01 сентября 2001 00:00
Individualized surgical strategy for the reduction of stroke risk in patients undergoing coronary artery bypass grafting
Background . This study was designed to evaluate the efficacy of a protocol of systematic screening of the ascending aorta and internal carotid arteries and individualization of the surgical strategy to the ascending aorta and internal carotid arteries status in reducing the stroke incidence among patients undergoing coronary artery bypass grafting.
Methods . On the basis of a pre- and intraoperative screening of the ascending aorta and internal carotid arteries, 2,326 consecutive patients undergoing coronary artery bypass grafting were divided in low, moderate, and high neurologic risk groups.
Results . The incidence of perioperative stroke
Conclusions . The described strategy allows a low rate of perioperative stroke
Postoperative stroke represents one of the most severe complications of coronary artery operations and, as a result of the progressive aging of the population referred for cardiac operations, it will probably tend to increase in frequency in the near future. For this reason, the identification of the surgical strategies that can allow a reduction of postoperative neurologic events
In this report we analyze our 4 years of prospective experience with the use of an integrated protocol aimed at reducing the incidence of cerebrovascular events in patients undergoing coronary artery bypass procedures by means of the systematic screening of the aorta and internal carotid arteries and adoption of dedicated surgical strategies in case of atherosclerotic disease of one or both vascular districts.
Patients and methods
This study was prospectively started in October 1993 to evaluate the possibility of reducing the incidence of cerebrovascular complications in patients undergoing coronary artery bypass grafting by means of a protocol of systematic screening of the ascending aorta and the internal carotid arteries and modification of the surgical strategy on the basis of the status of these two vascular districts.
For the purpose of this report, data collection ended in January 1997. All cases submitted to isolated coronary artery bypass (ie, not associated with any other cardiac procedures) on elective or urgent basis at our institution in this time frame were considered.
Emergency cases were not included due to the impossibility of performing a complete preoperative evaluation of the carotid arteries.
During the study period no major modifications in the surgical and anesthesiologic technique were adopted.
Preoperative and intraoperative evaluation
Following a protocol in use at our Institution since 1990, all the 2,326 patients were submitted to the following tests:
Extracranic carotid arteries were evaluated by color flow duplex scanning study;
Patients were then classified in four groups: no disease, slight, moderate, or severe carotid artery disease (see ). In patients with severe stenosis a preoperative carotid angiography was always performed.
Evaluation of the ascending aorta
To identify the presence of atherosclerotic lesions of the ascending aorta the preoperative chest roeutgengram and the coronary angiography were carefully evaluated. In addition, intraoperative digital palpation of the aorta was always performed following a described methodology  and the patients were classified in four groups according to the scale proposed by Mills and Everson  (see ): no disease, mild, moderate, or severe ascending aorta atherosclerosis. In 715 patients operated during the last part of the series intraoperative ultrasonographic examination of the ascending aorta was also performed and the atherosclerotic lesions were classified according to the criteria described by Wareing and coauthors  (see ).
Patients with a clinical history of peripheral vasculopathy were also submitted to examination of the iliac and common femoral arteries following the described
On the basis of this preoperative assessment patients were divided in three categories of neurologic risk (in case of concomitant aortic and carotid disease of different gravity, classification was based on the most severe lesion): Patients at low risk: patients with no or slight internal carotid artery disease and with no or slight disease of the ascending aorta. Overall, this group included 1,602 of the 2,326 patients (68.8%). Patients at moderate risk: patients with moderate internal carotid artery stenosis or moderate atherosclerosis of the ascending aorta. In total 380 patients were assigned to this group (16.3% of the overall population). In particular, moderate carotid artery stenosis was present in 239 patients (10.2% of the total) and moderate ascending aorta atherosclerosis in 116 (4.9%); in 25 patients (1.0%) the two pathologies coexisted. Patients at high risk: patients with severe internal carotid artery stenosis (either asymptomatic or symptomatic) or severely atherosclerotic ascending aorta. Globally 344 patients (14.7% of the total population) were assigned to this category. In particular, severe carotid disease was present in 196 patients (8.4%), severe aortic disease in 137 (5.8%), and the two conditions coexisted in 11 patients (0.4%).
