From the Guidelines
When evaluating an EKG in a patient with syncope, be concerned about several critical findings that suggest potentially life-threatening cardiac causes, including bundle branch block, alternating bundle branch block, and bifascicular block, as these findings are associated with abnormal conduction properties and increased risk of high-degree AV block 1. These findings are concerning because they indicate electrical abnormalities that can cause sudden drops in cardiac output leading to cerebral hypoperfusion and syncope. Some key EKG changes to look for include:
- Prolonged QT interval (QTc >470ms in males, >480ms in females)
- Brugada pattern (characterized by ST elevation in V1-V3 with a coved or saddleback appearance)
- Ventricular pre-excitation (Wolff-Parkinson-White syndrome with short PR interval and delta waves)
- Complete heart block or high-degree AV block
- Ventricular tachycardia or evidence of prior ventricular tachycardia
- Significant bradycardia (<40 beats per minute)
- Bifascicular block (especially new onset)
- Signs of arrhythmogenic right ventricular cardiomyopathy (epsilon waves or T-wave inversions in V1-V3) According to the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope, a resting 12-lead electrocardiogram (ECG) is useful in the initial evaluation of patients with syncope, as it can provide information about the potential and specific cause of the syncope episode 1. Additionally, the presence of certain ECG findings, such as atrial fibrillation, intraventricular conduction disturbances, voltage criteria for left ventricular hypertrophy, and ventricular pacing, are associated with increased risk of death from all causes at 1 year 1. It is also important to note that patients with bundle branch block, especially those with alternating bundle branch block, are at higher risk of developing high-degree AV block and may require further evaluation, such as electrophysiological studies (EPS) 1. Patients with these findings often require urgent cardiology consultation, possible hospitalization for monitoring, and may need interventions such as pacemaker placement, defibrillator implantation, or antiarrhythmic medications depending on the specific abnormality identified.
From the Research
EKG Changes in Syncope
The following EKG changes in someone with syncope are concerning:
- Bradycardia, which can indicate a problem with the heart's electrical system 2
- Atrioventricular block, which can disrupt the normal flow of electrical signals in the heart 2
- Intraventricular conduction abnormality, which can affect the heart's ability to pump blood effectively 2
- Tachydysrhythmia, which can lead to inadequate blood flow to the brain and other organs 2
- Morphologic findings suggesting cardiovascular maladies, such as:
- ST-segment and T-wave abnormalities of acute coronary syndrome 2
- Ventricular preexcitation, as seen in Wolff-Parkinson-White syndrome 2
- Brugada syndrome, which can increase the risk of sudden death 2
- Prolonged QT interval, which can be associated with long QT interval presentations 2
- Right ventricular hypertrophy, which can be indicative of hypertrophic cardiomyopathy 2
- ST-segment elevation in lead aVR, which can indicate global ischemia of the myocardium and is often associated with obstructive coronary artery disease (CAD) 3
Specific EKG Presentations
Certain EKG presentations can provide a reason for the loss of consciousness and guide early therapy and disposition, including:
- Bradycardia, atrioventricular block, intraventricular conduction abnormality, and tachydysrhythmia in the appropriate clinical setting 2
- ST-segment elevation in lead aVR with or without diffuse ST depression, which can be caused by various etiologies, including severe anemia, drug overdose, and severe CAD 3