Ketamine as a part of anaesthetic management in a dog with twiddler's syndrome

An 11‐year‐old male German shepherd dog was referred for possible pacemaker implantation. A routine 6‐lead electrocardiogram revealed a third‐degree atrio‐ventricular block with a heart rate of 40 to 45 beats/minute. A transvenous pacemaker implantation procedure was scheduled. The dog was premedicated with 10 µg/kg acepromazine and 5 mg/kg pethidine. A dose of 5 mg/kg ketamine and 0·2 mg/kg diazepam were used for induction and isoflurane in O₂ and a constant rate infusion of ketamine (20 to 30 µg/kg/minute) were administered for maintenance of general anaesthesia. Due to a twiddler's syndrome, the pacemaker had to be repositioned. For the second procedure, the same protocol was employed except for a lower dose of ketamine both for induction (3 mg/kg) and constant rate infusion (10 to 15 µg/kg/minute). Ketamine appeared to be useful for both management of anaesthesia and cardiac pacemaker implantation in the absence of a temporary pacemaker.     

Use of a programmable, 'physiological' cardiac pacemaker in a dog with total atrioventricular block (with some comments on complications associated with cardiac pacemakers)

A collie-cross dog with syncopal attacks associated with total atrioventricular heart block was successfully fitted with a programmable, ‘physiological’ pacemaker, employing atrial sensing and ventricular pacing leads. Transvenous placement of leads under sedation and local analgesia, followed by temporary pacing, then general anaesthesia for the fitting of a permanent pacemaker, offers advantages over epicardial pacing. The use of a ‘tined’ ventricular lead appears to reduce the risk of lead displacement.     

Suspected lily-of-the-valley (Convallaria majalis) toxicosis in a dog

Objective: To describe successful treatment of third-degree atrioventricular (AV) block using temporary noninvasive transthoracic pacing and placement of a permanent transvenous pacemaker in a case of suspected lily-of-the-valley ( Convallaria majalis ) intoxication in a dog.
Case summary: A 2-year-old neutered male Beagle weighing 17.8 kg was presented to the emergency service for treatment of bradycardia, vomiting, and lethargy. An electrocardiogram revealed third-degree AV block that was nonresponsive to atropine. Ten hours after admission, the dog became obtunded. Treatment initially consisted of temporary noninvasive transthoracic pacing and eventually placement of a permanent transvenous pacemaker. The initial history did not suggest that the dog had access to any known cardiotoxins. However, C. majalis , which contains cardiac glycosides, was identified within the dog's environment and the dog's serum did contain digoxin or an immunologically cross-reactive compound.
New or unique information provided: This is the first reported successful management of C. majalis toxicosis in a dog. Temporary noninvasive transthoracic pacing was used in the management of this case as a safe and effective bridge to permanent pacemaker implantation.     

Implantation of permanent transvenous endocardial pacemaker in a dog with atrioventricular block

A 10-year old male mongrel dog was presented to the University Veterinary Teaching Hospital with a two-month history of episodic syncope. Twenty-four hr Holter electrocardiographic (ECG) recording revealed frequent episodes of advanced atrioventriculer block with long periods of ventricular asystole. The cause of syncope was determined to be Adams-Stokes syndrome exhibited bradyarrhythmia. After the animal failed to respond to medical therapy, permanent transvenous pacemaker implantation was performed. Postoperative Holter ECG showed 100 beat per min programmed pacemaker rhythm, which indicated successful capture of the artificial pacing. The dog recovered smoothly from the operation and syncopal episodes completely disappeared. Six months after the surgery, no complications were observed and the dog's quality of life has dramatically improved.     

Temporary transvenous cardiac pacing in a dog with diltiazem intoxication

Objective: This case report presents the clinical findings of a dog with diltiazem intoxication and the utilization of temporary transvenous pacing for management of high‐grade second‐degree atrioventricular (AV) block with associated bradycardia and hypotension. Case summary: A nine‐year‐old spayed female Basset Hound, who ingested between 95 and 109 mg/kg of sustained‐release diltiazem exhibited clinical signs of cardiac arrhythmias, bradycardia, hypotension, mental depression and gastrointestinal (GI) upset. Bradycardia was present initially, then was followed by high‐grade second‐degree AV block with ventricular escape. Traditional medications to treat calcium channel blocker (CCB) intoxication, including atropine, calcium gluconate, dopamine and glucagon were initially successful in managing the cardiac rhythm disturbances and hypotension. Twenty‐two hours post‐ingestion, however, the dog became refractory to these medications following sedation for GI decontamination and a temporary transvenous pacemaker was placed. The dog was paced for 19 hours. Transvenous pacing effectively increased heart rate, which increased blood pressure into an acceptable range. The dog was successfully discharged from the hospital following treatment. New or unique information provided: The use of a temporary pacemaker should be considered an acceptable treatment for bradycardia, AV block and hypotension associated with CCB intoxication when conventional medical therapy fails.     

