Given the relatively common prevalence of peripheral vascualr disease and its potential complications in the lower extremity, these authors offer key diagnostic insights with a particular emphasis on non-invasive screening tools. Lower extremity vascular disease is a routine complication with lower extremity wounds, especially in the diabetic population. Peripheral neuropathy and peripheral vascular disease are recognized as contributing factors in lower extremity amputation. It is estimated that more than 5 million people per year experience peripheral vascular disease.1 In 2002, about 82,000 non-traumatic lower limb amputations were performed in people with diabetes.2 Researchers have shown that basic vascular screening is efficacious in the identification of lower limb peripheral arterial occlusive disease, and that clinicians can incorporate this screening in the initial evaluation of the at-risk patient.3 Therefore, a complete evaluation of a patient with lower extremity ulcerations always requires the practitioner to perform a thorough vascular examination.4
What To Look For In The Patient History And Clinical Exam
When assessing patients whom you suspect of having peripheral vascular disease, there are several considerations to be aware of when reviewing the patient history. One should note any concomitant medical problems that contribute to a patient’s risk of atherosclerotic disease. Common comorbid conditions include diabetes, hypercholesterolemia, coronary artery disease and cerebrovascular disease among others. In regard to asymptomatic patients with multiple atherosclerotic risk factors, clinicians should routinely screen for involvement of the peripheral vasculature. Ten percent of individuals between the ages of 55 to 74 have asymptomatic lower extremity arterial disease when they are screened.5 Furthermore, atherosclerotic occlusive disease is but one manifestation of a generalized process with affected individuals often presenting with concomitant lesions in a variety of vascular beds such as the coronary, carotid or renal vasculature.6-8 Clinicians can assess arterial insufficiency based upon a patient’s presenting symptoms. The pain associated with this condition is directly related to the lack of arterial flow to the lower extremity musculature. Symptoms can be acute, chronic or both. Patients with acute arterial occlusion from an embolic or thrombotic event may present with an acute onset of increasing pain in the affected limb in the presence of a cool extremity and variable numbness. In the event of an acute event in a patient with known risk factors, these symptoms may be the first signal that arterial insufficiency exists. These acute symptoms can also present in the presence of more chronic complaints in patients with longstanding peripheral vascular disease. The patient may complain of pain in the buttocks or calves that is brought on with activity and relieved with rest (intermittent claudication). Patients may experience burning pain in the forefoot that is aggravated by elevation and relieved by dependency (rest pain), or clinicians may note the development of ulceration on the legs, feet or between the toes. Multilevel atherosclerotic disease is usually required to produce significant symptomatology. The classical symptoms of claudication or rest pain may be obscured by neuropathy in the patient who has diabetes, and the visual identification of ulcers may be delayed because of associated visual loss from diabetic retinopathy. Elderly patients with significant cardiac or pulmonary disease may not be sufficiently ambulatory to trigger complaints of claudication even though significant disease may be present. Additionally, clinicians should thoroughly question patients about their renal function as this will have an impact on choices for advanced vascular imaging modalities due to the potential for a patient to receive an iodinated dye load. One should also note any allergies to iodinated contrast and shellfish, which can impact the ability to safely perform angiography.
