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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3955_Библиотеки_им_академика_М_И_Перельмана.pdf
Renal Artery Angioplasty and Stenting
Sanjay Misra
Clinical Features
• Patients with uncontrolled hypertension will often present with headaches,
palpitations, chest pain, and blurry vision.
• Young women with hypertension who are not on oral contraceptives often have
fibromuscular dysplasia (FMD).
• Patients with renal artery stenosis (RAS) in the sixties, seventies, and eighties
have typically atherosclerotic renal artery stenosis.
• On physical examination, patients with renal artery stenosis will often have a
flank or lateral epigastric bruit over the affected kidney.
• Suspect RAS in patients who
b
Develop renal insufficiency while on angiotensin-converting enzyme (ACE)
inhibitors
b
Patients with malignant hypertension
b
Patients with long-standing hypertension which accelerates without cause
b
Patients with flash pulmonary edema (usually due to bilateral RAS)
Diagnostic Evaluation
Laboratory
• Kidney function should be assessed prior to intervention with serum blood urea
nitrogen, creatinine, and an estimated glomerular filtration rate calculated using
Modification of Diet in Renal Disease (MDRD) formula or a short clearance.
• Blood pressure evaluation should be performed. A 24-h blood pressure monitor
may be useful.
• Anti-hypertensive medications need to be optimized. Most patients should be
on an ACE inhibitor, a beta-blocker, and a diuretic. This should be managed by
a physician who is familiar with these medications and can optimally manage
them.
141
R.A. Morgan, E. Walser (eds.), Handbook of Angioplasty and Stenting Procedures,
Techniques in Interventional Radiology, DOI 10.1007/978-1-84800-399-6_12,
C
Springer-Verlag London Limited 2010
142 S. Misra
Imaging
• Non-invasive imaging of the renal arteries can be performed using computed
tomographic analysis, magnetic resonance angiography, or ultrasound:
Ultrasound
b
One advantage of ultrasound is that it is a non-invasive test, which can be
performed in patients with normal and abnormal kidney function.
b
Sometimes difficult to determine if patient has FMD and limited by body
habitus and bowel gas.
b
Resistive indices (RIs) should be determined in both kidneys prior to inter-
vention. Resistive indices are used to predict a successful outcome in patients
with hypertension, typically an RI of less than 0.7 is favorable for a successful
outcome after treatment.
b
The velocity measurement of blood in the renal artery can predict the likeli-
hood of a stenosis. Usually a peak systolic velocity of greater than 180 cm/s
is predictive of a stenosis. In addition, a ratio between the blood velocity in
the aorta to renal artery of >3.5 is suggestive of a stenosis. For restenosis after
angioplasty or stent placement, similar blood velocities in the stented artery
can predict restenosis.
b
The size of the kidney is important by ultrasound and 8-cm or larger kidneys
should be stented or angioplastied.
Conversely, small kidneys (<6–7 cm) respond poorly to renal artery
intervention.
Computed tomographic angiography (CTA)
b
One advantage of CTA is that it is a non-invasive test which can be performed
in patients with pacemakers and provides anatomical information with regard
to the presence of aortoiliac arterial occlusive disease.
b
CTA is sensitive for detecting FMD.
b
Stenosis determination hindered in the presence of exuberant vascular calcifi-
cations
Magnetic resonance imaging/magnetic resonance angiography
b
One advantage of MRI/MRA is that it is a non-invasive test which can be
performed in patients and provides anatomical information with regard to the
presence of aortoiliac arterial occlusive disease.
b
One disadvantage of MRI/MRA is that gadolinium has been associated with
nephrogenic sytemic fibrosis in patients with decreased glomerular filtration
rate (GFR less than or equal to 30) and is contraindicated in these patients.
b
MR performs better in the presence of calcification.
b
Newer MR sequences actually allow MR angiography without the use of
contrast agents.
