Right coronary artery to left ventricle coronary cameral fistula in a cat.

A six-month-old female intact domestic shorthair cat was presented for evaluation of a loud heart murmur. Transthoracic echocardiography revealed dilation of the left ventricle secondary to an abnormal vessel shunting blood into the left ventricular outflow tract at a high velocity during diastole. Multidetector computed tomography angiography revealed a coronary cameral fistula that originated at the right coronary artery, encircled the heart, and then terminated into the left ventricular outflow tract. This case report documents the first known case of a coronary cameral fistula in a cat. Multimodal imaging was an essential aspect to diagnosing the congenital lesion in this case.

Coronary arterial compression testing by simultaneous balloon valvuloplasty and coronary angiography in an English bulldog with pulmonary valve stenosis.

A 4-year-old male neutered English bulldog presented for heart murmur evaluation. Echocardiography identified severe pulmonic stenosis (an echocardiography-derived transpulmonary pressure gradient of 100 mmHg), and computed tomography confirmed the presence of an anomalous coronary artery with a prepulmonic course of the left coronary artery arising from the right coronary ostium. Before artificial pulmonic valve implantation, a coronary compression test was performed. A simultaneous aortic root angiogram and pulmonic balloon valvuloplasty revealed complete occlusion of the circumflex branch. Artificial valve implantation was aborted with concern for fatal coronary compression after implantation. Coronary compression testing is a critical component of the evaluation before catheter-based implantation of conduits across the pulmonic valve.

Electrocardiogram-gated 16-multidetector computed tomographic angiography of the coronary arteries in dogs.

The aims of this study were to assess if ECG-gated 16-multidetector CT (MDCT) provides sufficient temporal and spatial resolution to evaluate canine coronary arteries and provide a detailed description of their anatomy. A total of 24 dogs were included. Images were reviewed to assess: (1) coronary artery opacification and dominance; (2) choice of optimal R-R ECG reconstruction interval for both left coronary artery (LCA) and right coronary artery (RCA); (3) branching patterns of the left main coronary artery (LMCA); and (4) diameter and length of the LCA and RCA and classification of their branches by adapting a previously described segmental coding system. The degree of opacification of the coronary arteries was subjectively judged as excellent or good in five and 19 dogs, respectively. All hearts showed a left coronary dominance. The best R-R reconstruction interval for both LCA and RCA arteries was 75 per cent. Seven different subtypes of LMCA branching patterns were noted. The rami circumflexus and interventricularis paraconalis were divided into three angiographic segments, and the ramus septi interventricularis and the RCA in two and three segments, respectively. ECG-gated 16-MDCT coronary angiography provides adequate resolution to assist the basic anatomy of the main coronary artery branches.

Arterial distribution to the pelvic cavity and pelvic limb in the pampas deer (Ozotoceros bezoarticus, Linnaeus 1758).

This research is a study about the arterial vascularization of pelvic cavity and pelvic limb in pampas deer. For this study, 25 dead animals were used. The vascularization of the organs was investigated using a latex injection technique. Two animals were injected in the common carotid artery with contrast to cardiac angiography, and then, radiographs were taken. The aorta showed the two external iliac arteries, and after a short course, the aorta ended in two internal iliac arteries. The median sacral artery was originated from the dorsal surface cranially to the emergence of the internal iliac arteries. The last one gave off parietal (iliolumbar, cranial and caudal gluteal arteries) and visceral (umbilical and internal pudendal arteries) branches. The external iliac artery gave as first branch the deep circumflex iliac artery which was divided into a cranial and a caudal branch. After a short distance from the external iliac artery, the femoral and deep femoral arteries were originated. The deep femoral artery gave origin to the pudendoepigastric trunk and to the medial femoral circumflex artery. Based on the arterial distribution of the pelvic cavity and pelvic limb in the pampas deer, it is concluded that the internal iliac artery has a pattern of intermediate development. In reference to the distribution of the external iliac artery and its branches, the pattern of development is the cranial tibial type.

Comparison of cardiac measurements by multi-detector computed tomography angiography and transthoracic echocardiography in English bulldogs.

