Transvenous cardiac pacing

Transvenous pacing therapy is a life-saving technique for patients with clinically significant bradyarrhythmias. For most symptomatic bradyarrhythmias in small animals, there is no effective substitute for cardiac pacing. The methods employed for pacemaker placement, although potentially time-consuming, are not technically difficult. This article discusses the indications, techniques, clinical decision-making, and potential complications associated with temporary and permanent transvenous cardiac pacing.     

Intramedullary interlocking nail stabilisation of 21 humeral fractures in 19 dogs and one cat

OBJECTIVE: To assess the suitability of the intramedullary interlocking nail to stabilise humeral diaphyseal fractures in dogs and cats. METHOD: This multi-centre study retrospectively examined medical records, between June 1994 and May 2001, of 19 dogs and one cat, in which a total of 21 humeral fractures were stabilised with intramedullary interlocking nails. RESULTS: Animals ranged in body-weight from 4 to 97 kg. Eighteen (86%) of the fractures were comminuted. Adjunctive stabilisation was used in twelve (57%) fractures and bone grafts in nine (43%) fractures. A rapid return of function was noted in the majority of animals, with 14 (67%) having good or excellent function within four days of surgery. In two fractures the repair collapsed when a single proximal transcortical screw was placed cranial to the tricipital line of the humerus. This suggests that if a single transcortical screw is placed proximally the screw should be distal or caudal to the tricipital line in order to engage sufficient cortical bone. Eighteen (86%) of the fractures healed when stabilised with intramedullary interlocking nails. Three fractures did not heal. One was in a dog where a pathological fracture was temporarily stabilised with an intramedullary interlocking nail, one in a dog that died of an abdominal crisis three weeks after surgery and one in a dog in which fracture stabilisation collapsed due to incorrect implant selection. CONCLUSION: Intramedullary interlocking nails are well suited to the stabilisation of humeral diaphyseal fractures in dogs and cats.     

Noninvasive transthoracic temporary cardiac pacing in dogs

Temporary cardiac pacing is used in the emergency treatment of life-threatening bradyarrhythmias and for the support of heart rate and blood pressure of patients with sick sinus syndrome or high-grade atrioventricular (AV) block undergoing general anesthesia, typically for permanent pacemaker implantation. We retrospectively evaluated the safety and efficacy of a noninvasive transthoracic external cardiac pacing system in 42 dogs treated for bradyarrhythmias. Optimal placement of the patch electrodes on the skin of the thorax was initially established on 2 anesthetized normal dogs. The optimal electrode placement was determined to be on the right and left hemithoraces, directly over the heart. Afterward, by means of this electrode placement all 42 dogs treated for bradyarrhythmias in this study were successfully paced with the noninvasive transthoracic system. Dogs ranged in age from 1 to 15 years and weighed between 3.2 and 40 kg. Miniature Schnauzers, German Shepherds, and mixed breeds were most common in the study population. Indications for noninvasive transthoracic pacing included emergency treatment of hemodynamically unstable 3rd-degree AV block (2 dogs): support of heart rate during general anesthesia for permanent pacemaker implantation or lead-wire adjustment (38 dogs): and support of heart rate during general anesthesia for ophthalmologic surgery in dogs with sick sinus syndrome (2 dogs). Complications included pain and skeletal muscle stimulation, which required general anesthesia. We conclude that the noninvasive transthoracic pacing system evaluated is satisfactory for clinical veterinary use.     

