Partial Anomalous Pulmonary Venous Connection in 2 Miniature Schnauzers

A 3-year-old, 6.0 kg, intact female Miniature Schnauzer was presented to Azabu University for evaluation of right heart enlargement, incidentally noticed on survey thoracic radiographs. The dog was asymptomatic and no abnormalities were identified on physical examination. Radiographic evaluation of the thorax indicated right heart enlargement (vertebral heart score, 12.1). Two-dimensional echocardiography disclosed right atrial and right ventricular dilatation (Fig 1). An abnormal vascular structure connected to the right atrium at the heart base was observed on color Doppler echocardiography (Fig 2). No other structural heart disease or conditions that could result in right heart dilatation (eg, pulmonary hypertension, atrial septal defect [ASD], tricuspid valve regurgitation) were found. A complete blood count (CBC) and serum biochemistry profile were within normal limits. D-dimer concentration (reference range, <0.2 lg/mL) was normal. Computed tomography angiography (CTA) and cardiac catheterization were performed under general anesthesia, maintained by fentanyl constant rate infusion and isoflurane inhalation, to determine a definitive diagnosis. A 4 Fr multipurpose catheter was introduced from the right jugular vein through a catheter introducer placed by the Seldinger technique. Oxygen saturation (SaO2) of each site within the heart was measured while breathing room air. Mean SaO2 of the cranial and caudal vena cava was 55.9%. SaO2 in the right atrium varied from 81.8 to 99.2%, depending on the location of the catheter tip. SaO2 at the right ventricle and pulmonary artery were 77.0 and 83.2%, respectively. Mean right atrial and pulmonary pressures were 1 and 11 mmHg, respectively. The dog was placed in dorsal recumbency on a clinical 16-multi-detector-row computed tomography scanner. Iodinated contrast medium (2 mg/kg) was rapidly injected via the cephalic vein. Repetitive transverse plane cine scans (120 kV, 99 mAs, 0.625 mm slice thickness, 0.6 s tube rotation time, 0.938 helical pitch) were acquired over the heart. Images were transferred to an image software system for further evaluation. Acquired images were analyzed using multiplanar reconstruction and volume rendering, and it was determined that the pulmonary vein of the right cranial lung lobe was connected to the right atrium. Therefore, a definitive diagnosis of partial anomalous pulmonary venous connection (PAPVC) was made (Fig 3).