The pulmonary circulation provides a large filter for any small thrombi returning from the systemic circulation. A small microthrombus to the lungs is probably insignificant but if the pulmonary circulation can be bypassed and shunted then there is a risk of thrombi entering the systemic arterial circulation. This can happen when there are areas allowing right to left shunting in the heart such as a patent foramen ovale or Atrial septal defect or Ventricular septal defect or other form of congenital heart disease. However, clots bypassing the lungs can be seen in those with pulmonary arteriovenous malformations.
Aetiology
Paradoxical Embolic Stroke = DVT + Right to left shunt
Causes
Cause Comments PFO Most are entirely innocent and seen in 25% of population but 50% with cryptogenic stroke. Closed by catheter if felt to be causative ASD Flow will usually go Left to right but here can be reversal. Get Echo. Bubble study. May be surgically closed VSD Flow will usually go Left to right but here can be reversal with Eisenmenger's syndrome. Get Echo. Bubble study. May be surgically closed Other Congenital heart disease with R/L shunt Flow will usually go Left to right but here can be reversal with Eisenmenger's syndrome. Get Echo. Bubble study. May be surgically closed Pulmonary AVM A lesion may be seen on CXR. Needs CTPA. Bubble study will show bubbles in LA after several cardiac cycles. Can be considered for occlusion by interventional radiologists
Investigations
Evidence Against Repeated Paradoxical embolism
Evidence For Repeated Paradoxical embolism
Management
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Paradoxical embolisation
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