Volume 129, Issue 2 , Pages 307-313, February 2005
No-touch aorta off-pump coronary surgery: The effect on stroke
Article Outline
Objective
Studies examining the neuroprotective effects of off-pump coronary artery bypass grafting have shown inconsistent results. Most studies, however, have not differentiated between clampless and clamp off-pump techniques. The aim of this study was to evaluate the effect of avoiding aortic manipulation on major neurologic outcomes after off-pump coronary artery bypass grafting.
Methods
A total of 700 consecutive patients undergoing multiple-vessel off-pump coronary artery bypass grafting between 2000 and 2003 were included. The 429 patients undergoing aortic no-touch technique were compared with 271 patients in whom partial aortic clamps were applied. The aorta was screened by manual palpation, and epiaortic ultrasonography was used selectively.
Results
The frequency of detected atherosclerotic aortic disease was higher in the no-touch group (17.4% vs 5.1%, P < .0001). No-touch revascularization was achieved with arterial conduits, arranged in T-graft or in situ configurations (50%). The respective graft/patient ratios were 2.5 ± 0.6 and 2.6 ± 0.6 in the side-clamp and no-touch groups (P = .009); however, revascularization of the posterolateral myocardial territory was comparable (87% vs 90%, difference not significant). The incidence of stroke (0.2% vs 2.2%, P = .01) was significantly lower in the no-touch group (1/429). Logistic regression identified partial aortic clamping as the only independent predictor of stroke (odds ratio 28.5, confidence interval 0.22-333, P = .009), increasing this risk 28-fold. Peripheral vascular disease (P = .068), diabetes (P = .072), and history of stroke (P = .074) trended toward stroke.
Conclusions
Avoiding partial aortic clamping during off-pump coronary artery bypass grafting provides superior neurologic outcome. The results are reproducible and irrespective of the severity of aortic disease or the method of aortic screening. This technique is recommended whenever technically feasible.
Although the death rates associated with cardiac operations have declined during the past decade, neurologic complications remain a substantial source of morbidity and mortality.1 Explanations for this finding have focused on changing risk profiles in patient age, coexisting diseases, and diagnostic test use.1 Embolic dislodgment of atherosclerotic plaques during surgical aortic manipulations has been recognized as a major cause of stroke.2, 3 Coronary artery bypass grafting (CABG) done without CPB (off-pump CABG [OPCAB]) eliminates the risk of atheroemboli associated with aortic cannulation, crossclamping, and pump-related platelet aggregate emboli.4 Although it has been reported that the risk of stroke is lowered by OPCAB,5, 6 this benefit has been inconsistently demonstrated7, 8 and was not reproduced in a randomized study.9, 10, 11 Most studies, however, have not differentiated between OPCAB strategies with partial aortic clamps for the construction of proximal aortic anastomoses and those in which revascularization was performed without aortic manipulation (no-touch technique).6, 7, 8, 9, 10, 11 Compelling data have shown that the placement and removal of these clamps are linked to cerebral embolic load12 and thus the risk of embolic stroke. Interestingly, studies evaluating the effect of partial aortic clamping and, reciprocally, the neurologic benefit in avoiding aortic manipulation have yielded contradictory results.5, 13 Subgroup analysis by Calafiore and colleagues13 determined the subsequent risk of stroke, suggesting that it compares to the risk after total aortic manipulations required for on-pump CABG. Conversely, Patel and coworkers5 have proposed that avoiding aortic manipulation during OPCAB is not associated with improved neurologic outcome. Thus the superiority of any OPCAB technique in terms of major neurologic outcome in unselected patients remains undetermined.
The use of arterial in situ or T configurations during OPCAB allow clampless revascularization without any aortic manipulation (aortic no-touch).5, 14 The purpose of this study was to compare major neurologic outcomes after aortic no-touch versus side-clamp OPCAB techniques in the general population. To avoid preselection for either OPCAB or on-pump CABG and subsequent potential bias in patient allocation, we limited our study cohort exclusively to patients undergoing OPCAB.
