From the Guidelines
ECG changes associated with cardiovascular causes of syncope include ST-segment elevation or depression, prolonged QT interval, Brugada pattern, delta waves of Wolff-Parkinson-White syndrome, complete heart block, bifascicular block, ventricular pre-excitation, and evidence of prior myocardial infarction. These changes can identify underlying cardiac pathology, such as arrhythmias, conduction disorders, or structural heart disease, which can cause syncope by reducing cardiac output and cerebral perfusion 1.
Key ECG Findings
- ST-segment elevation or depression suggesting myocardial ischemia
- Prolonged QT interval indicating risk for torsades de pointes
- Brugada pattern with characteristic ST elevation in V1-V3
- Delta waves of Wolff-Parkinson-White syndrome
- Complete heart block with AV dissociation
- Bifascicular block
- Ventricular pre-excitation
- Evidence of prior myocardial infarction such as Q waves
Importance of ECG in Syncope Evaluation
ECG is widely available and inexpensive, and can provide information about the potential cause of syncope, such as bradyarrhythmia or ventricular tachyarrhythmia 1. Identifying these ECG changes is crucial for diagnosis and appropriate management, as cardiovascular causes of syncope often require specific interventions like pacemaker implantation, antiarrhythmic medications, or catheter ablation depending on the underlying condition.
Additional Considerations
Other significant ECG findings include sinus bradycardia below 40 beats per minute, sinus pauses exceeding 3 seconds, ventricular tachycardia, and supraventricular tachycardias 1. These findings can also indicate underlying cardiac pathology and guide further evaluation and management.
Guideline Recommendations
The 2017 ACC/AHA/HRS guideline recommends a resting 12-lead electrocardiogram (ECG) in the initial evaluation of patients with syncope, as it can provide information about the potential cause of syncope and guide further evaluation and management 1.
From the Research
ECG Changes Associated with Cardiovascular Causes of Syncope
ECG changes can be indicative of underlying cardiovascular conditions that may cause syncope. The following are some of the key ECG changes associated with cardiovascular causes of syncope:
- Left ventricular hypertrophy by voltage, repolarization abnormalities, QRS widening, pseudoinfarction patterns, and slurred QRS upstroke mimicking delta waves, which are common in hypertrophic cardiomyopathy (HCM) 2
- T-wave inversions and epsilon waves in the right precordial leads, which are characteristic of arrhythmogenic right ventricular dysplasia (ARVD/C) 2
- Coved ST-segments in the right precordial leads, associated with a history of syncope, ventricular arrhythmia, or sudden cardiac death in probands or family members, which is diagnostic of Brugada syndrome 2
- Wolff-Parkinson-White syndrome, long QT syndrome, and Brugada syndrome, which are important forms of primary electrical disease that may result in syncope 2
- J-point elevation or early repolarization pattern, which has been suggested to be associated with an elevated risk of sudden cardiac death 2
Diagnostic Criteria and Findings
The ECG may disclose an arrhythmia associated with a high likelihood of syncope, avoiding further evaluations and permitting institution of specific treatment in some patients 3. The following are some of the diagnostic criteria and findings suggestive of cardiac syncope:
- Bradycardia, atrioventricular block, intraventricular conduction abnormality, and tachydysrhythmia in the appropriate clinical setting 4
- Morphologic findings suggesting cardiovascular malady, including ST-segment and T-wave abnormalities of acute coronary syndrome, ventricular preexcitation, and prolonged QT interval 4
- Right ventricular hypertrophy suggestive of hypertrophic cardiomyopathy 4
Clinical Implications
The ECG is a mandatory diagnostic tool in the evaluation of syncope, although it may be normal in the majority of patients 3. The following are some of the clinical implications of ECG findings in patients with syncope: