Page 6 - Carotid and peripheral vascular interventions textbook
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                     A                                                      B






                    Figure 12-3. Duplex ultrasonography to determine the location and degree of stenosis. A: Doppler wave form of a patent right femoral artery
                    showing triphasic pattern. B: Different doppler wave forms changing from a typical triphasic pattern to a biphasic, and f nally monophasic
                    presentation in a signif cant stenotic lesion.

                    Computed tomography                             complementary and supplants the current gold standard of
                    angiography (CTA)                               digital subtraction angiography (DSA). The limitation of

                        Lower extremity CTA is not the primarily preferred     MRA is lacking visualization of vascular calcif cations
                    diagnostic test, but it can be helpful for planning     (Fig. 12-4 B), which is a possible impediment when considering
                    revascularization strategies and offers quicker image    revascularization options. In addition, MRA has some limitations
                    acquisition  capabilities  compared  with  magnetic     in patients with metallic clips, prosthetic implantation,
                    resonance angiography (MRA) (13). CTA creates images   implantable def brillators and permanent pacemakers.
                    of vascular structures using cross-sectional plains which
                    may be reconstructed into 3-dimensional angiographic-  Digital subtraction angiography

                    like images. Importantly, CTA visualizes calcif cation      DSA provides an improved overall arterial tree
                    clearly (Fig. 12-4 A), which is benef cial when considering   visualization  and  a  more  accurate  assessment  of
                    revascularization strategies. At femoropopliteal segments,   stenosis. DSA is the standard method for diagnosing PAD
                    the sensitivity, specif city, and accuracy rates are 96%,   and is normally applied for delineating the location and
         334        85%, and 92%, respectively (14). Since it requires large   extension of arterial pathology before a revascularization
                    volumes of iodinated contrast media, CTA is unsuitable   procedure. The major advantage is the capability to
                    for renal insuff cient patients. Another disadvantage is   selectively assess individual vessels to obtain physiologic
                    radiation exposure.                             information such as pressure gradients, and to function as
                                                                    a percutaneous intervention platform. The disadvantages
                    Magnetic resonance angiography                  are its invasiveness using ionizing radiation, arterial
                        Non-contrast MRA which relies on inf ow can   puncture, with potential nephrotoxicity from iodinated
                    overestimate the degree of stenosis. Contrast-enhanced   contrast agents.
                    MRA is better in determining and assessing the severity of
                    stenosis and can help in decision between surgical and  INDICATIONS
                    endovascular revascularization (13). In addition, MRA
                    can give helpful information such as the reconstitution of        Based on 2016 AHA/ACC guidelines on the management
                    blood f ow distal to the occlusion, the vessel runoff beneath   of patients with lower extremity PAD (15), indications for
                    the knee and also the anatomy of the aortoiliac bifurcation     revascularization have been reserved for only a subset of
                    for crossover technique. Currently, MRA imaging is   symptomatic PAD patients, including those with:
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