Heart disease is an important and common condition in pets. As a pet owner, it is important for you to know the signs of heart disease and to have a basic understanding of how the heart works, why it fails and how treatment can help.

Heart diseases can be placed into two general categories, congenital or acquired. Congenital conditions are those with which your pet is born or to which he is genetically predisposed. Common congenital conditions include stenosis (narrowing) of the outflow arteries (aortic and pulmonic), septal defects (holes in the wall that separates the right and left sides of the heart, and valvular dysplasias (malformations). The effect of these abnormalities can vary from a barely detectable benign heart murmur to severe abnormalities in blood flow patterns which can result in death within the first few hours of life.

Acquired heart diseases are those which develop due to factors other than genetics or congenital anatomical defects. These diseases tend to affect mature to older pets and most often involve valvular disease, myocardial (heart muscle) disease or a combination of the two.

Anatomy of the Heart:

The heart consists of a series of chambers separated from each other by one-way valves and septae (walls). The right side of the heart receives oxygen- poor blood from the body and pumps it through the pulmonary artery to the lungs. The left heart receives this oxygenated blood from the lungs and pumps it to the body through the aorta. Normally the right side of the heart and the pulmonary vascular bed, have low pressures (5-20mmHg) relative to the left side of the heart and the systemic vascular bed (60-120mmhg).

Pathophysiology of Heart Disease:

The heart is essentially a pump whose job it is to move blood through the body in a specified manner. Cardiac output (CO) is defined as the volume of blood pumped at each beat (stroke volume) multiplied by the heart rate.

(CO =Heart Rate X Stroke Volume), Heart failure is nothing more a decrease in cardiac output. This can occur either due to defects in the valves and walls of the heart, or due to failure of the heart muscle itself. When the heart begins to fail, the body is equipped with a group of nervous and hormonal compensatory mechanisms that help correct for the decline in pump efficien text/javascript”> cy. These systems initially increase both stroke volume and heart rate thus increasing cardiac output. Stoke volume is increased by the retention of sodium and water under the control of the kidneys. As total blood volume increases, the heart must enlarge to accommodate it. Initially this results in increased stroke volume and increased cardiac output. However beyond a certain point, stretching of the heart muscle results in decreased contractility and a fall in stroke volume. Eventually, the excess fluid begins to leak into the tissues either as fluid on the lungs (left heart failure) or fluid in he abdominal cavity (right heart failure). It is at this point where symptoms of congestive heart failure begin do develop

Symptoms of Heart Disease:

In its early phase, heart disease is usually silent. The first signs are often the presence of a heart murmur or an arrhythmia that is detected during physical examination. Owners are much more likely to detect early heart disease in an athletic patient than in a sedentary one. These athletic pets will lose their ability to perform. Sedentary pets are often presented in advanced heart failure before the owner has noticed any significant behavioral changes.

The symptoms of heart disease include:

  • Lethargy
  • Unwillingness to perform normal activities
  • Elevated heart rates
  • Increased respiratory rates
  • Coughing
  • Abdominal distension

These symptoms are the direct result of poor tissue perfusion and the accumulation of excess fluid in the lungs and soft tissues of the body. Because cats are so sedentary by nature, heart disease is especially dangerous. Cats frequently present with acute severe heart failure and an owner who has noticed no abnormal behavior.


Heart disease is diagnosed and quantified based on physical exam findings, chest radiographs, echocardiography, electrocardiography and blood work. It is important to thoroughly evaluate a patient with an abnormal heart on physical exam to determine:

  • The source of the problem
  • The severity of the problem
  • The most appropriate course of therapy

The physical examination will give information regarding the type of problem (arrhythmia vs. murmur) and allow one to narrow the list of possible causes based on specific findings. Radiographs provide general information concerning overall heart size and most importantly whether there is actual congestive heart failure (presence of fluid in the lungs or abdomen).

Echocardiography is the gold standard for the diagnosis of heart problems. It allows us to examine the heart in real time motion and

  • Accurately measure heart size
  • Evaluate individual valves and heart cambers
  • Detect abnormal blood flow patterns across valves and quantify their severity
  • Detect pulmonary and systemic hypertension
  • Detect congenital defects
  • Monitor the effective of treatment

Treatment of Heart Failure:

The treatment of heart disease is determined by the severity of the condition. In animals with a heart murmur and no associated signs of heart enlargement or failure, no treatment may be indicated. The heart condition should be rechecked every 6 to 12 months to monitor the progression of the problem.

The owner plays an important role in monitoring the pet for progression of heart disease by being alert for symptoms of heart problems such as lethargy, exercise in tolerance and coughing. Should symptoms begin to appear, the pet should be rechecked regardless of whether a follow up visit is due.

For pets with radiographic signs of heart enlargement or congestive heart failure, a multi faceted approach to treatment is indicated. The use of low salt diets is very important in mitigating the kidney’s ability to retain fluid. Pharmacologics such as blood pressure medications, diuretics and positive inotropes (drugs that increase the strength of the heart beat) all play a role in the management of heart failure.


The prognosis for pets with heart failure depends on multiple factors including the underlying disease, the stage at which the problem is diagnosed and the pet’s response se to therapy. Early and accurate diagnosis with prompt and appropriate therapy represent the best chance for successfully managing heart disease in pets.