Essential Keys To The Vascular Examination
All basic vascular assessments begin with the grading of pedal pulses, Doppler examination in the event of a non-palpable pulse and, if necessary, ankle-brachial index (ABI) exams. However, these steps do not constitute a complete and thorough exam. Further exam is necessary to get a true assessment of the extent of potential vascular compromise present. The signs and symptoms of arterial insufficiency will vary depending upon the severity of the problem. A visual inspection should note the presence or absence of tissue loss (or ulceration), the color of the foot and whether there is any evidence of soft tissue atrophy. The color of the foot is of particular importance. The color of the skin is conferred by blood in the subpapillary layer and will vary with the position of the extremity, skin temperature and the degree of blood oxygenation (reduced hemoglobin blue). In chronic arterial insufficiency, the arterioles will maximally dilate as a compensatory response to the chronic ischemia intensifying color changes. During acute arterial occlusion, the venules will empty, leading to a chalky white appearance regardless of extremity position. Partial but inadequate perfusion from an incomplete acute or chronic occlusion allows for pooling of blood in the venules, which may be red in cold temperatures or blue at higher temperatures. When the extremity is at the level of the heart, the pooled blood masks the arterial flow. Elevation of the extremity above the level of the central venous pressure (rarely greater than 25 cm) allows the pooled venous blood to drain and facilitates an accurate assessment of the degree of arterial flow. The normal extremity will remain pink whereas the extremity with arterial insufficiency will become pallid. Conversely, allowing the extremity to become dependent will cause an intense rubor or cyanosis (dependent rubor). The time of return of blood to the dependent extremity is a useful marker of the severity of the deficit (normally less than 20 seconds).4 Reduced arterial flow results in a diminished nutritional supply to the skin, leading to thinning and functional loss of the dermal appendages. One will note dry, shiny and hairless skin. The nails may become brittle and ridged. Comparing color and trophic changes between extremities gives a good indication of the severity of the process unless a bilateral deficit is present. In cases of bilateral deficit, the experience of the examiner will be required to make an accurate diagnosis. It is important to differentiate the rubor associated with vascular insufficiency and cellulitis accompanying an active infective process. Cellulitic color changes will persist despite extremity elevation while dependent rubor will reduce with elevation of the affected extremity. Skin temperature is a reliable indicator of the blood flow rate in the dermal vessels although flow is governed primarily by constriction or dilation of the arterioles to maintain a constant core temperature. Nevertheless, the temperature of the skin as a marker of perfusion is useful. One can assess this by lightly palpating the skin with the back of the hand and comparing similar sites from one extremity to the other. An ischemic limb is cool and demarcation of temperature gives a rough indication of the level of the occlusion. Again, assessment of temperature differences is confounded when both extremities are affected. Extremity ulcerations have a characteristic appearance depending upon their etiology.9-10 When it comes to ulcerations caused by ischemia, clinicians will typically locate them at the most distal end of the arterial system. They are most commonly present on the tips of the toes and between the digits. The lesions appear punched out and painful, but exhibit little bleeding. Neuropathic ulcerations typically occur at the heel or over the metatarsal heads on the plantar surface (mal perforans ulcer) but may also occur in less characteristic locations secondary to trauma or pressure. The sensory neuropathy present in the diabetic population may allow significant progression of these processes with penetration to bone and the deep plantar space without symptomatology. In addition to ulcers, patients may present with a varying degrees of tissue loss in the forefoot or hindfoot or frankly gangrenous digits. The presence of dry gangrene is a stable process allowing for a complete vascular evaluation. However, any progression to an infected wet gangrene requires immediate surgical debridement.
Understanding The Impact Of Non-Invasive Vascular Screening Tools
Abnormalities on initial exam obligate the practitioner to proceed with more advanced modalities to assess vascular inflow into the lower extremity. Noninvasive vascular laboratory evaluations play an important role in the care of patients with evidence of vascular disease and allow for a clear picture of whether advanced imaging modalities such as angiography will be necessary. Current noninvasive vascular tests include physiologic and anatomic testing modalities. Segmental limb pressures, Doppler and plethysmographic waveform analysis, transcutaneous oximetry, and skin perfusion pressure all provide important functional information on the adequacy of perfusion. Color duplex imaging provides more specific anatomic and physiologic information.4
What You Should Know About Limb Pressure Measurements
