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IN) over the guidewire and position in the suprarenal abdominal aorta. Advance a 5- to 6-F IMA catheter, multipurpose, or JR4 through the long sheath and engage the renal artery (Figs. 5-10 through 5-12).

Peripheral Arterial Disease and Angiography

Assessment of Renal Artery Stenosis Signiﬁcance

Standard selective angiography provides a limited 2D view of the renal artery. Because many clinical trials, predicated on the identiﬁcation of RAS using angiographic measurement, have yielded discordant data on the clinical beneﬁt of renal artery revascularization, there has been great interest in developing reliable strategies to predict those patients who will most likely beneﬁt from renal artery revascularization. In patients with RAS due to FMD, it has been well validated that PTA alone is sufﬁcient to disrupt the webs of tissue responsible for causing the stenosis and is often highly effective to reduce associated HTN (Fig. 5-13). However, in patients with atherosclerotic disease, debate persists regarding who serves most to beneﬁt from revascularization. Similar to the practice in CAD, there has been a recent movement to deﬁne signiﬁcant RAS, not by anatomic severity, but rather by physiologic impact using pressure wire evaluation with induction of hyperemia. Of note, adenosine should not be used in the renal vasculature for the induction of vasodilation because it can paradoxically provoke renal artery vasoconstriction. The optimal vasodilator for the renal vasculature is papaverine, which must be used with heparin-free saline, because the combination of these two drugs leads to formation of a precipitate that may provoke microvascular injury. Some studies have evaluated the use of other vasodilators, including dopamine. A hemodynamically signiﬁcant RAS is characterized by one of the following conditions: (1) resting pressure distal to stenosis/pressure in the aorta (Pd/Pa) <0.90, (2) hyperemic Pd/Pa called fractional ﬂow reserve (FFR) for the coronary circulation <0.80, (3) hyperemic mean gradient > (5) minimal luminal area (MLA) by intravascular ultrasound (IVUS) imaging of 8.6 mm2 or less. Given the limitations of angiography, any intermediate stenosis should likely be assessed using one of these techniques.

20 mm Hg, (4) hyperemic systolic gradient >20 mm Hg, and

Renal Artery Revascularization

Indications for renal artery revascularization include facilitation of BP control in patients with resistant HTN, preservation of renal function, or reversal of end-stage renal failure or prevention of a decline in renal function in selected patients. Renal artery stenting has also been shown to improve functional class in patients with unstable angina and CHF.

Large-scale randomized clinical trials (including DRASTIC, ASTRAL, and STAR), testing the efﬁcacy of renal artery revascularization versus medical management, have concluded that renal artery stenting does not confer signiﬁcant beneﬁt compared with medical therapy. Signiﬁcant methodologic ﬂaws have limited translation of these results to general clinical practice. The most recent CORAL trial enrolled patients with relatively mild clinical indications (patients took two antihypertensive medications), and physiologic assessment of lesion severity was not required. Considering these limitations, renal artery revascularization produced modest improvement in BP control during these clinical trials. Further prospective randomized studies with physiologic determination of stenosis severity may provide greater insight in determining those patients who may beneﬁt from renal artery revascularization.

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Peripheral Arterial Disease and Angiography 263

Figure 5-10 Aortogram showing bilateral renal ar tery stenosis (R AS)

(arrows).

Figure 5-11 Right renal artery stenosis (R AS).

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Peripheral Arterial Disease and Angiography

Figure 5-12 Angiogram of right renal artery after stenting.

Figure 5-13 Angiogram demonstrating ﬁbromuscular dysplasia (FMD) of

the renal arter y. (Image courtesy of Dr. Michael Jaf f.)

Subclavian and Brachiocephalic Intervention

Upper-extremity arterial insufﬁciency due to obstructive disease of the major aortic arch vessels affects up to 7% of individuals in select populations. Atherosclerotic disease most commonly involves the ostium

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or proximal segments of the subclavian and brachiocephalic arteries; in other conditions, such as FMD, large vessel vasculitides (e.g., Takayasu arteritis, giant cell arteritis), thoracic outlet syndrome, or radiation-induced disease may cause lesions in more distal locations.

Symptoms of subclavian obstruction include arm claudication with fatigue, paresthesia, or pain during exertion. The presence of stenosis may ﬁrst be identiﬁed by discrepant BP readings between arms, with a lower BP recorded on the affected side. Proximal left subclavian stenosis may also impede antegrade ﬂow through the left vertebral artery, resulting in symptoms of vertebrobasilar insufﬁciency that may manifest as diplopia or vertigo with left arm exertion, known as subclavian steal. In patients with left or right internal mammary (LIMA or RIMA) bypass grafting for coronary artery bypass graft (CABG) surgery, the presence of proximal subclavian stenosis may result in angina during arm exercise or periods of physiologic subclavian steal.

