Vascular Surgery: PAD and ABI

Vascular Surgery Overview

• Vascular surgery addresses five main conditions
  • Peripheral arterial disease (PAD)
  • Carotid disease
  • Aneurysms
  • Dialysis access
  • Venous disease
• Vascular surgery procedures are primarily preventative or restorative

PAD Approach

• The approach to PAD includes indication, imaging, and interventions

Indications for Vascular Intervention in PAD

• PAD is indicated by an Ankle-Brachial Index (ABI) <0.9 or >1.3, suggesting arterial wall calcification
• Vascular interventions in PAD aim to improve lower extremity perfusion to:
  • Increase walking function
  • Improve wound healing
  • Avoid major amputation

Ankle-Brachial Index (ABI)

• The ABI measurement includes 6 measurements:
  • Both arms (brachial)
  • Both ankles (DP and PT)
• ABI is calculated as the highest ankle pressure divided by the highest arm pressure.
• ABI <0.9 indicates PAD
• ABI >1.3 suggests non-compressible/non-diagnostic vessels
• A drop in ABI after exercise indicates PAD

Toe-Brachial Index (TBI)

• TBI uses a special cuff on the toe with a PPG or Doppler probe to monitor the digital artery
• Digital arteries are less likely to be calcified compared to ankle arteries
• TBI provides prognostic information for critical limb ischemia cases
• TBI is less useful for intermittent claudication

PAD Prevalence

• Peripheral arterial disease prevalence is around 10-20% in individuals (men and women) over 65

PAD - Risk Factors

• Risk factors include:
  • Age
  • Smoking
  • Cardiovascular disease history (heart disease or stroke)
  • Diabetes
  • Chronic kidney disease and dialysis
  • Hypertension
  • Hyperlipidemia

Medical Management of PAD

• Cardiovascular disease (Heart attack and stroke) is the leading cause of death in PAD patients
• Key medical management includes:
  • Smoking cessation
  • Aspirin (or other antiplatelet therapy)
  • Blood pressure control
  • Blood glucose control
  • Statin therapy
  • Exercise

Asymptomatic PAD

• Patients are able to engage in walking without intermittent claudication
• Patients do not have ischemic rest pain or ischemic tissue loss (no ulcer or wound)
• There is no indication for an invasive procedure
• Best medical therapy for cardiovascular risk factors, exercise, and proper foot care is the only intervention.

Intermittent Claudication

• Muscle discomfort reproducibly produced by exercise, relieved by rest within 10 minutes.
• Normal, healthy leg arteries increase blood flow for increased oxygen demand during exercise, maintaining stable ankle pressure
• Arterial disease limits supply of blood in PAD. When demand exceeds supply, Ankle pressure drops and pain occurs

Claudication and Anatomy

• The muscle distcomfort location predicts the issue :
  • Hamstrings, buttocks = iliac artery disease
  • Gastrocnemius = iliac and/or femoropopliteal disease
• Patient characteristics must match the disease.

Leg Pain

• Leg pain with walking is not always PAD
• Alternative causes:
  • Neurogenic- Nerve root compression / irritation (sciatica)
  • Spinal stenosis
  • Arthritis
  • Chronic venous obstruction (DVT)
  • Non-atherosclerotic arterial disease
  • Popliteal (artery) entrapment
  • Popliteal aneurysm
  • Emboli

Intermittent Claudication Evaluation

• Check the patients ABI
  • If the ABI is normal at rest, consider exercise ABI
• Ensure that patient characteristics are correct
• Ensure the symptoms are correct
• Is an alternative diagnosis more likely?
• Will improving extremity blood flow improve symptoms, and function?

Chronic Limb Threatening Ischemia

• Severe pedal pain, typically in the distal foot and toes
• Often improves when foot is dependent
• Worsens at night with recumbent patient position
• Tissue loss includes :
  • Ulceration/gangrene
  • Distal (toes)
  • Characterized by lack of wound healing, despite appropriate wound care

Chronic Limb Threatening Ischemia Outcomes

• Severe ischemia indicates extensive arterial disease
• High risk of major amputation without intervention
• Cardiovascular disease high death risk - Proper treatment for cardiovascular disease is crucial