Segmental limb pressures are an extension of the bedside ABI. This noninvasive test is indicated in any patient for whom history and physical examination suggests peripheral vascular disease. By obtaining pressures at successive levels of the extremity, the level of disease can be localized in most cases. After the patient has been at rest in a supine position for 15 minutes, one would place four standard-sized blood pressure cuffs at the high thigh, above-knee, below-knee and ankle positions. Clinicians may obtain the dorsalis pedis or posterior tibial arterial Doppler signal with a continuous wave Doppler at the ankle. One measures the pressure at each cuff level that occludes the pedal signal by first inflating the cuff until you no longer hear the signal and then progressively deflating the cuff until the signal resumes. Dividing the pressure at each level by the highest systolic arm pressure gives the clinician an index for each level. The proximal thigh pressure is usually recorded 30 to 40 mmHg higher than the brachial pressure. These pressures should be nearly equal in normal individuals but artifact occurs because the thigh cuff width is often not appropriately 120 percent of the diameter of the limb at the thigh level to provide an accurate pressure reading. A high thigh index of less than 1.2 is considered abnormal and may reflect aortoiliac disease of concomitant profunda and superficial femoral obstruction, depending on the placement of the cuff relative to these structures. However, a normal high-thigh brachial index rules out aortoiliac disease. Note the differences in index level between the cuff levels as well as between each extremity at the same level. A 20 mmHg pressure gradient between successive levels on the same extremity is considered a significant pressure drop and correlates with flow limiting vascular lesions. Successive significant decrements indicate multilevel disease. Comparing the unaffected limb with the affected limb is a good indicator of the severity of the process. The systolic pressures measured at the same level in both legs normally should not differ by more than 20 mmHg. Pressure gradients may be increased in the hypertensive patient and decreased in low cardiac output states. Adequate collateralization may also diminish the observed pressure gradient, obscuring a significant lesion. Segmental pressure measurements are useful in the serial evaluation of patients over time and are reliable as an assessment of changes relative to risk factor intervention, exercise programs or revascularization. Any change in index greater than 0.15 at the same cuff level from one study to the next is considered significant.
Understanding The Value Of Obtaining Toe Pressures
Diabetics with medial sclerosis and patients with chronic renal insufficiency often have non-occlusive pressures with ABIs greater than 1.3. Accordingly, segmental pressures have limited usefulness in the evaluation of peripheral vascular disease in these populations. Toe digital arteries are less likely to be calcified so toe occlusive pressure measurements more reliably reflect pressure within the digital artery. Therefore, the toe brachial index (TBI) is a more reliable indicator of foot perfusion in patients with diabetes.5 In order to obtain a photoplethysmographic (PPG) arterial waveform, the clinician would place a pneumatic cuff on the digit and place a photoelectrode on the end of the digit. An infrared light is transmitted into the superficial layers of the skin and the reflected portion is received by a phototransistor within the plethysmographic sensor. The resulting signal is proportional to the quantity of red blood cells in the cutaneous circulation. The toe cuff is analogous to the segmental cuff pressures as one would inflate the toe cuff until the waveform flattens and then progressively deflate it. The clinician would record the systolic pressure at the point in which the normal waveform is reestablished. The ratio of the recorded systolic pressure to the higher of the two brachial pressures gives the toe-brachial index. The absolute toe pressures are of value in estimating the potential healing of the ulcer as a pressure greater than 30 mmHg is favorable for ulcer healing.11-14 Though toe pressures are useful to define perfusion at the level of the foot in those with incompressible vessels, one cannot obtain an indication with toe pressures as to the level of disease.
What Pulse Volume Recordings May Reveal
In order to help establish the disease level in these individuals, one adjunctive method is obtaining waveform analysis with pulse volume recordings (PVR) or Doppler waveform. The PVR is the most commonly used waveform analysis and is less operator dependent than Doppler waveform analysis.15 One would obtain PVRs through the application of sequential blood pressure cuffs with an air plethysmographic technique. After inflating each cuff (10 to 65 mmHg), one can indirectly assess variations in blood volume in the tissue beneath the cuff. Alterations in pressure are transmitted through the inflated cuff to a pressure transducer that records the variations through the cardiac cycle to produce a waveform. Conversion of this pressure signal to an appropriately calibrated electrical signal permits production of an analog tracing that clinicians can examine and interpret. The normal PVR waveform has a sharp upstroke and peak with a reflected wave present before it returns to baseline. With mild obstruction, the reflected wave is lost, the upstroke delayed and the peak blunted. Moderate to severe obstruction produces a bowing of the downstroke away from the baseline. A flat PVR is irregular with low amplitude and indicates severe obstruction.
Can Exercise Testing Be Beneficial?
Performing segmental blood pressure testing, toe brachial index measurements and waveform analysis before and after a patient exercises can unmask occlusive disease that is not apparent on resting studies. With exercise, blood flow normally increases three to fivefold to meet the increased demand and resistance in the muscular bed falls. The presence of a significant stenosis limits this compensatory response and magnifies the pressure gradient across the lesion. The standard test involves walking on the treadmill at 2 mph at a 12 percent incline for five minutes or until the patient is forced to stop. After one records the walking time and nature of symptoms, the clinician can assess the magnitude of the decrease in ankle systolic pressure and time for recovery to resting pressure. A normal response to exercise is a slight increase or no change in the ankle systolic pressure in comparison to the baseline, and rules out vascular insufficiency as the cause of symptoms. A fall in ankle pressure by more than 20 percent of the baseline or below an absolute pressure of 60 mmHg that requires more than three minutes to recover is considered abnormal. Single level disease is inferred with a recovery time of less than six minutes. A greater than six minute recovery time is associated with multilevel disease. One may perform similar testing by utilizing pharmacologic agents such as priscoline. Another option is inducing reactive hyperemia in place of exercise testing in patients with limited exercise ability due to cardiopulmonary disease of musculoskeletal problems.
A Pertinent Guide To Transcutaneous Oximetry
Transcutaneous oxygen (TcPO2) tension may provide supplemental information regarding local tissue perfusion and clinicians often use this test to assess the healing potential of lower extremity ulcers or amputation sites.16 Previous studies showed that TcPO2 measurements can accurately predict the severity of foot ischemia and one can use these measurements to help determine appropriate treatment (conservative versus operative) for patients with diabetes.17 For this test, the physician would place platinum oxygen electrodes on the chest wall and legs or feet. One may evaluate either the absolute value of the oxygen tension at the foot or leg, or a ratio of this value to that of the chest wall. A normal value at the foot is 60 mmHg and a normal chest/foot ratio is 0.9. Controversy exists regarding the optimal level for tissue healing. It is generally accepted that wounds are likely to heal if oxygen tension is greater than 40 mmHg (foot/chest ratio greater than 0.5) and that healing is not likely to occur with a value less than 20 mmHg.18 One may also obtain TcPO2 in conjunction with exercise testing. Normally the value will not diminish. However, in the patient with arterial occlusive disease, the value will fall. A higher value must be achieved for healing of an ulcer in the diabetic foot. Keep in mind that the accuracy of the TcPO2 value is limited by local edema, skin temperature, the patient’s emotional state (sympathetic vasoconstriction) and pharmacologic agents. The routine evaluation of waveforms in conjunction with segmental pressures and segmental indices increase the accuracy of Doppler testing. Duplex ultrasound scanning has been well established as a screening test in vascular patients. However, in terms of duplex arterial mapping in lower extremities, there remains considerable debate regarding its accuracy. Color duplex imaging appears effective for the assessment of occlusive disease of the lower extremities, especially above the knee, but may be less reliable in the infrapopliteal segments. Color duplex imaging incorporates real-time B (brightness) mode imaging and pulsed and color Doppler. Real time B-mode imaging allows for vessel identification and anatomic detail of the vessel. Color Doppler imaging provides for the direction of flow (red toward the transducer and blue away from the transducer) and the presence of turbulence. In addition, one can calculate the degree of diameter reduction or stenosis by peak systolic velocity and velocity ratios. The normal arterial waveform is triphasic with a sharp upstroke, a sharp peak during systole, a sharp downstroke, a reversed flow component and forward diastolic flow. Progressive obstructive lesions cause a loss of reversed flow or of the forward diastolic flow, resulting in a biphasic signal. Decreased peripheral vascular resistance is responsible for the loss of the diastolic flow component and may be normal in older patients or reflect compensatory vasodilation in response to obstructive vascular lesions. The monophasic signal is characterized by a delayed upstroke, blunted peak and no second component. Severe obstruction leads to a flat waveform.
Ensuring a thorough vascular examination is of utmost importance for practitioners who perform limb salvage. Researchers have shown that foot pulses, the toe brachial index and qualitative waveform analyses are highly sensitive screening methods in individuals with and without diabetes.3 Thorough and appropriate vascular evaluations allow for early detection of disease and enable early intervention. Early aggressive intervention, including debridement and revascularization, can result in a cumulative limb salvage rate of 74 percent in high risk groups.19,20 Comprehensive foot care programs can reduce amputation rates by 45 to 85 percent.2 The importance of this testing cannot be understated, and provides a foundation that aids in critical decision making for a multidisciplinary limb salvage team. Dr. Halloran is a Chief Resident in Podiatric Surgery at the Yale-New Haven Hospital in New Haven, Ct. Dr. Blume is an Assistant Clinical Professor within the Section of Podiatry in the Department of Orthopedics and Rehabilitation at the Yale University School of Medicine. He is the Director of Limb Preservation at the Yale-New Haven Hospital in New Haven, Ct. Dr. Palladino is the Director of Research at the North American Center for Limb Preservation in New Haven, Ct. Dr. Sumpio is the Chief of the Section of Vascular Surgery in the Department of Surgery at the Yale University School of Medicine in New Haven, Ct. References 1. Selvin E, Erlinger TP. Prevalence of and risk factors for peripheral arterial disease in the United States: results from the National Health and Nutrition Examination Survey.1999-2000. Circulation 2004; 110:738-743. 2. American Diabetes Association. Diabetes Statistics. Available at www.diabetes.org/diabetes-statistics.jsp. 3. Williams DT, Harding KG, Price P. An evaluation of the efficacy of methods used in screening for the lower-limb arterial disease in diabetes. Diabetes Care 2005; 28(9):2206-2210. 4. Sumpio BE, Lee T, Blume PA. Vascular evaluation and arterial reconstruction of the diabetic foot. Clin Podiatr Med Surg 20 (2003) 689-708 5. Collins KA, Sumpio BE. Vascular assessment. Clin Podiatr Med Surg 2000;17(2):171–91. 6. Abir F, KakisisY, Sumpio B. Do vascular surgery patients need a cardiology work-up? A review of pre-operative cardiac clearance guidelines in vascular surgery. Eur J Vasc Endovasc Surg 2003;25:110–7. 7. Kakisis J, Abir F, Liapis C, Sumpio B. An appraisal of different cardiac risk reduction strategies in vascular surgery patients. Eur J Vasc Endovasc Surg 2003;25:493–504. 8. Kilaru S, Frangos SG, Chen AH, Gortler D, Dhadwal AK, Araim O, et al. Nicotine: a review of its role in atherosclerosis. J Am Coll Surg 2001;193(5):538–46. 9. Sumpio BE. Foot ulcers. N Engl J Med 2000;343(11):787–93. 10. Frangos S, Kilaru S, Blume P, Shin J, Sumpio B. Classification of diabetic foot ulcers. Improving communication. Int J Angiol 2002;11:158–64. 11. Bone GE, Pomajzl MJ. Toe blood pressure by photoplethysmography: an index of healing in forefoot amputation. Surgery 1981;89(5):569– 74. 12. Bowers BL, Valentine RJ, Myers SI, Chervu A, Clagett GP. The natural history of patients with claudication with toe pressures of 40 mmHg or less. J Vasc Surg 1993;18(3):506–11. 13. Carter SA, Tate RB. Value of toe pulse waves in addition to systolic pressures in the assessment of the severity of peripheral arterial disease and critical limb ischemia. J Vasc Surg 1996;24(2):258–65. 14. Weitz JI, Byrne J, Clagett GP, Farkouh ME, Porter JM, Sackett DL, et al. Diagnosis and treatment of chronic arterial insufficiency of the lower extremities: a critical review. Circulation 1996;94(11):3026– 49. 15. Gahtan V. The noninvasive vascular laboratory. Surg Clin North Am 1998;78(4):507–18. 16. Harward TR, Volny J, Golbranson F, Bernstein EF, Fronek A. Oxygen inhalation-induced transcutaneous PO2 changes as a predictor of amputation level. J Vasc Surg 1985;2(1): 20–7. 17. Ballard JL, Eke CC, Bunt TJ, Killeen JD. A prospective evaluation of transcutaneous oxygen measurements in the management of diabetic foot problems. J Vasc Surg 1995;22(4):485–90; discussion 90–2. 18. Quigley FG, Faris IB. Transcutaneous oxygen tension measurements in the assessment of limb ischaemia. Clin Physiol 1991;11(4):315–20. 19. Blume P, Paragas L, Sumpio B, Attinger CE. Single stage surgical treatment of noninfected diabetic foot ulcers. J Plast Reconst Surg 2002;109:601–9. 20. Taylor Jr LM, Porter JM. The clinical course of diabetics who require emergent foot surgery because of infection or ischemia. J Vasc Surg 1987;6(5):454–9. Editor’s note: For related articles, see “Vascular Intervention In Difficult Wounds” in the July 2002 issue of Podiatry Today or “Rethinking Proper Patient Selection For Limb Salvage Interventions” in the August 2006 issue. Also be sure to visit the archives at www.podiatrytoday.com.
