Dogs
Pacemakers are now commonly available for dogs PDF  | Print |  E-mail

Many people know someone who has had a pacemaker implanted for a cardiac rhythm disturbance. Like so many treatments, this has now made the switch from human to veterinary medicine and pacemakers are widely available for implantation into dogs that would otherwise be reliant on less effective drugs.

What is a pacemaker?

A pacemaker is an electronic device for use in certain cases of heart disease to assume the functions of the natural cardiac pacemaker. The first pacemaker to be implanted in a human was in 1957, the first dog to have a pacemaker fitted was in 1968. Since then, the implantation technique has developed so that a pacemaker can now be implanted by feeding it up a peripheral vein to the heart, rather than via open chest surgery.

When is a pacemaker required?

Pacemakers are useful in the treatment of a slower than usual heart rate (bradyarrhythmia) that causes symptoms in the patient. These types of rhythm disturbances are poorly responsive to drugs.

The 2 most common types of bradyarrhythmia in dogs are:

1) Third-Degree Atrioventricular Block
2) Sick Sinus Syndrome

Dogs with either of these conditions usually have a history of a slow heart rate, exercise intolerance, lethargy and sometimes collapse (syncope). Some dogs with third-degree atrioventricular block may already have signs of congestive heart failure, such as fluid in the abdomen (ascites) and fluid between the lungs and chest wall (pleural effusion).

What is required for diagnosis?

A complete baseline blood profile, including hematology and biochemistry, should always be conducted to rule out concurrent disease.

Chest xrays often show an enlarged heart, and are useful to rule out primary respiratory disease.

Ultrasound is used to assess the contractility of the heart muscle, the dimensions of the heart chambers and the function of the valves.

The most important of all diagnostic tests is electrocardiography (ecg). This measures the electrical pulses in the heart itself, so is the most useful for studying rhythm disturbances.

How is a pacemaker fitted?

The dog is put under general anesthetic, taking care to maintain circulation and ventilation as best possible during the procedure. Sometimes a temporary pacemaker is placed via a leg vein, from induction of anesthesia until the permanent one is implanted.

The permanent pacemaker is fitted via a lead in the right jugular vein in the dogs neck. The lead is passed all the way down into the right ventricle of the heart. Once in place, the lead is connected to the pulse generator and the heart is paced as necessary. A pulse generator is implanted under the skin on the right side of the neck. Once implanted, the pacemaker can be interrogated to find out information about sensing and pacing thresholds. The heart rate can be set according to the heart disease present.

Is there much postoperative care?

A bandage is placed around the neck for 7 days following surgery. Dogs should be kept calm for the 48hrs following surgery, the anti anxiety drug acepromazine is sometimes prescribed for this purpose. Antibiotics and painkillers are given for a week or so after the implantation.

What about longer term aftercare?

Aftercare of pacemaker dogs is vital. Animals must be kept quiet for 28 days after implantation to allow the lead to become imbedded in the heart wall. If the lead becomes dislodged the pacemaker with fail, with potentially disastrous results.

Regular follow up appointments with the cardiologist are very important. Stitches are removed 10 days after the procedure, with further appointments at 4 week intervals for several months.

Summary

Whilst for many uninsured pets pacemakers might not be affordable, technological advances mean they are becoming cheaper and more widely available. Although implantation is considered a high risk procedure, complications rates are low and the severity of the disease means it is the treatment of choice.

Pacemakers allow many dogs to return to their normal day to day activities, and most of them can enjoy a relatively normal life expectancy.

About the Author

Dr Matthew Homfray is one of the veterinary pet experts at www.televets.com. Our dedicated community of caring pet experts are waiting to offer you free advice, second opinions and support.
 
Second hand pacemakers power-up ailing pets PDF  | Print |  E-mail

You can't take a pacemaker out of one human and replant it in another, for fear of what medical science refers to technically as "cooties."

Dogs, however, are not so particular.

Margie Leja of Dearborn Heights lost her mother-in-law in July. That's not "lost" as in wandered off, but rather lost in the sense that we're not built to last forever, and Genevieve wore out at 90.

Leja adored Genevieve, who bowled and drove until she was 85. "A wonderful mother-in-law," she says, and someone who's missed.

