Arterial Stiffness and Peripheral Arterial Disease

Michel E. Safar

The Diagnosis Center, Hotel-Dieu Hospital, Paris, France

Abstract

Of the atherosclerotic diseases, peripheral arterial disease is the most characterized by its association with systolic hypertension, increased arterial stiffness and disturbed wave reflection. This disease raises the question to which extent sclerosis in 'atherosclerosis' is necessary per se to cause an increase in systolic blood pressure.

Copyright © 2007 S. Karger AG, Basel

Arteriosclerosis obliterans or peripheral arterial disease (PAD) usually denotes a degenerative arteriopathy affecting the abdominal aorta and mostly the upper and lower limbs [1]. This vascular disease is characterized by occlusive lesions, primarily of atherosclerotic origin, but often accompanied by fibrosis and calcification of the tunica media. A varying degree of thrombosis is frequently associated. In the past, arteriosclerosis obliterans has been considered to be an occlusive arterial disease, exclusively or predominantly affecting the lower limbs.

In this report, the abnormalities of circulatory homeostasis in patients with PAD are studied with particular reference to the modifications in systolic blood pressure (SBP), arterial stiffness, and wave reflections. Consequences with regard to diseased atherosclerotic limbs and the relationship with cardiovascular (CV) morbidity and mortality are also taken into account.

Ankle-Brachial Index

Intermittent claudication, the major symptom of PAD, is absent in the majority of patients. A useful tool for screening patients is known to be ABI, i.e. the ratio of SBP measured at the ankle to SBP at the brachial artery [1-3]. Without an obstruction to blood flow, SBP in the ankle is greater than brachial SBP (ankle-brachial index 61.0). This hemodynamic profile is due to wave reflections (see Chapter 1). It is observed because a great amount of reflected waves from the toes merges with the forward wave at the systolic phase of the pressure waveform (due to the small distance between toes and ankle). As the lumen narrows, SBP beyond the obstruction falls and a pressure gradient can be measured between sequential segments of each extremity. The fall in peripheral (ankle) SBP lowers the ABI (table 1). The ABI is further reduced in subjects with systolic hypertension since brachial SBP is augmented. For the diagnosis of peripheral artery disease of the lower limbs, several threshold values have been proposed, but the majority of authors consider values <0.9 to be abnormal, since this value is 95% sensitive to angiographically proven peripheral artery stenosis. High values of ABI (>1.4-1.5) are also considered to be abnormal. The reason is that they reflect increased rigidity of the arteries of the lower limb, which prevents their compression by the cuff, leading to false results, even in the absence of systolic hypertension [4-6].

ABI <0.9 has been recognized as a strong predictor of subsequent CV mortality and stroke [2]. Recently it has been even demonstrated that both high (>1.4) and low (<0.9) ABI similarly predict CV and total mortality [3].

PAD, Blood Pressure and Systemic Hemodynamics

For many years, the incidence of systolic-diastolic hypertension, assessed from non-invasive indirect determinations of BP, has been reported to be consistently higher in patients with PAD than in age-matched control subjects [1]. This finding may be discussed on the basis of the validity of BP measurements in PAD patients. Since the initial description by Osler [4], it has become well accepted that elderly subjects may have inappropriately elevated cuff pressure when compared with intra-arterial pressure, due to excessive atheromatosis and/or medial hypertrophy of the arterial tree [5, 6]. In the elderly, cuff determinations overestimate DBP whereas SBP remains largely accurate [7]. Such results strongly suggest that the incidence of hypertension in PAD patients should have to be reviewed on the basis of intra-arterial BP measurements.

Table 1. Systemic and regional hemodynamic parameters in resting patients with PAD of the lower limbs by comparison with age- and sex-matched controls [8-10]

Parameters

Control subjects

PAD patients

Systolic arterial pressure, mm Hg

l40±4

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