Pulmonary embolism electrocardiogram

Associate Editors-in-Chief: Ujjwal Rastogi, MBBS [mailto:urastogi@perfuse.org]

Overview
ECG abnormalities exist in both patients with and without PE who do not have preexisting cardiovascular disease thus limiting it's diagnostic usefulness. ECG findings may be normal as well. A prospective study, reported 70% of acute PE patients to have ECG abnormalities, most commonly nonspecific ST-segment and T-wave changes.

Electrocardiogram
An electrocardiogram (ECG) is routinely done on patients with chest pain to rule-out myocardial infarctions (heart attacks).


 * The most common ECG finding is anterior T-wave inversion.
 * This likely represents reciprocal changes reflecting infero-posterior ischemia due to compression of the right coronary artery (RCA) as a result of pressure overload in the right ventricle (RV).
 * Sinus tachycardia, right bundle branch block (RBBB) are also frequently seen, but again are not sensitive or specific.
 * An ECG may show signs of right heart strain or acute cor pulmonale in cases of large PEs - the classic signs are a large S wave in lead I, a large Q wave in lead III and an inverted T wave in lead III (S1Q3T3). This is present in upto 20% patient, but may also occur in other acute lung conditions and has therefore limited diagnostic value.

The most common sign, seen in the ECG tracing of a PE patient is sinus tachycardia, but it lacks specificity.

The presence of Q waves in anterior leads wih coved ST-elevation after PE has also been described in few case reports.

Prognostic Assessment
ECG findings associated with poor prognosis are:
 * 1) Atrial arrhythmias
 * 2) Right bundle branch block
 * 3) Inferior Q-waves
 * 4) Precordial T-wave inversion and ST-segment changes.
 * 5) Development of QR wave in lead V1 is identified as an independent risk factor for an adverse prognosis.