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Dexter: 6-month-old male intact Miniature Dachshund

Please enjoy reading about one of our Cardiology Patients Dexter.

Dexter 6-month-old male intact Miniature Dachshund

Dexter presented to our cardiology service for evaluation of a continuous heart murmur, incidentally noted by his referring veterinarian during his vaccine appointment. On initial physical examination, a grade 5/6 left axillary continuous murmur was ausculted, often described as a “washing machine” murmur due to its characteristic sound. An echocardiogram was performed, which confirmed a left-to-right shunting patent ductus arteriosus (PDA), with mild left ventricular enlargement, mild to moderate systolic dysfunction, and mild left atrial enlargement.


Figure 1 PDA visualized on echocardiogram (left). Colour Doppler on right shows blood flow across PDA site.


The ductus arteriosus allows shunting of blood across the pulmonary artery to the aorta during fetal development, bypassing pulmonary circulation and preventing volume overload in developing lungs. Following birth, lung inflation and stimulation of the pulmonary circulation occurs. The increased blood flow into the pulmonary veins results in increasing left atrial pressures, which stimulates ductus closure. The ductus arteriosus usually closes within 24 hours of birth, preventing deoxygenated blood in the pulmonary trunk from entering the aorta. In patients with a PDA, the ductus arteriosus fails to close. The etiology is not fully understood in animals; however, is it hypothesized that hypoplasia of the smooth muscle of the ductus results in a failure of contraction.


Figure 2 Angiography of the PDA site, with contrast shunting from the aorta into the main pulmonary artery.


Left untreated, the left-to-right shunting results in systolic dysfunction, volume overload, arrhythmias, and congestive heart failure (65% within first year of age if uncorrected). Other complications include development of severe pulmonary hypertension resulting in reverse shunting (right-to-left), exercise intolerance, and cyanosis. A left-to-right PDA can be surgically ligated or corrected by minimally invasive device occlusion using an ACDO device (Amplatz® canine ductal occluder). The ACDO device is self-expanding nitinol wire mesh, with a flat disk to secure the device and an expanding waist to occlude the PDA. Success rates are similar for the procedures (94 vs 92% respectively), however lower complication rates are reported with minimally invasive techniques.


Figure 4 ACDO device being placed across the PDA site.


Dexter was taken to surgery for correction of his PDA, using a minimally invasive approach. An Introducer catheter was fed up the right femoral artery and into the aorta using fluoroscopic guidance. Angiography was performed to determine ductus size for placement of the occluding device. A guidewire was then fed across the PDA site into the pulmonary artery. The ACDO catheter sheath was fed across the PDA site, and the ACDO device was deployed using fluoroscopic visualization. The distal disc opens into the pulmonary artery, and further deployment of the device fills the PDA ostium with the waist of the occluder. The device placement was confirmed with fluoroscopy. The femoral artery was then ligated upon completion of the procedure.


Figure 3 ACDO device, actual size on left. Magnified on right



Figure 5 ACDO device circled in red. Image taken 12 hours post-occlusion.

Dexter’s ACDO device was visualized with echocardiogram the following morning, confirming no residual transductal flow. He was discharged to the care of his owners later that day and is now happily hiking mountains and enjoying being a puppy!

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