Radial Artery Graft for Coronary Artery Bypass Surgery: Biological Characteristics and Clinical Outcome

Effect of Vasodilatory Medications on Blood Pressure in Patients Undergoing Transradial Coronary Angiography: A Comparative Study

Background:

In patients undergoing coronary intervention, different vasodilators are used to prevent the radial artery spasm (RAS). To date, no studies investigated the effect of these vasodilators in blood pressure (BP) reduction.

Aim:

The study aimed to investigate and compare the effect of vasodilatory medications on BP reduction in patients undergoing transradial coronary angiography procedure.

Methods:

We consecutively included 300 patients undergoing transradial coronary angiography procedures and randomly assigned them into three equal groups to compare the effect of verapamil (2.5 mg), nitroglycerin (200 μg), and combination (verapamil 2.5 mg with nitroglycerin 200 (μg) was diluted in 5 ml of normal saline and given through radial sheath. Changes in the BP, heart rate (HR), and other clinical parameters were assessed and presented as standardized mean differences (SMD) with 95% confidence intervals (CIs). ANOVA test was performed to analyze the differences in the BP and other clinical parameters between the three groups.

Results:

Overall, the mean age of the study population was 53.26 years (standard deviation: 9.27), male patients (84%), with dyslipidemia (62.6%), and diabetes (45%). At baseline, the mean systolic BP (SBP) was 150.91 ± 31.66 mmHg, HR (72.34 ± 12.71 beats/min). After the administration of vasodilators, the combination group reduced SBP significantly (SMD: −33.35 [95% CI]: −40.27–−26.42, P < 0.001). There was a statistically significant difference between groups for the SBP (F [2,296] =3.38, P = 0.035). Verapamil alone showed a significant decrease in the SBP by −27.23 mmHg and diastolic BP by −4.980 mmHg.

Conclusion:

Intra-arterial administration of verapamil alone showed lower BP reduction compared to the combination of vasodilators. Verapamil could be a safer and effective alternative to prevent RAS with no deleterious effect on BP and HR in patients undergoing transradial coronary angiography.

A systematic review of isolated radial artery harvesting as a conduit for lower limb bypass grafting

BACKGROUND

Whilst autologous vein conduits have been heralded as the first-line approach for patients undergoing lower limb bypass grafting procedures, patients with peripheral arterial occlusive disease may have exhausted venous options given prior use for cardiac surgery, varicose vein surgery, or lower limb revascularization. Hence, the use of a radial artery graft may serve as a viable alternative.

METHODS

The systematic review was performed in accordance to the Preferred Reporting Items for Systematic Review and Meta-analysis guidelines. An electronic search was performed on the following databases: Medline (via PubMed); EMBASE; Cochrane library to search for relevant publications. A narrative analysis was conducted.

RESULTS

Four publications were included in this review including two retrospective cohort studies, one case series, and one case report, with a total of 43 patients. The most common indication for lower limb bypass grafting was critical limb ischemia, and the radial artery was chosen as graft conduit, most commonly due to the absence of suitable arm or leg vein. There was one case of 30-day mortality and 11 reinterventions.

CONCLUSION

Despite the encouraging results, the paucity of high-quality studies prevents the establishment of any firm conclusion. This warrants the need for appropriately conducted randomized controlled trials to compare the radial artery graft to autologous vein grafts and prosthetic grafts for lower limb bypass grafting.

Impact of Diabetes Mellitus on Radial and Ulnar Arterial Vasoreactivity after Radial Artery Cannulation: A Randomized Controlled trial

BACKGROUND

Endothelial dysfunction associated with diabetes mellitus (DM) may influence arterial vasoreactivity after arterial stimulus, such as cannulation, and cause changes in diameter and blood flow. Despite the frequent use of arterial cannulation during anesthesia and critical care, little information is available regarding vasoreactivity of the radial and ulnar arteries and its influence on underlying DM.

METHODS

Forty non-DM and 40 DM patients, who required arterial cannulation during general anesthesia, were enrolled. Using duplex Doppler ultrasonography, we measured the patients' arterial diameter, peak systolic velocity, end-diastolic velocity, resistance index, and mean volume flow of both arteries at five different time points.

RESULTS

After radial artery cannulation, ulnar arterial diameter and blood flow did not significantly increase in DM group, as they did in non-DM group. Ulnar arterial resistance index significantly increased in both groups, but the degree of decrease in DM group was significantly less than non-DM.

