HISTORY AND EXAMINATION

There are many causes of breathlessness (see Box 6.1). Everyone is breathless at times, but people who are physically unfit or who are overweight will be more breathless than others. Breathlessness can also result from anxiety, but when it is due to physical illness the important causes are anaemia, heart disease and lung disease; a combination of causes is common. Apart from ischaemia (see Ch. 5), cardiac diseases causing breathlessness include valve disease, cardiomyopathy, and myocarditis including acute rheumatic fever. Boxes 6.2–6.6 summarize the effects of these conditions on the heart, and the corresponding ECG features. The most important function of the history is to help to determine whether the patient does indeed have a physical illness and, if so, which system is affected.

Breathlessness in heart disease is due to either increased lung stiffness, as a result of pulmonary congestion, or pulmonary oedema. Pulmonary congestion occurs when the left atrial pressure is high. A high left atrial pressure occurs either in mitral stenosis or in left ventricular failure. Pulmonary oedema occurs when the left atrial pressure exceeds the oncotic pressure exerted by the plasma proteins.

Congestive cardiac failure (right heart failure secondary to left heart failure) can be difficult to distinguish from cor pulmonale (right heart failure due to lung disease). With both, the patient is breathless. Both are associated with pulmonary crackles in left heart failure due to pulmonary oedema, and in cor pulmonale due to the lung disease. Also in both, the patient may complain of orthopnoea. In heart failure, this is due to the return to the effective circulation of blood that was pooled in the legs. In patients with chest disease (especially chronic obstructive airways disease), orthopnoea results from the need to use diaphragmatic respiration. Both pulmonary congestion and lung disease can cause a diffuse wheeze. The diagnosis therefore depends on a positive identification, either in the history or on examination, of heart or lung disease.

The main value of the ECG in patients with breathlessness is to indicate whether heart disease of any sort is present, and whether the left or the right side of the heart is affected. The ECG is best at identifying rhythm abnormalities (which may lead to left ventricular impairment and so to breathlessness) and conditions affecting the left ventricle particularly ischaemia. The patient with a completely normal ECG is unlikely to have left ventricular failure, though of course there are exceptions. Lung disease eventually affects the right side of the heart, and may cause ECG changes suggesting that significant lung disease is present.

RHYTHM PROBLEMS

A sudden rhythm change is a common cause of breathlessness, and even of frank pulmonary oedema. Arrhythmias can be paroxysmal, so the patient may be in sinus rhythm when examined, and a patient who is suddenly breathless may not be aware of an arrhythmia. When sudden breathlessness is associated with palpitations it is important to establish whether the breathlessness or the palpitations came first palpitations following breathlessness may be due to the sinus tachycardia of anxiety. The ECG in Figure 6.1 is from a patient who developed pulmonary oedema due to the onset of uncontrolled atrial fibrillation.

Less dramatic rhythm abnormalities can also contribute to breathlessness, especially to breathlessness on exertion. This is true of both fast and slow rhythms. The ECG in Figure 6.2 is from a patient who had atrial fibrillation but who was breathless on exercise partly because of coupled ventricular extrasystoles, which markedly reduced cardiac output as a result of an effective halving of the heart rate.

THE ECG IN DISORDERS AFFECTING THE LEFT SIDE OF THE HEART