A veterinary cardiologist is a specialist in the diagnosis and treatment for pets with heart disease. As with human heart problems, this might include cardiac ultrasound, angiography, catheterization, ECG and Holter monitoring as well as a focused examination of the patient. Our cardiologist, Dr Marco Margiocco, is the only interventional cardiologist in Western Canada, meaning he has the ability to place pacemakers, repair heart defects and perform balloon valvuloplasties.

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Common indications for referring a pet to a cardiologist

  • Screening for heart disease prior to introduction of a pet into a breeding program
  • Pre-purchase screening
  • Evaluation prior to anesthesia
  • Evaluation of a newly or previously identified heart murmur or extra heart sound
  • Evaluation of a newly or previously identified arrhythmia (irregular heartbeats)
  • Cough
  • Increased breathing rate and/or effort (shortness of breath)
  • Exercise intolerance or weakness
  • Fainting episodes
  • Abdominal swelling

Before you come

During your first evaluation you should bring all pertinent medical records and previous diagnostics. Although it might be necessary to repeat some tests, this will help avoiding unnecessary duplication of previously performed tests.

Please also bring with you all medications your pet is currently receiving. It is also important that your pet receives all due medications the day of your visit.

Your primary veterinarian will provide us with the necessary information regarding your pet’s medical history, copies of recent blood work, recent radiographs (X-rays) and/or ECGs.

What to expect

During a typical visit you will first meet the Cardiology Technician, who will collect a detailed medical history and some basic data, such as your petʼs weight, body temperature and blood pressure. An Electrocardiogram (ECG or EKG) is also commonly done at this time. The cardiologist will then perform a physical examination and review all previous medical records and diagnostics. At this point an echocardiogram is performed in the majority of our patients. Other diagnostics, such as thoracic radiographs or blood work, may be discussed with you and can be performed during the same visit. After your petʼs medical work-up is completed, you will have a thorough discussion with the cardiologist regarding all the findings, including severity, prognosis, treatment options and associated costs. We will also plan follow-up care and detail symptoms to watch for, as well as address any questions or concerns you might have at the conclusion of your visit.

Typically the first appointment should last about 2 hours. We will make every attempt to stay on schedule; however emergencies are given priority, therefore occasional delays, although infrequent, are to be considered unavoidable in a busy clinical service.

Following your visit you and your primary veterinarian will receive a discharge summary that includes clinical findings, diagnosis, prognosis, treatment and follow-up recommendations.

Diagnostics

Following the initial examination several diagnostic procedures may be indicated. Our Cardiology Service offers the following diagnostics:

Electrocardiography (ECG or EKG)

ECGAn ECG evaluates the electrical activity of the petʼs heart. An ECG is an essential test for the diagnosis of rhythm disturbances (irregular heart beats) or conduction disturbances (i.e. so called “heart blocks”). It can also suggest the presence of cardiac enlargement. An ECG is obtained in virtually every patient referred for cardiac evaluation.

Holter monitor analysis

HolterA Holter monitor recording consists in attaching a small recording device to a harness or vest and connecting it with several wires to adhesive patches placed on the skin of the chest.
The pet is then discharged from the Hospital while the device continuously records the heartʼs electrical activity for the following 24-48 hours.

Holter

Sometimes rhythm abnormalities are intermittent and not necessarily present at the time of the visit, therefore prolonged monitoring of the heart rhythm increases the possibility of identifying arrhythmias.

A Holter test is also important in the evaluation of the response to anti-arrhythmic treatment and in the diagnosis of diseases of the heart muscle (called cardiomyopathies, such as Dilated Cardiomyopathy in Dobermans and Arrhythmogenic Right Ventricular Cardiomyopathy in Boxers).

Implantable Loop Recorder

Implantable Loop Recorder and remote control.