INTRODUCTION: Transthoracic echocardiography (TTE) is the primary tool for the assessment of cardiac structure and function in dogs but is challenging in English bulldogs due to dorsoventral compression of the thorax, obesity, and narrow intercostal spaces. Multi-detector computed tomography angiography (CTA) may overcome the conformational obstacles of cardiac imaging in this breed. ANIMALS: Eleven client-owned English bulldogs. MATERIALS AND METHODS: Prospective clinical trial with paired analysis of TTE and CTA studies. RESULTS: Eight of the 25 linear cardiac dimensional measurements were significantly different between TTE and CTA (p<0.033). Intraobserver agreement was strong with average coefficients of variation (CV) of 5.34% for TTE and 2.50% for CTA. Interobserver agreement CV averaged 6.5% for TTE and 8.75% CTA. Ejection fraction, stroke volume, and end-systolic volume were significantly different between modalities (all p<0.002). No significant difference was present between end-diastolic volume for TTE compared with CTA. DISCUSSION: High-quality cardiac angiographic studies were accomplished using CTA without the use of general anesthesia in English bulldogs. Multi-detector computed tomography angiography and TTE are not interchangeable modalities in the clinical setting. CONCLUSION: Multi-detector-CT ECG-gated cardiac angiography is possible in sedated, non-intubated English bulldogs. Differences were found between some cardiac dimensions as measured by TTE in the awake dog and compared with sedated CTA, indicating the two methodologies are not equivalent. Sedated, non-intubated CTA yielded high-quality imaging with strong intraobserver and interobserver measurement repeatability in English bulldogs.

Comparison of cardiac output measured by use of computed tomography and thermodilution in dogs.

OBJECTIVE To compare cardiac output (CO) measured by use of CT coronary angiography and thermodilution (criterion-referenced standard) at various CO values, record adverse effects, and determine the time needed to measure CO. ANIMALS 5 healthy purpose-bred Beagles (2 males and 3 females). PROCEDURES A prospective nonrandomized crossover study was conducted. Dogs were premedicated with butorphanol tartrate (0.2 mg•kg-1, IM). Anesthesia was induced by IV administration of etomidate (1 to 2 mg•kg-1) and midazolam (0.25 mg•kg-1). Orotracheal intubation was performed, and anesthesia was maintained by administration of isoflurane. The CO was determined by use of thermodilution and by use of CT at 3 CO values. Dobutamine was infused at various rates to obtain the 3 CO values. RESULTS 13 values were obtained and analyzed. The mean ± SD difference between methods was 0.09 ± 0.71 L•min-1 (95% confidence interval [CI], 0.52 to -0.34 L•min-1). Only 1 of 13 values was located on the 100% agreement line (ie, 0 line), 7 of 13 values were located within the 95% CI, and 5 of 13 values were outside the 95% CI. CONCLUSIONS AND CLINICAL RELEVANCE For this study, there was poor agreement between the 2 methods. The 95% CI interval was 0.52 to -0.34 L•min-1, and 5 of 13 values were outside the 95% CI. Therefore, results for the CT method appeared to be inappropriate for use in making clinical decisions.

Balloon dilation of congenital supravalvular pulmonic stenosis in a dog.

Percutaneous balloon valvuloplasty is considered the standard of care for treatment of valvular pulmonic stenosis, a common congenital defect in dogs. Supravalvular pulmonic stenosis is a rare form of pulmonic stenosis in dogs and standard treatment has not been established. Although, there have been reports of successful treatment of supravalvular pulmonic stenosis with surgical and stenting techniques, there have been no reports of balloon dilation to treat dogs with this condition. Here, a case of supravalvular pulmonic stenosis diagnosed echocardiographically and angiographically in which a significant reduction in pressure gradient was achieved with balloon dilation alone is presented.

Cardiac-gated computed tomography angiography in three alpacas with complex congenital heart disease.

