Pulmonary embolism

ECG

Sinus Tachycardia
- Don’t need tachycardia to have a PE. Seen in only ~30% of patients, but signals increased oxygen demand
Atrial and ventricular dysrhythmias
- SVT, atrial fibrillation, atrial flutter, etc.
- SVTs (AVNRT, AVRT, atrial and junctional tachycardias, etc.) have been shown to be an independent predictor of subsequent clinical deterioration
ECG Signs of RV strain
- Rightward axis (look for large S wave in lead I)
  - S1Q3 or S1Q3T3
    - (McGinn White pattern)
    - not sensitive or specific
      - unless large S wave
- Conduction delays and repolarization abnormalities
  - New RBBB or incomplete RBBB
  - Look for tall R waves in V1
- New T-wave inversions
  - Right precordial leads (V1-V4)
  - Inferior leads (II, III, aVF)
  - New T wave inversions in the anteroseptal leads +/- inferior leads should be considered a sign of acute pulmonary hypertension or PE until proven otherwise
- ST-segment elevations or depressions (mimics ischemia)
- ST-segment elevation in rightward leads (V1, V2, aVR, III)

Co, et al. J Emerg Med 2017 (PMID: 27742402) – identified the most common ECG changes in patients with known PE when comparing their ECGs with previous ECGs

285 PEs diagnosed on CTA (62% segmental, 20% in main pulmonary artery, 8% saddle)
- No ECG changes ~ 24%
- TWI ~ 34%
  - sensitive V1-V3
  - specific: also III, aVF
- T wave flattening ~ 30%
- Sinus tachycardia ~ 27%
- Rightward axis ~ 11%
- ST segment changes ~ 9%
- S1Q3T3 ~ 4%

ECG findings a/w hemodynamic instability & ↑ morbidity + mortality:

TWIs in right precordial leads
ST-segment elevation and depression
- Especially STE in V1-V2, aVR, III
Signs of right heart strain (right axis deviation, tall R wave in V1)
Tachycardia
- (sinus, afib/flutter)

References

McGinn S, White PD. Acute cor pulmonale resulting from pulmonary embolism: its clinical recognition. JAMA. 1935; 7104:1473–80. https://doi.org/10.1001/jama.1935.02760170011004

Co I, Eilbert W, Chiganos T. New Electrocardiographic Changes in Patients Diagnosed with Pulmonary Embolism. J Emerg Med. 2017;52(3):280-285. PMID: 27742402