RENAL ANGIOGRAPHY AND ANGIOPLASTYRenal Arteriogram and Angioplasty Techniques
Renal revascularization interventions for renovascular hypertension include angiography, angioplasty, stent placement, selective renal vein renin sampling and rarely embolization. Main goals of renal angioplasty: 1. Eliminate or decrease the need for medical therapy, 2. Avoid or delay surgical revascularization. Indications for renal angioplasty: Poorly defined and are still evolving. -Poorly controlled hypertension on >3 antihypertensive medications and/or elevated creatinine. Contraindications for angioplasty or stenting Advanced disease, creatinine > 3-4 mg/dL (vary) Small kidney Limited life expectancy Severe bleeding diathesis In adults: Recent myocardial infarction, pregnancy Indications for renal stenting: (1) Post-angioplasty rupture/bleeding (2) Flow-limiting dissection not responsive to balloon and anticoagulation (3) very early recurrence following successful angioplasty. Pre-procedure Evaluation and Management 1. Treatment guided by several factors: age, size, extent of disease, natural history of the lesions, technical difficulty, and ease of medical treatment. 2. All patients should be seen by nephrology and preferably reviewed by the Midaortic Syndrome-Renal Artery Stenosis (MAS-RAS) team (nephrology, interventional radiology, cardiology, transplant surgery). 3. Peri- and intraprocedural management of anti-hypertensive medications (e.g. beta blockers and angiotensin-converting enzyme inhibitors) should be coordinated between nephrology and anesthesia. 4. Decide of initiation or discontinuation of antiplatelet therapy (aspirin and clopidogrel-Plavix) pre-operatively. Anticoagulants are held. 5. Review of cross-sectional imaging. The renal-aorta angle should be noted. 6. Labs: Renal function, CBC, coagulation profile, typing and cross matching. 7. Consent should include angiography, angioplasty, stent placement, selective renal vein renin sampling and embolization. 8. Transplant surgery consultation is available in the event of a major vascular adverse event. 9. To determine if lesions will benefit from procedure, pre-captopril and post-captopril DMSA scintigraphy and selective renal vein renin sampling may be helpful in selective cases. Technique: Cross-sectional imaging findings: Imaging studies are carefully reviewed to determine 1. Number of renal arteries, 2. Location and Orientation of arteries, 3. Stenosis analysis: site, length, degree, involved branching, etc. 4. Status of the aorta and mesenteric vessels. - Generous Intravenous hydration with normal saline throughout the procedure. Arterial access 1. Femoral access is the standard. Brachial artery access can be considered for significant downward angulation of the affected renal artery. 2. Sheath: Either with 1. Long sheath (e.g. (30-45 cm, 6-Fr Balkin or Check-flo) or 2. Regular Pinnacle sheath with guiding catheter (5-6 Fr Envoy). Renal Angiography 1. Abdominal aortogram at the level of the renal arteries with multi-sidehole, calibrated flush catheter (4 or 5 Fr Sos Omniflush> pigtail catheters). Projection guided by cross-sectional imaging to illustrate the ostium. For aortography in children, contrast rate of 1-1.5 ml/kg/sec and DSA at 2-4 frames/sec can be used. 2. Selective renal artery catheterization: 4 Fr or 5 Fr catheters (e.g. MP, SOS, Cobra). At least one frontal and two oblique projections coned to the kidney area. Reflux into the aorta to opacify ostium is crucial. The parenchymal and venous phases are only needed for the first frontal study. Lateral and craniocaudal obliquities may reduce artery foreshortening and demonstrate the ostium. 3. Contrast dose preferably kept < 3 mL/kg. To decrease dose, 50% contrast dilution and biplane DSA, carbon dioxide (aortogram). Renal Angioplasty
Renal Venous Sampling - Main and Selective sampling from segmental veins for precise localization - Can be a good predictor of favorable angioplasty outcome - More useful in children. Technique: 2-3 samples are collected from each location listed below using simple curved or reversed curved catheters (e.g 5 Fr Cobra). For selective renal vein branches, a large microcatheter (e.g. Renegade HF) may be needed. Samples should be labelled and numbered in proper fashion and documented in the report of the procedure. Discard the first couple of mLs (>dead space) aspirated from catheter.
