October 1st, 2012
Selections from Richard Lehman’s Literature Review: October 1st
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.
Arch Intern Med 24 Sep 2012 Vol 172
Physical Activity and Mortality in Those with Diabetes:
Of Exercise I sing, and that benignant sweat
Which from six thousand diabetic brows
Exudes. My pen, Hygeia, speed! To save
That honey-urined tribe from mortal pains
Which Indolence doth breed, and glut of food:
That to the treadmill they may go, or healthful jog,
Or bicycle with ever-turning wheel;
These strivings, Muse, assist me to exhort,
That to the height of this great Argument
I may assert eternal Exercise:
For sloth in diabetes hastens death.
I beg your pardon: I was just trying to think of an EPIC way to convey the message of this paper about the mortality benefit of exercise in a cohort of 5859 diabetic individuals followed up from 1992 onwards in the European Prospective Investigation Into Cancer and Nutrition (aka EPIC). I know there’s confounding and reverse causality to be considered, but the burden of all such studies is always the same: even small amounts of regular exercise buy large amounts of added life.
Intensive and Standard BP Targets in Those with Type-2 Diabetes (pg. 1301): Nothing else in diabetes is as straightforward as the benefit of exercise: blood pressure control in type 2 DM for example, is a subject of such intellectual complexity that I sometimes think only Rod Hayward really understands it. The message of this systematic review and meta-analysis seems to be fairly clear: if you set a target BP with an upper limit of 130/80 rather than 140-160/85-100, you will reduce stroke but have no significant effect on total mortality or myocardial infarction. That may be all that a jobbing clinician needs to remember, but if you drill down just a little deeper, things get a good deal more complex. There is no simple—or even complicated—formula that can just give you a read out of numbers needed to treat for risk reduction in type 2 diabetes with hypertension. You must always consider the totality of cardiovascular risk in the individual patient. If you really want to engage with this, combine this study’s findings with the classic Timbie, Hayward and Vijan modelling paper from 2010.
JAMA 26 Sep 2012 Vol 308
Diagnostic Accuracy of FFR from CT Angiography: Interventional cardiologists with itchy fingers will all be citing the FAME study (see NEJM two weeks ago) as a reason to put wires in coronary arteries to measure fractional flow reserve (FFR) in stable coronary artery disease. I promised at the time that I wouldn’t comment further on something so far removed from my own field of practice. Here, however, is a technique for measuring FFR without an invasive procedure, unless you count a hefty dose of ionizing radiation as invasive. It is our old friend coronary computed tomographic (CT) angiography with some extra computing thrown in. In this multinational study, 252 patients with stable CAD underwent both CT scanning and invasive FFR measurement with adenosine stimulation. So this is a nice example of a diagnostic study with a simple gold standard: you can plug the figures into your 2×2 table and come up with specificity (73%), sensitivity (90%) and all the rest. Or you can construct a receiver operator curve (AUC, 0.81). Either way, CT derived FFR doesn’t quite cut the mustard. Further refinement might give us more accuracy, but for now, I struggle to think of a clinical use for this imaging modality. People with stable CAD should keep taking their tablets and try to avoid cardiologists with itchy fingers or shiny new CT machines.