Coronary slow flow: description of a new "cardiac Y" syndrome.

Angina in the presence of intact coronary arteries remains a relatively frequent clinical issue. It is now well understood that an impaired capacity to modulate coronary vascular resistances upon exercise (i.e. an impaired coronary flow reserve) may lead to ischemia and angina. We describe a case of coronary slow flow, i.e. a condition in which resting (micro) vascular resistances are inappropriately high, causing unstable angina. We propose that this novel syndrome should be called coronary syndrome Y to distinguish it from the better understood coronary syndrome X.