Relationship between pulmonary embolism (PE) and atrial fibrillation (AF)

If PE and AF occur together it is most likely that the PE is the cause of the AF.

The mechanism of the AF is said to be acute right ventricular dilatation with "strain" due to the embolus in the pulmonary circulation creating backpressure into the right ventricle.

If a patient presents with unexplained AF, look for an accompanying PE as the cause.

It is postulated that AF can cause PE if a clot originates in the right atrium rather than the left, but this is less common than clots originating from the right ventricle and more studies need to be done in this area.

References:

• Flegel K., When atrial fibrillation occurs with pulmonary embolism, is it the chicken or the egg?, CMAJ 1999;160:1181-2