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The radial artery in coronary surgery, 2018

  • James Tatoulis
REVIEW ARTICLE
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Abstract

It is now 25 years since the radial artery (RA) was reintroduced in coronary surgery. It has evolved into being a significant coronary artery bypass conduit and ranks third in usage after the internal thoracic artery (ITA) and saphenous vein grafts (SVG). Its advantages are that it can be readily and efficiently harvested, is of good length and appropriate size for coronary artery bypass graft (CABG) surgery, is robust and easy to handle, and remains free of atheroma, and there is minimal wound morbidity. The RA must be used judiciously with attention to spasm prophylaxis because of its muscular wall, and by avoiding competitive flow. Its patency is equivalent to the ITAs when placed to similar coronary territories and under similar conditions (stenosis, size, quality) and RA patencies are always superior to those of SVG in both observational and randomized studies—88–90% versus 50–60% at 10 years, and 80–87% versus 25–40% at 20 years. Its use and excellent patencies result in survival results equivalent to bilateral internal thoracic artery (BITA) grafting and always superior to left internal thoracic artery (LITA) +SVG. Typical radial artery multiarterial bypass grafting (RA-MABG) 10-year survivals are 80–90% versus 70–80% for LITA-SVG. In general, for every 100 patients undergoing CABG, 10 more patients will be alive at 10 years post-operatively. The RA also is important in achieving total arterial revascularization, and several reports indicate a further survival advantage for patients having three arterial grafts over two. The RAs are especially useful in diabetic, morbidly obese patients, those with conduit shortage, and leg pathology, and in coronary reoperations. Although the RA has equivalent patencies to the right internal thoracic artery (RITA), it is much more versatile. RAs that have been instrumented by angiography or percutaneous coronary intervention should be avoided. The radial artery has proved to be an excellent arterial conduit, is equivalent to but more versatile than the RITA, and is always superior to SVG. Its use should be part of every coronary surgeon’s skill set.

Keywords

Coronary artery bypass Radial artery Arterial grafting 

Introduction

The RA is a versatile and an extremely useful conduit in coronary surgery. It is long, robust, easy to handle, and of an appropriate size, and there are two.

It is used in an identical fashion to a SVG. Moreover, the forearm incisions heal well and rapidly—as distinct from leg incisions. There is a lower chance of infection and ambulation is much more rapid—especially relevant in older patients.

It was first used by Carpentier in 1971, in 30 patients (40 RA grafts), and reported in 1973. The initial clinical results were satisfactory, however, within 2 years 32% of the grafts appeared to be occluded and a further number had severe stenoses within them. Hence, the RA was abandoned. Although spasm was recognized at the time, it was managed by mechanical dilatation. There were no modern smooth muscle relaxing drugs available, and nitroglycerine was not routinely used [1].

Twenty years later, Acar unexpectedly noted good long-term results from this early group of patients. A number of the earlier “occluded” grafts were now found to be widely patent [2].

This stimulated renewed interest in the RA, and its application gradually became more widespread. Although the RA is not widely used, currently in an increasing number of centers, it is now the second or third graft of choice after the LITA and the RITA.

The RA appears to be resistant to atherosclerosis, and has better long-term patency than SVG, and in turn is associated with better long-term results (over 10 years). In many centers, it is a significant component of total arterial revascularization [3].

Rationale for RA use as a coronary conduit

The internal thoracic arteries (ITAs) are the best conduit(s) for coronary surgery. The use of and the results associated with the RITA are compromised by its use to less conducive vessels (circumflex marginal and posterior descending).

Irrespective of which conduit is used, there is a hierarchy of patency. Patency to the left anterior descending (LAD) is best followed by the circumflex marginal (CxOM), and finally the distal right coronary (RCA) distribution. Additionally, RITA patency is influenced by more complex techniques including passage through the transverse sinus, LITA/RITA Y composite grafts, multiple sequential anastomoses, and direct proximal anastomoses to the aorta in Free RITA grafts.