Three simple ratios and equations to interpret renal venous sampling:
1. Vaughan formula: V-A/A (V = Renal vein renin and A = Artery renin). Normal 0.24 (Sens 75%, spec of 100%). - Potentially curable by intervention if:
2. Renin Ipsilateral/contralateral Ratio> 1.5 (=Renin hypersecretion). Less accurate (sens and spec ~ 60%) 3. Renin contralateral/ Infrarenal IVC. Ratio < 1.3 (=Renin suppression). Renal Artery Stenting Balloon mounted stents covering the ostium and protruding into the aorta for 2-3 mm is used when indicated. Completion angiogram is then performed via the side arm of the sheath. Adult size renal artery: Only 3 stent systems are approved for use in the renal artery: Palmaz stent (Cordis), the AVE stent (Medtronic), and Express SD (Boston Scientific). But only the Express SD remains available. Renal artery < 5 mm: high restenosis rate (~ 50%). Consider 1. Coronary stents: VeriFLEX Bare-Metal coronary stent Boston Scientific), 2. Drug-eluting coronary stents such as Taxus (Cook) or ION™ Paclitaxel-Eluting Platinum Chromium Coronary Stent System or 3. Covered stents such as iCast stent (Atrium). Two access stent systems: Either over 0.014- 0.018 or 0.035”. 0.035 stents: have better hoop strength, visibility and less dog-boning but are large, stiff, difficult with severe narrowing. Palmaz Genesis (Cordis), AVE stent (Medtronic), and Express SD stent (Boston Scientific). Only the Express remains available. Tools: 6 Fr renal-shaped sheaths such as Ansel 1, 2, or 3 sheath (Cook), Destination (Terumo), or BriteTip sheath (Cordis). Over the wire, the sheath/dilator is advanced up to the renal ostium. For more support for nonostial lesions, the sheath can be advanced into the renal artery. 0.014/0.018 stents: such as Express SD (Boston Scientific), Herculink (Abbott), Genesis (Cordis), Palmaz Blue (Cordis), and 418 (Cook). Tools: 6 Fr guide catheter or a 5-Fr guide sheath. A renal-shaped guide catheter, such as the LIMA, RES, RESS (Boston Scientific), or RDC (Cordis). Stent technical notes: - Stent diameter: 20% larger than normal artery (not poststenotic dilatation) - Stent length: 1-2 mm longer than lesion - Ostial stents: 2 mm into aortic lumen and flaring of end with 1 mm larger balloon - Avoid placing a stent across branching (may cause hypertension). With major branching, consider kissing balloon angioplasty or surgical revascularization. - Severe pain during angioplasty/stent: adventitia overstretched (may cause rupture). Selective cannulation of the affected renal artery: Reverse-curve catheter (Sos II, AngioDynamics) and guidewire (e.g. standard Glidewire (Terumo) or Bentson. Catheter is pulled to engage and traverse the lesion over the wire, guidewire is exchanged for a stenting purpose wire over which the stenting procedure can be performed, such as an 0.014-inch Spartacore (Abbott), an 0.014-inch Mailman (Boston Scientific), or a 0.018-inch McNamara nitinol J wire (Cook) (for 0.014/0.018-inch stents) or Rosen wire (AngioDynamics) (for 0.035 stents). Postoperative Monitoring, Follow-up and Outcomes Admission overnight under nephrology for BP monitoring. Alternatively, the patient (particularly older children and less complex procedures) is discharged the same day after observation for 6 hours and nephrology assessment. Patients who underwent cutting balloon angioplasty or visible dissection are admitted to the ICU. Contrast-induced nephropathy: Renal function should be assessed at 48-72 hours after the procedure, if the contrast volume was substantial or baseline renal function compromised. Serum creatinine level obtained 24 hours postprocedure can often be misleading. Follow-up assessment by nephrology within 2 weeks. 1 month later, with decreasing frequency if pressures were well controlled. Follow up parameters: Blood pressure, serum creatinine, and number of antihypertensive medications. Doppler US was done at 6 weeks, 6 months, 1 year, and yearly thereafter. For stents: Combination of oral antiplatelet therapy: 81 mg daily of aspirin for 3 months after angioplasty, clopidogrel once daily for at least 4 weeks. Indications for repeat angiogram and angioplasty: 1. Clinical worsening, 2. Recurrence of symptoms during follow-up or if 3. In-stent restenosis on US. Indications for surgical revascularization: Technical failure of initial PTA, failed clinical response to repeat PTA , stenosis at major branching, List of BASIC Tools 1. Cook Check-Flo performer introducer sheath. Mullin design. 