Vascular Evaluation in Patients with Lower Extremity Ulceration

Written by
Michael Cumming, MD, MBA

Introduction

Over 30% lower extremity ulcers and non-healing wounds arenot fully resolved at 6 months even though patients have received “best careavailable” and spending 10’s of billions of dollars in direct care costs.1–4 Nearly 15% of Medicare beneficiarieshave lower extremity ulcers with a conservative estimated annual cost of $32billion.5 Compounding this is therising prevalence (1-2%) of leg ulcers as people are living longer.6 Despite an abundance ofstudies and guidelines, there is significant variation in recommendations,which are often contradictory, causing confusion and raising barriers topatient’s receiving appropriate care.

Deficiencies in the management of leg ulcers are common andare due to incorrect diagnosis and treatment.7–9 Inappropriate treatment maycause deterioration of the wound, delay in wound healing and harm to the patient.Barriers to healing include lack of consensus, interprofessional rivalry, nostandardization,  care deliverystructure, limited resources and educational gaps.10,11 The delivery of health careservices is in a state of constant flux which is detrimental tointerdisciplinary teamwork, professional relationships, and a collaborativeenvironment.

This brief addresses the often misunderstood and underappreciatedrole of arterial and venous disease in patients with lower extremityulceration.

Knowledge Gaps

Nonhealing wounds are not a disease, but a symptom of anunderlying condition.12 Successful treatment dependson an accurate diagnosis of the underlying cause. The vast majority, over 85%,of lower extremity wounds have arterial, venous or mixed arterial and venousdisease as a primary cause.13–17

Much emphasis has been put on the making clinical diagnosisbased on ulcer anatomical location, characteristics, and morphology.14,18 While useful, this approachcan cause tunnel vision and result in patient’s not receiving appropriatetimely care. Old maxims such as all plantar wounds are neuropathic, or venouswounds only occur in the setting of varicose veins are wrong.

When faced with a lower extremity wound, the task at hand isto rule out an underlying correctable contributing etiology. This requires in-depthknowledge and understanding of the utility of clinical evaluation and diagnostictesting to include or exclude arterial and venous disease. 19–21 There are many physiologicand imaging tools to identify patients with arterial and venous disease. Mostof these tests are “good tests” but not “great tests”. They must be interpretedwith an understanding of the sensitivity, specificity, and disease prevalence. Inshort, the question is, “what is the chance that the clinical condition will bepresent or absent in the context of a positive or negative test?”.21

Arterial Disease

One of the first steps in evaluating a patient with a lowerextremity ulcer is to exclude ischemia as a potential contributor to the woundand to determine if revascularization required. Appallingly, in the UnitedStates, almost 50% of patients who undergo a major lower extremity amputation,do not have an appropriate arterial evaluation prior.22–24 An in-depth discussion of thenuances of evaluating lower extremity arterial perfusion in the setting ofcritical limb ischemia (CLI) is the subject another brief (“Evaluation of FootPerfusion”). The basics are covered here.

At the bedside, our primary tools include identifying riskfactors for peripheral arterial disease (PAD) and physical examination finding.Important risk factors include (but not limited to) smoking, diabetes, age, cardiovascularand cerebrovascular disease. Physical exam findings include pulses, capillary refill,trophic changes (loss of hair, dry scaly skin) and ulcer characteristics. Thesetools are useful for identifying patients with PAD – “rule in”.

However, these clinical tools are not useful to “rule out” significantPAD.25–27 More specifically, the clinicalexamination for ischemia has a “poor negative predictive value and should notbe used in isolation to triage patients with non-healing ulcers”.28

The presence or absence of PAD must be determined usingobjective testing. Objective tests for PAD are broadly classified into 2categories: physiologic and anatomical. Physiologic testing includes anklebrachial indices (ABI), toe brachial indices (TBI), segmental pressures, skinperfusion pressures, transcutaneous oxygen tension, pulse volume recordings, dopplerwaveforms and other newer modalities. Non-invasive anatomical imaging includesarterial ultrasound (US), CT angiography, and MR angiography. Physiologic testingshould always be utilized before anatomical imaging.29

Frustratingly, there are difficulties and limitations with physiologicevaluation. Surprisingly, the ABI, widely considered the gold standard fordetecting PAD, has limited negative predictive value in the setting of criticallimb ischemia, being falsely reassuring and falsely negative in over 30% of patients.30,31 An ABI should not be used inisolation when evaluating for CLI. The addition of a TBI improves the detectionof the presence of significant ischemia.32 Alternatively skin perfusionpressures (SPP), although not as well validated, are another option for vasculartesting in patients with CLI.

