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Heart failure diagnosis and investigations

In the first of a two-part feature on heart failure, Professor Bun Tan answers questions from GP Dr Stefan Cembrowicz

In the first of a two-part feature on heart failure, Professor Bun Tan answers questions from GP Dr Stefan Cembrowicz

1 What reversible causes of heart failure should GPs think about?

The most common cause of heart failure in the UK is ischaemic heart disease. About a third of patients have silent ischaemia or hibernating myocardium, and their presenting complaint is not angina but breathlessness on exertion, just like patients with heart failure. It is important to identify patients with silent ischaemia because coronary revascularisation, via angioplasty or bypass surgery, may improve cardiac function to such an extent as to obviate the diagnosis of heart failure.

Other reversible lesions to look out for include any form of:

• valvular diseases • arrhythmia • conduction defects, including heart blocks or bundle branch blocks causing contractile dyssynchrony, pericardial effusion or constriction.

Some of these lesions can be corrected through cardiological interventions. It may not always be easy to make such diagnoses.

2 How is heart failure now categorised – systolic/diastolic failure, or low output versus high output? And how does this classification help with choosing treatment?

Heart failure has been categorised in several ways.

Acute/chronic This is the most important categorisation in practice, because, although they are both heart failure, the treatment is distinctly different. In acute decompensated heart failure, the patients are symptomatic at rest and exercise is out of the question; whereas those with chronic compensated heart failure are generally comfortable at rest but become symptomatic during exercise. Therapy for chronic heart failure (such as ACE inhibitors, ß-blockers, angiotensin receptor blockers) may need to be temporarily stopped during an acute exacerbation.

Compensated/decompensated As above.

Systolic/diastolic This is probably the most confusing and unhelpful categorisation because, in terms of cardiac muscle mechanics, systolic and diastolic dysfunction invariably coexist. It is more important to determine the severity and cause of heart failure in these patients in order to decide how best to treat, than to worry about whether it is systolic or diastolic.

Right-sided/left-sided heart failure Because both right and left sides of the heart share a common pericardium and atrial and ventricular septa, there are always significant interactions between the two sides.

Low-output/high-output High-output heart failure is so rare nowadays that it is doubtful many GPs will ever see it.

Absolute/relative The aim of treatment should not be stimulating the heart, but to lower its load. Absolute heart failure is when the heart itself is intrinsically failing and unable to maintain a normal human circulation.

3 A young female patient of mine has developed heart failure after successful radiotherapy for breast cancer. Is this a recognised cause of heart failure?

Yes, radiation injury to the heart is a known complication of radiotherapy and can result in heart failure. Oncology societies have issued guidelines on how to avoid or minimise radiotherapy-related (or chemotherapy-related) cardiotoxicity that manifest as cardiac myocyte loss and/or increased fibrosis. Management of radiotherapy-related heart failure follows the same lines as other forms of heart failure.

4 An echocardiogram is now considered sine qua non for the diagnosis and assessment of heart failure; but what other clinical signs should be remembered?

The most important point to remember about echocardiogram is that it is an imaging technique, and particularly good at determining structural defects in the heart, so it may help to identify the cause of the failure. However, organ failure or not pertains to cardiac function and dysfunction, which may or may not be related to identified structural abnormalities.

Presence of an abnormality in structure does not necessarily mean presence of abnormality in function, whereas abnormality in function may be improved by correcting the abnormal structure.The most widely used echocardiographic parameter quoted for heart failure assessment is left ventricular ejection fraction (LVEF). This has often been touted as an indicator of cardiac function, but in actual fact, it is more an indicator of structure, the size of the chamber of the left ventricle. It is important to note that a normal LVEF does not rule out the presence of heart failure in a patient with typical features of heart failure. The patient may have true 'diastolic' heart failure, or the heart failure could have been caused by silent ischaemia, arrhythmia, valvular diseases, or relative heart failure caused by inappropriate ventricular loading.In terms of clinical signs (and symptoms), it is worth remembering that the two entities the heart's function must supply adequately are blood pressure and cardiac output. Therefore, the important features to look out for include the following.

