This document discusses left atrial thrombus in patients with rheumatic mitral stenosis. It finds that 26-33% of patients with severe mitral stenosis have left atrial thrombi, which are associated with a higher risk of embolic events. The document classifies different types of left atrial thrombi and examines determinants of thrombus formation like atrial fibrillation, left atrial size, and severity of mitral stenosis. It recommends anticoagulation to reduce thromboembolic risk, noting studies have found anticoagulation facilitates thrombus resolution.

1. LEFT ATRIUM THROMBUS
23-12-2014

2.  Introduction
 Determinants
 Classification
 Management
 Conclusions

3.  Patients with severe symptomatic MS, 50% or more
have chronic AF.
 The incidence of thromboembolic complications is
higher in patients with rheumatic mitral stenosis and is a
major cause of morbidity and mortality.
 The left atrium and left atrial appendage are well
recognised sites of clot formation in these patients.
 Patients with a clot in the left atrium and left atrial
appendage had a higher incidence of systemic
embolization.

4.  LA thrombi are reported to occur in 26-33% of
patients with severe mitral stenosis.
 LA thrombi were found in 20% of patients who
underwent surgery for mitral stenosis.
 The presence of LA thrombi was associated with a
threefold increase in embolic events.
 Fifty percent of LA thrombi in patients with
rheumatic valvular disease, and nearly 90% of LA
thrombi in patients with non-valvular AF are limited
to the LA appendage

5. DETERMINANTS
 Various factors determine the individual risk for the
development of left atrial clot and thromboembolization
in patients with rheumaticmitral valve disease which
include
 Atrial fibrillation
 Left atrial size
 Duration of symptoms
 Older age
 Severity of mitral stenosis
 However the presence of moderate to severe mitral
regurgitation has a negative predictive value for the
development of clot in the left atrium.

6. `

8. CLASSIFICATION
 The thrombus in the left atrium can be classified as
(Manjunath et al.) -
 Ia (thrombus confined to LAA)
 Ib (thrombus in LAA and protruding into LA cavity)
 IIa (attached to LA roof but above the plane of fossa ovalis)
 IIb (reaching below plane of fossa ovalis)
 III (attached to interatrial septum)
 IV (mobile with attachment to roof or lateral wall)
 V (ball valve thrombus)

13. SPONTANEOUS ECHO CONTRAST
 The incidence of spontaneous echo contrast in
mitral stenosis varies from 21 to 67%.
 Previous reports have shown that in majority or all,
left atrial clot and systemic thromboembolization
were associated with spontaneous echo contrast in
left atrium on transesophageal echocardiography.
 Spontaneous echo contrast was also found to be
an important predictor of systemic embolization,
independent of the presence of clot in LA clot.

14.  Fatkin et al, in a group of 140 patients who
underwent transesophageal echocardiography
found that the presence of SEC, not the presence
of clot in LA correlated significantly with previous
history thromboembolism.
 Acarturk et al, found that the presence of both
(spontaneous echo contrast and left atrial clot)
correlated significantly with thromboembolism.

16. MANAGEMENT
 Anticoagulation is conventionally used to reduce
the risks of thromboembolic events associated with
atrial fibrillation, particularly in the pericardioversion
period.
 The benefit is balanced by the high cost and risk of
anticoagulation.
 The mechanism by which warfarin achieves the
reported risk reduction is speculative.
 Earlier reports supported the hypothesis of
"thrombus maturation," by which the thrombus
endothelializes and adheres to the atrial wall.

17.  Coumarin anticoagulants such as warfarin act by inhibiting the
synthesis of vitamin Kdependent coagulation factors II, VII, IX,
and X.
 The primary effect of this form of anticoagulation is to prevent
further thrombus extension and development.
 It has been suggested that this will facilitate the action of the
endogenous fibrinolysis (ie, tissue plasminogen activator).
 Thrombus resolution has been demonstrated in clinical reports
on patients with left ventricular thrombi treated with 12 weeks
of warfarin.

21. CONCLUSIONS
 It can be stated that more than one third of the
patients with severe rheumatic MS and AF will have
LA thrombi.
 In a subgroup of the patients with normal sinus
rhythm, patients with larger left atrium (≥40 cm2 )
and spontaneous echo contrast have a higher risk
of clot formation in the LA/LAA.
 Anticoagulation appears to be facilitating LAC and
LA thrombus resolution, with an 80% short term
success rate.