Asian Cardiovasc Thorac Ann 2003;11:52-57
© 2003 Asia Publishing EXchange Ltd
Stroke in Thoracic Aortic Surgery: Outcome and Risk Factors
Yoshito Kawachi, MD,
Atsuhiro Nakashima, MD,
Yoshihiro Toshima, MD,
Tomokazu Kosuga, MD,
Kenichi Imasaka, MD,
Hiroshi Tomoeda, MD
Department of Cardiovascular Surgery, Clinical Research Institute, National Kyushu Medical Center, Fukuoka, Japan
For reprint information contact: Yoshito Kawachi, MD Tel: 81 92 852 0700 Fax: 81 92 846 8485 email: kawachiy{at}qmed.hosp.go.jp Department of Cardiovascular Surgery, National Kyushu Medical Center, 1-8-1, Jigyohama, Chuo-ku, Fukuoka 810-8563, Fukuoka, Japan.
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ABSTRACT
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The risk factors and the outcome of stroke in thoracic aortic surgery were studied in 127 patients (86 males, 41 females), aged 18 to 84 years (mean, 64 years), operated on between September 1994 and December 2000. There were 29 operations on the ascending aorta, 63 arch, 29 descending, 5 thoracoabdominal, and 1 extraanatomical bypass. Perioperative stroke occurred in 15 patients (12%). The risk factors for stroke were identified as preexisting chronic renal failure and femoral arterial cannulation. Hospital death occurred in 4 of the 15 cases (27%) of stroke and 7 of the 112 cases (6%) without stroke (p < 0.05). There were 18 late deaths during a mean follow-up period of 3.2 years (range, 1 month to 7.2 years). The 3-year survival rates were 43 ± 14% in the stroke patients and 85 ± 4% in the other patients. Actuarial survival, including during hospitalization, was lower in the stroke patients than in the other patients not only among those 70 years or older but also among all the patients (both p < 0.0001). Stroke occurring in thoracic aortic surgery is thus an important risk factor for early and late mortality, particularly in patients 70 years or older.
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INTRODUCTION
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Perioperative stroke is one of the major sources of mortality and morbidity in thoracic aortic surgery.1–7 Neurological complications have been studied predominantly in aortic arch replacement operations performed under deep hypothermic circulatory arrest with or without retrograde cerebral perfusion (RCP) or antegrade selective cerebral perfusion (SCP).1–5,8–11 Stroke occurs in surgery on not only the ascending aorta or aortic arch but also the descending or thoracoabdominal aorta. Few studies have reported the late results of patients who suffered a stroke during thoracic aortic surgery.3,5 We conducted a retrospective analysis of patients who underwent thoracic aortic surgery to determine the predisposing factors and the outcome of perioperative stroke, particularly in the elderly.
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PATIENTS AND METHODS
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Between September 1994 and December 2000, thoracic aortic surgery was performed in 133 consecutive patients at our center. Six patients who died of bleeding or low cardiac output syndrome within 3 days after surgery were excluded because stroke could not be evaluated. The other 127 patients consisted of 86 men and 41 women, aged 18 to 84 years (mean, 64 ± 12 years), including 7 octogenarians.
Demographic and clinical outcome data were entered into a computer database, reviewed, and supplemented as needed from patient records. The pathology and extent of aortic disease are shown in Table 1
. There were 51 cases of nondissecting (primarily atherosclerotic) aneurysm, 44 acute aortic dissection, 29 chronic dissecting aneurysm, and 3 atherosclerotic aneurysm with dissection. Preoperatively, 25 patients had old brain infarction identified by computed tomographic (CT) scan regardless of neurological deficits. Of these, 15 had nondissecting aneurysm, 6 chronic dissecting aneurysm, and 4 acute type A dissection. Another 5 patients had acute ischemic stroke induced by acute type A dissection before surgery.
The surgical approach employed depended on the location of the diseased thoracic aorta. Median sternotomy was used in 88 patients (69%), left thoracotomy in 32 (25%), and median sternotomy with left anterolateral thoracotomy in 7 (6%). Aortic replacement was performed in 118 patients, patch closure of saccular aneurysm in 8, and extraanatomical bypass from the ascending aorta to the abdominal aorta in 1 (Table 2). With respect to the extent of graft replacement, the ascending aorta was replaced in 28 patients (22%), the aortic arch involving at least 1 of the 3 arch vessels in 56 (44%), the descending aorta in 29 (23%), and the thoracoabdominal aorta in 5 (4%). In the cases of aortic arch replacement, arch vessels were reimplanted using separate grafts in 55 patients and en bloc in 1. Concomitant procedures included aortic valve resuspension in 24 patients, elephant trunk graft in 22, redo operation after cardiac or thoracic aortic surgery in 10, aortic root replacement (modified Bentall, Cabrol, or David procedure) in 5, coronary artery bypass grafting in 4, aortic valve replacement in 3, and ventricular septal defect repair in 1. Emergency surgery was performed in 65 patients (51%) within 24 hours of hospital admission or establishment of the diagnosis of aortic rupture, impending rupture, and acute type A dissection. The other patients had elective operations.