Patency of SVGs, even in the modern era, is disappointing despite statins and newer antiplatelet drugs, with SVG occlusion rates of up to 10% at 1 week [4], 25% at 1 year [5], and 50–60% at 10 years [6]. Those SVGs still patent beyond 10 years are also heavily affected by atheroma. Reduced SVG patencies frequently result in recurrent angina, myocardial infarction, re-hospitalization, and further interventions by percutaneous coronary intervention (PCI) or redo CABG, and reduced long-term survival [3, 6, 7].

Hence, the RA is an appealing alternate conduit as there are two. It is superficial, is accessible, can be readily harvested, and can be used in a similar fashion to SVG. As an arterial graft, it has the potential to overcome the limitations posed by SVG, providing care is taken in its harvest, deployment, and perioperative management.

Its use is also particularly attractive when SVG is not available (prior surgery, varicose veins, leg pathology) and in reoperations where it would not be logical to use further SVG, as presumably the best SVG conduits have already failed, and any SVG remaining would be of inferior quality to that used in the first operation, also in patients with severe obstructive airway disease, morbid obesity, particularly with insulin dependent diabetes—situations which generally preclude the use of bilateral ITAs (BITA).

Anatomy

The RA runs from the elbow, just medial to the biceps tendon, accompanied on either side by venae comitantes, coursing between the brachioradialis muscle laterally, and the flexor muscles medially, initially in loose areolar tissue. It becomes superficial in the lower third of the forearm, covered by skin and subcutaneous tissue.

Branches are few proximally—located either laterally, medially, or on the deep aspect, and become more numerous towards the wrist.

Beyond the wrist, the radial artery contributes to the superficial and deep palmar arteries and establishes continuity with the distal ulnar artery.

Generally (> 95%), the ulnar artery is dominant which allows the RA to be harvested without compromising the forearm or hand vascularity or function.

The lateral cutaneous nerve and the superficial radial nerve, both sensory nerves, run parallel and lateral to the RA and should be identified, (in an open technique) and avoided. Trauma to these nerves during harvest will inevitably lead to sensory abnormality in the base of the thumb but fortunately it mainly resolves within 3 months.

There are a number of anatomic variations, but fortunately they are rare. However, it is important to be mindful of these—the most common being an early large lateral terminal branch, which if present should be preserved—thus, inevitably resulting in a shorter length of RA available for harvest [3, 6].

Histology

The RA is a muscular walled artery. Its wall thickness is 2–3 times greater than the ITA. The RA has more intimal changes and a 5% incidence of significant medial calcification by comparison to the ITA in the same patient. Diabetes, peripheral vascular disease, male gender, and age are associated with an increase in RA wall pathology [8].

The mean distal RA diameter is 2.2 mm by comparison to the ITA (2.0 mm).

Proximal RA diameter is a mean of 3.5 mm—similar to SVG from the lower leg [3, 6, 8].

Pharmacology and physiology

As a consequence of the relatively thick smooth muscle media, the RA is exquisitely sensitive to mechanical, cold and pharmacologic stimulation with resulting intense vasoconstriction and spasm. Extensive laboratory studies have shown potent contractile responses to vasoconstrictors such as norepinephrine, thromboxane A2, and medically used vasoconstrictors, metaraminol, and vasopressin. In general, the RA contractor response is twice that of the ITA [9].

Conversely, the RA responds well to vasodilators that include papaverine, nitroglycerine, nitroprusside, phenoxybenzamine, milrinone, and diltiazem [9].

Intraoperative spasm prophylaxis is essential. In our (and many other) practice, we achieve this by atraumatic no-touch RA harvest, intraluminal injection (with a 1-mm-bulb-tipped cannula) of 3 ml papaverine solution in warm arterial blood (30 mg in 30 ml), clipping the distal end and letting the RA beat against the occluded distal end in situ for 5 min before disconnecting it proximally, and storing the RA in an identical solution until use [3, 6, 10].

We also use intra- and perioperative nitroglycerine infusion for 24 h, and once in a day calcium channel blocker, and amlodipine for 6 months—empirically, based on observations of isolated areas of RA spasm which instantly resolved with intragraft nitroglycerine, in some angiograms up to 3 months post-operatively [3, 6, 10].