The preoperative clinical and angiographic characteristics of the patients of the three categories are shown in . [Table 1]
All the operations were performed by five surgeons using standardized techniques. Patients of the different categories were treated using different surgical strategies.
Patients at low risk
After median sternotomy and pericardiotomy, cardiopulmonary bypass was established by cannulating the right atrium and the ascending aorta. Normothermic systemic perfusion was used and myocardial protection was achieved by intermittent isothermic anteretrograde blood cardioplegia; patients were actively rewarmed if their nasopharingeal temperature fell below 34°C and mean nasopharingeal temperature in this group was 36.3 ± 0.8°C. Mean arterial pressure during cardiopulmonary bypass was maintained between 50 and 70 mm Hg; volume infusion or vasopressors (phenylephrine) were used in case of hypotension. Proximal and distal anastomoses were always performed during a single period of aortic cross-clamping.
Patients at moderate risk
These patients were also operated using the conventional technique described, however, due to the reported concerns on the neurologic safety of normothermic cardiopulmonary bypass and retrograde cardioplegia   , patients of this group were always operated using mildly hypothermic systemic perfusion (28°C) and isothermic intermittent antegrade blood cardioplegia; mean nasopharingeal temperature in this group was 27.4 ± 0.9°C. In cases with moderate aortic disease care was paid to avoid the atherosclerotic areas during cannulation and cross-clamp.
Patients at high risk
We adopted dedicated surgical strategies for these patients. In particular, in patients with severe monolateral internal carotid artery stenosis simultaneous carotid endoarterectomy and coronary artery bypass was performed in case of unstable angina (n = 91), whereas a staged strategy (carotid endoarterectomy performed before myocardial revascularization) was adopted in patients with stable angina (86 patients). During simultaneous operations the carotid endoarterectomy was always carried out before median sternotomy; for both concomitant and staged procedures an intraluminal carotid shunt was used and myocardial revascularization was performed in condition of hypothermic systemic perfusion. Among patients who underwent staged operations the mean interval between the carotid and coronary operations was 14.9 ± 8.7 days. Patients with bilateral carotid artery stenosis and stable angina (n = 15) were treated by carotid endoarterectomy of the most diseased site followed by combined operation on the other carotid and the coronary arteries (performed within 2 to 3 weeks), whereas the patients with bilateral carotid disease and unstable cardiac symptoms (n = 4) were treated by simultaneous carotid endoarterectomy of the most severe lesion and coronary artery bypass, followed after 2 to 3 weeks by surgical treatment of the other carotid artery.
In patients with severely atherosclerotic ascending aorta we adopted
Main operative data of the different groups are reported in . [Table 2] As a direct consequence of our policy of privileging the reduction of the neurologic risk at expense of the completeness of the myocardial revascularization,
Evaluation of postoperative neurologic complications
Postoperative neurologic complications were classified according to the definitions given in the ; patients with transient ischemic attacks were not considered in the data analysis.
Following a protocol in use at our institution since 1990, a neurologic evaluation was always performed by a cardiac anesthesiologist (blinded to the pre- and intraoperative evaluation) at the moment of the awakening of the patient from the anesthesia. In cases of neurologic abnormalities a complete neurologic examination was performed by a consultant neurologist immediately after the onset of symptoms, 24 hours later, at regular interval of 1 or more days (depending on the clinical status), and at discharge. In case of stroke the neurologic outcome was assessed using the Glasgow Outcome Scale  . The Glasgow Outcome score was assigned in concomitance with the neurologic evaluations by a neurologist and a cardiac anesthesiologist; disagreements were resolved by consensus after a common reevaluation. In patients with clinical evidence of neurologic complications of any type brain computed tomographic scans were performed immediately after the evidence of symptoms, 24 to 48 hours later, after any change in the neurologic status, and the day before discharge. All scans were performed prospectively and independently evaluated by two expert neuroradiologists; disagreements were resolved by common reexamination. In case of computed tomographic evidence of recent stroke, lesion size was measured by a ruler to the nearest half millimeter in two dimensions and multiplied by the thickness of the slice following a previously described methodology   . For multiple or irregularly shaped lesions the sum of the single ischemic areas was calculated. All neurologic measurements were prospectively entered in a computerized database.
