Unmasking of a significant left main stenosis in a patient with high left ventricular pressures.

As identification of left main (LM) stenoses has prognostic and therapeutic relevance, a precise anatomic and/or functional characterization of angiographically intermediate LM stenoses, by using intravascular ultrasound (IVUS) and fractional flow reserve (FFR) respectively, is crucial (1). However, increased left ventricular (LV) pressures might affect FFR measurements (2). Here we describe the case of a patient with chronic coronary syndrome and severe LV dysfunction in whom coronary angiography revealed an intermediate LM stenosis and catheterization identified an increased LV end-diastolic pressure. FFR measurement showed disproportionally higher FFR values compared with the minimal luminal area assessed by IVUS. When cardiac output was artificially augmented by using Impella for assisting percutaneous coronary intervention, the value of FFR measurement turned out proportional to what expected for the degree of anatomical stenosis. This discrepancy between anatomic and functional measurement may be a sign of coronary autoregulation dysfunction and therefore could help to identify high-risk patients in whom the use of a mechanical support device is more beneficial during percutaneous revascularization.