Continuing Education Activity

The radial artery graft is considered the second option as a conduit after the left internal mammary graft in coronary artery bypass grafting. Multiple studies have shown better patency rate and survival with radial artery graft as compared to saphenous vein graft. This activity reviews the utility of radial artery grafts for coronary artery bypass surgery and highlights the interprofessional team's role in evaluating and treating this condition.

Objectives:

• Identify the indications for using a radial artery bypass graft.
• Describe the equipment, personnel, preparation, and technique in regards to radial artery bypass graft.
• Review the appropriate evaluation of the potential complications and their clinical significance of radial artery bypass graft.
• Outline some inter-professional team strategies for improving care coordination and communication to advance radial artery bypass graft and improve outcomes.

Introduction

The coronary artery bypass graft (CABG) surgery is the treatment of choice for severe left main and multivessel coronary artery disease.[1][2] Both arterial and venous graft combinations are commonly used in CABG. Left internal mammary graft is still the preferred conduit because of the better long-term survival rates than other bypass conduits.[3] Saphenous venous grafts (SVG), compared to arterial grafts, have a shorter overall life and have an increased tendency to degenerate and become occluded after an ischemic event. During the first year, SVG graft occlusion can occur in 10 to 15% cases, and 50% of them have significant or complete occlusion by ten years.[4][5] 

Because of the poor long term outcomes associated with SVG, other arterial conduits, including the right internal thoracic artery, right gastroepiploic artery, right inferior epigastric artery, and radial artery, came into consideration. The use of bilateral internal mammary graft has been discouraged because of its association with increased sternal infection.[6] 

The radial artery graft is easy to harvest and can be bypassed to reach the major coronary arteries; it has now gained popularity as the preferred option after the left internal mammary artery. Carpentier and his colleagues in 1973 first used the radial artery as an arterial conduit.[7] However, within a few years, its use was abandoned because of the high rate of occlusion. Acar and colleagues reintroduced it in 1992 after discovering patent radial graft on an angiogram performed in a patient 18 years post CABG, which was previously thought to be occluded.[8] 

With modification in surgical technique and utilization of antispasmodic agents, the radial artery graft patency rate is more than 90% at both one year and five years.[9] This article will review the utility of the radial artery in CABG.

Anatomy and Physiology

The brachial artery divides into two branches, ulnar and radial artery, opposite to the neck of the radius. The radial artery is smaller in diameter as compared to the ulnar artery. At the lateral side of the carpus, the artery turns backward, and underneath tendons of extensor pollicis longus and flexor pollicis longus, it runs towards the first and second metatarsal space. The artery reaches the palm of the hand while crossing between two first dorsal interosseous muscle. The radial artery makes a deep palmar arch by combining it with the superficial volar branch of the ulnar artery.

At the forearm, the radial artery branches to the recurrent radial artery. It gives off a volar carpal branch at the wrist, and at the hand, it gives superficial volar carpal branch. Histologically, the medial layer of the radial artery is mostly muscular, making it prone to spasm. The muscular segments of both the radial artery and the internal mammary artery are similar.[10] 

The radial artery is particularly prone to spasm, possibly because of its large medial cross-sectional area. Adaptation to high arterial pressure, diameter similar to coronary arteries, length suitable for all coronary arteries, and harvesting without ambulation make radial artery graft preferable to saphenous vein graft in terms of both morbidity and mortality.[11]

Indications

Graft choices for coronary artery bypass graft surgery:

According to the 2011 ACCF/AHA Guideline, indications for CABG surgery using a radial artery include the following:[12]

1. Radial artery graft to left-sided coronaries with severe stenosis (>70%) can be reasonable. [Level 2]
2. Radial artery graft to the right-sided coronaries with severe stenosis (>90%) can be reasonable. [Level 2]

Contraindications

Contraindications for CABG using radial artery graft include:

• Abnormal Allen test
• Injury to the radial artery due to trauma 
• Dissection from prior arterial cannulation
• Significant radial artery stenosis on ultrasonography
• Arteriovenous fistula for hemodialysis
• Vasculitis[13]
• Raynaud disease[14]

Equipment

The equipment required for radial artery bypass graft include:

• Operation theatre
• Cardiopulmonary machine
• Surgical drape
• Sternal saw
• Clamps
• Retractors
• Forceps
• Scissors
• Needle holder
• Dilators and dissectors
• Suction cannula
• Sutures and Needles
• Arterial cannula
• Venous cannula
• Cardioplegia cannula

Personnel

• Cardiothoracic surgeon
• Anesthesiologist
• Intervention cardiologist
• Operation theatre technician
• Anesthesia technician
• Perfusionist for cardiopulmonary bypass machine
• Staff nurse
• Nutritionist
• Physiotherapist

Preparation

The modified Allen test using pulse oximetry and plethysmography should be performed before surgery. This test helps to assess the arterial flow of the hand. For radial artery preparation, the most crucial step is to pre-medicate with vasodilators. For vasodilation, either calcium channel blockers or nitrates are used to reduce radial artery graft spasm.

