Homocysteine and Progression of Atherosclerosis

BACKGROUND:

Few studies of progression of atherosclerotic peripheral vascular disease have been performed and none have used objective methods to evaluate disease progression in a large number of symptomatic subjects. The study is of obvious major clinical importance. Elevated plasma homocysteine is well established as an independent risk factor for atherosclerosis. If folate treatment results in less frequent/rapid progression of peripheral vascular disease, then it will be confirmed as the first effective treatment for atherosclerosis which is without toxic side effects and does not involve major changes in life/dietary habits.

DESIGN NARRATIVE:

The Homocysteine and Progression of Atherosclerosis Study (HPAS) is a long term, prospective, blinded, multifactoral clinical study which began in 1991 to study the relationship between elevated plasma homocysteine (HC) as well as a number of other risk factors and PVD progression. The study is divided into two phases, conducted sequentially upon 400 patients with symptomatic lower extremity (LED) and cerebrovascular disease (CVD). The first phase was a three year natural history study in which relationship of progression of peripheral vascular disease to plasma homocysteine and other risk factors was established. The clinical question addressed by the natural history study was: Do patients with symptomatic peripheral vascular disease and elevated plasma homocysteine have more rapid/frequent progression of peripheral vascular disease than patients with symptomatic peripheral vascular disease and normal plasma homocysteine? Progression of disease was assessed by the primary outcome variables of ankle brachial pressure index and degree of carotid artery stenosis, as determined in the noninvasive vascular laboratory, and by secondary outcome variables including vascular death, need for vascular surgery, stroke, myocardial infarction, amputation, and other clinical events. All outcome variables were determined by investigators blinded to the results of plasma homocysteine testing.

The second phase of the study, which began in August, 1995, is a blinded, prospective, randomized, placebo-controlled trial of folic acid treatment of elevated plasma homocysteine in the same patient population. Folic acid treatment has been demonstrated to result in normalization of elevated plasma homocysteine. The treatment trial addresses the clinical question: Do patients with symptomatic peripheral vascular disease and elevated plasma homocysteine treated with folate have less frequent/rapid progression of peripheral vascular disease than patients with symptomatic peripheral vascular disease and elevated plasma homocysteine treated with placebo? Although the second phase is described as a clinical trial, the Surgery and Bioengineering Study Section describes it as clinical research, not an NIH-defined Phase III trial.