Interact CardioVasc Thorac Surg 2008;7:500-503. doi:10.1510/icvts.2007.174318
© 2008 European Association of Cardio-Thoracic Surgery
Best evidence topic - Coronary |
For patients undergoing coronary artery bypass grafting at higher risk of stroke is the single cross-clamp technique of benefit in reducing the incidence of stroke?
Shahzad G. Raja*,
Manoraj Navaratnarajah,
Naveed Fida and
C. Saifuddin Kitchlu
Department of Cardiothoracic Surgery, Harefield Hospital, Hill End Road, Harefield, UB9 6JH, Middlesex, UK
Received 23 December 2007;
received in revised form 20 February 2008;
accepted 24 February 2008
*Corresponding author. Tel.: +44 1895 828665; fax: +44 1895 828666.
E-mail address: drrajashahzad{at}hotmail.com (S.G. Raja).
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Abstract
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A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether, for patients undergoing coronary artery bypass grafting at higher risk of stroke, the single cross-clamp (SC) technique is of benefit in reducing the incidence of stroke. Using the reported search 458 papers were identified. Six randomised controlled trials (RCTs), of which one was a duplicate publication, represented the best evidence on the subject. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study comments and weaknesses were tabulated for these. We conclude that current best available evidence, from six RCTs randomising 490 patients, suggests that there is no benefit of SC technique over multiple cross-clamp (MC) technique in terms of reduction in the incidence of stroke (SC=2/206 vs. MC=7/284; P=ns) although there is some advantage of SC technique in causing less neuropsychological deficits and release of serum S-100 protein, a surrogate marker of cerebral injury.
Key Words: Coronary artery bypass grafting; Stroke; Focal neurologic deficit; Evidence-based medicine
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1. Introduction
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A best evidence topic was constructed according to a structured protocol. This protocol is fully described in the ICVTS [1].
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2. Clinical scenario
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Your consultant is about to operate on an urgent in-patient referral with left main stem disease who has long-standing diabetes and hypertension with atheromatous changes in the aorta. You ask him if he will use the single cross-clamp (SC) technique for coronary artery bypass grafting (CABG). He replies that he has not seen any convincing papers that prove that this will protect the patient from stroke and he is concerned that this technique may unnecessarily increase the myocardial ischaemic cross-clamp time. You decide to look up the evidence for his statement.
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3. Three-part question
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For [patients undergoing CABG at higher risk of stroke] is the [single-cross clamp technique] of benefit in reducing the [incidence of stroke]?
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4. Search strategy
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The English language scientific literature was reviewed primarily by searching Medline from 1950 through November 2007 using Ovid interface.
[cross-clamp.mp OR crossclamp.mp] AND [CABG.mp OR exp Thoracic surgery OR Coronary art$ bypass.mp OR Cardiopulmonary bypass.mp OR exp Cardiovascular surgical procedures OR exp Thoracic surgical procedures OR exp Coronary artery bypass] AND [exp stroke OR stroke.mp OR mortality.mp or exp mortality].
The ‘related articles’ function was used to broaden the search and all abstracts, studies, and citations scanned were reviewed. The reference lists of articles found through these searches were also reviewed for relevant articles.
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5. Search outcome
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A total of 458 papers were found using the search strategy and only randomised controlled trials (RCTs) were selected. Six RCTs, of which one was a duplicate publication, were deemed to represent the best evidence on the topic and are summarised in Table 1.
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6. Discussion
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Hammon et al. [2] in a recently published randomised controlled trial (RCT), recruiting high-risk CABG patients divided into multiple clamp (MC) group (n=27) and SC group (n=54) and compared to an additional contemporary group of patients treated with off-pump CABG (n=26), showed that at six months, 26% of 27 MC patients had neuropsychological deficits, 27% of 26 off-pump CABG patients had neuropsychological deficits, and only 9% of 54 SC patients had neuropsychological deficits (P=0.067 vs. MC and off-pump CABG). The authors had published similar results previously as well [3].
Tsang et al. [4] in another RCT recruiting two hundred and sixty-eight consecutive patients undergoing CABG, randomised to MC group (n=134) and SC group (n=134), showed that there were no differences in the number of perioperative myocardial infarctions (Group SC=3 [2.3%]; Group MC=2 [1.5%], P=0.50) or mortality (Group SC=2 [1.5%]; Group MC=3 [2.2%], P=0.50). Two patients randomised to MC were switched to SC intraoperatively because of severe calcification of the ascending aorta. In Group MC, there were two strokes (1.5%) and two (1.5%) postoperative confusions vs. none in Group SC (relative risk=2.0, P<0.05, respectively).
Dar et al. [5] in their RCT recruiting 50 consecutive patients undergoing elective, isolated, primary CABG showed that postoperative S-100 levels were significantly higher in MC group (n=24) than in SC group (n=25) (P<0.015) with no significant difference between the groups in postoperative troponin-T levels. One patient in MC group was excluded because control S-100 levels were higher than postoperative.