All but one procedure involved cardiopulmonary bypass (CPB). Femorofemoral CPB was employed in 23 patients undergoing repair of descending or thoracoabdominal aortic aneurysm. Routine CPB with femoral perfusion, mild hypothermia, and ascending aortic clamping was employed in 3 patients undergoing replacement of the ascending aorta or aortic root. Profound hypothermia was used in 100 patients who underwent aortic arch replacement and open distal or proximal aortic anastomosis, with arterial cannulation during the core cooling period in the femoral artery in 70 cases, ascending aorta in 28, and left subclavian artery in 2. In these patients, after cooling to 20°C bladder temperature, systemic circulation was arrested and cerebral perfusion was started to prevent ischemic brain damage. Antegrade SCP was used in 84 patients; RCP through the superior vena cava was used in 6 patients who underwent ascending aortic replacement; and RCP by the Takamoto method12 (cerebral perfusion with blood returned to the right atrium and the patient in the Trendelenburg position) was used in 10 patients who underwent replacement of the distal arch and proximal descending aorta through the left thoracotomy. During core rewarming, the arterial return line was placed in the aortic graft in 81 cases, ascending aorta in 13, femoral artery in 4, and left subclavian artery in 2.
Our SCP technique involved inserting 1 perfusion cannula each with a balloon of 14F, 12F, and 12F (Fuji Systems, Tokyo, Japan) into the innominate artery, left common carotid artery, and left subclavian artery, respectively, through the aortic lumen. Using a roller pump separated from the systemic circulation, cerebral blood flow was initiated at 250 to 500 mL•min-1 with a blood temperature of 15°C. In RCP through the superior vena cava, perfusion flow was 500 mL•min-1 at 15°C blood temperature. Gelatin-resorcinol-formaldehyde glue (Cardial; Bard Inc., Saint-Etienne, France) was used to treat acute aortic dissection since November 1995.
Perioperative stroke is defined as a new focal neurological deficit, permanent or transient, together with findings of new brain infarction by CT scan. Operative mortality is defined as death occurring within 30 days of operation or before hospital discharge. The outcome of patients who had perioperative stroke was defined by operative mortality and late survival.
Continuous data were expressed as mean ± standard deviation, actuarial determinations as mean ± standard error of the mean, and categorical variables as percentages. All statistical analyses were done using StatView version 5.0 (SAS Institute, Cary, NC, USA). Parameters that were analyzed are listed in Table 3. Categorical variables were compared between 2 patient groups using the chi-squared test with 2 x 2 contingency tables or Fisher’s exact test as appropriate, and continuous variables were compared using Student’s t test. Risk factors that produced p values below 0.20 in the univariate analysis were analyzed by stepwise multiple logistic regression to identify independent predictors of perioperative stroke. Actuarial survival rates were calculated using the Kaplan-Meier method and group comparison of survival was made using the log rank test. Variables are considered statistically significant at p < 0.05.
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RESULTS
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Perioperative stroke occurred in 15 patients (12%), involving 11 permanent (6 hemiplegia and 5 diffuse injury) and 4 transient (2 each of convulsion and hemiplegia) sequelae. No patients suffered permanent impairment of cognitive function. The only incremental risk factor for stroke indicated by univariate analysis was preexisting chronic renal failure (serum creatinine > 1.5 mg•dL-1 or dialysis) (Table 3
). By multiple logistic regression analysis, preexisting chronic renal failure and the site of arterial cannulation were found to be independent predictors of perioperative stroke (p < 0.0005 and p < 0.05, respectively). Stroke occurred in 1 of 28 patients (3.6%) who had ascending aortic perfusion and in 11 of 73 patients (15%) who had femoral arterial perfusion (Table 3).
There were 4 hospital deaths among the 15 cases (27%) of stroke and 7 among the 112 cases (6%) without stroke (p < 0.05). The 116 survivors were followed for an average of 3.2 years (range, 1 month to 7.2 years). Among 18 late deaths, 5 died of pulmonary insufficiency, 4 of sudden death, 3 of sepsis, 2 of a new stroke, and 1 each of cancer, congestive heart failure, senile decay, and intestinal necrosis. Among the 11 stroke survivors, 4 (36%) died of pulmonary insufficiency or sepsis within 1 year after discharge and another died 3.6 years after the operation. These 5 patients were all 70 years or older. Among the 15 cases of stroke, hospital or late death occurred in 7 of 8 patients (88%) 70 years or older and 2 of 7 patients (29%) under 70 years (p < 0.05). In patients 70 years or older, overall mortality was significantly higher in those who had stroke (7/8) than those who did not (11/37) (p < 0.005). In younger patients, there was no significant difference between those with stroke (2/7) and those without (9/75). Actuarial survival, including during hospitalization, of the stroke patients was lower than in the other patients not only among the 70 years or older but also among all the cases (both p < 0.0001) (Figures 1A and 1B). However, there was no significant difference in survival in younger patients. The 3-year survival rate was 81 ± 4% overall, 43 ± 14% in the stroke patients, and 85 ± 4% in patients without stroke.