Patients and methods
Study design
The data from 700 consecutive patients who underwent isolated OPCAB with multiple grafts between September 2000 and September 2003 were acquired. The 471 patients who were operated on without aortic manipulation (no-touch group) were compared with the 229 patients in whom partial aortic clamps were applied during the construction of proximal aortic anastomoses (side-clamp group). OPCAB procedures comprised 60% of the isolated CABG operations performed during this period, and arterial revascularization was applied in 75% of the patients.
Patients who underwent minimally invasive direct CABG and those undergoing midsternotomy single graft anterior wall revascularizations by in situ left internal thoracic artery (ITA) were not included, to avoid preselection for the no-touch group. Proximal mechanical connectors or clampless suture-based proximal devices were not used in any of the patients.
The aorta was routinely screened by digital palpation. The degree of aortic disease was graded in accordance with the criteria of Mills and Everson.15 When this was graded as none or mild (areas free of aortic disease easily identified), the patient was considered eligible for both techniques and patient allocation was based on technical considerations.16 No-touch OPCAB was favored when the extent of aortic disease was graded as moderate (disease moderately extensive but with adequate disease-free areas) or severe (circumferential disease with no disease-free areas). Thus by definition the prevalence and severity of aortic disease were higher in the no-touch group.
Epiaortic ultrasonography was performed selectively. A 7.5-MHz probe (Hewlett-Packard Company, Palo Alto, Calif) was used when undetermined findings were encountered during digital aortic palpation or when a high index of suspicion arose after chest radiography or coronary angiography. The ultrasonographic findings were evaluated by the surgeon himself.
All patients were routinely screened by carotid Doppler assessments. The patients who required carotid endarterectomy (symptoms with unilateral stenosis >70% or symptoms with severe bilateral stenosis) were excluded from this study.
Definition of terms
Patients' data were collected and analyzed according to the Society of Thoracic Surgeons National Cardiac Surgery database guidelines and definitions (http://www.ctsnet.org/doc/4314). Operative mortality was defined as death occurring within 30 days of the operation. Neurologic complications were defined as any global or focal neurologic deficit that was evident after emergence from anesthesia and categorized as either permanent or reversible (transient ischemic attacks and prolonged reversible ischemic neurologic deficit). All neurologic events were evaluated by a neurologist and further assessed by computed tomographic scan.
Surgical technique and postoperative management
Operations were performed through midline sternotomy. Anticoagulation was achieved with 2 mg/kg heparin, and the activated clotting time was maintained above 300 seconds. The heart was stabilized with a suction tissue stabilization system (Octopus; Medtronic, Inc, Minneapolis, Minn). A deep pericardial retraction suture was placed at the posterior fibrous pericardium medial to the proximal part of the inferior vena cava to help manipulate and rotate the heart to vertical and lateral positions. A right-sided pericardial incision directed toward the inferior vena cava was selectively performed to facilitate venous return. Vessel occlusion was achieved by external encircling silicone rubber bands. Intracoronary shunts were used occasionally.
Grafting in the no-touch group was composed of arterial conduits only. These included the left and right ITAs, the radial artery (RA), and the right gastroepiploic artery (RGEA). The grafts were deployed as left-sided in situ bilateral ITA or T configurations constructed of bilateral ITA or left ITA-RA. The ITAs were routinely skeletonized,16 and dissection of the RA and the RGEA was facilitated by ultrasonic scalpel (Harmonic Scalpel; Ethicon Endosurgery, Cincinnati Ohio). The choice of configuration was determined by technical considerations related to the conduits, as has been previously described for conventional on-pump CABG.15 When T grafts were used, T anastomoses were constructed before the distal coronary anastomoses. The RGEA was always used as in situ graft.
Revascularization in the side-clamp group was achieved with ITAs and saphenous vein grafts. All saphenous vein grafts were attached to the aorta and constructed proximally after placement of partial aortic clamp. Anterior wall revascularization was routinely performed first in the sequence of grafting in both groups.
After the operation, all patients received intravenously administered isosorbide dinitrate (4-20 mg/h) for 2 days. Oral calcium-channel blockers (Dilatam; Teva, Petah-Tikva, Israel) were given to patients who received RA or RGEA conduits and continued for 6 months. Antiplatelet therapy included aspirin at 250 mg/d (recommended for indefinite use) and clopidogrel at 75 mg/d (Plavix; Sanofi Winthrop, Gentilly, France) for 6 postoperative weeks.