The RA in the coronary circulation is a “living graft” and may vasoconstrict to a “string sign” in situations of competitive flow, and conversely may significantly enlarge in diameter in a high-flow milieu. As a consequence, it should be preferably used to target vessels with a high degree stenosis, preferably when the most stenotic segment is < 1-mm diameter or where there is total occlusion. Moderately, stenosed-dominant RCA scenarios are generally inappropriate for RA and these can be managed by either leaving the moderately stenotic RCA alone unless there is a compelling fractional flow reserve (FFR) measurement, or by stenting or SVG depending on the patient’s age and clinical situation [2, 3, 9, 10].

Surgical strategy and deployment

The RA is used either as the second graft (after LITA) or third graft (after bilateral ITAs).

In younger patients (< 70 years), we and other groups prefer BITAs and supplement these with an RA if necessary and appropriate [11, 12].

In older patients (> 70), we routinely use the LITA to the LAD, and RA to the next most important vessel, and then a second RA or an SVG to other graftable vessels [3, 6, 10].

As noted earlier, moderate stenosis in the RCA may be managed by a number of options (medical management, PCI, or SVG) depending on the patient’s circumstances.

RA should be avoided in collagen diseases such as scleroderma, where there is Raynaud’s disease, or an extremely cold climate [3, 10].

It can be efficiently harvested concurrently with the LITA. Bilateral RA harvest in general is performed prior to ITA harvest, unless there are 3 operators [10].

The RA should be used in an identical manner as for SVG. The majority are used as aortocoronary grafts, predominantly 1:1, or in a sequential fashion depending on the revascularization requirements in the circumflex and or distal right coronary systems. The sequential anastomoses are constructed in a manner to accommodate the best lie (using the same principles and techniques as one would with other sequential grafts).

If possible, the terminal anastomosis should be to a relatively large vessel with a tight stenosis [13, 14].

Excellent patency and clinical results have been reported in both single and sequential RA grafting [2, 3, 7, 13, 14]. These are discussed in detail later.

LITA-RA Y grafts are also commonly used [7, 14]. They are especially useful for anaortic off-pump coronary artery bypass (OPCAB). The “inlet” anastomosis should be a Y rather than a T, performed at the level of the second intercostal branch of the LITA to allow the best lie and entry into the pericardium. Such a construction should be avoided if the LITA is small (< 2 mm). This technique is also useful when there is a conduit shortage. Patency reports are varied—from excellent [2, 3, 6] to satisfactory—with some authors reporting a 25% attrition rate of the last segment of the RA [14].

“Baby Y” composite RA grafts when the anatomy is unfavorable for sequential grafting, e.g., a more distal stenosis in the first circumflex marginal. The baby Y technique allows anastomosis in the most ideal segment of each target vessel, without being dictated by the lie or length of a sequential graft. The main/primary graft may pass to either the proximal or distal target and a short “baby” 3–5-cm segment can be connected to the primary RA graft.

RITA-RA extension grafts are used, especially in anaortic OPCAB, to supplement the LITA-LAD and can reach any other coronary targets [15].

An inverted T graft is where an aortocoronary segment, i.e., SVG or RA, is connected end to side to the central portion of an RA conduit with flow passing both superiorly and inferiorly through the RA, as it has no valves, to appropriate targets, especially on the left side [16].

Although the RA patency data predominantly relate to on-pump CABG with single RA grafts, clinical data across the range of RA use strategies are similar and uniformly very good to excellent (discussed later).

Radial artery harvest

Adequate hand circulation must be always assessed. The clinical Allen’s test is the simplest and reliable. Return of hand circulation within 10 s of releasing the ulnar is satisfactory.

This can be better and more objectively demonstrated by adding a plethysmograph to the index finger, and documenting the return of the arterial wave on releasing ulnar artery [3, 6, 10].

Ultrasound can assess the size of the RA and any pathology/wall calcification, if there is doubt about its potential suitability.

The right RA is now commonly used for angiography and PCI, and should be avoided if possible. Significant radiologic and histologic changes have been noted following such procedures which may impact on long-term patency. If the instrumented RA must be used (conduit shortage), then most authors recommend delaying this for 3 months if possible [17, 18].

RA harvest can be either open, or closed, with endoscopic and harmonic scalpel technology [19, 20]. Most RA patency data relates to open harvest, and the more recent clinical data is reported from “endoharvest” cohorts. There does not appear to be a long-term clinical advantage of one technology over the other. Endoharvest is best by experienced, dedicated operators and perhaps is not suitable where the assistants are transient (teaching hospitals).

RA wound problems are rare. The most common problem is dysfunction of the lateral cutaneous nerve of the forearm and superficial radial nerve causing thenar discomfort and paresthesia for 3–6 months. Hand function is not compromised by RA harvest and there is ultrasound evidence of compensatory enlargement and vascularity of the ulnar artery.

Technical

The distal anastomoses, whether end to side or side to side are constructed with either 7.0 or 8.0 polypropylene, identically to the techniques used for SVG or ITA (Fig. 1).
Fig. 1

RA ready for anastomosis to the posterior descending artery (PDA). RA hood approximately 25% larger

The proximal RA anastomosis to the aorta is preferably performed during a single period of cross clamping with free and easy access to almost the entire ascending thoracic aorta or by using a proximal anastomotic device in OPCAB if the “inlet” is to be from the aorta rather than an ITA.

For smaller RAs (< 3-mm proximal diameter) a 2.5- or 2.7-mm aortic punch is used, for larger (more common) RAs (proximal diameter > 3 mm), a 3.5-mm aortic punch. The RA hood should be at least 25% larger than the punched opening to ensure a wide, patulous inlet anastomosis. This is constructed in an identical manner as for SVG [3, 6, 10].

Graft to graft anastomoses (discussed above) are usually constructed with continuous 7.0 polypropylene.

Results

Multiple publications where the RA has been used in CABG document the perioperative (including 30 day) mortality to be 1–2%, depending on patients’ age, clinical circumstances, comorbidities, etc. [2, 3, 6, 7, 12, 14, 15].

Other major morbidities, i.e., perioperative myocardial infarction, stroke, post-operative hemorrhage, and sternal wound infections, are also infrequent and identical to conventional surgery with an LITA and SVG.

Significantly, where the RA is used in conjunction with ITAs in anaortic OPCAB, the incidence of stroke is < 1%, even in 70- and 80-year-olds [15].

The longer term patency and clinical results are discussed below.

Patency

Observational studies

Many observational studies have been reported. Results before 10 years are confounded by different techniques and applications of available conduits. It takes 7 years to begin to see a divergence of conduit patency favoring arterial grafts, including the RA, over SVG.

Apart from 1 study [21], all others where angiography has been driven by symptoms have shown excellent RA patencies of, 90–95% in the first 5 years, 89–92% at 9 to 10 years, and 86% at 20 years [2, 3, 6, 22, 23, 24]. In over 1000 post-operative RA angiograms we found 10-year patency to be 89%. Moreover, patency within the yearly cohorts studied remained at 90% [3]. Gaudino et al. have published 20-year RA patency of 87%, identical to the ITAs in their series [23].

Importantly, all RA grafts reported as patent in the long term are uniform and free of atheroma, unlike SVG. Typical RA long-term angiograms are shown in (Figs. 2, 3, 4, 5, 6, and 7).
Fig. 2

RA to the PDA. Ten years post-operatively

Fig. 3

RA to the PDA. Twelve years post-operatively

Fig. 4

RA to the circumflex marginal (OM) 12 years post-operatively. Same patient as in Fig. 3. Smooth lumen in each with no suggestion of atheroma

Fig. 5

RA sequential to mid and inferior OM. Fifteen years post-operatively

Fig. 6

“Baby Y” RA composite grafts to the diagonal (diag) and OM arteries

Fig. 7

RA from the descending thoracic aorta to the OM. Eight years post-operatively

RA graft failure is an early phenomenon and is either technical, due to localized trauma, or unrecognized wall disease, or as a result of competitive flow [3, 13, 14]. Once an RA graft is in situ and functioning well, it remains free of atheroma and remains patent in the long term [2, 3, 22, 23, 24]. In addition, there is a remodeling of the wall of the RA conduit that transforms it from a muscular to an “elastomuscular” vessel, more closely simulating the wall structure of the ITA [25].

