Coronary artery ectasia due to microfistulae.

The pathogenesis of coronary artery ectasia (CAE) is not fully understood and associated with a vast group of disorders. We present a rare case of CAE of the left coronary artery associated with microfistulae. Microfistulae bypass myocardial capillaries and decrease the distal blood flow. The coronary artery responds to this coronary steal phenomenon with a compensatory dilatation, causing diffuse ectasia to catch up for the considerable decrease in coronary diastolic perfusion pressure. Although segmental dilatation is frequently seen in association with hypertension, one should think of microfistulae as an underlying cause of diffuse coronary ectasia.