An older, coughing dog is brought into examination room. Owners claim, they noticed exercise intolerance, that was going on for a while, but attributed it to dog’s age. Our mind can quickly jump to the idea of heart disease and necessity for thoracic x-rays and echocardiography …
We will probably really need them. But before jumping to more advanced diagnostic techniques, don’t forget that cough is not specific sign for heart failure and is often present in dogs with respiratory disease. And I use cough as an example – also exercise intolerance and dispnea can be caused by various other conditions. A proper clinical examination with evaluation of cardiovascular system can help us decide, whether it goes about cardiac disease at all, and maybe even points us toward specific disorder.
As every other, cardiovascular exam starts with signalment and detailed history. Keep in mind, that some abnormalities are more prevalent in certain breeds or life stages.
- Subaortic stenosis: Boxer, German Shepherd, Golden Retriever, Great Dane, Rottweiler
- Pulmonic stenosis: Boxer, English Bulldog, terriers, Cocker Spaniel, Miniature Schnauzer
- PDA: mostly small breed dogs – poodle, Yorkshire terrier, Shetland sheep dog, Pomeranian, collies and also German Shepherd
- Dilated cardiomyopathy: large to giant breed dogs – Boxer, Doberman Pinschers, Golden Retriever, Great Dane, Newfoundland, spaniel breeds
- Hypertrophic cardiomyopathy: cats
- Myxomatous mitral valve degeneration: most common cardiac disease in older dogs; predisposed in small to medium-sized breeds – Cavalier King Charles Spaniel, Papillon, Poodle, Chihuahua, Dachshund
Physical evaluation starts with observation of respiratory pattern, before the patient is stressed by examination. Animals in cardiac failure are usually dyspneic and appear anxious. We can notice increased respiratory rate and effort, flared nostrils, open-mouth breathing, reluctance to lie down and sitting or standing with abducted elbows. Pulmonary edema increases stiffness of the lungs, which results in rapid and shallow breathing (restrictive respiratory pattern), as animal tries to minimize the work of breathing.
Hands-on cardiovascular examination consists of evaluating peripheral circulation (mucous membranes), jugular veins, systemic arterial pulses, palpating for abnormal fluid accumulation and liver enlargement and chest auscultation.
Usually oral mucous membranes are inspected for colour and capillary refill time (CRT) to evaluate peripheral perfusion. Normal CRT is about 2 seconds, but slower refill times occur in causes of decreased cardiac output. Mucous membranes appear pale with poor cardiac output and cyanotic in causes of inadequate oxygenation, which can be seen with pulmonary edema. Comparing the colour of oral mucosa with caudal membranes (prepuce or vagina) can be useful in case of reversed patent ductus arteriosus (causes differential cyanosis, in which cranial portions of the body are adequately oxygenated, but caudal parts receive desaturated blood and appear cyanotic).
Jugular veins allow evaluation of systemic venous pressure. They are not distended in healthy animals when standing with head in normal position. Persistent jugular distention is a sign of venous stasis as a result of right-sided heart failure (elevated right atrial pressure), external compression of cranial vena cava or thrombosis of jugular vein or cranial vena cava. In some cases, a pulsation of jugular veins can be seen: tricuspid insufficiency, hypertrophied right ventricle and some arrhythmias. If elevation of right atrial pressure is to mild to cause persistent jugular distension, we can test hepatojugular reflux by pressing on cranial abdomen. This increases venous return to the right heart and causes temporary jugular distension, which resolves as abdominal pressure is released. In long-haired animals the coat on neck can be wetted with spirit, to avoid clipping in order to assess jugular veins.
Evaluation of peripheral pulse strength and rate is usually assessed on femoral arteries. Pulse strength depends on difference between systolic and diastolic arterial pressure – with wider difference, the pulse fells stronger. Decreased pulse strength may be caused by left ventricular outflow obstruction (subaortic stenosis) or very low cardiac output (dilated cardiomyopathy). An exaggeratedly increased strength of pulse on expiration and weak pulse during inspiration occurs with cardiac tamponade. Increased pulse can occur because of excitement, pain or hypertrophic cardiomyopathy. Bounding femoral pulse is present with increased pulse pressure (PDA, aortic insufficiency, hyperthyroidism). Both femoral pulses should be palpated at the same time and compared – absence or weaker pulse on one side may be a result of thromboembolism. Femoral pulse should also be compared to heart rate (by chest auscultation), to detect any possible pulse deficits, which can be caused by cardiac arrhythmias.
Right-sided heart failure can result in accumulation of excessive fluid within body cavities and enlargement of liver and spleen. To detect effusions, palpation and ballottement of the abdomen and percussion of the chest should be performed. Liver enlargement may also be detected with abdominal palpation.
Cardiac auscultation is performed to evaluate hearth rate, rhythm, normal and abnormal sounds. Auscultation should be performed in a quiet room, ideally with animal in standing position (normal position of the heart). Both chest sides should be auscultated especially over the valve areas, and for any possible abnormal sounds the point of maximum intensity should be located. If the animal is panting, that can be stopped by holding the mouth closed and purring of cats may be stopped by holding a finger over one or both nostrils, holding alcohol-soaked cotton ball near cat’s nose or open the water flow near the animal. Normal heart sounds can be muffled in case of obesity, pericardial effusion, pleural effusion, diaphragmatic hernia, dilated cardiomyopathy or other intrathoracic pathologies. Abnormal heart sounds – murmurs can be classified as systolic, diastolic or continuous, based on their timing within cardiac cycle. By their intensity, they are divided into 6 different grades:
|I||very soft, heard only after longer listening in quiet surrounding|
|II||softer than normal heart sounds, but easily heard|
|III||as loud as normal heart sounds|
|IV||louder than normal heart sounds, without precordial thrill|
|V||louder than normal heart sounds, with palpable precordial thrill|
|VI||very loud, with a precordial thrill, heard with the stethoscope lifted from the chest wall|
Check the next post for more about normal and abnormal heart sounds.
Nelson R. W., Couto C. G.: Small Animal Internal Medicine, 4th Ed. Mosby Elsevier, 2009
Fuentes V. L., Johnson L. R., Dennis S.: BSAVA Manual of Canine and Feline Cardiorespiratory Medicine, 2nd Ed. BSAVA, 2010