Stroke and ON-Pump Coronary Artery Bypass Grafting. Should We Change to OFF-Pump? Our Experience from the North of Jordan.
aorta, cardiopulmonary bypass, coronary artery disease, stroke
E Hijazi. Stroke and ON-Pump Coronary Artery Bypass Grafting. Should We Change to OFF-Pump? Our Experience from the North of Jordan.. The Internet Journal of Cardiovascular Research. 2008 Volume 7 Number 1.
PRINCIPLES: Stroke is a well known complication after coronary artery bypass grafting (CABG) using cardiopulmonary bypass (CPB). We were interested in reviewing our experience with on-pump coronary artery bypass grafting, to evaluate its neurologic dysfunction and its impact on patient management. And to ask a question that recently applied. Should
Coronary artery bypass grafting in the late 1960s was first performed without the use of cardiopulmonary bypass (CPB) . But after the use of CPB and cardioplegic arrest this technique was largely abandoned . With the use of cardiopulmonary bypass neurologic dysfunction is well documented as an associated complication of cardiac surgery . Cerebral injury occurs in two distinct forms, and become an important cause of morbidity and mortality after open heart surgery . Stroke, as devastating complication occurs in 3% of patients undergoing CABG . Soon after open heart surgery using cardiopulmonary bypass (CPB), cognitive dysfunction, occurs in as many as 80% of patients and persists in one fourth of these patients six months after surgery and only by detailed neuropsychologic testing can be detected [4,6,7]. Many factors participate in the pathogenesis of cerebral injury and cognitive dysfunction after cardiac surgery, but there is increasing evidence that multiple microemboli arising from the ascending aorta, the heart chambers, or the bypass circuit are the primary pathophysiologic mechanisms producing diffuse ischemic cerebral injury . Cardiopulmonary bypass requires cannulation and cross-clamping of the ascending aorta, which per se may dislodge atheromatous macroemboli, leading to stroke . Cardiopulmonary bypass is a well known source that generates microemboli and increases the permeability of the blood-brain barrier which may adversely affect cognitive function [10,11].
Patients and Methods
1050 consecutive patients who were undergoing coronary artery bypass grafting (CABG) from May 5, 2003, to December 31, 2007, were enrolled in this retrospective study. Our cardiac center is a new one in the north since May 5, 2002. All patients had undergone conventional CABG using a left internal mammary artery (LIMA) graft with different surgeons. Stroke was defined as any new permanent global or focal neurological deficit. Stroke was first detected by cardiac surgeon immediately after extubation (early) or within 5-6 day in the hospital (late), then neurologist will be consulted, and in the majority of patients they were confirmed by CT head scan. Patients having cardiac valve surgery, ASD (atrial septal defect) repair, LVEF (left ventricular ejection fraction) <0.40, and undergoing repeat CABG surgery were excluded. Mortalities not related to neurological complications were excluded. Twenty seven patients with severe carotid artery disease were excluded from the study as they were transferred to other cardiac center for combined surgery with carotid endarterectomy by vascular surgeons as a complex case. Patients with incomplete intraoperative or postoperative data from medical files were excluded from study.
Stroke occurred in 19 patients (1.81%). Fifteen of these cases (78.95%) discovered at first day post operation in the ICU. Four of them developed stroke in the ward after they were discharged from the ICU (21.05%) 2nd-3rd day post operation. All of these patients were ≥ 65 years old. Brain CT-scan was done in nine patients. Eleven of the 19 patients with stroke had moderate carotid artery disease and history of TIA (transient ischemic attacks) (57.89%). The patients with severe carotid artery disease transferred to other cardiac center for combined surgery with carotid endarterectomy by vascular surgeons as complex cases and were excluded from the study. Thirteen of the 19 patients who developed stroke were female (68.42%). Ten of these female patients were diabetic. Four of these female patients died in the hospital. Six of the 19 patients who developed stroke were male (31.58%). Five of them were diabetic. Two of these patients died in the hospital. The overall mortality related to stroke from the total number of patients in this study was (0.57%). The mortality in the stroke group (n=19) was (31.57%). Total diabetic patients who developed stroke were 15 patients (8.24%) from the total diabetic number of patients (n= 182).
Stroke is a well known and unwanted complication after coronary artery bypass grafting (CABG) using cardiopulmonary bypass (CPB) . With the use of cardiopulmonary bypass, we are facing evidence suggesting increase in morbidity associated with coronary artery bypass grafting (CABG) surgery . Stroke after coronary bypass grafting is usually embolic and related to CPB, manipulation of the aorta during cannulation, or surgical . Bowles, et al  have demonstrated a significant reduction in the number of microemboli detected by transcranial Doppler ultrasonography (TCD), as they comparing off-pump coronary artery bypass grafting (OPCAB) with on-pump CABG (coronary artery bypass grafting using CPB), they noticed a reduction in the stroke rate in patients undergoing off-pump coronary artery bypass. But they believed that true clinical significance of this dramatic reduction in cerebral microemboli, however, remains to be determined.
