Use of verapamil and nitroglycerin solution in preparation of radial artery for coronary grafting

Reducing vasospasm of vein and arterial conduits used in coronary artery bypass surgery: are solutions the solution or is preserved perivascular fat the answer?

The three main conduits used for myocardial revascularization in patients with coronary artery disease (CAD) are the internal thoracic artery (ITA), radial artery (RA) and saphenous vein (SV). In coronary artery bypass grafting (CABG) conduits may be harvested with perivascular adipose tissue (PVAT) intact (pedicled) or removed (skeletonized). Various studies have shown that the patency rate of these bypass grafts may be affected by the preservation or removal of PVAT. Vasospasm is often encountered at harvesting, a condition that has both immediate and long term effects on graft performance. During surgery a variety of antispastic solutions are routinely used on conduits that have anti-contractile and/or vasorelaxant actions. Spasm may be abolished or reduced when PVAT is left intact at harvesting and this is particularly the case for the SV. The protective properties of PVAT are multifactorial, ranging from its mechanical properties in supporting the graft after implantation to the beneficial effect of adipocyte-derived factors. This review aims to outline the possible mechanisms through which preserved PVAT could alleviate vasospasm and improve conduit performance in CABG. Moreover, since preservation of PVAT reduces spasm at and after surgery this review also considers whether antispastic solutions are needed if conduits are harvested with PVAT intact.

To reverse or not to reverse the radial artery in coronary artery bypass graft surgery? Histopathologic concerns and media thickness

Background and aims

Radial artery (RA) is a popular coronary artery bypass grafting (CABG) conduit. The challenging issue is vasospasm. A few studies are available on histopathological differences between RA's proximal and distal ends. This study aims to compare histopathological features of the proximal and distal end of RA to find the best technique for anastomosis.

Methods

In this matched case-control study, 80 patients were included who underwent CABG and used RA as a graft. Ten subjects were excluded. RA was harvested by open technique, and a cocktail of Papaverine, Verapamil, and Nitroglycerine was frequently applied topically. One centimeter of proximal and distal ends of the RA was evaluated considering its Histopathology. Clinical signs of RA graft vasospasm were monitored from harvesting until the post-operative period. Intima, media, and intima-media thickness (IMT) index were compared between the two cohorts.

Results

Vasospasm occurred in 1.41% of patients. The mean intimal thickness in the proximal and distal ends were, respectively, 0.20 (standard deviation [SD] 0.17 mm) vs. 0.31 (SD 0.18 mm) (p < 0.001). The mean media thickness in the distal end was higher than the proximal end (0.98 [SD 0.36] vs. 1.09 [SD 0.37], p = 0.004). IMT index of the proximal and distal ends showed a statistically significant difference (0.22 [SD 0.17] vs. 0.31 [SD 0.19]) (p < 0.001).

Conclusion

The overall incidence rate of vasospasm in our study is comparable with other studies using the same cocktail. Proximal RA has a relatively lower medial thickness compared to the distal part, which may induce less vasospasm in CABG patients.

The impact of Verapamil for radial access in diagnostic cerebrovascular angiograms: A retrospective case-control study

INTRODUCTION

Different combinations of medications are utilized during wrist access for radial artery (RA) or ulnar artery (UA) catheterization in neuroendovascular procedures to preclude vasospasm. These "cocktails" commonly include the calcium channel blocker Verapamil, without established benefit. We analyze outcomes in patients with and without Verapamil in their "cocktail" by using a case-control cohort of our single-center experience.

METHODS

A prospective log of consecutive patients who underwent diagnostic cerebral angiograms using RA/UA access was retrospectively reviewed, and patients were grouped into Verapamil and non-Verapamil cohorts. The primary outcomes assessed were the presence of forearm skin rashes (hives) and RA/UA spasms. Our initial management included Verapamil (5 mg) in the cocktail, but Verapamil was removed after we noticed the development of hives in multiple patients immediately following its injection.

RESULTS

A total of 221 patients underwent 241 RA/UA diagnostic cerebral angiograms and were included in our analysis. One hundred and forty-nine patients (61.8%) underwent catheterization with Verapamil and 92 (38.2%) were catheterized without it. Four of the 149 patients in the Verapamil group (2.7%) developed hives during the procedure and were treated with Benadryl (25 mg). Of the 92 patients who did not receive Verapamil, there were zero (0%) cases of hives and one (1.1%) case of vasospasm.

CONCLUSION

Verapamil in the "cocktail" for wrist access diagnostic cerebral angiograms was associated with periprocedural hives, but not associated with a significant reduction in spasm compared to the non-Verapamil group. Our findings suggest that the administration of prophylactic Verapamil for these procedures may not be necessary.

Antispastic Effect of Fasudil and Cocktail of Fasudil and Nitroglycerin in Internal Thoracic Artery

BACKGROUND

Spasm of arterial grafts in coronary artery bypass grafting is a clinical problem and can occasionally be lethal. Perioperative spasm in the internal thoracic artery (ITA) and coronary arteries occurs in 0.43% of patients. This study aimed to investigate the antispastic effect of a RhoA/Rho-kinase (Rho-associated coiled-coil-containing protein kinase [ROCK]) inhibitor (fasudil) with and without nitroglycerin in combination in the ITA.

METHODS

Isolated human ITA rings taken from 68 patients who were undergoing coronary bypass were studied in a myograph. Cumulative concentration-relaxation curves for fasudil (-9 to -3.5 log M) were established in the ITA, which was precontracted with potassium chloride or U46619. The inhibitory effect of fasudil (-6.3 or -5.3 log M) or fasudil in combination with nitroglycerin were also tested. The ROCK2 protein was measured by Western blot.

RESULTS

Fasudil caused similar relaxation in ITA rings contracted by potassium chloride or U46619. Pretreatment with -5.3 log M fasudil significantly depressed contraction induced by potassium chloride (P = .004 vs control; P = .017 vs -6.3 log M) and U46619 (P = .010 vs control; P = .041 vs. -6.3 log M). Fasudil in combination with nitroglycerin had more effect and more rapid and sustained relaxation than either vasodilator alone. Fasudil caused a decrease of ROCK2 protein content (P = .014).

CONCLUSIONS

Fasudil fully relaxes some vasoconstrictor-induced contraction and decreases ROCK2 protein content in the ITA. The combination of fasudil and nitroglycerin has a superior effect than either vasodilator alone. The new cocktail solution composed of fasudil and nitroglycerin (pH 7.4) has effective antispastic action and may prove to be a new antispastic method for arterial conduits during coronary bypass surgery.

Vasodilation by Verapamil-Nitroglycerin Solution in Microvascular Surgery

OBJECTIVE

Papaverine is a topical vasodilator commonly used during microvascular surgery to inhibit undesired vasoconstriction. A previous national shortage of papaverine prompted evaluation of an alternative, effective vasodilator. This study aims to assess the experience of a solution of verapamil and nitroglycerin (VG) as a potential alternative pharmacologic vasodilator.

STUDY DESIGN

Retrospective case series.

SETTING

Two tertiary academic medical centers.

SUBJECTS AND METHODS

Among 298 patients, 306 consecutive free tissue transfers performed between 2014 and 2017 for head and neck defect reconstruction utilized a VG solution. Patient and flap characteristics, intraoperative patient and flap complications, and postoperative complications were reviewed. Diameter of the cervical recipient artery was measured intraoperatively before and after topical application of the VG solution in a subset of 43 patients (44 flaps).

