Medicine and multimedia: Evidence Based Cardiology
Authors: John R Hampton
Journal: BMJ (1998)

Studies comparing clinical practice in different countries always show a remarkable lack of consistency in the way patients are treated. In cardiovascular disease there is a huge variation in, for example, the use of coronary angiography and percutaneous transluminal coronary angioplasty after acute myocardial infarction, and even in the use of relatively cheap treatments such as digoxin and diuretics in patients with heart failure. Why should this happen? The medical community is international, there is little debate about which are the leading journals, everyone goes to the same international meetings, and everyone has essentially the same access to the evidence on which treatment is supposedly based. One would have thought that there would be considerable consistency in the investigation and treatment of patients with cardiovascular disease in countries at a similar stage of educational and economic development, but this is not the case.

The problem presumably lies in doctors’ perceptions of what constitutes evidence that is good enough to be the basis of medical practice. If this were not so “consensus conferences” would be needed in only areas where there is essentially no evidence about the efficacy of treatment. In most circumstances, however, there is plenty of published evidence about different treatment strategies, and what consensus conferences actually do is to evaluate published literature. Consequently, what constitutes consensus varies, and not all published guidelines on treatment are identical.

A weighty book impressively titled Evidence Based Cardiology can thus represent only a particular view of evidence, and grading the value of such evidence into categories A, B, and C does not necessarily provide a vision of absolute truth. As with most devotees of evidence based medicine, the authors are strong on reviews of published clinical trials but weak on philosophy. As usual, they place much emphasis on meta-analysis, although to many people this is now a somewhat discredited technique for analysing trials. They scarcely consider the possibility that patients included in clinical trials may be atypical of those seen in the real world so that, however statistically significant the results of a trial may be, it can be almost impossible to assimilate them into daily practice. The concept of equivalence of treatments does not get a mention, and there is little about cost effectiveness as an important component of evidence based practice. 

Some of the treatments recommended on the basis of grade A evidence may raise some eyebrows. Just because the huge ISIS-4 trial showed a small benefit from treatment with angiotensin converting enzyme inhibitors in unselected patients with acute myocardial infarction, should we really accept that all such patients should be given these drugs routinely in addition to all the other treatments of proved benefit? Surely the benefit in ISIS-4 was mainly in those with left ventricular dysfunction. How many people would accept that primary angioplasty in myocardial infarction is an alternative to thrombolysis in the real world? All the primary angioplasty trials have had such low fatality rates that the included patients must be atypical. Can most patients with mitral stenosis really be treated successfully with balloon angioplasty (grade B evidence), or is this a view from centres dealing only with young patients and non-calcified valves? Certainly, a recent consensus conference by the Royal College of Physicians of Edinburgh on the management of atrial fibrillation came up with different interpretations of published evidence from those described in this book: for example, on the value of left atrial size in deciding whether a patient should receive long term treatment with anticoagulants.


Any review represents a perception of events at a point in time. This book is certainly heavy (3.2 kg), but it is no tablet of stone. At present it is right up to date, but next month it will be out of date. As our view of evidence based medicine becomes more sophisticated and realistic, it will perhaps be seen to represent the zenith of a particular phase of development of medical science. It will, in other words, become an architectural—or even an archaeological—monument.  


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