BACKGROUND: The prevalence of congenital heart disease is higher in camelids than in other domestic species and complex defects, often involving the great vessels, are more frequently encountered in llamas and alpacas than in other species. Some of these complex defects can be difficult to accurately characterize via echocardiography, the most commonly used diagnostic imaging technique to evaluate the heart in veterinary patients. Contrast-enhanced, electrocardiogram (ECG)-gated computed tomography (CT) has proven utility for the evaluation of human patients with certain congenital heart defects, including those with conotruncal septation defects and other abnormalities involving the formation of the great vessels. METHODS: Three alpaca crias, 4 days, 5 weeks and 14 months of age were clinically evaluated and subjected to a complete color-flow Doppler echocardiogram and a contrast-enhanced ECG-gated CT. RESULTS: These alpacas exhibited a variety of clinical findings including lethargy, failure to thrive, exercise intolerance, heart murmur, and/or respiratory difficulty. All three crias were subsequently diagnosed with complex cardiac defects including pulmonary atresia with a ventricular septal defect (VSD), a truncus arteriosus with a large VSD, and a double outlet right ventricle with a large VSD and aortic hypoplasia. In each case, the diagnosis was confirmed by postmortem examination. CONCLUSION: Color flow echocardiographic evaluation identified all of the intra-cardiac lesions and associated flow anomalies but contrast-enhanced ECG-gated CT permitted more accurate assessment of the morphology of the extracardiac structures and permitted a more precise determination of the exact nature and anatomy of the great vessels.

Transesophageal echocardiography to diagnose anomalous right coronary artery type R2A in dogs.

OBJECTIVES: To assess the feasibility of transesophageal echocardiography (TEE) as an alternative to angiography for the diagnosis of R2A coronary artery (CA) abnormalities. ANIMALS: Twenty-two dogs with a diagnosis of type R2A CA anomaly were reviewed/analyzed. METHODS: A retrospective study of case records. Transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), angiography, and follow-up investigations of pulmonic stenosis (PS) with R2A CA were carried out to compare different diagnostic methods. RESULTS: Based on the TTE morphology, PS with an aberrant CA was suspected in all dogs (n = 22) and later confirmed by angiography in 18 cases (18/22), and necropsy in two cases (2/22). In 12 cases (12/22), TEE and angiography were both performed and confirmed the diagnosis of an R2A anomaly. Two cases (2/22) were diagnosed only with TEE. CONCLUSIONS: Transesophageal echocardiography may be considered an effective tool to diagnose CA abnormalities, in particular when TTE is inconclusive. Transesophageal echocardiography offers detailed and easily reproducible views of coronary ostia, and the spatial relationship between the right common CA and the great arteries. Although it is not possible to define the course of the more distal coronary branches, TEE has proven reliable in recognizing those elements that can constitute a risk for the execution of a balloon valvuloplasty (BV). Therefore, TEE can be used to confirm this type of CA anomaly and prevent a BV, which is contraindicated in these cases. In addition, TEE avoids any further vascular access, radiation exposure, and contrast medium injection.

Dynamic computed tomographic determination of scan delay for use in performing cardiac angiography in clinically normal dogs.

OBJECTIVE: To determine the scan delay for use in performing cardiac CT angiography in dogs. ANIMALS: 4 clinically normal adult Beagles. PROCEDURES: In a crossover study, 12 formulations of iohexol solutions differing in iodine dose (300, 400, and 800 mg/kg) and concentration (undiluted and diluted 1:1, 1:2, and 1:3 with saline [0.9% NaCl] solution) were administered IV to each dog. Dynamic CT angiography was performed to evaluate enhancement characteristics of each formulation, with the region of interest set over the aorta. Time-attenuation curves (TACs) were obtained and analyzed. RESULTS: Peak arc-type TACs were obtained after administration of all undiluted formulations. Curve shape changed from peak arc type to plateau type as the total volume of the contrast solution (ie, dilution) increased. Prolonged peaks characteristic of plateau-type TACs suggested that a sufficient period of homogeneous attenuation could be achieved for CT scanning with administration of higher iohexol dilutions (1:2 or 1:3) containing higher iodine doses (400 or 800 mg/kg). In particular, attenuation values for plateau-type TACs remained between 200 and 300 Hounsfield units for > 16 seconds after the plateau endpoint was reached for 1:2 and 1:3 dilutions containing an iodine dose of 800 mg/kg. Scan delays of 13 to 17 seconds were computed for those 2 formulations. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that for clinically normal dogs, a scan delay of 13 to 17 seconds could be used to perform cardiac CT angiography with iohexol solutions containing an iodine dose of 800 mg/kg at dilutions of 1:2 or 1:3.

Effects of two different anesthetic protocols on 64-MDCT coronary angiography in dogs.

