Use of a modified open patch-graft technique and valvulectomy for correction of severe pulmonic stenosis in dogs: eight consecutive cases

Use of an autologous pericardial patch to repair a post-traumatic caudal vena cava cicatrix in a dog

OBJECTIVE

To report the use of a pericardial patch graft to repair a post-traumatic caudal vena cava cicatrix in a dog.

STUDY DESIGN

Case report.

ANIMALS

A 1 year-old Rottweiler presenting with ascites following presumed blunt thoracic trauma.

METHODS

Kinking of the caudal vena cava and resultant Budd-Chiari-like syndrome was diagnosed on echocardiography and computed tomographic angiography (CTA). Surgical exploration via right sixth intercostal thoracotomy was performed. Release of the cicatrix was unsuccessful in reducing the pressure gradient and a pericardial patch graft repair of the thoracic caudal vena cava was therefore performed to relieve the obstruction.

RESULTS

The dog recovered from surgery and was discharged after 3 days. Follow-up at 6 weeks showed resolution of ascites and all clinical signs. Owner telephone follow-up at 24 months post-surgery confirmed that the dog remained clinically normal.

CONCLUSION

A pericardial patch graft technique can be used successfully to reconstruct the thoracic caudal vena cava, in cases of traumatic kinking where dissection of the fibrotic band alone fails to reduce caudal caval pressure.

Transvalvular pulmonic stent angioplasty: procedural outcomes and complications in 15 dogs with pulmonic stenosis

INTRODUCTION

Balloon valvuloplasty is the treatment of choice for dogs with severe type A pulmonic stenosis (PS), but less successful for dogs with annular hypoplasia and unsuitable for supravalvular stenosis or cases with a circumpulmonary coronary malformation. We report outcomes and complications of the first 15 consecutive transvalvular pulmonic stent angioplasty procedures performed by a single center in dogs with PS.

ANIMALS

Fifteen dogs with naturally occurring PS were included in the study.

MATERIALS AND METHODS

Dogs underwent echocardiography before and four weeks after the procedure. Transvenous approaches were used to deploy a pre-mounted, balloon-expandable metallic stent in all cases.

RESULTS

Of 15 dogs, all had annular hypoplasia, and in addition, supravalvular stenosis was diagnosed in 11 of 15 dogs, and three had R2A coronary malformation. All dogs survived to discharge. One dog died less than four weeks postoperatively (non-cardiac), but 14 of 15 dogs were re-examined at four weeks. Severity reduced in all cases; median pressure gradient reduced from 137 mmHg (range 81-202 mmHg) to 83 mmHg (range 31-155 mmHg). Clinical signs improved in all cases, and hematocrit reduced in all dogs with erythrocytosis. The median follow-up time was 280 days (range 95-896 days). Over one-year follow-up was available in six of fifteen dogs. Two dogs died because of refractory right-sided congestive heart failure signs: one at 10 months and one at 22 months postoperatively.

CONCLUSIONS

Transvalvular pulmonic stent angioplasty technique was associated with an improvement in clinical signs and reduction in stenosis severity for all dogs in this population, including cases with supravalvular PS or circumpulmonary coronary malformation.

A novel hybrid stent technique to treat canine pulmonic stenosis

Balloon valvuloplasty is routinely performed in dogs with severe pulmonic stenosis using a transvenous approach. We report a novel transventricular approach to stent the right ventricular outflow tract. An 18-month old Havanese with frequent syncope was referred with a diagnosis of severe valvular pulmonic stenosis. Transvenous approaches were unsuccessful; therefore, two Palmaz XL 29 mm by 12 mm transhepatic biliary stents were deployed across the valve using a direct right ventricular approach. The echocardiographically derived systolic pressure gradient decreased from 133 mmHg to 39 mmHg with resolution of clinical signs. The patient continues to do well after 3 years with occasional syncope when extremely excited despite pressure gradient increases to 130 mmHg at 12 months and 174 mmHg at 22 months.

Pericardial flap to repair a pulmonary laceration in a cat with pyothorax

Case summary

A 2-year-old female neutered domestic shorthair cat was presented for investigation of acute onset tachypnoea and dyspnoea. Pyothorax was diagnosed based on thoracic radiographs and fluid analysis. Medical treatment consisted of bilateral thoracostomy tube placement, antibiotic therapy and thoracic lavage. After 12 days of medical management infection was still present, warranting exploratory thoracotomy. At surgery, encapsulated abscesses were found in the left lung, right cranial and right middle lobes. The right caudal lobe was the only macroscopically non-abscessated lobe, and appeared to have a parenchymal laceration 8 mm long over the dorsolateral surface. Following partial pericardiectomy, mediastinectomy and debridement of abscesses, a pericardial flap was reflected caudolaterally and apposed over the laceration to seal the affected lung lobe. This flap was sutured to a rim of fibrinous adhesion that was partially covering this lobe. After 8 days the cat was discharged with antibiotic therapy for 3 more weeks. Follow-up assessment at 19 and 38 weeks postoperatively confirmed the cat to have good exercise tolerance. Thoracic radiographs at 19 weeks revealed good bilateral aeration of the pulmonary parenchyma without pleural effusion.

