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Images of the heart.

Most heart disorders can be diagnosed from the history and clinical examination. But the severity-and therefore the prognosis and appropriate treatment-cannot always be judged on clinical grounds alone. The size and position of congenital defects, the haemodynamic results of valve lesions, the site of coronary arterial stenoses, and the effect of these disorders on cardiac function are all important for proper management. Of course, an intelligent guess can often be made at the bedside, but nowadays a more accurate assessment can be made with modern techniques of cardiac imaging. The benefits of any investigation have to be balanced against the risks. The plain chest radiograph remains popular because it is familiar, painless, and practically harmless. It enables us to gauge the overall heart size, presence of valve calcification, left atrial enlargement, and pulmonary congestion. Its chief value is to detect change, especially in heart size. Similar comments apply to cardiac screening, but this does not leave a permanent record and is largely outmoded. The other traditional method of visualizing the heart is contrast angiography, which is always combined with the measurement of intracardiac pressures. Cardiac catheterization is uncomfortable, sometimes distressing, and occasionally hazardous. Its role is changing,' but it is still essential when the severity of a lesion is in doubt despite the results of other imaging techniques and when coronary arteriography is required. This latter indication is the more common, so much so that an alternative method of visualising the coronary arteries would put most diagnostic catheter laboratories out of business. Within the past decade the quality of echocardiographic images has improved from Polaroid photographs of limited value to excellent strip-chart recordings depicting the movement and thickness of the heart valves, the interventricular septum, and the left ventricular posterior wall and the minor diameter of the ventricular cavities. Abnormalities such as pericardial effusion, left atrial myxoma, and vegetations on the valves can be detected, often with ease and always without harm or discomfort to the patient. It is, indeed, the development of this technique that has led to the decline of cardiac catheterization before valve surgery in some centres.2 Since by no means everyone can produce such good echocardiographs the chief value of the echocardiogram in other centres will remain confirmation of the presence of a disorder rather than assessment of its severity.3 The single piezoelectric crystal of the echocardiographic