An additional benefit that possibly impacts patency and long term clinical efficacy is that the RA (as with other arterial grafts) synthesizes and releases nitric oxide, and other favorable vasoactive substances, that protect the coronary artery downstream from the anastomosis from development of new atheromatous plaque [26]. This may be one of the mechanisms whereby diabetic patients not only do better with CABG over PCI, but do even better with total arterial revascularization in which RA conduits are a major feature in some series [27].

Randomized controlled trials

Three large randomized controlled trials of RA versus SVG have reported patency results beyond 5 years, and all showed superior patency for the RA over SVG.

The British Radial Artery versus Saphenous Vein Patency (RSVP) study reported 92% RA patency versus 78% for SVG at 5 years [28].

The Canadian Radial Artery Patency Study (RAPS) showed 88% RA patency at 7.7 years [29].

The Australian Radial Artery Patency and Clinical Outcomes (RAPCO) RCT also reported superior patency for the RA over the SVG at 5 years, 90% versus 82%, and also at 10 years, 86% versus 75% [30].

Of note, in the RAPCO study the comparison between RA and SVG was 1:1, as the second graft, to the second most important target vessel (after LITA-LAD). The trial conduit was harvested and grafted by the attending surgeon. Despite the SVG being the best possible venous conduit (usually from the lower leg, uniform size, no branches and no valves), the patency (and clinical) results favored RA.

A comprehensive meta-analysis of RCTs of RA versus SVG patency by Cao et al. showed a marked patency benefit for RA—89.9 vs 63.1% (p < 0.0001). SVG were 2–3 times more likely to fail [31, 32].

The RAPCO study was the only RCT to compare the RA to RITA. This was in patients < 70 years. The randomization was RA or free RITA (to ensure valid comparison as an aortocoronary graft) as the second conduit to the second most important artery. The outcomes at 5 and 10 years—for both patency and clinical—slightly favored the RA but there were no statistical differences. Patency rates at 10 years were 88%.

In general RA patency is similar or identical to that of LITA or RITA grafts, (and always better than for SVG) when placed to the same arteries, under the same conditions:95% to the LAD, 92% to the circumflex marginal, and 88% to the posterior descending coronary arteries [6, 23].

It has been argued that contemporary SVG patency is superior to prior eras, as a result of better harvesting, preservation techniques, dual antiplatelet therapy and statins. However, this is not necessarily the case as recent observational studies and RCTs of SVG have reported SVG failure rates of up to 12% at 1 week, 25% at 1 year, and 50% at 10 years [4, 5, 6].

Clinical results

In addition to graft patency, long-term prognosis following CABG is influenced by age, comorbidities such as diabetes, renal disease, hypertension, other cardiovascular disease and importantly, the degree of left ventricular dysfunction and the number of arterial grafts, or conversely the number of venous grafts. The published reports universally show better long-term outcomes—fewer major adverse cardiac events (MACE), myocardial infarctions (MI), less recurrent angina, and fewer interventions and repeat revascularization in patients that have multiple arterial grafts which include the RA. Additionally, most also document superior long-term survival, especially beyond 10 years.

Long-term survival with RA-MABG is reported in the range of 90–94% at 5 years, 85–90% at 10 years, and 67–75% at 15 years by comparison to the traditional single arterial graft plus SVG (70–75% at 10 years, 60–70% at 15 years). Overall, for every 100 patients undergoing CABG, 10 more will be alive 10 years post-operatively if they had multiple arterial grafts including radial artery [12, 27, 32].

The long-term clinical results will be considered in the context of RA versus SVG as a second graft, RA versus RITA as a second graft, radial artery in multi-arterial bypass grafting, and in total arterial revascularization (TAR), as well as in specific patient subgroups—the elderly, gender, and diabetes.

Radial artery versus saphenous vein as the second graft

Early clinical results are similar. Patient survival for RA-MABG at 5 years is 90–95%. Survival curves begin to diverge at the seventh post-operative year. 10-year survival reports show a marked advantage for RA- MABG over LITA-SVG; 85–90% at 10 years opposed to 70–75%. In a typical report Habib et al. documented a 9-year propensity-matched survival of 89% for RA-MABG versus 69% for LITA-SVG [32]. Grau et al. found a similar survival of 92% at 10 years [33]. This is in keeping with many other experiences.

Recent large population studies with RA-MABG from California (n = 5813), Melbourne (n = 9935), and Canada (n = 5580) reported 89.5, 87, and 74% at 7-, 10-, and 15-year survivals respectively [34, 35, 36].

Additionally, there are no leg wound infections and RA harvest site infections are rare. Procurement of SVG (predominantly thigh vein) by endoscopic techniques has revolutionized and minimized lower limb infection and hematoma but unfortunately SVG so procured show even poorer patency and inferior clinical results than those obtained by open harvest and when used in OPCAB [5].

Newer concepts in SVG use including harvest with its fat pedicle, LITA-SVG Y grafts, and external flexible splinting appear to show favorable short- to medium-term SVG patencies [37, 38, 39].

Radial artery versus RITA as the second graft

Survival at 10 years and beyond is similar when either the RA or RITA is used as a second graft to the second most important coronary artery. A recent meta-analysis by Benedetto and colleagues of 8 propensity score-matched survival studies with almost 3000 matched pairs favored RITA for overall survival. However, RITA was associated with a higher perioperative mortality and sternal wound infection [40]. Navia found a non-significant survival benefit for BITA-MABG over RA-MABG, 88 vs 83% at 7 years [41].

Conversely, other reports by Tranbaugh et al. show an advantage for RA [42]. The 10-year results of the RAPCO RCT (RA versus free RITA for the second most important coronary in patients < 70 years) showed a marginal non-significant benefit for RA over RITA [30], and yet others show equipoise between the RA and RITA [43].

The reported differences may depend on technique, incorporation of early learning experiences for either group, and the time taken to appreciate important outcome determining characteristics of each graft—sternal blood supply, skeletonization for the RITA, spasm, and competitive flow for the RA. RITA grafts are influenced less by competitive flow than RA [3, 6, 9, 11, 44].

Skeletonized RITA grafts significantly reduce sternal wound infection and dehiscence, and display vasodilatation, extra length, versatility, and are less affected by competitive flow. Conversely, RA grafts are almost always longer, can be harvested more efficiently with the LITA and the harvest does not contribute to wound infections [45].

Hence, RA grafts have a vast potential use in diabetic patients, those with severe chronic obstructive airways disease (COAD), in conduit shortage (e.g., reoperation), and where there is leg pathology.

In general, 10-year survival is between 85 and 90% for either group [11, 12, 23, 35, 40, 42, 43].

Current guidelines recommend either RA or RITA as the second arterial graft in appropriate patients [46].

Table 1 summarizes patency and survival outcomes for the different conduits and grafting strategies.
Table 1

Summary of patency and survival from randomized controlled trials, large propensity-matched series and meta-analysis

 

5 years (%)

10 years (%)

15 years (%)

20 years (%)

Patency

 RITA

90–95

90–92

85–90

85–90

 RA

90–94

85–90

85–90

80–87

 SVG

65–80

50–70

30–50

25–40

Survival

 BITA

90–95

85–88

70–75

45–65

 RA-MABG

88–95

80–89

70–75

 

 LITA-SVG

85–92

60–80

55–65

30–50

Details are to be found in the text. Ranges account for variations in reported studies, for era, mean age at the time of surgery, comorbidities and length of follow-up. No reliable 20-year survival figures for RA-MABG available

There is also evidence showing that higher risk subgroups of patients, the elderly, diabetics, and females may benefit from RA grafting.

Clinical outcomes—specific subgroups

Diabetes

The incidence of diabetes is progressively increasing worldwide, especially in the coronary artery disease population. Forty-seven percent of CABG patients in the STS database have diabetes [47].

