Page 210 - Libro 2

190
PART 3 — PERIPHERAL ARTERIAL
􏰀70% DR stenosis is a criteria for a loss of “stenosis- free” patency whether repaired or selected for watch- ful observation in the asymptomatic patient. An open or percutaneous secondary intervention undertaken to maintain or improve functional angioplasty changes the procedural outcome to “assisted” primary patency. If the angioplasty site thrombosed and a secondary pro- cedure is performed to restore patency, the outcome status changes to “secondary” patency. A successful surveillance program following PTA should produce an assisted-primary patency in the range of 80% to 90% at 2 years and no significant improvement in second- ary patency. Failure to identify clinically significant le- sions prior to thrombosis is present if the primary and assisted-primary patency rates are similar.
An abnormal or change in ABI indicates PAD, but is not diagnostic for angioplasty site failure. In many diabetic patients, the measurement of ABI is inaccu- rate and limb arterial testing requires pulse volume recording and duplex testing to evaluate limb per- fusion and PTA functional patency. The application of objective criteria provided by duplex scanning is essential for a useful surveillance program. The use of combined threshold criteria for intervention
SUMMARY
(i.e., PSV 􏰀300, Vr 􏰀3.5) is associated with a high (􏰀90%) positive predictive value when compared to angiogram findings for 􏰀70% DR stenosis.
The initial surveillance examination should be per- formed within 2 weeks, and ideally combined with an outpatient vascular clinic evaluation to assess the patient’s activity level, to assess ASO risk factor mod- ifications, and to review drug (antiplatelet, statin) therapy. If the initial PTA testing is “normal,” follow- up testing in 3 months is appropriate for patients treated for CLI and in 6 months in claudicants. Sub- sequent testing is individualized at 6- to 12-month intervals. If initial duplex testing detects a residual 50% to 70% DR angioplasty site stenosis, a repeat evaluation in 4 to 6 weeks is safe and reliable in the detection of stenosis progression. The patient should be instructed that new limb ischemia symptoms should be evaluated in the vascular laboratory imme- diately. Abbreviated testing intervals (i.e., 3 months) may also be appropriate during the first year follow- ing endovascular treatment of TASC C and D lesions due to the higher likelihood of failure. The incidence of reintervention is higher following balloon (30%) than stent (20%) angioplasty.
The application of duplex ultrasound surveillance following peripheral arterial inter- ventional procedures can be useful and should be considered a part of PAD patient care. Reliance on the patient to recognize changes in limb perfusion is not reliable. Interpreting arterial testing that is performed within a surveillance protocol can be challenging, and some vascular specialists are not convinced that routine duplex surveillance is of benefit, worth the health care expense, or that the vascular labora- tory is competent to execute a quality surveillance program. Duplex surveillance, when correctly performed and interpreted, should improve patency and clinical out- comes following endovascular therapy—an intervention with known limited func- tional patency and performed in a patient cohort subject to ASO disease progression.
Critical Thinking Questions
1. During a duplex examination of a patient with a superficial femoral artery stent, the common femoral artery ultrasound reveals an acceleration time
of 210 ms. With this information, how would you augment the examination and why?
2. A patient comes in for a duplex ultrasound examination 6 months following a balloon angioplasty and stent placement. At this time interval within the follow-up protocol, where is the most likely place along the limb where a stenosis may be present?
3. When examining a patient postballoon angioplasty and stenting, do you ex- pect the PSV within the treated site to be similar to or different from a patient who underwent an atherectomy?