On The Pulse - 22nd June 2012

Pre-diabetes
A systematic review of stroke in people with pre-diabetes in the BMJ can be interpreted in contradictory ways. Some journals took the view that it showed that millions of people were at higher risk. Dr Lydgate, who isn’t alone in thinking that the rebranding of impaired glucose tolerance as pre-diabetes is a marketing trick to provide a huge pool of potential patients for unnecessary pharmacological intervention, takes a more sceptical view. After excluding studies that might have enrolled people with undiagnosed diabetes, the systematic review estimated the relative risk of stroke at 1.2 (95%CI 1.02–1.44), and as the investigators admit, this modest association could easily be due to confounding rather than cause and effect.

Oral contraception and thromboembolism
How much hormonal contraceptives predispose to thromboembolic complications is debated, but a huge study in the NEJM provides some reassurance. Data were extracted from the Danish National Registry of Patients for the entire female population aged 15–49 years (1.6 m patients), from 1995 to 2009. Thrombotic stroke and myocardial infarction were increased by factors of 0.9–1.7 with oral contraceptives that included 20 μg ethinyl estradiol and 1.3–2.3 with those containing 30–40 μg, but the absolute risk increases were small. An accompanying Editorial agrees that while oral contraceptives are not risk-free, they are safe enough.

Escalating rates of diagnostic imaging
As diagnostic imaging gets better and better, it’s used more and more. A survey from the USA in JAMA reports a 3-fold increase within the last 15 years and rates now average more than one imaging investigation per person annually. The corollary of course is a substantial increase in exposure to ionizing radiation. Four percent of people surveyed had received a dose of >50 mSV in the past year, which is 20 times the background radiation. As a paper in the BMJ pointed out last year, iatrogenic radiation needs to be taken more seriously. Are all those CT scans really necessary?

The 6-minute walk test
A study in Archives of Internal Medicine uses the distance walked in 6 minutes, going at their own speed, to assess 556 patients with stable coronary heart disease. The top quartile of tested patients walked 544 to 837 m – for every 100 m less, the risk of a cardiovascular event during a median 8.0 years of follow-up increased by 55%, independent of conventional risk factors. Those unable to complete the test were at similar risk to the bottom quartile. An accompanying Commentary reckons this is as informative as treadmill testing, but easier, cheaper and notably safer.

Subsidised chocolate
Dark chocolate has antihypertensive, anti-inflammatory, antithrombotic and metabolic effects, which are attributed to its high polyphenol content. Observational studies and short-term RCTs have shown that regular consumption reduces systolic blood pressure and plasma cholesterol concentrations. An Australian study in the BMJ takes this to a logical, if faintly ludicrous, conclusion with a Markov modelling analysis showing that dark chocolate consumption would be cost effective in the primary prevention of cardiovascular events. Chocolate doesn’t have such a large effect as statins or ACE inhibitors but perhaps this would be offset by better compliance and fewer adverse effects.

Short-term anti-arrhythmic treatment after cardioversion
While anti-arrhythmic drugs reduce recurrence in people with atrial fibrillation treated by electrical cardioversion, they are associated with potentially serious side effects such as ventricular proarrhythmia. A trial in the Lancet compares short-term (4 weeks) and long-term (6 months) treatment with none at all, in ~600 patients with persistent atrial fibrillation undergoing planned cardioversion. The investigators’ hypothesis that short-term treatment would be enough was largely confirmed, with ~50% event-free at 6 months, but long-term treatment remained slightly superior. An accompanying Comment thinks short-term treatment should be considered if adverse events are a particular concern.

Growing a new vein
Conventional approaches to vascular replacement either use autologous tissue such as saphenous vein or synthetic materials such as Dacron and ePTFE, and are vulnerable to stenosis and thrombosis in the long-term. A case study in the Lancet describes how a 10-year-old girl with extrahepatic portal vein obstruction was given a bypass using decellularized iliac vein from an allogeneic donor that was subsequently recellularised using endothelial and smooth muscle cells grown from the recipient’s own stem cells. As an accompanying Comment says, very few patients will qualify for this expensive and complex procedure, and the long-term outcome is uncertain, but this may be an important advance.

Medical narratives
Many doctors think that narratives are as necessary as science in the practice of clinical medicine, and a thoughtful piece in JAMA argues that, if stories are important, then so is telling them well. Truth isn’t only communicated by complete fidelity to facts, and the way in which a story is told is inseparable from its meaning. Clinical stories, such as those told in BMJ fillers or Annals of Internal Medicine’s On Being a Doctor, are often unsatisfying and unconvincing; this article begins to explain why.