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Peripheral Arterial Disease and Angiography 265

Noninvasive Testing

In patients with suspected obstructive disease of the upper extremities, CTA or MRA may be helpful to conﬁrm the diagnosis and provide anatomic insight. Imaging studies permit assessment of arch anatomy and degree of atherosclerotic burden and may be helpful for procedural planning if revascularization is considered. Duplex ultrasound may be used to evaluate vertebral artery ﬂow on the affected side. Reversal of vertebral ﬂow found on Duplex characterizes subclavian steal physiology. Presence of the steal phenomenon alone does not warrant revascularization unless the disease involves the left subclavian artery and the LIMA is intended for use in CABG surgery. To conﬁrm the diagnosis of subclavian steal syndrome (vs. phenomenon alone), patients must have symptoms of vertebral-basilar insufﬁciency (VBI), angina, or arm claudication.

Invasive DSA may provide enhanced anatomic detail. Arch aortography using a pigtail catheter placed into the ascending aorta at 40 degrees LAO deﬁnes the origins of the great vessels and permit selective angiography if needed. The determination of translesional pressure gradients to determine the signiﬁcance of intermediate lesions involving the arch vessels may be diagnostic of important stenosis. Selective canalization of the vessels may be performed using a variety of specialized catheters; in cases where prolonged catheter manipulation is required, anticoagulation is recommended.

Revascularization

Revascularization of the brachiocephalic and subclavian arteries is indicated for the presence of signiﬁcant symptoms or empirically if a LIMA is required as a conduit for CABG surgery. Endovascular treatment of the subclavian and brachiocephalic arteries is successful in more than 95% of cases. Surgical bypass is possible but has a comparatively high rate of complications, including cranial nerve palsy, lymphocoele, and morbidity related to the need to enter into the chest cavity. To date, there have been no trials comparing outcomes with open surgical revascularization and endovascular therapy in subclavian and innominate artery distribution.

The optimal approach to upper-extremity revascularization depends on lesion location and arch anatomy. The femoral approach is most often used, although brachial or radial access may facilitate treatment of CTOs, where it may be difﬁcult to localize the vessel’s origin from the aortic arch or maintain adequate catheter support to cross the occlusion. Radial access is gaining popularity and most

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balloon-expandable stent platforms up to 8 mm may be delivered through 6-F sheath systems and postdilatated up to 10 mm with 6-F compatible balloons. Simultaneous femoral and arm access may permit embolic protection of the vertebral artery or carotid in the case of innominate intervention or in cases where complex proximal plaque is felt to pose a particularly high risk for DE.

balloon-expandable stents, because radial force is desirable, precision of deployment is imperative, and this territory is not exposed to extrinsic compression. For lesions located in the more distal portions of these vessels, self-expanding stents may be preferred to accommodate extremity movement and the propensity for ﬂexion, extrinsic compression, and other forces that could result in stent deformation.

ing complication that occurs due to the direct route to cerebral circulation through the vertebral artery. Some operators advocate for the use of cerebral embolic protection at the time of treatment for bulky subclavian or brachiocephalic lesions. No large studies have evaluated the safety or efﬁcacy of this approach, but given the unknown timing of vertebral ﬂow reversal, some operators recommend embolic pro tection. In the rare event of acute thrombotic occlusions of the arch vessels, embolic protection to vertebral and axillary arteries seems prudent, because more DE may occur at the time of instrumentation.

Peripheral Arterial Disease and Angiography

Aorto-ostial and proximal lesions are generally treated with

Atheroembolization, although uncommon, represents a devastat-

Carotid Disease

In the United States, cerebrovascular disease remains the third leading cause of death and represents a signiﬁcant cause of morbidity and health care expenditure. Approximately 800,000 individuals develop a new or recurrent stroke each year, of which two-thirds are ﬁrst-time events and one-third are recurrent. Although 80% of strokes are ischemic in origin and result from long-standing HTN, 20% to 25% are due to atherosclerotic disease of the carotid artery. The risk of stroke from carotid artery plaque itself depends on both the severity of narrowing as well as characteristics of the plaque biology—that is, whether a prior stroke or transient ischemic attack (TIA) has occurred from an unstable lesion.

The highest risk of recurrent stroke occurs in the context of symptomatic severe carotid lesions of 70% to 99% as established by angiography. These data, described in the North American Symptomatic Carotid Endarterectomy Trial (NASCET), ﬁrmly established that the risk of recurrent ipsilateral stroke at a 2-year follow-up was 26%. In less severe but symptomatic stenosis (50% to 69%), the 5-year risk of any ipsilateral stroke was 22.2%. The highest risk of stroke occurred early after the index event, highlighting the importance of early revascularization. Although medical therapy at the time of NASCET was limited, the beneﬁt of early revascularization of symptomatic patients with carotid disease is now well established.

