Lipid-lowering for peripheral arterial disease of the lower limb

Atheroma (fatty deposits) in the walls of the arteries to the legs can lead to peripheral arterial disease with insufficient blood flow to the muscles and other tissues. People with peripheral arterial disease often do not have symptoms. The most common symptom is intermittent claudication, which is characterised by leg pain and weakness brought on by walking, with disappearance of the symptoms following a brief rest. Lipid-lowering therapies may reduce cardiovascular events and worsening of local disease for people with lower limb peripheral arterial disease. They are recommended to people with coronary artery disease, for prevention of myocardial infarction and stroke.

Eighteen randomised controlled trials were included in the review, involving a total of 10,049 participants (78% were men) from seven different countries. The trials compared lipid-lowering therapy with placebo or usual treatment for at least 90 days. They differed considerably in the inclusion criteria, outcomes measured, and type of lipid-lowering therapy used. Lipid-lowering therapies improved walking distance. The effect of lipid-lowering therapy on death from any cause in people with peripheral artery disease was inconclusive. Using drugs to lower blood lipids had a beneficial effect on the incidence of total cardiovascular events, due primarily to an overall reduction in coronary events (OR 0.8; 95% Confidence Interval 0.7 to 0.9). The only type of drug for which consistent, clear evidence of a beneficial effect on total cardiovascular events, total coronary events and stroke was available, was the statins. The greatest evidence was with simvastatin in people with a blood cholesterol level of at least 3.5 mmol/litre. The evidence on side effects was inconclusive in these trials.

Authors' conclusions: 

Lipid-lowering therapy is effective in reducing cardiovascular mortality and morbidity in people with PAD. It may also improve local symptoms. Until further evidence on the relative effectiveness of different lipid-lowering agents is available, use of a statin in people with PAD and a blood cholesterol level ≥ 3.5 mmol/litre is most indicated.

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Background: 

Lipid-lowering therapy is recommended for secondary prevention in people with coronary artery disease. It may also reduce cardiovascular events and/or local disease progression in people with lower limb peripheral arterial disease (PAD).

Objectives: 

To assess the effects of lipid-lowering therapy on all-cause mortality, cardiovascular events and local disease progression in patients with PAD of the lower limb.

Search strategy: 

The authors searched The Cochrane Peripheral Vascular Diseases Group's Specialised Register (last searched February 2007) and the Cochrane Central Register of Controlled Trials (CENTRAL) (last searched Issue 2, 2007) for publications describing randomised controlled trials of lipid-lowering therapy in peripheral arterial disease of the lower limb.

Selection criteria: 

Randomised controlled trials of lipid-lowering therapy in patients with PAD of the lower limb.

Data collection and analysis: 

Three authors independently assessed trial quality and extracted data.

Main results: 

Eighteen trials were included, involving a total of 10,049 participants. Trials differed considerably in their inclusion criteria, outcomes measured, and type of lipid-lowering therapy used. Only one trial (PQRST) reported a detrimental effect of active treatment on blood lipid/lipoprotein levels.

The pooled results from all eligible trials indicated that lipid-lowering therapy had no statistically significant effect on overall mortality (Odds Ratio (OR) 0.86; 95% Confidence Interval (CI) 0.49 to 1.50) or on total cardiovascular events (OR 0.8; 95% CI 0.59 to 1.09). However, subgroup analysis which excluded PQRST showed that lipid-lowering therapy significantly reduced the risk of total cardiovascular events (OR 0.74; CI 0.55 to 0.98). This was primarily due to a positive effect on total coronary events (OR 0.76; 95% CI 0.67 to 0.87). Greatest evidence of effectiveness came from the use of simvastatin in people with a blood cholesterol ≥ 3.5 mmol/litre (HPS).

Pooling of the results from several small trials on a range of different lipid-lowering agents indicated an improvement in total walking distance (Mean Difference (MD) 152 m; 95% CI 32.11 to 271.88) and pain-free walking distance (WMD 89.76 m; 95% CI 30.05 to 149.47) but no significant impact on ankle brachial index (WMD 0.04; 95% CI -0.01 to 0.09).

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