The diagnostic yield from cardiac electrophysiology ranges
from 14–70%. This variability is primarily dependent on the char-
acteristics of patients studied, in particular the absence or
presence of co-morbid cardiovascular disease.^12 Thus despite the
use of investigations such as head up tilt testing, ambulatory
cardiac monitoring, external loop recorders and electro-
physiological testing, the underlying cause of syncope remains
unexplained and continues to pose a diagnostic problem.
The implantable loop recorder (ILR) is a new diagnostic tool to
add to the strategies for investigation of unexplained syncope.^12 It
permits long term cardiac monitoring to capture the ECG during a
spontaneous episode in patients without recurrence in a
reasonable time frame. It should be considered in those who have
already completed the above outlined investigations that have
proved negative, and in those in whom the external loop recorder
has not yielded a diagnosis in one month. The ILR is implanted
under local anaesthetic via a small incision usually in the left
pectoral region. It has the ability to “freeze” the current and
preceding rhythm for up to 40 minutes after a spontaneous event
and thus allows the determination of the cause of syncope in most
patients in whom symptoms are due to an arrhythmia. The
activation device, used by the patient, family member or friend
freezes and stores the loop during and after a spontaneous
syncopal episode. This is retrievable at a later stage using a
standard pacemaker programmer. The ILR specifically monitors
heart rate changes. Hypotensive syndromes including vasovagal
syncope, orthostatic hypotension, post-prandial hypotension and
vasodepressor carotid sinus hypersensivity may also cause
syncope. An ability to record blood pressure variation in addition
to heart rate changes during symptoms would be a very helpful
and exciting addition to the investigation of people with syncope.
RReeffeerreenncceess
1 Brady PA, Shen WK. Syncope evaluation in the elderly. Am J Geriatr
Cardiol1999; 88 : 115–24.
2 Kapoor W. Syncope in older persons. J Am Geriatr Soc1994; 4422 : 426–36.
3 Lipsitz L. Syncope in the elderly. Ann Intern Med1983; 9999 : 92–105.
4 Kapoor W. Diagnostic evaluation of syncope. Am J Med1991; 9900 : 91–106.
5 Gibson TC, Heitzman MK. Diagnostic efficacy of 24 hour electro-
cardiographic monitoring for syncope. Am J Cardiol1984; 5533 : 1013–17.
6 Clark PI, Glasser SO, Spoto E. Arrhythmias detected by ambulatory
monitoring; lack of correlation with symptoms of dizziness and
syncope. Chest1990; 7777 : 722–5.