Transvenous pacemaker placement in a dog with atrioventricular block and persistent left cranial vena cava

The case reported herein describes the placement of a permanent transvenous pacemaker in an older dog with a previously undiagnosed persistent left cranial vena cava (PLCVC) and recent onset symptomatic third-degree atrioventricular (AV) block. On presentation the dog was found to have atrial flutter and third-degree AV block and echocardiography demonstrated evidence of chronic valvular disease and pulmonary arterial hypertension. The persistent left cranial vena cava was discovered via angiography when difficulties were encountered with pacemaker placement. Successful right ventricular pacing necessitated passage of the lead through the coronary sinus. The attendant complications in pacemaker placement in the presence of a PLCVC are well-described in man but, to the authors' knowledge, have not been described in companion animals.     

Permanent pacemaker implantation with transvenous electrode placement in a dog with complete atrioventricular heart block, congestive heart failure and Stokes-Adams syndrome

A permanent asynchronous pacemaker was implanted in a 2-year-old Shetland Sheepdog with complete heart block. Electrode implantation was via the transvenous method. One year after implantation the pacemaker unit began to fail. A new pacemaker, with a 7-year battery expectancy, was substituted for the original unit. The subject is still leading a normal life, 1 ½ years after the use of the pacemaker.     

Exploration of a third degree atrioventricular block by standard echocardiography, tissue Doppler imaging, and treatment with a cardiac pacemaker in a German wire-haired pointer

A nine-year-old intact male Drathaar was evaluated for syncope and extreme weakness, and was found to have a third degree atrioventricular (AV) block. As there were no biochemic, serologic, organic (thoracic radiographs, abdominal echography, standard and tissue Doppler echocardiographies) and histologic (interventricular septum biopsy) anomalies, the dog was treated with a permanently implanted cardiac pacemaker.     

Heart rate distribution in dogs with third degree atrioventricular block and rate responsive pacemakers

IntroductionIn dogs, single lead ventricular pacing, ventricular sensing, inhibition response, rate adaptive (VVIR) pacemakers are routinely used to treat third degree atrioventricular block. The objectives of this study were to investigate the heart rate distribution in dogs with VVIR pacemakers, and report changes when activity settings were adjusted.AnimalsEighteen client-owned dogs with VVIR pacemakers for third degree atrioventricular block.Materials and methodsThis observational study consisted of a review of medical records of dogs with VVIR pacemakers. For dogs with >50% of paced beats at the lower pacing rate, the activity daily living (ADL) and exertion responses were increased. Re-evaluations were performed after 6–12 months.ResultsHeart rate distribution similar to healthy dogs was absent for all dogs. In nine dogs, the ADL and exertion responses were increased to the highest level. Of these, three dogs showed no improvement in heart rate distribution; for two dogs, one with an epicardial pacemaker, several activity settings were adjusted and pacing at higher heart rates was observed at re-evaluation. Four dogs died or were lost to follow-up. Clinical signs had resolved for all dogs after pacemaker implantation.ConclusionDefault activity settings of VVIR pacemakers do not result in heart rate distribution equivalent to healthy dogs. Increasing the ADL and exertion response settings to the highest levels did not improve the pacemaker rate response. Further investigations into the role of dog size, generator positioning, pacemaker settings, and whether rate responsiveness is required for dogs' quality and quantity of life are warranted.     

Late cardiac perforation by a passive-fixation permanent pacemaker lead in a dog

CASE DESCRIPTION: A 12-year-old Miniature Dachshund with a history of permanent endocardial pacemaker implantation performed 7 weeks previously was admitted for routine dental prophylaxis. CLINICAL FINDINGS: Preanesthetic ECG revealed normal ventricular capture. Thoracic radiographic findings included caudomedial displacement of the endocardial pacemaker lead. Echocardiography revealed moderate chronic degenerative valve disease with moderate left atrial and ventricular dilation. After induction of anesthesia, loss of ventricular capture was detected. The dog recovered from anesthesia and had improved ventricular capture. The following day, surgical exposure of the cardiac apex revealed perforation of the right ventricular apex by the passive-fixation pacemaker lead. TREATMENT AND OUTCOME: A permanent epicardial pacemaker was implanted through a transxiphoid approach. Appropriate ventricular capture and sensing were achieved. The dog recovered without complications. Approximately 2 months later, the dog developed sudden respiratory distress at home and was euthanized. CLINICAL RELEVANCE: In dogs with permanent pacemakers and loss of ventricular capture, differential diagnoses should include cardiac perforation. If evidence of perforation of the pacemaker lead is found, replacement of the endocardial pacemaker lead with an epicardial pacemaker lead is warranted.     