Renal Artery Angioplasty and Stenting 143
Promising new method, which avoids risks of iodinated contrast and
gadolinium and ionizing radiation
Digital Subtraction Angiography
b
“gold standard” for accurate evaluation of RAS
b
Enables hemodynamic measurements to determine significance of RAS
b
In case of contrast allergy or renal failure, alternative contrast agents are
available:
Carbon dioxide for renal dysfunction
Gadolinium for iodinated contrast allergy
Modern fluoroscopic units have the ability to optimize imaging for alter-
native contrast agents
Indications
• Renal artery angioplasty or stent placement is performed in patients with
b
Uncontrolled hypertension
In young patients
In older patients who previously had well-controlled hypertension
b
Worsening renal function
b
Cardiac destabilization syndromes – sudden episodes of
Congestive heart failure
Flash pulmonary edema
Unstable or refractory angina pectoris
• Fibromuscular dysplasia (FMD) responds well to angioplasty of the renal artery
and stenting is reserved for flow-limiting dissections.
b
In the event of restenosis with FMD, repeat angioplasty remains effective
• Atherosclerotic renal artery stenoses respond best to primary stenting.
Contraindications
• Abnormal coagulation studies with elevated INR (>1.8), PTT (>60 msec), or
decreased platelets (<50 ×10
3
mm
3
).
• Severe iodinated contrast allergies
◦ Consider CO
2
or gadolinium angiography
• Renal failure with GFR <40
◦ Pre treat with N-acetylcysteine, intravenous hydration
◦ Consider CO
2
angiography
144 S. Misra
Patient Preparation
• The patient is encouraged to take his normal medications on the date of the
procedure, but otherwise is kept fasting (NPO) for 8 h.
• Laboratory investigations include hemoglobin, prothrombin time (PT), interna-
tional normalized ratio (INR), partial thromboplastin time ( PTT), platelets, and
serum creatinine prior to the procedure.
• Consider checking the hemoglobin and serum creatinine 48 h after the
renal artery procedure to assess for bleeding and contrast medium-induced
nephropathy.
Relevant Anatomy
Normal Anatomy
• The renal arteries typically arise immediately inferior to the superior mesenteric
artery near the L
1
–L
2
intervertebral disk space.
• Typically, 70% of the patients have one renal artery supplying each kidney. In
20–35% of the patients, there is more than one renal artery supplying each kidney.
Aberrant Anatomy
• There may be an early bifurcation of the renal artery.
• The renal artery may uncommonly arise from the common iliac artery, external
iliac artery, superior or inferior mesenteric arteries.
Renal Artery Angioplasty and Stent Equipment
• The original description of renal artery angioplasty was described using a
0.035
wire and balloon. Today, r enal artery stents and angioplasty are typically
performed using 0.014–0.018
compatatible catheters and wires.
• The balloons and stents are monorail for 0.014
or over the wire for 0.018
systems, many of which require the use of a guiding catheter.
• The guiding catheter shape is based on the orientation of the renal artery origin.
Multiple different types of guiding catheter shapes are available with different
wires of different stiffness and torqueability.
• One popular option is a 6F (IM) guide catheter (Boston Scientific, Natick, MA)
used to engage the renal orgin.
b
A 0.014
Reflex (Cordis Endovascular, Miami, FLA) or Sparta Core (Abbott
Vascular, Redmond, CA) wire is used to cross the renal artery stenosis.
b
The tip of the wire should not prolapse as this may cause a subintimal
dissection.
Renal Artery Angioplasty and Stenting 145
Pre-procedure Medications
• Except those with contraindications such as fluid overload and asthma, patients
with glomerular filtration rate less than 30 check in to the hospital 1 day before
the procedure for
b
Overnight prehydration with oral fluids and/or intravenous crystalloids ±
N-acetylcysteine (Mucomyst) to prevent the potential nephrotoxic effects of
the contrast.
N-acetylcysteine 600 mg orally every 12 h for four doses (two before and
two after angiography).
One method for intravenous hydration is Dextrose 5% in water (850 mL)
with 154 milliequivalents sodium bicarbonate administered at 3 mL/kg/h
for 1 h before procedure and 1 mL/kg/h for 6 h post-procedure.
