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15 Pulmonary Arteriovenous Malformations 153
a
Fig. 15.4 (a) Non-selective pulmonary trunk injection showing recanalization of left lower lobe
PAVM embolized 10 years before(yellow arrowhead), new left and right upper lobe PAVMs (red
arrows). Despite maximum field of view, there is exclusion of peripheral lung. (b) Rt UL lesions
occluded with detachable silicone balloons and pushable fibered coils. Non-selective completion
angiogram reveals small Rt LL lesion (white arrow) excluded from previous non-selective image
b
device does embolize is potentially useful in preventing the device lodging in the
carotid.
• This risk can lead to selection of too large a device, which then creates a risk
of coils stringing back and not coiling—this is not good as it prevents distal
occlusion and restricts access for subsequent treatment.
• Detachable coils may be useful, since appropriate coil size can be confirmed
before final deployment.
• Coil deployment technique is very important (Fig. 15.5) (see Chapter 2).
• Do NON-SELECTIVE completion angiogram to detect other vessels supplying
the PAVM.
• The risk of paradoxical embolization has led to the development of detachable
devices which do reduce the risk of this complication at the cost of increased
complexity and higher costs. The recently introduced Amplatzer vascular plug
devices are screw-detachable plugs that are s afe and easy to use, but do not yet
have the proven long-term efficacy of coils.
• The risk of paradoxical emboli remains until all lesions are treated. Meticulous
technique is important to avoid ANY air or blood clot entering the system during
the procedure. Wire withdrawal with the catheter tip abutting a vessel sidewall
produces a vacuum that fills with air if the catheter hub is open to air. Since
superselective catheterization almost always requires the use of a shaped catheter,
this situation is difficult to avoid in smaller vessels; having to torque and withdraw
154 G. Robinson
Fig. 15.5 (Anchor and scaffold diagrams courtesy of Dr Robert I White Jr) (a) The anchor tech-
nique involves deploying the first few centimeters of coil into a side branch and then weaving the
remainder of the coil as shown. A coaxial guide catheter or sheath is important to allow sufficient
forward pushability of the inner catheter. (b) The scaffold technique involves deployment of a high
radial force initial coil (typically 2 mm oversized to the vessel), with a softer platinum coil then
woven in
the catheter to free the tip can be time-consuming and ultimately unsuccessful in
allowing sufficiently distal canulation of small vessels. Various techniques can be
used to exclude air including wire exchanges with the catheter hub held beneath
the surface in a bowl of saline (simple but can be messy, and difficult to see with
backbleeding of blood into the saline) or using a closed system (Fig. 15.6) with
pressurized saline, which is more cumbersome but secure.
Fig. 15.6 Closed system
comprising: coaxial catheters,
clear tubing (allows air
bubbles to be seen), Tuohy
Borst adapter, two-way taps,
and obturator for the coil. The
tubing is connected to a
pressurized bag of
heparinized normal saline
running at about two
drips/second
15 Pulmonary Arteriovenous Malformations 155
• Clot formation and paradoxical embolization are potential risks during treatment
of PAVM. Heparinization during the procedure may help reduce this; the author
favors heparinization but the evidence is only anecdotal.
Aftercare
• There is a small incidence of pleuritic chest pain when the aneurysm sac thromboses. This can occur shortly after the embolization (up to 48 h) or may be
delayed and typically occurs at 4–6 weeks. This can be severe but rarely requires
more than non-steroidal analgesia and reassurance. Some operators advocate
treating only one lung at a time because of the potential risk of bilateral pleuritic pain. Geography of patient’s travel time to hospital may override this
consideration.
Post-embolization
Day case or overnight stay.
Clinic visit, phone call, or email contact a few days later.
Follow-Up
• Annual clinical review and clinical assessment for continued occlusion of PAVM
and to follow any known untreated small PAVMs.
• Radiation dose is clearly an issue, particularly with the potential for multiple follow-up imaging studies. Contrast-enhanced echocardiography and oxygen
saturations are preferable for solitary lesions.
• Contrast-enhanced CT is necessary if there are untreated PAVMs.
• Pulmonary angiography every 5-years, should be performed more frequently if
◦ Large lesion(s) treated, as recanalization is more likely with large or complex
feeding vessels.
◦ Return of symptoms.
◦ Reduction in oxygen saturation.
• Screen relatives.
Keypoints
Screen family for HHT and PAVMs.
No air introduction during angiography/embolization!
156 G. Robinson
Embolize as close to the sac as possible.
Correct device size is crucial—do not oversize coils too much, since they
will misplace the catheter.
Non-selective completion angiogram.
