Syncope: review of monitoring modalities

Abstract

Elucidating the underlying cause of unexplained syncope, palpitations or other possible arrhythmia-related symptoms is a formidable clinical challenge. Cardiac monitoring supplements the most important "test" in patients with syncope or palpitations, that of a thoughtful history and physical examination. Ideally, comprehensive physiologic monitoring during spontaneous symptoms would constitute what, at present, is an unattainable gold standard test for establishing a cause. Short of that goal, establishing an accurate symptom-rhythm correlation can often provide a diagnosis. Ambulatory outpatient monitoring is a powerful diagnostic tool for the evaluation of cardiac arrhythmias. Evolving technologies have provided a vast array of monitoring options for patients suspected of having cardiac arrhythmias, with each modality differing in duration of monitoring, quality of recording, convenience and invasiveness. Holter monitors, event monitors and external loop recorders are non-invasive and provide easily accessible short-term monitoring solutions. In instances where the diagnosis remains elusive, a more long-term strategy with an implantable loop recorder may be the preferred path.

Fig. (1). Holter Monitor.

The recording device is worn by the patient using a shoulder strap or belt loop, attaching to 3-5 skin electrodes for continuous monitoring. An event button (not shown) at the top of the housing of the device is pressed in the event of symptoms to mark the recording. See text for discussion.

Fig. (2). Transtelephonic Monitors.

The device is lightweight and portable. Four recording electrodes are present on the back of the device to permit single lead rhythm strip capture. A record button (top left) is pressed at the onset of symptoms, and the recorded event is transmitted to a base station over an analog phone line.

Fig. (3). Loop Recorders.

An external loop recorder (left) with cables that attach to the patient. The record button is pressed in the event of symptoms to store the previous 9 minutes, and the ensuing minute. The phone receiver is also placed over this button to transmit data over an analog phone line. An implantable loop recorder (center) and patient activator (right). The patient activator is used to “freeze” symptomatic events that are retrieved with a pacemaker programmer. Automatic events can also be captured (see text for discussion).

Fig. (4). External Loop Recorder Tracing.

Sinus rhythm during presyncope is recorded in a 43-year-old female with recurrent unexplained syncope and presyncope. The fluctuation in heart rate is suggestive of neurocardiogenic syncope.

Fig. (5). Automatic Event Detection from an ILR.

This is a typical tracing of an event captured by an ILR during syncope in a patient. The arrow and letter A denotes automatic activation when the device detects a 3 second pause. Each line constitutes 10 seconds of a single lead rhythm strip. Note the slowing of the sinus rate prior to onset of a prolonged pause, which resulted in syncope. This is consistent with the diagnosis of neurocardiogenic syncope (ISSUE classification 1A).

Fig. (6). Manual Event Detection from an ILR.

Manual activation during presyncope in a 73-year-old male with two previous episodes of unexplained syncope. There is subsequent sinus showing suggests a secondary vasovagal response.This is classified as a 1C response by the proposed ISSUE classification, suggesting intrinsic AV node disease.