RESULTS

Flaps included fibula, radial forearm, subscapular system, and anterolateral thigh. In total, 3 (0.98%) flaps failed with varied etiology unrelated to the VG solution (venous thrombosis, arterial anastomosis thrombosis, physical damage to the perforator). Specific to topical application of the VG solution, the mean recipient artery diameter increased from 2.1 to 3.1 mm, a 48% increase (P < .01). There were no intraoperative cardiac events or complications attributable to the VG solution.

CONCLUSION

We describe the use of a VG solution for pharmacologic vasodilation during microvascular free tissue transfer. Its use was associated with an acceptable incidence of adverse events, none of which were directly attributable to the VG solution. Apparent and sustained vasodilation was demonstrated. The VG solution represents a safe and efficacious alternative to papaverine in microvascular surgery.

Preventing spasm of the radial artery conduit during coronary artery bypass grafting: Nicardipine versus verapamil

BACKGROUND AND AIM OF THE STUDY

In vitro studies have shown a reduction in radial artery spasm with the use of calcium antagonists. The purpose of this study was to evaluate the efficacy of topical treatment of the radial artery conduit using either verapamil or nicardipine before the anastomoses.

METHODS

This prospective randomized study included 131 patients, who underwent coronary artery bypass grafting surgery with the use of the radial artery as a conduit. In 65 patients, the harvested radial artery was topically treated with verapamil and in 66 patients with nicardipine. After harvesting the radial artery, the direct flow through the conduit was measured in vitro before 5-minute incubation in nicardipine or verapamil and measured again after incubation. The flow before and after incubation was compared. Postincubation flow was also compared in the two groups. After performing the anastomosis, the flow through the radial artery was measured in vivo.

RESULTS

The mean flow after NaCl incubation was 19.93 ± 12.66 mL/min and after incubation in the Ca+ channel blocker 47.16 ± 14.58 mL/min (P < .001). No significant difference in postincubation free flow was found between verapamil (46.29 ± 15.43 mL/min) and nicardipine (48.01 ± 13.77 mL/min; P = .503).

CONCLUSION

Topical treatment with Ca+ channel blockers reduces radial artery spasm and significantly increases the free flow through the radial artery conduit. Nicardipine is a safe and effective alternative of verapamil in preventing spasm of radial artery conduit.

Use of nitroglycerin and verapamil solution by organ bath technique in preparation of left internal thoracic artery for coronary artery bypass surgery

Background

The aim of this prospective study was to compare the effect of application of nitroglycerin and verapamil solution (GV) by organ bath technique with other methods of applications and solutions on the free blood flow of LITA. The technique was not described for in situ graft before.

Method

The patients were randomly assigned to four groups: group I (n_32, GV solution by organ bath technique), group II (n_30, papaverine solution by organ bath technique), group III (n_29, topical GV solution) or group IV (n_29, topical papaverine solution). In each patient, pedicled LITA was harvested; thereafter applied with the randomized different methods and solutions. The free flow from the distal end of the divided LITA was measured for 15 s under controlled hemodynamic conditions after harvesting (Flow 1). The flow of LITA was measured again just prior to anastomosing the conduit (Flow 2).

Result

The mean blood flow in LITA was 56.2 ± 5.0 ml/min before application of solutions. After application, the mean blood flow in group I:102.3 ± 7.0 ml/min, in group II: 92.7 ± 3.4 ml/min, and in group III: 88.6 ± 2.2 ml/min and in group IV: 81.4 ± 2.1. Proportional increases in blood flow observed in group I (82.6%) > group II (65.1%) > group III (57.6) > group IV (44.8%) (p < 0.05).

Conclusions

GV solution by organ bath technique is effective and superior in comparison to use of papaverine using organ bath technique or topical spray of GV or papaverine solution.

Relaxant effect of the prostacyclin analogue iloprost on isolated human radial artery: An approach for the reversal of graft spasm

Radial artery graft spasm in the perioperative or postoperative period of coronary bypass surgery necessitates urgent treatment due to risk of graft failure and mortality. Herein, we evaluated the effect of iloprost, a prostacyclin (PGI₂) analogue, against the contractions produced by noradrenaline and potassium chloride on isolated human radial artery. Following the determination of endothelial and vascular relaxing capacities of the arteries, iloprost (10^-9M-10^-6M) was cumulatively applied on rings precontracted submaximally with the spasmogens. In some rings, the response to iloprost was assessed following pretreatment with nitric oxide (NO) synthase inhibitor, l-NAME (3×10^-4M,30min). Iloprost produced complete relaxations on radial artery rings precontracted with noradrenaline whereas, only moderate relaxations against the contractions induced by potassium chloride. Notably, the relaxation to iloprost was remarkably blunted in radial arteries with impaired endothelial function. Moreover, the relaxation to iloprost was unchanged in rings pretreated with l-NAME. Our results demonstrated that iloprost could be a potent relaxant agent in reversing radial artery spasm, particularly initiated by noradrenaline, possibly acting via an endothelium-mediated mechanism unrelated to NO.

Antispastic Management in Arterial Grafts in Coronary Artery Bypass Grafting Surgery

Arterial grafts have long-term patency superior to vein grafts but have a tendency to develop spasm that can lead to potentially life-threatening complications. A perfect antispastic protocol should include advanced surgical technique and adequate pharmacologic methods. All pharmacologic vasodilator drugs relax the vessel through specific mechanisms, and therefore, there is no perfect, single best vasodilator to prevent or treat spasm of the arterial graft against all mechanisms of contraction. One of the choices is to use a combination of pharmacologic vasodilators targeting different mechanisms of spasm to obtain the reliable and best effect.

Fasudil Is an Effective Graft Vasodilator for Gastroepiploic Artery in Coronary Artery Bypass Grafting

OBJECTIVE

The gastroepiploic artery (GEA) has been used as an alternative arterial in situ graft for coronary artery bypass grafting (CABG). However, because of the large individual differences and the spastic nature of the GEA, caution has to be exercised during harvesting. We evaluated the usefulness of fasudil, a Rho kinase inhibitor, as a vasodilator for right GEA (RGEA) graft after harvesting, compared with the conventional agents papaverine and verapamil-nitroglycerin.

METHODS

Between June 2009 and January 2013, 30 patients with ischemic heart disease who underwent isolated CABG using RGEA graft were randomly assigned to fasudil (n = 10), papaverine (n = 10), or verapamil-nitroglycerin (n = 10) group. Fasudil (2.67 mmol/L), papaverine (1.0 mmol/L) mixed with heparinized blood, or verapamil-nitroglycerin (30 μmol/L each) was injected intraluminally into the RGEA graft after harvesting. Right GEA graft free flow (GFF), hemodynamic changes, and histopathology of RGEA were evaluated.

RESULTS

Intraluminal injection of fasudil increased GFF significantly (P < 0.001) and markedly from 41.5 ± 31.5 mL/min at baseline to 149.3 ± 46.7 mL/min after injection. Papaverine increased GFF (P < 0.001) from 40.0 ± 35.8 to 64.9 ± 33.7 mL/min, and verapamil-nitroglycerin also increased GFF (P < 0.001) from 38.8 ± 32.1 to 79.0 ± 35.2 mL/min. The GFF was significantly higher (P = 0.001) in the fasudil group than in the other two groups. Histopathologically, fasudil treatment markedly increased the diameter of RGEA graft, while maintaining integrity of the multiple elastic lamellae. Blood pressure did not change significantly after drug injection in all groups.

CONCLUSIONS

Fasudil is more potent than papaverine or verapamil-nitroglycerin in increasing GFF of RGEA graft for CABG.

Effect of Benidipine in Human Internal Mammary Artery and Clinical Implications

BACKGROUND

Graft spasm remains challenging in coronary artery bypass grafting (CABG). Calcium antagonists are commonly used in patients with coronary artery disease. This study investigated the inhibitory effect of third-generation dihydropyridine calcium channel antagonist benidipine on the vasoconstriction induced by various vasoconstrictors in the human internal mammary artery (IMA).