Data analysis
The categoric variables were tested for group independence with the χ2 test. The results are expressed as the percentages and P value. Numeric variables were compared with both the t test and the nonparametric Mann-Whitney test. Data are expressed as mean ± SD with P value. Logistic regression was used to evaluate the effect of preoperative and intraoperative descriptors on occurrence of neurologic complications, early death, and the combined end point of stroke or death. Results of logistic regression were expressed as odds ratio (OR) with associated 95% confidence interval (CI) and P values. All analyses were performed with SPSS 11 software (SPSS Inc, Chicago, Ill).
Results
The baseline characteristics among the two groups were comparable, with the exception of a higher prevalence of renal dysfunction in the side-clamp group (Table 1). Operative data are listed in Table 2. The no-touch technique was performed in 61% of the cases. The prevalence and severity of aortic disease were greater in the no-touch group. Moderate to severe atheromatous involvement was detected in 16.5% of these patients, whereas all but 3 patients (1%) in the side-clamp group were free of involvement or had only mild involvement (P < .0001). Despite a higher mean number grafts in the side-clamp group (2.5 ± 0.6 vs 2.6 ± 0.6, P = .009), revascularization of the posterolateral territory (the distribution of obtuse marginals or posterior descending arteries) was comparable (Table 2).
TABLE 1. Preoperative characteristics
| Variable | No-touch group (n = 429) | Side-clamp group (n = 271) | P value |
|---|---|---|---|
| Age (y) | .235 | ||
 Mean | 67.4 ± 11.5 | 68.4 ± 10.9 | |
| Range | 33–94 | 40–92 | |
| Age ≥ 80 y (No.) | 56(13.1%) | 27(10.0%) | .233 |
| Female (No.) | 117(27.3%) | 81(30.0%) | .436 |
| Hypertension (No.) | 283(66.0%) | 166(61.7%) | .253 |
| Diabetes (No.) | 169(39.4%) | 108(40.0%) | .873 |
| Peripheral vascular disease (No.) | 74(17.3%) | 39(14.4%) | .304 |
| Creatinine >2 mg/dL (No.) | 25(5.8%) | 35(13%) | .001 |
| Chronic lung disease (No.) | 38(8.9%) | 24(8.9%) | .999 |
| Acute myocardial infarction <1 wk (No.) | 44(10.3%) | 19(7%) | .144 |
| Congestive heart failure (No.) | 68(15.9%) | 47(17.4%) | .589 |
| Left main stenosis >50% (No.) | 120(28.2%) | 79(29.3%) | .756 |
| Three-vessel disease (No.) | 399(93%) | 254(93.7%) | .710 |
| Ejection fraction ≤35% (No.) | 33(7.7%) | 21(7.7%) | .992 |
| Emergency operation (No.) | 28(6.5%) | 21(7.8%) | .528 |
| Preoperative intra-aortic balloon pump (No.) | 26(6.1%) | 16(5.9%) | .932 |
| Previous cerebrovascular disease (No.) | 41(9.6%) | 23(8.5%) | .632 |
| Carotid disease (No.) | |||
| Moderate (50%–70% stenosis) | 67(15.6%) | 54(19.9%) | .142 |
| Severe (>70% stenosis) | 10(2.3%) | 8(2.9%) | .613 |
TABLE 2. Operative data
| Variable | No-touch group (n = 429) | Side-clamp group (n = 271) | P value |
|---|---|---|---|
| Epiaortic ultrasonography (No.) | 21(4.8%) | 52(19%) | <.0001 |
| Grafts/patient | .009 | ||
| Mean | 2.5 ± 0.6 | 2.6 ± 0.6 | |
| Range | 2–4 | 2–5 | |
| Atherosclerotic aorta (No.) | 75(17.4%) | 14(5.1%) | <.0001 |
| Aortic grading (No.) | |||
| Moderate atherosclerosis | 45(10.4%) | 3(1.1%) | <.0001 |
| Severe atherosclerosis | 26(6.1%) | 0(0%) | .0009 |
| Use of left ITA (No.) | 427(99.5%) | 269(99.2%) | .642 |
| Use of right ITA (No.) | 245(57.1%) | 83(30.6%) | <.0001 |
| Use of bilateral ITA (No.) | 236(55.3%) | 83(30.6%) | <.0001 |
| Use of RA (No.) | 174(40%) | 8(2.9%) | <.0001 |
