US Preventive Services Taskforce just published their guidelines for peripheral arterial disease screening with ankle-brachial index (ABI) — see link: http://www.uspreventiveservicestaskforce.org/uspstf12/pad/padfinalrs.htm). they do not find sufficient evidence to recommend routine screening, though point out:
–PAD common, with recent NHANES survey showing that 5.9% of US population >40 years old have ABI <0.9, most of whom are asymptomatic
–PAD is a marker for coronary heart disease (approx 2-fold increased risk – see JAMA. 2008;300(2):197-208, which found twice the 10-year mortality in those with PAD), and is independent of traditional risk factors. adding PAD to the framingham risk score would result in reclassification of patient risk as follows: for men, who get more PAD at an earlier age, 19% were reclassified, mostly by a normal ABI resulting in high risk decreasing to intermediate risk; in women, there was a 36% reclassification rate, mostly from low to intermediate or high risk based on low ABI) — but there are no data that this reclassification and potentially changed treatment would affect clinical outcomes. one study in JAMA (2010; 303(9):841-8) did not show that aspirin was effective in general population with low ABI. USPSTF comments that there are no studies addressing lipid-lowering in patients without known diabetes or CAD (one point of the guidelines is whether the testing would alter therapy; diabetics and patients with CAD should already be on lipid-lowering meds and probably aspirin anyway). [there actually are a couple of studies – one small study of patients with severe PAD who did have a survival benefit with statins and another larger study of patients also found a mortality benefit, but this study had patients with many different underlying medical problems (44% with CAD) and didn’t perform subgroup analysis. so, there are some data suggesting statins do confer cardioprotection in those with PAD.]
coincidentally, the european cardiology conference this month reported the results of the REACH trial (reduction of atherothrombosis for continued health) registry in patients with symptomatic PAD. full report not available for evaluation, but i am bringing it up given the above guidelines. basically:
–5861 patients with established symptomatic PAD assessing 4-year data.
–primary outcome (localized) — worsening claudication or new episode of critical limb ischemia, revascularization or amputation. secondary outcome (systemic) — cardiovascular death, nonfatal MI and nonfatal stroke.
–3643 on statin and 2218 not. (note: this is not an intervention trial)
–adverse limb outcomes: occurred in 22% of those on statin and 26.2% not on statin (unadjusted rates), with 14.7 vs 18.2% with worsening claudication or critical limb ischemia; 18.2% vs 21.7% with revascularization; 3.8% vs 5.6% with amputation
–adverse systemic outcomes: 19.6 vs 20.3% with total cardiovasc outcomes; 17.3 vs 19.7% all-cause mortality; 11.4 vs 12.4% cardiovascular mortality; 5 vs 4.6% nonfatal MI; 6 vs 6.8% nonfatal stroke. — unclear how statistically significant this is. [though these numbers don’t show much improvement with statins, unlike the 25-30% risk reduction in the CAD trials]
so, what makes sense here??? it is true from several studies that PAD is associated with CAD. one would think this to be true whether the PAD were symptomatic or not. adding PAD to the framingham risk score seems to reclassify a lot of people. and statins do seem to improve walking distances and decrease need for limb revascularization. (also, see article showing that ramipril increases walking distances in dropbox, or JAMA. 2013;309(5):453-460). i would suggest the following:
–would not screen for PAD in asymptomatic patients, given the above-noted lack of good data.
–statins should be part of treatment for symptomatic PAD (one reason i brought this study up is the pretty surprising finding that >1/3 of the patients in this registry with symptomatic PAD were not on statins), esp if LDL is >100.
geoff