Third degree atrioventricular block and sudden death secondary to acute myocarditis in a dog

Third degree atrioventricular (AV) block in dogs is thought to be most frequently characterized by non-specific fibrotic changes in the AV node. However, it may occur secondary to an undiagnosed inflammatory process. We report a case of third degree AV block in a dog, secondary to acute lymphocytic-plasmacytic myocarditis that resulted in sudden death. This dog had cardiac troponin I levels of 44.65 ng/mL (normal <0.11 ng/mL). The serum cardiac troponin I level was five times higher than any other AV block patient measured in our laboratory, and was also substantially higher than in dogs with chronic valve disease or dilated cardiomyopathy. The severe myocardial necrosis observed at necropsy correlated with the degree of cardiac troponin I elevation. This report suggests that measurement of cardiac troponin I may be an indicated test before pacemaker implantation in dogs with third degree AV block.     

Pacemaker implantation in a ferret (Mustela putorius furo) with third-degree atrioventricular block.

A 7.5-year-old castrated male ferret (Mustela putorius furo) was diagnosed with third-degree atrioventricular (AV) block. A monopolar epicardial pacemaker system was implanted, resulting in a regular, paced cardiac rhythm with third-degree AV block at 140 beats per minute. Over the next 2 months, the ferret developed anorexia, interstitial pneumonia, intermittent diarrhea, and hind-limb weakness and had a slow and progressive recovery. The ferret developed clinical signs of congestive heart failure 4 months after the surgery, resulting in its death 3 weeks later. Necropsy results attributed the death to cardiac failure due to extensive myocardial mineralization. To the authors' knowledge this is the first published report of surgical report of surgical pacemaker implantation in a ferret.     

Complete heart block associated with lupus in a dog

A 5-year-old Poodle-cross was initially presented for exercise intolerance and difficulty in chewing and yawning. Some months later it acutely developed lethargy referable to complete heart block. Further investigations before and after permanent pacemaker implantation demonstrated Coombs-positive immune-mediated haemolytic anaemia, presumptive masticatory myositis and hypoadrenocorticism, suggesting the possibility of multisystem auto-immune disease. A diagnosis of systemic lupus erythematosus (SLE) was made based on these findings and a positive anti-nuclear antibody titre. It was thought that immune-mediated destruction of cardiac conduction tissues was responsible for the development of atrioventricular conduction block. Glucocorticoid deficiency was corrected using cortisone replacement therapy. SLE was controlled successfully for 10 months using azathioprine monotherapy until signs, subsequently shown to be due to subacute bacterial endocarditis, resulted in the death of the patient. Lupus should be considered as a potential underlying aetiology in dogs that develop heart block.     

Malignant pheochromocytoma presenting as a bradyarrhythmia in a dog

Objective: To describe a case of atrioventricular block and syncope secondary to systemic hypertension in a dog with malignant pheochromocytoma. Case Summary: A 13‐year‐old spayed female mixed‐breed dog presented following an acute onset of collapse. The dog was hypertensive and had paradoxical high‐grade second‐degree atrioventricular block with concurrent syncope. Initial emergent therapy included a nitroprusside infusion for the systemic hypertension and vagolytic therapy for the bradyarrhythmia. A left adrenal mass was seen on abdominal ultrasound and was further characterized by MRI. Following medical stabilization with phenoxybenzamine and propantheline, a left adrenalectomy was performed. Histological diagnosis was consistent with a malignant pheochromocytoma. Following tumor removal there has been no further hypertension, atrioventricular block or syncope. Unique information provided: This is the first documented case of a malignant pheochromocytoma presenting as syncope secondary to hypertension induced atrioventricular block.     

Complete Heart Block in a Dog Seropositive for Borrelia burgdorferi: Similarity to Human Lyme Carditis

Lyme disease has been recognized in humans since 1975 when it was associated with an outbreak of oligoarthritis in children in Lyme, Connecticut. Erythema chronicum migrans (ECM) is a clinical marker for the human disease, which usually appears within 3 to 32 days after an infected tick bite. Lyme disease is caused by spirochete, Borrelia burgdorferi, which is vectored by the hard ticks Ixodes dammini or Ixodes pacificus in the United States. In humans, Lyme disease has been found to cause a variety of clinical syndromes including cardiopathy, neuropathy, dermatopathy, and arthropathy. Human Lyme carditis is characterized by varying degrees of atrioventricular (AV) heart block that usually resolve regardless of therapy. Lyme disease has been reported in the dog as an arthropathy. This article reports a case of complete heart block and myocarditis in a dog with a positive titer for B burgdorferi, in which clinical and pathologic findings were similar to those seen in human Lyme myocarditis.     

