From the Department of Clinical Neurosciences, King's College
School of Medicine and Institute of Psychiatry (M.C., H.M.); and Department of
Cardiology (R.W., A.B., M.M.), King's College Hospital, London, UK.
Correspondence to Dr Hugh Markus, Department of Clinical Neurosciences, Institute of Psychiatry, De Crespigny Park, London, SE5 8AF, UK. E-mail h.markus{at}iop.bpmf.ac.uk
Background and Purpose—Embolism
is believed to be the major cause of stroke in patients with
nonvalvular atrial fibrillation (NVAF). The detection of
asymptomatic embolic signals (ES) in individuals with NVAF
might allow identification of patients at high risk of stroke and
monitoring of therapy in individual subjects. We determined the
frequency of asymptomatic ES in patients with NVAF who were
not taking warfarin.
Methods—Bilateral transcranial Doppler
recordings were made for 1 hour from the middle cerebral
arteries of 111 successive patients with NVAF taking aspirin alone or
no antithrombotic or anticoagulant therapy. Adequate recordings
could be made in 86 patients. In 79 subjects, recordings were
performed on a second occasion to study temporal variability.
Recordings for a single hour were also made in 30 age-matched
control subjects.
Results—ES were detected in 13 (15.1%) of NVAF subjects but in
no control subjects (P=0.02). ES were detected both in
subjects with symptomatic NVAF (4 of 30 [13.1%],
P=0.04 versus controls) and asymptomatic
NVAF (9 of 56 [16.1%], P=0.02 versus controls). There
was no correlation between the presence of ES and smoking status,
diabetes, hypertension, aspirin use, aspirin dose,
symptomatic status, left atrial size, left
ventricular function, or the presence of left atrial
thrombus detected on transthoracic
echocardiography. Repeating the recording
increased the number of patients with ES to 21 (26.6%). On considering
the results of both recordings, again there was no association
for either recording between the presence of ES and smoking
status, diabetes, hypertension, aspirin use, aspirin dose, age,
symptomatic status, left atrial size, or left
ventricular function. On repeating the recording,
in the symptomatic group only 2 patients (8%) changed
status, in contrast to 15 (29%) in the asymptomatic
group.
Conclusions—ES can be detected in patients with NVAF at a low
frequency. Particularly in asymptomatic patients, ES show
marked temporal variability. We found no correlation between the
presence of previously reported clinical and
echocardiographic markers of increased stroke risk and
the presence of ES. This association requires further investigation
before the clinical utility of this technique in patients with NVAF is
decided.
© 1998 American Heart Association, Inc.
Original Contributions
Asymptomatic Embolization in Subjects With Atrial Fibrillation Not Taking Anticoagulants
A Prospective Study
Key Words: atrial fibrillation • cerebrovascular diseases • cerebral embolism • ultrasonics
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