Relevance and novel information

Lung lobe laceration can be treated by lung lobectomy or direct suturing of the lung parenchyma. This is the first report using a pericardial flap to repair a lung laceration. Pericardial flap was successfully used to treat this lung laceration where lobectomy was contraindicated. Encouraging results were present at 8 months postoperatively.

Pericardial Free Patch Grafting as a Rescue Technique in Surgical Management of Right Atrial HSA

A 7 yr old, neutered female vizsla underwent an exploratory thoracotomy after diagnosis of recurrent hemorrhagic pericardial effusion and a right auricular mass. Staging tests were negative for metastasis. The patient underwent a right, fourth intercostal thoracotomy, subtotal pericardectomy, right auricular mass excision, and pericardial free patch graft. The patient experienced blood loss during surgery, which required a packed red blood cell transfusion. The patient experienced transient arrhythmias postoperatively, but was discharged from the hospital 48 hr later. Histopathologic diagnosis of the mass was hemangiosarcoma. The patient was treated with carboplatin single-agent chemotherapy and palliative radiation therapy. The patient died at home, presumably from metastatic disease 260 days postoperatively. Surgical mass removal or debulking along with pericardial free patch grafting may be considered as palliative treatment options for dogs diagnosed with right auricular masses. In this case report, other techniques failed to repair the defect in the heart and a free patch graft offered a good rescue procedure with a favorable outcome without the need for inflow and outflow occlusion when used in conjunction with adjunctive therapies.

Histological study of right ventricle-pulmonary artery valved conduit implantation (RPVC) in dogs with pulmonic stenosis

We examined whether right ventricle-pulmonary artery valved conduit (RPVC) implantation can overcome the disadvantages of current procedures for pulmonic stenosis (PS). We histologically evaluated the feasibility of RPVC using a homograft in PS model dogs. Eight dogs underwent pulmonary artery banding (PAB) and then 12 weeks later were assigned to PAB (n=4) or PAB+RPVC (n=4) groups. Dogs in the PAB group received no treatment throughout the experimental period, whereas the PAB+RPVC group underwent RPVC. At 1 year after PAB, hearts and conduits were explanted from euthanized dogs and histologically evaluated. The ratios (%) of myocardial fibrosis on right ventricle (RV) epicardial, median and endocardial layers were significantly lower in the PAB+RPVC, than in the PAB group. The ratio of myocardial fibrosis on left ventricular (LV) epicardial and endocardial layers were significantly lower in the PAB+RPVC, than in the PAB group. Neo-intimal thickness in the anastomosis areas of the Denacol and PAB+RPVC groups was 42.77 +/- 30.19 and 88.30 +/- 27.24 microm, respectively, with no significant differences between the groups. Calcification and neo- intima hypertrophy were not obvious in the valve area. Immunohistological staining showed that the internal surface of the anastomosis and intermediate areas were positive for endothelial cells. We concluded that RPVC using a bioprosthetic graft can apparently overcome the disadvantages of current procedures for pulmonic stenosis.

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.

Successful surgical correction of supravalvular pulmonary stenosis under beating heart using a cardiopulmonary bypass system in a dog

A male Pomeranian dog aged 1 year and 8 months was presented for evaluation of severe systolic ejection, cardiac murmur and syncope on excitation. Supravalvular pulmonary stenosis was diagnosed. An echocardiogram showed a supravalvular membranous stricture and a severely increased pulmonary arterial velocity in the stricture (6.49 m/s, pressure gradient of 169 mmHg). The supravalvular stricture was surgically removed by pulmonary arteriotomy with the heart beating using a cardiopulmonary bypass system. The postoperative pulmonary arterial velocity at the narrow area decreased to 3.80 m/s, and the pressure gradient decreased to 57.7 mmHg. Six months after the operation, there were no signs of restenosis, and the dog was in good condition without syncope. Surgical correction of pulmonary stenosis with the heart beating using a cardiopulmonary bypass system is useful because of the improvement it brings in safety and reliability.

Results of balloon valvuloplasty in 40 dogs with pulmonic stenosis

The records of 43 dogs presenting with severe pulmonic stenosis in which balloon valvuloplasty was attempted were reviewed. Thirty-four dogs (79 per cent) were symptomatic at initial presentation. All patients were selected for balloon valvuloplasty on the basis of a Doppler-derived trans-stenotic pressure gradient of over 80 mmHg and concurrent evidence of mild to severe right ventricular hypertrophy. Forty dogs underwent balloon valvuloplasty; the procedure was not performed in three dogs because of an aberrant coronary artery in two cases and because catheterisation of the pulmonary artery was not possible in the third. Overall, 37 out of the 40 dogs (93 per cent) were successfully ballooned, resulting in a mean reduction in the pressure gradient of 46 per cent, with a mean pressure gradient of 124 mmHg on presentation and 67 mmHg six months after the procedure. Three dogs died during balloon valvuloplasty (all of which had a concurrent defect) and three dogs showed a poor clinical response to the procedure. Thus balloon valvuloplasty was successful and resulted in a sustained clinical improvement in 80 per cent of previously symptomatic cases. This study was undertaken to document the results of balloon valvuloplasty in a larger population of dogs than has previously been published.

