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August 1, 2017 Circulation. 2017;136:e60–e122. DOI: 10.1161/CIR.0000000000000499 e72

3.2.3 Cardiac Monitoring: Recommendations

Although cardiac monitoring is often used in the evaluation of palpitations or intermittent arrhythmias, the following recommendations and discussion are focused primarily on the use of monitoring for the evaluation of patients with syncope. The choice of monitoring system and duration should be appropriate to the likelihood that a spontaneous event will be detected and the patient may be incapacitated and unable to voluntarily trigger the recording system.

3.2.2 Stress Testing: Recommendation

Recommendation for Stress Testing

COR LOE Recommendation IIa C-LD Exercise stress testing can be useful to establish the cause of syncope in selected patients who experience syncope or presyncope during exertion.132,143

See Online Data Supplement 10. Exertion can result in syncope in a variety of conditions, including structural lesions, such as hypertrophic obstructive cardiomyopathy and aortic stenosis; interarterial anomalous coronary artery and pulmonary arterial hypertension; and channelopathies, such as LQTS (type 1) and catecholaminergic polymorphic ventricular tachycardia (CPVT). Subjecting a patient to a treadmill exercise test to reproduce the symptoms or evaluate the hemodynamic response to exertion (eg, hypotension) must be done with extreme caution and in an environment with proper advanced life support.

In a prospective evaluation of 433 patients in which tachyarrhythmia was studied as the etiology for exertional syncope,132 an ECG stress evaluation was felt to be the sole test useful in identifying a presumptive cause of syncope in only 2 patients. However, bradyarrhythmia may ultimately be responsible for exertional syncope as well, and may only be elicited during stress testing. In rare instances, exercise-induced ischemia143–146 or coronary vasospasm147 may lead to high-grade/infranodal AV block in patients with underlying coronary disease.

Recommendations for Cardiac Monitoring

COR LOE Recommendations

I C-EO The choice of a specific cardiac monitor should be determined on the basis of the frequency and nature of syncope events.

N/A The technology of cardiac rhythm monitoring is dynamic and advancing at rapid speed. Several types of ambulatory cardiac rhythm monitoring are summarized in Table 8. Their selection and usefulness are highly dependent on patient characteristics with regard to the frequency of syncope and the likelihood of an arrhythmic cause of syncope.148

IIa B-NR To evaluate selected ambulatory patients with syncope of suspected arrhythmic etiology, the following external cardiac monitoring approaches can be useful: 1.  Holter monitor149–153

2.  Transtelephonic monitor150,154,155 3.  External loop recorder150,154–156 4.  Patch recorder157–159 5.  Mobile cardiac outpatient telemetry160,161

See Online Data Supplements 11 and 12. The types of external monitoring devices are summarized in Table 8. The effectiveness of any external cardiac monitoring device for syncope evaluation is related to the duration of monitoring, continuous versus intermittent monitoring, frequency of syncope, duration of prodrome, and suddenness of incapacitation. The patient activation, before or after an event, allows for symptom rhythm correlation; however, some external loop recorders are of limited use in patients who are temporarily incapacitated around the time of syncope. External loop recorders are also limited by infrequent syncopal events. The advantage of an external loop recorder over Holter monitoring stems from a longer monitoring period, which confers a higher yield than Holter monitoring149,153 and may offer a diagnosis after a negative Holter evaluation.150 Although the diagnostic yield of an external loop recordermay be lower than that of an implantable cardiac monitor (ICM), the noninvasive strategy is reasonable as a first approach. One prospective, multicenter study of 392 patients (28% with syncope) reported a 4-week diagnostic yield of 24.5%, with recurrent events and previous history of supraventricular arrhythmias being strong predictors of diagnostic events.156

The advances of new patch-based devices offer another and often less cumbersome means of identifying an arrhythmic cause for syncope.157–159 The duration of monitoring (2 to 14 days) is often shorter than for the external loop recorder or mobile continuous outpatient telemetry. Some practices offer mobile continuous outpatient telemetry devices, which provide real-time arrhythmia monitoring and analysis. An RCT161 of 266 patients with suspected intermittent arrhythmias demonstrated that an arrhythmia was diagnosed in 88% of mobile continuous outpatient telemetry patients versus 75% of external loop recorder patients (P=0.008). Importantly, therewas a similar result in the subgroup of patients presenting with syncope or presyncope, with a significantly higher diagnostic yield in the mobile continuous outpatient telemetry group (89% versus 69%; P=0.008).

IIa B-R To evaluate selected ambulatory patients with syncope of suspected arrhythmic etiology, an ICM can be useful.149,150,153,161–175

See Online Data Supplements 11 and 12. Several RCTs and observational studies have demonstrated a benefit of the ICM in establishing a diagnosis in syncope of unclear etiology. In a prospective study of 60 patients with syncope of unknown origin, the diagnosis (primarily bradyarrhythmia) was made in 55% with ICM, compared with a 19% diagnostic yield with conventional testing (external loop recorder, followed by tilttable testing and electrophysiological study [EPS]) (P=0.0014).162 These findings are consistent with other studies, which generally have shown that patients who underwent the ICM approach experienced higher rates of diagnosis than those of patients who underwent the conventional approach.164,176,177 A study on cost-effectiveness of the ICM strategy reported that the mean cost per participant was higher but the cost per diagnosis was lower in patients who received ICM than in patients who underwent conventional approaches.162,164,178 Key confounders in cost assessment include differences in healthcare settings, heterogeneity of patient populations, pricing of devices and healthcare delivery, and changing technology.

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