Transarterial ductal occlusion with the Amplatzer vascular plug in 31 dogs

Background: Transarterial ductal occlusion with the Amplatzer vascular plug was first reported in dogs by Hogan et al in 2005. Hypothesis: Use of the Amplatzer vascular plug is a safe, efficacious method of patent ductus arteriosus (PDA) occlusion. Animals: Thirty‐one client‐owned dogs with PDA. Methods: Records of 31 dogs in which transarterial occlusion of PDA with an Amplatzer vascular plug was attempted were reviewed. Results: All dogs had a type II PDA, with 27 dogs having type IIA morphology and 4 dogs having type IIB morphology. Appropriate device deployment was achieved in 29 of 31 dogs. Postdeployment angiography in 21 dogs documented complete occlusion in 10 dogs, trivial residual flow in 5 dogs, mild residual flow in 2 dogs, moderate residual flow in 3 dogs, and severe residual flow in 1 dog. Transthoracic color Doppler echocardiography documented complete occlusion in 22 dogs, whereas 2 dogs had trivial residual flow, 2 dogs had mild residual flow, 2 dogs had mild to moderate residual flow, and 1 dog had severe residual flow. Of the 7 dogs with residual flow, 2 had complete occlusion 2–4 months postoperatively, 1 had moderate residual flow 1 month postoperatively, and 4 were lost to follow‐up. One dog required a larger device than was able to be deployed through the largest sheath placed in the femoral artery. Pulmonary embolization of the device occurred in 1 dog. Conclusion: We conclude that ductal occlusion with an Amplatzer vascular plug is a safe and efficacious therapy for PDA in dogs.     

Unilateral shunt formation with thoracic aortic dissection in a whippet

A three‐year‐old neutered male whippet was presented with intermittent, exercise‐induced paraparesis. Femoral pulses were bilaterally absent. Neurologic examination was suggestive of a thoracolumbar myelopathy. Blood pressure measurements revealed hypotension in both pelvic limbs, hypertension in the right thoracic limb and it was immeasurable in the left thoracic limb. Echocardiography was within reference limits. A clear vascular pulsation was palpable on the right ventral abdominal wall. Computed tomographic angiography revealed a dissection of the aortic wall between the left subclavian artery and the brachiocephalic trunk with subsequent thrombus formation. A shunt between the right internal thoracic, cranial and caudal epigastric arteries to preserve blood flow to the pelvic limbs was visualized. Necropsy was declined by the owner. This is the first case report describing the formation of a unilateral vascular shunt following a thoracic aortic occlusion, which presented as exercise‐induced paraparesis .     

Collateral vessel development after chronic bilateral common carotid artery occlusion in the dog

The functional response to occlusion of arteries supplying the head has been found to be much less severe in th dog than in man, indicating that a more significant collateral development occurs in the dog. To document the anatomic response to chronic occlusion of vessels supplying the head, patterns of collateral vessel growth and development were studied by corrosion casting in adult mongrel dogs 8 weeks after bilateral ligation of the common carotid artery. Dissection of the casts revealed two consistent and bilateral anastomotic connections: (i) internal carotid artery to maxillary artery (anastomotic artery) and (ii) internal carotid artery to ascending pharyngeal artery. Also present in all of the casts was a connection between one common carotid artery and both vertebral arteries, which has been designated as the deep collateral vessel. Significant collateral connections did not occur between the orbital vessels or between analogous vessels of the right and the left sides.     

Evaluation of the Cranial Rectus Abdominus Muscle Pedicle Flap as a Blood Supply for the Caudal Superficial Epigastric Skin Flap in Dogs

This study evaluates the cranial rectus abdominus muscle pedicle flap as the sole blood supply for the caudal superficial epigastric skin flap. This flap was composed of a cranially based rectus abdominus muscle pedicle flap that was attached to the caudal superficial epigastric island skin flap (including mammary glands 2 to 5) via the pudendoepigastric trunk. Selective angiography of the cranial epigastric artery in eight cadaver dogs proved that the arterial vasculature in the cranial rectus abdominus was contiguous with that in the caudal superficial epigastric skin flap. In the live dog study, three of six of the flaps failed because of venous insufficiency. Necrosis of mammary gland 2 occurred in two of six flaps. One of six flaps survived with the exception of the cranial most aspect of mammary gland 2. Angiography of the cranial epigastric artery proved that arterial blood supply to these flaps was intact. Histological evaluation of the failed flaps showed full-thickness necrosis of the skin and subcutaneous tissues, the presence of severe congestion, and venous thrombosis. Retrograde venous blood flow through the flap was inconsistent, and hence resulted in failure of this myocutaneous flap. Use of this flap for clinical wound reconstruction cannot be recommended.     