When a 24h Holter monitor recording is not sufficient to identify an intermittent arrhythmia or to provide explanations for infrequent clinical signs such as episodic weakness or collapsing episodes, an Implantable Loop Recorder (ILR) is used. It consists of a small device that is implanted just under the skin of the chest. Implantation can be performed with sedation and local anesthesia or with a brief general anesthesia. The device records the heart rhythm for up to 2 years. It can be programmed to start recording whenever the heart rate goes above or below a certain number of beats per minute, or when certain “pauses” in the heart rhythm occur. A little “remote control” is provided to the owner so to allow recording of the heart rhythm any time the patient appears not to be doing well (for instance when the patient appears weak, unwilling to move or exercise, unable to stand, or if a collapse occurs). The device can be “interrogated” like we would do with a pacemaker and all the information can be downloaded, analyzed and matched with clinical signs. The device is then removed once a diagnosis is reached and treatment efficacy is confirmed.

Thoracic Radiographs

Thoracic RadiographThoracic radiographs allow for the visualization of the heart shape and overall size and, most importantly, the lungs and their blood vessels. Thoracic radiographs represent an invaluable tool to help clarifying the causes for the respiratory signs a pet might present with, such as cough or shortness of breath. This is very important since these signs can be caused by lung or heart disease. Thoracic radiographs are also helpful to monitor the efficacy of medical treatment.

Echocardiography (or Cardiac Ultrasound)

An echocardiogram is an ultrasound study of the heart and blood vessels directly originating form the heart. It allows the cardiologist to obtain information on the anatomy and function of the heart, as well as on the direction, velocity and other characteristics of blood flow.

It is a completely non-invasive test that is usually performed without sedation on pets gently restrained on a custom-made table. The table has a window that allows the operator to “scan” the chest from the dependent side in order to obtain the best image quality.

The majority of dogs and cats are not shaved for an echocardiogram.

An echocardiographic study includes the acquisition of images (still frames and videos) obtained adopting several imaging modalities, each with its specific purposes and strengths. Below are examples of the most common imaging modalities.

  • 2D-echocardiography: used to obtain information on the anatomy and pump function of the heart

  • M-mode echocardiography: used to obtain accurate measurements and calculate some parameters of pump function
M-mode Echocardiography
M-mode Echocardiography
  • Doppler echocardiography: used to study direction, velocity and characteristics of blood flow through cardiac chambers, valves and blood vessels.

Tissue-Doppler Imaging
Tissue-Doppler Imaging
 

Spectral-Doppler Echo
Spectral-Doppler Echo

Fluoroscopy

Fluoroscopy is an X-ray-based imaging technique used to obtain real-time moving images of the internal structures of a patient. Angiography is a medical imaging technique used to visualize the inside, or lumen, of arteries, veins and heart chambers, performed by injecting a radio-opaque contrast agent into the blood stream and imaging using fluoroscopy. This injection is done through a long catheter, introduced into the circulation through a peripheral vein or artery, usually of the neck or hind leg, that allows for the delivery of contrast agent in a specific location within the cardiovascular system.

This procedure is called cardiac catheterization. Angiography allows for an accurate characterization of the anatomy and function of the heart and vessels. With the advent of echocardiography the need for diagnostic angiography was significantly reduced.

Nowadays angiography is used in selected patients affected by complex congenital heart defects and/or in patients that are amenable to catheter-based therapeutic interventions.

Cardiovascular Disease

The normal circulation

Heart drawing dog
Diagram courtesy of Mal Rooks Hoover, KSU
The heart consists of four chambers and four valves (please refer to the diagram). In a nutshell, the heart is comprised of two pumps in series. Itʼs main job is to keep the blood flowing within the circulation. The so called right heart (right atrium -RA and right ventricle – RV) receives the poorly oxygenated blood (venous blood) from the body and pumps it into the lungs. The lungs add oxygen to the blood and remove some waste products. This well oxygenated blood then returns to the left heart (Left atrium – LA and left ventricle – LV), that pumps it to the rest of the body.

