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A brief overview of the development of coronary angioplasty
In this section we propose to give only a flavour of the historical development of coronary angioplasty and the context in which it emerged. Coronary artery disease (CAD) is the most common cause of death in developed countries. It is the end result of a process called atherosclerosis that occurs when atheroma or plaque forms on the inner layer of the coronary artery and impedes the flow of blood to the heart. In the early stages, the build up of these deposits is silent (symptom-less) but as the disease progresses chest pains of varying degree (angina) as well as shortness of breath occur; the eventual outcome could be a heart attack.[2]
As recently as the decade of the 1960s treatment options for angina (chest pain) or acute myocardial infarction (heart attack) consisted of few medications (mainly nitroglycerin in use from the mid to late 1800s to provide transient relief from angina by dilating vessels and enabling more blood to get to the heart), rest and hope. In the 1960s and 1970s respectively, two new classes of drugs (beta-blockers and calcium channel blockers) were added to the cardiologist’s arsenal for dealing with angina. But the 1960s heralded a new surgical treatment modality - coronary artery bypass surgery, which at the time was regarded as being truly revolutionary. This was based on the idea of stopping a heart, using a vessel harvested from another part of the body (upper leg) to restore the blood flow between those areas of the heart that were separated by the occlusion, and then restarting cardiac activity.
The technique spread rapidly[3] although the diffusion of this procedure was not without controversy and this was primarily related to the evidence base on which bypass surgery was being promoted. A debate raged throughout the 1970s about the quality of evidence that was being assembled about the efficacy of bypass surgery relative to medical therapy. In a review of the medical literature at the time Mullins and Lipscomb (1977) noted that analyses were based on incomplete studies or that some studies were less that ideally designed. Given the weight of evidence available they were hesitant to unambiguously recommend surgery other than in special cases.
The development of a new treatment modality
It is against this background of uncertainty about the efficacy of coronary bypass surgery that coronary angioplasty (formally, percutaneous transluminal coronary angioplasty or PTCA) was developed. While this achievement secured Gruentzig’s name in the annals of medical history, his key insight of using a balloon tipped catheter to dilate the diseased coronary artery was built around cardiac catherisation and transluminal angioplasty, already established medical techniques. The former is a diagnostic procedure in which a catheter (a thin flexible tube) is inserted into the right or left side of the heart. This could be then used to produce angiograms (x-ray images) of the coronary arteries and the left ventricle, the heart’s main pumping chamber, and/or used to measure pressures in the pulmonary artery and to monitor heart function. But by the 1950s, following the work of Cournand, Seldinger and others, diagnostic catherization had become established as the main technique for investigating cardiac function.
The second technique, transluminal angioplasty also known as ‘dottering’ after its developed Charles Dotter, consisted in the dilatation of occluded peripheral arteries by means of a catheter that inserted into the vessel to break the plaque. Gruentzig learned of the Dotter method during a seminar given by Zeitler, one of the European followers of Dotter, at the Ratchow Clinic in Darnstadt, Germany in the mid 1960s. He later moved to the University of Zurich and there, collected and evaluated a small series of ‘dotter’ cases. By the 1970s he was actively considering how this technique could be applied to the heart recognising that ‘any application of the dilatation procedure to other areas of the body would require technical changes’ (King 1996: 1624). Encouraged by his colleague and Joint Head of Cardiology, Wilhelm Ruttishauser, Gruentzig went on to develop a prototype balloon catheter, the foundation for PTCA. One of the challenges he had to overcome was to find the right material for the balloon. He experimented with several and by 1972 settled on a PVC balloon as he found this to be a tough, less compliant material than latex which he also considered. In 1975, he developed a single and then more importantly a double lumen catheter – one for inflating the balloon and the other for injecting contrast media and monitoring intravascular pressure. The following year (1976) he presented results based on animal experimentation to a less than enthusiastic audience at the American Heart Association meeting. Undaunted he succeeded in performing first PTCA on a human patient in Zurich in 1977. The technique gained credence and spread quickly thereafter particularly in the US.
The growth of practice was naturally associated with several improvements in devices and in practice including the invention of the steerable balloon catheter by Simpson in the early 1980s (Simpson, et al. 1982).[4] However, the structure of these many contributions to the innovation sequence also reflects the shift in the nature of the dominant problem. The solution to the catheter problem and Greuntzig’s balloon device to compress the plaque opened up new territory but it was soon found that restenosis - the re-narrowing of the artery after it has been treated - occurred in a significant number of patients drastically reducing the efficacy of the treatment and raising its real cost. The solution to this problem was the invention and innovation of the stent, an expandable metal device to give support to the blood vessel wall (Eeckhurst, Kappenbergen and Goy, 1996). Stenting cuts residual restenosis by over 50% and is a major complementary development in PTCA technology. However even this solution is not complete as restenosis can occur on the inside of the stent and subsequent attention shifted to the design of drugs to coat the stent that will prevent this occluding process (Serruys, et al, 1991; Lincoff, 2000; Suwaidi, et al, 2000).