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Biomedical subjects

J W Buchanan

Publications and source records attributed to J W Buchanan.

72 records · Page 4Linked to original sources

Esophageal obstruction caused by a left aortic arch and an anomalous right patent ductus arteriosus in two German Shepherd littermates.

OBJECTIVE: To present details of surgical management of an unusual vascular ring anomaly in two German Shepherd littermates. STUDY DESIGN: Clinical case report. STUDY POPULATION: Three-month-old intact male and female German Shepherd littermates. RESULTS: In each dog, the esophagus was obstructed by a vascular ring comprised of the left aortic arch, an anomalous patent right ductus arteriosus, and the pulmonary artery ventrally. Surgical treatment consisted of dividing and oversewing the patent right ductus arteriosus. Neither dog has clinical signs of esophageal disease one year after treatment. CONCLUSION AND CLINICAL RELEVANCE: This vascular ring anomaly should be considered a possibility in any young dog with esophageal obstruction and a machinery murmur.

Animals↗

Circumferential suture of the mitral annulus for correction of mitral regurgitation in dogs.

OBJECTIVE: To develop a method for reducing mitral regurgitation in dogs by positioning and tightening a circumferential suture around the mitral valve annulus. STUDY DESIGN: Description of clinical cases. ANIMALS: 15 dogs with spontaneous mitral valve disease, annular dilation, and refractory congestive heart failure treated between 1962 and 1994. METHODS: A composite suture material was constructed using braided Teflon-impregnated polyester sternotomy suture, barium sulfate thread, and Silastic tubing. Through a left lateral thoracotomy, the suture was positioned around the mitral annulus by passing it through the coronary sinus, right atrium, and underneath the left coronary arteries before tightening it. RESULTS: Six dogs died during surgery because of hemorrhage from the left atrium, coronary sinus, or left coronary artery. Three dogs died postoperatively because of coronary artery compression by the suture. Satisfactory suture placement was achieved in six dogs, three of which were long-term survivors (6 to 26 months) before they were euthanatized for noncardiac reasons. CONCLUSIONS: Reduction of mitral annulus diameter with a circumferential purse-string suture does not require cardiopulmonary bypass. The surgery is technically difficult, and detailed knowledge of coronary artery anatomy is required. The current suture design is inexpensive, radiopaque, and biocompatible; no special instruments are required for placement. CLINICAL RELEVANCE: Mitral regurgitation is the most common cardiovascular disorder in dogs and the most common cause of congestive heart failure. Annular dilation occurs as a consequence of mitral regurgitation. Placement and tightening of a circumferential suture around the mitral annulus reduces the degree of mitral regurgitation.

Animals↗

Short-term hemodynamic evaluation of circumferential mitral annuloplasty for correction of mitral valve regurgitation in dogs.

OBJECTIVE: To determine the short-term hemodynamic effects associated with circumferential mitral annuloplasty (CMA) in dogs with mitral regurgitation. STUDY DESIGN: Prospective experimental study. Animals-Seven healthy adult mongrel dogs. METHODS: Mitral regurgitation was surgically induced, and annular dilation occurred. Echocardiography and cardiac catheterization were used to determine forward ejection fraction (FEF), regurgitant fraction (RF), pulmonary capillary wedge pressure (PCWP), and annular diameter before and immediately after CMA in five dogs. FEF and RF were also evaluated 7 days after annuloplasty. RESULTS: Mean annular diameter and PCWP were significantly reduced immediately after CMA. Significant increases in FEF of 19% and 22% were shown immediately and 7 days after CMA. Significant reductions in RF of 19% and 22% were also shown immediately and 7 days after annuloplasty. CONCLUSIONS: Sustained hemodynamic benefits and a reduction in annular diameter were achieved by CMA in a canine model of mitral regurgitation. CLINICAL IMPLICATIONS: CMA may be a suitable treatment for heart failure because of mitral regurgitation when early signs of cardiovascular decompensation persist despite appropriate medical management.

Animals↗

Radiographic and echocardiographic measurement of the heart in obese cats.

A prospective study was undertaken to reconcile radiographic cardiomegaly and normal echocardiography in obese cats and to test a radiographic technique for better distinguishing between pericardial fat and the heart. Ten obese, but otherwise normal cats and 10 non-obese normal cats were used. A body condition scoring system was used to objectively group obese and non-obese normal cats. Two-dimensional echocardiograms were made to verify that all cats had a normal heart. Thoracic radiographs then were made using standard and altered exposure techniques. The hearts were measured on these radiographs using the metric and a vertebral scale system. Obese cats consistently had excessive fat around the heart especially if they also had a large amount of falciform fat. Altering exposure technique by increasing mAs and decreasing kVp sometimes enhanced the radiographic contrast between fat and myocardium. Enhanced radiographic contrast accentuated the double silhouette identifying the true cardiac silhouette within the fat expanded silhouette. Pericardial fat usually was distinguished more readily in lateral than in VD radiographs. In two cats, pericardial fat had a characteristic prominent square corner to the right cranial margin of the cardiac silhouette in VD radiographs. Obesity caused increased width and depth of the thoracic cage. 2D echocardiograms revealed normal cardiac dimensions in both groups of cats and increased precordial distance in the obese group.

Adipose Tissue↗

Echocardiography and surgery in a dog with left atrial rupture and hemopericardium.

Endocardial splitting and left atrial rupture were diagnosed in a dog with mitral regurgitation that experienced the sudden onset of collapsing episodes, weakness, depression, labored breathing, and weak pulses. Thoracic radiographs showed a rounded cardiac silhouette with prominent left atrium consistent with hemopericardium due to left atrial rupture. Two-dimensional echocardiography confirmed the presence of severe mitral valve disease, pericardial fluid, and a laminated blood clot caudal to the left ventricle. A sterile emergency thoracotomy was performed, the hemopericardium and blood clot were removed, and the rupture site in the left atrium was repaired with reinforced sutures. The dog recovered from surgery but died the next day, presumably from a ventricular arrhythmia.

Animals↗

Pathogenesis of single right coronary artery and pulmonic stenosis in English Bulldogs.

English Bulldogs are the most common breed to have pulmonic stenosis. Previous studies showed that this congenital heart abnormality in Bulldogs frequently is caused by a circumpulmonary left coronary artery originating from a single right coronary artery. Fetal anasarca also occurs often in Bulldogs and might represent congestive heart failure, but the cause is unknown. To determine if fetal anasarca is associated with a coronary anomaly and pulmonic stenosis, major coronary arteries were studied in 6 bulldog puppies with fetal anasarca. Five of the puppies had normal coronary arteries, and this led to the conclusion that fetal anasarca usually is not associated with major coronary abnormalities or pulmonic stenosis. The 6th puppy had single right coronary artery with circumpulmonary left coronary artery and moderate subvalvular pulmonic stenosis. Serial section histology suggests that the underlying cause of this syndrome is malformation of the left aortic sinus (of Valsalva) and inversion of the proximal segment of the left main coronary artery.

Animals↗