Cardiovascular Disease (or heart disease)

Heart disease can be present at birth (congenital heart disease) or can occur anytime during a petʼs life (acquired heart disease). Heart disease can affect the cardiac valves or the cardiac muscle. Examples of valvular disease are Pulmonic Stenosis (a congenital defect) or Chronic Degenerative Mitral Valve Disease (an acquired disease). An example of disease of the heart muscle is Dilated Cardiomyopathy (an acquired disease).

The presence of heart disease can be suspected by your primary veterinarian based on your petʼs history, symptoms or physical examination. Furthermore, some breeds are known to be at an increased risk for the development of specific heart diseases. A heart murmur is a common finding that can allow your primary veterinarian to identify the presence of cardiac disease.

It is important to emphasize the difference between heart disease and heart failure.

Heart disease is present whenever there is a problem with the anatomy or function of a cardiac valve, cardiac muscle or one of the large vessels leaving the heart. However the body is often able to adapt to the presence of mild (and occasionally even moderate) heart disease. This condition is called a compensated heart disease. A pet with a compensated heart disease usually does not show any sign of the condition, with the exception perhaps of a heart murmur or other abnormal findings that your primary veterinarian might be able to appreciate. It is however very important to identify the presence of heart disease early in the compensated state, because it is at this stage that more can be done to improve your petʼs quality and quantity of life.

Heart Failure

Heart Failure can be defined as the incapacity of the heart to efficiently pump blood throughout the body so to meet its requirements in terms of oxygenation, delivery of nutrients and maintenance of normal pressures within the different chambers and blood vessels. Heart failure occurs when the body is no more capable to adapt to (i.e. to compensate for) the presence of heart disease. The typical consequence of heart failure is pooling of fluids in specific parts of the body. When the left side of the heart fails, fluids accumulate in the lungs and the pet shows respiratory signs. this is because the “wet” lungs cannot function properly. When the right side of the circulation fails, fluids accumulate in the belly and abdominal swelling or vague signs like inappetence, vomiting or diarrhea can occur. In both cases (left and right-side heart failure) exercise intolerance and variable changes in demeanor can be seen.

Thereby heart disease can be present without heart failure while heart failure implies the presence of heart disease.

Congenital Heart Defects

Are diseases of the heart and blood vessels that are present at birth or manifest shortly after birth. They originate from abnormal or arrested development of the fetal heart and vessels. Many, if not most, Congenital Heart defects (CHD) are heritable. Thereby it is important to identify pets with these conditions, not only because early diagnosis has the potential of resulting in the best chances of treatment or cure, but also because a pet with a suspect of proven CHD should not be use in a breeding program. Follows a short list of the most common CHDs in dogs and cats.

Patent Ductus Arteriosus

The Ductus Arteriosus is a normal fetal blood vessel that serves the purpose of redirecting blood away from the non-functioning lungs. The fetus does not breath, thereby the lungs are non the site where blood is oxygenated. The fetus, in fact, receives oxygen from the maternal placenta. After birth the Ductus Arteriosus should close. When this does not happen the ductus is said to be patent and the condition knwon as Patent Ductus Arteriosus (PDA). Pets with a PDA have a characteristic murmur that your primary veterinarian can identify. If untreated most pets develop heart failure early in life. A PDA can be closed with open-chest surgery or a catheter-based procedure (PDA embolization).

Pulmonic Stenosis

A stenosis consists in a valve that does not open normally. The consequence is that the heart has to pump harder to allow an adequate amount of blood to flow through the narrow opening. This causes the ventricle upstream to the stenotic valve to grow thicker, in order to become able to generate a higher pressure. This phenomenon is similar to the increase in muscle mass that physical exercise induces. Pets with PS have a loud murmur that can be identified during a physical examination. If a dog has moderate or severe PS and is left untreated sudden death or heart failure can occur. Pulmonic Stenosis can be treated with a catheter-based procedure (Balloon Valvuloplasty).

