June 18th, 2012
Selections from Richard Lehman’s Literature Review: June 18th
CardioExchange is pleased to reprint selections from Dr. Richard Lehman’s weekly journal review blog at BMJ.com. Selected summaries are relevant to our audience, but we encourage members to engage with the entire blog.
JAMA 13 June 2012 Vol 307
Imaging Risks (pg. 2400): We know surprisingly little about the long-term effects of low-dose ionizing radiation. This became a matter of intense debate during and after the era of above-ground nuclear weapons testing, and much of what we know about the subject is based on extrapolation from the effects of the weapons detonated over Hiroshima and Nagasaki. It is very hard to quantify the cumulative effects of exposure to diagnostic X-rays and to work out the benefit/harm ratio from this exposure: all that this study and others can tell us is that such exposure in advanced health systems is steadily increasing, mainly due to the use of CT scanning. In large integrated health systems in the USA, use of this modality more than doubled between 1996 and 2010.
NEJM 14 June 2012 Vol 366
Oral Contraception, MI, and Stroke (pg. 2257): Oral contraception began as a massive natural experiment in the 1960s, and it is one we are still learning from. Where better to go than Denmark, which has a superb National Registry of Patients and Register of Medicinal Products Statistics: combine the two and you can get data relating to 1,626,158 women, with 14,251,063 person-years of observation. Øjvind Lidegaard and a team of four crunched the numbers to give us the most detailed picture yet of the risk of myocardial infarction and thrombotic stroke attributable to each type of oral contraception. The type of progestin seems to make little difference, but the dose of oestrogen probably does. Pills with the standard dose of 30 mcg of ethinyl oestradiol may roughly double the risk of MI and thrombotic stroke in this population. This equates to about 1-2 extra events per 10,000 women annually. The title of the editorial sums it up: Hormonal Contraceptives and Arterial Thrombosis — Not Risk-free but Safe Enough.
Arch Intern Med 11 June 2012 Vol 172
Never Too Old to Quit (pg. 837): Richard Doll famously said that death in old age is inevitable, but death before old age is not inevitable. Amongst the avoidable factors he was referring to, smoking remains the most obvious, and after sixty years of preaching on the subject, he must be sighing in his grave to read yet another study proving that this is still so, regardless of where you set the threshold for “old age”. This systematic review shows that the mortality benefit of giving up can be seen even beyond the age of 80.
Wasteful Cardiovascular Tests (pg. 854): Less is More is the most essential series in any journal: not perhaps for its originality, not for its academic content, but simply because it carries the most important messages for all developed health systems. The drive to do useless things is nowhere near as strong in the NHS as in the pay-by-item American systems, but it happens all the time for all that. Exercise echocardiography in asymptomatic patients following coronary revascularization at any time following the procedure makes no difference to outcomes. It is a waste of resources and should not be done.
(pg. 837): The same can be said for a lot of stress testing following admission for chest pain in US hospitals. In one tertiary hospital, the authors found that “most patients who are admitted with low-risk chest pain undergo stress testing, regardless of pretest probability, but abnormal test results are uncommon and rarely acted on.” The need to factor in pre-test probability is a lesson that never seems to get learnt sufficiently.