Echocardiography is an ultrasound examination of the heart. A probe sends out sound waves that are reflected to different degrees by the heart muscle, the valves and the blood. A computer assembles the echoes into moving images. Unlike X-rays or computed tomography, this involves no radiation exposure.
The standard method is called transthoracic echocardiography: the sound reaches the heart through the chest. You usually lie on your left side, and a gel ensures good contact between skin and probe. Through the gaps between the ribs and from below the breastbone, the heart is imaged from several directions. Doppler technology also shows the direction and speed of the blood flow, so that narrowed or leaking valves stand out.
The findings answer many questions at once. How large are the chambers and atria, how thick are the walls? How strongly does the left ventricle pump, expressed as the proportion of blood ejected, the ejection fraction? Do individual sections of the wall move less, for example after a heart attack? Fluid in the pericardium, blood clots in the heart and signs of increased pressure in the pulmonary circulation can also be detected. Common reasons for the examination are shortness of breath, swollen legs, a heart murmur, arrhythmias, long-standing high blood pressure or monitoring a known heart condition.
Some questions call for special forms. In transoesophageal echocardiography (TOE), a thin probe is passed down the oesophagus to a position behind the heart. This shows the valves, atria and clots in great detail; the examination is carried out on an empty stomach, with the throat numbed and often with a sedative. In a stress echo, the heart is scanned under physical exertion or medication-induced stress to detect reduced blood flow. If the image quality is not sufficient, for example in lung disease, an ultrasound contrast agent can help.