Occlusion of the internal carotid artery by means of microcoils for preventing epistaxis caused by guttural pouch mycosis in horses.

Occlusion of the internal carotid artery by insertion of intravascular platinum microcoils for guttural pouch mycosis was experimentally evaluated in 9 healthy adult Thoroughbred horses. The internal carotid artery was ligated to its origin, and an arteriotomy was made distal to the ligature, which was then occluded by insertion of the microcoil approximately 13 cm distal to its origin. Cessation of blood flow was determined visually and by angiography at the arteriotomy site. Six horses were evaluated for complication clinically and by endoscopy after surgery. One horse was necropsied after 30 days of surgery for histological evaluation of artery thrombus formation. In the other 3 horses, the blood flow of the right internal carotid artery was monitored, before and after microcoil occlusion of the left internal carotid artery. One or 2 microcoils stopped blood flow within a few minutes. No other abnormal findings were observed clinically. Thrombus was observed in the occluded segment of 1 horse 30 days after insertion; but no abnormalities were detected. The blood flow in the right internal carotid artery increased by approximately 28-58% after occlusion of the left internal carotid artery. This microcoil vascular occlusion technique causes an effective thrombosis, and based on experimental studies and clinical application in 2 horses with epistaxis due to guttural pouch mycosis, this technique would appear to be safe and efficacious.     

Evaluation of the characteristics of venous occlusion after placement of an ameroid constrictor in dogs

OBJECTIVES: To evaluate the mechanism of vascular occlusion after placement of an ameroid constrictor (AC) on a large intra-abdominal vein and document changes in blood flow. STUDY DESIGN: Experimental study. ANIMALS: Six adult dogs. METHODS: Six 6.5 mm ACs were digitally scanned to measure area and circumference of the ameroid and inner lumen before surgery. ACs were surgically positioned around the left common iliac vein (CIV) in each dog. Peri-vascular ultrasonic flow probes were positioned on the left CIV cranial to the AC, and on the right CIV as an internal control. Blood flow measurements were recorded daily until there was no, or prolonged minimal, blood flow, at which time the dogs were euthanatized. Left and right CIVs were removed for histologic evaluation, and the ACs re-scanned to evaluate degree and direction of expansion of the ameroid. RESULTS: Reduction in blood flow occurred within 10 days in all dogs. Three dogs had complete occlusion by day 10 from thrombus formation. One dog damaged the flow probes at 13 days when blood flow was approximately 50% of intra-operative values; the dog was euthanatized at 37 days; there was partial occlusion from thrombosis. Two dogs had persistent low blood flow and occlusion from thrombus formation when euthanatized at 59 and 98 days. There was a significant increase in total AC area and outer circumference, and decrease in luminal area and inner circumference when presurgical and postocclusion measurements were compared. CONCLUSIONS: Vascular occlusion after placement of an AC on a large intra-abdominal vein occurred from thrombus formation. CLINICAL RELEVANCE: A similar pattern of venous occlusion may occur after placement of an AC on a portosystemic shunt, which may lead to both short- and long-term complications associated with portal hypertension.     

Collateral vessel development, following unilateral chronic carotid occlusion in the dog.

Because much of the data base describing the physiology of cerebral circulation is based on experiments using the dog as a model and because the functional response to occlusion of arteries supplying the head have been shown to be different in man than in dogs, it is important that the growth and development of the extracerebral collateral circulation in dogs be documented. Using the techniques of corrosion casting, collateral vessel development was evaluated in adult mixed-breed dogs, following 4- and 8-week periods of unilateral ligation of the common carotid artery or the external carotid artery. Neurologic deficits or severe ischemia was not observed in any of the dogs during the postoperative period. Extensive collateralization occurred between the ipsilateral vertebral artery, regardless of the occlusion site. In addition, numerous collateral connections developed between the same vessel from the contralateral side. Two main patterns of collateral vessel organization consistently developed. Initially, a collateral network of highly tortuous superficial vessels predominated. With longer survival times after occlusion, deeper and more uniform-diameter direct-collateral vessels developed.     

