Hydrogen Sulfide and Peripheral Arterial Disease

This will be an observational study comparing the plasma levels of free hydrogen sulfide in patients with and without peripheral arterial disease using a novel recently published method of measuring hydrogen sulfide. The investigators will also see if there is any difference in these levels between symptomatic and asymptomatic patients. Will examine the relationship of these levels to known clinical risk factors as well as plasma nitrite and nitric oxide levels. In doing the above the investigators hope to explore the utility of free hydrogen sulfide as a biomarker for peripheral arterial disease. Atherosclerotic peripheral arterial disease (PAD) of the lower extremities represents a significant and growing cause of morbidity and mortality. The PARTNERS study of screening ABIs in a primary care population of nearly 7000 individuals demonstrated a remarkable 29% incidence of ABI \<0.9, which is the commonly accepted level of abnormal ABI diagnostic of PAD. Also of note in these patients with a new diagnosis of PAD the incidence of asymptomatic PAD was a striking 48%. The availability of a biomarker will greatly enhance the care of these patient and hopefully reduce morbidity and mortality. The investigators believe that hydrogen sulfide (H2S), an endogenously produced gasotransmitter, holds promise as a clinically useful biomarker for PAD and may also provide a possible explanation for the paradox of asymptomatic PAD in patients with ABIs less than 0.9. To date, research regarding H2S has demonstrated that it participates in a myriad of physiological functions including vasodilatation, anti-apoptotic effects, modulation of mitochondrial respiration, and changes in vascular remodeling.