ProtocolsThere are many protocols for treadmill testing including fixed routines, graded routines and alternative protocols for patients with limited exercise ability [36]. J Cardiovasc Surg (Torino) 1982; 23:125. ), Noninvasive vascular testing may be indicated to screen patients with risk factors for arterial disease, establish a diagnosis in patients with symptoms or signs consistent with arterial disease, identify a vascular injury, or evaluate the vasculature preoperatively, intraoperatively, or for surveillance following a vascular procedure (eg, stent, bypass). J Am Coll Cardiol 2001; 37:1381. A three-cuff technique uses above knee, below knee, and ankle cuffs. The natural history of patients with claudication with toe pressures of 40 mm Hg or less. TRANSCUTANEOUS OXYGEN MEASUREMENTSTranscutaneous oxygen measurement (TcPO2) may provide supplemental information regarding local tissue perfusion and the values have been used to assess the healing potential of lower extremity ulcers or amputation sites. The Ankle Brachial Index (ABI) is a measure of ankle pressure divided by the pressure at the arm. Only tests that confirm the presence of arterial disease,further define the level and extent of vascular pathologyor provide information that will alter the course of treatment should be performed.Vascular testing may be indicated for patients with suspected arterial disease based upon symptoms (eg, intermittent claudication), physical examination findings (eg, signs of tissue ischemia), or in patients who are asymptomatic with risk factors for atherosclerosis (eg, smoking, diabetes mellitus) or other arterial pathology (eg, trauma, peripheral embolism) [1]. Blood pressure cuffs are placed at the mid-portion of the upper arm and the forearm and PVR waveform recordings are taken at both levels. Measure the systolic brachial artery pressure bilaterally in a similar fashion with the blood pressure cuff placed around the upper arm and using the continuous wave Doppler. Mild disease and arterial entrapment syndromes can produce false negative tests. Arterial thrombosis may occur distal to a critical stenosis or may result from embolization, trauma, or thoracic outlet compression. 13.19 ). Am J Med 2005; 118:676. The ABI for each lower extremity is calculated by dividing the higher ankle pressure (dorsalis pedis or posterior tibial artery) in each lower extremity by the higher of the two brachial artery systolic pressures. MR angiography in the evaluation of atherosclerotic peripheral vascular disease. ), Provide surveillance after vascular intervention. The disease occurs when narrowed arteries reduce the blood flow to the arms and legs. A potential, severe complication associated with use of gadolinium in patients with renal failure is nephrogenic systemic sclerosis/nephrogenic fibrosing dermopathy, and therefore gadolinium is contraindicated in these patients. These tools include: Continuous-wave Doppler (with a recording device to display arterial waveforms), Pulse volume recordings (PVRs) and segmental pressures, Photoplethysmographic (PPG) sensors to detect blood flow in the digits. Circulation 1995; 92:614. However, the intensity and quality of the continuous wave Doppler signal can give an indication of the severity of vascular disease proximal to the probe. Platinum oxygen electrodes are placed on the chest wall and legs or feet. N Engl J Med 1964; 270:693. A higher value is needed for healing a foot ulcer in the patient with diabetes. Compared to the arm, lower blood pressure in the leg suggests blocked arteries due to peripheral artery disease (PAD). Pulsed-wave technology uses a row of crystals, each of which alternately send and receive pulse trains of sound waves with a slight time delay with respect to their adjacent crystals. These criteria can also be used for the upper extremity. The upper extremity arterial system requires a different diagnostic approach than that used in the lower extremity. ), The comparison of the resting systolic blood pressure at the ankle to the systolic brachial pressure is referred to as the ankle-brachial (ABI) index. Ann Vasc Surg 2010; 24:985. American Diabetes Association. Exercise testing is generally not needed to diagnose upper extremity arterial disease, though, on occasion, it may play a role in the evaluation of subclavian steal syndrome. In a series of 58 patients with claudication, none of 29 patients in whom conservative management was indicated by MDCT required revascularization at a mean follow-up of 501 days [50]. Met R, Bipat S, Legemate DA, et al. J Vasc Surg 1996; 24:258. Condition to be tested are thoracic outlet syndrome and Raynaud phenomenon. The ratio of the velocity of blood at a suspected stenosis to the velocity obtained in a normal portion of the vessel is calculated. However, because arteriography exposes the patient to radiation and other complications associated with percutaneous arterial access and iodinated