• Blood pressure The question to bear in mind is 'Can the failing heart generate sufficient blood pressure to perfuse the body tissues? In critical cases, do not rely on automatic blood pressure equipment because they can be quite misleading. I have come across patients in cardiogenic shock (systolic blood pressure <80 mmHg and oliguric) when the (correctly calibrated) automatic blood pressure machines actually registered normal blood pressure.

• Cardiac output Look out for signs of low cardiac output, such as thready pulse, cold ± cyanosed peripheries, cutaneous shut-down giving appearance of paleness, unexplained sweatiness, listlessness and oliguria/anuria.

Natural physiological mechanisms are usually activated to compensate for the poor cardiac function, and one prominent one is raising filling pressures, manifested as raised jugular venous pressure (JVP), pitting oedema, hepatic congestion, inspiratory crackles, white frothy sputum. The feature to be concerned about is when the pulmonary oedema is so severe as to cause respiratory failure.

5 What other tests are useful when assessing a heart failure patient – for example, bloods, ECG, chest X-ray and particularly brain natriuretic peptide (BNP)? And should we check uric acid?

In patients with severe heart failure, any systemic setback or other organ impairment may tip them over into worsening heart failure.

• By far the most common is any type of chest infection. A chest X-ray may help.

• Another common cause of worsening heart failure symptoms is the onset of atrial fibrillation, so do an ECG.

• Anaemia is common in heart failure and needs aggressive monitoring and treatment. Similarly, poorly controlled diabetes or thyroid disorders affect heart failure.

• Uric acid is always raised when patients are treated with diuretics, but treat and monitor it if symptoms of gout are present.

• Because fluid balance is a major issue in heart failure management, and diuretics still the first-line therapy, the wellbeing of heart failure patients is closely related to renal function. Close monitoring of U&Es is essential at all stages of heart failure management to avoid arrhythmias, which worsen the failure.

• It is also vital to protect renal function, because in a heart failure patient without adequate renal function, medical therapy is virtually impossible, because dialysis is not a realistic option.

The above investigations all relate to indirect effects on heart failure. What clinicians really need is a direct measure of organ function or dysfunction; LVEF is unfortunately not a measure of organ function. In the past two decades, it has emerged that the most representative measure of organ function is peak cardiac power output (CPOmax), not dissimilar to peak brake horsepower used by engineers to grade car engines. Unfortunately, only very few centres in the world have expertise to measure this. Surrogate measures of CPOmax include peak exercise oxygen consumption, exercise duration or other indicators of exercise capacity and BNP.BNP or its more stable form, N-terminal pro-BNP, is a blood test that:

• correlates significantly with the extent of cardiac dysfunction

• has a powerful negative predictive value for the presence of heart failure (low values effectively exclude the presence of significant heart failure)

• is a powerful prognostic indicator for heart failure.

This valuable relatively inexpensive blood test (much cheaper than echocardiography) has yet to become available as a routine test

Professor Bun Tan is a consultant cardiologist at Leeds General Infirmary

Competing interests None declared

Take-home points

• A third of patients with IHD have hibernating myocardium or silent ischaemia, and present with breathlessness on exertion rather than angina

• Left ventricular ejection fraction (LVEF) is not a direct indicator of cardiac function, but of the size of the left ventricle chamber; a normal LVEF does not rule out heart failure

• Systolic/diastolic may be the least helpful categorisation as the two invariably coexist – it is more important to determine severity and cause of heart failure

• Management of radiotherapy-related heart failure is similar to that for other forms of heart failure• Brain natriuretic peptide is a blood test that correlates with the extent of cardiac dysfunction, and has a powerful negative predictive value for the presence of heart failure

what I will do now

Dr Cembrowicz responds to the answers to his questions

I will remember to:

• hunt for these reversible causes for heart failure – for example, pericardial effusion can catch you out; and, as there are many treatments possible nowadays, look out for silent ischaemia

• recall the old familiar acute/chronic categorisation

• consider stopping the ß-blocker or ACE inhibitor when a heart failure patient becomes acutely unwell

• look out for classic clinical signs, which are still of huge diagnostic importance

• be aware of post-radiotherapy heart failure in breast cancer patients

• watch out for CPOmax, although BNP is arriving locally in our area and sounds really useful

Stefan Cembrowicz is a GP in Bristol

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