Hybrid technique for ventricular septal defect closure in a dog using an Amplatzer® Duct Occluder II

A left-to-right shunting muscular ventricular septal defect (VSD) was diagnosed in a 4-month-old, female, 1.8 kg Bichon Frise – poodle mix dog. Echocardiographic evidence of cardiac remodeling, calculated pulmonary blood flow (Qp) to systemic blood flow (Qs) ratio of 2.8, and radiographic evidence of pulmonary edema supported the diagnosis of a hemodynamically important VSD. Using a combination of surgery and interventional catheter-based techniques to approach the VSD through the right ventricle, the VSD was occluded with an Amplatzer^® Duct Occluder (ADO) II device. The ADO II is a low profile, flexible device originally developed for patent ductus arteriosus closure in humans that has been used to close muscular and perimembranous VSD in children. This report describes the hybrid procedure and imaging that was essential for successful occlusion of the VSD in this dog.     

COMPUTED TOMOGRAPHIC CHARACTERISTICS OF COLLATERAL VENOUS PATHWAYS IN DOGS WITH CAUDAL VENA CAVA OBSTRUCTION

Collateral venous pathways develop in dogs with obstruction or increased blood flow resistance at any level of the caudal vena cava in order to maintain venous drainage to the right atrium. The purpose of this retrospective study was to describe the sites, causes of obstruction, and configurations of venous collateral pathways for a group of dogs with caudal vena cava obstruction. Computed tomography databases from two veterinary hospitals were searched for dogs with a diagnosis of caudal vena cava obstruction and multidetector row computed tomographic angiographic (CTA) scans that included the entire caudal vena cava. Images for each included dog were retrieved and collateral venous pathways were characterized using image postprocessing and a classification system previously reported for humans. A total of nine dogs met inclusion criteria and four major collateral venous pathways were identified: deep (n = 2), portal (n = 2), intermediate (n = 7), and superficial (n = 5). More than one collateral venous pathway was present in 5 dogs. An alternative pathway consisting of renal subcapsular collateral veins, arising mainly from the caudal pole of both kidneys, was found in three dogs. In conclusion, findings indicated that collateral venous pathway patterns similar to those described in humans are also present in dogs with caudal vena cava obstruction. These collateral pathways need to be distinguished from other vascular anomalies in dogs. Postprocessing of multidetector‐row CTA images allowed delineation of the course of these complicated venous pathways and may be a helpful adjunct for treatment planning in future cases.     

Intracaval Repair of a Persistent Ductus Venosus in a Dog

A persistent ductus venosus was diagnosed in a 4-month-old Old English sheepdog. Total occlusion of blood flow to the liver was achieved through heparinization, hepatic artery occlusion, and placement of bypass cannulas from the portal vein and caudal vena cava to the right atrium. Intracaval closure of the ductus venosus then was accomplished. Despite postoperative complications of continued hemorrhage and acute renal uremia, the animal recovered. The neurologic abnormalities exhibited before surgery resolved, and the dog became more active and gained weight. The dog died due to undetermined causes three months after surgery. The ductus venosus was found to be closed, and the liver was markedly increased in size at necropsy.     

Repair of a canine forelimb skin deficit by microvascular transfer of a caudal superficial epigastric flap

Extensive skin loss from the forelimb of a Border collie was repaired by a microvascular caudal superficial epigastric flap, with secondary meshing of the flap to increase coverage. The caudal superficial epigastric artery and vein were anastomosed to the brachial artery and vein. End-to-end anastomosis to the brachial artery and vein did not compromise peripheral blood flow, and no flap necrosis was observed after subsequent limited meshing of the flap.     

The effect of carotid artery occlusion on lingual arterial blood pressure in dogs.