All patients were regularly submitted to clinical examination at our institution 1 and 6 months after operation and then every year thereafter. A stress myocardial scintigraphy was obtained in all patients 6 months postoperatively and every year thereafter. In case of clinical or instrumental suspect of residual myocardial ischemia or angina recurrence, reangiography was always proposed to the patient.
Data are expressed as mean value ± 1 standard deviation. For statistical analysis qualitative data were compared using the <Рисунок: chi> 2 test with Bonferroni's correction. Parametric quantitative data were compared
Mortality and morbidity
Mortality and morbidity data of the patients of the different risk categories are summarized in . [Table 3]
No significant difference in mortality was found between the three groups; renal insufficiency was the only postoperative complications significantly more frequent
Overall, 27 patients suffered a perioperative stroke (1.1%).
The mean Glasgow Outcome Scale score and the computed tomographic extension of the brain lesion were similar in the three risk categories ( p = not significant).
The difference in incidence of intraoperative stroke between patients with aortic and carotid disease was statistically significant ( p < 0.01), whereas no differences was found with regard to the postoperative events.
No cases of perioperative stroke were reported among patients who underwent simultaneous
The rate of freedom from clinical or instrumental angina recurrence and cardiac death was significantly higher
In 1993 we started this prospective study with the aim of evaluating the possibility of reducing the incidence of neurologic events in patients undergoing isolated coronary artery bypass grafting by means of a protocol of systematic pre- and intraoperative evaluation of the aorta and the carotid arteries and adoption of dedicated surgical strategies in cases of severe atherosclerosis of one or both vascular districts. Using this approach we achieved a 1.0% global stroke incidence and a rate of cerebrovascular complications
In fact, Roach and coauthors  in a recent large prospective multicenter trial found that perioperative cerebrovascular accidents occurred in 7.8% of patients with carotid disease versus 2.5% of cases without this characteristic and the Buffalo Cardiac Cerebral Study Group estimated a 6.01 odds ratio for postoperative stroke in patients with carotid stenosis <Рисунок: GE> 50%  . Likewise, McKhann and colleagues  reported perioperative cerebrovascular accidents in 15.5% of their patients in whom a carotid bruit was identified preoperatively and Reed and associates  showed
A limitation of our study relies in the method used to evaluate the ascending aorta. In the majority of our patients the assessment of the aortic status was performed by intraoperative palpation, a technique that has already been shown to be quite insensitive in the demonstration of ascending aorta atherosclerosis   . In fact, when analyzing the neurologic outcome
The technical solutions that we applied have been extensively described and are part of the knowledge of all cardiac surgeons; however, we concentrate our effort on the careful evaluation of each case and on the systematic individualization of the surgical approach to the clinical and anatomic condition of every single patient. In this perspective some patients at high risk were treated using integrated techniques (surgical and percutaneous interventions) and, more in general, the completeness of surgical revascularization (once that the left anterior descending was protected by a mammary graft) was judged less important that the reduction of the neurologic risk. As a consequence, patients
Our policy in dealing with combined monolateral carotid and coronary disease was to adopt simultaneous carotid endoarterectomy and myocardial revascularization in patients with unstable angina and a staged procedure (the carotid endoarterectomy performed before the coronary revascularization) in patients in more stable cardiac conditions. Patients with concomitant bilateral carotid artery stenosis and stable angina were treated by carotid endoarterectomy of the most diseased site followed by combined operation on the other carotid and the coronary arteries, whereas the patients with bilateral carotid disease and unstable cardiac symptoms were treated by simultaneous carotid endoarterectomy of the most severe lesion and coronary artery bypass, followed by surgical treatment of the other carotid artery.
This approach allowed a safe and effective treatment of concomitant carotid and coronary disease, leading to acceptable rates of perioperative stroke and myocardial infarction in all groups of patients .
In conclusion, our experience demonstrates that it is possible to achieve a low rate of perioperative cerebrovascular complications
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