Subaortic Stenosis (SAS)

Subaortic Stenosis is a condition similar to PS, but it affects the left side of the heart. It is caused by a narrowing just below the Aortic Valve, hence the name Sub-aortic stenosis. A murmur is present, that would suggest further workup is needed. SAS is usually treated medically, because current surgical or catheter-based techniques are usually not indicated in most affected animals. However, in selected pets, balloon valvuloplasty can be considered.

Acquired Heart Diseases

Include a variety of heart disorders that occur and develop during the petʼs life. Below is a list of the most common acquired cardiac disease encountered in pets. Follows a short list of the most common acquired heart diseases in dogs and cats.

Chronic Degenerative Valve Disease (CDVD)

Is the most common acquired heart disease in dogs. It accounts for approximately 80% of all cardiac cases seen by veterinarians. It is common in small breed dogs (approximately less than 15Kg), such as Cavalier King Charles Spaniel, Dachshund, Pomeranian, Toy Poodles and others, but also occasionally seen in larger breeds (such as German Shepherd and Doberman). It typically affects the Mitral Valve that becomes “leaky”, and causes a heart murmur to become audible. This finding dictates the need for further workup. This condition is also referred to as Mitral Regurgitation (MR). If untreated, dogs with moderate or severe CDVD can develop left-sided Heart Failure. CDVD is treated medically with several drugs that have been proven to prolong survival and improve quality of life. Treatment is usually not instituted just when a heart murmur is identified. Currently available scientific literature suggests that medical treatment is needed (and beneficial) when the patient approaches the state of heart failure. Patients with CDVD are managed with periodic examinations in order to be able to identify early evidence of impending heart failure, ideally prior to the occurrence of overt clinical signs, and only at that time establish appropriate therapy. The two videos below are from a dog with severe Chronic Degenerative Valve Disease affecting the mitral valve. The videos show thickening of the mitral valve leaflets and severe regurgitation (green color-Doppler signal).


Dilated Cardiomyopathy

Dilated Cardiomyopathy (DCM)
Dilated Cardiomyopathy (DCM)
Dilated cardiomyopathy (DCM) is the most common disease affecting the heart muscle and is prevalent in large- and giant-breed dogs. It can also occur in medium-breed dogs, though this is less common, and is less frequently observed in cats. It represents a primary myocardial disease of unknown origin and, while there is no definitive cure for DCM, its signs and symptoms can be managed in many patients. Hearts affected by this condition become weaker and show a tendency to dilate. Early diagnosis through accurate screenings is important, especially in breeds at high risk, such as Doberman, Great Dane, Newfoundland, and Irish Wolfhound. The existence of a significant breed predilection suggests that DCM could be, at least in some cases, a hereditary disorder. Vigilant monitoring of the petʼs condition and consistent medication administration are crucial to maximizing your petʼs quality and length of life. Doberman Pinschers suffer from a particular form of DCM that carries a significant risk for sudden death secondary to arrhythmias. Particularly in this breed, annual Holter monitor recordings are highly recommended in order to identify patients candidates for medical prevention of sudden cardiac death.

This is a particular form of myocardial disease seen in Boxers. It is likely an inherited disease, but characterized by adult onset, and typically (but not exclusively) diagnosed in dogs around 6 years of age. Boxers affected by ARVC can develop fatal arrhythmias or heart failure. The best diagnostic tool is a Holter monitor recording, used to quantify the number of arrhythmias (particularly Ventricular Premature Contractions or VPCs) in 24 hours. Given the variable age at presentation we recommend that boxers start undergoing annual Holter monitoring at 3 year of age. If a Holter shows several VPCs, and echocardiogram becomes necessary at that point. Diagnosing a Boxer with ARVC is important in order to establish an antiarrhythmic therapy with the intent of reducing the risk of cardiac death due to arrhythmias but also because dogs with ARVC should not be used in a breeding program.

Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy (HCM) is another primary myocardial disease of unknown cause, that affects cats and, less commonly, dogs. It causes progressive and unexplained thickening of the wall of the ventricles, particularly the left ventricle, that reduces the ability of the heart to accommodate the blood that returns from the lungs and the rest of the body. It is common in Main Coon, Ragdoll, Persian, but also seen in Domestic Shorthair cats and other breeds. Although not completely know, the cause is hypothesized to be genetic, as recently demonstrated in some Main Coon, Ragdoll, and other breeds. A murmur may or may not be present. More consistently severe cases are characterized by the presence of a gallop heart sound your primary veterinarian might be able to auscultate. Treatment is medical and consists of interventions aiming at improving cardiac function and reducing the severity of the signs of congestion. Cats affected by HCM can also be at risk for arrhythmias and the formation of a clot within the circulation, called a Thromboembolism.

Arterial Thromboembolism

A devastating complication of HCM in cats, Arterial Thromboembolism (ATE) typically manifests as sudden onset pain and loss of control of one or both hind limbs. Occasionally a front limb is affected and or other arteries, such as those providing blood to the kidneys or the intestine. Left atrial enlargement favors blood stasis and thereby formation of clots in the heart (called thrombi). These thrombi can leave the heart and travel along the aorta, finally lodging in and obstructing, partially or totally, the vessel. This is an emergency situation and you should see your primary veterinarian or an emergency service as soon as possible. Medical management is usually aimed at controlling pain and discomfort, providing supportive care, and treating heart failure if present. Medical and interventional attempts to directly reduce the obstruction have not been consistently rewarding and therefore are not adopted routinely. Cats with moderate to severe cardiac disease are commonly treated preventatively with drugs that reduce the tendency of the blood to clot within the circulation.

Systemic Hypertension

Elevated blood pressure is a relatively frequent, and potentially under-appreciated problem in pets. Blood pressure can be measured with a technique similar to the one used in human medicine. Blood pressure is measured in all patients referred to CWVS as part of our routine evaluation. High blood pressure, known as Systemic Hypertension, causes serious damages to many organ, mainly the heart, eyes, brain and kidneys. The identification of patients with elevated blood pressure is instrumental in preventing the onset or progression of these damages. Systemic hypertension is commonly cause by other chronic diseases that can be frequently managed.

Pulmonary Hypertension

Elevated pressure within the pulmonary circulation is known as Pulmonary Hypertension. It is apparently an increasingly diagnosed condition among pets and can be managed with medical approaches. The diagnosis is primarily echocardiographic and consists of a thorough Doppler study of the blood flow within the right side of the heart, the chambers (right atrium and right ventricle) that send blood into the pulmonary vessels. Mild or moderate pulmonary hypertension frequently complicates cases of Chronic Degenerative Mitral Valve Disease. Severe forms of pulmonary hypertension are seen in dogs affected by respiratory diseases, Heartworm Disease, or as a primary disorder of unknown origin.

Arrhythmias

Irregular heart beats originate from abnormalities in the spontaneous cardiac electrical activity. Arrhythmias are can be suspected during a physical examination and are diagnosed with an ECG and/or a Holter. Cardiac arrhythmias can be secondary to heart disease or diseases of other organs of the body. Disorders of the spleen and gastrointestinal tract frequently cause arrhythmias. In the occasional patient a cause for arrhythmias cannot be identified, in this case the arrhythmia is said to be primary or idiopathic. Arrhythmias can be serious and life-treatening, so to necessitate immediate treatment, or more benign, so to only require monitoring. Antiarrhythmics are the drugs used to treat arrhythmias or to prevent their degeneration into a more serious arrhythmia. These drugs are potentially toxic and must be used with caution and knowledge of their applications and side effects.