METHODS

Isolated human IMA rings (N = 65, taken from 37 patients undergoing CABG) were studied in a myograph in 2 ways: the relaxing effect of benidipine on vasoconstrictor-induced precontraction by KCl and U46619 and the depressing effect of benidipine at plasma concentrations on the contraction. Enzyme-linked immunosorbent assay (ELISA) was used to measure the change of the protein related to the L-type calcium channel.

RESULTS

Benidipine caused more relaxation in KCl-contracted (86.7% ± 3.3%; n = 12) than in U46619-contracted (63.8% ± 5.3%; n = 8; p < 0.001) IMA rings. Pretreatment of IMA with plasma concentrations of benidipine (-6.92 log M) significantly depressed subsequent contraction by KCl (from 17.3 ± 2.7 mN to 7.4 ± 1.2 mN; n = 6; p < 0.05) but did not significantly affect the contraction caused by U46619. Benidipine also caused a decrease of caveolin (CaV)1.2 protein content (0.55 ± 0.02 versus 0.63 ± 0.02 mg/mL; p < 0.05).

CONCLUSIONS

We conclude that in human IMA, the third-generation dihydropyridine calcium channel antagonist benidipine has a potent inhibitory effect on the vasoconstriction mediated by a variety of vasoconstrictors. Use of benidipine in patients undergoing CABG may provide vasorelaxant or antispastic effects in the grafts.

Spasm in Arterial Grafts in Coronary Artery Bypass Grafting Surgery

Spasm of arterial grafts in coronary artery bypass grafting surgery is still a clinical problem, and refractory spasm can occasionally be lethal. Perioperative spasm in bypass grafts and coronary arteries has been reported in 0.43% of all coronary artery bypass grafting surgery, but this may be an underestimate. Spasm can develop not only in the internal mammary artery but more frequently in the right gastroepiploic and radial artery. The mechanism of spasm can involve many pathways, particularly those involving regulation of the intracellular calcium concentration. Endothelial dysfunction also plays a role in spasm. Depending on the clinical scenario, the possibility of spasm during and after coronary artery bypass grafting should be confirmed by angiography. If present, immediate intraluminal injection of vasodilators is often effective, although other procedures such as an intraaortic balloon pump or extracorporeal membrane oxygenation may also become necessary to salvage the patient. Prevention of spasm involves many considerations, and the principles are discussed in this review article.

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.

Nafamostat mesilate: can it be used as a conduit preserving agent in coronary artery bypass surgery?

Background

Graft vessel preservation solution in coronary artery bypass surgery is used to maintain the graft conduit in optimal condition during the perioperative period. Nafamostat mesilate (NM) has anticoagulation and anti-inflammatory properties. Therefore, we investigated NM as a conduit preservative agent and compared it to papaverine.

Methods

Sprague-Dawley (SD) rat thoracic aortas were examined for their contraction-relaxation ability using phenylephrine (PE) and acetylcholine (ACh) following preincubation with papaverine and NM in standard classical organ baths. Human umbilical vein endothelial cells (HUVECs) were cultured to check for the endothelial cell viability. Histopathological examination and terminal deoxynucleotidyl transferase dUTP nick end labeling assay were performed on the thoracic aortas of SD rats.

Results

The anti-contraction effects of papaverine were superior to those of NM at PE (p<0.05). The relaxation effect of NM on ACh-induced vasodilatation was not statistically different from that of papaverine. Viability assays using HUVECs showed endothelial cell survival rates of >90% in various concentrations of both NM and papaverine. A histopathological study showed a protective effect against necrosis and apoptosis (p<0.05) in the NM group.

Conclusion

NM exhibited good vascular relaxation and a reasonable anti-vasocontraction effect with a better cell protecting effect than papaverine; therefore, we concluded that NM is a good potential conduit preserving agent.

Potent vasodilatory effect of fasudil on radial artery graft in coronary artery bypass operations

BACKGROUND

The radial artery (RA) is a useful conduit for coronary artery bypass grafting (CABG) but is susceptible to vasospasm during harvesting. We evaluated the usefulness of fasudil, a Rho kinase inhibitor, in dilating the RA graft and increasing graft free flow (GFF) compared with the conventional graft-dilating agents papaverine and verapamil-nitroglycerin (VG).

METHODS

Between June 2012 and January 2013, 45 patients with ischemic heart disease who underwent isolated CABG using the RA were enrolled and randomly assigned to fasudil (n = 15), papaverine (n = 15), or VG (n = 15). Fasudil (2.67 mmol/L), papaverine (1.0 mmol/L) mixed with heparinized blood, or VG (30 μmol/L each of verapamil and nitroglycerin) was injected intraluminally into the RA graft after harvesting. Main outcome measures were RA GFF, hemodynamic changes, and histopathologic examination of the RA.

RESULTS

In the fasudil group, GFF increased significantly (p < 0.001) from 36.8 ± 20.4 at baseline to 148.0 ± 88.3 mL/min after injection. GFF increased significantly (p < 0.001) from 36.0 ± 19.0 to 72.3 ± 36.7 mL/min in the papaverine group and increased significantly (p < 0.001) from 39.5 ± 23.3 to 64.3 ± 29.9 mL/min in the VG group. The GFF was significantly higher (p = 0.001) in fasudil-treated RA than in papaverine- or VG-treated RA. Histopathologically, RA graft diameter was markedly increased after fasudil injection, and the structure of the multiple elastic lamellae was intact. Blood pressure did not change significantly after drug injection in all groups.

CONCLUSIONS

Fasudil exhibited a very potent vasodilatory effect on the RA compared with conventional papaverine or VG, resulting in increased GFF. This agent is useful for dilating RA grafts in CABG.

Vasorelaxation induced by new third-generation dihydropyridine calcium antagonist azelnidipine in human internal mammary artery

BACKGROUND

Graft spasm remains challenging in coronary artery bypass graft (CABG) surgery. Calcium antagonists are commonly used in patients with coronary artery disease. We investigated the inhibitory effect of the new third-generation dihydropyridine calcium antagonist azelnidipine on the vasoconstriction in human internal mammary artery (IMA) from patients undergoing CABG.

METHODS

Isolated IMA rings (n = 68, taken from 28 patients) were studied in myograph in two ways: the relaxing effect of azelnidipine on vasoconstrictor-induced precontraction by potassium chloride (KCl) and U46619; and the depressing effect of azelnidipine at plasma concentrations on the contraction.

RESULTS

Azelnidipine caused full relaxation in KCl-contracted (96.5% ± 0.7%) and in U46619-contracted (96.5% ± 1.4%) IMA rings (n = 8), with 28.8-fold higher potency to KCl than to U46619 (EC50 -7.49 ± 0.21 versus -6.03 ± 0.11 log M, p < 0.01). Pretreatment of IMA with plasma concentrations of azelnidipine (-6.1 log M) significantly depressed subsequent contraction to KCl (from 25.8 ± 2.2 mN to 16.0 ± 1.5 mN, p < 0.01) and U46619 (from 30.6 ± 4.0 mN to 16.5 ± 2.2 mN, p < 0.05).

CONCLUSIONS

We conclude that in human IMA, azelnidipine has a potent inhibitory effect on the vasoconstriction mediated by a variety of vasoconstrictors. Thus, use of azelnidipine in CABG patients is favored for treating and preventing graft spasm.

