Photoplethysmographic assessment of pulse wave reflection -: Blunted response to endothelium-dependent beta2-adrenergic vasodilation in type II diabetes mellitus

OBJECTIVES We sought to determine whether a simple index of pressure wave reflection may be derived from the digital volume pulse (DVP) and used to examine endothelium-dependent vasodilation in patients with type II diabetes mellitus. BACKGROUND The DVP exhibits a characteristic notch or inflection point that can be expressed as percent maximal DVP amplitude (IPDVP). Nitrates lower IPDVP, possibly by reducing pressure wave reflection. Response of IPDVP to endothelium-dependent vasodilators may provide a measure of endothelial function. METHODS The DVP was recorded by photoplethysmography. Albuterol (salbutamol) and glyceryl trinitrate (GTN) were administered locally by brachial artery infusion or systemically. Aortic pulse wave transit time from the root of the subclavian artery to aortic bifurcation (T-Ao) was measured by simultaneous Doppler velocimetry. RESULTS Brachial artery infusion of drugs producing a greater than threefold increase in forearm blood flow within the infused limb was without effect on IPDVP whereas systemic administration of albuterol and GTN produced dose-dependent reductions in IPDVP. The time between the first and second peak of the DVP correlated with T-Ao (r = 0.75, n = 20, p < 0.0001). The effects of albuterol but not GTN on IPDVP were attenuated by N-G-monomethyl-L-arginine. The IPDVP response to albuterol (400 mu g by inhalation) was blunted in patients with type II diabetes mellitus as compared with control subjects (fall 5.9 +/- 1.8% vs. 11.8 +/- 1.8%, n = 20, p < 0.02), but that to GTN (500 mu g sublingually) was preserved (fall 18.3 +/- 1.2% vs. 18.6 +/- 1.9%, p = 0.88). CONCLUSIONS The IPDVP is influenced by pressure wave reflection. The effects of albuterol on IPDVP are mediated in part through the nitric oxide pathway and are impaired in patients with type II diabetes. (C) 1999 by the American College of Cardiology.