Disclosures Vascular Testing in the CLI Patient None 2015 UCSF Vascular Symposium Warren Gasper, MD Assistant Professor of Surgery UCSF Division of Vascular Surgery Critical Limb Ischemia Chronic Limb Ischemia characterized by Ischemic Rest Pain Tissue Loss (non-healing ulceration or gangrene) Prognosis High risk of limb loss High risk of cardiovascular events Vascular Testing in Critical Limb Ischemia 1. Diagnostic Criteria Is this CLI? 2. Prognosis Will this heal? 3. Surveillance after revascularization 1
Which of the following tests is best suited to predict the healing potential of a patient with peripheral artery disease and an ulcer on the great toe? A. Contrast angiography with digital subtraction B. Computed Tomography Angiography (CTA) C. Transcutaneous pressure of oxygen (tcpo 2 ) D. 3-phase bone scan C o n t r a s t a n g i o g r a p h y w i.. 10% 10% C o m p u t e d T o m o g r a p h y... T r a n s c u t a n e o u s p r e s s u r e.. 81% 3 - p h a s e b o n e s c a n 0% Methods for Assessing Arterial Insufficiency Hemodynamic Measurements Ankle-brachial index (ABI) Toe-brachial index (TBI) Segmental Doppler Pressures Pulse Volume Recordings Tissue Perfusion Measurements Transcutaneous pressure of oxygen (tcpo 2 ) Skin Perfusion Pressure (SPP) Indocyanine green angiography (ICGA) Anatomic Imaging Duplex ultrasound, CTA, MRA, Angiography Ankle-brachial index Toe-brachial index ABI < 0.4 is consistent with severe PAD CLI is defined by absolute ankle pressure <50mmHg or <70mmHg with tissue loss Advantages: Cheap, quick, easy Disadvantage: Limited use in CLI due to tibial calcification TBI 0.70 0.2 0.5 <0.2 Severity of PAD No significant PAD Moderate PAD Severe PAD / CLI Cuff on the toe, PPG or Doppler probe to monitor digital artery CLI is defined by absolute toe pressure <30mmHg or <50mmHg with tissue loss Advantages: Quick Digital artery calcification is uncommon Disadvantages: Special equipment Requires a toe 2
Transcutaneous pressure of oxygen (tcpo2) Transcutaneous oxygen tension measurement using a small electrode on the skin Transcutaneous pressure of oxygen (tcpo 2 ) tcpo 2 in practice Oxygen tension reflects the metabolic state of the tissue Limited use in mild to moderate PAD, because oxygen delivery far exceeds demand Severely limited inflow is necessary to create a condition where the balance of oxygen supplydemand can be assessed A reading of 0 represents consumption of all available oxygen, not a lack of flow Interpreting tcpo 2 values: >55mHg is normal >40mmHg wound healing is likely <10mmHg wound healing is unlikely Advantages Validated diagnostic and prognostic value in CLI Measurements are not affected by arterial calcification Can be performed at any level, regardless of wound, lack of toes, etc Disadvantages Time-intensive (30 minutes) Poor reproducibility Can be affected by many factors: Age Skin temperature Body temperature Sympathetic tone Cellulitis Edema Obesity Venous pressure Vertical level of the leg 3
Skin Perfusion Pressure (SPP) Laser Doppler probe detects RBC movement up to 1.5mm below the skin Coupled with a blood pressure cuff, the Skin Perfusion Pressure (SPP) can be measured Andersen CA J Vasc Surg 2010; 52:Suppl S Skin Perfusion Pressure (SPP) 403 limbs / 211 patients with PAD 50% diabetic, 21% dialysis-dependent 94 limbs with tissue loss Interpreting SPP values SPP >50mmHg is normal SPP <30mmHg wound healing is unlikely Advantages: Can be done at any level Results are independent of arterial calcification Disadvantages Reproducibility can be affected by the same factors as tcpo 2 J Vasc Surg 2008;47:318-23 4
Indocyanine green angiography (ICGA) Method for assessing regional perfusion using an intravascular fluorophore Indocyanine green is administered intravenously and an 806nm wavelength laser is used for excitation. Resulting fluorescence is recorded with a digital camera ICG has a half-life of 2.5 3 min Fluorescence is recorded for about 2 minutes after injection Promise: operator-independent, reproducible data on regional perfusion at the wound site 13 patients with CLI assessed before and after revascularization Phase I/II type report of the parameters that can be measured with the technique J Vasc Surg 2013;57:1213-8 Testing Angiosomes Angiosome-targeted revascularizations may improve wound healing Angiosome anatomy is typically assessed with angiography The value of angiosome-specific perfusion measured with SPP, tcpo2, or ICGA remains to be seen J Vasc Surg 2013;57:1213-8 Scand J Surg 101: 125 131, 2012 5
Imaging in CLI Multi-level arterial stenosis is common in critical limb ischemia Pulse exam Presence/absence of femoral and pedal pulses Duplex ultrasound Pro: Non-invasive, hemodynamic assessment Con: Limited evaluation of iliac and heavily calcified arteries Computed Tomography Angiography (CTA) Pro: Fast, non-invasive imaging Con: Radiation, iodinated contrast, calcium bloom Magnetic Resonance Angiography (MRA) Pro: no-radiation, no calcium artifacts Con: gadolinium contrast, long acquisition times Angiogram Pro: resolution, hemodynamic assessments, therapeutic Con: invasive, radiation, iodinated contrast Conclusions Toe pressure is the gold standard for noninvasive testing to predict wound healing There is no single perfect test for assessing foot perfusion in critical limb ischemia Perfusion based techniques may have a better predictive value for wound healing and for planning angiosome-directed revascularizations, although current technologies are limited by reproducibility 6