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Diagnosis of Cardiovascular Disease in Cats

By

Suzanne M. Cunningham

, DVM, DACVIM (Cardiology), Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University;


Kursten V. Roderick

, DVM, Tufts University

Last full review/revision Jul 2018 | Content last modified Aug 2018
Topic Resources

A veterinarian often diagnoses cardiovascular disease by reviewing the medical history and signs, conducting a physical examination, and interpreting the results of specific tests or imaging procedures. The physical examination includes using a stethoscope to listen to the heart and lungs. A veterinarian may hear an abnormal heart rate (for example, a rate that is too slow, fast, or irregular), an abnormal breathing rate (fast or labored breathing), additional heart sounds (called a "gallop" rhythm), a murmur (an abnormal sound caused by abnormal blood flow or vibrations in the heart), decreased or muffled heart sounds, or abnormal sounds in the lungs that suggest the fluid accumulation. Veterinarians also feel a cat's pulse, which may feel rapid, weak, or irregular. In addition, veterinarians feel the body with their hands and fingers to detect abnormal fluid accumulation in the abdomen. A cat's gums are also examined to look for evidence of blue, purple, or grey color, a sign that oxygen is not reaching the body's tissues adequately.

Common Types of Imaging Used to Diagnose Heart Disease

X-rays

X-rays (also called radiographs) of the chest frequently help diagnose heart disease in pets. Finding generalized enlargement of the heart or enlargement of specific heart chambers makes the presence of heart disease more likely. The images may also provide clues as to the specific disease present. For example, fluid in the lungs is a common finding in congestive heart failure. Although chest x-rays are useful in evaluating patients with heart disease, they have certain limitations. The presence of fluid in the lungs does not definitively confirm a disease originating from the heart or exclude another origin, such as pulmonary (lung) disease. Also, assessment of overall heart size and the size of specific heart chambers is typically far less accurate than testing by echocardiography (ultrasonography).

Electrocardiography

Electrocardiography is the recording of the heart’s electrical activity from the body surface with the use of electrodes. It can be used to identify heart arrhythmias, such as bradycardia (slower than expected rhythm), tachycardia (faster than expected rhythm), or other abnormalities of rhythm (such as sinus arrhythmia or sinus arrest).

Electrocardiography can also detect conduction disturbances, or failures of the electrical signals that cause the heart to contract to pass through the heart tissue. These include first-, second-, and third-degree atrioventricular block.

Finally, electrocardiography can identify chamber enlargement, which is indicated by waveform abnormalities shown on the electrocardiogram recording. Different readings suggest enlargement of the different chambers. While the electrocardiogram may suggest chamber enlargement, chest x-rays and echocardiography (ultrasonography) are more effective.

Echocardiography

Echocardiography is a type of ultrasonography used to evaluate the heart, the aorta, and the pulmonary artery. Echocardiography complements other diagnostic procedures by examining and displaying the working heart and moving images of its action. Heart chamber and wall dimensions can be determined; the physical structure and motion of valves can be seen; and pressure differences, blood flow volumes, and several measurements of heart function can be calculated. There are 3 main types of echocardiography: 2-dimensional, m-mode, and Doppler. Two-dimensional echocardiography provides a wedge-shaped, 2-dimensional video of the heart as it moves. M-mode echocardiography is produced by a 1-dimensional beam of ultrasound that penetrates the heart, providing an “ice-pick view.” Differences in tissue density that are detected by the beam are then plotted on a screen. This is typically used to measure chamber size, wall thickness, valve motion, and the size of the aorta and pulmonary artery. Doppler echocardiography detects changing frequencies of the ultrasonic beam as it contacts moving red blood cells to measure the speed of blood flow and thus identify turbulent or high-speed flow. This can locate heart murmurs.

Cardiac Catheterization

Cardiac catheterization involves the placement of specialized catheters (thin, flexible tubes) into the heart, aorta, or pulmonary artery. Cardiac catheterization may be performed when other diagnostic tests are insufficient to identify specific heart abnormalities or are unable to identify the severity of a lesion. It may also be used for presurgical evaluation, treatment, and in clinical research. Diagnostic and presurgical cardiac catheterization, however, have largely been replaced by echocardiography (see above). Most of the time now, cardiac catheterization is done to surgically repair defects in the heart.

Your cat's age and breed may help your veterinarian diagnose its heart disease. For example, a middle-aged cat with labored breathing and reluctance to lie down may have heart muscle disease (most commonly hypertrophic cardiomyopathy Hypertrophic Cardiomyopathy Cats can develop many different cardiovascular diseases. The ones discussed below are the most common. This acquired disease is characterized by a thickening of the heart valves. Degenerative... read more ), whereas an older cat with weight loss and behavioral changes is more likely to have hyperthyroidism Hyperthyroidism The thyroid gland is a 2-lobed gland in the neck. It produces 2 iodine-containing hormones, T3 and T4, which affect many processes in the body. In general, the thyroid hormones regulate metabolic... read more , which can cause high blood pressure and worsen heart disease. In addition, certain heart diseases are more common in some breeds.

Imaging techniques include x-rays, electrocardiography (recording electrical activity of the heart), and echocardiography (a type of ultrasonography). Many cardiovascular diseases can be diagnosed by physical examination and x-rays. X-rays are also used to diagnose and monitor congestive heart failure Heart Failure in Cats Heart failure is not a specific disease or diagnosis. It is a syndrome in which severe dysfunction results in failure of the cardiovascular system to maintain adequate blood circulation. There... read more . Electrocardiography is used to diagnose heart rhythm disturbances (arrhythmias). Echocardiography is excellent for confirming tentative diagnoses, assessing the severity of leaky heart valves or narrowed vessels, evaluating chamber sizes and heart muscle function, identifying types of cardiomyopathy, diagnosing high blood pressure in the lungs, identifying birth defects in the heart, detecting heart tumors, or identifying disease of the membrane that surrounds the heart (the pericardium). Your veterinarian may also recommend a specific blood test that measures proteins that increase in certain types of heart disease and failure. Occasionally, more specialized tests such as cardiac catheterization (using a thin flexible tube inserted and threaded through an artery into the heart) or nuclear studies (x-ray tests that include injection of radioactive isotopes) are necessary. In cats, diagnosis of heartworm Heartworm Disease in Cats Heartworm disease is a potentially fatal, but preventable, infection caused by a worm parasite, Dirofilaria immitis. The organism is transmitted by mosquitoes, which carry the heartworm larvae... read more disease may include blood tests, x-rays, and echocardiography.

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