Safety
If you have not done one before, discussing a case with someone who has may
be helpful:
http://www.hht.org/living-with-hht/treatment-centers/
is a good place for con-
tact details.
Suggested Reading
1. Pollak JS, Saluja S, Thabet A, Henderson KJ, Denbow N, White RI Jr. Clinical and anatomic
outcomes after embolotherapy of pulmonary arteriovenous malformations. J Vasc Interv
Radiol. 2006 Jan;17(1):35–44
2. Lee WL, Graham AF, Pugash RA, Hutchison SJ, Grande P, Hyland RH, Faughnan ME.
Contrast echocardiography remains positive after treatment of pulmonary arteriovenous malformations. C hest. 2003 Feb;123(2):351–8.
Chapter 16
Systemic Arteriovenous Fistulae
Robert Rosen
Clinical Features
• An arteriovenous fistula (AVF) is a direct connection between an artery and vein.
• AVFs are not the same as arteriovenous malformations (Chapters 14 and 15).
• AVF can be considered according to etiology, site, and symptoms.
• AVF can be congenital or acquired (e.g., iatrogenic for dialysis or following
trauma or biopsy).
• Local effects include dilation and tortuosity of the afferent artery and draining vein, ischemia distal to the AVF, and venous hypertension with secondary
degenerative changes in the vein wall and overlying skin.
• Physical examination demonstrates increased pulsation and a thrill; marked dilation and tortuosity of the draining veins; and hyperpigmentation, thickening, and
eventual ulceration of the skin distally (Fig. 16.1).
Fig. 16.1 Photograph of a
patient with extensive skin
changes resulting from an
AVF of her fourth digit
• The distal ischemia may be severe and be the patient’s primary complaint, with
atrophy of the distal soft tissues, cyanosis, rest pain, and ischemic ulceration.
• Reversal of flow in the distal artery (steal) is common.
• Venous hypertension may also occur with time and exacerbate distal ischemia.
Transcatheter Embolization and Therapy,
Techniques in Interventional Radiology, DOI 10.1007/978-1-84800-897-7_16,
C
Springer-Verlag London Limited 2010
157
158 R. Rosen
• Generalized cardiovascular effects are related to both the shunt and the decrease
in peripheral vascular resistance, and include increased circulating blood volume,
increased cardiac output, and in severe cases, cardiac dilation and eventual highoutput failure.
• High-output states are much more common in arteriovenous fistulae (AVF) than
in arteriovenous malformations, which generally have a complex nidus rather
than a direct arteriovenous connection, resulting in higher resistance to flow.
In fact, clinically apparent high-output failure in complex AVMs is relatively
uncommon.
• Resting tachycardia may be present in patients with large fistulae, and slowing of the pulse with compression of the feeding artery (Branham–Nicoladoni
sign) is a classic physical finding which confirms the presence of a high-output
state.
• Most fistulae increase in size and flow over time and will require treatment.
It is preferable to treat them prior to the development of secondary pathologic changes, and particularly before secondary irreversible cardiac dilation
occurs.
Diagnostic Evaluation
Laboratory
• Standard pre-angiography laboratory evaluation should be undertaken, including
the following.
◦ Serum creatinine
◦ Complete blood count
◦ Coagulation profile
◦ Liver panel (if embolization of AVF within the liver)
Imaging
• Imaging studies of value include ultrasound, computed tomography, magnetic
resonance angiography, catheter angiography, and echocardiography for evaluation of the cardiac changes.
• Ultrasound examination will demonstrate enlargement of the feeding arteries and
draining veins, turbulence with mixed arterial and venous signals at the site of
the fistula, and high venous velocities.
• CTA, particularly with 3D reconstruction, can provide a detailed anatomic view
of the location and size of the actual arteriovenous connection and be helpful in
choosing the type and size of embolic device (Fig. 16.2).
• MRA studies will show increased flow and dilation of the involved vessels, but
generally lack the temporal and spatial resolution to permit treatment planning.
16 Systemic Arteriovenous Fistulae 159
Fig. 16.2 Three-dimensional rendering of a CTA of the chest demonstrating a pulmonary AVM of
the right lower lobe (arrow)
• Catheter angiography is usually reserved for treatment or instances when noninvasive imaging does not reveal sufficient anatomical detail to plan therapy.
Indications for Embolization
• Symptomatic AVF: nearly all will require embolization, especially if there is
venous hypertension, symptomatic arterial “steal” syndrome, high-output congestive heart failure or organ insufficiency due to venous hypertension or arterial
steal.
• Asymptomatic AVF: early embolization should be considered to prevent sec-
ondary changes due to venous hypertension or arterial compromise.
Alternative Therapies
• Surgical interventions may be possible in superficial AVF (e.g., in the extremities)
and simple AVFs (e.g., those with few feeding and draining vessels).