Heart rate is a major factor influencing diagnostic image quality in computed tomographic coronary artery angiography (MDCT-CA), with an ideal heart rate of 60-65 beats/min in humans. The purpose of this prospective study was to compare effects of two different clinically applicable anesthetic protocols on cardiovascular parameters and 64-MDCT-CA quality in 10 healthy dogs. Scan protocols and bolus volumes were standardized. Image evaluations were performed in random order by a board-certified veterinary radiologist who was unaware of anesthetic protocols used. Heart rate during image acquisition did not differ between protocols (P = 1), with 80.6 ± 7.5 bpm for protocol A and 79.2 ± 14.2 bpm for protocol B. Mean blood pressure was significantly higher (P > 0.05) using protocol B (protocol A 62.9 ± 9.1 vs. protocol B 72.4 ± 15.9 mmHg). The R-R intervals allowing for best depiction of individual coronary artery segments were found in the end diastolic period and varied between the 70% and 95% interval. Diagnostic quality was rated excellent, good, and moderate in the majority of the segments evaluated, with higher scores given for more proximal segments and lower for more distal segments, respectively. Blur was the most commonly observed artifact and mainly affected the distal segments. No significant differences were identified between the two protocols for optimal reconstruction interval, diagnostic quality and measured length individual segments, or proximal diameter of the coronary arteries (P = 1). Findings indicated that, when used with a standardized bolus volume, both of these anesthetic protocols yielded diagnostic quality coronary 64-MDCT-CA exams in healthy dogs.

Microdose computed tomographic cardiac angiography in normal cats.

OBJECTIVES: To determine if microdose contrast-enhanced multi-detector computed tomographic angiography (MDCTA) allows characterization of cardiac chambers in lightly sedated normal cats. ANIMALS: Seven healthy domestic cats. METHODS: Lightly sedated normal cats were imaged pre-contrast and with microdose (0.22 ml/kg of non-ionic iodinated contrast medium, 300 mg I/ml) triple-phase MDCTA in a motion restriction device. RESULTS: On pre-contrast images, the aorta (median: 52.43 Hounsfield units [HU], range 27.35-76.74 HU) was outlined by significantly (p = 0.015) lower attenuating periaortic fat (-66.16 HU, -42.62 to -92.77 HU). On post-contrast images, median peak contrast enhancement in the right ventricle (111.77 HU, 36.09-141.60 HU) was achieved in 3.1 s (range 2.9-7.3 s), in the aorta (149.30 HU, 99.43-319.60 HU) and left atrium (180.83 HU, 88.53-266.84 HU) in 6.4 s (range 5.6-7.7 s) and in the left ventricle (147.89 HU, 57.23-245.77 HU) in 7.10 s (range 6.2-11.2 s). Significantly higher attenuation was measured between all chambers and walls, the right ventricular lumen and interventricular septum (median ratio 53.78 HU, range 0.21-83.20 HU), left ventricular lumen and left ventricular free wall (89.32 HU, 38.81-185.95 HU) and aorta and periaortic fat (190.43 HU, 143.22-425.44 HU) on post-contrast images. CONCLUSIONS: Sufficient biological contrast is available on survey CT to discriminate between the aorta and the left atrium, and microdose MDCTA provides sufficient contrast enhancement for adequate visualization of the heart chambers in normal cats.

[Coronary angiography of in vitro porcine heart using MSCT].

OBJECTIVE: To establish standardized methods and parameters of the isolated heart coronary angiography through the experiment of in vitro porcine heart by MSCT. METHODS: Based on different perfusion volume (50, 60 and 70 mL) and different perfusion-imaging time (5, 10 and 20 min), the in vitro porcine coronary artery was injected liposoluble and water-soluble contrast agents using remodel angiography equipment and scanned by MSCT. And the 3D image results were compared. The images were recorded and evaluated by 2 radiologists and analyzed by statistical software. RESULTS: Liposoluble contrast agent affected the images by damaging and infiltrating the fats around the coronary artery, while the water-soluble contrast agent didn't affect the images. The groups with 60 mL or 70 mL perfusion and 5 min perfusion-imaging time had the best images. CONCLUSION: The suitable parameters of the angiography lay the foundation of postmortem coronary angiography.