Leja also adores dogs, and those two passions are now connected by something Genevieve donated after her passing:

The little device that occasionally jump-started her heart.

At the request of the family, the funeral home removed her pacemaker and sent it to the veterinary college at Michigan State University. There, if they haven't done so already, surgeons will redeposit it beneath the fur of an ailing animal, most likely one with a waggable tail.

The surgery goes for $2,000 or so, says veterinarian and associate professor Bari Olivier, a deep discount compared to the price at most places that do the work. The pacemaker itself, $7,000 on up at your local Bed, Bath & Surgical Devices, is free.

"It's such a fantastic gift that can be passed on," says Leja, 63, "and nobody knows about it." Or at least, most people didn't. But now more of them will.

Fido stands to benefit

Today's pacemakers are about the size and weight of an Oreo.

At MSU, the vast majority of them go to the dogs, simply because dogs are more likely than other animals to suffer from what's known as third-degree heart block. An experienced surgeon like Olivier can insert one in as little as an hour. Place the device along the neck, slide a wire down the jugular vein, and a poodle with a pulse rate of 20 to 40 beats per minute will be back up to 80-100 before the anesthesia wears off.

Some of them are donated new by manufacturers like Medtronic. Most, however, come gently used, and without them, "we would have a serious problem," Olivier says. MSU performs up to 30 procedures annually, more than twice as many as a few years ago, and the number might well go up if more pacemakers were available.

Removing them from donors is easy and free. They have to be snared by a mortician anyway if there's a cremation, lest they explode or expel unpleasant things like mercury. Just ask, Olivier says, and most funeral homes will gladly ship them to East Lansing.

Can't take it with you

Leja first heard of the program from a funeral director 20 years ago, when her dad died. As someone whose present herd includes a greyhound and two beagles, all rescued, she was immediately intrigued.

About three weeks later, the veterinary school dropped her a note. "They said my father's pacemaker was used for a seeing-eye dog whose family would never have been able to buy one," she says.

That was all she needed to know, and enough to make her want to spread the word. It's the easiest way imaginable to be a buddy to a bulldog or a saint to a St. Bernard.

This article appeared in the Detroit News and was written by This e-mail address is being protected from spambots, you need JavaScript enabled to view it . Please visit this site
 
Pacemaker Implantation in a Boxer PDF  | Print |  E-mail
Pacemaker Implanatation In A Boxer.

A very interesting document written by renowned animal cardiologist Nicole Van Israel concerning a pacemaker implantation in a 6 year old male boxer called Murdo. The following is the article which is reproduced here courtesy of Dr Van Israel - Please visit Dr Van Israels site Here, and please view all of her incredible papers Here.

A huge thanks from PWP to Dr Van Israel for taking the time to respond to our emails and granting us permission to direct you to her work. Below is an extract from one of her articles which can be downloaded in full, in PDF format HERE.

PRESENTING HISTORY
Murdo is a six-year-old male neutered Boxer presented for investigation of a bradycardia noticed at a pre-anaesthetic check when the intention was to remove an epulis. The dog was completely asymptomatic and there was no previous history of illness.

CLINICAL EXAMINATION
On presentation Murdo was overweight (36 kg; ideal weight 32 kg) but bright, alert and responsive. On clinical examination his mucous membranes were pink and his capillary refill time was less than 2 seconds. He seemed fully hydrated. Multiple epuli were visible in his mouth. No jugular distension was noticed. A strong and regular apex beat was palpable and no precordial thrill was felt. Abdominal palpation, although difficult because of the dog’s obesity, was unremarkable. All lymph nodes were within normal limits.All his extremities were nicely warm. His pulses were strong and without any deficits.
On auscultation a very regular heart rate was audible.The heart rate was 60 BPM. No murmur was audible. The lungs sounded unremarkable. Rectal temperature was 38.5°C.