Asymptomatic patients enrolled in the Asymptomatic Carotid Surgery Trial (ACST) with a carotid stenosis more than 60% (determined by ultrasound) were found to have a stroke risk of 11% at 5-year follow-up. In contrast to symptomatic patients, who have a high risk of recurrent stroke early after an index event, the risk of stroke in asymptomatic patients was constant during the 5-year period, implying that revascularization in these patients may be considered on a more elective basis.

Diagnostic Testing

Duplex ultrasonography is the standard test used to assess coronary artery stenosis (CAS). Numerous criteria have been established to

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assist in the diagnosis severe carotid stenosis. In most cases, greater than 80% stenosis correlates with PSV of 300 to 400 cm/sec, an EDV greater than 100 cm/sec, and a ratio of internal carotid artery/common carotid artery (ICA/CCA) systolic velocity of more than 4. Other features, such as the presence of contralateral occlusion, diminished cardiac output from severe left ventricular (LV) dysfunction, valvular pathology such as aortic stenosis, and concomitant CCA stenosis, may render these measurements less reliable. MRA and CTA may also facilitate the identiﬁcation of CAS. Still, catheter-based angiography remains the gold standard for evaluating carotid stenosis. Angiography provides information on vessel anatomy, plaque morphology, ﬂow characteristics, and presence of collateral circulation. These parameters are particularly useful in predicting the safety of carotid endarterectomy (CEA) or carotid artery stenting. However, angiography also carries risks of vascular complications and plaque embolization, although these events are uncommon.

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Peripheral Arterial Disease and Angiography 267

Carotid and Cerebral Angiography

Carotid and cerebral angiography is most commonly performed from the femoral artery approach. However, in some cases, right radial or brachial arterial access may be preferred. Regardless of approach, meticulous procedural technique must be used during carotid and cerebral angiography. It is recommended that anticoagulation with heparin be achieved to prevent catheter- and/or wire-related thrombosis and embolism. Careful ﬂushing and back-bleeding of every catheter must be performed to prevent air or thromboembolism. In most cases, selective angiography of the great vessels should not be completed without ﬁrst performing a nonselective angiogram of the aortic arch.

Standard baseline arch aortography is using a pigtail catheter with power injection (typical volume of 40 cc) in a LAO 30- to 40-degree orientation. There should be limited foreshortening of the catheter. This position permits visualization of the origins and proximal segments of the great vessels and enables determination of arch type, which may indicate any potential technical challenges related to performing selective carotid angiography.

The aortic arch typically gives rise to the brachiocephalic trunk, the left CCA, and the left subclavian artery. The brachiocephalic trunk usually bifurcates into the right subclavian artery and right CCA. In 20% to 30% of the population, the brachiocephalic trunk and left CCA share a common origin. The aortic arch can be classiﬁed into three types, deﬁned by Myla and described by Uﬂacker et al., on the basis of the distance of the origin of the great vessels from the top of the arch (Fig. 5-14). The widest diameter of the left common carotid is used as a reference vessel. In a type-I arch, all great vessels originate within one diameter length (diameter length of the widest portion of the left common carotid) from the top of the arch; in a type-II arch, all great vessels originate within two diameter lengths from the top of the arch; and in a type-III arch, the great vessels originate within more than two diameter lengths from the top of the arch (see Fig. 5-9). In addition, a small segment of the population has the left carotid artery originating from the innominate artery. This is known as a “bovine arch” (Fig. 5-15). Given the potential variability in arch conﬁguration and the marked impact that anomalous conﬁgurations have on procedural technique, arch aortography is a critical ﬁrst step.

Various-shaped catheters are available for selective carotid and vertebral artery angiography. The catheters can be divided into three groups: passive, intermediate, and active shape designs. Use of a particular category of catheter will depend on the type of aortic arch and the geometry of the origins of the great vessels. Passive catheters, such as headhunter, multipurpose, vertebral, and Berenstein, are used to access the great vessels in patients with a type-I

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Peripheral Arterial Disease and Angiography

Type-I

aortic arch

Figure 5-14 Schematic diagram showing classiﬁcation of aortic arch.

Figure 5-15 Bovine arch angiogram demonstrating the left common

carotid arising from the innominate arter y (arrow).

Type-II

aortic arch

Type-III

aortic arch

aortic arch. Intermediate catheters, including the Vitek (Cook, Inc, Medical, Bloomington, IN) and Bentson (JB 1–3; Cordis Corp., Hialeah, FL), require more manipulation than passive catheters and are ideal for type-II aortic arches. Active catheters including the Simmons Sidewinder and Newton catheter are useful for type-II or -III arches but must be shaped in the ascending aorta and therefore may introduce the opportunity for release of atheroemboli. A practical way to shape these catheters requires advancing them into the aortic arch over a wire (an angled Glidewire is recommended). With removal of the wire, the catheter may then be retracted and the tip positioned in the left subclavian artery. Further rotation will allow the catheter to prolapse into the ascending aorta. The catheter can then be manipulated into each speciﬁc great vessel.