From the randomized controlled trials (RCTs)  available evidence with respect to occurrence of stroke and postoperative neurocognitive dysfunction does not unequivocally show that OPCAB is better than conventional CABG (on-pump CABG) [14,17-31]. Postoperative stroke after OPCAB may be related to aortic manipulation during construction of the proximal anastomoses that requires the use of a side-biting clamp . Recently in off-pump surgery the non-touch technique of the ascending aorta, which avoids intraoperative dislodgment of the atheromatous macroemboli from the atherosclerotic aorta into the cerebral circulation, may improve neurologic outcomes after OPCAB . Sedrakyan, et al  in their meta-analysis of systematically reviewed trials, concluded that off-pump CABG is associated with reduced risk of stroke, AF and infections as compared with CABG with CPB, but they believed that evidence should be generalized taking in consideration randomized controlled trial (RCT) enrollment limitations, drawbacks related to training requirements, propensity to perform fewer grafts and likely reinterventions after off-pump surgery. Lev-Ran, et al  included a total of 700 consecutive patients undergoing multiple-vessel off-pump coronary artery bypass grafting between 2000 and 2003. They compared 429 patients undergoing aortic no-touch technique with 271 patients in whom partial aortic clamps were applied. The aorta was evaluated with manual palpation, and screened by epiaortic ultrasonography which was used selectively. They concluded that 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. They recommended this technique whenever technically feasible. Kapetanakis, et al  from January 1998 to June 2002, enrolled 7,272 patients underwent isolated CABG surgery through three levels of aortic manipulation: full plus tangential (side-biting) aortic clamp application (on-pump surgery; n = 4,269), only tangential aortic clamp application (OPCAB surgery; n = 2,527) or an “aortic no-touch” technique (OPCAB surgery; n = 476). Their result showed a significant association for postoperative stroke correspondingly increasing with the extent of aortic manipulation was demonstrated by the univariable analysis (cerebrovascular accidents (CVA) incidence respectively increasing from 0.8% to 1.6% to a maximum of 2.2%, p < 0.01). In the logistic regression model, patients who had a full and a tangential aortic clamp applied were 1.8 times more likely to have a stroke versus those without any aortic manipulation (95% confidence interval: 1.15 to 2.74, p < 0.01) and 1.7 times more likely to develop a postoperative stroke than those with only a tangential aortic clamp applied (95% confidence interval: 1.11 to 2.48, p < 0.01). They concluded that aortic manipulation during CABG is a contributing mechanism for postoperative stroke. The incidence of postoperative stroke increases with increased levels of aortic manipulation.
As we observed from our study we found that female sex was independently associated with stroke, but this finding was observed before in other studies [39-46]. Prior neurological event, carotid artery stenosis, diabetes mellitus, and advanced age have been found in many studies to increase susceptibility to perioperative stroke, possibly by identifying individuals with widespread cerebrovascular disease, impaired cerebral blood flow, and/or increased susceptibility to atheroembolism or thromboembolism [39-49]. Atrial fibrillation was observed as transient due to electrolyte disturbances, the heart rate returned to sinus after electrolyte correction. Atrial fibrillation is a frequent complication of cardiac surgery that has been reported to increase the risk of perioperative stroke in some, but not all, studies [39-46]. Hogue, et al  found that an equally important explanation may be the strong interaction they observed between postoperative atrial fibrillation combined with low cardiac output syndrome and delayed stroke, an interaction that has not been reported previously and because both complications are associated with cardiac thrombus formation and cerebral hypoperfusion, aggressive therapy may be beneficial for patients with both conditions. Unfortunately epiaortic ultrasound of the ascending aorta was not performed to evaluate for atheromatous disease. The finding that ascending aorta atherosclerosis was an independent predictor of delayed strokes suggests that risk of stroke associated with this condition may result from mechanisms other than direct atheroembolism. In addition to being a potential cause of cerebral embolism, ascending aorta atherosclerosis may be a marker of widespread atherosclerosis of the aortic arch and cerebral vessels [46,50-58].
Limitations of the Study
This is a retrospective nonrandomized study in a new cardiac surgery center, as well as we are in the starting period in cardiac surgery in the north of Jordan, our cases are more selective. Inspite of the fact that the quality of patients in the recent years and the improvement of invasive cardiology techniques and the experience of cardiologists, leaving us without a wide range of selections. Carotid artery ultrasound was performed in 45.80% of patients ≥60 years old (not routinely) and the prevalence of carotid artery disease could have been underestimated. Epiaortic ultrasound was not available to evaluate the ascending aorta for atheromatous disease. Detailed preoperative neurological assessment was not performed in our patients. We could not find a clear cut answer for the question if we should change to off-pump, many of these studies going toward off-pump, we think a prospective randomized study with a large number of patients will give us a proper answer.
Female sex, diabetic patients and patients with previous transient ischemic attacks and significant carotid artery stenosis are associated with increased the risk of stroke and in-hospital mortality. The literature does not offer a clear answer about the common question that recently applied -Should We Change to OFF-Pump? The proper answer would come from one surgeon with a prospective randomize trial.