Diagnosis of Pulmonary Arterio‐Venous Fistula and Persistent Left Cranial Vena Cava by 3‐Dimensional Computed Tomographic Reconstruction

Abstract

A 5-month-old, 20 kg, intact female, German Shepherd Dog was presented to the Veterinary Hospital of the University of Zurich for evaluation of severe panting, exercise intolerance, and cyanosis. On clinical examination, the dog was thin but bright, alert, and responsive. A grade 5/6 systolic heart murmur was detected with the point of maximum intensity over the cranial left thorax. The peripheral pulse was weak, mu-cous membranes were pink, and capillary refill time was 2 seconds. Noninvasive blood pressure measurement was normal. Arterial oxygen saturation measured by pulse oximetry (SpO 2) on the tongue was 100% while in lateral recumbency and breathing room air. Based on these findings, congenital ventricular outflow tract obstruction was suspected and thoracic radiographs and echocardi-ography were performed. On radiography, moderate right-sided and mild left-sided cardiomegaly were present. The pulmonary vasculature was smaller than normal, with the exception of an enlarged and tortuous pulmonary artery and vein in the right cranial lung lobe. Moderate widening of the mediastinum was identified on the ventrodorsal projection (Fig 1). The abnormal vasculature in the right cranial lung lobe was considered compatible with an arterio-venous (AV) fistula. Widening of the cranial mediastinum was attributed to the presence of the thymus gland. Two-dimensional echocardiographic a findings included severe right ventricular hypertrophy with flattening of the septum and severe dilatation of the right atrium. Severe valvular pulmonic stenosis with a maximal systolic blood flow velocity (v max) of 5.0 m/s, a perimembranous ventric-ular septal defect with left-to-right shunting (v max 1.8 m/s), and mild subaortic stenosis (v max 2.4 m/s) were diagnosed by color Doppler and spectral Doppler examination, respectively. Considering the normal SpO 2 at rest, the shunting fraction through the AV fistula was judged to be clinically irrelevant. Adequate oxygen delivery at rest but cyanosis with slight effort was thought to be caused by right-to-left shunting through the AV fistula and ventric-ular septal defect associated with exercise-induced changes in pulmonary and systemic arterial pressures, possibly combined with peripheral cyanosis associated with decrease cardiac output caused by severe valvular pulmonic stenosis. During catheterization of the left jugular vein for ballooning of the pulmonic stenosis, the catheter could not be advanced into the right atrium, and entered the great cardiac vein instead. For better orientation, angiography of this aberrant vessel was performed and revealed a persistent left cranial vena cava (PLCVC) and dilated coronary sinus (Fig 2). Uneventful catheterization of the right heart through the right femoral vein followed by successful balloon valvuloplasty led to a reduction in pulmonic v max to 3.7 m/s. After the procedure, the owners reported normal respiratory rate, improved exercise tolerance, and no reccurrence of cyanosis. On a follow-up examination 3 years later, the owner consented t...

Intrapulmonary arteriovenous anastomoses in dogs with severe Angiostrongylus vasorum infection: clinical, radiographic, and echocardiographic evaluation

“…The ability to recruit IPAVAs varies between individuals, and not all humans or dogs, healthy or diseased, are able to open IPAVAs [1,2,7,9]. These physiological anastomoses are not to be confused with macroscopic arteriovenous-fistula malformations, even though the consequences may be similar [10,11].…”

Recruitment of arteriovenous pulmonary shunts may attenuate the development of pulmonary hypertension in dogs experimentally infected with Angiostrongylus vasorum

“…12 Second, a shunt may occur through a macroscopic peripheral congenital pulmonary arteriovenous malformation. 13 ventilation-perfusion mismatch that occurs in poorly ventilated but well perfused lung areas resulting in poor oxygenation of blood passing through such areas. This occurs physiologically in ventral lung areas where alveoli collapse or pathologically with lung injury.…”

Imaging characteristics of persistent left cranial vena cava incidentally diagnosed with computed tomography in dogs

“…A genetic basis for PLCVC has been suggested in the German shepherd dog on the basis of breeding trials in dogs with concurrent persistent right aortic arch [14]. PLCVC has been diagnosed in various breeds of dogs including the German shepherd, Boston terrier, Irish setter, French bulldog, cocker spaniel, Brittany spaniel and Beagle [1,2,3, 9, 10, 23]. Similar to previous results, 1 case was identified with PLCVC in each of the German shepherd, English bulldog and Boston terrier breeds in the present study.…”

“…Echocardiography is a useful method to diagnose PLCVC by visualization of a dilated coronary sinus between the left atrium and pericardium at the level of the aorta [3, 4, 9]. Additionally, echocardiography allows examination of all the cardiac structures to detect any other congenital heart malformation.…”

“…In a report of transvenous pacemaker placement in a dog, initial echocardiography failed to identify a dilated coronary sinus, which was diagnosed incidentally during catheterization [3]. CT and magnetic resonance imaging have been used to diagnose PLCVC in humans and dogs [5, 9, 22]. In particular, multi-detector CT angiography has proved its value in the visualization of vessels for detection of venous anomalies.…”