Coronary angiography of in vitro porcine heart using MSCT / 法医学杂志

OBJECTIVE@#To establish standardized methods and parameters of the isolated heart coronary angiography through the experiment of in vitro porcine heart by MSCT.@*METHODS@#Based on different perfusion volume (50, 60 and 70 mL) and different perfusion-imaging time (5, 10 and 20 min), the in vitro porcine coronary artery was injected liposoluble and water-soluble contrast agents using remodel angiography equipment and scanned by MSCT. And the 3D image results were compared. The images were recorded and evaluated by 2 radiologists and analyzed by statistical software.@*RESULTS@#Liposoluble contrast agent affected the images by damaging and infiltrating the fats around the coronary artery, while the water-soluble contrast agent didn't affect the images. The groups with 60 mL or 70 mL perfusion and 5 min perfusion-imaging time had the best images.@*CONCLUSION@#The suitable parameters of the angiography lay the foundation of postmortem coronary angiography.

Pulmonary angiography with 64-multidetector-row computed tomography in normal dogs.

Pulmonary angiography using 64-multidetector-row computed tomography (MDCT) was used to evaluate pulmonary artery anatomy, and determine the sensitivity of pulmonary artery segment visualization in four Beagle dogs using images reconstructed to 0.625 mm and retro-reconstructed to 1.25 and 2.5 mm slice thickness. Morphologically, characteristic features included a focal narrowing in the right cranial pulmonary artery in all dogs, which should not be mistaken as stenosis. While the right cranial pulmonary artery divided into two equally sized branches that were tracked into the periphery of the lung lobe in all dogs, only a single left cranial (cranial portion) lobar artery was present. Compared with 1.25 and 2.5 mm retro-reconstructions, 0.625 mm reconstructions allowed for detection of significantly (P≤0.05) more pulmonary artery segments and sharper depiction of vessel margins. Clinical applications such as prevalence and significance of diameter changes, and detection of pulmonary arterial thrombembolism on lobar and sublobar level, using pulmonary angiography with 64-MDCT applying 0.625 mm reconstruction slice thickness remain to be established.

64-multidetector computed tomographic angiography of the canine coronary arteries.

Canine coronary artery angiography (CTA) was performed in four anesthetized healthy dogs using 64-multidetector computed tomography. Esmolol, a ß-1 adrenergic receptor antagonist, and sodium nitroprusside, an arteriolar and venous dilator, were administered to enhance visualization of the coronary arteries by reducing heart rate and creating vasodilation. The left main coronary artery with its three main branches and the right coronary artery were visualized and subdivided in 13 segments for evaluation. Optimal reconstruction interval, expressed as percentage of the R-to-R interval, was determined at 5% in 2.9%, 35% in 1%, 75% in 21.2%, 85% in 43.3%, and 95% in 31.7% of the segments. Overall image quality was good in 41.3% of the segments and excellent in 14.4%. There was blur in 98.1%, motion in 17.3%, and stair step in 6.7% of the evaluated segments, but these artifacts did not interfere with anatomic depiction of the arteries. Cross-sectional anatomy of the coronary arteries as evaluated from the coronary CTA agreed well with gross anatomic evaluation and published information. The use of esmolol did not lead to the target heart rate of 60-65 beats/min. Nitroprusside had no significant effect on visualized length or diameter of the coronary artery branches. Coronary CTA is useful for the anatomic depiction of coronary artery branches in the dog.

Transvenous occlusion of patent ductus arteriosus in 56 consecutive dogs.

OBJECTIVE: Document safety and efficacy of transvenous catheter occlusion of patent ductus arteriosus (PDA) over a wide range of ductal and patient sizes. ANIMALS, MATERIALS AND METHODS: Retrospective study of fifty-six consecutive dogs referred to Colorado State University with diagnosis of PDA. All cases utilized the transvenous approach, via the femoral vein. Occlusion was achieved using a coil (Flipper) in dogs with PDA minimal dimension of 4 mm, or if a coil was unstable following deployment. RESULTS: Ductal occlusion was achieved using the transvenous route alone in 54/56 dogs (96.4%). Occlusion was achieved using detachable Flipper coils in 39/42 dogs (92.9%) in which coil occlusion was attempted, with 38/39 dogs (97.4%) requiring only a single coil. In 16 dogs, occlusion was achieved using an Amplatzer duct occluder or vascular plug. Post-procedure residual ductal flow was absent or only mild in 36/39 (92.3%) dogs in which it was assessed. Procedural mortality rate was 1.7%, and major complication rate 7.0%. CONCLUSION: Transcatheter occlusion via a transvenous approach is a safe and effective method for treating PDA in dogs and is useful for small dogs (<2.5 kg).

