There are several non-invasive cardiac tests that veterinary cardiologists utilize on a daily basis to diagnose heart disease in animals and develop appropriate treatment and follow-up recommendations. Your pet may not require all of these tests – after a thorough cardiovascular examination by both your family veterinarian and veterinary cardiologist, a tailored diagnostic plan will be made. We have provided some additional information regarding the tests that may be performed below. Each cardiac consultation with Dr. Orr will include a complete cardiovascular physical examination, blood pressure and a single lead ECG. Generally an echocardiogram will also be performed in most cases.
Echocardiography
An echocardiogram is a non-invasive cardiac ultrasound. It allows for real-time imaging of the heart to evaluate heart size and function. There are several modes that are used during a complete echocardiogram – 2D refers to the real time image where we can see the heart contracting and relaxing in real-time. Colour Doppler allows us to follow the flow of blood through the heart, identifying any leaky valves or turbulent blood flow. Spectral Doppler allows the measurement of speed of blood flow through the heart – this can then be used to estimate cardiac pressures. In recent years, there are have been several advances in the field of echocardiography including tissue Doppler imaging (TDI) and speckle tracking – these modalities allow cardiologists to assess heart function in more detail than ever. East Coast Veterinary Cardiology uses the newest and most advanced portable cardiac ultrasound called the Vivid iq. Although this unit is small, it performs just as well as a larger stationary machine.
We’ve included some examples of various studies in animals so you can see what we see with echo!
This is an echocardiogram from a cat with Hypertrophic Cardiomyopathy, the most common form of acquired heart disease in the cat.
In this video, we are focused on the left sided of the heart with the left atrium and left ventricle in view. The left ventricle is very thickened – this is called concentric hypertrophy. We can also see the valves opening and closing in this loop – the mitral valve separates the left atrium and ventricle. We can also assess the aortic valve motion which is the exit valve from the left ventricle.
This is an echocardiogram from a Cavalier King Charles Spaniel with Mitral Valve Disease. Did you know this disease affects almost 90% of Cavaliers by the time they are 10 years of age?
In this video, we are able to assess all four heart chambers – the right side of the heart is in the top portion of the video (near-field) while the left side is the lower two chambers (far-field). The left side is very enlarged compared to the right side because of this dog’s mitral valve disease. We can see that the mitral valve (separating the left atrium from ventricle) is very thickened, irregular and a portion of the leaflet is prolapsing into the left atrium with every heart beat. This dog likely tore a chordae tendinae, a thin attachment structure that helps tether the mitral valve leaflets in place.
This is an echocardiogram from a dog with Dilated Cardiomyopathy. This is a condition where the heart dilates secondary to a weakening of the heart muscle.
In this video we are focused on the left side of the heart which is dilated – this image shows the utility of colour Doppler – the colour tells us about direction and speed of blood flow. In this image, there is a leak (back-flow) across the valve called mitral regurgitation – it is represented by the blue/green colour that is flowing back into the left atrium. Mitral regurgitation is common in dogs with DCM as the dilation stretches the mitral valve leaflets, pulling them apart. This prevents the formation of a perfect seal and a leak develops.
This video is from a dog with Heartworm Disease. This dog was rescued from the southern USA and moved to Ontario, Canada. He presented for weakness and collapse. An echocardiogram revealed a mass of worms in the right atrium, obstructing the flow of blood across the tricuspid valve (called Caval Syndrome). In this video, you can see the mass of worms (the parallel lines) that are filling the right atrium.
This dog had an emergency, non-invasive surgery to remove the worms from his heart. You can see the worms we removed here!
Although heartworm disease is not terribly prevalent in Atlantic Canada, we still recommend annual heartworm prevention and this is why! It is far easier to prevent an infection than to treat it.
This was an echocardiogram from an older Golden Retriever. She had acutely collapsed and her veterinarian noted that her heart sounds were very quiet and suspected fluid had built up around her heart called pericardial effusion.
An echocardiogram unfortunately revealed a cardiac tumour. This tumour was growing from the right atrium and had bled, causing build up of blood around her heart. In this image, you can see the darker space around the heart – this is the effusion. The bright white line around the effusion is the pericardium (heart sac). The right atrium, tricuspid valve and right ventricle are centered in this image. The tumour is located along the right atrium (the darker structure to the left of the right atrium).
Doppler Blood Pressure
Measuring blood pressure is an important part of a cardiac examination in any animal – that’s why we include it with all of our cardiac evaluations! Systemic hypertension is common in animals with many affected animals showing no signs of disease.
Hypertension can have a negative impact on the heart function in animals with heart disease. Therefore addressing hypertension is an important part of a treatment plan in any animal with heart disease.
Some of the medications prescribed to a patient with heart disease can lower the blood pressure – therefore, trending blood pressure becomes an essential part of monitoring therapy in these animals.
Many veterinarians use Doppler blood pressure to measure the pressure indirectly. A small ultrasonic crystal is used to hear the arterial pulse while a small cuff is inflated and deflated to allow measurement of the systolic blood pressure. In animals, the systolic blood pressure is very similar to that in a human.
Electrocardiogram (ECG)
An electrocardiogram (ECG) is our best test to diagnose an irregular heart rhythm (arrhythmia) in an animal. Animals with heart disease can commonly have secondary arrhythmias such as Atrial Fibrillation. We use the ECG to tell us about the rhythm and electrical activation of the heart. We also use the ECG to assess response to medical treatments – some animals can have a serious life threatening arrhythmia called ventricular tachycardia that will be treated with an intravenous medication called lidocaine. We use the ECG to assess response to lidocaine and ensure conversion back into a normal sinus rhythm.
Holter/Event Monitor
A Holter monitor is a small, lightweight ambulatory electrocardiogram (ECG) that animals can wear to assess for intermittent arrhythmias and also evaluate for potential causes of syncope (fainting). It is also used to assess response to anti-arrhythmic therapy for a variety of arrhythmias.
Some Holters can stay on for a longer period of time (days) – these are best for intermittent episodes that may not occur daily. This is called an event monitor and requires the pet owner to trigger the device following an episode.
