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Stroke during cardiac surgery: risk factors, mechanisms and survival effects
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Stroke i samband med hjärtkirurgi : riskfaktorer, mekanismer och effekter på överlevnad (Swedish)
Abstract [en]

Introduction: Neurological complications and stroke in association with cardiac surgery is a serious problem. The stroke event can occur during surgery (early stroke) or in the postoperative period with a symptom free interval (delayed stroke). Particle embolization due to aortic manipulation during surgery has been suspected as a mechanism for early stroke. The present thesis address mechanisms and survival effects of stroke both clinically (I-III) and experimentally (IV-V).

Methods: Study I) Within a cohort of 2641 consecutive cases, a group of cardiac surgery patients with stroke and evaluated by computed tomography (CT) were studied (n=77). CT-findings were analyzed in relation to stroke symptoms. Study II) Data from 9122 patients undergoing coronary surgery were analyzed. 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%). Early and delayed stroke were evaluated separately. Independent risk factors for stroke were analyzed by logistic regression and survival by Cox regression (9.3 years median follow-up). Study III) Patients with early (n=223) and delayed stroke (n=116) were identified among 10809 patients undergoing cardiac and aortic surgery, both groups exposed to cardiopulmonary bypass. Stroke patients were subdivided by the hemispheric location of lesions. Subgroups were compared and their associated pre- and peroperative variables and survival were analyzed. Study IV) Aortic cross-clamp manipulation was studied in a human cadaveric perfusion model. The pressurized aorta was repeatedly cross-clamped and washout samples were collected before and after clamp maneuvers. Particles in the washout samples were evaluated by microscopy and by digital image analysis. Study V) Pig aortas were pressurized and cannulated. Washout samples were collected before and after cannulation (n = 40). Particles were deposited onto a 10-μm filter to be evaluated by microscopy and digital image analysis.

Results: Study I) In the group of patients exposed to routine cardiac surgery (i.e., clamping and cannulation) and with early stroke, right-hemispheric lesions were more frequent than of the contra-lateral side (P=0.005). Patients with aortic dissections had a strong dominance of bilateral findings, which was different from the unilateral pattern in the routine-surgery group (P<0.001). Study II) Early and delayed stroke did not share any risk factors. Both early and delayed stroke explained mortality in the early postoperative period (P<0.001, P<0.001 respectively) but also at long term follow-up (P=0.008, P<0.001 respectively). For patients surviving their first postoperative year, delayed but not early stroke influenced long-term mortality (P=0.001 and P=0.695, respectively). Study III) Stroke lesions in association to cardiac surgery were near exclusively ischemic. Early stroke had a preponderance for right-hemispheric lesions (P=0.009). In contrast, patients with early stroke that had undergone surgery of the aorta with circulatory arrest showed a pattern with more bilateral lesions compared to ‘cardiac-type’ operations (P<0.001). Patients with bilateral lesions had a dramatically impaired survival compared to those with unilateral lesions (P<0.001). Study IV) In the cadaveric perfusion model, cross-clamping produced a significant output of particles, which was seen for size intervals of 1 mm and smaller (P=0.002 to P=0.022). In all size intervals the particle output correlated with the degree of overall aortic calcification (P =0.002 to P=0.025). Study V) At cannulation of the pig aorta, more particles were noted after cannulation compared to before the maneuver (P<0.001). This increase included small (<0.1 mm, P<0.001) and intermediate-size particles (0.1-0.5 mm, P< 0.001). Particles above 0.5 mm were few and were not associated with cannulation.

