THERE are a plethora of diagnostic tests available for the suspected cardiology patient – at considerable cost to the owner.
However, in deciding which may be appropriate tests, or in conserving funds for potentially expensive therapy, a wealth of information can be gleaned from careful history taking and the physical examination.
History
Signalment is important! If your patient is a middle-aged or older Cavalier King Charles spaniel with a loud systolic heart murmur, tachypnoea and cough, it is highly likely to have myxomatous degenerative valvular disease (MVD); echocardiography may not be essential.
If a St Bernard presents with a chaotically irregular arrhythmia and soft heart murmur with weak pulses, it is most likely to have dilated cardiomyopathy (DCM) with atrial fibrillation.
Thorough history taking can identify signs of cardiac disease. If the patient has previously had episodes of collapse or weakness, careful questioning should allow you to differentiate between a neurological or cardiac cause. If unsure in this regard, a video of the event captured by the owner is useful.
Any history of coughing should direct questioning to characterise its nature. Cardiac coughs are typically soft, mild, intermittent and nocturnal. Coughs producing pink-tinged fluid are indicative of fulminant pulmonary oedema. Conversely, cats rarely cough due to cardiac disease.
The physical examination should identify significant problems that need to be addressed with the selected treatment. Questions to be answered from the physical examination in the suspected cardiac patient should be:
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Are there abnormalities on thoracic palpation?
Palpation of the thorax can give you a wealth of important information before even auscultating. Assess for deviation and strength of the cardiac apex beat (normally located over the left fourth to sixth intercostal space at the costochondral junction). Deviation to the right side may be caused by a mass effect or right-sided enlargement. Moreover, a hypokinetic beat indicates reduced contractility, pericardial or pleural effusion or may be the result of obesity.
A cardiac thrill specifies a heart murmur grade of V-VI/VI. Thoracic compressibility can be reduced in cats with a cranial mediastinal mass or pleural effusion. Percuss the thorax; ventral dullness is consistent with pleural effusion.
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Are there any abnormal auscultation findings?
Remember that not all cats or dogs with congestive heart failure (CHF) will have obvious auscultation abnormalities. Particularly be wary of the coughing Dobermann; it may have DCM, with sinus rhythm and no audible murmur.
It is worth listening specifically for diastolic gallops (S3/S4) sounds, with the bell of your stethoscope applied with minimal pressure over the left apex. These are usually apparent in cats with myocardial disease or dogs with DCM, although the loud heart murmur masks them in dogs with mitral valve disease. Assess the volume of the heart sounds in relation to the thoracic conformation and body condition score of the patient; a lean Great Dane with quieter than expected heart sounds may have DCM.
Although muffled heart sounds are expected in cases of pericardial effusion, sounds are not always muffled as effusions may be haemorrhagic, and blood is actually a good acoustic conductor. Conversely, dogs with MVD often have loud heart sounds, especially S1. Carefully auscultate the entire lung field for evidence of crackles. These can often be tricky to hear; an optimal environment and length of listening will reward with more information. Breath sounds may be absent ventrally with a significant pleural effusion.
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Is there forwards heart failure (or poor cardiac output)?
Signs from the clinical examination include weak femoral pulses, cold extremities, pale mucus membranes with sluggish capillary refill and possibly hypothermia.
The blood pressure may be low or low-normal. If these signs are present, especially with hypotension, positive inotropic support is required (e.g. pimobendan).
In the presence of CHF, with the neuroendocrine activation including many vasoconstrictors such as noradrenaline, angiotensin II, vasopressin and endothelin, failure to maintain blood pressure is regarded as a grave prognostic indicator.
Tip: note that arrhythmias, particularly tachyarrhythmias such as ventricular tachycardia or fast atrial fibrillation may be associated with these signs, and pulse deficits. If these signs are noted, this is a haemodynamically significant arrhythmia, which requires treatment. An ECG is essential to select appropriate anti-arrhythmic drugs.
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Is there backwards left-sided congestive heart failure (pulmonary oedema)?
Patients will be tachypnoeic with a restrictive breathing pattern (shallow). Auscultation may or may not identify inspiratory crackles.
Cough in dogs is usually due to the associated left atrial enlargement and compression of the left caudal mainstem bronchus.
Thoracic radiographs are the best method to confirm cardiogenic pulmonary oedema and to exclude other respiratory pathology. However, if suspected, trial treatment with furosemide should result in dramatic improvement.
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Is there backwards right-sided congestive heart failure?
In dogs, this is usually manifested as ascites (Figure 1). Owners will note progressive abdominal distension and a fluid thrill will be evident on ballotment. There is often palpable hepatomegaly.
If the abdominal effusion is due to right-sided CHF, the jugular veins will be distended (Figure 2), and pulsations will be evident more cranially than usual. Try to elicit the hepatojugular reflux (HJR): with gentle cranial abdominal pressure the jugular veins will become more prominent.
Pleural effusion can also be a consequence of right-sided or biventricular CHF in cats. If you suspect a pleural effusion, then thoracocentesis is both diagnostic and therapeutic.
Tip: in a dog with only rightsided CHF signs (no left), it is vital to exclude a pericardial effusion as a cause. The pulse quality may vary during respiration (pulsus paradoxus), pathognomic for a pericardial effusion.
Conclusions
Thorough history taking and examination of possible cardiac cases can yield much information at little expense. This can help direct further investigations or treatment with greater efficiency. The whole story is important; looking at the big picture will help you do the best for your patient.
