From the Guidelines
An EKG is ordered for a patient with a syncopal episode to evaluate for cardiac causes of syncope, which can identify life-threatening conditions and guide further management, as recommended by the 2017 ACC/AHA/HRS guideline 1. The EKG can identify arrhythmias (such as bradycardia, tachycardia, or heart blocks), structural heart disease (like hypertrophic cardiomyopathy), conduction abnormalities (including prolonged QT interval or Brugada syndrome), or evidence of ischemia that might explain the loss of consciousness. Some key points to consider when ordering an EKG for a patient with a syncopal episode include:
- The EKG is widely available and inexpensive, and can provide information about the potential and specific cause of the syncope episode, such as bradyarrhythmia with sinus pauses or high-grade conduction block; ventricular tachyarrhythmia 1.
- The EKG may demonstrate an underlying arrhythmogenic substrate for syncope or sudden cardiac death (SCD), and subsets of patients with certain conditions (such as Wolff-Parkinson-White syndrome, Brugada syndrome, long-QT syndrome, hypertrophic cardiomyopathy, or arrhythmogenic right ventricular cardiomyopathy) have characteristic ECG features 1.
- A multicenter, prospective, observational study concluded that the presence of AF, intraventricular conduction disturbances, voltage criteria for left ventricular (LV) hypertrophy, and ventricular pacing were associated with increased risk of death from all causes at 1 year 1. The EKG should be performed as soon as possible after the event, ideally within 24 hours, as transient abnormalities may normalize over time. While a normal EKG doesn't rule out cardiac causes completely, it helps risk-stratify patients and guide further diagnostic workup, which may include echocardiography, Holter monitoring, or electrophysiology studies depending on clinical suspicion and EKG findings 1.
From the Research
Reasons for Ordering an EKG for a Patient with a Syncopal Episode
- To identify arrhythmias, which are the most common cardiac causes of syncope, as stated in the study 2
- To disclose an arrhythmia associated with a high likelihood of syncope, avoiding further evaluations and permitting institution of specific treatment in some patients, as mentioned in 2
- To assess the risk of major cardiovascular events or sudden cardiac death when the cause of syncope remains uncertain after initial evaluation, as discussed in 2
ECG Findings Suggestive of Cardiac Syncope
- Arrhythmias, such as bradycardia, atrioventricular block, intraventricular conduction abnormality, and tachydysrhythmia, as noted in 3
- Morphologic findings, including ST-segment and T-wave abnormalities of acute coronary syndrome, ventricular preexcitation, Brugada syndrome, prolonged QT interval, and right ventricular hypertrophy, as described in 3 and 4
- Signs of structural heart disease, such as myocardial infarction or cardiomyopathy, and signs of primary electrical disease, as mentioned in 4
Importance of ECG Monitoring in Syncope
- ECG monitoring is a well-established procedure in the work-up of patients with syncope or for diagnosing arrhythmias, as stated in 5
- A systematic approach and selection of ECG monitoring tools help permit an effective usage of the limited health care resources available for the management of unexplained syncope, as discussed in 5
- The gold standard for the diagnosis of syncope is a symptom-ECG correlation, as noted in 5