What are the electrocardiogram (EKG) changes in pulmonary embolism (PE)?

From the Guidelines

Electrocardiogram (EKG) changes in pulmonary embolism (PE) are often nonspecific but can provide valuable diagnostic clues, with the most recent guidelines suggesting that EKG signs of RV strain, such as inversion of T waves in leads V1–V4, a QR pattern in lead V1, and incomplete or complete right bundle-branch block, may be helpful in diagnosis 1. The classic EKG finding in PE is the S1Q3T3 pattern, consisting of an S wave in lead I, Q wave in lead III, and T wave inversion in lead III, though this is present in only a small percentage of cases. More commonly, sinus tachycardia is observed, occurring in PE patients as the heart attempts to compensate for decreased cardiac output. Right bundle branch block may develop due to right ventricular strain. T wave inversions in the precordial leads (V1-V4) and right precordial leads are frequently seen, reflecting right ventricular strain. Atrial arrhythmias, particularly atrial fibrillation or flutter, can occur as a result of right atrial dilation. ST segment depression or elevation may be present but is nonspecific. It's essential to note that up to 30% of patients with confirmed PE have normal EKGs, so a normal EKG cannot rule out PE, as stated in the 2008 European Society of Cardiology guidelines 1. The 2019 ESC guidelines on the diagnosis and management of acute pulmonary embolism do not specifically address EKG changes, instead focusing on diagnostic algorithms, anticoagulation therapy, and reperfusion options 2. These EKG changes reflect the pathophysiology of PE, where obstruction of pulmonary blood flow leads to increased pulmonary vascular resistance, right ventricular strain, and subsequent electrical changes in the heart. Some key points to consider when evaluating EKG changes in PE include:

• The presence of sinus tachycardia, which can indicate decreased cardiac output
• The development of right bundle branch block, which can result from right ventricular strain
• The presence of T wave inversions in the precordial leads, which can reflect right ventricular strain
• The potential for atrial arrhythmias, such as atrial fibrillation or flutter, due to right atrial dilation.

From the Research

EKG Changes in Pulmonary Embolism

The electrocardiogram (EKG) changes in pulmonary embolism (PE) can be summarized as follows:

• An S1Q3 pattern is a common EKG finding in patients with PE, observed in 34 patients out of 51 in one study 3
• A "septal embolic pattern" is also observed in patients with PE, found in 27 patients out of 51 in the same study 3
• Anterior lead T-wave inversion is another EKG abnormality seen in patients with PE, present in 8 patients out of 51 3 and in 68% of patients in another study 4
• New right bundle branch block is also observed in patients with PE, found in 7 patients out of 51 3 and in 27.3% of patients in another study 5
• Right bundle branch block pattern, S-wave in the first standard lead, and S-wave in the aVL lead are also common EKG findings in patients with PE, observed in 27.3%, 64.5%, and 70% of patients, respectively 5
• T-wave inversion in the precordial leads is the most common abnormality, representing the EKG sign best correlated to the severity of the PE 4
• Abnormal changes in right-sided ECG, such as T-wave inversion, ST segment elevation, and QS pattern, are associated with an increase in right to left ventricular diameter ratio and higher pulmonary embolism severity index (PESI) score 6

Prognostic Value of EKG Changes

The prognostic value of EKG changes in patients with PE can be summarized as follows:

• The resolution of EKG signs, such as S-wave in the first lead, S-wave in the aVL lead, and right bundle branch block, is associated with 30-day survival and a decrease in right ventricular systolic pressure 5
• The presence of right bundle branch block at admission is significantly associated with 30-day all-cause mortality 5
• The anterior subepicardial ischemic pattern is a strong marker of severity and its reversibility is correlated to the changes in PE 4
• ST segment elevation in right precordial leads is an independent predictor for PESI score in patients with moderate and high 30-day mortality risk 6