Coronary slow flow phenomenon: an angiographic curiosity.

Cardiologists are familiar with the phenomenon of slow progression of angiographic contrast in the coronary arteries in the absence of stenosis in the epicardial vessels in some patients presenting with chest pain. The coronary slow flow phenomenon (CSFP), first described in 1972, remains scantily studied. This phenomenon should be distinguished from occurrence of slow flow in the context of coronary reperfusion therapy such as angioplasty or thrombolysis that is associated with different pathophysiological and clinical implications. Similarly, coronary slow flow associated with coronary artery spasm, coronary artery ectasia (CAE), myocardial dysfunction, valvular heart disease and certain connective tissue disorders involving coronary microvasculature is easy to understand. CSFP may occassionly also result from inadvertent air-embolism during angiography or may be due to an overlooked ostial lesion. However, it is not certain whether CSFP in the absence of any of these known causes represents merely an angiographic curiosity or has special physiologic or therapeutic implications. In this editorial we focus on the current knowledge regarding CSFP manifesting in the absence of any known etiology.