CANINE CARDIO CARE

By Veterinary Diagnostics Institute

Veterinary Diagnostics Institute (VDxI) http://www.vetdiag.com is a veterinary reference laboratory that offers the 1st and only canine and feline specific NT-proBNP blood tests called CardioCare.

The intended use of the CardioCare test is as follows:

Detect the following forms of heart disease in cats and dogs:

Dilated cardiomyopathy
Mitral Valve Disease
Hypertrophic Cardiomyopathy
Restrictive Cardiomyopathy
Detect Heart Failure in Cats and Dogs

This test is intended to identify cats and dogs at an earlier stage in the disease process that need to be triaged to a cardiologist for a cardiac work-up to include echocardiogram.

In general, at your regular vet visit the most common tool used to diagnose heart disease is auscultation. Auscultation involves listening to the heart with a stethoscope in order to detect abnormal heart sounds such as murmurs. In order for auscultation to be useful, the animal must be completely quiet and still. This is identical on the human side where physicians require patients to remain quiet in order for heart sounds to be accurately interpreted with a stethoscope. Veterinarians are presented with a unique and complicating problem when it comes to auscultation. Movement, cat purring, dog panting, excitement and anxiousness at the clinic, among other distractions, all complicate the veterinarian’s ability to make an accurate assessment with auscultation. Another problem with auscultation is discerning between innocent murmurs and those murmurs associated with heart disease. Finally, and most importantly, dogs and cats with heart disease may have no detectable murmur (occult disease).

In addition to the difficulty that may be encountered in detecting abnormal heart sounds, the clinical signs of underlying heart disease may be nondescript. Often times in the very early stages of heart disease signs may be absent.

When heart disease is detected late, prognosis is usually poor. Early diagnosis is important in order for the veterinarian to intervene and initiate a treatment regimen that will assist in delaying the progression of heart disease to heart failure.

This test is intended to only be used in conjunction with a veterinary exam, to include auscultation. Echocardiogram, performed by a cardiologist is the recognized gold standard to diagnose heart disease and heart failure. The following decision algorithm is provided as a tool to assist in determining which animals may benefit from CardioCare testing and to aid in the interpretation of a CardioCare result.

HOW CAN YOU GET YOUR ANIMAL TESTED? Ask your vet to visit Veterinary Diagnostics Institute's home page and set up an account with them. http://www.vetdiag.com or call them at 949-273-TEST

The AVMA goes on to state that “although some of the early stages of heart failure in dogs have no visible signs, heart failure can be diagnosed through a clinical evaluation by a veterinarian. Dogs with mild to moderate heart failure may present with cough, lethargy and difficulty breathing. Severe heart failure is characterized by difficulty breathing (even at rest), fainting, profound intolerance to exercise, loss of appetite and weight loss.

Heart Disease in Cats and Dogs – The Silent Killer

According to the American Veterinary Medical Association (AVMA) of all the dogs examined annually by veterinarians, approximately 3.2 million have some form of acquired heart disease and may be in heart failure.1 In a recently published study in the American Journal of Veterinary Research, published January 2007, the incidence of heart disease in dogs was found to be 17%. This published clinical study can be found at the following link: click here

In order to understand heart disease, we must first review the anatomy and function of the heart itself. The heart is responsible for moving deoxygenated blood through the lungs for oxygenation then pumping the newly oxygenated blood throughout the body to provide life-sustaining oxygen and nutrients to the peripheral organs. The physiology and life-sustaining function of the heart is identical for all mammals from humans to dogs and cats. Along with sharing cardiac physiology and function, unfortunately cats and dogs also share a similar risk for developing heart disease.

According to Dr. Joanne Bicknese, “Too often, dog owners do not take their dogs to visit the veterinarian until they are displaying severe signs of heart failure, and by then it may be too late.”

 

Heart disease includes a number of diseases affecting the function and/or structure of the heart. There are 2 types of heart disease, congenital and acquired. Congenital heart disease is present at birth, whereas acquired heart disease develops over a period of time after birth. Acquired heart disease comprises 95% of all cases of heart disease in dogs and cats. There are 3 types of acquired heart disease: valvular disease, myocardial disease, and pericardial disease. The most common type of valvular disease is Mitral Valve Disease (MVD). In MVD the mitral valve degenerates and leaks, allowing blood to flow, or “leak” back into the left atrium from the left ventricle. Myocardial disease is marked by disease of the heart muscle (myocardium). Although heart disease is marked by diseases affecting the function and/or structure of the heart, the heart is still able to effectively pump the required amount of blood throughout the body to the end organs. Heart failure is marked by the heart losing it’s ability to act as a pump. In other words, in heart failure the heart can no longer effectively pump the required amount of blood to the vital organs such as the brain and kidneys. In the absence of diagnosis, medical intervention and management, heart disease usually progresses to heart failure. Fortunately, when heart disease or heart failure is properly diagnosed, especially in the early stages, treatment exists to delay the onset of heart disease to heart failure, or when in heart failure, treatment exists to assist the heart in maintaining it’s ability to act as an efficient pump.

The risk of heart disease increases with age.

More and more pets are experiencing cardiac disorders. Also, certain breeds of dogs and cats are at an increased risk of acquiring heart disease. In cats the most common form of heart disease is hypertrophic cardiomyopathy (HCM), followed by restrictive cardiomyopathy (RCM). The Main Coon, American Shorthair, and Persian are feline breeds especially at an increased risk for heart disease. Dogs on the other hand, most commonly experience mitral valve disease (MVD) and dilated cardiomyopathy (DCM) with large breed dogs most at risk for DCM and small breed dogs at higher risk for MVD.