• Surgical interventions are CONTRAINDICATED in lesions that are complex;
these lesions should be treated as one would treat an AVM, with endovascular means only. Surgical interventions in such complex lesions can lead to
recruitment of more feeding vessels and a much more difficult endovascular
intervention.
160 R. Rosen
Contraindications for Embolization
• All contraindications are relative, and the risk of doing the procedure must be
weighed against the risk of not doing the procedure!
• Contraindications to angiography
◦ Contrast allergy
◦ Uncorrectable coagulopathy or thrombocytopenia
◦ Renal insufficiency
• Contraindications to embolization
◦ Inability to safely reach target vessel
◦ High risk of embolization of agent through AVF and into pulmonary
circulation
Specific Complications
• Complications of angiography.
• Occlusion of draining vein (may be required as part of embolization procedure).
• Pulmonary embolism—may occur due to migration of agent through AVF or may
occur in delayed fashion from outflow vein thrombosis.
• Paradoxical systemic embolism—may occur if the patient has a concurrent right
to left shunt (e.g., pulmonary AVM).
Anatomy
• Anatomical considerations depend on organ being embolized.
• AVFs, particularly if long-standing, can recruit new vessels similar to an AVM.
Proximal angiography to assess for any unsuspected vessel inflow is vital to a
successful embolization procedure.
• Variant anatomy for any specific organ undergoing embolization should also be
recognized.
Equipment
Catheters
• Non-selective catheters: Pigtail, Omni Flush.
• Selective catheters: variety of according to the anatomy of the target vessels.
• Guide catheter: guide catheters or long sheaths may be particularly helpful to
perform check angiograms and roadmaps during selective catheterization.
16 Systemic Arteriovenous Fistulae 161
Embolic Agents
Coils: Coils are suitable if the afferent artery can be safely sacrificed and the size
and flow rate of the fistula permit them to be securely deployed without risk of
migration.
Other occlusion devices: detachable plugs such as the Amplatzer device offer
many of the same advantages as coils and are simple to use.
Liquid agents: adhesives (n-butyl cyanoacrylate) and polymers (Onyx) may be
useful in certain types of fistulae where achieving a complete seal is difficult.
The choice of agent is determined by the following:
• The size of the feeding and draining vessels.
• The anatomy of the fistula itself (side-to-side, end-to-side, associated aneurys-
mal dilation).
• Rapidity of flow.
• The need to preserve flow in the involved artery or vein.
• The consequences of losing the embolic device or agent through the venous
side of the fistula.
• In some cases a combination of devices, agents, and techniques will be
required.
Medications
Pain Control
• Intraprocedural sedation and analgesia, typically with midazolam and fentanyl
• Post-procedural anti-inflammatory medications (ketoralac, ibuprofen) and pain
medications (opiods) as needed
Infection Control
• Antibiotics not often needed.
Sickness Control
• Anti-nausea medications not often needed.
Hydration
• IV normal saline or D5W as needed.
• These procedures may be very lengthy, in which case more aggressive fluid
management may be necessary.
162 R. Rosen
Angiography
Arterial and/or venous access may be required for effective treatment. In some
instances additional access is required to allow the use of an occlusion balloon to
reduce flow through the AVF and decrease the risk of systemic embolization.
Arterial Access
• Plan according to the anatomy and location of the AVF.
Venous Access
• Required in some anatomic situations, particularly
◦ When there is aneurysmal dilation of the draining vein
◦ When direct trans-arterial access has been sacrificed
◦ When venous embolization alone will lead to thrombosis of the AVF
Assessing the Lesion
• Angiography remains the gold standard for evaluating arteriovenous fistulae,
demonstrating flow patterns, the precise site of communication, and regional
collateral vessels.
• In order to define the anatomy of the fistula, highly selective studies must be
performed and will probably require high-frame rates. If this does not give the
answer, then some form of occlusion of the inflow artery or outflow vein will be
needed.
• If there has been prior unsuccessful intervention, either surgically or with
embolization, then the collateral flow may be so extensive that it is virtually impossible to define the original site of AV communication. The angiographic picture may then be indistinguishable from a complex congenital AVM
(Fig. 16.3).
Angiographic Appearance
• Appearance depends on the degree of shunting with the AVF.
• Long-standing or large AVF may have a very dilated feeding artery and a very
dilated draining vein.
• Multiple feeding arteries may be present—proximal, non-selective angiography
is mandatory to evaluate these arteries.
• The artery distal to the AVF is often normal in size or very small.
• Arterial steal may be present with flow reversal. This is readily demonstrated on
ultrasound. To demonstrate steal angiographically may require the following: