Cerebrovascular accidents after cardiac surgery: an analysis of CT scans in relation to clinical symptoms

Toward stroke-free coronary surgery: The role of the anaortic off-pump bypass technique

Surgical coronary revascularization remains the preferred strategy in a significant portion of patients with coronary artery disease due to superior long-term outcomes. However, there is a significant risk of perioperative neurologic injury that has influenced guideline recommendations. These complications occur in 1%-5% of patients, ranging from overt neurologic deficits with permanent disability, to subtle cerebral defects noted on neuroimaging that may result in slow cognitive and functional decline. The primary mechanism by which these events occur is thromboembolism from manipulation of the ascending aorta. This occurs during cardiopulmonary bypass, aortic cross-clamping, and partial occlusion clamping (side clamp). Elderly patients and patients with aortic atheroma are, therefore, at significantly increased risk. Initial surgical techniques addressed this by aggressively debriding or replacing the ascending aorta during coronary artery bypass grafting (CABG). Strategies then moved toward minimizing aortic manipulation through pump-assisted beating heart surgery and off-pump surgery with partial occlusion clamping or proximal anastomosis devices. Finally, anaortic off-pump CABG aims to avoid all manipulation of the ascending aorta through advanced off-pump grafting techniques combined with in situ and composite grafts. This has been demonstrated to result in the greatest reduction in risk. Establishing successful anaortic off-pump CABG programs requires subspecialization and focused interest groups dedicated to advancing CABG outcomes.

Perioperative Stroke

PURPOSE OF REVIEW

This review overviews perioperative stroke as it pertains to specific surgical procedures.

RECENT FINDINGS

As awareness of perioperative stroke increases, so does the opportunity to potentially improve outcomes for these patients by early stroke recognition and intervention. Perioperative stroke is defined to be any stroke that occurs within 30 days of the initial surgical procedure. The incidence of perioperative stroke varies and is dependent on the specific type of surgery performed. This chapter overviews the risks, mechanisms, and acute evaluation and management of perioperative stroke in four surgical populations: cardiac surgery, carotid endarterectomy, neurosurgery, and non-cardiac/non-carotid/non-neurological surgeries.

Early Versus Delayed Stroke After Cardiac Surgery: A Systematic Review and Meta-Analysis

Background

Although it is traditionally regarded as a single entity, perioperative stroke comprises 2 separate phenomena (early/intraoperative and delayed/postoperative stroke). We aimed to systematically evaluate incidence, risk factors, and clinical outcome of early and delayed stroke after cardiac surgery.

Methods and Results

A systematic review (MEDLINE, EMBASE, Cochrane Library) was performed to identify all articles reporting early (on awakening from anesthesia) and delayed (after normal awakening from anesthesia) stroke after cardiac surgery. End points were pooled event rates of stroke and operative mortality and incident rate of late mortality. Thirty‐six articles were included (174 969 patients). The pooled event rate for early stroke was 0.98% (95% CI 0.79% to 1.23%) and was 0.93% for delayed stoke (95% CI 0.77% to 1.11%; P=0.68). The pooled event rate of operative mortality was 28.8% (95% CI 17.6% to 43.4%) for early and 17.9% (95% CI 14.0% to 22.7%) for delayed stroke, compared with 2.4% (95% CI 1.9% to 3.1%) for patients without stroke (P<0.001 for early versus delayed, and for perioperative stroke, early stroke, and delayed stroke versus no stroke). At a mean follow‐up of 8.25 years, the incident rate of late mortality was 11.7% (95% CI 7.5% to 18.3%) for early and 9.4% (95% CI 5.9% to 14.9%) for delayed stroke, compared with 3.4% (95% CI 2.4% to 4.8%) in patients with no stroke. Meta‐regression demonstrated that off‐pump was inversely associated with early stroke (β=−0.009, P=0.01), whereas previous stroke (β=0.02, P<0.001) was associated with delayed stroke.

Conclusions

Early and delayed stroke after cardiac surgery have different risk factors and impacts on operative mortality as well as on long‐term survival.

Portable head computed tomography in the diagnosis of cerebral fat embolism secondary to cardiac surgery

BACKGROUND AND PURPOSE

Cerebral fat embolism (CFE) has been diagnosed previously by both brain magnetic resonance imaging (MRI) and dedicated head computed tomography (HCT) studies. The most commonly reported feature on CT is the presence of the "hypodense artery sign," although the number of reported cases has been minimal to date.

METHODS

Report of a single case involving a 88-year-old patient who underwent cardiac surgery. Postoperatively, the patient developed right hemiparesis. Contraindications existed for performing brain MRI and dedicated head CT. Portable head CT (pHCT) was obtained. Hounsfield unit measurement was used.

RESULTS

A hypodense artery sign was visualized, and Hounsfield unit measurement indicated fat density. Diagnosis was determined to be CFE.

CONCLUSION

This case report emphasizes that pHCT quality may be sufficient to diagnose CFE and offers a viable alternative when MRI or HCT is contraindicated.

Stroke after cardiac surgery--hemispheric distribution and survival

OBJECTIVES

Stroke following cardiac surgery may occur either in association with surgery (early) or occur postoperatively (delayed). The hemispheric distribution of lesions may provide information about embolic routes, which was analyzed here.

DESIGN

In 10,809 patients undergoing cardiac surgery, early (n = 223) and delayed stroke (n = 116) were explored. Symptoms and computed tomography findings were evaluated to categorize hemispheric distributions. This was compared with pre- and intra-operative characteristics and survival, using logistic regression and Kaplan-Meier statistics.

RESULTS

Early stroke had preponderance for the right rather than the left hemisphere (P = 0.009), whereas delayed stroke had a uniform distribution. Several intraoperative variables predicted the development of bilateral stroke compared with its unilateral counterpart. At multivariable analysis, the use of tranexamic acid was associated with bilateral stroke (P = 0.017), but was also associated with right rather than left-hemispheric stroke (P = 0.001). Bilateral lesions dramatically impaired survival versus those with unilateral lesions (P < 0.001). There was no survival difference between left and right-hemispheric stroke.

CONCLUSIONS

When stroke, after cardiac surgery, is subdivided into early and delayed forms, it becomes evident that early, but not delayed stroke, demonstrates a hemispheric side difference. The preponderance for right-hemispheric lesions may indicate embolic mechanisms routed via the brachiocephalic trunk.

Asymmetric pattern of cerebrovascular lesions in patients after left ventricular assist device implantation

BACKGROUND AND PURPOSE

Stroke is a major adverse event after left ventricular assist device (LVAD) surgery. The purpose of this study was to describe differences in hemispheric distribution of stroke in LVAD patients.

METHODS

We reviewed 317 consecutive patients who underwent LVAD surgery between November 2000 and July 2011. Stroke during LVAD support was analyzed.

RESULTS

In total, 46 strokes occurred at 76.0±96.8 days postoperatively. Among the 46 strokes, 27 events (58.7%) occurred in right hemisphere, 13 events (28.2%) in the left hemisphere, 3 events (8.7%) occurred bilaterally, and 2 events (4.3%) were vertebrobasilar lesions. The right hemispheric stroke was significantly more common in patients with postoperative infection compared with left hemispheric events.

CONCLUSIONS

Stroke after LVAD implantation has a right hemispheric predominance. This finding suggests LVAD-related thrombus in the setting of infection and/or the anatomic configuration of LVAD outflow cannula-ascending aorta anastomosis to be highly associated with stroke after LVAD surgery.

Early and delayed stroke after coronary surgery - an analysis of risk factors and the impact on short- and long-term survival

OBJECTIVE

Stroke is a serious complication to cardiac surgery, and is generally considered as a uniform disease regardless of its temporal relationship to surgery. Our hypothesis suggests that stroke, in association with surgery, reflects other characteristics than stroke occurring with a free interval. This issue was here explored for risk factors and survival effects.

METHODS

Data were collected from 7839 procedures of isolated coronary artery bypass grafting (CABG), 297 off-pump CABG, and 986 combined CABG and valve procedures. Records of patients with any signs of neurological complications were reviewed to extract 149 subjects with stroke at extubation (early, 1.6%) versus 99 patients having a free interval (delayed, 1.1%). Survival data were complete, with a median follow-up time of 9.3 years (maximum 16.3 years). Independent risk factors were analyzed by logistic regression and survival by Cox regression.

RESULTS

Risk factors for early stroke were advanced age, high preoperative creatinine level, extent of aortic atherosclerosis, and long cardiopulmonary bypass time (all P<0.001). Factors associated with delayed stroke were female gender (P<0.001), unstable angina (P=0.003), previous cerebrovascular disease (P=0.009), inotropic support requirement (P<0.001), and postoperative atrial fibrillation (P<0.001). Stroke explained mortality not only in the early postoperative period (P<0.001), but also at long-term follow-up (P<0.001). Early and delayed stroke were associated with mortality hazard ratios (HRs) of 1.44 and 1.85 (P=0.008, P<0.001), respectively. However, for patients surviving their first postoperative year, early stroke did not influence long-term mortality (HR 1.07, P=0.695). This was in contrast to delayed stroke (HR 1.71, P=0.001).

CONCLUSIONS

Early and delayed stroke differed in their related risk factors. The influence of stroke on short-term mortality was obvious and devastating. Mortality in association with early stroke mainly presented itself in the acute period, whereas for delayed stroke survival continued to be impaired also in the long-term perspective. Our report emphasizes that early and delayed stroke should be considered as two separate entities.

Ischemic stroke of the cortical "hand knob" area: stroke mechanisms and prognosis

Cortical ischemic stroke affecting the precentral "hand knob" area is a rare but well known stroke entity. To date, little is known about the underlying stroke mechanisms and the prognosis. Twenty-nine patients admitted to our service between 2003 and 2007 were included in the study on the basis of an acute ischemic infarct of the cortical "hand knob" area confirmed by diffusion-weighted magnetic resonance imaging with contralateral hand paresis. For all patients clinical, epidemiological as well as imaging data at the time point of admission were analysed retrospectively and follow-up data on all patients was obtained. The majority (n = 21/72%) had an isolated infarct of the cortical "hand knob" area. In 23 (79%) patients it was a first ever stroke. Ten patients (34%) had ipsilateral extracranial stenosis of the internal carotid artery (ICA), whereas potential cardiac embolic sources were less frequent (n = 4/14%). No patient exhibited ipsilateral MCA stenosis. All but two patients (93%) had marked atherosclerotic alterations of the ICA. Hypertension was the most prevalent vascular risk factor (n = 23/79%). At follow-up (mean 25.0 months, range 0.4-47.4 months) no patient had died and only one (3%) experienced a recurrent stroke. The majority of patients (79%) reported improvement of hand paresis, 17 (59%) were asymptomatic (modified Rankin score = 0). Only one patient was significantly disabled due to a recurrent stroke. In conclusion, ischemic infarcts affecting the cortical "hand knob" area are frequently associated with atherosclerotic changes of the carotid artery, suggesting an arterio-arterial thrombembolic stroke mechanism. It mostly reflects first ever ischemic stroke, and follow-up data suggest a rather benign course.

Incidence, topography, predictors and long-term survival after stroke in patients undergoing coronary artery bypass grafting

BACKGROUND

Previous studies on stroke after coronary artery bypass grafting (CABG) provide limited data about the timing (early vs delayed) of this event and findings of brain imaging analysis. This information is of significant importance because it provides insight into the etiology of stroke, potentially allowing the development of preventive measures. This study analyzed the incidence and timing of stroke, the topography and mechanisms of cerebral lesions, independent predictors, and late outcome after the occurrence of this complication in patients undergoing CABG.

METHODS

We retrospectively analyzed prospectively collected data from 2985 patients (2064 men [67%]), with a mean age of 66 +/- 11 years, who underwent CABG between January 1998 and December 2006. Stroke was defined as any new permanent focal neurologic deficit (early stroke, < or = 24 hours; delayed, > 24 hours postoperatively).

RESULTS

The incidence of stroke was 1.6% (n = 48) and similar between conventional CABG (1.6%) and off-pump CABG (1.4%). Early stroke occurred in 25 patients (52%). Brain imaging was obtained in 44 patients (92%): 44 had computed tomography, 3 had magnetic resonance imaging. Results were positive in 33 of 44 patients (75%), showing large embolic stroke in 25 (76%), watershed in 5 (15%), and mixed pattern in 3 (9%). Chronic ischemic changes were found in 17 patients. Multivariate analysis revealed extensive aortic calcification (odds ratio [OR], 4.2), previous stroke (OR, 2.2), female sex (OR, 1.9), and congestive heart failure (OR, 2.6) as predictors of stroke. The hospital mortality rate after stroke was 16.7% (n = 8) compared with 1.5% (n = 44) in those without (p < 0.001). The mortality rate was higher in early stroke at 24% (6 of 25) compared with 9% (2 of 23) in late stroke. Survival of stroke patients was 87% at 1 year and 62% at 5 years and was significantly reduced compared with 96% and 85%, respectively, in patients without stroke (p<0.001).

CONCLUSIONS

Most strokes after CABG occurred early after surgery. This complication is associated with an increased hospital mortality and morbidity and reduced long-term survival. The infarction type had no impact on early and late outcome. Preoperative computed tomography scan seems warranted in patients at risk and without any previous history of stroke.

Using an automated emboli detection device in a porcine cardiopulmonary bypass (CPB) model: feasibility and considerations

The significant risk of cerebral embolism during cardiopulmonary bypass (CPB) makes monitoring of embolic events advisable already when developing new operation and coagulation management strategies for example in CPB animal models. The present study therefore evaluated in a porcine CPB model the feasibility of bilateral epicarotid Doppler signal recording and the quality of manual or automatic emboli detection. A total of 42 recordings (e.g. right carotid artery (n = 20), left carotid artery (n = 22)) were evaluated. The frequency of emboli counts was comparable for both carotid arteries. Automatic emboli detection, however, found significantly more embolic events per pig than did post-hoc manual off-line analysis of the recordings (172 +/- 217 vs. 13 +/-10). None of the brains, however, showed any emboli or infarction area either in cross-examination or in histological evaluation. In conclusion, the present study showed the feasibility of using an epicarotid Doppler device for bilateral emboli detection in a porcine CPB model. Automatic on-line emboli detection, however, reported more embolic events than did post hoc, off-line manual analysis. Possible reasons for this discrepancy are discussed.

Value of cerebral perfusion computed tomography in the management of intensive care unit patients with suspected ischaemic cerebral pathology after cardiac surgery

OBJECTIVE

Adverse neurologic outcomes, like stroke, in intensive care unit (ICU) patients after cardiac surgery can have devastating consequences, among them increased mortality risk and, among survivors, loss of independence and a diminished quality of life. Non-contrast computed tomography (CT) remains a widely utilised modality for assessing stroke; however, it has a low sensitivity in the acute phase. Perfusion CT (PCT) has the potential of imaging stroke in its hyperacute phase. We evaluated the feasibility and results of the method among patients from the ICU.

METHODS

The NCCT and PCT images of 33 retrospectively identified patients were included in this study. The diagnostic contribution of the PCT to patient management was classified according to one of three categories: (A) those that changed the preliminary (NCCT) diagnosis; (B) those that revealed additional pathology and/or specified more exactly findings that have been detected by NCCT or clinically suspected; and (C) confirmed the preliminary diagnosis. Neurologic outcome variables were also documented and associated with PCT lesions.

RESULTS

Fifteen patients after coronary artery bypass graft (CABG) operation, 14 patients after CABG and valve surgery, and 4 patients after an aortic dissection (Type A) surgery underwent a NCCT with PCT 2.4+/-1.3 days after the operation. Twenty patients had bilateral internal carotid artery (ICA) stenosis (>50%), 11 patients had unilateral ICA stenosis (>75%), and 2 patients had no ICA stenosis. In nine patients (27.2%) the PCT changed the initial diagnosis of the NCCT and revealed ischaemic pathology. In 24 patients (72.7%), the performed PCT revealed additional pathology and/or more completely characterised findings that have been detected by the initial NCCT. In nine patients, PCT confirmed only the initial diagnosis. Patients with normal PCT findings had a favourable outcome; patients with large lesions in PCT in one or more vascular territories had an unfavourable outcome; seven patients with lesions in basal ganglia and/or semioval centre had a favourable outcome.

CONCLUSIONS

PCT shows a greater sensitivity in detecting and mapping acute ischaemic stroke in ICU patients (after cardiac surgery) in whom conventional imaging findings are not in line with the severity of the clinical condition.

Intraluminal aortic manipulation by means of intra-aortic filter, cannulation, and external clamp maneuvers evaluated versus dislodged embolic material

OBJECTIVES

Aortic atherosclerosis is an important risk factor for cerebrovascular accidents in cardiac surgery. An intra-aortic filter might reduce this risk. We aimed to analyze the risks for emboli associated with intraluminal aortic manipulation and intra-aortic filter handling in relation to cannulation and external clamp maneuvers.

METHODS

A model was designed with a cadaver aorta and retrograde perfusion (n = 16). A crossclamp was positioned on the ascending aorta and repeatedly opened under pressure to collect aliquots with dislodged particles. Cannulation was performed after 10 clamp maneuvers, followed by positioning and removing the intra-aortic filter, with each step followed by a washout sequence to collect perfusate. The removed filter was also analyzed. Evaluation was by means of digital image analysis, with differentiation of particles into different spectra.

RESULTS

Intra-aortic filter manipulation produced a significant washout of embolic particles; in particular, this was seen for the macroscopic cellular spectrum (P = .006 and P = .002 for filter insertion and removal, respectively). Particles were also found to be collected by the filter (P = .004). In addition, cannulation and aortic crossclamp manipulation generated a notable number of particles (P = .001 and P = .013, respectively).

CONCLUSIONS

The intra-aortic filter collects material during aortic manipulation. However, intraluminal aortic manipulation from filter handling can also dislodge particles, possibly related to shedding of intimal debris. This is in addition to substantial amounts of particles that are generated by aortic cannulation and aortic crossclamping.