The coronary slow flow phenomenon

Abstract

The coronary slow flow phenomenon (CSFP) is a microvascular coronary disorder, ­characterised angiographically by delayed contrast opacification of the distal vasculature in the absence of obstructive coronary artery disease. Its prevalence has been reported as 1–3 % of coronary angiograms performed. It often presents initially as an acute coronary syndrome with 8 % of patients having positive cardiac markers for myocardial infarction. Although transient T wave changes are frequently observed during the acute episode, only a third of patients have clinical evidence of inducible myocardial ischaemia. Both structural and functional studies have demonstrated the presence of microvascular coronary dysfunction however the underlying cause remains elusive. Possible pathogenetic mechanisms include a defective endothelial nitric oxide pathway, excessive endothelin mediated vasoconstriction, autonomic dysfunction, platelet dysfunction, metabolic derangements (associated with the metabolic syndrome and hyperhomocystinaemia), and vascular inflammation. The risk of future cardiac events following the initial presentation appears low however many patients continue to experience recurrent chest pain. Further well-controlled therapeutic studies are required to identify effective therapies for this disabling condition.