Transarterial ductal occlusion using the Amplatz Canine Duct Occluder in 40 dogs.

OBJECTIVES: Describe the result of patent ductus arteriosus (PDA) occlusion using the Amplatz Canine Duct Occluder (ACDO) in 40 dogs. ANIMALS, MATERIAL AND METHODS: Records of the first 41 dogs at Texas A&M University in which ductal occlusion with an ACDO was attempted were reviewed. RESULTS: Appropriate device release was achieved in 40 of 41 dogs. Post-release angiography in 39 dogs documented complete occlusion in 27 dogs, trivial residual flow in 7, mild residual flow in 1 and moderate residual flow in 4; angiography was not recorded in one dog. The following day transthoracic color Doppler echocardiography documented complete occlusion in all 40 dogs. One dog required a larger device than could be deployed through the largest sheath accommodated by the femoral artery and the PDA was subsequently closed by surgical ligation. CONCLUSIONS: Ductal occlusion using an ACDO has a high rate of initial and 24-h complete occlusion. Ductal occlusion using an ACDO is a safe and efficacious therapy for PDA in dogs. This report confirms the positive clinical outcome of the original report in a large cohort of dogs.

Cardiovascular effects of right ventricle-pulmonary artery valved conduit implantation in experimental pulmonic stenosis.

Right ventricle (RV)-pulmonary artery (PA) valved conduit (RPVC) implantation decreases RV systolic pressure in pulmonic stenosis (PS) by forming a bypass route between the RV and the PA. The present study evaluates valved conduits derived from canine aortae in a canine model of PS produced by pulmonary artery banding (PAB). Pulmonary stenosis was elicited using PAB in 10 conditioned beagles aged 8 months. Twelve weeks after PAB, the dogs were assigned to one group that did not undergo surgical intervention and another that underwent RPVC using denacol-treated canine aortic valved grafts (PAB+RPVC). Twelve weeks later, the rate of change in the RV-PA systolic pressure gradient was significantly decreased in the PAB+RPVC, compared with the PAB group (60.5 +/- 16.7% vs. 108.9 +/- 22.9%; p<0.01). In addition, the end-diastolic RV free wall thickness (RVFWd) was significantly reduced in the PAB+RPVC, compared with the PAB group (8.2 +/- 0.2 vs. 9.4 +/- 0.7 mm; p<0.05). Thereafter, regurgitation was not evident beyond the conduit valve and the decrease in RV pressure overload induced by RPVC was confirmed. The present results indicate that RPVC can be performed under a beating heart without cardiopulmonary bypass and adapted to dogs with various types of PS, including "supra valvular" PS or PS accompanied by dysplasia of the pulmonary valve. Therefore, we consider that this method is useful for treating PS in small animals.

Long-term palliation of tetralogy of Fallot in dogs by use of a modified Blalock-Taussig shunt.

OBJECTIVE: To describe a modified Blalock-Taussig shunt (mBT) procedure and assess its use in dogs with clinical signs associated with tetralogy of Fallot (TOF). DESIGN: Descriptive report. ANIMALS: 6 dogs with severe TOF-associated clinical signs. PROCEDURES: Each dog had TOF (confirmed echocardiographically or angiographically) and underwent an mBT shunt procedure for surgical palliation of signs. The surgery was performed through a left fourth rib resection or a left fifth intercostal thoracotomy. The left subclavian artery was dissected free from surrounding mediastinal tissue. The main pulmonary artery trunk was exposed through an incision in the overlying pericardium. A shunt comprised of a 6-mm-diameter tube of expanded polytetrafluoroethylene (5 dogs) or a segment of carotid artery (1 dog) was sutured end to side between the left subclavian artery and pulmonary artery trunk. RESULTS: 5 of the 6 dogs survived the immediate postoperative period. The dog that died shortly after surgery was the smallest of the dogs (weight, 2.9 kg [6.38 lb]) and had received the carotid artery autograft. Three dogs survived long term and 2 dogs died of unknown causes 6 years after undergoing the mBT shunt procedure. In all dogs that survived the mBT procedure, shunt patency was confirmed and quality of life appeared improved. CONCLUSIONS AND CLINICAL RELEVANCE: These findings have suggested that the mBT shunt procedure safely provides long-term palliation of TOF-associated clinical signs in dogs. In addition, it may offer an effective low-risk and lower-cost alternative to open heart repair of TOF.