Diagnosing PAD is not always simple.33 A pragmatic approach, startingwith a detailed history and physical exam, followed by testing with ABI and TBIor SPP, is a cost effective strategy.34 Finally, prior to any amputation,referral to a critical limb expert for catheter angiography, should be mandatory.35

Venous Disease

Venous ulcerationis extremely distressing for patients, greatly affecting their quality of life,and causing about 40% more days of lost employment than any other disease.36,37 Our knowledge of the pathophysiology,hemodynamics, diagnostic imaging, and treatment of chronic venous insufficiency(CVI) has expanded greatly, particularly in the last decade. Venous pathology developsfrom valvular incompetence, obstruction, and/or muscle pump dysfunction causingvenous hypertension.38

Like PAD, theclinical findings (varicose veins, hyperpigmentation, statis dermatitis,atrophie blanch, lipodermatosclerosis) are useful to “rule in” CVI. There areno studies on the utility of these findings to “rule out” significant venousdisease. Unfortunately, there is the all-too-common misconception that the absenceof these clinical findings implies that there is no significant venous disease.The absence of varicose veins and/or leg swelling does not confer that apatient does not have significant venous disease.39 This can only be determined by objectivetesting.

Testing for CVI ispoorly understood by non-vascular specialists.40 This is due to limited education duringmedical training, rapidly evolving knowledge, and the variety of testsavailable.

Not all venous USstudies are the same. Most (all) clinicians are familiar with ordering a venousUS to evaluate for deep venous thrombosis (DVT). This examination has onepurpose - to determine if a patient has or does not have DVT. Unfortunately,even this widely used test, is inconsistently performed and can have higherfalse negative rate than expected.41 It is important for physicians to recognizethat a DVT US does not evaluate venous valvular function or venous obstruction.

Venous incompetenceUS is the primary diagnostic tool for evaluating venous valve function in boththe superficial and deep venous systems of the lower extremity.42,43 The adequate performance of a venous incompetenceUS requires specially trained and experienced US technologists. The supervisionand interpretation of these US studies must be done by a specialist with a deepunderstanding of the complexities of lower extremity venous disease.44

Venous obstructionis divided into inflow and outflow. Inflow disease is defined as obstruction inthe deep veins (common femoral, femoral, and popliteal veins) and outflow diseaseas obstruction of the iliac veins and/or the inferior vena cava.

The importance ofvenous outflow obstruction in the setting of CVI is becoming better understood.45–47 Physiologic testing, primarily with air plethysmography,is no longer reimbursed by Medicare. Non-invasive diagnostic imaging including venousUS, CT venography and MR venography while useful lack well validated parametersfor determining outflow disease. Invasive imaging with intravascular ultrasound(IVUS) is the best tool for identifying patients with significant venousoutflow compression.48

Inflow venous obstructionprimarily occurs after lower extremity DVT and is one of the main causes of postthrombotic syndrome (PTS).  Evaluation ofthe lower extremity deep venous system and potential therapies is an area ofintense research.49,50

Finally, all patientswith a suspected venous ulcer should have measurement of the ankle-brachialindex at the time of initial presentation.51

Conclusion

Lower extremitywounds are complex and challenging for patients, families, and healthcareproviders. Most lower extremity ulcers are secondary to either or both arterialand venous problems. A comprehensive history and physical assessment followedby appropriate imaging are essential to identify, diagnose and develop careplans. Dedicated vascular specialists should be involved in the care of alllower extremity ulcers and wounds to determine or exclude the presence ofsignificant arterial and/or venous disease.7,52 Rapid referral and treatment of theunderlying problem has been shown to improve wound healing, reducing patientmorbidity and improving quality of life.53–56

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