| Use of RGEA (No.) | 27(6.3%) | 1(0.4%) | <.0001 |
| Use of saphenous vein graft (No.) | 5(1.2%) | 261(96.7%) | <.0001 |
| T grafts (No.) | 213(49.7%) | 30(11.1%) | <.0001 |
| Sequential grafting (No.) | 155(36.2%) | 28(10.3%) | <.0001 |
| Bilateral ITA cross configuration (No.) | 146(34%) | 58(21.4%) | <.0001 |
| Grafts to posterolateral territory (No.) | 388(90.4%) | 236(87.1%) | .164 |
| Target coronary vessel (No.) | |||
| Left anterior descending | 429(40%) | 271(40%) | |
| Diagonal | 101(9.4%) | 58(8.6%) | .510 |
| Circumflex | 354(33.4%) | 156(23%) | <.0001 |
| Right | 31(2.8%) | 34(5%) | .182 |
| Posterior descending | 157(14.6%) | 158(23.3%) | <.0001 |
Operative mortality and morbidity
Early mortality was lower in the no-touch group, although the difference did not reach statistical significance (Table 3). The EuroSCORE-predicted mortalities were 4.8% ± 8% (95% CI 0.055-0.073) and 4.3% ± 6% (95% CI 0.049-0.054) in the no-touch and side-clamp groups, respectively (P = .326). The modes of death were cardiac-related (5 patients), sepsis (4 patients), acute abdominal ischemia (3 patients, of whom acute mesenteric event was diagnosed during laparotomy in 2), and acute aortic dissection (1 patient).
TABLE 3. Early results
| Variable | No-touch group (n = 429) | Side-clamp group (n = 271) | Total (n = 700) | P value |
|---|---|---|---|---|
| Hospital stay (d) | .166 | |||
| Mean ± SD | 5.5 ± 4.2 | 5.9 ± 3.6 | 5.7 ± 4 | |
| Range | 0–20 | 0–24 | 0–24 | |
| Early death (No.) | 9(2.1%) | 7(2.6%) | 16(2.3%) | .679 |
| Myocardial infarction (No.) | 6(1.4%) | 4(1.5%) | 10(1.5%) | .936 |
| Atrial fibrillation (No.) | 62(14.8%) | 39(14.8%) | 101(14.8%) | .991 |
| Re-exploration for bleeding (No.) | 5(1.2%) | 5(1.9%) | 10(1.5%) | .448 |
| Renal failure* (No.) | 16(3.8%) | 16(6.0%) | 32(4.7%) | .166 |
| Sternal infection (No.) | ||||
| Deep | 4(0.9%) | 1(0.4%) | 5(0.7%) | .388 |
| Superficial | 10(2.3%) | 15(5.5%) | 25(3%) | .026 |
| Major neurologic event (No.) | 1(0.2%) | 6(2.2%) | 7(1.0%) | .010 |
| Neurologic event or death (No.) | 10(2.4%) | 13(4.9%) | 23(3.3%) | .072 |
* Defined as serum creatinine level 2 mg/dL or more, or postoperative increase of 1 mg/dL. |
The incidence of major neurologic complications was significantly higher in the side-clamp group (1/429 or 0.2% vs 2.2% or 6/271, P = .01; Table 3). The types and distribution of neurologic deficits were as follows: permanent (stroke) in 5 patients and prolonged reversible ischemic neurologic deficit in 2 patients, in the right cerebral hemisphere in 4 patients and the left cerebral hemisphere in 3 patients. Two patients who had strokes had been regarded by the surgeon as being free of aortic disease, and in 3 patients with stroke the aorta was considered mildly involved.
Prediction of neurologic complications and mortality
The surgical technique including use of partial aortic clamp (OR 28.5, 95% CI 0.22-333, P = .009,) was identified as independent predictor for neurologic complications. Peripheral vascular disease (P = .068), history of cerebrovascular disease (P = .074), and diabetes (P = .072) tended to predict neurologic complications (Table 4). Emergency operation (OR 8.7, 95% CI 1.99-38.3, P = .004) and renal dysfunction (OR 11.5, 95% CI 3.02-43.8, P < .0001) were identified as correlates of mortality (Table 4). The use of partial aortic clamping tended to predict the occurrence of neurologic complications or mortality (OR 2.55, 95% CI 0.96-6.75, P = .060).