Arterial grafts: clinical classification and pharmacological management

In comparison with standard saphenous vein grafts, use of the internal mammary artery (IMA) as a coronary artery bypass graft has achieved superior long-term results. This is related to the differences in the biological characteristics between the venous and arterial grafts. However, even arterial grafts are not uniform in their biological characteristics. The variation in the perioperative behavior of the grafts and in their long-term patency may be related to different characteristics. These factors should be taken into account in the use of arterial grafts, some of which are subjected to more active pharmacological intervention during and after the operation to obtain satisfactory results. To better understand the biological behavior of the grafts, their common features and their differences, a clinical classification may be useful for a practicing surgeon. Based on experimental studies of their vasoreactivity combined with anatomical, physiological and embryological considerations, we have proposed a functional classification for arterial grafts that may be useful clinically. Our classification suggests that there are three types of arterial grafts: Type I-somatic arteries; Type II-splanchnic arteries; and Type III-limb arteries. Type I arteries have enhanced endothelial function and release more nitric oxide and other relaxing factors. Type II arteries, such as the gastro-epiploic artery, and Type III arteries, such as the radial artery (RA), have higher pharmacological reactivity to vasoconstrictors. This classification explains why the IMA has the best long-term patency. Because Type II and III arteries are prone to spasms due to higher contractility, they require more active pharmacological interventions. Furthermore, the harvesting technique of the conduits, including the saphenous vein and IMA, are described and discussed in this article. Prevention of spasms using two cocktails of medications (verapamil + nitroglycerin and nicardipine + nitroglycerin) during harvesting of the conduits is described. These solutions have been demonstrated to be clinically effective.

Direct vasodilation by transdermal administration of nitroglycerin: preliminary, randomized, placebo-controlled trial of nitroglycerin skin spray for premedication before artery puncture

PURPOSE

Transdermal administration of nitroglycerin (NTG) before arterial puncture may improve puncture success. The objective of this study was to evaluate the vasodilation effect of NTG skin spray on brachial arteries.

MATERIALS AND METHODS

We recruited 10 healthy volunteers. On different days and in random order we sprayed their skin above the right or left brachial artery with a solution containing 0.3 mg NTG or above the right brachial artery with physiological saline. A radiologist ultrasonographically measured the cross-sectional area of right brachial artery before and at 5-min intervals for up to 25 min after spraying and calculated the rate of increase of the area.

RESULTS

The average vasodilation rate after spraying with NTG above the right brachial arteries of 10 volunteers was 16.4% at 5 min, 23.6% at 10 min, 19.6% at 15 min, and 16.5% at 20 min; spraying with NTG above the left brachial artery or with physiological saline alone elicited few changes. The vasodilation rate 10 min after spraying with NTG above the right brachial artery was significantly higher than for control groups (P < 0.001).

CONCLUSIONS

Transdermal application of NTG spray dilated the targeted brachial artery. This technique may be a good premedication before artery puncture.

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.

Verapamil and Nitroglycerin Improves the Patency Rate of Radial Artery Grafts

The best way to prevent spasm of the radial artery is still under investigation. We retrospectively compared the effectiveness of topical verapamil-nitroglycerin with papaverine in preventing graft spasm in 215 patients who underwent isolated conventional coronary artery bypass using a radial artery. Postoperative angiographic data were successfully collected in 116 patients. Perioperative radial artery graft spasm was observed in 2 patients in the papaverine group and 1 in the verapamil-nitroglycerin group; this difference was not considered significant. Complete or functional occlusion was detected by postoperative angiography in 13 grafts (10 in the papaverine group and 3 in the verapamil-nitroglycerin group). Multivariate regression analysis revealed that topical papaverine and grafting to the right coronary artery significantly increased the rate of occlusion of radial artery grafts. Although further studies are needed, our data support the view that topical verapamil-nitroglycerin reduces the incidence of radial artery graft occlusion.

A new antispastic solution for arterial grafting: nicardipine and nitroglycerin cocktail in preparation of internal thoracic and radial arteries for coronary surgery

OBJECTIVE

Antispastic protocols for arterial grafts are important in arterial grafting for coronary artery bypass grafting surgery. We designed a new nicardipine and nitroglycerin cocktail that is composed of a second-generation dihydropyridine calcium antagonist, nicardipine and nitroglycerin (30 micromol/L), and examined its effect in human internal thoracic and radial arteries.

METHODS

Human internal thoracic (n = 86) and radial (n = 74) artery segments from 72 patients undergoing coronary artery bypass grafting were studied. Relaxation against 3 classic vasoconstrictors (potassium chloride, thromboxane A(2) mimetic U46619, and alpha-adrenoceptor agonist norepinephrine) and prophylactic effect on contraction against these vasoconstrictors were examined. The effect of the nicardipine and nitroglycerin cocktail on the endothelial function in internal thoracic and radial arteries was studied in response to acetylcholine.

RESULTS

Nicardipine and nitroglycerin induced almost full relaxation (92.2% +/- 4.7% to 97.9% +/- 1.0%, P < .001 in internal thoracic arteries and 95.4% +/- 1.9% to 96.7% +/- 3.3%, P < .001 in radial arteries, n = 6-8) against 3 vasoconstrictors with significant prophylactic effect on contraction (maximal contraction was depressed to 32.5% to 76.4%, P < .05 or P < .001, and EC50s were increased to 5 to 42-fold more, P < .01). After treatment with the nicardipine and nitroglycerin cocktail, the acetylcholine-induced relaxation was unchanged (P > .05).

CONCLUSION

The use of the nicardipine and nitroglycerin cocktail provides a new antispastic protocol that has rapid onset, full relaxation, and excellent prophylactic effect against all known mechanisms of vasospasm and maximally protects the endothelial and smooth muscle function of the internal thoracic and radial arteries. The cocktail is therefore expected to provide a new method in treating grafts in coronary artery bypass grafting with the best antispastic effect and protection of the graft.

Endoscopic Radial Artery Harvesting Reduces Postoperative Pain and Neurologic Complications

BACKGROUND

Endoscopic radial artery harvest provides better cosmetic result without compromising the quality of the graft. We sought to compare postoperative harvesting site neurologic and vascular outcome.

METHODS

From 10/2002 until 10/2004, 50 patients were randomized to have their radial artery harvested for coronary bypass either endoscopically (group A, n = 25) or conventionally (group B, n = 25). Radial arteries were preoperatively evaluated by Doppler echocardiography. Neurologic and functional status was assessed by a self reporting questionnaire with a semiquantitative (1-5) scale. Vascular status of the forearm was assessed by control echocardiography.

RESULTS

At an average follow-up of 37 +/- 7 months, patients undergoing endoscopic radial artery harvesting had less overall neurologic complications (11 versus 17 patients, P = .023) and they were less severe (0.8 +/- 1.1 versus 2.2 +/- 1.2; P < .001). Ulnar flow increase was similar among the groups: 13.1 +/- 5.43 cm/s in group A versus 15.9 +/- 4.9 cm/s in group B (P = .147) as well as ulnar artery diameter increase 0.29 +/- 0.16 mm in group A versus 0.29 +/- 0.26 cm in group B (P = .914).

CONCLUSION

Endoscopic radial artery is safe and does not compromise graft quality or forearm and hand circulation postoperatively. Along with providing a better cosmetic result, endoscopic artery harvesting reduces postoperative harvesting site pain and neurologic complications.