Although temporary occlusion of the carotid arteries is commonly done to reduce blood loss during nasal surgery in the dog, data supporting its use are mostly anecdotal and subjective. Twelve dogs were placed under general inhalation anesthesia and mechanically ventilated to maintain normocapnea and an end-tidal halothane concentration equivalent to 1.3 times the minimum alveolar concentration. Tourniquets were placed around both carotid arteries of each dog. Both lingual arteries were cannulated in each dog and their heart rate and blood pressure were measured bilaterally. During unilateral carotid artery occlusion, the blood pressures in the ipsilateral lingual artery were significantly (P < 0.05) lower than the preocclusion control pressures and pressures recorded in the contralateral vessel. Bilateral carotid artery occlusion resulted in a further significant (P < 0.05) fall in all lingual arterial pressures. The recorded heart rates only varied significantly from preocclusion control values when they increased during bilateral carotid occlusion (P < 0.05). The results of this study confirm that carotid artery occlusion has the potential to reduce intraoperative blood loss during oronasal surgery in the dog.     

Use of laser Doppler flowmetry to determine blood flow in and viability of island axial pattern skin flaps in rabbits

Perfusion and viability of island axial pattern skin flaps were tested in 37 healthy New Zealand white rabbits, using laser Doppler monitoring of blood flow in the capillary loops and the subpapillary plexus of the dermis. Skin flaps, selected on the basis of the caudal superficial epigastric vein and artery, were lifted and replaced in their original locus after selective occlusion of their vascular pedicles. Subjects were allotted into groups: control group (n = 10); arterial occlusion (n = 7); venous occlusion (n = 10); and arterial and venous occlusion (n = 10). The rabbits were monitored from 48 hours before surgery until euthanasia 48 to 72 hours after replacement of the flap. Flap viability was assessed on a clinical basis, using a comparative scoring method based on a numeric scale. The degree of necrosis in histologic sections was evaluated, using a scoring system. Laser Doppler measurements were obtained on 3 consecutive days before surgery, to establish the normal basal blood flow in the skin. Postsurgical measurements were obtained at 2-hour intervals for the first 8 hours and at 24, 48, and 72 hours after surgery. Measurements of basal blood flow varied significantly (P less than 0.05) from site to site on the surface of individual flaps and over time. When laser Doppler flowmetric (LDF) measurements from 6 sites on a flap were used as a measure of laser Doppler flow for the total flap, there was no significant difference between contralateral flap areas outlined on the abdomen of the rabbits. Temporal variations over 3 days for each rabbit or among rabbits were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)     

ULTRASONOGRAPHY OF THE FEMORAL ARTERY IN SIX NORMAL HORSES AND THREE HORSES WITH THROMBOSIS

Ultrasonography of the femoral artery in the horse, including color, power and spectral Doppler, provides morphologic and dynamic information. This paper describes the use of the techniques in six clinically normal horses and three with femoral artery thrombosis. Useful landmarks for orientation are the saphenous artery and the medial saphenous vein. The lateral circumflex femoral artery can not be visualized. Recognition of the genus descendens artery is complicated due to the presence of multiple distal caudal femoral arteries. The femoral artery feeds a high resistance bed. In normal horses the peak systolic velocity varies between 50–90 cm/sec. Echoic tissue in the femoral artery lumen with stenosis, occlusion and collateral blood flow formation are features encountered in the patients.     

Caudal vena cava obstruction caused by redundant pacemaker lead in a dog

Inferior vena cava obstruction, a rare but serious complication of transvenous pacemaker lead placement in humans, has not been reported in dogs. We describe this complication in a dog that developed ascites 8 months after pacemaker implantation. Radiography disclosed a loop of redundant lead within the caudal vena cava (CVC), and angiography demonstrated obstruction to blood flow. Withdrawal of the loop from the CVC did not restore blood flow. Persistent obstruction was suspected secondary to fibrosis resulting from vascular damage caused by the loop of lead. Angioplasty of the CVC obstruction restored blood flow and resolved the dog's clinical signs.     