Procedure
Access
• Patients receive moderate sedation using a combination of midazolam hydrochlo-
ride (Versed, Abraxis Pharmaceutical Products, Schaumburg, IL) and fentanyl
citrate (Hospira, Inc, Lake Forrest, IL) for pain as needed administered through
a peripheral intravenous line by a registered nurse. The common femoral artery
is typically used and anesthetized using 5–10 mL of 2% lidocaine hydrochlo-
ride (Hospira Inc, Lake Forrest, IL). The brachial artery or radial artery can be
used. The common femoral artery is accessed using a Seldinger technique. A
6F sheath is placed and an IM guide catheter is used to engage the renal orgin
(Figs. 1 and 2).
Fig. 1 Renal angiogram
showing “string of beads”
appearance in a patient with
fibromuscular dysplasia
(arrow)
146 S. Misra
Fig. 2 Atherosclerotic ostial
renal artery stenosis (arrow)
Angiography
• A renal angiogram is performed in the appropriate oblique to image the renal
origin “en face.” Typically, a 15–25
◦
LAO projection using 4–8 mL of contrast
infused at 4 mL/sec is performed
Assessing the Lesion
• Renal artery stenosis is defined as a diameter reduction of greater than 50% by
visual estimate when compared to its immediate, distal non-dilated main renal
arterial segment. A pressure gradient is obtained if there is a question of lesion
severity.
b
A mean pressure gradient measured between the aorta to distal renal artery
of 10 mm of Hg or a systolic gradient of more than 20 mm of Hg is
hemodynamically significant.
• Renal artery stenosis are classified into “ostial” if it is located less than or equal
to 5-mm distance away from renal artery origin from the aorta and “non-ostial”
if it is located more than 5-mm away from renal artery origin.
Renal Artery Angioplasty and Stenting 147
• Fibromuscular dysplasia has a “string of beads” appearance, which can involve
the main renal arteries and its branches. It typically affects women in their forties
and sixties with 80% incidence of bilaterality (Fig. 1). There are three types of
FMD:
b
Medial fibroplasia (most common, 70% of the patients) – string of beads most
common angiographic appearance
b
Intimal fibroplasia (20%) – younger patients (often infants). Tubular, concen-
tric stenoses are characteristic
b
Subadventitial fibroplasia (10%)
• Atherosclerotic renal artery stenosis is characterized by ostial disease, which has
dense calcification (Fig. 2). In 6–10% of the patients, there can be atherosclerotic
RAS with FMD.
Intra-procedural Medications
• Before stent placement or angioplasty, one should administer
b
Bolus of unfractionated heparin intravenously (50 units per kilogram of body
weight).
b
Nitroglycerin in 50–100 µg aliquots to prevent guidewire-induced spasm in
the peripheral renal arteries.
Performing the Procedure
Crossing the Lesion
• First, a floppy (soft-tipped) wire or glide wire carefully traverses the renal artery
lesion. It is important to keep the guidewire within the lumen of the vessel as a
subintimal dissection can occur very easily.
• To select the renal artery, some use a cobra-type catheter, while others use a
Shepard’s hook catheter (Simmons type). Regardless of the catheter used, the
operator must use extreme care to pass the guidewire through and not underneath
the renal occlusive lesion in question.
• Two methods exist to measure the length and diameter of the renal artery stenosis
b
Visual estimation – using the field of view and guide catheter size as markers
to estimate distances
b
arker catheter – use to calibrate the length of the stenosis and diameter of the
non-diseased renal artery using the software provided with the angiographic
suite.
148 S. Misra
Angioplasty/Deploying the Stent
• Atherosclerotic RAS requires the radial force of balloon-expandable stents, the
choice of which is based on the preference of the interventionalist as there are
many different types available.
• Typically, appropriate renal artery stent diameters are 5–8 mm with a length of
12–15-mm based on the length of the stenosis and diameter of the non-diseased
renal artery. The diameter of the stent should not be larger than the diameter of
the non-diseased renal artery since this can lead to dissection or rupture.
• If the stent cannot cross the renal artery stenosis, consider a 3–4-mm predilation
of the renal artery stenosis to allow easier passage of the stent.
• Deploy the renal artery stent to its nominal diameter based on the pressure chart
supplied with the stent from the manufacturer.
• Perform follow-up angiography after stent deployment to the stent to ensure that
there is no renal artery dissection, rupture, or spasm (Fig. 3).
• Carefully assess the peripheral renal arteries for embolization, which can occur
in 10–20% of renal artery stent placement procedures.
