From the Guidelines
The most common ECG changes associated with pulmonary embolism (PE) include sinus tachycardia, atrial arrhythmias, low voltage, Q waves in leads III and aVF, S1Q3T3 pattern, Qr pattern in V1, P pulmonale, right-axis deviation, ST-segment elevation, ST-segment depression, QT prolongation, and incomplete or complete right bundle-branch block, as reported in the 2011 American Heart Association scientific statement 1. These ECG changes occur due to right ventricular pressure overload and strain resulting from pulmonary arterial obstruction. The sudden increase in pulmonary vascular resistance leads to right ventricular dilation and dysfunction, which manifests as these characteristic ECG abnormalities.
- Key ECG findings that correlate with worse short-term prognosis in acute PE include:
- Sinus tachycardia
- New-onset atrial arrhythmias
- New right bundle-branch block (complete or incomplete)
- Qr pattern in V1
- S1Q3T3 pattern
- Negative T waves in V1 through V4
- ST-segment shift over V1 through V4, as noted in the study 1. However, it's essential to note that ECG findings in PE are often nonspecific and may be absent in some confirmed cases. Therefore, while these ECG changes can raise suspicion for PE, they should not be used alone for diagnosis, and further testing such as D-dimer, CT pulmonary angiography, or ventilation-perfusion scanning is necessary to confirm the diagnosis.
From the Research
EKG Changes Associated with Pulmonary Embolism
The electrocardiogram (ECG) may be entirely normal in patients with pulmonary embolism (PE), or it may show various rhythm and morphologic abnormalities 2. Some common ECG changes associated with PE include:
- Arrhythmias, such as sinus tachycardia, atrial flutter, atrial fibrillation, atrial tachycardia, and atrial premature contractions 2
- Nonspecific ST segment/T wave changes 2
- T wave inversions in the right precordial leads 2, 3
- Rightward QRS complex axis shift and other axis changes 2
- S1Q3 or S1Q3T3 pattern 2, 3
- Right bundle branch block 2
- Acute cor pulmonale 2
- QTc prolongation with new T-wave inversion in leads III, aVF, and V1-V3, and ST-segment depression in leads V5-V6 3
- S-wave notch in lead V1 and clockwise rotation with sinus tachycardia 3
- Transient atrioventricular junctional rhythm followed by sinus arrest 3
Mechanism of EKG Changes
The mechanism responsible for these ECG changes may be associated with myocardial ischemia, acute right ventricular overload, or vagal reflex 3.
Clinical Significance
These ECG changes can be used to support the diagnosis of PE, especially in patients with symptoms such as chest pain, shortness of breath, or syncope 4, 2. However, it is essential to note that the ECG may be normal in some patients with PE, and further diagnostic testing, such as chest imaging, may be necessary to confirm the diagnosis 4.