CE Exam #152 Choose the single best answer to the following questions. 1. In regard to intermittent claudication … a) patients may complain of pain in the buttocks or calf that is relieved with activity and exacerbated by rest. b) classical symptoms may be obscured by neuropathy in patients with diabetes. c) patients may experience burning pain in the forefoot that is aggravated by dependency and relieved with elevation. d) all of the above 2. When elevating the extremity above the level of the central venous pressure to facilitate an accurate assessment of the degree of arterial flow, … a) the normal extremity will remain pallid while the extremity with arterial insufficiency will exhibit an intense rubor. b) the normal extremity will remain pink while the extremity with arterial insufficiency will exhibit an intense rubor. c) the normal extremity will remain pink while the extremity with arterial insufficiency will become pallid. d) none of the above 3. When evaluating the severity of arterial insufficiency in an affected limb, it is important to differentiate between the rubor associated with _________ and the cellulitis that accompanies _________________ . a) an active infectious process, vascular insufficiency b) deep vein thrombosis, an active infectious process c) vascular insufficiency, an active infectious process d) None of the above 4. When it comes to ulcerations caused by ischemia, they typically … ? a) occur on the tips of the toes and between the digits. b) exhibit profuse bleeding. c) occur over the metatarsal heads on the plantar surface. d) none of the above 5. Which of the following noninvasive vascular tests provides important functional information on the adequacy of perfusion? a) Transcutaneous oximetry b) Skin perfusion pressure c) Segmental limb pressures d) All of the above 6. In regard to limb pressure measurements, why is the proximal thigh pressure usually recorded 30 to 40 mmHg higher than the brachial pressure? a) The thigh cuff width is often not appropriately 20 percent of the diameter of the limb at the thigh level to provide an accurate pressure reading. b) The thigh cuff often lacks sufficient inflation to garner an accurate pressure reading. c) The thigh cuff width is often not appropriately 80 percent of the diameter of the limb at the thigh level to provide an accurate pressure reading. d) None of the above 7. In regard to limb pressure measurements … a) a 20 mmHg pressure gradient between successive levels on the same extremity correlates with flow limiting vascular lesions. b) pressure gradients are significantly elevated among patients with multilevel disease c) systolic pressures measured at the same level in both legs normally should not differ by more than 10 mmHg. d) none of the above 8. Which of the following tests is reportedly more reliable in assessing foot perfusion in patients with diabetes? a) Segmental pressures b) Exercise testing c) Toe brachial index d) None of the above 9. Previous studies have shown that TcPO2 measurements can accurately predict … a) diabetic foot ulcers. b) the severity of foot ischemia. c) the healing potential of diabetic foot wounds even in the presence of local edema. d) none of the above 10. Which of the following statements is true about color duplex imaging? a) It is particularly reliable in the infrapopliteal segments. b) It appears to be effective for the assessment of occlusive disease of the lower extremities, especially above the knee. c) It facilitates vessel identification and a view of anatomic detail of the vessel. d) b and c Instructions for Submitting Exams Fill out the enclosed card that appears on the following page or fax the form to the NACCME at (610) 560-0502. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam. Responses will be accepted up to 12 months from the publication date.