Physiological assessment of coronary stenosis: a view from the coronary microcirculation

The complexity of ischemic heart disease (IHD) comprehends disease in the succeeding perfusion domains of the vascular tree. Fractional flow reserve and coronary flow reserve are validated diagnostic modalities to identify myocardial ischemia, but solitarily do not suffice to objectify the respective contribution of obstructive and nonobstructive disease to IHD. Combined pressure and flow measurements deliver a comprehensive intracoronary assessment of IHD, although fractional flow reserve and coronary flow reserve disagree in 40% of the cases. Discrepancy between the indices does not reflect methodological failure, but explores divergent extremes of epicardial and microvascular disease, which holds vital prognostic value. We advocate critical revision of the current diagnostic and therapeutic approaches toward IHD. In this review, we deliver a perspective on the future developments in the diagnosis and treatment of IHD.