Allan D Struthers

Heart failure is a difficult disease to define. It is easy to recognise heart failure in its moderate/severe version where the patient has pronounced symptoms and signs accompanied by echocardiography evidence of left ventricular (LV) systolic dysfunction.1 However, the problem of defining heart failure arises in its milder forms where patients may complain of dyspnoea but do not have echocardiographic evidence of LV systolic dysfunction. The complexities of what represents heart failure are illustrated in fig 10.1 but space precludes a detailed discussion of the definition of heart failure.

To overcome the various difficulties in defining heart failure, the European Society of Cardiology (ESC) has developed guidelines for the diagnosis of heart failure.2 However, like all statements which are meant to define the undefinable, there is a certain deliberate vagueness about them. For example, they do not specify what they mean by cardiac dysfunction. Does an elderly lady whose echocardiogram meets criteria for "diastolic dysfunction" and who has swollen ankles have heart failure, even if she has no breathlessness or fatigue? Despite this caveat, the ESC guidelines have clarified the situation, even if one can still point to isolated patients who remain ambiguous with the ESC definition.

At a more pragmatic level, the clinician who is faced with a patient with suspected heart failure should try to answer two major questions:

1. Are the patient's symptoms cardiac in origin?

Figure 10.1. The various subcategories of heart failure.

European Society of Cardiology guidelines for the diagnosis of heart failure

• Essential features

1. Symptoms of heart failure (for example, breathlessness, fatigue, ankle swelling)

2. Objective evidence of cardiac dysfunction (at rest)

• Non-essential features

In cases where the diagnosis is in doubt, there is a response to treatment directed towards heart failure

2. If so, what kind of cardiac disease is producing these symptoms?

In order to answer these questions, the clinician goes through the standard process of assessing the patient's symptoms, then the patient's signs, and finally arranging appropriate investigations. Obtaining the answer to the above questions is much more complex than it is with some other disease. For example, absolute levels of blood glucose make or break the diagnosis of diabetes mellitus. Similarly, absolute levels of blood pressure decide whether a patient has hypertension or not (even if the cutoff values for blood pressure and blood glucose do change repeatedly). Heart failure is much more difficult because it is not definable by an absolute level of any one parameter. Even if one could define a set of echocardiographic criteria to make the diagnosis, experts would never agree on the cutoff values and, even if they did, echocardiography is much more subject to interobserver bias than is a blood glucose. In order to set the scene, it is also worth saying how poor clinicians are at diagnosing mild heart failure using purely symptoms and signs. This information comes from the many open access echo services which have been set up throughout the country. In these, general practitioners are asked to send up all patients whom they suspect may have heart failure. To the surprise of many, it was found that only 25% of those sent up had LV systolic dysfunction on their echocardiogram— that is, 75% had normal LV systolic function.3 4 This is not to criticise doctor's skills. Rather this says how non-specific are the symptoms and signs which classically lead us to suspect heart failure (table 10.1).5

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