TABLE 4. Logistic regression: Independent risk factors for stroke, death, and combined outcome of stroke or death
| Variable | Stroke | Death | Stroke or death | ||||||
|---|---|---|---|---|---|---|---|---|---|
| OR | 95% CI | P value | OR | 95% CI | P value | OR | 95% CI | P value | |
| Age | 1.05 | 0.93–1.18 | .397 | 1.06 | 0.99–1.15 | .081 | 1.06 | 1.00–1.13 | .039 |
| Sex | 6.65 | 0.60–73.5 | .122 | 0.51 | 0.14–1.82 | .303 | 0.95 | 0.33–2.72 | .929 |
| Diabetes | 6.89 | 0.60–56.6 | .072 | 0.92 | 0.26–3.23 | .903 | 1.38 | 1.00–3.77 | .520 |
| Hypertension | — | — | — | 1.40 | 0.36–5.47 | .621 | 2.21 | 0.66–7.43 | .197 |
| Peripheral vascular disease | 6.16 | 0.87–43.5 | .680 | 1.26 | 0.32–4.95 | .731 | 1.87 | 0.64–5.37 | .244 |
| Renal failure | 1.19 | 0.04–31.3 | .913 | 11.5 | 3.02–43.8 | <.0001 | 7.55 | 2.39–23.8 | .001 |
| Chronic lung disease | 0 | 0.00–5.40 | .943 | — | — | — | — | — | — |
| Cerebrovascular disease | 5.56 | 0.84–36.4 | .074 | 2.06 | 0.36–11.7 | .412 | 2.77 | 0.81–9.45 | .102 |
| Atrial fibrillation | 0 | 0.00–1.30 | .926 | 1.3 | 0.22–7.47 | .762 | 0.77 | 0.15–3.95 | .761 |
| Congestive heart failure | 1.59 | 0.13–19.1 | .712 | 1.1 | 0.20–5.83 | .906 | 1.04 | 0.27–4.02 | .947 |
| Left main disease | 3.86 | 0.68–21.7 | .126 | 0.41 | 0.10–1.62 | .208 | 0.94 | 0.34–2.57 | .913 |
| Emergency operation | 0 | 0.00–1.40 | .931 | 8.74 | 1.99–38.3 | .004 | 3.81 | 1.02–14.1 | .045 |
| Operative variables | |||||||||
| Use of bilateral ITA | 2.52 | 0.38–16.7 | .338 | 2.24 | 0.63–7.89 | .209 | 2.06 | 0.75–5.65 | .157 |
| Use of side-clamp | 28.5 | 2.27–333.3 | .009 | 1.04 | 0.30–3.55 | .939 | 2.55 | 0.96–6.75 | .600 |
Discussion
The findings of this study suggest that avoiding partial aortic clamping enhances the neuroprotective effect of OPCAB. This benefit was reproducible and attained irrespective of the severity of aortic disease or the method of aortic screening. It has been shown that the no-touch technique can be implemented in most OPCAB procedures and that routine use of arterial conduits for this purpose is feasible.
Refinements in surgical techniques and the advent of tissue stabilizers have markedly reduced blood pressure fluctuations and the subsequent risk of stroke during off-pump displacement of the beating heart.17 Partial aortic clamping, however, remains a potential cause for embolic stroke during OPCAB. Post-OPCAB stroke rates ranging from 0% to 3.3% have been reported.5, 6, 7, 8, 9, 10, 11, 14, 17, 18, 19 This wide range may reflect differences in patient profiles but may also stem from different operative strategies, such as the choice of graft deployment and aortic screening methods.
