| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
|
Interact CardioVasc Thorac Surg 2006;5:251-257. doi:10.1510/icvts.2006.129262 © 2006 European Association of Cardio-Thoracic Surgery
Should patients receiving a radial artery conduit have post-operative calcium channel blockers?
a Wessex Cardiothoracic Unit, Southampton General Hospital, Southampton, UK Received 19 January 2006; accepted 23 January 2006
*Corresponding author. Tel./fax: +44-7801548122.
A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether calcium channel blockers or possibly nitrates are necessary if a radial artery conduit has been used for coronary artery bypass grafting. The reported search found 98 papers of which 14 represented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group, relevant outcomes and weaknesses were tabulated. We conclude routine use of calcium channel blockers (CCBs) and nitrates, in order to reduce vasospasm, is in widespread use but none of the clinical studies that we identified provided any evidence for their benefit. Furthermore, one study demonstrated that a vasoconstrictor mediated increase in blood pressure actually increased blood flow in the radial artery, and a further study reported that serotonin induced vasospasm was not attenuated by CCBs in vivo. All these studies are underpowered to exclude a benefit of vasodilators in improving graft patency in the medium term. However, an RCT that sought to prove an increase of 5% in patency rates (which are already around 90% or more) with a power of 80% would have to recruit and perform medium term angiography on 948 patients.
Key Words: Thoracic surgery; Radial artery; Calcium channel antagonists; Coronary arterial bypass graft
A best evidence topic was constructed according to the structured protocol. This protocol is fully described in the ICVTS [1].
You are looking after a 45-year-old bricklayer with severe triple vessel disease who underwent urgent CABG using bilateral internal mammary arteries and a radial artery graft. He has progressed well and is awaiting discharge. He was on no medication on admission and asks you why he needs to have 6 weeks of Diltiazem three times per day as prescribed by your consultant. You have some difficulty justifying this medication and thus resolve to look up the literature that night.
In [patients undergoing coronary grafting], does receiving a [calcium channel blocker] improve [radial artery patency]?
Medline 1966 to Jan 2006. [Exp coronary artery bypass/OR coronary bypass.mp/OR coronary art$ bypass.mp OR CABG.mp OR exp Thoracic surgery/] AND [exp Radial artery/OR radial arter$.mp] AND [exp calcium channel blockers/OR calcium channel blocker$.mp/OR calcium antagonist$.mp/OR exp diltiazem/OR diltiazem.mp/OR exp amlodipine/OR amlodipine.mp OR exp nitrates/OR nitrate$.mp OR GTN.mp OR exp vasodilator agents/OR exp nitroglycerin/].
The search found 98 papers. Of these papers 14 represented the best evidence to answer the clinical question. Of note we included only in-vivo and clinical studies (Table 1).
Gaudino [2] randomised 100 consecutive patients, who had radial artery grafts to Diltiazem or no therapy. All patients were evaluated clinically and with TI201 myocardial scintography but no differences were found. In addition, 83 underwent angiography. Patency was over 95% in both groups and there was no difference between the groups. Twelve patients had assessment of the vasospastic response of the radial artery to serotonin. Diltiazem did not attenuate this response.
Gaudino [3] also looked at the clinical and angiographic effects of chronic channel blocker therapy continued beyond the first year in those having radial artery grafts. One hundred and twenty patients who had radial arteries with no evidence of radial artery dysfunction at 1 year were randomly assigned to continue therapy with diltiazem 120 mg daily or suspend therapy. At 5 years there was no difference in angina recurrence (10% in both groups) radial territory ischaemia ( Shapira [4] compared the use of nitrates and calcium channel blockers in the prevention of radial artery spasm in a randomised trial. No differences in operative mortality or morbidity, long term patency, thallium stress testing, need for stenting, or myocardial infarction were found. In this American study the overall cost of treatment with diltiazem was much more expensive than with nitroglycerin ($16.340 vs. $1.096). Sperti [5] evaluated the response to serotonin of the radial artery graft, the IMA graft and native coronary arteries in patients who had CABG with a radial artery graft. Twenty-two patients were not on any calcium channel blockers and 9 were on chronic diltiazem treatment. Their results showed no significant difference in the diameter of the radial artery in its basal state between groups and thus oral diltiazem did not prevent serotonin induced vasoconstriction of the radial artery grafts. Acer [7] followed 102 patients for 5 years who received a radial artery. All patients were started on diltiazem and converted to oral diltiazem (250 mg daily) and oral aspirin (100 mg daily). Fifty patients had an angiogram. Sixty-four radial grafts were studied and 83% were patent. Diltiazem had continued to be used in 27 and 23 were not on any treatment for various reasons. There were 8 graft failures in the CCB group and 4 in patients who had stopped CCBs. Broadman [8] performed a prospective review of 175 of 249 patients. Two patients had perioperative myocardial infarction but neither was related to radial artery dysfunction. Sixty patients underwent post operative angiography between 1 day and 40 weeks. Of these 28 were on calcium blocker therapy. Patency rate of the radial arteries was 95.7% and there was no effect with calcium blocker usage. Possati [10] followed up 90 patients who received a radial artery, then an angiogram, an average of 9 years post-operatively. All patients received Diltiazem for a year post-operatively but 51 patients stopped this medication for a variety of reasons after this. There was no difference in graft patency, which was still perfect in 88% of patients. Cameron [11] performed an angiogram 5 years post-radial artery grafting in 50 patients. Thirty-seven of these patients received calcium channel blockers. The patency rate was high at 89% and no correlation with CCB usage was found. Skubas [12] randomised 30 patients receiving a radial artery. Ten had intravenous nitroglycerin, 10 had intravenous nicardipine and 10 had normal saline. An intraoperative flow probe assessed radial artery flow and then they measured the change in flow in response to a vasoconstrictor. The flow was similar for all groups and increased for all patients in response to a vasoconstrictor in response to a higher blood pressure. Thus, no vasospasm was seen and a vasoconstrictor did not induce vasospasm. Arena [13] performed angiography on 32 patients 1 year after radial artery harvest. Patients were randomised to nifedipine or control. There were only 2 patients whose radial arteries were found not to be patent and the reasons for this occlusion was felt to be technical rather than due to CCBs. In 2001, Kalus [14] reviewed the literature for the use of calcium channel blockers or nitrates for the prevention of vasospasm. They referenced 17 papers and summarised their findings in a descriptive fashion. They found only small RCTs, small cohort studies and in vitro studies, and concluded that all these studies consistently find no clinical benefits for calcium channel blockers. Moran et al. [15] randomised 115 patients receiving radial arteries to Diltiazem, 180 mg per day for 1 year, or no treatment. Angiography at 1 year showed no difference and there were no clinical differences in symptoms or complications at 30 months follow-up. Myers et al. [9] performed a survey of Canadian surgical centres. Of 27 responding centres, 25 centres routinely use calcium channel blockers and 12 use nitrates in addition to this.
While routine use of calcium channel blockers and nitrates in order to reduce vasospasm is in widespread use, none of the clinical studies that we identified provided any evidence for their benefit. Furthermore, one study demonstrated that a vasoconstrictor mediated increase in blood pressure actually increased blood flow in the radial artery, and a further study reported that serotonin induced vasospasm was not attenuated by CCBs in vivo. All these studies are underpowered to exclude a benefit of vasodilators in improving graft patency in the medium term. However, an RCT that sought to prove an increase of 5% in patency rates (which are already around 90% or more) with a power of 80% would have to recruit and perform medium term angiography on 948 patients.
This article has been cited by other articles:
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
Top
Abstract
1. Introduction
5% both groups) or angiographic patency (