• FMD almost always responds to angioplasty alone with a balloon diameter of
1.1–1.2 greater than that of the non-diseased renal artery.
b
Consider a renal stent only if there is a dissection limiting renal artery blood
flow.
• Endpoints:
b
“Technical success” – less than 30% residual stenosis after deployment of the
stent on follow-up angiogram.
Fig. 3 Arrow showing spasm
caused by the wire after renal
artey stent placement
Renal Artery Angioplasty and Stenting 149
b
Systolic pressure gradient <10 mmHg or mean pressure gradient <5 mmHg
• The sheath and catheter are removed once the activated clotting time has
decreased below 200.
Immediate Post-procedure Care
• Patients recover as after any vascular procedure with femoral access with the
following additional considerations:
b
Hydration post-procedure – oral and intravenous
b
Precautions for orthostatic hypotension
Patients are instructed to avoid standing quickly and to have assistance
when standing for the first day.
b
Patients should keep a more detailed log of their blood pressure (3–4 times
daily) and present to the physician treating their hypertension so that he can
modify drug regimens accordingly.
b
Some recommend checking serum creatinine and GFR in 1–2 weeks to look
for evidence of cholesterol embolization syndrome.
Delayed presentation of renal dysfunction due to the slow time course of
multiple peripheral and segmental areas of renal ischemia.
Follow-Up and Post-procedure Medications
• Six-week course of dual antiplatelet therapy using a loading dose of
ClopidogrelPlavix 300 mg by mouth (Bristol-Myers Squibb/Sanofi
Pharmaceuticals Partnership, Bridgewater, NJ) and then 75 mg once daily.
In adddition, patients take one baby aspirin (81 mg) every day.
• Patients are followed with serial duplex ultrasound to evaluate for restenosis.
Restenosis typically occurs in 15–20% of the patients at 9 months.
• Periodic serum BUN, creatinine, and blood pressure measurement to evaluate for
functional outcome.
• Restenosis of renal arteries is retreated with a number of different approaches
including
b
Repeat angioplasty
b
Cutting balloon angioplasty
b
Cryoplasty
b
Placement of a new stent
b
Covered or drug-eluting stent placement.
150 S. Misra
Alternative Therapies
• Embolic protection devices: Embolic protection devices (EPDs) have been used
to prevent atheroembolism during treatment of stenosis involving saphenous vein
bypass grafts used as arterial conduits for coronary artery disease and in conjunc-
tion with the placement of a carotid artery stent. Recently, several reports have
described the use of these devices to prevent atheroembolism during renal artery
stent placement. It has been hypothesized that these devices may help prevent
atheroembolism during renal artery stent procedures. There are several papers
now describing the role of EPDs with renal artery stent placement in patients
with chronic renal insufficiency but no level 1 evidence to support their use.
• Drug-eluting stents: Renal arteries with diameters measuring less than 4 mm
have a lower patency rate after angioplasty and stent placement because of higher
incidence of in-stent restenosis and have typically been not stented. Drug-eluting
stents (DESs) have been used for the treatment of stenosis involving the coro-
nary arteries with lower restenosis rates, and may offer a potential alternative to
BMS in renal arteries with diameters less than 4 mm. There have been several
case reports of the use of DES for treating de novo RAS involving the bifurca-
tion of the renal artery or in-stent restenosis. In a small series from the Mayo
Clinic, DES were used to renal artery stenosis with good technical results and
low restenosis rates when compared to bare metal stents despite the DES group
having significantly smaller diameter renal arteries when compared to bare metal
stents.
Results of RAS Angioplasty and Stenting
• Percutaneous renal artery angioplasty with stent placement has become the
cornerstone therapy for the treatment of atherosclerotic renal artery stenosis.
• Reported technical results are excellent with a 98–100% procedural success rate.
• The effect on renal function is difficult to predict.
b
Improves in only 30–40% of patients
b
Stabilizes in another 30–40%
b
Deteriorates in 20–30%
• Angioplasty performed for FMD has better results with improvement in blood
pressure in as many as 90% of patients.
b
This success rate applies for repeat angioplasty in FMD as well.
Complications and Their Treatment
• There are many different types of complications which can occur during a renal
artery stent placement.