Before surgery, it is essential to continue aspirin, especially in patients with acute coronary syndrome. But P2y12inhibitors such as ticagrelor and clopidogrel need to behold five days and prasugrel seven days before the procedure.[15] Antidepressants consideration before surgery helps to reduce anxiety.

In preparation for the procedure, routine tests, including complete blood count, creatinine, electrolytes, coagulation profile, liver function test, electrocardiogram, and echocardiogram, are required. The blood products, including packed cell units, fresh frozen plasma, and platelets, should be arranged before the procedure. Fasting should be started 6 hours before the procedure.

Technique or Treatment

The two most important steps to prevent radial graft failure are using the “no-touch technique” and removing the graft as a pedicle that contains the radial artery, the surrounding veins, and fatty tissue.[16][13]

The nondominant hand is prepared and draped for the procedure. An arm board is applied to avoid traction on the arm during the change in the height of the table. A curvilinear incision made extending from one finger breath distal of the biceps tendon to one finger breath proximal to the radial styloid crease.

The tissues to the deep fascia are separated with the help of diathermy. It is vital to avoid injury to the lateral cutaneous nerve, which overlies the radial artery at the distal end of the incision. Then deep fascia is separated medially to the brachioradialis muscle. This reduces injury to the radial artery side branches.  Once the brachioradialis muscle is retracted, the side branches are visible.

Neurovascular fascia lies under the brachioradialis muscle covering the radial artery and its surrounding veins. It is simple to harvest the radial artery after this fascia is separated. The radial artery pedicle dissection becomes more straightforward when it started from the middle of the forearm as the artery cross underneath the brachioradialis muscle. The radial artery carefully lifts from its muscular bed. The side branches become visible once the radial artery pedicle is lifted. Then gentle upward traction to the vessel loop is done. After that, side branches are ligated with a harmonic scalpel.

Once the radial artery is mobilized, it is prepared for the proximal and distal divisions. The distal division is done first by putting a 2.0 silk suture around the artery at the point where the radial styloid combines with the radial pedicle, followed by ligation of the distal end of the radial artery. Once a distal division is complete, the distal stump of the radial artery is palpated to assure ulnar artery contribution to the collateral supply of the hand. Then proximal division is then performed. The radial artery is carefully lifted perpendicular to the forearm. The artery is first ligated with silk 2.0 suture and then divided. The proximal end of the graft is cannulated and flushed with the papaverine. The whole radial artery graft is covered with papaverine soaked gauze and detached from the operative site.

Electrocautery is used to achieve hemostasis of the radial artery graft. Before wound closure, hand examination is performed to confirm hemostasis. It helps to reduce the risk of postoperative compartment syndrome. It is essential to close the wound before giving systemic heparin. The deep fascia is sutured with running 2-0 polyglycolic suture and the skin with running 4-0 polyglycolic suture.

Complications

Following complications can occur after radial bypass graft surgery

• Cutaneous paraesthesia secondary to damage to the lateral cutaneous nerve (most common) [17]
• severe ischemia of the hand
• infections at the graft site
• median and radial nerve injuries[18]
• Radial artery spasm (more severe as compared to internal thoracic artery aneurysm)[19]
• Left ventricle dysfunction
• Stroke
• Acute renal injury
• Cardiac tamponade
• Pulmonary infections
• Cardiac arrhythmias

Clinical Significance

The radial artery graft is considered the second option as a conduit after the left internal mammary graft. Multiple studies have shown better patency rate and survival with radial artery graft than saphenous vein graft.[20]

As compared to the right internal thoracic artery, the radial artery is not associated with increased sternal wound infection. Compared to the right gastroepiploic artery and the inferior epigastric artery, radial artery graft is usable in obese and in patients with previous abdominal surgery.

Enhancing Healthcare Team Outcomes

CABG is a mortality and morbidity saving surgical procedure in patients with severe three-vessel coronary artery disease or left main coronary artery disease. It requires a multidisciplinary approach, consisting of a cardiothoracic surgeon, cardiac anesthesia specialist, interventional cardiologist, non-interventional cardiologist, operative technician, nursing staff, pharmacist,  dietician, and physiotherapist to improve patient care.[21] 

Before the procedure, the patient should have an assessment by the cardiologist, cardiothoracic, and anesthesia teams, with a clear explanation of risks and benefits to patients. Postoperatively, patients should receive antiplatelet drugs, heart rate-controlling agents, and vasodilators, especially in patients with radial artery graft.

The radial artery graft is gaining popularity, especially in patients with contraindication of bilateral internal mammary graft. As guidelines are now emphasizing complete arterial revascularization, radial artery graft use will become more common. To improve cosmetic and clinical outcomes, minimally invasive techniques to harvest radial artery is in consideration.