Subxiphoid multi-arterial OPCAB: surgical technique and initial case report

BACKGROUND

The surgical technique of transsternal coronary artery bypass grafting (CABG) has remained relatively stagnant for the past three decades. Unlike general and orthopedic surgery, cardiac surgery has made very little progress in converting our most common procedure into a minimally invasive alternative. Minithoracotomy techniques introduced in 1995 enjoyed a brief period of popularity but were inherently single vessel (LIMA-LAD) procedures and thus not an answer to the need for a less invasive multivessel operation. Totally endoscopic CABG has been performed in a small number of cases but the learning curve is very steep and the rate of conversion to open surgery remains high with only a few successful multivessel cases. There remains a great need for a less invasive approach that has the potential to graft all coronary targets without disturbing the chest wall and which can be performed by all current and future surgeons with acceptable hospital costs. A small subxiphoid incision has been used for single vessel grafting to anterior or inferior targets, but until now lateral wall grafting has not been considered possible. Development of a successful multivessel subxiphoid technique on the beating heart, including lateral wall grafting, is now reported in this article.

METHODS

Subxiphoid multi-arterial bypass grafting was performed on a 79-year-old male using commercially available equipment but modified surgical techniques. Instead of midline sternotomy, full exposure to the heart was obtained by four essential steps: (1) removal of the xiphoid process, (2) vertical lifting of the lower sternum, (3) caudal retraction of the diaphragm, and (4) spreading of the wound using a specific retractor to create an adequate working portal. Both internal mammary arteries were harvested for their full length as skeletonized conduits using only direct vision (headlight and loupes). Off-pump distal anastomoses to the left anterior descending (LAD) and first obtuse marginal branch of the circumflex (OMB-1) were performed using available stabilizer systems. The obtuse marginal was exposed using the Medtronic Starfish suction-positioner without any hemodynamic compromise. The wound was closed with a simple running fascial suture and the patient discharged on postoperative day 4 with no complications and no angina.

CONCLUSIONS

Most practicing surgeons are reluctant to perform multiple distal grafts through small incisions because of the difficulty in simultaneously mastering a host of new skills at the same time (robotics, endoscopics, beating heart techniques). The subxiphoid approach offers the potential to perform distal anastomoses to all regions of the beating heart with excellent exposure while utilizing the same skill sets that surgeons now possess. There is potential that further evolution of this technique will permit outpatient CABG while providing long-term clinical outcomes superior to coronary stenting.

Development of a local vasodilator delivery system using fibrin glue to prevent arterial graft from spasm

The clinical benefits of coronary artery bypass graft operations can be compromised by postoperative vasospasm. Traditionally, local papaverine (PPV) has been employed during the procedure to prevent and counteract vasospasm. But the relatively short action period limited its application. Fibrin glue (FG) might be a potential carrier of PPV for counteracting vasospasm in a longer action period than PPV solution. After FG incorporated with PPV (PPV-FG) was locally administrated in axillary and femoral arteries of dogs, PPV concentrations in artery vessels surrounding the administration sites were compared with the concentrations at the same sites in dogs given PPV solution. The properties of PPV's release in vitro and maintenance in vessel as well as the influence on the mean peripheral blood pressure and drug concentration in peripheral vein after the introduction PPV-FG on the surface of artery in dogs were evaluated. FG was considered to provide a sustained release of PPV and could maintain a high PPV concentration in artery vessel around the administration site. The results suggested that FG was an effective substrate for reserving PPV in the administrated site in a defined period.

Comparison of the pretreatment effects of mixed vasodilators (3-D solution) on radial and internal thoracic arteries by using a 3-dimensional anaglyph electron microscope technique

OBJECTIVE

Currently, internal thoracic arteries (ITA) and radial arteries (RA) are the first choice of conduits for coronary artery bypass grafts (CABG). Because the perioperative vasospasm continues to be a major problem, a number of pharmacologic agents such as papaverine, calcium receptor blockers, nitroglycerine, and phenoxybenzamine have been suggested as topical antispasmodics that may be used in the pre- and postoperative periods. In the present study, we investigated the quantitative efficacies of the mixed solution, which included verapamil, nitroglycerin, and papaverine, on RA and ITA using a scanning electron microscope with a 3-dimensional anaglyph technique.

METHODS

Diameter changes of RA and ITA in response to clinically important vasodilators were measured on 40 RA and 40 ITA rings from patients who had been subjected to coronary artery bypass procedure after 20 minutes of ex vivo incubation with verapamil (45 microg/L), nitroglycerin (45 microg/L), papaverine solution (266 micromol/L or 0.1 micro/mL), and 30 mL autologous heparinized whole blood (individual patient's blood obtained before cardiopulmonary bypass contained 100 IU of heparin per kg of patient weight). The pretreatment action was assessed by measuring the response to vasodilators.

RESULTS

In all cases, we did not observe graft vasospasm in any of the conduits during the intraoperative period between postanastomosis and sternal closure. In the postoperative period, we did not record any evidence of ischemic change in patients' electrocardiographic and myocardial enzyme analyses. None of the cases required inotropic support after the operation. The diameters of the pretreated RA and ITA were: minimum, 2.1 mm; maximum, 4.0 mm; and mean value, 2.80 +/- 0.46 mm. The diameters of the pretreated ITA were: minimum, 1.2 mm; maximum, 2.5 mm; and mean value, 1.76 +/- 0.35 mm. Incubated arterial segment diameters for the RA were: minimum, 2.8 mm; maximum, 5.2 mm; and mean value, 3.95 +/- 0.65 mm. These values for the ITA were: minimum, 1.5 mm; maximum, 3.9 mm; and mean value, 2.37 +/- 0.50 mm. These findings were statistically significant for both arterial grafts (P <.05).

CONCLUSIONS

According to our study findings, the mixed solution demonstrates a broad range of efficacy. We conclude that the described vasodilator solution with heparinized autologous blood seems to be very effective and may be used as a pretreatment agent in CABG conduits. Although papaverine has the shortest duration of action, its efficiency is increased by verapamil and nitroglycerin, in our opinion. To the best of our knowledge, high-quality imaging of CABG conduits with the 3-D anaglyph technique using a scanning electron microscope was a first in the literature. This technical approach may be used for confirming the ultrastructural anatomy and the quantitative vasodilator effects of arterial conduits. We believe that valuable anatomo-pathologic details of the CABG conduit can be obtained by this technique.

Skeletonized harvesting improves the early-term and mid-term perfect patency of a radial artery graft

OBJECTIVE

A radial artery (RA) graft is frequently used for coronary artery bypass grafting (CABG), but little information exists regarding the early- and mid-term patency associated with the harvesting procedure. The objective of this study is to compare the early- and mid-term patency of the RA graft obtained using non-skeletonized and skeletonized harvesting.

METHODS

Altogether, 131 patients and 159 anastomoses were studied. In 85 patients the RA was harvested non-skeletonized (group A: procedures between September 2000 and November 2002), whereas in 46 patients the RA was harvested skeletonized (group B: procedures between November 2002 and April 2004). Angiography results were analyzed before discharge [A: postoperative day (POD) 14.7 +/- 2.9, 75 patients, 90 anastomoses; B: POD 13.7 +/- 1.9, 38 patients, 47 anastomoses], and after 1 year (A: POD 386.8 +/- 149.3, 44 patients, 51 anastomoses; B: POD 267.1 +/- 148.7, 11 patients, 13 anastomoses).

RESULTS

There was no difference in patency between the two groups (group A vs group B, 96.7% vs 100%, P = not significant [NS], in the early-term, 96.2% vs 100%, P = NS, in the mid-term). However, the perfect patency rates for groups A and B were 86.7% and 98.1%, respectively, in the early-term (P = 0.034) and 77.5% and 100%, respectively, in the mid-term (P = 0.048). The location and severity of the target vessel did not influence the angiographic results.

CONCLUSION

The early- and mid-term patency of RA grafts was excellent, and skeletonized harvesting improved the perfect patency rates at both time points.

