Prof. Petros Nihoyannopoulos MD,FRCP
Professor of Cardiology,
Imperial College London
The year 2013 was the 60th Birthday of the founding of Echocardiography and the 160th anniversary since the death of Johann Christian Doppler (1803-1853). Those two events marked modern cardiology by not only shaping up a more accurate diagnosis of heart disease but also guiding patients’ management. Echocardiography has to be included among the top 10 greatest discoveries dating back to the discovery of piezoelectricity by Pierre and Jacque Curie (Curie and Curie 1880). Echocardiography was conceived in 1953 when Inge Edler, a physician from Lund University in Sweden, together with Hellmuth Hertz, a Swedish physicist and the son of a Nobel laureate in physics, performed the first human echocardiogram, which they called Ultrasound Cardiography (UCG) (Edler and Herz 1954). They used a shipyard sonar machine (Siemens Co, Germany) in Malmö that was used to detect structural flaws in boats, called ‘ultrasonic reflectoscope’, now in the Museum of Medical History in Lund. The images of the heart were crude and the knowledge of what it represented false. In October 1953, Edler and Hertz recorded the first ‘Ultrasound Cardiogram’ and published their findings the following year (Edler 1955; Edler 1956). Figure 1 shows one of the first echocardiographic recordings of the heart some 60 years ago. Edler went on to be a pioneer in echocardiography, while Hertz went on to invent the inkjet printer. There was little progress for a decade until 1963, when Harvey Feigenbaum, frustrated by the numerous limitations of cardiac catheterisation and angiography, borrowed an unused echoencephalography machine to scan the heart, and noticed that cardiac images could be recorded. He became the first person to describe pericardial effusion (Feigenbaum et al. 1965). By substituting ’cardio‘ with ’encephalo‘ it was this machine’s origins that gave the name ’echocardiography’.
In the meantime, in 1956 in Japan, Yoshida and Nimura were the first to apply the Doppler principle to cardiac recordings, but the resulting signals were wrongly interpreted as being caused by movements of the heart muscle and the valve leaflets. No signal was attributed to blood flow, and consequently the method was of little interest to cardiologists. It was not until 1969 that during the first World Conference of Ultrasonic Diagnosis in Vienna I. Edler and K. Lindstrom presented their ultrasound Doppler studies, including the first 40 clinical cardiac Doppler recordings for the evaluation of aortic and mitral regurgitation (Lindstrom and Edler 1969). Although cardiac Doppler was described fairly extensively in Europe, it was not until Holen (Holen and Simonsen 1979) and Hatle (Hatle and Angelsen 1985) showed that accurate haemodynamic data could be determined with Doppler ultrasound that Doppler revolutionised the non-invasive assessment of cardiac haemodynamics in clinical practice. Echocardiography and Doppler, better termed as ’Echocardiology‘ have expanded enormously and become an integral part of the diagnostic pathway for every patient with known or suspected heart disease.
Never before has the pace of innovations in echocardiography been so swift. Echocardiography today has been revolutionised alongside competition from other imaging modalities, such as cardiovascular magnetic resonance imaging and computer tomography. It is by far the most used cardiac imaging test, with over 23 million echocardiographic studies performed in the U.S. annually and 2.5 million stress echoes. The most common use is the assessment of ventricular function, valve disease and the haemodynamic assessment using Doppler, so that it has become essential in management of all forms of heart disease. The daily cardiac haemodynamic assessment is now based on Doppler haemodynamics for valve disease and diastolic function, while invasive haemodynamics are only reserved for when clinical discrepancies occur. That saves patients from unnecessary and potentially hazardous ionising radiation.
During the 1970s and 1980s, invaluable collaboration between engineers and physicians culminated in the development of two-dimensional echocardiography, Doppler echocardiography, colour-flow Doppler echocardiography and transesophageal echocardiography. In Europe Bom et al. (1973) developed a multi-element transducer to provide electronic linear grayscale scans of real-time two-dimensional cardiac images. More and more equipment manufacturers recognised the importance of developing their own transducers to be better matched with their equipment to provide high frontend compatibility and further improving image quality.
From the initial poorly understood M-mode echocardiographic recordings of the left ventricle, two dimensional echocardiography added spatial resolution to the imaging of the heart, and more clinicians were able to appreciate the anatomy and function of the heart, so that the method was adopted even by the most sceptical clinicians. Figure 2 is a four-chamber projection of the heart from the apex, clearly demonstrating the relative chamber sizes and valves. Notice the presence of an organised apical thrombus at the apex (arrow). However, while imaging quality continued to improve, two-dimensional echocardiography could not always match the clarity of some of the cardiac magnetic resonance imaging as it entered the clinical arena and some sceptics thought that cardiac MRI was the reference technique and that echocardiography was a technique of the past. How wrong they were!
Figure 4. Transoesophageal surgical view of the mitral valve. Superimposed is the mitral leaflet segmentation. A=Anterior, AL=anteriorlateral commissure, Ao= aorta, A1 anterior leaflet lateral segment, A2= anterior leaflet middle segment, A3= anterior leaflet medial segment, P=posterior, PM= posteromedial commissure, P1=Posterior leaflet lateral segment, P2=posterior leaflet middle segment, P3=posterior leaflet medial segment.
Figure 5. (Left) Transoesophageal surgical view of the mitral valve leaflets depicting the anterior leaflet and the posterior leaflet. Note the deep cleft identified in the region of P3 (arrow).