contrast, other modalities including computed tomography and magnetic resonance imaging have become important alternative methods for vascular assessment. Measurement and Interpretation of the Ankle-Brachial Index: A Scientific Statement from the American Heart Association. With severe disease, the amplitude of the waveform is blunted (picture 3). A fall in ankle systolic pressure by more than 20 percent from its baseline value, or below an absolute pressure of 60 mmHg that requires >3 minutes to recover is considered abnormal. Ix JH, Katz R, Peralta CA, et al. Vascular testing may be indicated for patients with suspected arterial disease based upon symptoms (eg, intermittent claudication), physical examination findings (eg, signs of tissue ischemia), or in patients with risk factors for atherosclerosis (eg, smoking, diabetes mellitus) or other arterial pathology (eg, trauma, peripheral embolism) [1]. The frequency of ultrasound waves is 20000 The principal effect is blood flow reduction because of stenosis or occlusion that can result in arm ischemia. endstream endobj startxref Only tests that confirm the presence of arterial disease, further define the level and extent of vascular pathology. Six studies evaluated diagnostic performance according to anatomic region of the arterial system. With a four cuff technique, the high-thigh pressure should be higher than the brachial pressure, though in the normal individual, these pressures would be nearly equal if measured by invasive means. 13.13 ). Duplex imagingDuplex scanning can be used to evaluate the vasculature preoperatively, intraoperatively, and postoperatively for stent or graft surveillance and is very useful in identifying proximal arterial disease. Your doctor uses the blood pressure results to come up with a number called an ankle-brachial index. 13.8 to 13.12 ). The ankle brachial index (ABI) is the ratio between the blood pressure in the ankles and the blood pressure in the arms. The signal is proportional to the quantity of red blood cells in the cutaneous circulation. Ann Vasc Surg 1994; 8:99. These tests generally correlate to clinical symptoms and are used to stratify the need for further evaluation and treatment. A low ABI is associated with a higher risk of coronary heart disease, stroke, transient ischemic attack, progressive renal insufficiency, and all-cause mortality [20-25]. With arterial occlusion, proximal Doppler waveforms show a high-resistance pattern often with decreased PSVs (see Fig. A >30 mmHg decrement between the highest systolic brachial pressure and high-thigh pressure is considered abnormal. Normal is about 1.1 and less . The ankle-brachial index (ABI) is a noninvasive, simple, reproducible, and cost-effective diagnostic test that compares blood pressures in the upper and lower limbs to determine the presence of resistance to blood flow in the lower extremities, typically caused by narrowing of the arterial lumen resulting from atherosclerosis. If the ABI is greater than 0.9 but there is suspicion of PAD, postexercise ABI measurement or other noninvasive options . Velocities in normal radial and ulnar arteries range between 40 and 90cm/s, whereas velocities within the palmar arches and digits are lower. Here's what the numbers mean: 0.9 or less. Once you know you have PAD, you can repeat the test to see how you're doing after treatment. Imaging of hand arteries requires very high frequency transducers because these vessels are extremely small and superficial. The wrist pressure do sided by the highest brachial pressure. To differentiate from pseudoclaudication (atypical symptoms). (See "Exercise physiology".). ), For patients with a normal ankle- or wrist-brachial index and distal extremity ischemia, individual digit waveforms and digit pressures can be used to identify small vessel occlusive arterial disease. Apelqvist J, Castenfors J, Larsson J, et al. Resnick HE, Lindsay RS, McDermott MM, et al. (B) Duplex ultrasound imaging begins with short-axis views of the subclavian artery obtained, Long-axis subclavian examination. The pressure drop caused by the obstruction causes the subclavian artery to be supplied by the ipsilateral vertebral artery. Circulation. Assessment of exercise performance, functional status, and clinical end points. Multisegmental plethesmography pressure waveform analysis with bi-directional flow of the bilateral lower extremities with ankle brachial indices was performed. Upper extremity disease is far less common than lower extremity disease and abnormalities in WBI have not been correlated with adverse cardiovascular risk as seen with ABI. CT and MR imaging are important alternative methods for vascular assessment; however, the cost and the time necessary for these studies limit their use for routine testing [2]. The lower the number, the more . Diabetes Care 2008; 31 Suppl 1:S12. Adriaensen ME, Kock MC, Stijnen T, et al. The ratio of the recorded toe systolic pressure to the higher of the two brachial pressures gives the TBI. Repeat ABIs demonstrate a recovery to the resting, baseline ABI value over time. Color Doppler and duplex ultrasound are used in conjunction with or following noninvasive physiologic testing. Exercise augments the pressure gradient across a stenotic lesion. In the patient with possible upper extremity occlusive disease, a difference of 10 mmHg between the left and right brachial systolic pressures suggests innominate, subclavian, axillary, or proximal brachial arterial occlusion. Standards of medical care in diabetes--2008. A meta-analysis of 20 studies in which MDCT was used to evaluate 19,092 lower extremity arterial segments in 957 symptomatic patients compared test performance with DSA [49]. (See "Management of the severely injured extremity"and "Blunt cerebrovascular injury: Mechanisms, screening, and diagnostic evaluation". In this video, taken from our Ultrasound Masterclass: Arteries of the Legs course, you will understand both the audible and analog waveforms of Dopplers, and. 13.1 ). If a patient has a significant difference in arm blood pressures (20mm Hg, as observed during the segmental pressure/PVR portion of the study), the duplex imaging examination should be expanded to check for vertebral to subclavian steal. ABI >1.30 suggests the presence of calcified vessels. (A and B) The principal arterial supply to digits three, four, and five is via the common digital arteries (, Proper digital artery examination. An index under 0.90 means that blood is having a hard time getting to the legs and feet: 0.41 to 0.90 indicates mild to moderate peripheral artery disease; 0.40 and lower indicates severe disease. [ 1, 2, 3] The . Eur J Radiol 2004; 50:303. In the upper limbs, the wrist-brachial index can be used, with the same cutoff described for the ABPI. Higher frequency sound waves provide better lateral resolution compared with lower frequency waves. 2. Intermittent claudication: an objective office-based assessment. ), Physiologic tests include segmental limb pressure measurements and the determination of pressure index values (eg, ankle-brachial index, wrist-brachial index, toe-brachial index), exercise testing, segmental volume plethysmography, and transcutaneous oxygen measurements. An ABI of 0.9 or less is the threshold for confirming lower-extremity PAD. It then goes on to form the deep palmar arch with the ulnar artery. A variety of noninvasive examinations are available to assess the presence, extent, and severity of arterial disease and help to inform decisions about revascularization. Olin JW, Kaufman JA, Bluemke DA, et al. the right brachial pressure is 118 mmHg. Furthermore, the vascular anatomy of the hand described herein is a simplified version of the actual anatomy because detailing all of the arterial variants of the hand is beyond the scope of this chapter. 0.90 b. SCOPE: Applies to all ultrasound upper extremity arterial evaluations with pressures performed in Imaging Services / Radiology . Exercise testingSegmental blood pressure testing, toe-brachial index measurements and PVR waveforms can be obtained before and after exercise to unmask occlusive disease not apparent on resting studies. (A and B) Long- and short-axis color and power Doppler views show occlusion of an axillary artery (, Doppler waveforms proximal to radial artery occlusion. The site of pain and site of arterial disease correlates with pressure reductions seen on segmental pressures [3,33]: As with ABI measurements, segmental pressure measurements in the lower extremity may be artifactually increased or not interpretable in patients with non-compressible vessels [3]. Ultrasonography is used to evaluate the location and extent of vascular disease, arterial hemodynamics, and lesion morphology [10]. The standard examination extends from the neck to the wrist. Different velocity waveforms are obtained depending upon whether the probe is proximal or distal to a stenosis. Exercise testing is most commonly performed to evaluate lower extremity peripheral artery disease (PAD). (A) As it reaches the wrist, the radial artery splits into two. 0.97 a waveform pattern that is described as triphasic would have: Pressure measurements are obtained for the radial and ulnar arteries at the wrist and brachial arteries in each extremity. Byrne P, Provan JL, Ameli FM, Jones DP. Diagnosis and management of occlusive peripheral arterial disease. A meta-analysis of 14 studies found that sensitivity and specificity of this technique for 50 percent stenosis or occlusion were 86 and 97 percent for aortoiliac disease and 80 and 98 percent for femoropopliteal disease [42]. ), An ABI 0.9 is diagnostic of occlusive arterial disease in patients with symptoms of claudication or other signs of ischemia and has 95 percent sensitivity (and 100 percent specificity) for detecting arteriogram-positive occlusive lesions associated with 50 percent stenosis in one or more major vessels [, An ABI of 0.4 to 0.9 suggests a degree of arterial obstruction often associated with claudication [, An ABI below 0.4 represents multilevel disease (any combination of iliac, femoral or tibial vessel disease) and may be associated with non-healing ulcerations, ischemic rest pain or pedal gangrene. Sign in|Recent Site Activity|Report Abuse|Print Page|Powered By Google Sites. For almost every situation where arterial disease is suspected in the upper extremity, the standard noninvasive starting point is the PVR combined with segmental pressure measurements ( Fig. (A) The distal brachial artery can be followed to just below the elbow. 332 0 obj <>stream This is an indication that blood is traveling through your blood vessels efficiently. Screen patients who have risk factors for PAD. Ankle and Toe Brachial Index Interpretation ABI (Ankle brachial index)= Ankle pressure/ Brachial pressure. What does a wrist-brachial index between 0.95 and 1.0 suggest? Normally, the pressure is higher in the ankle than in the arm. Pressure assessment can be done on all digits or on selected digits with more pronounced problems. The subclavian artery continues to the lateral edge of the first rib where it becomes the axillary artery. In the upper extremities, the extent of the examination is determined by the clinical indication. INTRODUCTIONThe evaluation of the patient with arterial disease begins with a thorough history and physical examination and uses noninvasive vascular studies as an adjunct to confirm a clinical diagnosis and further define the level and extent of vascular pathology. A pressure gradient of 20 to 30 mmHg normally exists between the ankle and the toe, and thus, a normal toe-brachial index is 0.7 to 0.8. Circulation 2004; 109:733. Thrombus or vasculitis can be visualized directly with gray-scale imaging, but color and power Doppler imaging are used to determine vessel patency and to assess the degree of vessel recanalization following thrombolysis. Finally, if nonimaging Doppler and PPG waveforms suggest arterial obstructive disease, duplex imaging can be done to identify the cause. Menke J, Larsen J. Meta-analysis: Accuracy of contrast-enhanced magnetic resonance angiography for assessing steno-occlusions in peripheral arterial disease. Normal ABI's (or decreased ABI/s recommend clinical correlation for arterial occlusive disease). (See "Clinical features, diagnosis, and natural history of lower extremity peripheral artery disease"and "Overview of thoracic outlet syndromes"and "Clinical manifestations and diagnosis of the Raynaud phenomenon"and "Clinical evaluation of abdominal aortic aneurysm".). A 20 mmHg or greater reduction in pressure is indicative of a flow-limiting lesion if the pressure difference is present either between segments along the same leg or when compared with the same level in the opposite leg (ie, right thigh/left thigh, right calf/left calf) (figure 1). ). ), For symptomatic patients with an ABI 0.9 who are possible candidates for intervention, we perform additional noninvasive vascular studies to further define the level and extent of disease. yr if P!U !a A high ankle brachial index is associated with greater left ventricular mass MESA (Multi-Ethnic Study of Atherosclerosis). Other goals, depending upon the clinical scenario, are to localize the level of obstructive lesions and assess the adequacy of tissue perfusion and wound healing potential. Effect of MDCT angiographic findings on the management of intermittent claudication. Ultrasound is the mainstay for vascular imaging with each mode (eg, B-mode, duplex) providing specific information that is useful depending upon the vascular disorder. Surg Forum 1972; 23:238. The steps for recording the right brachial systolic pressure include, 1) apply the blood pressure cuff to the right arm with the patient in the supine position, 2) hold the Doppler pen at a 45 angle to the brachial artery, 3) pump up the blood pressure cuff to 20 mmHg above when you hear the last arterial beat, 4) slowly release the pressure An ankle brachial index test, also known as an ABI test, is a quick and easy way to get a read on the blood flow to your extremities. (A) Note the low blood flow velocities with a peak systolic velocity of 12cm/s and high-resistance pattern. Although stenosis of the proximal upper extremity arteries is most often caused by atherosclerosis, other pathologies include vasculitis, trauma, or thoracic outlet compression. The ulnar artery feeding the palmar arch. Multidetector row CT angiography of the abdominal aorta and lower extremities in patients with peripheral arterial occlusive disease: diagnostic accuracy and interobserver agreement. However, the introduction of arterial evaluations for dialysis fistula placement and evaluation, radial artery catheterization, and radial artery harvesting for coronary artery bypass surgery or skin flap placement have increased demand for these tests. (A) This continuous-wave Doppler waveform was obtained from the radial artery with the hand very warm and relaxed. Clinically significant atherosclerotic plaque preferentially develops in the proximal subclavian arteries and occasionally in the axillary arteries. Assuming the contralateral limb is normal, the wrist-brachial index can be another useful test to provide objective evidence of arterial compromise. ), In a prospective study among nearly 1500 women, 5.5 percent had an ABI of <0.9, 67/82 of whom had no symptoms consistent with peripheral artery disease. interpretation of US images is often variable or inconclusive. Arterial occlusion distal to the ankle or wrist can be detected using digit plethysmography, which is performed by placing small pneumatic cuffs on each of the digits of the hands or feet depending upon the disease being investigated. A common fixed protocol involves walking on the treadmill at 2 mph at a 12 percent incline for five minutes or until the patient is forced to stop due to pain (not due to SOB or angina). (See 'Ankle-brachial index'above and 'Physiologic testing'above and 'Ultrasound'above and 'Other imaging'above. For example, velocities in the iliac artery vary between 100 and 200 cm/s and peak systolic velocities in the tibial artery are 40 and 70 cm/s. Introduction to Measuring the Ankle Brachial Index Spittell JA Jr. Radiology 2000; 214:325. Noninvasive physiologic vascular studies allow evaluation of the physiologic parameters of blood flow through segmental arterial pressures, Doppler waveforms, and pulse volume recordings to determine the site and severity of lower extremity peripheral arterial disease. 13.3 and 13.4 ), axillary ( Fig. MEASUREMENT OF WRIST: BRACHIAL INDICES AND ARTERIAL WAVEFORM ANALYSIS, measurement of radial and ulnar (or finger) and brachial arterial pressures bilaterally using Doppler or plethysmographic techniques, the calculation of the wrist (or finger ) brachial systolic pressure indices and assessment of arterial waveforms for the evaluation of upper 13.18 ). Br J Surg 1996; 83:404. At the wrist, the radial artery anatomy gets a bit tricky. 13.14 ). Selective use of segmental Doppler pressures and color duplex imaging in the localization of arterial occlusive disease of the lower extremity. 1. (A) Following the identification of the subclavian artery on transverse plane (see. TBI is a common vascular physiologic assessment test taken to determine the existence and severity of peripheral arterial disease (PAD) in the lower extremities. %PDF-1.6 % Ankle brachial index (ABI) is a means of detecting and quantifying peripheral arterial disease (PAD). Select the . ABI >1.30 suggests the presence of calcified vessels, For patients with a normal ankle-brachial index (ABI) who have typical symptoms of claudication, we suggest exercise testing. Prior to the performance of the vascular study, there are certain questions that the examiner should ask the patient and specific physical observations that might help conduct the examination and arrive at a diagnosis. The Toe Brachial Index (TBI) is defined as the ratio between the systolic blood pressure in the right or left toe and the higher of the systolic pressure in the right or left arms. This chapter provides the basics of upper extremity arterial assessment including: The appropriate ultrasound imaging technique, An overview of the pathologies that might be encountered. O'Hare AM, Katz R, Shlipak MG, et al. Vascular Clinical Trialists. The smaller superficial branch continues into the volar (palmar side) aspect of the hand (, Examining branches of the deep palmar arch. The analogous index in the upper extremity is the wrist-brachial index (WBI). Specificity was lower in the tibial arteries compared with the aortoiliac and femoropopliteal segment, but the difference was not significant. Wrist brachial index: Normal around 1.0 Normal finger to brachial index: 0.8 Digital Pressure and PPG Digital pressure 30 mmHg less than brachial pressure is considered abnormal. The following transition points define the major arteries supplying the arm: (1) from subclavian to axillary artery at the lateral aspect of the first rib; (2) axillary to brachial artery at the lower aspect of the teres major muscle; (3) trifurcation of the brachial artery to ulnar, radial, and interosseous arteries just below the elbow. Other studies frequently used to image the vasculature include computed tomography (CT) and magnetic resonance (MR) imaging. Specialized imaging of the hand can be performed to detect disease of the digital arteries. Proximal to a high-grade stenosis with minimal compensatory collateralization, a thumping sound is heard. OTHER IMAGINGContrast arteriography remains the gold standard for vascular imaging and, under some circumstances (eg, acute ischemia), is the primary imaging modality because it offers the benefit of potential simultaneous