A12-week-old 6.2-kg (13.6-lb) female English Springer Spaniel was evaluated at the University of Missouri-Columbia Veterinary Medical Teaching Hospital because of suspected PDA. On physical examination, the dog was tachycardic (heart rate, 200 beats/min) and tachypneic (respiratory rate, 60 breaths/min); harsh lung sounds and hyperkinetic femoral pulses were detected. A grade 5/6 continuous heart murmur with the point of maximal intensity over the left heart base was auscultated. Thoracic radiography revealed a moderately large cardiac silhouette with a vertebral heart score of 12.5 (reference range, 8.5 to 10.6); a vertebral heart score is derived from measurements of the short and long axes of the heart in relation to vertebral bodies.1 Radiographically, pulmonary venous distension and a mild perihilar interstitial infiltrate were evident. These changes were consistent with left-sided congestive heart failure. Echocardiographic findings confirmed the diagnosis of PDA (left-to-right shunt). Continuouswave Doppler ultrasonography revealed that the peak velocity of systolic flow through the ductus was 5.82 m/s and end-diastolic flow velocity was 3.35 m/s. Mild mitral valve regurgitation was also present. Furosemide (2 mg/kg [0.91 mg/lb], PO, q 12 h) was administered for treatment of heart failure.
Two weeks later, the dog underwent coil occlusion of the PDA. Cefazolin (22 mg/kg [10 mg/lb], IV) was given at induction of anesthesia and every 90 minutes thereafter during the procedure. Once the dog was anesthetized, the ductus was approached percutaneously via the femoral artery. Results of angiography indicated that the ductus was 8 mm at its widest point and 4 mm at its narrowest point. The first coil deployed in the ductus embolized to the caudal lobe branch of the right pulmonary artery. Five additional coils were successfully placed into the ductus, and the coil mass protruded slightly into the pulmonary artery (Figure 1). Cefazolin (22 mg/kg, IV) was given every 6 hours for the first 24 hours after surgery, and then antimicrobial administration was discontinued.
Twenty-four hours after the procedure, echocardiography revealed mild residual flow through the ductus; the peak velocity of systolic flow was 2.80 m/s, and the amount of diastolic flow was negligible. The murmur was attenuated to a grade 2/6 left basilar systolic murmur. There was moderate bruising and mild swelling associated with the femoral puncture site. This was treated with warm packing for 2 weeks. The dog was discharged 1 day following the procedure.
One week after the procedure, the dog became anorexic and lethargic, began vomiting, and had a rectal temperature of 40.2°C (104.5°F). The swelling associated with the femoral puncture site had abated, but mild skin discoloration was still present. Abnormalities detected via CBC included mild normocytic, normochromic anemia (Hct, 33%; reference range, 37% to 55%), neutrophilia (11,660 cells/mL; reference range, 3,000 to 11,500 cells/mL) with a left shift (3,040 band neutrophils/mL; reference range, 0 to 300 bands/mL), and thrombocytopenia (14,200 platelets/mL; reference range, 200,000 to 500,000 platelets/mL). Toxic effects on neutrophils were detected on examination of a blood smear. No notable abnormalities were identified via serum biochemical analyses. A coagulation profile was obtained. Prothrombin time was prolonged (7.8 seconds; reference range, 5.4 to 7.4 seconds) and fibrin degradation products concentration was high (> 20 mg/mL; upper reference limit, < 5 mg/mL). The activated partial thromboplastin time was within reference limits. The result of a parvovirus antigen test was negative. Urinalysis revealed proteinuria (2+), and urine specific gravity was 1.044 (reference range,2 1.001 to 1.065), but no other abnormalities were identified. Bacteriologic culture of urine yielded negative results; however, Pasteurella multocida was cultured from 3 blood samples obtained aseptically from a jugular vein at 1-hour intervals. Radiographically, the vertebral heart score was 11.0, and there was no evidence of congestive heart failure. The position of the coil mass was unchanged. Echocardiographically, there were no important changes, compared with previous postoperative findings.