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Figure 1. Comparison of actuarial survival using the log rank test in (A) all patients and (B) patients 70 years or older.
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DISCUSSION
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Studies with sample sizes of more than 100 cases reported the incidence of neurological complications in thoracic aortic surgery as 4.1% to 23%.1–7,9,10,13–15 These studies showed that increased risks of neurological complications were associated with such factors as older age, emergency operation, atherosclerosis or laminated thrombi in the aorta, aortic arch clamping, replacement of the distal arch, history of cerebrovascular disease, malperfusion of the extremities, preoperative hypotension, preexisting renal failure, approach through a left thoracotomy, pump time, prolonged hypothermic arrest, and lack of cerebral perfusion. It is speculated that neurological complications in thoracic aortic surgery result from cerebral emboli, ischemia, and hemorrhage. The majority of intraoperative strokes are the result of cerebral embolism caused by dislodgment of loose atheromatous plaques or mural thrombi.3,5,11,16 Our patient who underwent extraanatomical bypass from the ascending aorta to the abdominal aorta without CPB had stroke. This procedure involved temporary side clamping of the ascending aorta and permanent occlusion of the proximal descending aorta. The stroke was probably induced by dislodgment of the atheromatous plaque during aortic manipulation and aortic clamping or occlusion. Air embolism induced by CPB or improper deairing of the aortic arch and arch vessels in aortic arch surgery also may cause stroke.
Although our sample size may not be adequate for definitive analysis, there is strong evidence that preexisting chronic renal failure and the site of arterial cannulation (namely, the femoral artery for retrograde systemic perfusion) are independent predictors of perioperative stroke. While chronic renal failure might be the consequence of atherosclerosis in arteriosclerotic patients, Okita’s team5 also showed preexisting renal failure as one of the significant risk factors of stroke in surgery for arteriosclerotic aneurysm of the aortic arch. The aim of antegrade systemic perfusion is to prevent scattering of debris by the blood jet in an atheromatous thoracoabdominal aorta or malperfusion through a dissected aorta with an open false lumen.16,17 Westaby and colleagues11 reported a low incidence of cerebral embolism caused by antegrade systemic perfusion through proximal aortic cannulation compared with retrograde systemic perfusion through femoral cannulation.
We found poor early and late survival of the stroke patients, particularly those 70 years or older. Although it is well known that stroke is a major factor of operative mortality in thoracic aortic surgery, there are few reports on the late survival of stroke patients. These studies showed that the long-term survival of these patients was markedly decreased compared with those without stroke.3,5 However, they did not analyze the effect of age.
Three methods of cerebral protection are currently used: hypothermic circulatory arrest, antegrade SCP, and RCP. Recent reports suggest that neurological complications are not directly related to the method of cerebral protection used, except for prolonged deep hypothermic circulatory arrest with or without RCP.1–4,6–9,1315 We prefer antegrade SCP because it offers reliable cerebral protection regardless of perfusion time.16
The following steps are taken by our center to minimize the risk of intraoperative stroke: preoperative evaluation and treatment of intra- and extracranial occlusive arterial disease, detection of atherosclerosis by intraoperative epiaortic echocardiography, utilization of ascending aortic cannulation for antegrade systemic perfusion whenever possible, the use of antegrade SCP with hypothermia, and careful and meticulous manipulation of the thoracic aorta and aortic arch vessels.
Temporary neurological dysfunction has been reported in thoracic aortic surgery, such as postoperative confusion, agitation, delirium, prolonged obtundation, or transient parkinsonism without any localizing neurological signs and abnormal brain CT findings.2 We have noticed occasionally such signs in patients needing prolonged ventilatory support after cardiovascular surgery. Because these patients usually recover before discharge and return to an active social life after discharge, we have paid little attention to temporary neurological dysfunction. However, temporary dysfunction is one of the important postoperative neurological complications for assessing the reliability of the cerebral protection technique used.
In conclusion, we found that stroke occurring in thoracic aortic surgery is an important risk factor for early and late mortality, particularly in patients 70 years or older, and the independent risk factors for stroke are preexisting chronic renal failure and retrograde systemic perfusion through femoral arterial cannulation.
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ABSTRACT
INTRODUCTION
