Left hemispheric strokes in coronary surgery: implications for end-hole aortic cannulas

Risk Factors for Ischemic Stroke After Revascularization Surgery in Patients with Moyamoya Disease: An Age-Stratified Comparative Meta-Analysis

BACKGROUND

Patients who undergo revascularization surgery for moyamoya disease may develop postoperative ischemic stroke (pIS). Several studies have sought to identify risk factors; however, the findings remain highly inconsistent.

METHODS

PubMed, Scopus, and Web of Science were used to extract references. The first phase of screening required the studies to be in English, involve patients surgically treated for moyamoya disease, and report pIS. The second phase required the studies to provide ≥10 patients and include a control group.

RESULTS

All 22 studies were rated as high quality. Univariate analysis identified pediatrics <3 years of age as a risk factor for pIS (odds ratio [OR], 7.60; P < 0.0001). Among adult patients only, diabetes (OR, 2.10; P = 0.005), a Suzuki grade greater than 3 (OR, 1.74; P = 0.005), mean intraoperative systolic blood pressure (OR, 1.04; P < 0.0001), mean intraoperative diastolic blood pressure (OR, 1.04; P = 0.002), and revascularization in the left hemisphere (OR, 2.09; P = 0.001) were risk factors. Among both age groups, preoperative ischemic stroke (OR, 2.59; P < 0.00001) was a risk factor for pIS. Additionally, perioperative antiplatelet drug administration was a protective factor for specifically acute postoperative white thrombus among adult patients (OR, 0.35; P = 0.002).

CONCLUSIONS

In addition to the methods discussed that can mitigate the risk of pIS, the risk factors identified in our analysis may be of great value among surgeons for identifying high-risk patients in order to apply prophylactic measures, as well as scheduling longer and more frequent follow-up visits.

Flow analysis during mock circulation in normal and aortic arch aneurysm models through an aortic cannula toward the aortic arch and root

The aim of this study was to elucidate flow patterns of two different types of aortic cannulas inserted from the ascending aorta toward the aortic arch and root by mock circulation in a normal aortic arch and an aortic arch aneurysm model. Extracorporeal circulation was established using a centrifugal pump, a transparent glass normal aortic arch model, and an aortic arch aneurysm model for measurement by particle image velocimetry. The Stealthflow and Dispersion cannulas were used to elucidate the characteristics of the flow pattern and velocity under the condition of the cannula tip toward the aortic arch and aortic root. In the normal aortic arch model, high-velocity exit flow ranging from 0.7 to 0.8 m/s was detected in the proximal aortic arch by directing the cannula tip toward the aortic arch, whereas flow velocity in the aortic arch was < 0.2 m/s by directing the cannula tip toward the aortic root. In the aortic arch aneurysm model, high-velocity exit flow ranging from 0.5 to 0.8 m/s was detected in the aortic arch by directing the cannula tip toward the aortic arch, whereas flow velocity in the aortic arch was decreased to less than 0.2 m/s by directing the cannula tip toward the aortic root. Directing the aortic cannula tip toward the aortic root allowed the high-velocity exit flow to attenuate in velocity, so that flow velocity in the aortic arch was sufficiently reduced by reversed flow and vortex formation in both the normal and aortic arch aneurysm models.

The evolving role of the modern perfusionist: insights from transesophageal echocardiography

Transesophageal echocardiography is a relatively non-invasive, mobile, safe imaging technique that is ideal for providing real-time information on cardiac anatomy and function during heart surgery. The technology has evolved from two-dimensional to real-time three-dimensional imaging during cardiac procedures, which has significantly benefited preoperative planning, intraoperative guidance, evaluation, and postoperative follow-up. Transesophageal echocardiography may serve the clinical perfusionist by providing imaging guidance for identifying potential problems before cardiopulmonary bypass, guiding the proper placement of cannulas, monitoring cardiac performance on cardiopulmonary bypass, and providing useful feedback during weaning from cardiopulmonary bypass. Although the perfusionist should be able to understand all echocardiographic images and measurements in depth, perfusion-related echocardiographic information can or should be used to optimize the clinical practice of the modern perfusionist. Vice versa, whenever the perfusionist suspects a problem, the surgical team including the sonographer should verify this "clinical treat" by echocardiography whenever possible.