In this study, the low 1% overall incidence of major neurologic complications stemmed from the differential effect of the no-touch technique. There was 1 neurologic event among the 429 consecutive patients in the no-touch OPCAB group (0.2%). To date, data on the benefit of avoiding partial aortic clamps during OPCAB are sparse; however, our results validate previous reports of low stroke rates in corresponding no-touch OPCAB subgroups (0.5%,5 0.4%14 and 0%20, 21). This consistent reduction in the incidence of stroke below 1% may reflect on the reproducibility of the no-touch technique. Our results should be viewed in with respect to the relatively old age of the patient cohort (Table 1). Preoperative risk factors of stroke—history of cerebrovascular disease,22 peripheral vascular disease,23 diabetes,23 and hypertension,24 and carotid disease—were evenly distributed between the groups. After adjustment for confounding factors, the use of partial aortic clamping was found to be the only independent predictor of stroke, increasing this risk 28-fold. Consistent with previous observations,22, 23 history of cerebrovascular disease, peripheral vascular disease, and diabetes tended to predict stroke.
The 2.2% neurologic event rate observed our side-clamp group is compatible with stroke rates reported after previous OPCAB series.5, 6, 7, 8, 9, 10, 11, 14, 17, 18, 19 In our study, as well as in previous studies of corresponding subgroups, it is likely that certain cases of atherosclerotic aortic disease were undetected and resulted in stroke. Epiaortic ultrasonography has been established as the modality of choice for aortic screening,25 with manual palpation linked to a higher frequency of underdetection. It is apparent that in this study a suboptimal detection rate was achieved (Table 2), because the reported frequency of significantly atheromatous aorta detected in epiaortic ultrasonographic studies ranges from 21% to 62%.25, 26 Epiaortic ultrasonography during OPCAB has been reported to be useful in making the decision to deploy grafts on the ascending aorta and in making adjustments in the location of side-clamps once ultrasonographic findings have been detected.27 This, however, remains a problem considering that the frequency of atherosclerotic anterior wall aortic findings that indicate surgical modifications may reach 35%, and in 25% of patients undergoing OPCAB, revascularization without aortic manipulation may be eventually required.27 Despite the efficacy of epiaortic ultrasonography,25, 26, 27 not all strokes may be prevented by it. The decisions concerning surgical modifications are made on the basis of qualitative ultrasonographic information and are usually based on the surgeon's evaluation; thus the potential for errors is not obviated. The wide range of ultrasonographic detection rates (21%-62%) is a cause of concern,25, 26 and a major limitation is the fact that ultrasonography is not always available. At the time of our study routine, epiaortic ultrasonography was not considered to be the standard of care and was reserved for select high-risk patients. This policy has been apparently applied by many other centers as well.6 Mechanical or suture-based clampless proximal connectors are other options that have been contemplated for reducing the risk of atheroembolism during OPCAB while allowing some degree of aortic manipulation.28 Several concerns, however, have recently been raised. Embolic particulate debris after the use of anastomotic devices is still evident,29 and the safety of these devices remains unresolved after reports of device-related early graft closure.30 No-touch OPCAB may therefore be still the modification of choice once aortic disease has been ultrasonographically detected.
In this study, the term “no-touch grafting” denotes total arterial revascularization. The literature does not offer a clear mandate for routine composite attachment of venous grafts. Despite several exceptions to this rule,19 arterial conduits, arranged in composite or in situ configurations, are usually required for this purpose.5, 16, 20 Our results demonstrate that this strategy can be implemented for most patients undergoing OPCAB.
Several limitations of this study need to be addressed. Under the assumption that failure to detect atherosclerotic aortic plaques resulted in stroke, a comparative study with systematic epiaortic ultrasonography for all patients is warranted. This study is restricted in the ability to detect multiple predictors of neurologic events because only 7 such events occurred in this series. In addition, a comparative prospective randomized trial is required to validate our results. The reproducible results conferred by the no-touch technique, however, remain indisputable. We could not differentiate between the effect of single versus multiple aortic side-clamps on stroke. Relevant issues for further assessment would be the role of newly available clampless proximal anastomotic devices and the effect of no-touch OPCAB on neurocognitive outcomes.
In conclusion, the aortic no-touch OPCAB technique provides superior neurologic outcome irrespective of the aortic screening strategy or the severity of atherosclerotic disease. This technique should be considered whenever technically feasible.
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PII: S0022-5223(04)00872-4
doi:10.1016/j.jtcvs.2004.06.013
© 2005 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.
Volume 129, Issue 2 , Pages 307-313, February 2005