Efficacy of Physiologic Temperature on the Spasm of Harvested Radial Artery

BACKGROUND

The potential disadvantage of using the radial artery for coronary artery bypass grafting is its increased tendency to vasospasm. Therefore, different antispastic agents are being used in the perioperative and postoperative period. During the preparation of the radial artery, normal local and systemic temperatures are lost.

METHODS

We investigated the effects of topical normal saline solution at 20 degrees C (group SI), normal saline solution at 36 degrees C (group SII), diltiazem at 20 degrees C (group DI), and diltiazem at 36 degrees C (group DII) on radial artery free flow. Each group contained 10 patients undergoing coronary bypass surgery. Free flow and local temperature were measured at 3 stages: after the exploration and preparation of the distal 3 cm of the radial artery, after total preparation of the radial artery, and a median of 12 minutes after the pedicle had been sprayed with one of the agents.

RESULTS

Parallel to the significant decrease of the second local temperatures (P < .001), the second flow of the 4 groups decreased significantly (P < .001).

CONCLUSION

Hypothermia plays an important role in radial artery vasospasm, and normothermia may be the best perioperative vasodilating agent since the normal radial artery flows were reached with normothermia.

Mid-term follow up of patients using the St. Jude Medical Aortic Connector System for proximal vein graft in CABG

The aortic connector system may reduce stroke during proximal venous anastomosis. However, the overall anastomotic patency rate has been generally reported to be low. From October 2002 to March 2004, 68 patients who received proximal anastomosis using the St. Jude Aortic Connector System were included in the study. There were 47 men and 21 women and their mean age was 65.68+/-6.68 yr old (52 to 85 yr). Grafts were evaluated by coronary angiography or multi-slice 16 channel 3-D CT at 6 days and at 6 months postoperatively. In the immediate postoperative period, no stenosis was observed by either angiography (n=22) or 3D CT (n=46). At 6-month postoperatively, we performed either angiography (n=7) or 3-D CT (n=52). Of these patients, 5 patients showed graft stenosis in the midportion, and 3 in the ostium. There were no stroke. Simple, and effective proximal anastomosis with good protection from cerebrovascular accident was achieved especially when calcification or atheromatous plaque was observed at the ascending aorta in the operation room. However, our mid term patency results raise concerns related to venous graft stenosis in the midportion. Therefore, longer follow up is recommended.

Topical Vasodilators for Preventing Radial Artery Spasm during Harvesting for Coronary Revascularization: Comparison of 4 Agents

BACKGROUND

There is still controversy about which vasodilator solution is best for storing radial artery (RA) conduits prior to coronary artery bypass grafting. The aim of this pilot study was to investigate how 4 different topical vasodilators applied during RA harvesting affect blood flow with the vessel in situ.

MATERIALS AND METHODS

The subjects were 85 patients who underwent RA harvesting in preparation for coronary artery bypass grafting. Each case was assigned to 1 of 5 groups (17 RAs each) that were treated with different solutions: normal saline (control), nitroglycerin, diltiazem, papaverine, and adenosine. Standard clinical concentrations were used. The RA was partially harvested (pedicle attached proximally) and flow rates and hemodynamic parameters (mean arterial pressure, heart rate, central venous pressure) were recorded at 2 time points: (1) pretreatment and (2) after 5 minutes of immersion in 60 mL of treatment solution. Results were compared within and between groups, and post-treatment-to-pretreatment ratios were calculated for each variable.

RESULTS

There were no significant differences among the groups' mean pretreatment flow rates (P = .979) or mean posttreatment flow rates (P = .069). All except the diltiazem group showed a significant rise in mean flow rate from pretreatment to posttreatment. The mean posttreatment-to-pretreatment ratios for RA flow rate were 1.28 +/- 0.39 in the saline group, 1.85 +/- 0.72 in the nitroglycerin group, 1.31 +/- 0.48 in the diltiazem group, 1.37 +/- 0.64 in the papaverine group, and 1.23 +/- 0.42 in the adenosine group. Only the mean flow ratio in the nitroglycerin group was significantly higher than that in the saline group (P = .003). The mean flow ratios in the other vasodilator groups were not statistically different from the flow ratio in the saline group.

CONCLUSIONS

These preliminary results indicate that topical application of nitroglycerin solution effectively prevents perioperative spasm of the RA in patients undergoing coronary artery bypass surgery. The authors recommend this solution for preparation and storage of RA grafts. Randomized controlled trials with power analysis will give more definitive information.

Vasorelaxant effect of opioid analgesics on the isolated human radial artery

BACKGROUND AND OBJECTIVE

Arterial grafts are prone to vasospasm. Opioid analgesics are commonly used in the perioperative course of cardiac surgical procedures. Therefore, we investigated the direct effects of morphine, meperidine, fentanyl and remifentanil on the human radial artery.

METHODS

Radial artery segments, obtained from 20 patients, were precontracted with phenylephrine. Using the organ bath technique, the endothelium-independent vasodilatation was tested in vitro by addition of cumulative concentrations of morphine, meperidine, fentanyl and remifentanil in separate organ baths, in the presence or absence of naloxone. Indomethacin and NG-nitro-L-arginine methyl ester was added to all organ bath in order to determine the effects of prostaglandins and nitric oxide, respectively.

RESULTS

Morphine (10(-8) - 10(-4) mol L-1), meperidine (10(-10) - 10(-6) mol L-1), fentanyl (10(-10) - 10(-6) mol L-1) and remifentanil (10(-8) - 10(-4) mol L-1) caused a concentration-dependent vasorelaxation in the human being artery rings. The relaxations in the presence of naloxane did not change. The maximal relaxant effects of meperidine and fentanyl were significantly greater than those of morphine and remifentanil (P < 0.05).

CONCLUSIONS

These findings indicate that morphine, meperidine, fentanyl and remifentanil produce concentration-dependent and endothelium-independent relaxations in human being radial artery rings. Meperidine and fentanyl are more potent relaxant agents than morphine and remifentanil in the human being radial artery in vitro.

Comparative Effects of Tolazoline and Nitroprusside on Human Isolated Radial Artery

BACKGROUND

The radial artery is increasingly being used in coronary revascularization as an alternative conduit to a saphenous vein graft. Its perfect endothelial capacity provides a high patency rate comparable with the internal mammary artery (IMA). However, its spastic characteristics cause difficulties during its intraoperative preparation and may lead to early postoperative graft failure. Thus, treatment and/or prevention of radial artery spasm with an effective vasodilator agent is essential for its longevity. Endogenous vasoconstrictors, including noradrenaline, endothelin-1, and thromboxane A2, are likely to play a role in the pathogenesis of graft spasm. In the present study, we evaluated the vasorelaxant effect of tolazoline, a nonselective alpha-adrenoceptor blocker, against the contractions induced by various spasmogenic agents in an isolated human radial artery.

METHODS

Tolazoline (10(-9)-10(-4) M) or sodium nitroprusside (SNP, 10(-9)-10(-4) M) were cumulatively applied on radial artery rings precontracted submaximally with noradrenaline, endothelin-1, thromboxane analogue, U46619, or potassium chloride. In addition, some rings were pretreated with tolazoline (4 x 10(-6) M) for 30 minutes and the contractile response curve to noradrenaline was assessed in its presence.

RESULTS

Tolazoline effectively reversed noradrenaline-induced contractions in the radial artery, whereas it failed to produce remarkable relaxations on rings contracted with other spasmogenic agents, while SNP overcame the contractions induced by all spasmogens to a similar extent. In addition, brief pretreatment of radial artery rings with tolazoline significantly inhibited the contractions to noradrenaline.

CONCLUSIONS

Tolazoline is not as broadly effective as SNP against all spasmogens investigated; however, it may be effective in counteracting alpha-adrenoceptor-mediated vasospasm in human radial arteries.