Clinical evaluation of a new dispersive aortic cannula

INTRODUCTION

Cerebral injury is a serious complication in open-heart surgery. Once it occurs, it causes significant disability and death. We developed a novel dispersive aortic cannula named the Stealth Flow cannula and used it as a standard aortic cannula in cardiopulmonary bypass. The aim of this study was to evaluate the efficiency of this aortic cannula.

METHODS

A total of 182 consecutive patients undergoing cardiac surgery using cardiopulmonary bypass were studied. The patients were divided into two groups: the Soft-Flow cannula group (n = 89) and the Stealth Flow cannula group (n = 93). Patients with a shaggy aortic arch were excluded from this study because the cannulae were inserted at the ascending aorta with a cannula tip directed toward the aortic root in these cases. Patients with multiple arterial perfusion sites were also excluded. Complications including early mortality, perioperative stroke, and intraoperative aortic injury were compared between the two groups.

RESULTS

Age, operative procedure, cardiopulmonary bypass time, and the Japan SCORE were not significantly different between the groups. In comparisons between the Stealth Flow and Soft-Flow groups, the incidences of early mortality, perioperative stroke, intraoperative aortic dissection, and all complications were 1.08% versus 1.12% (p = 0.98), 1.1% versus 2.2% (p = 0.53), 0% versus 1.1% (p = 0.33), and 1.1% versus 3.4% (p = 0.29), respectively. The incidence of major cardiovascular events, including early death, perioperative stroke, and aortic dissection, was not different.

CONCLUSIONS

The Stealth Flow cannula, which was designed based on our previous experimental study, contributed to reducing cerebral and aortic events as much as the Soft-Flow cannula in the present clinical study.

Numerical Investigation of Blood Flow Characteristics through Cannulated Aorta

Cannulation of the aorta is done in order to provide oxygenation and circulatory function through the use of the heart lung machine during cardio-pulmonary bypass (CPB). The nature of the blood flow through the aorta and its ramifications during CPB is mostly linear as compared to the physiological flow, which is pulsatile in nature. This leads to the development of multiple morbidities caused by the development of emboli and atheromas. Perioperative postoperative care is necessitated by these conditions. As such the understanding of the blood flow characteristics is necessitated in order to effectively prevent the formation of emboli and to prevent the "Sandblasting" effect. The authors in this work seek to investigate the nature of blood flow through the aorta under such circumstances. The results obtained show the nature of blood flow in the cannulated aorta as well as the optimum angle of placement of the cannula with respect to the aortic wall.

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.

Improved hydrodynamics of a new aortic cannula with a novel tip design

Background: Reduction of atheroembolic complications during cardiopulmonary bypass remains a major challenge in cardiac surgery. New cannula tip designs may help to attenuate this problem by improved hydrodynamics.

Methods: Pressure gradients and back pressures of a new aortic cannula tip design were measured and compared with the Medos X-Flow, Sarns Soft-Flow and Argyle THI cannulae at various flow rates in a mock circulation followed by flow visualization.

Results: Pressure gradients were the lowest for the new cannula. Back pressures of the new cannula were up to 84% lower than for the Argyle cannula. The back pressure profile and flow visualization of the new cannula showed broad centric flow dispersion with a transcannula increase of flow area from 38 mm2 to 139 mm2.

Conclusions: The new design of an aortic cannula tip provides improved hydrodynamics, with low pressure gradients, low back pressures and a uniform central dispersion of flow, reducing the sandblasting effect.

Hydrodynamic evaluation of aortic cardiopulmonary bypass cannulae using particle image velocimetry

The high velocity jet from aortic arterial cannulae used during cardiopulmonary bypass potentially causes a "sandblasting" injury to the aorta, increasing the possibility of embolisation of atheromatous plaque. We investigated a range of commonly available dispersion and non-dispersion cannulae, using particle image velocimetry. The maximum velocity of the exit jet was assessed 20 and 40 mm from the cannula tip at flow rates of 3 and 5 L/min. The dispersion cannulae had lower maximum velocities compared to the non-dispersion cannulae. Dispersion cannulae had fan-shaped exit profiles and maximum velocities ranged from 0.63 to 1.52 m/s when measured at 20 mm and 5 L/min. Non-dispersion cannulae had maximum velocities ranging from 1.52 to 3.06 m/s at 20 mm and 5 L/min, with corresponding narrow velocity profiles. This study highlights the importance of understanding the hydrodynamic performance of these cannulae as it may help in selecting the most appropriate cannula to minimize the risk of thromboembolic events or aortic injury.

Cognitive dysfunction after on-pump operations: neuropsychological characteristics and optimal core battery of tests

Postoperative cognitive dysfunction (POCD) is a mild form of perioperative ischemic brain injury, which emerges as memory decline, decreased attention, and decreased concentration during several months, or even years, after surgery. Here we present results of our three neuropsychological studies, which overall included 145 patients after on-pump operations. We found that the auditory memory span test (digit span) was more effective as a tool for registration of POCD, in comparison with the word-list learning and story-learning tests. Nonverbal memory or visuoconstruction tests were sensitive to POCD in patients after intraoperative opening of cardiac chambers with increased cerebral air embolism. Psychomotor speed tests (digit symbol, or TMT A) registered POCD, which was characteristic for elderly atherosclerotic patients. Finally, we observed that there were significant effects of the order of position of a test on the performance on this test. For example, the postoperative performance on the core tests (digit span and digit symbol) showed minimal impairment when either of these tests was administered at the beginning of testing. Overall, our data shows that the selection of tests, and the order of which these tests are administered, may considerably influence the results of studies of POCD.

Investigation of risks for cerebral embolism associated with the hemodynamics of cardiopulmonary bypass cannula: a numerical model

Cerebral emboli originating in the ascending aorta are a major cause of noncardiac complications following cardiac surgery. The hemodynamics of the aortic cannula has been proven to play a significant role in emboli generation and distribution. The aim of the current study was to perform a thorough numerical investigation in order to examine the effect of the design and orientation of the cannula used during cardiopulmonary bypass on the risk to develop cerebral embolism. Hemodynamic analyses compared numerical models of 27 cases consisting of six different cannula orientations, four aortic anatomies, and three cannula designs. The cannula designs included a straight-tip (ST) cannula, a moderately curved tip cannula (TIP1 ), and a sharp-angle curved cannula (TIP2 ). Outcome measures included hemodynamic parameters such as emanating jet velocity, jet velocity drop, maximal shear stress, aortic wall reaction, emboli pathlines and distribution between upper and lower vessels, and stagnation regions. Based on these parameters, the risks for hemolysis, atheroembolism, and cerebral embolism were evaluated and compared. On one hand, the jet emerging from the ST cannula generated large wall-shear stress at the aortic wall; this may have triggered the erosion and distribution of embolic atheromatous debris from the aortic arch. On the other hand, it diverted more emboli from the clamp region to the descending aorta and thus reduced the risk for cerebral embolism. The TIP1 cannula demonstrated less shear stress on the aortic wall and diverted more emboli from the clamp region toward the upper vessels. The TIP2 cannula exhibited a stronger emanating jet, higher shear stress inside the cannula, and highly disturbed flow, which was more stagnant near the clamp region. Current findings support the significant impact of the cannula design and orientation on emboli generation and distribution. Specifically, the straight tip cannula demonstrated a reduced risk of cerebral embolism, which may be pivotal in the clinical setting.

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.

Venous drainage--gravity or assisted?

Since the early start of cardiopulmonary bypass, vascular access has been recognized as a main variable for obtaining optimal blood flow during cardiopulmonary bypass. In particular, venous drainage can limit the maximum flow as the wide, low-resistance, collapsible veins are connected with smaller stiff cannulas and tubing. Due to the introduction of long venous cannulas for minimally invasive cardiac surgery and the desire to limit hemodilution during cardiopulmonary bypass, more and more centers have started using assisted venous drainage techniques. This article gives an overview of these techniques, with their respective advantages and disadvantages.

Case-matched comparison of early and long-term outcomes of everted cervical vein and saphenous vein carotid patch angioplasty

OBJECTIVES

To compare outcomes after carotid endarterectomy (CEA) with saphenous vein patch closure (SV), with cervical vein (external jugular and common facial) patch closure (CV).

DESIGN

A total of 322 cases of CEA was achieved consecutively by using venous patch angioplasty. Propensity scores were calculated followed by a one-to-one basis case-matching.

MATERIALS

This resulted into 90 SV and 90 CV matched cases.

METHODS

The primary endpoint was the incidence of ipsilateral stroke and transient ischaemic attack at any time during follow-up.

RESULTS

Ten-year freedom from stroke was 94.1% ± 3.5% for the SV group and 90.5% ± 4.2% for the CV group (log rank P = 0.230). Ten-year freedom from ipsilateral neurological events (stroke and transient ischaemic attack) was 93.5% ± 3.3% for SV group and 92.4% ± 3.0% for the CV group (log rank P = 0.403). Ten-year freedom from ≥75% stenosis/occlusion was 93.1 ± 4.8% for the SV group and 89.9 ± 6.0% for the CV group (log rank P = 0.481).

CONCLUSIONS

CV is a good alternative to SV patching, particularly when the SV needs to be preserved for further use or is unsuitable.

Electroencephalography as a tool for assessment of brain ischemic alterations after open heart operations

Cardiac surgery is commonly associated with brain ischemia. Few studies addressed brain electric activity changes after on-pump operations. Eyes closed EEG was performed in 22 patients (mean age: 45.2 ± 11.2) before and two weeks after valve replacement. Spouses of patients were invited to participate as controls. Generalized increase of beta power most prominent in beta-1 band was an unambiguous pathological sign of postoperative cortex dysfunction, probably, manifesting due to gamma-activity slowing (“beta buzz” symptom). Generalized postoperative increase of delta-1 mean frequency along with increase of slow-wave activity in right posterior region may be hypothesized to be a consequence of intraoperative ischemia as well. At the same time, significant changes of alpha activity were observed in both patient and control groups, and, therefore, may be considered as physiological. Unexpectedly, controls showed prominent increase of electric activity in left temporal region whereas patients were deficient in left hemisphere activity in comparison with controls at postoperative followup. Further research is needed in order to determine the true neurological meaning of the EEG findings after on-pump operations.

Numerical simulation of hemodynamics in the ascending aorta induced by different aortic cannulas

There is still a lack of quantitative information concerning optimal blood flow in the aorta and in the carotid arteries during extracorporeal circulation (ECC). Problems are not only based on the location of the aortic cannula, they are furthermore associated with the cannula design itself and the effects on blood cells and aortic wall shear stresses. We simulated a two-phase fluid flow induced by different cannulas in the ascending aorta during ECC. Three commercially available cannulas were examined according to their influence on red blood cells (RBC). Additionally, mass flow in the carotid vessels and wall shear stresses acting on the aortic wall were evaluated. A constant volume flow of blood (3.4 L/min) was applied. Numerical results demonstrate a strong relation between the mass flow rate in the carotid vessels and the geometry of the aortic outflow cannula. RBC distributions both in the aorta and the carotid vessels changed depending on cannula geometry. Maximum blood velocities, shear stresses on the aortic wall, and the fluid mechanical load acting on RBCs varied depending on each cannula design. This numerical approach demonstrates the significant influence of the cannula design on the distribution of RBCs in the carotid vessels during ECC.

Hemodynamics of an end-to-side anastomotic graft for a pulsatile pediatric ventricular assist device

Numerical simulations are performed to investigate the flow within the end-to-side proximal anastomosis of a pulsatile pediatric ventricular assist device (PVAD) to an aorta. The anastomotic model is constructed from a patient-specific pediatric aorta. The three great vessels originating from the aortic arch--brachiocephalic (innominate), left common carotid, and left subclavian arteries--are included. An implicit large eddy simulation method based on a finite volume approach is used to study the resulting turbulent flow. A resistance boundary condition is applied at each branch outlet to study flow splitting. The PVAD anastomosis is found to alter the aortic flow dramatically. More flow is diverted into the great vessels with the PVAD support. Turbulence is found in the jet impingement area at peak systole for 100% bypass, and a maximum principal normal Reynolds stress of 7081 dyn/cm(2) is estimated based on ten flow cycles. This may be high enough to cause hemolysis and platelet activation. Regions prone to intimal hyperplasia are identified by combining the time-averaged wall shear stress and oscillatory shear index. These regions are found to vary, depending on the percentage of the flow bypass.

Hydrodynamics of aortic cannulae during extracorporeal circulation in a mock aortic arch aneurysm model

This study was designed to analyze flow pattern, velocity, and strain on the aortic wall of a glass aortic arch aneurysm model during the extracorporeal circulation, and to elucidate the characteristics of flow pattern in three different aortic cannulae. Different patterns of large vortices and helical flow were made by each cannula. With the curved end-hole cannula, the high velocity flow (approximately 0.6-0.8 m/s) was blowing to the aneurismal wall without attenuating the strain rate tensor (approximately 0.2-0.25/s). With the dispersion cannula and the Soft-Flow cannula, cannular jet was attenuated in the ascending aorta creating a large vortex at a velocity less than 0.5 m/s, and the strain rate tensor on the aneurismal wall was small (less than 0.15/s). In conclusion, end-hole cannula should not be used in the operation of aortic arch aneurysm. Dispersion-type aortic cannulae were less invasive on the aortic arch aneurismal wall, but particular attention to alternative cannulation sites should be paid in cases with severe atherosclerosis on the ascending aortic wall.

Numerical Study of Blood Flow at the End-to-Side Anastomosis of a Left Ventricular Assist Device for Adult Patients

We use an implicit large eddy simulation (ILES) method based on a finite volume approach to capture the turbulence in the anastomoses of a left ventricular assist device (LVAD) to the aorta. The order-of-accuracy of the numerical schemes is computed using a two-dimensional decaying Taylor–Green vortex. The ILES method is carefully validated by comparing to documented results for a fully developed turbulent channel flow at Reτ=395. Two different anastomotic flows (proximal and distal) are simulated for 50% and 100% LVAD supports and the results are compared with a healthy aortic flow. All the analyses are based on a planar aortic model under steady inflow conditions for simplification. Our results reveal that the outflow cannulae induce high exit jet flows in the aorta, resulting in turbulent flow. The distal configuration causes more turbulence in the aorta than the proximal configuration. The turbulence, however, may not cause any hemolysis due to low Reynolds stresses and relatively large Kolmogorov length scales compared with red blood cells. The LVAD support causes an acute increase in flow splitting in the major branch vessels for both anastomotic configurations, although its long-term effect on the flow splitting remains unknown. A large increase in wall shear stress is found near the cannulation sites during the LVAD support. This work builds a foundation for more physiologically realistic simulations under pulsatile flow conditions.

High Incidence of Infarction in the Left Cerebral Hemisphere Among Young Adults

We hypothesized that left cerebral hemisphere infarction is more frequent than right hemisphere infarction among young adults. Furthermore, we aimed to evaluate possible causes for this asymmetry. Cases were found by computer search from hospital registries at each of the 5 acute-care hospitals in a well-defined population in Hordaland County, western Norway. Important parameters used in the analysis were derived from the patient records. A total of 98 patients had left hemisphere infarctions, and 70 patients had right hemisphere infarctions (P = .037). This difference was due mostly to the higher incidence of infarction in the left middle cerebral artery (MCA) territory compared with the right MCA territory among the male subjects (P = .016). Lacunar infarction was equally distributed, whereas nonlacunar infarction was more frequent in the left MCA territory among the men (P = .016). A high frequency of left MCA infarctions may be associated with more frequent atherosclerosis in the left carotid artery, lateralization of cortical functions, or both in young adults.

Asymmetric Cerebral Embolic Load and Postoperative Cognitive Dysfunction in Cardiac Surgery

BACKGROUND

The aim of the study was to determine the effects of asymmetric cerebral embolic load on cognitive functions.

METHODS

Thirty-six open heart surgery (OH) and 26 coronary artery bypass grafting (CABG) patients were evaluated by neuropsychological and transcranial Doppler tests.

RESULTS

OH was associated with a significantly larger microembolic load in comparison to CABG. In OH patients, the microembolic load at the left middle cerebral artery correlated with a verbal memory decline, whereas the microembolic load at the right middle cerebral artery correlated with a nonverbal memory deficit. CABG patients also showed a postoperative verbal memory decline which correlated with cardiopulmonary bypass length but not with microembolic load.

CONCLUSION

Massive microembolic load during OH induces specific cognitive impairment in accordance to the brain region to which they are delivered. In atherosclerotic patients, the left temporal region is especially prone to perioperative ischemia.

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

There is a link between aortic manipulation, particle embolization, and cerebrovascular accidents (CVA) in cardiac surgery. The present aim was to study hemispheric side differences of CVA. Cardiac-surgery patients with CVA and with computer tomography (CT) performed (n = 77) were analyzed within a total group of 2641 consecutive cases. CT data were reviewed for hemispheric and vascular distribution, and compared with CVA-symptom data of immediate and delayed type. Of the included patients, 66% had positive CT. In the group of 'cardiac-type' operations (e.g., routine clamping and cannulation) and having immediate CVA, right-hemispheric lesions were more frequent than of the contra-lateral side (p = 0.005). Patients with aortic dissections had strong dominance of bilateral findings, which was different from the unilateral pattern of 'cardiac-type' operations (p = 0.001). The middle-cerebral artery territory dominated, and when involved showed a significant (p = 0.022) right-sided distribution. Both CT and clinical symptoms confirmed that CVA after cardiac surgery has a right-hemispheric predominance. These observations may imply that aortic manipulation directs embolic material towards the brachiocephalic trunk.

Neural correlates of cognitive dysfunction after cardiac surgery

Patients who underwent cardiac surgery and their relatives often complain on postoperative memory impairment. Most prospective neuropsychological studies also found postoperative cognitive decline early after surgery. Nevertheless, recently several reports questioned the existence of long-term brain alterations in these patient cohorts. The present review was aimed to clear up the true cardiac surgery effects on brain and cognitive functions. The reviewed data evidence that cardiac surgery interventions induce persistent localized brain ischemic lesions along with rapidly reversing global brain swelling and decreased metabolism. A range of studies showed that left temporal region was especially prone to perioperative ischemic injury, and these findings might explain persistent verbal short-term memory decline in a considerable proportion of cardiac surgery patient cohorts. Speed/time of cognitive performance is commonly decreased early after on-pump surgery either. Nevertheless, no association between psychomotor speed slowing and intraoperative embolic load was found. The rapid recovery of the latter cognitive domain might be better explained by surgery related acute global brain metabolism changes rather than ischemic injury effects. Hence, analyses of performance on separate cognitive tests rather than summarized cognitive indexes are strongly recommended for future neuropsychological studies of cardiac surgery outcomes.

Side differences in cerebrovascular accidents after cardiac surgery: a statistical analysis of neurologic symptoms and possible implications for anatomic mechanisms of aortic particle embolization

BACKGROUND

Aortic manipulation and particle embolization have been identified to cause cerebrovascular accidents in cardiac surgery. Recent data suggest that left-hemispheric cerebrovascular accident (right-sided symptoms) is more common, and this has been interpreted as being caused by aortic cannula stream jets. Our aim was to evaluate symptoms of cerebrovascular accident and side differences from a retrospective statistical analysis.

METHODS

During a 2-year period, 2641 consecutive cardiac surgery cases were analyzed. Patients positive for cerebrovascular accident were extracted from a database designed to monitor clinical symptoms. A protocol was used to confirm symptom data with the correct diagnosis in patient records. Patients were subdivided into 3 groups: control, immediate cerebrovascular accident, and delayed cerebrovascular accident.

RESULTS

Among pooled patients, immediate and delayed cerebrovascular accidents were 3.0% and 0.9%, respectively. The expected predisposing factors behind immediate cerebrovascular accidents were significant, although the type of operation affected this search. Aortic quality was a strong predictor ( P < .001). The rate of delayed cerebrovascular accident was unaffected by surgery group. Left-sided symptoms of immediate cerebrovascular accident were approximately twice as frequent ( P = .016) as on the contralateral side. This phenomenon was observed for pooled patients and for isolated coronary bypass procedures (n = 1882; P = .025).

CONCLUSIONS

Immediate cerebrovascular accident and aortic calcifications are linked. The predominance of left-sided symptoms may suggest that aortic manipulation and anatomic mechanisms in the aortic arch are more likely to cause cerebrovascular accidents than effects from cannula stream jets.

Benefits of off-pump bypass on neurologic and clinical morbidity: a prospective randomized trial

BACKGROUND

Neurologic and clinical morbidity after coronary artery bypass grafting (CABG) can be significant. By avoiding cardiopulmonary bypass, off-pump CABG (OPCAB) may reduce morbidity.

METHODS

Sixty patients (30 CABG and 30 OPCAB) were prospectively randomized. Neurocognitive testing was performed before the operation and 2 weeks and 1 year after the operation. Neurologic testing to detect stroke and (99m)Tc-HMPAO whole-brain single photon emission computed tomography scanning to assess cerebral perfusion were performed before the operation and 3 days afterward. Bilateral middle cerebral artery transcranial Doppler scanning was performed intraoperatively to detect cerebral microemboli. All examiners were blinded to treatment group. Clinical morbidity and costs were compared.

RESULTS

Coronary artery bypass grafting was associated with more cerebral microemboli (575 +/- 278.5 CABG versus 16.0 +/- 19.5 OPCAB (median +/- semiinterquartile range) and significantly reduced cerebral perfusion after the operation to the bilateral occipital, cerebellar, precunei, thalami, and left temporal lobes (p < or = 0.01). Cerebral perfusion with OPCAB was unchanged. Compared with base line, OPCAB patients performed better on the Rey Auditory Verbal Learning Test (total and recognition scores) at both 2 weeks and at 1 year (p < or = 0.05), whereas CABG performance was statistically unchanged for all cognitive measures. Patients who underwent CABG had more chest tube drainage (1389 +/- 1256 mL CABG versus 789 +/- 586 mL OPCAB, p = 0.02) and required more blood (3.9 +/- 5.8 U CABG versus 1.2 +/- 2.2 U OPCAB, p = 0.02), fresh frozen plasma (3.0 +/- 6.0 U CABG versus 0.5 +/- 2.2 U OPCAB, p = 0.03), and hours of postoperative use of dopamine (16.3 +/- 21.2 hours CABG versus 7.3 +/- 9.7 hours OPCAB, p = 0.04). These differences culminated in higher costs for CABG ($23,053 +/- $5,320 CABG versus $17,780 +/- $4,390 OPCAB, p < 0.0001). One stroke occurred with CABG, compared with none with OPCAB (p = NS). One OPCAB patient died because of a pulmonary embolus (p = NS).

CONCLUSIONS

Compared with CABG, OPCAB may reduce neurologic and clinical morbidity as well as cost.

Echocardiographic comparison of the standard end-hole cannula, the soft-flow cannula, and the dispersion cannula during perfusion into the aortic arch

BACKGROUND

Dislodgement of aortic arch atheroma caused by a perfusion "jet" from the aortic cannula may be a major cause of atheroemboli during coronary artery surgery when using cardiopulmonary bypass (CPB). Two very different cannulas, the Soft-Flow aortic cannula and the Dispersion cannula, which have been designed to reduce exit velocity (cm/s) during perfusion, are compared with a standard steel tip cannula and to each other.

METHODS

To demonstrate any significant differences transesophageal echocardiography (TEE) was used to measure exit velocity of each cannula at a distance of 1, 2, and 3 cm from the tip and compare flow morphology within the aortic arch. Nine patients in whom the cannula tip could be identified and colored Doppler imaging could demonstrate representative morphology were randomly assigned into one of three groups of 3 patients each: group I, a standard steel-tip end-hole cannula (7.3 mm); group II, the Soft-Flow cannula (8.0 mm); and group III, the Dispersion cannula (8.0 mm).

RESULTS

The standard steel tip cannula demonstrated a long narrow perfusion jet. The Soft-Flow cannula morphology was made up of multiple smaller exiting jets. The Dispersion cannula demonstrated a broad wedge-shaped perfusion pattern. Perfusion hemodynamics (cardiopulmonary bypass hematocrit in d/L, cardiopulmonary bypass blood flow in L/m, mean arterial pressure during cardiopulmonary bypass mm Hg, and perfusion line pressure in mm Hg) were not significantly different between each group. The mean velocities between group I (318 +/- 63 cm/s at 1 cm, 296 +/- 60 cm/s at 2 cm, 271 +/- 85 cm/s at 3 cm) and group II (351 +/- 31 cm/s at 1 cm, 240 +/- 103 cm/s at 2 cm, 171 +/- 120 cm/s at 3 cm) were not statistically different. Group III (the Dispersion cannula) demonstrated significantly reduced velocities (174 +/- 22 cm/s at 1 cm, 138 +/- 23 cm/s at 2 cm, 90 +/- 36 cm/s at 3 cm) when compared with the other two groups (p < 0.05, analysis of variance).

CONCLUSIONS

The Dispersion cannula is significantly different with a lower perfusion velocity and the elimination of the exiting jet or jets. This cannula warrants further clinical study as it may reduce atheroemboli during cardiopulmonary bypass.

Is there any impact of the shape of aortic end-hole cannula on stroke occurrence? clinical evaluation of straight and bent-tip aortic cannulae

OBJECTIVE

To compare the impact of straight and bent-tip aortic cannulae on stroke occurrence, location, and severity.

METHODS

Prospective data were collected on 8,129 patients (coronary artery bypass grafting (CABG) and/or valvular surgery). 'Bent-tip' aortic cannulae were used in 15.6% of cases and 'straight' end-hole cannulae in 84.4% of cases.

RESULTS

There were a total of 137 strokes: right anterior 52, left anterior 39, bilateral 23, posterior 18, and location not established 5. With the use of bent-tip cannulae, the incidence of strokes was 0.9% versus 1.8% with straight cannulae (chi2, p = 0.026). Bilateral and posterior strokes occurred more often with the use of straight cannulae (chi2, p = 0.015). Straight cannulae also related to the severity of strokes (chi2, p = 0.003).

CONCLUSIONS

There is an influence of the type of cannula on the occurrence, location, and severity of strokes. Straight cannulae cause significantly more often and more severe bilateral and posterior strokes than bent-tip cannulae.

Hydrodynamics of the new Medos aortic cannula

BACKGROUND

Postoperative neurologic complications in cardiac surgery patients are considered to be associated with the design of an aortic cannula and its hydrodynamic profile. To gain knowledge about the hydrodynamics of a new cannula type, based on the integration of a helical stator in its tip, was the aim of the present study.

METHODS

Pressure gradients and back pressures of the new Medos aortic cannula were measured and compared with a commonly used single-stream cannula at varying flow rates in a mock circulation. Additionally, flow visualization was performed by ink injection.

RESULTS

Pressure gradients across the Medos cannula were 25.5-31.8% lower at all flow rates measured when compared to the reference cannula. Back pressures of the Medos cannula were 64.1-67.9% lower than reference back pressures.

CONCLUSIONS

The Medos cannula provides improved hydrodynamic characteristics, probably reducing the risk of atherosclerotic embolism and cerebral malperfusion by avoidance of high back pressures and sandblasting effect.

In vitro hydrodynamics of the Embol-X cannula

BACKGROUND

Prevention of intraoperative plaque dislodgement in patients with atherosclerotic ascending aorta by development of innovative aortic cannula designs gains growing interest in cardiac surgery. To increase knowledge about the hydrodynamics of the innovative Embol-X cannula, which includes an intra-aortic filter device targeting at atheromatous emboli capture, was the aim of the present study.

METHODS

Pressure gradients and back pressures of the Embol-X cannula were measured at varying flow rates in a mock circulation and compared with two commonly used single-stream cannulae.

RESULTS

At a flow rate of 5.5 l/min, pressure gradients across the Argyle and the RMI cannulae were 48% and 62% and back pressures 25% and 47% lower than the corresponding values across the Embol-X cannula.

CONCLUSIONS

The novel concept of integrating a filter device may provide clinical advantages concerning neurologic outcome. Further in vivo studies seem to be desirable to obtain more information concerning the clinical effects of the Embol-X cannula hydrodynamics.