Conclusions: The influence of stroke on mortality was devastating, for both early and delayed stroke. These two stroke groups had obvious differences in both their risk factors and their hemispheric distribution. It is here emphasized that early and delayed stroke should be considered as two separate entities with suggested mechanistic differences. Ischemic lesions accounted for near all stroke events seen in association to cardiac surgery. For early stroke, these were mostly located within the right hemisphere. Results from the experimental studies underscore microembolic risks associated with aortic manipulation.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2010. , 40 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1392
Keyword [en]
stroke; cardiac surgery; adult; risk factors; mortality; embolism; aortic cross-clamp; aortic cannulation
National Category
Surgery
Research subject
Thoracic and Cardivascular Suregery
Identifiers
URN: urn:nbn:se:umu:diva-38079ISBN: 978-91-7459-120-0 (print)OAI: oai:DiVA.org:umu-38079DiVA: diva2:372224
Public defence
2010-12-17, Sal B, Tandläkarhögskolan, 9 tr, Norrlands universitetssjukhus, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2010-12-03 Created: 2010-11-24 Last updated: 2010-12-03Bibliographically approved
List of papers
1. Cerebrovascular accidents after cardiac surgery: an analysis of CT scans in relation to clinical symptoms
Open this publication in new window or tab >>Cerebrovascular accidents after cardiac surgery: an analysis of CT scans in relation to clinical symptoms
2005 (English)In: Scandinavian Cardiovascular Journal, ISSN 1401-7431, E-ISSN 1651-2006, Vol. 39, no 5, 299-305 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
Aged, Cardiac Surgical Procedures/*adverse effects, Coronary Artery Bypass, Dominance; Cerebral, Female, Humans, Intracranial Embolism/etiology, Male, Middle Aged, Postoperative Complications/radiography, Risk Factors, Stroke/etiology/*radiography, Telencephalon/radiography, Tomography; X-Ray Computed
Identifiers
urn:nbn:se:umu:diva-6034 (URN)10.1080/14017430510035907 (DOI)16269400 (PubMedID)
Available from: 2007-12-05 Created: 2007-12-05 Last updated: 2017-12-14Bibliographically approved
2. Early and delayed stroke after coronary surgery: an analysis of risk factors and the impact on short and long-term survival
Open this publication in new window or tab >>Early and delayed stroke after coronary surgery: an analysis of risk factors and the impact on short and long-term survival
(English)Manuscript (preprint) (Other academic)
Keyword
Stroke, cardiac surgery, risk factors, survival
National Category
Surgery
Research subject
Thoracic and Cardivascular Suregery
Identifiers
urn:nbn:se:umu:diva-38065 (URN)
Available from: 2010-11-24 Created: 2010-11-24 Last updated: 2010-12-03Bibliographically approved
3. Hemispheric distribution of stroke after cardiac surgery: patient characteristics and survival impact
Open this publication in new window or tab >>Hemispheric distribution of stroke after cardiac surgery: patient characteristics and survival impact
(English)Manuscript (preprint) (Other academic)
Keyword
cardiac surgery, stroke, early, delayed, hemispheric, survival
National Category
Surgery
Research subject
Thoracic and Cardivascular Suregery
Identifiers
urn:nbn:se:umu:diva-38066 (URN)
Available from: 2010-11-24 Created: 2010-11-24 Last updated: 2010-12-03Bibliographically approved
4. Size distribution of embolic material produced at aortic cross-clamp manipulation
Open this publication in new window or tab >>Size distribution of embolic material produced at aortic cross-clamp manipulation
2010 (English)In: Scandinavian Cardiovascular Journal, ISSN 1401-7431, E-ISSN 1651-2006, Vol. 44, no 6, 367-372 p.Article in journal (Refereed) Published
Abstract [en]

Objectives: The association between aortic atherosclerosis and neurological damage during cardiac surgery is well recognized. The purpose was here to analyze the size distribution of particles produced at cross-clamp manipulation of the ascending aorta.

Design: A human cadaveric aortic perfusion model of retrograde design was applied (n 27). With this model, washout samples were collected from the pressurized ascending aorta during cross clamp manipulation. Before the experiment, the aorta was flushed to remove debris and with a baseline sample collected. The cross-clamp was opened to collect ten repeated aliquots with dislodged particles. Collected washout samples were evaluated by digital image analysis and microscopy.

Results: Cross-clamping produced a significant output of particles, which was seen for size intervals of 1 mm and smaller (p 0.002 to p 0.022). In all size intervals the particle output correlated with the degree of overall aortic calcification(p 0.002 to p 0.025). The model generated substantially more small-size particles than large debris (p 0.010).

Conclusions: Aortic clamping was here verified to dislodge aortic debris which correlated with the degree of observed calcification. Macroscopic particles were few. In contrast, cross-clamping produced substantial numbers of small-size particles. These findings emphasize microembolic risks associated with cross-clamping of atherosclerotic vessels.

Place, publisher, year, edition, pages
London, UK: Informa Plc., 2010
Keyword
Cardiac surgery, aorta, atherosclerosis, surgical clamp, embolism, stroke
National Category
Surgery
Research subject
Thoracic and Cardivascular Suregery
Identifiers
urn:nbn:se:umu:diva-38073 (URN)10.3109/14017431.2010.501867 (DOI)
Available from: 2010-11-24 Created: 2010-11-24 Last updated: 2017-12-12Bibliographically approved
5. Cannulation of the noncalcified aorta generates particles of microembolic nature: an experimental study using pig aorta
Open this publication in new window or tab >>Cannulation of the noncalcified aorta generates particles of microembolic nature: an experimental study using pig aorta
2008 (English)In: Journal of cardiac surgery, ISSN 0886-0440, E-ISSN 1540-8191, Vol. 23, no 1, 39-43 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND AND AIM OF THE STUDY: Aortic cannulation during cardiac surgery is a potential etiological factor for perioperative stroke. Cannulae may dislodge aortic-wall calcifications. In addition, the sharp edge of the cannula-tip may shear off vessel-wall tissue, which can be expelled into the lumen. This hypothesis concerning source of emboli was tested in a noncalcified aortic perfusion model.

METHODS: Pig aortas were pressurized and cannulated. Washout samples were collected before and after cannulation (n = 40). Particles were deposited onto a 10-microm filter and evaluated by microscopy and digital image analysis.

RESULTS: A higher incidence of particles generated by cannulation was noted as compared to before the maneuver (p < 0.001). This increase included small (<0.1 mm, p < 0.001) and intermediate-size particles (0.1-0.5 mm, p < 0.001). Particles above 0.5 mm were few and were not associated with cannulation.

CONCLUSIONS: Cannulation was a source of embolic material in the noncalcified aortic model. However, these particles were less than 0.5 mm in diameter and may contribute to neurocognitive decline after cardiac surgery.

Keyword
aorta and great vessels, cardiovascular research, perfusion
National Category
Surgery
Research subject
Thoracic and Cardivascular Suregery
Identifiers
urn:nbn:se:umu:diva-38076 (URN)10.1111/j.1540-8191.2007.00481.x (DOI)
Available from: 2010-11-24 Created: 2010-11-24 Last updated: 2017-12-12Bibliographically approved

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