WIfI Classification System

• With non healing wounds, it is important to stage with SVS Wound. Ischemia, and Foot Infection (WIfI) classification system:
  • Wound
  • Ischemia
  • Foot Infection
• The WIfI stage predicts risk of major amputation at one year (stage 1 = 0 vs stage 4 = 30%)

Using WIfI to Save Feet

• Wound -Initiate appropriate wound care -Off load wound
• Ischemia
  -Look for it -Improving severe ischemia reduces the risk of amputation -In CLTI, arterial disease is extensive
• Foot infection -Early and aggressive drainage -Antibiotic therapy, as appropriate

PAD-Important Considerations

• Asymptomatic PAD: Intervention: Best medical therapy, smoking cessation, exercise, proper foot care
• Intermittent Cladication: First line intervention: Best medical therapy and regular exercise (i.e. walking 30-45min, 4-5 days per week)
  • Assess anatomy and consider an invasive procedure with lifestyle limiting IC
• CLTI: Intervention: Best medical therapy, imaging, and invasive procedure likely is needed to avoid amputation.

Imaging

• Look for ischemia signs
  • Hair loss
  • Shiny skin
  • Dependent Rubor
• Pulse exam- always palpate first -Doppler only if needed
  • Femoral pulses
  • Pedal Pulses

The Vascular Foot Exam

• Includes inspection of :
  • Color
  • Hair
  • Skin health
  • Wounds/ulcers
  • Structural Variations
  • Prior Amputations.

How to Feel the Femoral Pulse

• Patient must be supine
• Pulse caudal to the medial ⅓ of the inguinal ligament:
• If at groin crease- then too low!

PAD Patterns

• Younger (50s) Smokers
  • Aortoiliac disease
  • Diabetes and dialysis patients
• Tibial artery disease
• Small vessel disease
• Critical Limb Ischemia
  • Multilevel disease

Arterial Anatomy

• Inflow :
  • Aorta
  • Right/ Left Iliacs
  • Right/ Left CFAs
• Femoro-Popliteal arteries
  • Profunda
  • SFA
  • Popliteal
  • Adductor canal
  • Knee joint
• Tibial arteries:
  • PT
  • Peroneal
  • AT
  • Ankle
• Foot Vascular Anatomy:
  • Dorsalis pedis
  • Posterior tibial
  • Plantar arch
  • Toe Joints

Imaging - Vascular

• To treat each tibial artery is a specific region of the foot, also known as angiosomes
• Revascularization with an intact plantar arch is probably best. Angiosome anatomy is typically assessed with angiography.

Imaging - Arteries

• Obtain imaging of arteries Duplex Ultrasound
• Computed Tomography Angiography (CTA)
• Magnetic Resonance Angiography (MRA) -Arterial angiogram (digital subtraction angiogram)

Duplex Ultrasound- Overview

-Advantages -Cheap -Portable

• No radiation
• No IV access
• Dynamic images -Disadvantages
• Operator dependent -Consuming to get full map -Arterial wall calcification will obscure artery lumen -Unpredictable imaging above the inguinal ligament

CTA- Overview

-Advantages: -Fast image acquisition -Able to visualize calcification/stents

• Disadvantages: -Ionizing radiation -Iodinated contrast damage renal function
  • "Calcium Bloom" limits visualizing tibial and pedal arteries
  • Static assessment

MRA-Overview

• Advantages: -No ionizing radiation -No calcium interference leads to improved visualization
• Disadvantages: -Gadolinium contrast is not used with advanced renal disease -Slow image acquisition -Obscure artery assessment -Static assessment

Digital Subtraction Angiography Overview

• Advantages: -Dynamic arterial assessment -Can perform hemodynamic assessments -Can be a therapeutic procedure -Superior resolution of pedal/tibial arteries
• Disadvantages: -Ionizing radiation -Lodinated contrast -Invasive -Can underestimate stenosis

PAD- Modalities

• Duplex Ultrasound: Is best used for surveillance (angioplasty, stent, bypass)
• MRA or CTA
  • Good, noninvasive initial choice for imaging from the aorta to the toes - but weakness is the tibial arteries
• Angiogram -Invasive, but superior tibial and pedal artery resolution and has the opportunity to create an intervention

Summary

• PAD is defined as of an ABI <0.9 or >1.3
• Goals in patients are to improve lower perfusion in order to
  • increase walking
  • improve wound healing
  • avoid amputation
• Process of imaging starts with physical exam and predicts what sort of interventions are needed/possible