intervention. J Vasc Surg 2009; 50:322. ), The normal ABI is 0.9 to as high as 1.3. Patients with asymptomatic lower extremity PAD have an increased risk of myocardial infarction, stroke, and cardiovascular mortality and benefit from identification to provide risk factor modification [, Confirm a diagnosis of arterial disease in patients with symptoms or signs consistent with an arterial pathology. Leng GC, Fowkes FG, Lee AJ, et al. In one prospective study, the four-cuff technique correctly identified the level of the occlusive lesion in 78 percent of extremities [32]. Physiologic tests include segmental limb pressures and the calculation of pressure index values (eg, ankle-brachial index, toe-brachial index, wrist-brachial index), exercise . The formula used in the ABI calculator is very simple. It goes as follows: Right ABI = highest right ankle systolic pressure / highest brachial systolic pressure. A venous signal can be confused with an arterial signal (especially if pulsatile venous flow is present, as can occur with heart failure) [11,12]. The ankle-brachial pressure index(ABPI) or ankle-brachial index(ABI) is the ratio of the blood pressureat the ankleto the blood pressure in the upper arm(brachium). For instance, if fingers are cool and discolored with exposure to cold but fine otherwise, the examination will focus on the question of whether this is a vasospastic disorder (e.g., Raynaud disease) versus a situation where arterial obstructive disease is present. The blood pressure is measured at the ankle and the arm (brachial artery) and the ratio calculated. Health care providers calculate ABI by dividing the blood pressure in an artery of the ankle by the blood pressure in an artery of the arm. Progressive obstruction proximal to the Doppler probe results in a decrease in systolic peak, elimination of the reversed flow component and an increase in the flow seen in late diastole. Facial Esthetics. Volume changes in the limb segment beneath the cuff are reflected as changes in pressure within the cuff, which is detected by a pressure transducer and converted to an electrical signal to produce an analog pressure pulse contour known as a pulse volume recording (PVR). Two ultrasound modes are routinely used in vascular imaging: the B (brightness) mode and the Doppler mode (B mode imaging + Doppler flow detection = duplex ultrasound). Anatomy Face. Wrist-brachial index The wrist-brachial index (WBI) is used to identify the level and extent of upper extremity arterial occlusive disease. Vogt MT, Cauley JA, Newman AB, et al. (A) Upper arm and forearm (segmental) blood pressures are shown in the boxes on the illustration. Exercise testing is a sensitive method for evaluating patients with symptoms suggestive of arterial obstruction when the resting extremity systolic pressures are normal. Semin Ultrasound CT MR 1990; 11:168. TBPI Equipment A continuous wave hand held Doppler unit is used to detect the brachial and distal posterior tibial and dorsalis pedis pulses and the blood pressure is measured using blood pressure cuffs and a conventional sphygmomanometer. Calf pain Pressure gradient from the high to lower thigh indicates superficial femoral artery disease. This is the systolic blood pressure of the ankle. The axillary artery courses underneath the pectoralis minor muscle, crosses the teres major muscle, and then becomes the brachial artery. According to the ABI calculator, a normal test result falls in the 0.90 to 1.30 range, meaning the blood pressure in your legs should be equal to or greater . Hiatt WR. Velocity ratios >4.0 indicate a >75 percent stenosis in peripheral arteries (table 1). Norgren L, Hiatt WR, Dormandy JA, et al. Physicians and sonographers may sometimes feel out of their comfort zone when it comes to evaluating the arm arteries because of the overall low prevalence of native upper extremity arterial disease and the infrequent requests for these examinations. Authors Basics topics (see "Patient information: Peripheral artery disease and claudication (The Basics)"), Beyond the Basics topics (see "Patient information: Peripheral artery disease and claudication"), Noninvasive vascular testing is an extension of the vascular history and physical examination and is used to confirm a diagnosis of arterial disease and determine the level and extent of disease. The distal radial artery, princeps pollicis artery, deep palmar arch, superficial palmar arch, and digital arteries are selectively imaged on the basis of the clinical indication ( Figs. A threshold of less than 0.9 is an indication for invasive studies or operative exploration in equivocal cases. The effects of exercise on the cardiovascular system are discussed elsewhere. This index provides a measure of the severity of disease [10]. The WBI for each upper extremity is calculated by dividing the highest wrist pressure (radial artery or ulnar artery) by the higher of the two brachial artery pressures.