Musumeci et al. [6] in their RCT comparing intermittent ischaemic arrest (IIA) (n=43) or SC with intermittent anterograde cold blood cardioplegia (n=48) showed that during elective CABG in patients with no clinical evidence of aortic or cerebro-vascular disease the incidence of peri-operative cerebral microemboli and postoperative neuropsychological disturbances are comparable with both techniques of myocardial preservation. However, median peak troponin I levels were 0.64 µg/l with IIA vs. 0.87 µg/l with SC (P=ns) and troponin T 0.8 µg/l vs. 1.08 µg/l (P<0.03).
Bertolini et al. [7] in their RCT randomised CABG patients into two groups. In Group I, 55 patients underwent CABG using crystalloid cardioplegia and the conventional partial occluding clamp technique to perform proximal anastomoses, whereas in Group II, 45 patients were operated on combining blood cardioplegia and the SC technique. Analysis of combined mortality and morbidity events (adverse events) between the two groups, led to a significant prevalence in Group I patients (P<0.03) in spite of a higher preoperative risk score (P<0.03) and longer ischaemic times (P<0.001) in Group II patients. Moreover, neurological lesions remained confined to Group I patients.
Use of SC technique by avoiding repeated aortic manipulation appears a rational strategy to avoid neurological complications especially in high-risk patients with atheromatous aorta. Interestingly, all the RCTs, except Tsang et al. [4], failed to show a superiority of this technique in reducing the incidence of postoperative stroke. This is mainly due to the multifactorial aetiology of postoperative stroke. Aortic cannulation/decannulation, punching aorta for construction of proximal anastomoses, inadequate deairing strategies are some of the major reasons leading to postoperative stroke apart from cross-clamp application/removal. Perhaps OPCAB ‘no-touch aorta’ total arterial revascularisation could be the ideal technique for avoiding postoperative stroke as it would theoretically avoid generation of micro- as well as macroemboli resulting from the use of cardiopulmonary bypass, aortic manipulation and inadequate deairing.
As for the limitations of the studies included in this BET none provide details about the aetiology of stroke. More importantly, the sample sizes are not adequate to reach statistical significance and last, but not the least, patients at highest risk of stroke were excluded from all trials.
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7. Clinical bottom line
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We conclude that current best available evidence, from six RCTs randomising 490 patients, suggests that there is no benefit of SC technique over MC technique in terms of reduction in the incidence of stroke (SC=2/206 vs. MC= 7/284; P=ns) although there is some advantage of SC technique in causing less neuropsychological deficits and release of serum S-100 protein, a surrogate marker of cerebral injury.
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References
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- Dunning J, Prendergast B, Mackway-Jones K. Towards evidence-based medicine in cardiothoracic surgery: best BETS. Interact CardioVasc Thorac Surg 2003;2:405–409.[Abstract/Free Full Text]
- Hammon JW, Stump DA, Butterworth JF, Moody DM, Rorie K, Deal DD, Kincaid EH, Oaks TE, Kon ND. Coronary artery bypass grafting with single cross-clamp results in fewer persistent neuropsychological deficits than multiple clamp or off-pump coronary artery bypass grafting. Ann Thorac Surg 2007;84:1174–1178.[Abstract/Free Full Text]
- Hammon JW, Stump DA, Butterworth JF, Moody DM, Rorie K, Deal DD, Kincaid EH, Oaks TE, Kon ND. Single crossclamp improves 6-month cognitive outcome in high-risk coronary bypass patients: the effect of reduced aortic manipulation. J Thorac Cardiovasc Surg 2006;131:114–121.[Abstract/Free Full Text]
- Tsang JC, Morin JF, Tchervenkov CI, Platt RW, Sampalis J, Shum-Tim D. Single aortic clamp versus partial occluding clamp technique for cerebral protection during coronary artery bypass: a randomized prospective trial. J Card Surg 2003;18:158–163.[CrossRef][Medline]
- Dar MI, Gillott T, Ciulli F, Cooper GJ. Single aortic cross-clamp technique reduces S-100 release after coronary artery surgery. Ann Thorac Surg 2001;71:794–796.[Abstract/Free Full Text]
- Musumeci F, Feccia M, MacCarthy PA, Ellis GR, Mammana L, Brinn F, Penny WJ. Prospective randomized trial of single clamp technique versus intermittent ischaemic arrest: myocardial and neurological outcome. Eur J Cardiothorac Surg 1998;13:702–709.[CrossRef][Medline]
- Bertolini P, Santini F, Montalbano G, Pessotto R, Mazzucco A. Single aortic cross-clamp technique in coronary surgery: a prospective randomized study. Eur J Cardiothorac Surg 1997;12:413–418.[Abstract]
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Abstract
1. Introduction