Effects of Papaverine and Glycerilnitrate-Verapamil Solution as Topical and Intraluminal Vasodilators for Internal Thoracic Artery

BACKGROUND

Arterial spasm is described as an event occurring after left internal thoracic artery (LITA) harvesting. Many vasodilators have been used to treat or prevent LITA spasm. The aim of this study is to compare the effects between glyceril-trinitrate/verapamil (GV) solution and papaverine to treat LITA spasm and to determine the best delivery method.

METHODS

One hundred consecutive ischemic patients were randomly assigned to three groups: group GV (n = 34, GV solution), group P (n = 33, papaverine), or group C (n = 33, normal saline). In each patient, pedicled LITA was harvested, thereafter sprayed with the randomized solution, and covered with a sponge. Fifteen minutes after heparin administration, LITA was distally divided; flow per minute was calculated after measuring the free flow for over 15 seconds; this is named "topical free flow." Then, the vasodilator was injected intraluminally and free flow per minute was measured; this is called "intraluminal free flow."

RESULTS

Analysis of variance was applied to detect differences among groups; paired-sample t test was used for LITA topical free flow versus intraluminal free flow within single groups. Mean LITA free flows were as follows: group GV, topical free flow = 38.6 +/- 25.2 mL/min versus intraluminal free flow = 58.8 +/- 29 mL/min (p < 0.0001); group P, topical free flow = 45.4 +/- 38.9 mL/min versus intraluminal free flow mL/min (p < 0.0001); group C, topical free flow = 31.6 +/- 19.9 mL/min versus intraluminal free flow = 34 +/- 19.8 mL/min (p = 0.14). Topical free flow difference among the three groups was not statistically significant (p = 0.1); intraluminal free flow difference was statistically significant (p = 0.001). Intraluminal free flow in group GV and in group P were higher than intraluminal free flow in group C (p = 0.004 and 0.001, respectively). Intraluminal free flow of group P was higher than that of group GV; this difference did not reach statistical significance (p = 1.00).

CONCLUSIONS

Glyceril-trinitrate/verapamil solution and papaverine are able to treat the spasm and increase the flow of the LITA, when they are used intraluminally. When used topically, these vasodilator agents do not ensure an optimal free flow.

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

The radial artery (RA) is gaining popularity as a bypass conduit for coronary artery bypass grafting, and its impact on clinical practice has been extensively explored. In the present article, we provide a review of postoperative hand circulation, vascular biological characteristics of the RA graft, the efficacy of vasodilator therapies, and mid-term clinical results of use of the RA graft. Fundamental studies revealed excellent vascular biological characteristics of the RA graft as a living arterial conduit, making it almost equivalent to the internal thoracic artery (ITA) graft. Clinical studies have yielded encouraging mid-term results. Most studies reported in favor of the RA graft over the saphenous vein graft with regard to patency rate, freedom from cardiac events, and survival. However, superiority of either the RA or right ITA graft has not been conclusively determined. The long-term results of RA grafts remain unknown, but at present, supplementary use of an RA graft with a left ITA graft appears feasible for CABG.

Greater vasopressin-induced vasoconstriction and inferior effects of nitrovasodilators and milrinone in the radial artery than in the internal thoracic artery

BACKGROUND

Vasopressin may be a potential cause of spasm in both the radial artery and the internal thoracic artery. This study compared the vasopressin-induced contraction and the effects of milrinone, nitroglycerin, and nitroprusside in vasopressin-induced contraction between the human radial artery and the internal thoracic artery to find effective antispastic methods for arterial grafts.

METHODS

Concentration-contraction (normalized as force gram produced by each millimeter of the circumference tissue of the artery) curves for vasopressin with or without pretreatment of vasodilators and concentration-relaxation curves for the vasodilators listed were established in the human radial artery (n = 107) and internal thoracic artery (n = 122) segments.

RESULTS

Vasopressin induced a greater contraction in the radial artery than in the internal thoracic artery (1.9 +/- 0.2 g/mm vs 0.6 +/- 0.1 g/mm, P < .001) with a higher sensitivity (lower EC(50): -9.28 +/- 0.11 vs -8.91 +/- 0.05 log(10)M, P = .006). Milrinone was less potent than nitroglycerin and nitroprusside with higher EC(50) (P < .05) in both the internal thoracic artery and radial artery. Pretreatment with milrinone and nitroprusside significantly inhibited vasopressin contraction in the internal thoracic artery but had little effect in the radial artery. Pretreatment with nitroglycerin did not significantly inhibit the maximum vasopressin contraction in either the internal thoracic artery or radial artery.

CONCLUSION

The radial artery is more prone to develop spasm related to vasopressin than is the internal thoracic artery, and the effect of vasodilators in vasopressin-induced contraction is different in the radial artery from that in the internal thoracic artery. A more significant prophylactic antispastic effect of milrinone and nitroprusside is demonstrated in the internal thoracic artery than in the radial artery. Therefore, more intensive antispastic treatment is necessary in the radial artery than in the internal thoracic artery during coronary artery bypass grafting.

Effects of hydrostatic distention on in vitro vasoreactivity of radial artery conduits

BACKGROUND

Surgical preparation of coronary conduits may affect early and long-term patency through endothelial and smooth muscle injury. We investigated the effect of hydrostatic distention on the in vitro endothelial function and contractile properties of the human radial artery.

METHODS

Human radial arteries were harvested and distended to physiologic pressure or suprasystemic pressure (>300 mm Hg) by using heparinized whole blood for 2 minutes. Distal segments were retrieved and prepared into 3-mm rings. These were mounted and stretched to optimum resting tension in oxygenated Krebs solution at 37 degrees C. Contraction responses to potassium, norepinephrine, and serotonin and relaxation responses to acetylcholine and nitroprusside were evaluated. Undistended radial artery segments were used as controls.

RESULTS

Vasocontraction to all 3 contractile agonists was significantly different between groups. The radial artery subjected to suprasystemic pressure distention achieved the lowest percentage of maximum contraction (potassium, P <.001; norepinephrine, P <.05; serotonin, P <.05). The median effective concentration was also significantly reduced in this group, indicating increased sensitivity to all 3 agonists. Receptor-mediated contractility was significantly reduced in both distended groups when compared with controls. Relaxation to acetylcholine and nitroprusside was significantly reduced in the suprasystemic pressure-distended group, which had a tendency to vasospasm when exposed to a physiologic concentration of acetylcholine (10(-6) mol/L). Median effective concentrations for both acetylcholine and nitroprusside were not different between groups.

CONCLUSIONS

Excessive distention of the radial artery leads to a significant reduction in vasoreactivity, which may be attributed to a disruption of the vascular endothelium and media, with a propensity for graft spasm with exposure to acetylcholine.

Radial versus femoral approach for percutaneous coronary diagnostic and interventional procedures; Systematic overview and meta-analysis of randomized trials

OBJECTIVES

We sought to compare, through a meta-analytic process, the transradial and transfemoral approaches for coronary procedures in terms of clinical and procedural outcomes.

BACKGROUND

The radial approach has been increasingly used as an alternative to femoral access. Several trials have compared these two approaches, with inconclusive results.

METHODS

The MEDLINE, CENTRAL, and conference proceedings from major cardiologic associations were searched. Random-effect odds ratios (ORs) for failure of the procedure (crossover to different entry site or impossibility to perform the planned procedure), entry site complications (major hematoma, vascular surgery, or arteriovenous fistula), and major adverse cardiovascular events (MACE), defined as death, myocardial infarction, emergency revascularization, or stroke, were computed.