PROBLEM LIST AND DIFFERENTIAL DIAGNOSIS
Regular bradycardia Sinus bradycardia
Physiological
•    in very fit animals
•    in animals with increased vagal tone (brachycephalic breeds)
•    sleep
Pathological
•    hypothermia
•    hypothyroidism
•    hyperkalaemia
•    CNS disease, increased intracranial pressure
•    upper airway obstruction
•    gastro-intestinal (obstruction)
•    urinary (obstruction)
Pharmacological
●     tranquilliser, anaesthesia, digoxin, ß-blockers, morphine
Third degree AV-block
•    Infiltrative disease (neoplasia, inflammation)
•    Idiopathic fibrosis
•    Myocardial infarction
•    Hyperkalaemia
•    Lyme disease
•    Bacterial endocarditis
•    Associated with congenital defects (aortic stenosis, ventricular septal defect)

DIAGNOSTIC WORK-UP
The dog was admitted to the hospital for electrocardiography, blood work, thoracic radiography and colour flow Doppler echocardiography.

ECG
A 12-lead ECG confirmed the presence of third degree
AV-block with a ventricular escape rhythm of 60 BPM.
The P-wave rate was 120 per minute (Fig. 1).


Fig. 1: Six-lead ECG showing third degree AV-block with an escape rhythm at 60 BPM (50 mm/s; 1 cm=1 mV).

Atropine response test
An atropine response test (atropine 0.02 mg/kg IV; in
normal animals one can expect a 50-100% increase in
heart rate depending on the initial heart rate) increased the
P-wave rate but not the ventricular escape rate.

Lab-work
a. Haematology (Table 1)
Haematology was unremarkable.


b. Biochemistry (Table 2)
The biochemistry showed the presence of a marginally
elevated cholesterol level.T4 levels were within normal
limits. Mildly increased urea and creatinine were
consistent with a mild prerenal azotaemia




The Vertebral Heart Score was 12.5.There was sign of mild R-sided cardiomegaly.The great vessels (aorta, pulmonary artery and caudal vena cava) and the pulmonary vasculature were within normal limits. The pleural space and the lung fields were unremarkable.

Fig. 2: Right lateral thoracic radiograph (expiratory film):
rounding of the cranial border of the cardiac silhouette.The
lung fields are clear.

Colour flow Doppler echocardiography
All chambers measured within normal limits. Posterior wall and interventricular septal wall thickness were within normal limits in diastole. The fractional shortening (FS) as indicator of myocardial contractility was mildly increased (FS53%).
A hyperechoic area was visualised in the lower part of the interatrial septum (Fig. 3). There was no sign of valvular insufficiency.The velocity across the aorta and pulmonary artery were within normal limits.


Fig. 3: Right parasternal long-axis view showing the
hyperechoic area in the interatrial septum (la: left atrium; ra:
right atrium).

FINAL DIAGNOSIS
Idiopathic third degree AV-block.
 
TREATMENT
The dog was pre-medicated with acepromazine (ACP®, C-Vet; 0.0125 mg/kg) and pethidine (0.5 mg/kg; Martindale) intramuscular. Prophylactic antibiotics (cephalexin, Kefzol®, Lilly; 20 mg/kg IV q 8 hrs) and analgesia (carprofen, Rimadyl®, Pfizer; 4 mg/kg IV) were administered. General anaesthesia was induced with thiopentone IV (Thiovet®, C-Vet; 412 mg) and maintained with isoflurane/O2 (Isoflo®, Mallinckrodt). Under fluoroscopic guidance a bipolar lead (Bipolar Endocardial Lead,Porous tip,Tined;Guidant®, Basingstoke UK; Fig. 4) was implanted in the right ventricle via the left


Fig. 4: Detailed view of the end of a tined pacemaker lead.

jugular vein. The whole procedure was monitored electrocardiographically. The bipolar lead was first connected to an external temporary pacemaker. Once the position of the lead established (pacing threshold less than 1 mA) it was tunnelled subcutaneously and attached to the pacemaker device. The permanent pacing generator (Pacesetter® VVI system) was implanted subcutaneously cranial to the left shoulder.The rate was pre-programmed at 70 BPM. A thoracic radiograph (Fig. 5) was taken for a permanent record of lead placement. The wounds were closed routinely and a protective bandage was applied.


 
Fig. 5: Right lateral thoracic radiograph showing correct placement of the pacemaker lead in the right ventricle.The lead has an S-bend to allow movement of the neck without putting strain on the lead.

