Date of Award

2012

Document type

Thesis

Degree Name

MD (Medical Doctor)

First Supervisor

Dr Joan T Moroney

Keywords

Brain Ischemia

Abstract

Background:

Transoesophageal echocardiographic (TOE)-defined mobile, thread-like valvular strands (VS) have been associated with acute ischaemic stroke (AIS). The relationship between VS as a possible embolic substrate and the risk of recurrent stroke remains unclear. Our primary aims were to measure the prevalence of VS and explore their association with AIS in a case-control study and then, compare the risk of subsequent poor vascular outcome (vascular events and vascular death) in the stroke cohort patients with or without VS in a follow-up study. Our secondary aims were to determine the relationship of VS to other potential cardiac sources of emboli in TOE, relationship of VS to diastolic dysfunction in stroke cohort on comparison with controls. In addition, we sought to evaluate the relationship of VS to ischaemic stroke subtype and infarct topography on neuroimaging, and also to determine the relationship of hypercoagulable states in young patients with VS in the stroke cohort.

Methods:

In the case-control study, the prevalence of VS was estimated from patients consecutively admitted with AIS and from patients underwent TOE for cardiac conditions (those with infective endocarditis and stroke were excluded) in our institution over a two year period. In the follow-up study, patients with AIS were followed to evaluate the risk of poor vascular outcome, including risk of recurrent stroke.

Results:

We recruited 170 patients with AIS and of those, 78 underwent TOE. In our case-control study, we found TOE-defmed VS in approximately half of the patients with AIS (38/78, 48.7%) compared to one-third of controls (29/89, 32.6%). VS were more commonly seen in stroke patients over the age of 60 years (21/34, 61.8%). Univariate analysis found an association between the presence of VS and risk of AIS (OR = 3.85 ,p = 0.05), but multivariate analysis reduced the strength of the association (OR = 2.15,p= 0.06). In stroke subtypes, high prevalence of VS was seen in cardioembolic stroke but it did not reach statistical significance (p = 0.52) and there was no increased frequency of VS in cryptogenic stroke subtype. Diastolic dysfunction was seen in 78.9 % of cases with VS and there was a strong association between diastolic dysfunction and VS in the case-control study (OR 7.75,/) = 0.005). There was no statistically significant association between infarct location (cortical, subcortical, brainstem or cerebellar) in neuroimaging and the presence of VS. There were only few young cases with abnormalities in laboratory testing for hypercoagulable conditions. The risk of recurrent stroke and survival without poor vascular outcome was not statistically different between cases with or without VS in our study (OR = 1.45, 95 % Cl 0.30 - 6.96,p = 0.64).

Conclusion:

We were able to demonstrate an association between valvular strands and acute ischaemic stroke in our case-control study, however, the strength of the association was reduced after multivariate analysis. We did not find any increased risk of poor vascular outcome or increased recurrent stroke risk in cases with or without VS. Our findings do not support the embolic potential of valvular strands and it may not be a risk factor for stroke.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

File Size

2.63 MB

Comments

A thesis submitted to the Royal College of Surgeons in Ireland for the degree of Doctor of Medicine from the National University of Ireland in 2012.

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