Radial Artery Evaluation Before Coronary Artery Bypass Grafts



Radial Artery Evaluation Before Coronary Artery Bypass Grafts


Molly J. Zaccardi

Nahush A. Mokadam



The choice of conduit in coronary artery bypass grafting is often surgeon and institution specific. Nonetheless, the general consensus is that this choice can play a crucial role in the outcomes of patients undergoing coronary revascularization. Increased attention has been paid to the use of multiple arterial conduits for coronary artery bypass, including the left internal mammary artery, the right internal mammary artery, and the radial artery. The radial artery was first introduced in 1973 for aortocoronary bypass.1 However, initial enthusiasm faded quickly, because the radial artery was prone to premature graft occlusion and spasm. The development of pharmacologic therapy to minimize arterial spasm, along with new techniques for arterial harvest, rejuvenated interest in the radial artery as a conduit for coronary artery bypass.2 Although long-term outcomes data comparing the radial artery with the saphenous vein are fraught with bias, there is a suggestion that the use of a radial artery graft improves survival or, at the very least, is equivalent to the use of saphenous vein grafts.3,4 For these reasons, the routine and widespread use of the radial artery has not gained a major foothold in the cardiac surgery community, but it does remain a very good option in many patients.

The radial artery is one of the two end arteries supplying the hand. The ability to safely harvest the radial artery depends on adequate ulnar artery inflow and an intact palmar arch. The traditional and most simplistic evaluation of the arterial supply to the hand has been Allen’s test. However, the adequacy of Allen’s test has been questioned, leading to the practice of relying on more objective criteria to prevent hand ischemia after harvesting the radial artery.5


ROLE OF THE VASCULAR LABORATORY

When the radial artery is being considered for use as a conduit, the vascular laboratory can provide important preoperative information regarding collateral circulation to the hand and the size and patency of the radial artery to answer the key questions listed below:



  • Will the collateral circulation be adequate to ensure perfusion of the hand following removal of the radial artery?

    In most patients, the deep and superficial palmar arches of the hand provide collateral routes between the radial and the ulnar arteries and allow safe harvesting of the radial artery. The classic superficial palmar arch connects the ulnar artery and the superficial palmar branch of the radial artery. The classic deep palmar arch connects the radial artery and the deep branch of the ulnar artery (Fig. 34.1). However, cadaver studies have reported that up to 34% of hands have an incomplete deep or superficial palmar arch.6,7,8,9,10 Table 34.1 summarizes five such studies. In these cases, removal of the radial artery could lead to digital ischemia. In addition, it has been suggested that a complete arch may be present in the hand but that collateral flow might still be inadequate. Examples of complete and incomplete superficial palmar arches are demonstrated in Figure 34.2 from a report by Gellman et al.11


  • Is the radial artery size (diameter and length) adequate for use as a coronary artery bypass graft?

    Ideally, the length of the radial artery conduit should be sufficient to reach from the aorta to the lateral wall of the heart (15 to 18 cm) for an obtuse marginal bypass. The diameter should be at least 2 mm, but preferably larger. The cadaver study of Gellman et al11 reported radial artery lumen diameters ranging from 2.3 to 5 mm, with an average of approximately 2.6 mm. Anatomic variants such as ulnar artery dominance may be associated with a smaller radial artery diameter. Early or late bifurcations can also reduce the usable length of the radial artery. In a study of 192 cadavers (384 arms), Rodriguez-Niedenfuhr et al12 found anatomic variants in 24% of the upper arm (brachial) arteries and 19% of the forearm (radial and/or ulnar) arteries. A summary of this report is presented in Table 34.2.


  • Is the radial artery obstructed or calcified?

    Stenosis or calcification of the radial artery can reduce the long-term patency of a coronary artery bypass graft. These abnormalities are common in this patient population, as noted by Ruengsakulrach et al.13 These authors examined 73 patients preoperatively with ultrasound and found an overall 31.5% incidence of radial artery calcification or echogenic plaques.







FIGURE 34.1. Normal anatomy of the forearm and hand arteries, including the deep and superficial palmar arches of the hand.








TABLE 34.1 PREVALENCE OF INCOMPLETE SUPERFICIAL AND DEEP PALMAR ARCHES FROM CADAVER STUDIES

▪ NUMBER OF CADAVER HANDS

▪ INCOMPLETE SUPERFICIAL PALMAR ARCH (%)

▪ INCOMPLETE DEEP PALMAR ARCH (%)


Coleman and Anson (1961)7

650

21.5

3


Ikeda et al (1988)8

220

3.6

23.1


Mezzogiorno et al (1994)9

60

—

33.3


Orzkus et al (1998)10

80

20

—


Ruengsakulrach et al (2001)6

50

34

10







FIGURE 34.2. Examples of variations of the superficial palmar arch. (From Gellman H, Botte MJ, Shankweiler J, et al. Arterial patterns of the deep and superficial palmar arches. Clin Orthop 2001;383:41-46, used with permission.)









TABLE 34.2 SUMMARY OF ANATOMICAL VARIANTS FOUND IN A CADAVER STUDY OF 384 LIMBS

▪ ARTERIAL PATTERNS

▪ DESCRIPTION

▪ INCIDENCE


Arm


1 artery

Brachial (Normal)


76.06%

Superficial brachial

Brachial artery is superficial to the nerve

4.9


2 arteries

Brachial and accessory brachial

Brachial artery branches in the upper arm and rejoins above the elbow

0.26

Brachial and brachioradial

Radial artery with high origin

13.8

Brachial and superficial brachioradial

Radial with high origin and superficial to the nerve

<0.26

Brachial and brachioulnar

Ulnar artery with a high origin

0.26

Brachial and superficial brachioulnar

Ulnar with high origin and superficial to the nerve

4.2

Brachial and superficial brachioulnoradial

Brachial has radial and ulnar branches but continues into interosseus

0.52

Brachial and superficial brachiomedian

High origin of the median artery, which is superficial to muscles

<0.26

Brachial and brachiointerosseus

High origin of the interosseus artery coexisting with brachial artery

<0.26


Forearm


1 artery

Ulnar and radial absent


<0.26

Radial and ulnar absent


<0.26


2 arteries

Ulnar and radial (Normal)


81.22%

Ulnar and brachioradial

High origin of the radial artery

13.8

Ulnar and superficial brachioradial

High origin of the radial artery and superficial to muscle/tendons

<0.26

Ulnar and superficial radial

Radial artery superficial to muscle

0.52

Radial and brachioulnar

High origin of the ulnar artery

0.26

Radial and superficial brachioulnar

Ulnar has a high origin and is superficial to muscle

4.2

3 arteries

Ulnar and radial and brachiomedian

High origin of the median artery

<0.26

Ulnar, radial, and superficial brachioradial

Radial duplication

<0.26

Radial, ulnar, and superficial brachioulnar

Ulnar duplication

<0.26


Adapted from Rodriguez-Niedenfuhr M, Vazquez T, Nearn L, et al. Variations of the arterial pattern in the upper limb revisited: A morphological and statistical study, with a review of the literature. J Anat 2001;199:547-566.


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Sep 23, 2016 | Posted by in CARDIOLOGY | Comments Off on Radial Artery Evaluation Before Coronary Artery Bypass Grafts

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