6-12 Fr, 48-75 cm long, or Envoy Guiding Catheter (Codman), 90- 100 cm, 5 Fr (0.056”), 6Fr (0.07”). 2. 4-5 Fr Omni flush or pigtail catheter. 3. Maverick Over-the-Wire PTCA dilatation catheter (Boston Scientific), Nominal=6 ATM, Rated =14 ATM, 0.014” wire, 135 cm, 6 Fr sheath, Diameter: 1.5, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4 mm. Balloon length: 9, 12, 15, 20, 25, 30 mm. 4. Cutting Balloons (Flextome, Boston Scientific), Number of atherotomes=3 or 4, 2.00-4.00 mm x 6 -15 mm. • Discrete (≤ 15 mm in length), or tubular (10 to 20 mm in length) • Reference vessel diameter (RVD) of 2.00 mm - 4.00 mm • Readily accessible to the device • Light to moderate tortuosity of proximal vessel segment • Non-angulated lesion segment (< 45°) • Smooth angiographic contour • Absence of angiographically visible thrombus and/or calcification 5. Stabilizer Plus wire (Cordis) Stainless steel. 0.014”. 180-300 cm. Supersoft. Hydrophobic. Core-to-tip support weight wire. Stabilizer XS provides extra support. DEFINITIONS Hypertension = BP> 95th age-sex–specific percentile. Normal renal function: creatinine (age dependent) < 1 mg/dL and creatinine clearance (Schwartz) > 60 mL/min. Clinical benefit= free of recurrent hypertension, renal morbidity, increased creatinine >20%, progression to hemodialysis, and death. Definitions of improvement in renal function varied: e.g. 20% increase in eGFR (estimated Glomerular Filtration rate) or 15-20% improvement in creatinine clearance, or decrease in creatinine by 10-20%, Technical success: sustained increase in blood vessel diameter, residual stenosis ≤ 30%. Suspected restenosis: Increase in BP after a period of improvement after angioplasty Response criteria (Ellis et al and Great Ormond) (1) “Cured”: Normal BP (<95th percentile) with no antihypertensive treatment (2) Improved BP with same or reduced treatment (3) No change in BP despite angiographic success (4) Technical failure (5) BP >95th percentile because of cerebrovascular disease - Pressure gradient: mean 10 mm Hg (or peak sys 20) at 50% stenosis - Flow limiting dissections (TIMI flow <3): TIMI 3 defined as clearance of contrast within two cardiac cycles). Dissections arbitrarily divided into types I to III or types A to F: • Type A — Luminal haziness • Type B — Linear dissection • Type C — Extraluminal contrast staining • Type D — Spiral dissection • Type E — Dissection with reduced flow • Type F — Dissection with total occlusion REFERENCES 1. Corriere MA, Pearce JD, Edwards MS, Stafford JM, Hansen KJ. Endovascular management of atherosclerotic renovascular disease: early results following primary intervention. J Vasc Surg. 2008 Sep;48(3):580-7; 2. McLaren CA, Roebuck DJ. Interventional radiology for renovascular hypertension in children. Tech Vasc Interv Radiol. 2003 Dec;6(4):150-7. 3. Srinivasan A, Krishnamurthy G, Fontalvo-Herazo L, Nijs E, Keller MS, Meyers K, Kaplan B, Cahill AM. Angioplasty for renal artery stenosis in pediatric patients: an 11-year retrospective experience. J Vasc Interv Radiol. 2010 Nov;21(11):1672-80 4. Arthurs Z, Starnes B, Cuadrado D, Sohn V, Cushner H, Andersen C. Renal artery stenting slows the rate of renal function decline. J Vasc Surg. 2007 Apr;45(4):726-31; discussion 731-2. 5. Jaff MR, Bates M, Sullivan T, Popma J, Gao X, Zaugg M, Verta P; HERCULES Investigators. Significant reduction in systolic blood pressure following renal artery stenting in patients with uncontrolledhypertension: results from the HERCULES trial. Catheter Cardiovasc Interv. 2012 Sep 1;80(3):343-50.. 6. Shroff R, Roebuck DJ, Gordon I, Davies R, Stephens S, Marks S, Chan M, Barkovics M, McLaren CA, Shah V, Dillon MJ, Tullus K. Angioplasty for renovascular hypertension in children: 20-year experience. Pediatrics. 2006 Jul;118(1):268-75. |