Closure of a persistent ductus arteriosus of Botallo in two dogs using transarterial coil embolization

Non-surgical occlusion of persistent ductus arteriosus (PDA) by catheter guided coil embolisation was performed in two dogs. In both dogs the procedure was performed through the femoral artery. The exact location and the narrowest diameter of the PDA were evaluated angiographically after contrast medium injection into the ascending aorta. Based on shunt diameter measurements of 4 mm in dog no. 1 and 2.4 mm in dog no. 2, a coil of 8 mm diameter was chosen for dog no. 1, and of 5 mm diameter for dog no. 2. The coils were placed within the shunt vessel under fluoroscopic guidance using the Cook delivery-system for detachable PDA coil. The success of the intervention was documented angiographically 10 minutes after coil release. The shunt vessel was completely occluded in dog no. 1, while minimal blood flow was detected in dog no. 2 at that time. The technique of transvascular PDA closure compares favorably with the traditional surgical technique due to minimal invasiveness and hence excellent postinterventional comfort to the patient.     

Hepatic arteriovenous fistulae and portal vein hypoplasia in a Labrador retriever

An 18-month-old male Labrador retriever was referred for investigation of chronic intermittent diarrhoea and vomiting of two months duration. A diagnosis of hepatic arteriovenous fistulae was made. These are extremely rare hepatic vascular anomalies which confer arterial pressure to the portal vein. Liver atrophy, portal vein hypoplasia, portal hypertension and multiple acquired portosystemic collateral vessels are the main complications. Surgical excision is a challenge as resection of large lesions may be associated with significant blood loss. In this dog, persistence of portal vein hypoplasia and extensive collateral pathways following surgery led to a reserved prognosis.     

Use of a flow-mediated vasodilation technique to assess endothelial function in dogs

OBJECTIVE: To develop and assess the reproducibility of a protocol to noninvasively test endothelial function in dogs on the basis of the flow-mediated vasodilation (FMD) procedure used in humans. ANIMALS: 5 healthy spayed female dogs. PROCEDURES: Luminal arterial diameter and blood flow velocity in the brachial and femoral arteries were measured with ultrasonography. The within-dog reproducibility of these ultrasonographic measurements was tested. An occlusion period of 1, 3, or 5 minutes with an inflatable cuff was used to create the FMD response. Measurements made at 15, 30, and 60 seconds following release of the occlusion were compared with measurements made immediately prior to each occlusion to assess the FMD response. RESULTS: Within-dog reproducibility of measurements revealed moderate to high correlations. Change from baseline in luminal arterial diameter was most substantial when measured at 30 seconds following release of occlusion, whereas blood flow velocity changes were maximal when measured at 15 seconds following release. The brachial imaging site provided a larger number of significant FMD responses than the femoral site. The 3-minute occlusion period provided equal or better responses than the 5-minute occlusion period. CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasonographic measurement of the FMD responses was a feasible and reproducible technique and significant changes from baseline were detected. The FMD responses in dogs were most substantial when performed at the brachial artery with blood flow velocity and luminal arterial diameter changes from baseline measured at 15 and 30 seconds, respectively, following release of a 3-minute occlusion period.     

Coil embolization of patent ductus arteriosus via the carotid artery in seven dogs

This study was designed to evaluate the feasibility and limitations of transcatheter embolization coil occlusion of patent ductus arteriosus in dogs using a carotid artery approach. Seven dogs examined at the University of California, Davis Veterinary Medical Teaching Hospital in 2002-2003 for evaluation of heart disease had congenital patent ductus arteriosus diagnosed by characteristic physical, electrocardiographic, radiographic, and anatomic and Doppler echocardiographic findings. Dogs were anesthetized for transesophageal echocardiography and transcatheter coil embolization of the ductus via the right external carotid artery. Coil embolization was achieved in all seven cases, using one to four detachable embolization coils. There were no major complications. Minor complications occurred in two dogs (additional coils placed using a femoral arterial approach and coil embolization of a left femoral artery branch). One dog was examined only 24 h post-operatively and had no murmur and trivial residual ductal flow by Doppler echocardiography. The other 6 dogs were clinically healthy when examined up to three years post-intervention. One dog had a very soft continuous murmur and mild residual ductal flow; the other five had no audible continuous murmur, with only one dog having trivial residual ductal flow identified by Doppler echocardiography. Although technically challenging, coil embolization via the carotid artery is a viable alternative approach for transcatheter closure of patent ductus arteriosus in some dogs.