Ambulatory cardiac telemetry has been shown to be effective in establishing diagnoses in patients with suspected arrhythmias. A critical component of ambulatory telemetry is the immediate transfer of rhythm information to a central monitoring station without requiring patient action. The frequency with which potentially life-threatening events are detected using ambulatory telemetry has not previously been evaluated in a large patient population. All patients (n = 26,438) who underwent monitoring from April to December 2008 at a single service provider formed the patient population of this study. Arrhythmic events noted in these patients were defined as those requiring physician notification and those that represented potentially life-threatening arrhythmias. Of the 26,438 patients included in the study, 5,459 (21%) had arrhythmic events meeting physician notification criteria during a mean monitoring period of 21 days. Of these, 262 patients (1%) had arrhythmic events that could potentially be classified as emergent. These included 120 patients with wide complex tachycardia ≥15 beats at ≥120 beats/min, 100 patients with pauses ≥6 seconds, and 42 patients with sustained heart rates <30 beats/min. An additional 704 patients (3%) had narrow complex tachycardia ≥180 beats/min at rest. In conclusion, approximately 1% of patients who underwent ambulatory telemetry for routine clinical indications experienced life-threatening arrhythmic events over a 3-week monitoring period. Ambulatory cardiac telemetry could be potentially lifesaving in this group of patients.
Patients who complain of intermittent symptoms such as palpitations or syncope represent a difficult diagnostic dilemma. A number of techniques have been developed to detect potential arrhythmic causes with intermittent symptoms. These include Holter monitoring, patient-activated intermittent event recorders with or without looping memory, auto-triggered memory loop recorders, and ambulatory cardiac telemetry. Several studies have compared these techniques and shown that the diagnostic yield of ambulatory cardiac telemetry is at least as high as that of other techniques. One unique feature of ambulatory cardiac telemetry is the ability to immediately detect life-threatening arrhythmias and transmit data to a central monitoring station without patient action. Thus, ambulatory cardiac telemetry has the potential to detect dangerous arrhythmias in real time and allow immediate transmission and rapid intervention. However, the actual incidence of these arrhythmias in clinical use has not been previously evaluated in a large population. The purpose of the present study was to use the database of a large independent diagnostic testing facility (IDTF) to evaluate the incidence of potentially life-threatening arrhythmias using ambulatory cardiac telemetry.
Methods
The study was designed as a retrospective analysis of patient characteristics, diagnostic yield, and diagnoses of patients in a large commercial database (LifeWatch Services, Inc., Rosemont, Illinois). The LifeWatch ambulatory cardiac telemetry device consists of a small, lightweight sensor and electrodes worn on the chest that records the heart’s rhythm. Each heartbeat is transmitted wirelessly to a cellular phone monitor, in which it is analyzed by a proprietary algorithm that is resident within the monitor. If an arrhythmia is detected, the cellular phone monitor automatically transmits it to a central station for review and intervention, if appropriate.
Consecutive patients presenting for ambulatory cardiac telemetry from April to December 2008 were included. The groups consisted of a consecutive series of 26,438 patients, representing a variety of diagnoses. The database contained baseline demographic information and a brief clinical history for each patient. LifeWatch’s device contains programmable features that allow physicians to select criteria for transmission. Because this was a retrospective analysis, changes in programming may have been present in some patients; default programming criteria are listed in Table 1 . Arrhythmic events were identified using a proprietary algorithm and reviewed by ≥2 trained certified cardiac technicians. In this large IDTF’s database, review of individual tracings by the investigators was not feasible.
| Trigger Type | Default Setting | Rate (beats/min) | Onset Duration (seconds) |
|---|---|---|---|
| Atrial fibrillation | On | 30 | |
| Tachycardia | On | 150 | 10 |
| Bradycardia | On | 40 | 25 |
| Pause | On | 3 |
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