Practices and outcome of artificial cardiac pacing in 154 dogs

Artificial pacing (AP) is a treatment for symptomatic bradyarrhythmias unresponsive to medical therapy. This retrospective study was designed to define the practices and outcome of AP in dogs at 7 referral institutions participating in the Companion Animal Pacemaker Registry and Repository (CANPACERS). The indications, implantation techniques, complications, long-term outcome, and owner satisfaction were examined. One hundred fifty-four dogs were identified as undergoing AP from January 1, 1991, to January 1, 1996. Third-degree atrioventricular (AV) block (n = 91; 59%) and sinus node dysfunction (n = 45; 29%) were the most common indications for AP Transvenous endocardial AP systems were implanted in 136 dogs (88%), and epicardial systems were implanted in 18 (12%). Complications associated with AP were reported in 84 dogs (55%). Major complications occurred in 51 dogs (33%), including dislodgement of the pacing lead (n = 15; 10%), generator failure (n = 10; 6%), cardiac arrest during implantation (n = 9; 6%), and infection (n = 7; 5%). Minor complications occurred in 47 dogs (31%), including seroma formation (n = 18; 12%), muscle twitch (n = 17; 11%), and inconsequential arrhythmias (n = 15; 10%). Fourteen dogs (9%) experienced both major and minor complications. Survival analysis revealed 1-, 2-, and 3-year survival rates of 70, 57, and 45%, respectively. Age and presence of preexisting congestive heart failure (CHF) had a negative effect on survival (P = .001). Sixty percent of dogs with preexisting CHF died within 1 year of implantation, whereas 25% of dogs without heart failure died during the same period. Owners rated their satisfaction with the procedure as high in 80% of the dogs.     

Efficacy of two commercially available cardiac pacing catheters for transesophageal atrial pacing in dogs

ObjectiveCompare the efficacy of two cardiac pacing catheters for transesophageal atrial pacing (TAP).AnimalsTen healthy dogs.MethodsTransesophageal atrial pacing was attempted in left lateral recumbency under general anesthesia. In series, a curved electrophysiologic (EP) catheter and a straight transesophageal pacing (TP) catheter were passed transorally into the distal esophagus, caudal to the heart. Each catheter was slowly withdrawn until pacing was initiated. The catheter continued to be withdrawn in 5 mm increments until capture was no longer achieved at maximal pacing setting creating a total zone of capture (tZOC). Minimum pacing threshold (Th_min) and degree of extraneous muscle stimulation (EMS) were determined at each site.ResultsThe EP catheter achieved TAP in 10/10 dogs with a Th_min of 8.8 ± 4.8 mA and tZOC of 4.0 ± 1.7 cm. The TP catheter achieved TAP in 7/10 dogs with a Th_min of 22.5 ± 5.6 mA and tZOC of 1.2 ± 1.6 cm. No EMS was noted during TAP at Th_min using the EP catheter. Of the 7 dogs in which TAP was successful, 3/7 experienced considerable EMS at Th_min. There was no significant relationship between patient body weight and Th_min with either catheter (EP catheter P = 0.09; TP catheter P = 0.81).ConclusionsThe electrophysiology catheter captured the atria of more dogs over a larger area without EMS as compared to the TP catheter. The electrophysiology catheter is recommended for transesophageal atrial pacing in dogs.     

Intraocular findings in three dogs and one cat with chronic glaucoma

Intraocular neoplasia may cause secondary glaucoma. If an intraocular prosthesis is placed in an eye with glaucoma secondary to intraocular neoplasia, the neoplasm frequently regrows around the prosthetic ball, resulting in recurrence of buphthalmos and signs of pain. Histologic examination of eviscerated intraocular contents of 4 animals resulted in diagnosis of intraocular neoplasia in 2 glaucomatous eyes and ruled out neoplasia as the cause of glaucoma in 2 eyes.     

Severe hypophosphatemia associated with diabetes mellitus in six dogs and one cat

Severe hypophosphatemia was found in 6 diabetic dogs and in one diabetic cat. The cat suffered from hemolysis, and one dog had seizures, both apparently as a result of the severe hypophosphatemia. Clinical signs were not determined solely by the serum concentration of phosphorus, as seen in 5 other patients that did not have signs of disease despite similar serum phosphorus concentrations.     

Imaging and surgical outcomes of spinal tumors in 18 dogs and one cat

Clinical and magnetic resonance imaging (MRI) findings, histological appearances and surgical outcomes of 18 dogs and one cat with spinal tumors are presented. Medical records of the cases admitted for spinal disorders were reviewed, and cases of spinal tumors that were diagnosed by MRI and confirmed by histological examination were included in this study. T1 weighted, T2 weighted and contrast enhanced T1 weighted images were taken and interpreted to evaluate the spinal tumors. The tumors were diagnosed as: meningioma (n = 6), ependymoma (n = 1), nerve sheath tumor (n = 4), metastatic spinal tumor (n = 3), osteosarcoma (n = 2), osteoma (n = 1), rhabdomyosarcoma (n = 1), and nephroblastoma (n = 1). Thirteen cases underwent surgical operation and the remaining six cases were euthanized at the request of the owners. The neurological status of the surgical cases did not deteriorate, except for one dog that showed ependymoma in the early period after the operation. These results indicate the potential for surgical gross total tumor removal of vertebral tumors to provide better quality of life and surgical collection of histological specimens for definitive diagnosis. For effective case management, dedicated MRI examination is important to accurate evaluation of the spinal tumors, and surgical treatment is useful for extradural and intradural-extramedullary spinal tumors.     

Suspected sphenoid bone osteomyelitis causing visual impairment in two dogs and one cat

Objective  To present the clinical and magnetic resonance imaging (MRI) characteristics of sphenoid bone osteomyelitis.
Procedures  Two dogs (English Springer Spaniel – ESS, Golden Retriever – GR) and one cat (Domestic Long Haired) were presented with a 2–14-day history of visual deficits and reduced pupillary light reflexes. Investigations included physical, ophthalmologic and neurological examination as well as hematology, serum biochemistry, MRI of the head and cerebrospinal fluid (CSF) analysis.
Results  MRI changes included thickening of the sphenoid bone and a loss of normal bone marrow signal on T1W MRI. Enhancement of the sphenoid bones, ventral meninges and ventral surface of the brain was present using paramagnetic contrast medium. CSF analysis was abnormal in the two dogs with increased cellularity, neutrophilic pleocytosis, intracellular bacteria and increased total protein in one, and with lymphocytic pleocytosis in another. CSF analysis was normal in the cat.
An underlying cause for the osteomyelitis could not be identified. The use of broad-spectrum antibiotics for 3–6 weeks combined with anti-inflammatory medications proved effective. Full clinical recovery occurred with no relapse during the follow up time of 7 (ESS) and 4 (Domestic Long Haired) years. The GR relapsed 10 months after treatment and recovered following a second 3-week course of broad-spectrum antibiotics with no relapse during the following 3 years.
Conclusion  Visual pathway deficits in dogs and cats may be due to sphenoid bone osteomyelitis. MRI and CSF analysis can assist diagnosing this potentially treatable condition. To the authors' knowledge this is the first report of sphenoid bone osteomyelitis in these species.     

Neurological dysfunction in three dogs and one cat following attenuation of intrahepatic portosystemic shunts

Neurological dysfunction is an uncommon complication following extrahepatic portosystemic shunt ligation. Three dogs and one cat are described that developed neurological signs within 21 to 42 hours of attenuation of intrahepatic portosystemic shunts. None of these cases had biochemical evidence of hepatic encephalopathy postoperatively. Two dogs died during management of status epilepticus following aspiration of food. One dog died six months postoperatively. The cat had persistent neurological dysfunction at discharge, but was alive and had recovered most of its neurological function at the time of writing, 37 months after surgery. This report demonstrates the potential for animals with intrahepatic portosystemic shunts to develop postoperative neurological signs and highlights the difficulty of managing such cases. Two dogs had both intrahepatic and extrahepatic portosystemic shunts. Large intestinal malrotation (partial situs inversus) may have been linked to the development of a portosystemic shunt in the remaining dog.     

Middle ear disease associated with congenital palatine defects in seven dogs and one cat

Medical records of eight dogs and one cat with congenital palatine defects were reviewed retrospectively. Five of the dogs had nasal discharge and seven had radiographic signs of middle ear disease, but no clinical signs of ear disease were identified in any of the dogs, nor were any reported by their owners during a one- to five-year follow-up period. One dog had an ipsilateral impairment of hearing detected by brainstem auditory evoked responses. The cat had clinical and radiographic signs of middle ear disease. These findings suggest that, as in humans, congenital palatine defects in dogs and cats may predispose to middle ear disease. Any associated deafness could cause problems for working dogs.     

Fusion podoplasty for the management of chronic pedal conditions in seven dogs and one cat

Eight animals underwent fusion podoplasties for the treatment of chronic interdigital furunculosis (n=3), ectrodactyly (n=1), digit abnormalities associated with tendonectomy (n=1), redundant indertigital skin (n=1), conformational deformity (n=1), and necrotizing fasciitis of the paw (n=1). Median duration of bandaging was 14 days, and median duration of hospitalization was 5 days. Four dogs had dehiscence, which occurred at a mean time of 11 days after surgery. Clinical abnormalities necessitating podoplasty resolved in six animals and improved in two. Six animals had normal ambulation and two dogs had slight weight-bearing lameness after a median follow-up time of 29 mo. Fusion podoplasty may be recommended as a salvage procedure for the treatment of various chronic pedal diseases in dogs and cats.     

Inadvertent severe hypercarbia associated with anesthesia machine malfunction in one cat and two dogs.

Severe acute hypercarbia occurred in a cat and 2 dogs as a result of anesthesia machine malfunction. In each case, the anesthesia machine had been checked by the anesthesia technician and clinician, and no problems were found. After it was noticed that the same machine had been used on each animal, further investigation revealed an expiration valve that was functional with large breaths or positive pressure ventilation but was not functional with small breaths with low peak inspiratory flow. Rebreathing of expired carbon dioxide occurred, and the patients subsequently became severely hypercarbic. Recovery from anesthesia was prolonged in 2 animals, and cardiac and respiratory arrest occurred in the third. Hypercarbia from rebreathing can be detected through the use of blood gas analysis or end-tidal carbon monoxide monitoring.     

Transvenous electrical cardioversion of atrial fibrillation in two dogs

Atrial fibrillation is characterized by uncoordinated electrical activation of the atria that leads to the loss of atrial mechanical function and atrial fibrosis as a substrate promoting maintenance of rhythm abnormality. Transvenous electrical cardioversion has not been previously reported in the dog. The authors demonstrate the use of this technique for successful cardioversion of atrial fibrillation in two dogs with dilated cardiomyopathy.     

Occurrence of pulsus alternans during anaesthesia of two dogs and one cat and its treatment

The authors report the occurrence of pulsus alternans, a condition characterised by the alternance of pulses of higher and lower amplitude, in two dogs and one cat under general anaesthesia. The presence of an underlying cardiac disease was confirmed in the cat but not in either dog, which – based on history and clinical findings – had presumably normal cardiovascular function before the anaesthetic. Possible mechanisms, including negative inotropy and haemodynamic and Frank-Starling effects, as well as the role of general anaesthesia as the potential triggering factor, are discussed in this report. Ephedrine resulted in the successful treatment of pulsus alternans, as demonstrated by the return of normal pulse and synchronisation of heart and pulse rates in the cat and in one dog. In the other dog, pulse pattern and frequency returned to normal once the guidewire for central line placement was withdrawn.     

Transversus abdominis muscle as a gastric or intestinal on-lay flap in two dogs and one cat

Historically, omentalisation and serosal patching have been used to augment gastrointestinal wall defects or incisions where gastrointestinal viability is of concern. This report describes the novel use of a transversus abdominis muscle on-lay flap to augment and provide support to compromised intestine in three cases. The muscle flap was used to support: the ileum following reduction of an intussusception in a dog (case 1), the gastric wall following gastric strangulation, dilation and volvulus in a diaphragmatic rupture in a cat (case 2) and the jejunum following enterotomy and full-thickness ulcer resection with primary repair in a dog (case 3). All animals were discharged within 4 days postoperatively with no short- or long-term complications reported by either the referring veterinary surgeons on routine postoperative examination or on telephone follow-up with the owners (case 1: 10 months, case 2: 30 months, case 3: 6 weeks). The creation of a flap of the transversus abdominis muscle may provide a useful alternative or adjunct to previously described techniques for supporting the gastrointestinal tract when gastrointestinal tissue viability is questionable or resection is not feasible. Further prospective clinical evaluation studies would be indicated to determine whether the muscle flap remains viable or compare whether this technique should be recommended over conventional methods.     

Subtotal ear canal ablation in 18 dogs and one cat with minimal distal ear canal pathology

A modified technique for performing total ear canal ablations is described. This technique requires less dissection than the standard technique and maintains a portion of the distal vertical ear canal. Subtotal ear canal ablations were performed in 18 dogs and one cat for the treatment of otitis externa or masses of the horizontal ear canal. Animals with otitis externa had minimal involvement of the distal ear canal. Dermatological problems associated with the remaining ear canal and pinnae occurred in eight animals and resolved with medical management. Normal ear carriage was maintained in all animals with erect ears. Further investigation is required before the procedure can be recommended as a treatment for otitis externa not caused by masses or anatomical abnormalities of the horizontal ear canal in dogs with pendulous ears.