The “FREEDOM” RCT showed superior survival for CABG over PCI for diabetic patients with multivessel coronary artery disease (CAD) [48]. Diabetics undergoing CABG have a lesser survival than non-diabetics, and insulin dependent patients are even more compromised. Many groups have now shown that multiarterial bypass grafting (MABG) or total arterial (TAR) that includes the RA results in even better survival in CABG than for just LITA-SVG. Recent large studies of diabetic patients include those from Deb and colleagues from Canada [49], Raza and colleagues [50], Schwann and coworkers from the USA [51], and Tatoulis et al. from Australia [27]. All showed RA-MABG survival benefit of 80–85% versus 65–75% for LITA-SVG at10 years.

In a comprehensive study, Fremes (RAPS Trial) showed RA patency of 91.5% versus 75% for SVG at 7.7 years (p = 0.004). The difference was similar in both diabetic and non-diabetic patients and reinforces RA use in diabetics, especially to target vessels with high-grade stenoses. Diabetes did not impact RA patency [49]. Raza also documented equivalent long-term survival in diabetics whether they had BITA-MABG or RA-MABG [50].

Hence, the use of RA in this group can be strongly recommended as it mitigates against deep sternal wound infection (as opposed to pedicled BITA) and leg wound problems yet with equivalent results to BITA and superior to LITA-SVG.

The elderly

As the population ages, including those having CABG, the impact of arterial grafting and use of the RA is important. In developed countries, a 70-year-old has a further life expectancy of 15–17 years. Hence, durable revascularization, in the elderly (> 70 years) and very elderly (> 80 years) is relevant. A number of studies have now shown that older patients, even octogenarians benefit from MABG, the main form being LITA-RA.

10-year survival in septuagenarians favors LITA-RA over LITA + SVG, 70% versus 52% (p < 0.001) and similarly in those over 80 years, 60% versus 40% (p = 0.03) [52].

In another large study of 507 matched elderly pairs (mean age 71 years) from Melbourne, 10-year survival favored LITA + RA over LITA + SVG—68% versus 52% (p = 0.008) [53].

Anaortic RA-MABG OPCAB in those over 70 and 80 years can be performed with low operative mortality, and importantly perioperative stroke rates of < 1% [15].

Gender

10-year survival, in propensity-matched studies of males receiving RA-MABG versus LITA + SVG, showed benefit for RA—83% versus 73% (p < 0.001) [54] Similar reports of RA-MABG show benefit also for females [55]. However, some studies of RA-MABG showed improved survival predominantly in men [56]. Again, broadly, irrespective of gender, for every 100 patients undergoing CABG, approximately 10 more will be alive at 10 years post-operatively.

Obesity

Morbidly obese patients are prone to higher rates of sternal wound infections if BITA is used—in addition to other potential wound problems. These result in prolonged hospital stays, multiple procedures, and suboptimal outcomes. Development of mediastinitis can be catastrophic. There are no major studies comparing RA-MABG versus BITA-MABG in this group, however, it is intuitive that RA use mitigates against sternal infection while maintaining the benefits of multiple arterial grafting, and furthermore avoiding leg incisions and potential morbidity.

Chronic obstructive airways disease

There are no good quality comparative studies of CABG in COAD to inform practice.

BITA CABG is contraindicated in severe COAD, to avoid sternal dehiscence and pulmonary complications. Given RA-MABG has been shown to be superior to LITA + SVG, the use of the RA as a supplementary graft to the LITA is logical.

Renal dysfunction

There are reports of superior long-term results when BITA is used in patients with significant renal disease [57] without compromising perioperative outcomes. However, there is no major study of RA-MABG in this group to guide strategy. One would need to be cognizant of the need for arterial–venous fistulae in the forearm for hemodialysis in the future.

Other scenarios of RA-MABG

The RA (or both) is especially useful in re-operative CABG. Although this is not as common, if it is required, significant lengths and usually the best quality SVG has already been used in the first operation and failed. It would not seem logical to use any remaining SVG, which would be of secondary quality. The RAs are important conduits in this setting, and extensive revascularization can be performed, often resulting in TAR (prior LITA plus two new RAs). The perioperative and long-term results of RA-MABG in redo CABG are excellent [58, 59].