CONCLUSION

Ulnar artery's ability to increase blood flow for compensating the sudden reduction of radial arterial flow in DM patients was significantly less than that in non-DM patients under general anesthesia. Such attenuated vasoreactivity of ulnar artery to compensate the reduced radial arterial flow may have to be considered in radial arterial cannulation for DM patients.

Radial artery as graft for coronary artery bypass surgery: Advantages and disadvantages for its usage focused on structural and biological characteristics

Radial artery (RA) is the most popular arterial graft after the left internal thoracic artery in both low- and high-risk patients undergoing coronary artery bypass grafting. Various arterial grafts such as the right internal thoracic artery, the right gastroepiploic artery, and the inferior epigastric artery have also gained ground over the past 30 years because of the intimal hyperplasia and atherosclerosis of the saphenous vein leading to late graft occlusion. In this review article we would like to present the utility of the RA as a graft, focused mainly on its structural and biological characteristics.

Adventitial dissection: a simple and effective way to reduce radial artery spasm in coronary bypass surgery

OBJECTIVES

Over the last two decades, the radial artery (RA) has become a routinely used conduit for coronary artery bypass graft surgery. One potential disadvantage of the radial artery is its higher susceptibility to vasospasm compared with other arterial grafts. We investigated whether adventitial dissection of the radial artery can reduce vasoconstriction and increase free blood flow.

METHODS

Following harvesting, the adventitia of the radial artery was dissected using coronary scissors. Surplus distal radial artery segments (n = 35) with and without adventitial dissection of patients undergoing coronary artery bypass surgery were collected and pairwise assessment of vasoreactivity to potassium chloride, U46619 and acetylcholine was performed in organ bath experiments. Free blood flow was measured before and after adventitial dissection.

RESULTS

Full curve and maximal vasoconstriction of the RA to potassium chloride (P = 0.015 and 0.001) and U46619 (P = 0.048 and 0.001) was significantly reduced after adventitial dissection compared with non-adventitial dissected radial arteries. Endothelium-dependent relaxation to acetylcholine of adventitial dissected radial arteries was significantly increased (P = 0.006) compared with non-adventitial dissected radial arteries. Maximal vasorelaxation to acetylcholine was significantly increased for adventitial dissected radial arteries compared with non-adventitial dissected radial arteries (P = 0.018). Free blood flow was significantly increased after adventitial dissection (P = 0.037).

CONCLUSIONS

The adventitial dissected radial artery is less susceptible to vasoconstriction and more prone to vasorelaxation ex vivo and shows an increased free blood flow. Therefore, we suggest adventitial dissection of the radial artery graft to reduce vasospasm for arterial revascularization in coronary artery bypass surgery.

Reduction of arterial graft smooth muscle mass by moderate heat therapy

Radial artery (RA) graft spasm is a major cause of early graft failure in coronary artery bypass grafting surgeries. We explored the feasibility of thermal reduction of smooth muscle mass to attenuate vasoconstriction. Rat and rabbit femoral arteries were treated thermally in situ (45°C to 65°C; 0 s to 120 s) and then excised at various time points for histological and physiological study (pressure-diameter relationships). Human radial arteries were treated in vitro and studied in similar fashion. Weeks after thermal treatment, no overt indication was noted of vasospasm, thrombosis, or scarring in the arterial wall; however, this intervention led to a thermal dose-dependent reduction of vasoconstriction (to phenylephrine or potassium chloride) and to a conspicuous loss of smooth muscle. Pressure-diameter relationships showed no aneurismal dilation of these demuscularized arteries up to 200 mmHg. Qualitatively identical results were obtained in human radial arteries. Thermal ablation of RAs may provide a simple, safe, and effective solution to postsurgical vasospasm.

Radial artery versus saphenous vein conduits for coronary artery bypass surgery: forty years of competition--which conduit offers better patency? A systematic review and meta-analysis

