A quick look at Pulmonary Embolisms

Acute pulmonary embolism (PE) is believed to affect anywhere from 1 in 250 to 1 in 1000 persons in the US each year. Potentially 1 in 10 patients with an acute pulmonary embolism may go into cardiac arrest within the first 60 minutes[1].

The working diagnosis of a PE in the field is likely to be based solely on clinical findings. Therefore, prehospital providers should be familiar with the most common physical findings:

1. Tachycardia
2. Tachypnea
3. Dyspnea
4. Persistently low SaO2
5. Recent history of syncope
6. Hypotension
7. Cyanosis or pallor
8. Diaphoresis
9. Hemoptysis
10. Low grade fever
11. Diminished lung sounds

Additionally, prehospital providers should be familiar with the common ECG findings in acute pulmonary embolisms (in order of prevalence):

1. Sinus tachycardia (73%)
2. Prominent S1 (73%)
3. "Clock-wise" rotation (56%)
4. Negative T in 2+ precordials (50%)
5. Incomplete or complete RBBB (20-68%)
6. P-pulmonale (28-33%)
7. Axis shift, generally RAD (23-30%)
8. No significant findings (20-24%)
9. S1Q3T3 (12-25%)
10. Supraventricular arrhythmias (12%)

Note that 1 in 5 patients are likely to have no significant ECG findings. What this should stress is the field diagnosis of a PE will lean heavily on your clinical assessment and findings. Chou[2] notes that in one study only 5 patients of 64 were diagnosed with a PE based on ECG findings.

A combination of any of these physical and electrocardiographic findings strongly favor PE and prehospital providers should act accordingly. Unrecognized pulmonary embolisms may be rapidly fatal.

References

1. Galvagno SM. Emergency Pathophysiology: Clinical Applications for Prehospital Care. Teton New Media (2003). [ISBN 1591610079]
2. Surawics B, Knilans TK, Chou TC. Chou's Electrocardiography in Clinical Practice: Adult and Pediatric. Saunders/Elsevier (2008), 6th ed. [ISBN 1416037748]