of pulmonary vascular congestion and a ductal aneurysm characterizes a Patent Ductus Arteriosus (PDA). There is no evidence of a reverse PDA and/or cardiac failure.

Learning points

  • A PDA causes increased flow from the descending aorta into the main pulmonary artery resulting in pulmonary volume overload and left atrial and ventricular dilatation. Chronic, turbulent flow and enlargement of the PDA can create a “ductus bump” on ventrodorsal radiographic images.
  • Echocardiography has been the imaging modality of choice for PDA characterization, but electrocardiography-gated CT angiography allows for a more detailed evaluation, 3D reconstructions and flow modeling, rendering surgical interventions.

More information

  • »Patent ductus arteriosus morphology, pathogenesis, types and treatment«
    — Buchanan et al., J Vet Cardiol 2001;3(1):7-16
  • »Patent Ductus Arteriosus in Dogs«
    — Broaddus et al., Compendium, vetlearn.com; September 2010
  • »Review of left-to-right shunting patent ductus arteriosus and short-term outcome in 98 dogs«
    — Van Israël et al., JSAP. 2002; 43(9); 395-400

Images courtesy of Pinebrook Animal Hospital, USA.

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