Page 6 - Carotid and peripheral vascular interventions textbook
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                                                                  “Incidental RAS”

                                                               Resistant Hypertension

                                                               Ischemic Nephropathy

                                                               Cardiac Destabilization Syndrome
                                                                  Pulmonary edema
                                                                  Congestive heart Failure
                                                                 Acute coronary syndrome

                    Figure 10-4. A spectrum of clinical presentation of renal artery stenosis.

                    IMAGING STUDIES                                 readily available, although the need to use iodinated
                                                                    contrast makes it an unappealing modality for impaired
                        The ideal imaging study should assess both the main   renal function patients. Gadolinium-enhanced MRA
                    and accessory renal arteries, evaluate the hemodynamic   produces excellent anatomy of the renal mass, renal
                    signif cance of a lesion, recognize the severity and location   arteries, the surrounding vessels, as well as renal excretion
         254        of the stenosis, and recognize related perirenal pathology,   function. However, it has a propensity to overestimate
                    such as renal or adrenal masses or the appearance of an   stenosis, and it may be less helpful in patents with renal
                    abdominal aortic aneurysm. DUS is the f rst-line imaging   artery stents due to artifacts. In impaired renal function
                    test to screen for a signif cant (>60%) stenosis (24). This   patients , the cut-off levels of estimated glomerular f ltration
                    can be repeated to evaluate stenosis progression and its   rate (eGFR) suitable for CTA or MRA study are >60 mL/
                    hemodynamic consequence (e.g., renal vascular resistance   min and >30 mL/min, respectively (23).
                    and f ow velocity). Moreover, the renal resistive index       Digital subtraction angiography (DSA) is still the
                    (RRI) can assist to recognize a more severe stenosis and     gold standard for diagnosing RAS (25). Besides better
                    give additional information on response to intervention     resolution, the major benef t of DSA is the potential to
                    (Fig. 10-5). The RRI is def ned as (peak systolic velocity - end    measure the pressure gradient over the lesion, particularly
                    diastolic velocity) /peak systolic velocity. The normal   for a moderate stenosis. Renal artery fractional f ow
                    range is 0.50-0.70. High resistive indices (>0.8) in native   reserve (FFR) measurement during maximum hyperemia
                    kidneys are associated with poor response to intervention.  triggered by dopamine or papaverine is another way to
                        Multidetector  MRA  or  CTA  (without  or  with    evaluate the severity of RAS that may predict the clinical
                    gadolinium) shows comparable high specif cities (92-98%   response to intervention (26). Because of invasive procedure
                    and 85-93%) and sensitivities (64-100% and 94-97%)    and potential risks of contrast exposure or atheroemboli,
                    to detect signif cant RAS (25). CTA provides better spatial   angiography is normally limited to quantif cation and
                    resolution than MRA (Fig. 10-6) and likely being more   visualization of the stenosis prior to vascular intervention
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