The dog was admitted to the intensive care unit for treatment of sepsis because the presumptive diagnosis was infection of the implanted coils. Treatment with ticarcillin-clavulanic acid (50 mg/kg [22.7 mg/lb], IV, q 6 h) was initiated along with IV fluid therapy. Clinical signs of sepsis resolved within 48 hours. The femoral puncture site appeared normal within 1 week. After 2 weeks, IV treatment with the antimicrobial drug combination was discontinued and the dog received amoxicillin-clavulanic acid orally (13.75 mg/kg [6.3 mg/lb], q 12 h). The leukogram and platelet count were within reference range 1 month after starting treatment with ticarcillin-clavulanic acid.
Six weeks after the initial evaluation of the dog because of sepsis (at a time when it was still receiving antimicrobials), it was examined because of signs of congestive heart failure. Physical examination revealed a 5/6 continuous heart murmur with the point of maximal intensity over the left heart base, harsh lung sounds, and tachypnea. Thoracic radiography revealed the presence of pulmonary interstitial infiltrates in the caudal and dorsal portions of the lungs, which was consistent with congestive heart failure, and partial migration of the coils into the pulmonary artery (Figure 2). The vertebral heart score was 12.0. Echocardiography revealed that the left ventricular diastolic and left atrial systolic dimensions had increased by approximately 30%, compared with findings after surgery. Flow through the ductus had increased; the peak velocity of systolic flow was 4.43 m/s, and the end-diastolic flow velocity was 2.43 m/s. Treatment with furosemide (3.3 mg/kg [1.5 mg/lb], PO, q 12 h) and enalapril (0.5 mg/kg [0.23 mg/lb], PO, q 12 h) was initiated.
Two months after signs of heart failure initially developed, the dog was taken to Michigan State University's Veterinary Teaching Hospital for removal of the coils and closure of the PDA. Briefly, the dog was anesthetized and prepared routinely for surgery. The left femoral and left carotid arteries were isolated in case cardiac bypass became necessary. A left lateral thoracotomy was performed, and the PDA was approached as if for routine ligation. The ductus was clamped at its intersection with the aorta by use of Satinsky clamps and at its intersection with the pulmonary artery by use of ductus clamps. The ductus was incised to expose the coils, which were located partially within the ductus and partially in the pulmonary artery. Attempts to remove the coils by use of tension initially failed because of multiple adhesions that had formed between the coils and endothelium. The coils were also held by the ductus clamps at the point where they had migrated into the pulmonary artery. Inflow occlusion was performed 6 times, which enabled the coils to be freed from the pulmonary artery. The shortest inflow occlusion time was 5 seconds, whereas the longest inflow occlusion time was 90 seconds. The coils were cut into pieces and dissected free of the endothelium. The coil in the right pulmonary artery was left in place because it was inaccessible via a left lateral approach. Moderate hemorrhage occurred during the procedure, necessitating transfusion with several units of blood. The entire ductus was excised. The aorta and pulmonary artery were closed by use of 4-0 polypropylene suture in a mattress pattern. A thoracic tube was placed, and routine closure was performed. The coils and ductus tissue were submitted for bacteriologic culture, which yielded no growth of aerobic or anaerobic bacteria. The dog was discharged from the hospital 36 hours after surgery; the owner was instructed to administer amoxicillin-clavulanic acid (13.75 mg/kg, PO, q 12 h for 6 weeks), enalapril (0.5 mg/kg, PO, q 12 h for 2 weeks), and meloxicam (0.1 mg/kg [0.045 mg/lb], PO, q 24 h for 10 days).
Although the coil that embolized to the pulmonary vasculature was left in place, the dog had remained free of clinical signs for > 9 months at the time of this report. Two months after surgical treatment of the PDA, the dog underwent ovariohysterectomy without complications. Except for treatment with antimicrobials for 10 days after the ovariohysterectomy, the dog did not receive other antimicrobials during the followup period.
Patent ductus arteriosus
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