The dog recovered well from anaesthesia, stayed in the Intensive Care Unit for 48 hours and was hospitalised for another three days. After a last technical check at the human hospital, he was discharged with a one-week course of antibiotics (20 mg/kg cephalexin BID PO, Ceporex®;Virbac). 

OUTCOME
Three years post-intervention Murdo is still doing very well and the pacemaker seems to be pacing at all times (Fig. 6).


DISCUSSION
Third degree AV-block is an uncommon arrhythmia in the dog. It has been associated with several other conditions (Table 4). In this case no underlying cause could be determined. Dogs with third degree AV-block are usually middle-aged suggesting a degenerative change in the conduction system. Degeneration of the conduction system is common in many breeds. It has been stated that German Shepherd Dogs and Cockers Spaniels are over represented and there is one report where Dobermanns are the most common breed.

 

The importance of the hyperechoic area in the inter-atrial septum remains unclear. Hyperechogenicity is seen with fatty infiltration and collagen changes. Fibrosis and infiltrative disease are known aetiologies for third degree AV-block. Only a histopathological section might give an explanation.
Although no acetylcholine-esterase receptor antibodies were determined, myasthenia gravis was excluded as a possible aetiology on the basis of the complete absence of clinical signs. Borrelia burgdorfi antibody titres were ignored because Lyme disease is not endemic in the area where the animal lives.
Full bloodwork excluded electrolyte imbalances as a possible reason for the third degree AV-block. The azotaemia was, despite the lack of urinalysis (urine specific gravity), thought to be prerenal secondary to a decreased cardiac output due to the bradycardia.The renal perfusion and renal function parameters (urea, creatinine) should return to normal after pacing but no follow-up data are available in this case regarding this aspect. The mildly increased cholesterol levels could have been suggestive of hypothyroidism but T4 levels in the higher range of normal made this very unlikely.
Most animals with third degree AV-block have exercise intolerance as the main presenting sign. Dogs may also be presented because of syncope or congestive heart failure. In this case the dog was completely asymptomatic. It should be appreciated that third degree AV-block may not cause clinical signs unless there are periods with inadequate escape activity. Most healthy dogs can maintain a normal arterial blood pressure at rest with a heart rate as low as 40¬60 BPM.The ECG confirmed the presence of a relatively stable escape rhythm at 60 BPM. Considering the rate, the escape rhythm was thought to be originating from the subsidiary pacemakers in the bundle of His and the AV-node was the most likely site of the block.
On clinical examination no heart sounds (4th heart sounds) consistent with atrial contraction were noticed, partly due to the broad-chested nature of the dog and his obesity.The bouncy nature of the dog also made prolonged auscultation very difficult.The slow regular rhythm and the absence of a sinus arrhythmia were suggestive of an abnormal rhythm in this dog.The typical cannon A-waves, generated when atrial contraction occurs when the mitral valve is closed, were not observed in this animal’s jugular veins.
The radiographic changes were consistent with breed variation. Boxers have an increased VHS compared to other dogs (normal for Boxers 10.3-12.6v). As well as that bradycardia causes prolonged filling and can cause apparent cardiomegaly (diastolic frame). The echocardiographic changes (increased FS) in this case were typical of a hyperdynamic ventricle (Frank Starling mechanism).
Since the atropine response test was negative (atropine will usually increase the atrial rate without changing the ventricular rate because the ventricles are supplied mainly by sympathetic fibres and have few parasympathetic fibres) and since there was no increase of the heart rate after theophylline treatment a pacemaker implantation was the only alternative.



Fig. 7: Different types of pacemakers available with nomenclature.

Fig. 7 explains the three or five letter abbreviations used for describing the capabilities of the pulse generator.The first letter stands for which chamber is paced (V for ventricle, A for atrium,...), the second letter for which chamber is sensed (ditto), the third letter indicates the mode of response (I for inhibitory, T for triggered,...), the fourth letter shows that the device has multiple parameters that can be programmed and the final letter denotes if an anti¬tachydysrhythmia function is present.

The procedure and the post-operative period passed uneventfully in this case. However, one has to be aware that major (Table 5) and minor complications (Table 6) can occur. Survival analysis in the largest retrospective canine pacemaker study published revealed 1-, 2-, 3- year survival rates of 70, 57 and 45 % respectively.