RESULTS

Twelve randomized trials (n = 3,224) were included in the analysis. The risk of MACE was similar for the radial versus femoral approach (OR 0.92, 95% confidence interval [CI] 0.57 to 1.48; p = 0.7). Instead, radial access was associated with a significantly lower rate of entry site complications (OR 0.20, 95% CI 0.09 to 0.42; p < 0.0001), even if at the price of a higher rate of procedural failure (OR 3.30, 95% CI 1.63 to 6.71; p < 0.001).

CONCLUSIONS

The radial approach for coronary procedures appears as a safe alternative to femoral access. Moreover, radial access virtually eliminates local vascular complications, thanks to a time-sparing hemostasis technique. However, gaining radial access requires higher technical skills, thus yielding an overall lower success rate. Nonetheless, a clear ongoing trend toward equalization of the two procedures, in terms of procedural success, is evident through the years, probably due to technologic progress of materials and increased operator experience.

Outcome assessment of hand function after radial artery harvesting for coronary artery bypass

The radial artery has gained widespread acceptance as a conduit for coronary artery bypass. Advantages include minimal donor site discomfort, ease of handling, excellent early patency rates, and the possibility of freedom from late conduit atherosclerosis. Although most series describe minimal morbidity, a significant incidence of radial sensory neuropathy and isolated instances of hand claudication and ischemia have been reported. We performed an outcome study utilizing the Short Form-36, the Upper Limb-Disabilities of Arm, Shoulder and Hand, and a modified self-administered hand diagram to compare 288 patients undergoing coronary artery bypass utilizing the radial artery with a control group of 174 patients undergoing coronary artery bypass without the radial artery. The data were analyzed by the t test for continuous variables and the chi-square test for categorical variables, and subsequently a multivariate regression model was constructed. No patients developed hand claudication or ischemia. Although there was an incidence of radial sensory neuropathy of 9.9% associated with radial artery harvest, it was not significantly higher than the incidence in the control group (5.2%, p =.16). Intrinsic patient factors such as obesity, age, diabetes, and peripheral vascular disease were the principal determinants of overall health and quality of life issues.

Comparative efficacies and durations of action of phenoxybenzamine, verapamil/nitroglycerin solution, and papaverine as topical antispasmodics for radial artery coronary bypass grafting

OBJECTIVE

Radial arteries are increasingly used as conduits for coronary artery bypass grafts, but perioperative graft vasospasm continues to be a concern. Phenoxybenzamine, verapamil/nitroglycerin solution, and papaverine have been advocated as topical antispasmodic agents. We compared the relative efficacies and durations of action of these agents.

METHODS

Isometric tension developed in response to clinically important vasoconstrictors was measured in 100 radial artery rings (from patients undergoing coronary artery bypass grafting, n = 25) after 15 minutes of ex vivo incubation with phenoxybenzamine, verapamil/nitroglycerin solution, papaverine, or vehicle (control). Duration of action was assessed by measuring responses to vasoconstrictors in antispasmodic pretreated and control rings at intervals through 5 hours.

RESULTS

Verapamil/nitroglycerin solution reduced vasoconstriction in response to epinephrine, angiotensin II, prostaglandin F(2alpha), and phenylephrine but its effect had almost completely waned after 5 hours. Phenoxybenzamine prevented vasoconstriction in response to epinephrine, dopamine, and phenylephrine, with its effect lasting at least 5 hours. Papaverine had limited antispasmodic efficacy and prevented vasoconstriction in response to potassium (60 mmol/L) and phenylephrine for only 1 hour at the longest.

CONCLUSIONS

Verapamil/nitroglycerin solution has a broad efficacy against a range of vasoconstrictors but a limited duration of action. Papaverine has the shortest duration of action. Phenoxybenzamine is an effective agent with a prolonged duration of action, specifically preventing catecholamine mediated vasospasm of radial artery conduits.

The Influence of Calcium Channel Antagonists on Isolated Human Distal Radial Arteries

A comparison was made between the efficacies and potencies of calcium channel antagonists on contractions induced by 5-hydroxytryptamine, norepinephrine, or high-potassium buffer in isolated human distal radial arteries. Also, the impact of removal of extracellular calcium ions on contractions induced by 5-hydroxytryptamine or norepinephrine was assessed. Isometric contractions were induced by agonists, and relaxant responses to calcium channel antagonists, nifedipine, diltiazem, verapamil, or mibefradil were examined. 5-hydroxytryptamine-induced contractions when compared with norepinephrine or high-potassium induced contractions were significantly more sensitive to inhibition by nifedipine (pIC50 = 7.53 +/- 0.15; 6.78 +/- 0.12; 6.6 +/- 0.22, respectively, mean +/- SEM). Diltiazem was more effective in producing relaxations when contractions were elicited with 5-hydroxytryptamine (pIC50 = 6.48 +/- 0.84) or norepinephrine (pIC50 = 6.20 +/- 0.21) than with high potassium (pIC50 = 5.43 +/- 0.10). Verapamil was more effective at relaxing arteries contracted with 5-hydroxytryptamine (pIC50 = 6.09 +/- 0.19) or norepinephrine (pIC50 = 6.00 +/- 0.17) than with high potassium (pIC50 = 5.60 +/- 0.16). Mibefradil was not very effective in producing relaxations. The studies revealed that removal of extracellular calcium significantly attenuated contractions produced by 5-hydroxytryptamine (-67.7 +/- 6.3%) and norepinephrine (-89 +/- 1.5%). In conclusion, our data indicates that nifedipine was the most effective drug in producing relaxations; also, contractions produced by 5-hydroxytryptamine and norepinephrine were found to be critically dependent on the presence of extracellular calcium.

Radial artery use is safe in patients with moderate to severe left ventricular dysfunction

BACKGROUND

Using radial artery grafts in patients with moderate to severe left ventricular dysfunction (LVD; ejection fraction < 35%) has been discouraged for the fear that postoperative vasopressor support may cause graft spasm and lead to ischemic complications. We, therefore, examined the safety of radial grafts in aortocoronary bypass (ACB) patients with LVD.

METHODS

Data were collected from 5,455 patients who underwent isolated ACB between January 1995 and September 2001. One thousand eight hundred three patients received a radial artery graft (RadACB), and 3,652 patients did not (NoRadACB). Three hundred seven RadACB, and 819 NoRadACB operations were performed in LVD patients. A matched (age, sex, urgency of operation, diabetes, and renal insufficiency) cohort analysis was performed in LVD patients. Univariate and logistic regression analyses were performed in the entire population and the unmatched RadACB and NoRadACB patient subgroups to examine the effect of radial artery use on postoperative death or myocardial infarction rate.

RESULTS

The matched cohort analysis revealed a similar rate of death or myocardial infarction (RadACB, 11 of 242 patients; NoRadACB, 16 of 242 patients; p = 0.32). Left ventricular dysfunction was associated with a higher rate of death or myocardial infarction in both unmatched groups (RadACB, odds ratio, 2.36; 95% confidence interval, 1.38 to 4.58; p = 0.004; NoRadACB, odds ratio, 1.62; 95% confidence interval, 1.18 to 2.24; p < 0.001) and in the entire population (odds ratio, 1.77; 95% confidence interval, 1.32 to 2.35; p = 0.003). An interaction term for patients with LVD and a radial artery graft, which was forced into the logistic regression model for the entire population, was not predictive of death or myocardial infarction (odds ratio, 1.52; 95% confidence interval, 0.75 to 3.10; p = 0.25).

CONCLUSIONS

Left ventricular dysfunction carries similar risk for postoperative death or myocardial infarction in RadACB and NoRadACB patients. The presence of LVD in isolation is not a contraindication to the use of radial grafting.