Pulmonic stenosis in two cats

The clinical, radiographic and echocardiographic features of two cases of pulmonic stenosis in cats are presented. A rarely reported combination of pulmonic stenosis and tricuspid valve dysplasia is described.

Evaluation of closed pericardial patch grafting for management of severe pulmonic stenosis

Closed pericardial patch-grafting has been advocated for the treatment of severe pulmonic stenosis. In this study pre- and postoperative echocardiography was used to determine if the transvalvular pressure gradient was successfully lowered by this surgery and whether it remained lowered long term. The valvulotomy-ventriculectomy wire was passed using a blunt needle in four dogs (Bresnock technique1) and via a soft catheter in five dogs (Shores and Weirich modification). Eight of nine patients survived the perioperative period. These dogs were assessed up to 40 months following surgery for clinical and echocardiographic changes. Five cases showed significant decrease in peak pulmonic pressure gradient immediately after surgery (decreasing by 50-81%, P < 0.05), and six cases showed significant decrease 2 to 40 months postoperatively (decreasing by 31-80%, P < 0.005) when compared to preoperative values. There was no significant change in pulmonic pressure gradient from immediately postoperatively to 2 to 40 months postoperatively (P < 0.48). Six dogs showed clinical improvement postoperatively, however persistent right ventricular hypertrophy was observed in all cases. One dog died with symptoms of congestive heart failure 16 months postoperatively. Closed pericardial patch grafting can improve clinical signs in symptomatic patients, however the surgery has significant risks, long term prognosis for these patients is guarded and recurrence of clinical signs and development of congestive heart failure is possible. Cardiac changes can be monitored with Doppler flow echocardiography. Patients with extremely elevated preoperative pressure gradients may be expected to have poorer outcomes.

Intraoperative hemorrhage during patent ductus arteriosus ligation in dogs

OBJECTIVE

To determine the prevalence of intraoperative hemorrhage in a consecutive series of dogs undergoing patent ductus arteriosus (PDA) ligation at a veterinary teaching hospital, and to describe strategies to reduce the risk of ductus perforation and deal with hemorrhage when it occurs.

STUDY DESIGN

Retrospective clinical study.

ANIMALS

Sixty-four dogs.

METHODS

The records of all dogs undergoing PDA ligation at the University Veterinary Center, Sydney between May 1989 and February 1998 were reviewed and the prevalence and nature of complications identified.

RESULTS

Serious hemorrhage occurred in 4 of 64 dogs (6.25%) that underwent PDA ligation. In all cases, hemorrhage resulted from perforation of the craniomedial aspect of the ductus while attempting to expose the tips of the dissecting forceps. Hemorrhage was controlled in 3 dogs by clamping the main pulmonary artery, digital compression of the descending aorta, and completion of ductus ligation during an approximately 5-minute period of circulatory arrest. The remaining dog exsanguinated during an unsuccessful attempt to locate, clamp, and ligate the bleeding point. The mortality rate for PDA ligation was I of 64 dogs (1.6 %).

CONCLUSIONS

The technique described in this report permits simple ligation of a range of different ductus morphologies in dogs of varying breeds, weights, and ages. In the event of serious hemorrhage, prompt ventricular outflow occlusion and ductus ligation followed by rapid whole blood transfusion is life saving in most cases.

Outcomes of thoracic surgery in dogs and cats

Records of 146 dogs and 41 cats that underwent thoracic surgery at The University of Sydney Veterinary Teaching Hospital were reviewed for age, sex, breed, disease, operation date, periods of pre- and post-operative hospitalisation, use of surgical drains and outcome. Animals were assigned to 16 disease categories, the most common being patent ductus arteriosus, traumatic diaphragmatic hernia and oesophageal foreign body in dogs and traumatic diaphragmatic hernia in cats. Differences were observed between disease categories in all the criteria examined. There were almost equal numbers of male (72) and female (74) dogs, the median (range) age was 2.0 (0.2 to 14.0) years, the median pre-operative stay was 1 (0 to 14) days, the median post-operative stay was 4 (0 to 28) days and the overall survival to discharge rate was 78%. There were 24 male and 15 female cats (sex not recorded in 2 cats). The median (range) age was 3 (0.1 to 12) years, pre-operative stay 1 (0 to 6) days, post-operative stay 5 (0 to 15) days and the overall survival to discharge rate was 85%. Causes of post-operative deaths among animals in the most common categories are recorded and discussed.

Ventricular septal defect repair in a small dog using cross-circulation

A haemodynamically significant ventricular septal defect was diagnosed in a 3-month-old male Cavalier King Charles Spaniel. A median sternotomy was performed and the 6.5 kg dog placed on cardiopulmonary bypass using pump-assisted cross-circulation. A 10 mm diameter peri-membranous ventricular septal defect was closed using a continuous suture of 4-0 polypropylene, via a 2.5 cm incision in the right ventricular outflow tract. The duration of cardiopulmonary bypass was 90 minutes. Complications in the immediate postoperative period were mild and easily managed.