100 QUESTIONS IN CARDIOLOGY

76 What are the chances of a 24 hour tape

detecting the causes for collapse in a patient?

What other alternative monitoring devices are now

available?

RA Kenny and Diarmuid O’Shea

Syncope is a common medical problem accounting for up to 6% of

emergency medical admissions. In older patients presenting to

casualty this may be as high as 20% when evaluated with a full

cardiovascular work up. The annual recurrence rate is as high as

30%.^1 Syncope due to cardiac causes is associated with a high

mortality (>50% at 5 years) compared with 30% at 5 years in

patients with syncope due to non-cardiac syncope and 24% in

those with unexplained syncope.^2 However, in the elderly, even

“benign” syncope can result in significant morbidity and

mortality due to trauma, anxiety or depression, which may lead to

major changes in lifestyle or financial difficulties.^3

Syncope is often unpredictable in onset, intermittent and has a

high rate of spontaneous remission making it a difficult diagnostic

challenge. Thus even after a thorough work up, the cause of

syncope may remain unexplained in up to 40% of cases.^4

Prolonged ambulatory monitoring is often used as a first line

investigation. Documentation of significant arrhythmias or

syncope during monitoring is rare. At best, symptoms correlating

with arrhythmias occur in 4% of patients, asymptomatic

arrhythmias occur in up to 13%, and symptoms without

arrhythmias occur in up to a further 17%.5–7Prolonged monitoring

may result in a slight increase in diagnostic yield from 15% with 24

hours of monitoring to 29% at 72 hours.^8

Patient activated external loop recorders have a higher diagnostic

yield but do not yield a symptom-rhythm correlation in over 66% of

patients, either because of device malfunction, patient non-

compliance or an inability to activate the recorder.9,10In addition

such devices are only useful in patients with relatively frequent

symptoms. In a follow up by Kapoor et al,^11 only 5% of patients

reported recurrent symptoms at 1 month, 11% at 3 months and 16%

at 6 months. Thus this type of monitoring is likely to be useful only

in a small subgroup of patients with frequent recurrence in whom

initial evaluation is negative and arrhythmias are not diagnosed by

other means, such as 24 hour ECG or electrophysiology studies.