The internal thoracic artery is the most effective conduit for coronary artery bypass surgery; however, most patients have multivessel disease and require additional saphenous vein or radial artery grafts. In this systematic review of the literature and meta-analysis, we aim to compare reported patency rates for these conduits and explore if differences are homogeneous across follow-up intervals. A literature search was performed using Embase, Medline, Cochrane Library, Google Scholar and randomised controlled trial databases to identify studies published between 1965 and October 2009. All studies reporting angiographic comparison of saphenous vein and radial artery conduit patency were included, irrespective of language. The end point was angiographic graft patency stratified over different follow-up intervals. Meta-analysis was performed according to recommendations from the Cochrane Collaboration and Meta-analysis Of Observational Studies in Epidemiology guidelines. We used a random-effect model and the odds ratio as the summary statistic. A total of 35 studies were identified. They reported early patency (≤ 1 year, 6795 grafts), medium-term patency (1-5 years, 3232 grafts) and long-term patency (>5 years, 1157 grafts). Significant variation of comparative patency existed across different follow-up intervals. Early saphenous vein patency was similar to radial artery patency with odds ratio of 1.04 (95% confidence interval 0.68-1.61). Medium-term saphenous vein patency, however, deteriorated significantly (odds ratio 2.06, 95% confidence interval 1.29-3.29). Similarly, long-term patency was better for radial artery conduits (odds ratio 2.28, 95% confidence interval 1.32-3.94). Heterogeneity was due to angiographic patency characteristics and related to risk of bias. In conclusion, the findings of this systematic review of the published literature and meta-analysis support the use of radial artery in preference to saphenous vein conduits for coronary artery bypass surgery.

Rho-kinase inhibitors Y-27632 and fasudil prevent agonist-induced vasospasm in human radial artery

Radial artery (RA) vasospasm remains a potential cause of early graft failure after coronary artery bypass graft surgery, despite pretreatment with alpha-adrenergic or calcium channel blockers. Our aim was to investigate the mechanism of the vasorelaxant effects of Rho-kinase inhibitors (Y-27632 and fasudil) on the human RA. Segments were obtained from 30 patients undergoing coronary artery bypass graft and were divided into 3-4 mm vascular rings. The rings were stimulated with 10(-5) mol/L phenylephrine (PE) by using the isolated tissue bath technique and were relaxed with 10(-6) mol/L acetylcholine. Relaxation responses were recorded for Y-27632 (10(-9)-10(-4) mol/L), fasudil (10(-9)-10(-4) mol/L), and sodium nitroprusside (SNP) (10(-9)-10(-5) mol/L). Y-27632 and fasudil relaxation responses were repeated in either N(G)-nitro-L-arginine (L-NNA), which is a specific endothelial nitric oxide synthase inhibitor, or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), which is a guanylate cyclase inhibitor. SNP relaxation responses were repeated in 10(-8) mol/L Y-27632 and 10(-8) mol/L fasudil. Y-27632 and fasudil caused concentration-dependent vasorelaxation in RA rings precontracted with PE, and maximal relaxation (100%) was recorded at the highest concentration used (10(-4) mol/L). The vasorelaxant effects of Y-27632 and fasudil were significantly reduced in the presence of L-NNA and ODQ, and the pD2 values of Y-27632 and fasudil were not changed. The vasorelaxant effects of SNP were significantly increased in the presence of Y-27632 and fasudil, and the pD(2) values of SNP were not changed. These findings indicate that Y-27632 and fasudil caused concentration-dependent vasorelaxation in the RA rings. Because this effect was decreased in a dose-dependent manner by L-NNA and ODQ, the relaxant effects of Y-27632 and fasudil could be due to stimulation by nitric oxide that is being released. Rho-kinase inhibitors may have an important role in preventing vasospasm in arterial grafts used for coronary artery surgery.

Identification of an up-regulated anti-apoptotic network in the internal thoracic artery

BACKGROUND

The radial artery (RA) is known as an atherosclerosis-prone vessel in contrast to the atherosclerosis-resistant internal thoracic artery (ITA). The purpose of the present study was to compare the gene expression profile of these arteries from the same patient in order to identify genes involved in atherogenesis or intimal hyperplasia.

METHODS

Paired specimens of RA and ITA (n=6) were analyzed by histomorphometry and whole genome microarray. The microarray data underwent pathway analysis to identify biological networks. Laser microdissection (LMD) was used to identify the cellular expression of candidate genes in the intimal or medial layer of the ITA and RA.

RESULTS

Histomorphometric analyses revealed a significantly higher degree of intimal hyperplasia in the RA compared to the ITA. 552 genes were differentially expressed in the ITA and RA. qRT-PCR confirmed a significant up-regulation of six anti-apoptotic genes. p21 (11.8-fold, p=0.011), CCL2 (5.4-fold, p=0.034), SOCS3 (7.2-fold, p=0.002), IER3 (4.1-fold, p=0.048), MCL-1 (2.6-fold, p=0.025) and IL-6 (17.8-fold, p=0.046) were up-regulated in the ITA. LMD confirmed that cells of the intimal layer of the ITA consistently expressed higher levels of all six candidate genes than those of the RA.

