Heart disease is a syndrome caused by a variety of structural and functional disorders of heart and the vessels. It can be caused by a variety of underlying diseases such as dilated cardiomyopathy (DCM), mitral valvular disease, cardiac dysrhythmias, chronic obstructive pulmonary disease with pulmonary hypertension, pericardial effusion (build-up of fluid in space around heart), endocardiosis, systemic hypertension, hypothyroidism, aortic valve insufficiency, blockage in one of the pulmonary arteries in lungs, arrhythmias (abnormal rhythms), heart muscle disease etc
Clinical manifestations of heart failure are due to lowered cardiac output (weakness, exercise intolerance, fatigue), pulmonary congestion (shortness of breath, cough, abnormal breath sounds, crackles and wheezes), systemic fluid retention (jugular venous distention, enlarged liver, fluid build-up in belly or lungs i.e. pleural effusion) or a combination of these conditions.
Common signs of heart diseases in dogs:
Heart disease is structural or functional deformity of the heart. Anatomic or physiological disorders of heart can be congenital or acquired. The causes range from infectious, degenerative, genetic or anatomic abnormalities. Following are the common signs of cardiac dysfunction in dogs:
- Difficulty breathing – Dogs with heart disease breathe rapidly or with force. They can often be seen with necks stretched out, or making wheezing sounds. Trouble breathing is more common in dogs with cardiac dysfunction particularly when they are lying down.
- Coughing – This happens when there is fluid build-up in lungs, which usually gets frequent as the heart disease gets chronic.
- Loss of appetite – Decreased appetite or fussiness towards food or treats is also common
- Lethargy, weakness – Dogs with heart disease will exhibit signs of exercise intolerance. Many dogs will tire out easily and may have pale or bluish gums.
- Possible murmur or gallop – Physical examination can reveal heart murmurs, weak femoral pulses, pulmonary crackles or wheezes.
- Weight loss or muscle wasting – Cachexia and muscle atrophy are common with heart disease in dogs
- Systemic fluid retention – pleural effusion, hepatomegaly, fluid in belly are common conditions in conjunction with heart disease
Obesity – Obesity leads to increased heart rate, exercise intolerance, variable blood pressure, elevated cardiac output and many other such cardiovascular consequences. Body weight & blood pressure are directly correlated, and blood pressure always increases with increasing weight in dogs. High insulin and sodium retention is also common with obesity. This worsens the heart disease symptoms.
- Weight Loss or Muscle wasting – Lean muscle mass wasting and loss of weight are seen in chronic heart failure. This is due to a difference between food consumption and nutritional requirement leading to protein loss. Chronic inflammation and use of drugs can also lead to anorexic state. Elevated heart rate and respiratory distress leads to increased calorie requirement in dogs with heart disease.
- Hypertension – Renal disease causes secondary hypertension as control of blood pressure is done by kidneys. When there is no underlying disease, it is called primary hypertension. Higher fat or carbs diet can lead to obesity, which can then cause hypertension. Screening for pulmonary arterial hypertension should be regularly done for left-sided congestive heart failure.
- Kidney disease – Low cardiac output can lead to decreased renal performance. Abnormal heart rhythm and damage to the heart are common in dogs with acute kidney injury. Both kidney and heart influences endocrine responses that affect fluid balance. Kidney-mediated systemic hypertension leads to left ventricular hypertrophy, worsening mitral or aortic valve insufficiency, and cardiac arrythmias.
- Fluid build-up – Dogs with right heart failure (due to severe heartworm disease, severe valve dysplasia, cardiac tamponade etc) can develop fluid in abdomen. Pleural effusion occurs as a result of an impairment in circulation in dogs with biventricular heart failure.
Classes of Heart Disease:
Heart disease can be present without ever leading to heart failure. Chronic mitral valvular disease (endocardiosis) is the most common acquired cardiac abnormality in dogs. Structural abnormalities of the heart can be divided into three classes:
Class I Asymptomatic – This is when clinical signs of heart failure are not overtly evident. Cardiac murmur or arrythmia are detectable at this stage.
Class II Mild to Moderate Heart Disease – Clinical signs such as coughing, exercise intolerance, respiratory distress are evident
Class III Advanced Heart Failure – Clinical signs are immediately evident. Respiratory distress, reduced blood flow, fluid build-up is detectable.
Diagnosis of Heart disease in dogs:
A complete physical examination should be performed on a dog being evaluated for heart disease. In many instances, heart failure becomes evident gradually after a long asymptomatic period following the diagnosis of a valvular heart disorder based on the presence of murmur or arrythmias. This may be followed by the onset of mild to moderate clinical signs that worsen slowly, and lead to pulmonary edema. Heart murmurs i.e. audible vibrations coming from the heart or major blood vessels can be examined during Vet visit. The following tests are helpful in diagnosis:
- Chest X-ray – X-ray helps in assessing the size of your dog’s heart and check for any fluid build-up in lungs
- ECG (Electrocardiogram) – This helps in detecting arrythmia (rhythm of heartbeat). Arrhythmias are abnormalities of the rate, regularity, or site of cardiac impulse formation and are noted during auscultation. During an arrhythmia, the heart can beat too fast, too slowly, or with an irregular rhythm. However, the presence of cardiac arrhythmias does not necessarily indicate the presence of heart disease.
- Echocardiogram – This is ultrasound of heart which provides pictures of the heart's valves and chambers. This helps in definitive diagnosis of the presence of heart diseases in dogs.