Auscultation: listening to the heart with a stethoscope

The most common tool used to diagnose heart disease is auscultation. Auscultation involves listening to the heart with a stethoscope in order to detect abnormal heart sounds such as murmurs. In order for auscultation to be useful, the animal must be completely quiet and still. This is identical on the human side where physicians require patients to remain quiet in order for heart sounds to be accurately interpreted with a stethoscope. Veterinarians are presented with a unique and complicating problem when it comes to auscultation. Movement, cat purring, dog panting, excitement and anxiousness at the clinic, among other distractions, all complicate the veterinarian’s ability to make an accurate assessment with auscultation. Another problem with auscultation is discerning between innocent murmurs and those murmurs associated with heart disease. Finally, and most importantly, dogs and cats with heart disease may have no detectable murmur (occult disease).

In a recently published study - click here, 17% of dogs at high risk for DCM where found to have occult disease. In other words, these dogs had underlying heart disease in the absence of outward signs or murmur.

In addition to the difficulty that may be encountered in detecting abnormal heart sounds, the clinical signs of underlying heart disease may be nondescript. Often times in the very early stages of heart disease signs may be absent. According to Dr. Joanne Bicknese, “Too often, dog owners do not take their dogs to visit the veterinarian until they are displaying severe signs of heart failure, and by then it may be too late.”1 The AVMA goes on to state that “although some of the early stages of heart failure in dogs have no visible signs, heart failure can be diagnosed through a clinical evaluation by a veterinarian. Dogs with mild to moderate heart failure may present with cough, lethargy and difficulty breathing. Severe heart failure is characterized by difficulty breathing (even at rest), fainting, profound intolerance to exercise, loss of appetite and weight loss.”1 Cats present an even greater diagnostic challenge in that they are good at masking, or hiding an underlying ailment, especially heart disease. Many times decreased activity is the only outward sign that cats will present when affected with heart disease. Other common signs of feline heart disease include shortness of breath, rapid breathing, fatigue, loss of appetite, reduced activity, and rear leg paralysis. Up to 25% of all cats with heart disease have no detectable murmur.

When heart disease is detected late, prognosis is usually poor. Early diagnosis is important in order for the veterinarian to intervene and initiate a treatment regimen that will assist in delaying the progression of heart disease to heart failure.

 

In heart disease, the heart undergoes increasing difficulty in pumping blood throughout the body. In the normal physiologic state, a minimum level of pressure within the blood vessels is required in order to perfuse the vital organs with life-sustaining oxygen and nutrients carried by the blood. In other words, just as a certain amount of minimum pressure is needed to push on a door to open it, a certain amount of minimum pressure within the blood vessels is required to move the blood, along with the vital oxygen and nutrients, from the vessels to the vital organs, such as the brain, kidney, liver, and even the heart itself.

When the pump (heart) begins to fail and can no longer maintain the proper volume of blood moving throughout the body, both the blood volume and the pressure within the vessels drop. This drop in pressure and volume found in heart failure initiate a cascade of compensatory mechanisms intended to maintain the adequate pressure within the vessels to sustain vital organ perfusion. The physiologic compensatory mechanisms include activation of the Renin-Angiotensin-Aldosterone System (RAAS). Activation of this compensatory mechanism increases pressure and volume within the vessels, but ultimately, when heart failure is not recognized and treated, leads to progression of left ventricular dysfunction by increasing overall cardiac workload – forcing the heart to work beyond it’s capacity.

Left unchecked, RAAS activation is harmful to the animal. This is where the Natriuretic Peptides play a role. The Natriuretic Peptides are natural antagonists to the renin-angiotensin-aldosterone system (RAAS). Natriuretic peptides are counter-regulatory molecules to counteract the harmful physiologic effects resulting from heart failure and RAAS activation. Natriuretic Peptides are characterized by their vasodilatory (widening of the blood vessels) and natriuretic (excretion of sodium) properties, which counteract the vasoconstriction and salt and water retention caused by the action of other molecules during heart failure.

So in summary, heart failure leads to decreased pressure and volume within the vessels. This causes inadequate perfusion of the vital organs. RAAS responds by constricting the vessels and restricting fluid from being excreted by the kidneys thereby increasing the pressure in the vessels. However, the effects of RAAS unfortunately force the heart, already in failure, to work even harder. Natriuretic peptides in turn counteract the effects of RAAS. Left unchecked and undiagnosed, heart failure ultimately leads to death as the heart ultimately fails in face of the demands placed on it by the competing mechanisms of RAAS and the Natriuretic Peptides.

In humans NT-proBNP and BNP are widely recognized markers for the diagnosis, prognosis and therapy monitoring of patients in heart failure. Also, the human clinical literature is clear in recognizing that BNP measurement is superior over electrocardiogram (EKG) and radiographs in diagnosing heart disease.

There are published clinical studies on the veterinary side that document the clinical utility of BNP in dogs and cats and benefit of measuring NT-proBNP in cats and dogs.

 

Click here to read published studies on this subject

References

1. AVMA website, Canine Illnesses and Diseases. Heart Disease in Dogs. Available at: http://www.avma.org/careforanimals/animatedjourneys/pethealth/canine.asp Accessed January 22, 2007.

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Veterinary Diagnostics Institute (VDxI) is a veterinary reference laboratory that offers the 1st and only canine and feline specific NT-proBNP blood tests called CardioCare. www.vetdiag.com