CONCLUSIONS

Microarray analysis and qRT-PCR identified significantly up-regulated genes in the ITA involved in an anti-apoptotic network. LMD revealed a higher expression of all anti-apoptotic genes in the intimal area of the ITA. These genes may play an important role in protecting the intima of the ITA from developing hyperplasia and atherosclerosis.

Radial artery in myocardial revascularization

In the past decade, the use of the radial artery as a coronary artery bypass graft has been revitalized. However, there has been controversy regarding harvest techniques, antispasm protocols, and selection of target vessels. It is widely accepted that the patency of radial-artery grafts depends on the severity of native-vessel stenosis. Thus, radial artery grafts should be preferentially used for target vessels with high-grade (>75% stenosis) lesions. In this review article, we analyzed the current status of radial artery grafts as a coronary bypass conduit based on our personal experience and recently published literature data.

Patency rates of endoscopically harvested radial arteries one year after coronary artery bypass grafting

OBJECTIVES

To improve patients' acceptance of the radial artery as a graft for coronary revascularization, we introduced an endoscopic harvesting technique. The aim of this study was to assess graft quality 1 year after the operation.

METHODS

In 50 patients who underwent endoscopic radial artery harvesting for coronary artery bypass grafting, 64-slice computed tomography, electrocardiography, and echocardiography were utilized to assess graft patency and left ventricle function at a 1-year follow-up. In addition, the influencing factors of radial artery graft patency were evaluated. Radial artery patency was compared with a control group from our database.

RESULTS

Any patency of endoscopically harvested radial artery grafts was 78% (39/50) and perfect patency was 72% (36/50) 1 year after coronary revascularization. The implanting surgeon and graft harvester, patient factors, graft properties, medication, and target territory did not influence the patency rates of the radial artery graft. The only significant and strong parameter to predict perfect graft patency was the severity of the target vessel stenosis (P < .001). In patients with a target vessel stenosis of 90% or greater, radial artery graft patency was 90.3% (28/31). Patency rates of endoscopically (72%) and conventionally (74%) harvested radial arteries were not different (P = .822).

CONCLUSIONS

Patency rates 1 year after endoscopic radial artery harvesting are comparable to the open technique. On the basis of our results, we attempt to use the radial artery as a bypass graft only for target coronary arteries with 90% or greater stenosis. We recommend endoscopic harvesting as the technique of choice to harvest the radial artery.

Open Clip-Free Radial Artery Harvesting With the Harmonic Shears

BACKGROUND

The Ultracision Harmonic Scalpel is associated with several advantages in radial artery (RA) harvesting. It allows fewer hemostatic clips to close the collateral branches, less thermal injury of the conduit, and reduced time of harvesting in comparison with the conventional RA harvesting technique with electrocautery and hemostatic clips. We recently started open RA harvesting with the harmonic shears (HSH). In this study, we aimed at evaluating the feasibility of this simplified ultrasonically activated harvesting technique, and report the results of RA harvesting with HSH.

METHODS

The RA harvesting with HSH was performed in 20 patients operated on for myocardial revascularization from July 2004 to December 2005.

RESULTS

The harvest of the RA was completed in little time, without any complication. Neither bleeding from the collateral branches nor spasm alongside the entire length of the RA was observed. No bleeding occurred from the muscles of the forearm.

CONCLUSION

This technique of RA harvesting with HSH is impressive in terms of short time of harvest, complete absence of clips for the collateral branches, and no thermal injury of the conduit.

Arterial grafting for myocardial revascularization: how better is it?

PURPOSE OF REVIEW

Arterial conduits are becoming popular in cardiac surgery. Clinical studies and long-term follow-ups have proven that this technique provides satisfactory long-lasting results. The purpose of this review is to give an overview of the main articles from recent literature and compare the latest results.

RECENT FINDINGS

Arterial conduits are currently used in cardiac surgery and clinical follow-ups are confirming some advantages in performing multiple arterial revascularization compared to the saphenous vein and the mammary artery. Mid-term follow-ups are encouraging the use of the radial artery as the second conduit of choice after the internal mammary artery. Moreover, off-pump cardiac surgery is an alternative to perform extensive myocardial revascularization in selected patients. Use of in-situ mammary arteries and off-pump surgery has already been described as the ideal solution to guarantee the 'no touch aorta technique'. Recent results lead us to use the radial artery and the gastroepiploic artery as complement composite grafts to perform total arterial myocardial revascularization during off-pump coronary surgery.

SUMMARY

Arterial grafting provides satisfactory results. The second graft of choice after the mammary artery is the radial artery, but long-term results are still not available. To reduce the risk of major neurological complications, selected patients benefit from off-pump arterial revascularization.