The RA can also be used from the descending thoracic aorta to the circumflex system via a left thoracotomy OPCAB approach in redo surgery where a repeat sternotomy should be avoided (prior mediastinitis) or where it may be meddlesome (prior BITA grafts) (Fig. 7).

All CABG provide better survival than PCI in patients with significant left ventricular dysfunction or heart failure. Furthermore, RA-MABG in this group can be achieved with excellent perioperative outcomes but with a superior long-term survival by comparison to LITA-SVG [60, 61].

Where there is conduit shortage, severe varicose veins, peripheral edema, leg ulcers, lower limb venous thrombosis, peripheral vascular disease, and severe recurrent cellulitis, procurement of good quality SVG may not be possible or even contraindicated. In such patients, both RAs are usually available, can be readily harvested, usually good to excellent quality, and allow myocardial revascularization which might otherwise have not been possible [10].

Skeletonization of the RA allows further dilatation, and often achieves a further 2–3 cm in length. Some workers do this routinely to enhance its versatility, whereas others use this technique selectively to increase the length of a potentially short conduit, by removal of the accompanying venae comitantes.

The radial artery as a third arterial conduit

Evidence is evolving that the greater number of arterial grafts, the better the long-term survival (> 10 years) without compromising the currently enjoyed excellent perioperative results.

TAR achieved with BITA plus RA results in better survival. Grau noted better outcomes at 12 years for BITA + RA over BITA + SVG, 92 vs 87% [33]. Shi et al. also reported better survival in propensity-matched cohorts, 90 vs 81% at 10 years and 82 vs 72% at 15 years [62].

A recent large meta-analysis of 8 propensity score-matched series (> 10,000 patients) documented that three arterial grafts (RA as the third graft in the majority) show survival benefit of 24% over 6.5 years (hazard ratio 0.76, p < 0.001) for three arterial grafts over two [63].

In the arterial revascularization trial (ART), Taggart found that an additional RA (rather than SVG) to either LITA or BITA lowered the risk of MACE over 5 years [64].

The RA is an important component in achieving total arterial revascularization.

Radial artery use after transradial catheterization

The RA is being increasingly used for diagnostic angiography and PCI, particularly in acute coronary syndrome as this procedure is associated with a lower morbidity, especially vascular access site complications and transfusion. Deleterious effects include distal occlusion of the RA in 5–8% and intimal trauma which may compromise RA graft patency if it is subsequently used as a coronary conduit. The pharmaco-physiologic responses especially to dilatation may also be compromised by RA instrumentation [17, 18, 65].

The use of instrumented RA, hence, is problematic and a number of authors recommend not using such an RA within 3 months of PCI. Others avoid it all together unless absolutely necessary because of conduit shortage and in that context would avoid using the most distal 3–5 cm if possible. Fortunately, this dilemma arises rarely, as the right RA is used for PCI, whereas the left is most commonly used in CABG [17].

Conclusion

The radial artery is an important and extremely versatile coronary conduit.

Its long-term patency is identical to the ITAs when used in the same context, and significantly superior to SVG. These excellent patencies translate to superior long-term survivals. It can be used in routine CABG, and is of special use in diabetics, reoperations, conduit shortage, and in avoiding pathologic lower limbs. Perioperative spasm prophylaxis is essential, and competitive flow must be avoided. Once in situ and functioning normally, it remains smooth and free of atheroma and patent in the long term. It should be part of every coronary surgeon’s skill set and its use be expanded.

Notes

Compliance with ethical standards

Conflict of interest

The author declares that he has no conflict of interest.

Ethical

No animal research was involved. All human patient information is de-identified. All procedures performed in the patients were routine therapeutic coronary artery bypass graft operations, and all the reviewed studies had been previously published in the literature. The original studies had institutional research committee approvals which ensure appropriate ethical standards. This article is a review of previously published studies in the literature, and does not relate to any new information not previously published.

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Copyright information

© Indian Association of Cardiovascular-Thoracic Surgeons 2018

Authors and Affiliations

  1. 1.Royal Melbourne HospitalMelbourneAustralia
  2. 2.University of MelbourneMelbourneAustralia

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