May 14th, 2012
Selections from Richard Lehman’s Literature Review: Week of May 14th
Richard Lehman, BM, BCh, MRCGP
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 9 May 2012 Vol 307
Glucose, Insulin, and Potassium for MI (pg. 1925): In a wonderful letter to Humphry Davy in 1800, Coleridge declared that science, as a human activity, “being necessarily performed with the Passion of hope, is poetical”. All good science is inspired with the poetry of hope; but, alas, so also is a lot of bad science. If results are negative, then it is a lot easier to hope vainly that they contain hints of great things to come than to admit that years of effort have simply proved nullity. And if a simple cheap intervention like intravenous glucose, insulin, and potassium (GIK) seems to have promise in the treatment of acute myocardial infarction, all of us would much rather hope this is true than dismiss the possibility altogether. Several randomized trials have proved that GIK makes no difference when given in hospital, so this double-blinded RCT investigates whether the same applies to GIK given by emergency service personnel to patients with presumed cardiac chest pain before arrival at hospital. Again, there was no 30-day mortality benefit; but since (as a poet before Coleridge said) hope springs eternal in the human breast, the investigators draw attention to the fact that GIK was associated with lower rates of the composite outcome of cardiac arrest or in-hospital mortality. Nah, that won’t quite do: when I have a myocardial infarct, I want to be alive at 30 days. This intervention is beyond hope: GIK RIP.
NEJM 10 May 2012 Vol 366
Elective PCI without Surgical Standby (pg. 1792): I have had a lot of exposure to US cardiovascular outcomes research over the last year, and very enjoyable and formative it has been. I’m left convinced that there is no particular hierarchy of research in this area: good observational studies can be of the highest value, and qualitative or mixed-methods research can yield much more of practical value than some clever exercise in endless statistical adjustment and regression applied to a large database. Randomized controlled trials are relatively uncommon in this field, so while they do not automatically count as top dog, they are always interesting. Given that elective percutaneous intervention is now a procedure with very small immediate risks (e.g. acute MI, dissection of the coronary artery), PCI is often performed in hospitals without on-site cardiac surgery. If this interests you deeply, you can read all about it in a review on p.1814. This massive trial (n=18,867) randomized patients needing PCI on a 3:1 basis to hospitals with or without cardiac surgery units. Readers who object to the word noninferiority must clench their teeth at this point, because that is what this trial showed. And anyone who claims that this word does not belong in the English language will be sent a punitive stream of e-mails until they beg for mercy.
BMJ 12 May 2012 Vol 344
Varenicline and Cardiovascular Risk: That smoking cessation is a great good is undeniable, and varenicline undeniably helps many people to stop smoking. Does it therefore follow that varenicline is a great good? This is a nice debating point, because smoking cessation is actually a surrogate end-point, albeit one directly linked with certain outcome benefits; yet these benefits can be outweighed by other considerations, such as direct cardiovascular harm from the intervention itself. A previous meta-analysis seemed to show a 72% increase in risk of serious CV events from taking varenicline: this one shows no increase in risk. The main reason is ascertainment bias in the trials which had poor follow-up data from placebo groups; but the fact remains that we can never be full sure until the manufacturer releases full individual data from its trials for independent scrutiny, as should be mandatory in all cases like this.