Medical Management of heart failure

Heart failure (HF) is treated with a multiple drugs approach in pets. There are several goals in the medical treatment of HF. Based on the definition of Heart Failure the most important intervention consists of the use of diuretics, drugs that increase the amount of water and salts eliminated in the urine.

The most common diuretic is furosemide, either oral or injectable, depending on the specific situation. Other drugs commonly used are the so called ACE-inhibitors, of which Enalapril and Benazepril are among the most widely available products. These drugs help reducing the potential side-effects of chronic diuretic therapy, and have been proven to prolong survival and quality of life in many situations. Another diuretic that is commonly prescribed is Spironolactone. Also this drug has the potential of improving quantity of life on selected patients.

Digoxin is an old drug that still has its unique role in the treatment of pet in heart failure, especially when a particular arrhythmia, known as Atrial Fibrillation, is present. In the past decade Pimobendan has become an important addition to the multi-drug approach to HF in dogs, and less commonly in cats. Pimobendan has been proven to prolong quality and quantity of life in dogs with decompensated Mitral Regurgitation.

It is important to emphasize that current knowledge suggests that all these medications are indicated exclusively in severe cases of heart disease in which HF is present or impending.

Interventional Cardiology

Minimally invasive procedures have been developed over the past decades to treat or palliate several cardiovascular disorders. These interventions are performed under general anesthesia and under fluoroscopic guidance (see Angiography). Long catheters are introduced through peripheral veins or arteries and reach the heart in order to allow the operator to modify anatomic structures or deploy special devices. The most common indications for a catheter-based procedure are outlined below.

Pacemaker Implantation

Thoracic radiograph in a dog carrier of a permanent pacemaker
Thoracic radiograph in a dog carrier of a permanent pacemaker
A pacemaker is used to keep the heart beating regularly at a normal heart rate.

Pacemakers are applied to improve quality and quantity of life in pets with abnormally slow heart rates. Today’s pacemakers are small and are inserted under the skin in the neck region. The pacemaker lead is advanced through a vein in the neck down into the heart.

Pacemakers can communicate through the skin with a computer. The interrogation is performed by placing a wand over the area where the pacemaker is located (see image below).

ECG in a dog with Third Degree Heart Block Notice the slow heart rate (number of large waves)
ECG in a dog with Third Degree Heart Block Notice the slow heart rate (number of large waves)
 

Same dog as above after pacemaker implantation Notice the increased heart rate (i.e. increased number of large waves)
Same dog as above after pacemaker implantation Notice the increased heart rate (i.e. increased number of large waves)
Interrogation of a pacemaker.

 

Patent Ductus Arteriosus Occlusion

Thoracic radiograph in a dog treated for PDA with an ACDO. The device is visible at the base of the heart.
Thoracic radiograph in a dog treated for PDA with an ACDO. The device is visible at the base of the heart.

Patent Ductus Arteriosus is the most common congenital heart defect in dogs. Although open-chest surgery represents a safe and effective treatment for the condition, several minimally-invasive techniques to close this abnormal vessel have been developed and evaluated over the past years. Currently the Amplaz® Canine Ductal Occluder (ACDO®) represents the device of choice at CWVS. The procedure is performed with access through the femoral artery and the device is deployed within the ductus via a catheter.


Video illustrating the deployment of an Amplaz® Canine Ductal Occluder for the treatment of a Patent Ductus Arteriosus in a dog

Balloon valvuloplasty

Catheters with inflatable balloons at their tips can be used to stretch narrow orifices with the intention of improving blood flow and reducing the pressure that builds up before such an obstruction. This technique is commonly used to treat Pulmonic Stenosis (PS). During this procedure, catheters are introduced through the jugular vein in the neck and a balloon catheter is passed through the stenotic valve and inflated several times to improve its opening. Good results can be achieved in many patients.

Video illustrating a balloon valvuloplasty in a dog affected by Pulmonic Stenosis

Cardiology Team