REFERENCES AND FURTHER READING
TILLEY, L. P. (1992) Third degree AV-block. In: Essentials of canine and feline
electrocardiography, 3d Ed, Lea & Febiger, Philadelphia. Pp 175-178.
KITTLESON, M. D. (1998) Diagnosis and treatment of arrhythmias. In:Small
Animal Cardiovascular Medicine. Eds Kittleson & Kienle, Mosby, Inc, St-Louis.
Pp 489-492
BONAGURA, B. D. (1999) Cardiac pacing. BSAVA Congress synopses,
specialist session.
FOX, SISSON, MOISE (2000) Textbook of canine and feline cardiomyopathy
(W. B. Saunders).
OYAMA, SISSON, LEHMKUHL (2001) Practices and outcome of artificial
cardiac pacing in 154 dogs
(CANPACERS Study). JVIM; 15: 229-239.
© Illustrations Nicole Van Israël.





 
 
6 months after implantation - all is well! PDF  | Print |  E-mail
Another milestone has been reached, It has now been 6 months since Charlie the Pacemaker Dog was implanted. After some initial trial and error with the device voltage outputs, and jugling of medicine dosages, it seems we have finally got the management parameters right. He is doing extremely well and is just as rambunctious, destructive and playful as he was when he was a puppy. You can see an example of how well he is doing in the following video of him playing. Not bad for a 13 year old!



Charlie - The Pacemaker Dog hard at play.
 
 
Canine receives pacemaker - a first for U.S. Customs PDF  | Print |  E-mail

In late February, the Brownsville, Tex., Canine Enforcement section received a call from their local veterinarian. Dr. Sherri Wooding needed to see Customs canine "Dik" in her office for some additional lab work to follow-up his annual physical. The telephone call began a long and bumpy ride for Dik, a Belgian Malinois, and CEO Amador Zapata, his handler of five years.

Diagnosis
Dik underwent testing at the Brownsville Veterinarian Hospital and at Lackland Air Force Base in San Antonio, Tex. The specialists at the Military Working Dog Veterinary Clinic at Lackland confirmed that Dik had Cardiomyopathy, a chronic disorder of the heart muscle with a mild right-sided heart failure. Dik's heartbeat was one-third of what it should have been. Doctors advised CEO Zapata that Dik could no longer work and would need to be retired.

Dik with his handler CEO Amador Zapata.
Photo Credit: SCO Eugene Moriarty
Dik with his handler CEO Amador Zapata.

A possible solution
Dr. Wooding was not giving up on Dik-she researched his illness and made telephone calls to other veterinarians and specialists. She contacted Dr. Matt Miller, Associate Professor of Cardiology, at Texas A&M University, a world-renowned university for veterinarian medicine. Dr. Wooding, along with the Brownsville Animal Hospital and Texas A&M Veterinary Medical Center, explored alternative ways to give Dik the best care possible. The solution to Dik's illness? A pacemaker inserted into his neck to support his ailing heart and possibly give him a new lease on life.

On the afternoon of April 17, Dr. Wooding told Dik's handler that Texas A&M wanted to examine the dog to determine if he was a candidate for the procedure. Dik and Zapata left Brownsville at 3 a.m. the next morning for the 8-hour trip to Texas A&M.

Surgery
The news was good: Dr. Sonya Gordon, Assistant Professor of Cardiology, and graduate veterinary student Tricia Latimer decided that Dik was, indeed, a candidate for a pacemaker. Dik's strong physical condition ensured that the pacemaker would not only extend his life, but that it would also allow him to resume his duties as a narcotic detector dog. Dik was taken into the operating room that same day, and three hours later his pacemaker was in place and working. Clinic Director Hank Reinheart informed CEO Zapata and Brownsville Canine Enforcement that the Texas A&M Veterinary Medical Center would cover all of the expenses.

Speedy recovery
Dik returned to duty on May 28, and on May 30, he alerted to 84.37 pounds of marijuana hidden inside the tires of an automobile. Dik has an impressive record for the Port of Brownsville. His seizures total over $15 million worth of narcotics and property.

This story originally appeared on U.S. Customs Today