Following the review of arch aortography, selection of an appropriate catheter, and assurance that systemic anticoagulation has been achieved, the great vessels may then be engaged. The right anterior oblique (RAO) view allows visualization of the origins of the right common carotid, right subclavian, and right and left vertebral arteries (Figs. 5-16 and 5-17). The LAO view allows visualization of the left common carotid and left subclavian and innominate arteries. Following selective engagement of the common carotid from the arch (or innominate), wiring of the common carotid is often required to allow the catheter to be advanced and appear in the ﬁeld of view for quantitative angiography of carotid bifurcation. Take care with any wire or catheter advancement to prevent the catheter from jumping forward into the lesion. Angiography performed from the proximal or middle portion of the common carotid (if not diseased) is usually sufﬁcient.

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Peripheral Arterial Disease and Angiography 269

Figure 5-16

Once the diagnostic catheter is in place, angiography of the carotid bifurcation in the AP, lateral, and ipsilateral oblique (45 degrees) is obtained. The carotid artery is classically divided into four segments: cervical, petrous (often washed out in appearance as the artery courses through the petrous bone), cavernous, and supraclinoid.

With the catheter selectively in each carotid artery, obtain intracranial imaging in both the AP cranial and lateral projections. Although additional discussion is beyond the scope of this chapter, any operator performing selective carotid and intracranial angiography should be familiar with the anatomy of the major cerebral vessels and branches and should recognize congenital variations as well as the presence or absence of collateral vessels when intracranial disease is present.

Ulcerated plaque in internal carotid artery (ICA).

Vertebral Disease

In contrast to carotid disease, the optimal management of vertebral artery stenosis is less well known, in large part because the manifestations of vertebral disease may be ambiguous and underappreciated. Vertebral arteries provide the blood supply to the posterior aspect of the brain, including the cerebellum. Ischemic insults to this area may manifest with dizziness, ataxia, diplopia, hemiparesis, and bilateral lower-extremity weakness and numbness. The vertebral arteries merge together to form the basilar artery; occlusion of the basilar artery presents as “locked in” syndrome, in which the patient may only control lateral movement of the eyes.

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Peripheral Arterial Disease and Angiography

Figure 5-17 Poststent angiogram of internal carotid artery (ICA).

The primary cause of posterior circulation strokes is embolization from the heart, aorta, or proximal aspect of the vertebral arteries themselves. Transient ischemia of the posterior circulation may also occur in the context of “inﬂow” vessel (subclavian or innominate artery) stenosis or occlusion, where ﬂow is further compromised by transient reduction in BP, or during episodes where “steal” physiology reduces antegrade ﬂow, classically with strenuous use of the ipsilateral arm.

Atherosclerosis represents the most common cause of vertebral artery stenosis, primarily concentrated at the vessel origin. Other, less common causes of vertebral artery stenosis include arterial dissection (usually traumatic), FMD, migraine, and vasculitides, such as Takayasu and giant cell arteritis. The diagnosis of VBI is often quite challenging due to vague and indistinct symptoms.

The location of the arteries and their intercervical course make duplex ultrasonography challenging. The best tests for assessing vertebral arteries include CTA, MRA, and invasive angiography.

Vertebral arteries most commonly arise from the proximal portion of the subclavian artery, although in 5% of patents, the left vertebral may arise directly from the arch. Classically, the vertebral artery is divided into four segments, designated V1 to V4. The V1 section is the one most affected by atherosclerosis and extends from the origin to the point at which the vessel enters the transverse foramina of the vertebra (C5 to C6) where it then becomes the V2 section. From the intervertebral foramina, the vertebral courses behind C2 extracranialy

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Peripheral Arterial Disease and Angiography 271

(the V3 section) and then enters the skull through the foremen magnum, where it is then called the V4 segment. This ﬁnal portion enters into the brain and merges with the contralateral vertebral artery to form the basilar artery. It is common to ﬁnd a size discrepancy between the two vertebral arteries, with the left often the larger of the two. The larger vertebral is often referred to as the “dominant” vessel.

Conclusion

Peripheral arterial disease is prevalent and encompasses a wide spectrum of disorders. Clinicians must be vigilant for vascular disease, since the diagnosis confers high risk of adverse cardiovascular events. Once diagnosed, the mainstay of treatment for PAD is medical therapy, focused on the modiﬁcation of cardiovascular risk factors. Exercise therapy may substantially improve symptoms of claudication, but for the select patients who fail conservative therapy, there are a growing number of endovascular and surgical therapeutic options. Through keen understanding of clinical and anatomic features, as well as appreciation of the range of therapeutic strategies, we may tailor our approach to optimize outcomes for our patients.