Use of a programmable, activity-sensing, rate-regulating Sacemaker in dog

A multi-programmable, single chamber pulse generator with automatic, activity-sensing rate regulation was successfully implanted into an eight-year-old crossbred dog with symptomatic third-degree atrioventricular heart block. Postoperative Holter monitoring confirmed appropriate activity-related changes in the ventricular rate.     

Syncope secondary to transient atrioventricular block in a German shepherd dog with dilated cardiomyopathy and atrial fibrillation

This case report describes transient atrioventricular block as the etiology for syncopal events in a 6-year-old male German shepherd dog with atrial fibrillation and dilated cardiomyopathy. The arrhythmia diagnosis was obtained via Holter monitoring. Medical treatment with a sustained-release preparation of theophylline, as an additive to the standard congestive heart failure treatment (benazepril, furosemide and pimobendan) may have contributed to temporary remission of the syncopal events. However, the congestive heart failure progressed and the dog was euthanized. Veterinarians should be aware of the possibility of transient atrioventricular block causing syncope in dogs with DCM and AF and should be careful in empirically lowering the ventricular response rate if these dogs present with syncopal episodes.     

Ventral abdominal, transdiaphragmatic approach for implantation of cardiac pacemakers in the dog

Surgical implantation of a sutureless myocardial electrode and pulse generator was performed in 18 dogs, using a ventral abdominal, transdiaphragmatic approach. Twelve dogs were greater than or equal to 10 years old. The 18 dogs weighed from 3 to 54 kg. Indications for permanent cardiac pacemaker implantation included complete (3rd degree) atrioventricular block, sick sinus syndrome, and sinus bradycardia. Few complications developed during or after surgery. One dog died during surgery from ventricular fibrillation, and hypertrophic cardiomyopathy was found at necropsy. Five dogs died 1 to 19 months after surgery (mean, 8.6 months) because of renal failure, hepatic cirrhosis, congestive cardiomyopathy, or idiopathic causes. Twelve dogs were alive 1 to 48 months after surgery (mean, 15.1 months). The surgical approach was used a second time in 3 dogs to replace the myocardial electrode wire and pulse generator 4, 16, and 26 months after surgery; technical complications were not associated with the second surgery in these 3 dogs. In 2 dogs that had initial pacemaker implantation via lateral thoracotomy, a transdiaphragmatic approach was used to replace the myocardial electrode lead and pulse generator 25.5 and 26 months after surgery. According to results of this study, the ventral abdominal, transdiaphragmatic approach for permanent pacemaker implantation in the dog is a simpler technique, with decreased surgery time, decreased time of tissue exposure, and decreased rate of infection, as compared with results described by investigators who used lateral thoracotomy or midline celiotomy and caudal one-third median sternotomy.     

Syncope associated with paroxysmal atrioventricular block an ventricular standstill in a cat

A four-and-a-half-year-old neutered male shorthair cat was presented with a three-week history of episodic fainting. Twenty-four hour electrocardiographic (Holter) recording revealed frequent prolonged episodes of complete atrioventricular (AV) block with ventricular standstill. The fainting episodes coincided with the longest periods of ventricular inactivity. A permanent transjugular pacemaker was placed to prevent further life-threatening episodes of syncope. Three months after discharge, the patient was re-presented with sudden onset dyspnoea associated with chylothorax and electrocardiography showed a third degree (complete) AV block. The pacemaker was reprogrammed in view of the third degree AV block and the chylous effusion was successfully treated by repeated thoracocentesis and long-term diuresis. However, the patient's general condition deteriorated progressively and the cat was euthanased five and a half months after implantation of the pacemaker.     

Results of pacemaker implantation in 104 dogs

OBJECTIVES: To document the outcome, survival and complications involved in pacemaker implantation in dogs in a retrospective study. METHODS: Case records for all dogs in which pacemaker implantation was performed were reviewed. RESULTS: A total of 104 dogs underwent pacemaker implantation. Dogs were presented with atrioventricular (AV) block (71), sick sinus syndrome (25) or vasovagal syncope (eight). Age at presentation varied from six months to 13 years with a median age of seven years and two months. The Labrador was the most commonly represented breed (17 cases). All but one dog survived pacemaker implantation, with 93 showing resolution of their clinical signs while 10 dogs showed intermittent residual signs. One-, three- and five-year survival estimates were 86, 65 and 39 per cent, respectively. Major complications after implantation were documented in 15 dogs and three of these led to fatalities. Minor complications were noted in 23 dogs. Sudden death occurred in six dogs three to 55 months following successful pacemaker implantation. CLINICAL SIGNIFICANCE: Transvenous pacemaker implantation was successful in reducing or eliminating clinical signs in over 90 per cent of dogs with third-degree atrioventricular (AV) block or sick sinus syndrome. In dogs with vasovagal syncope, six of eight dogs had greatly reduced frequency of collapse and two became asymptomatic. Although the procedure was associated with complications, these were rarely life threatening and good survival was documented in the majority of cases.