The Impact of Coronary Physiology on Contemporary Clinical Decision Making

Physiological assessment of coronary artery disease (CAD) has become one of the cornerstones of decision making for myocardial revascularization, with a large body of evidence supporting the benefits of using fractional flow reserve and other pressure-based indexes for functional assessment of coronary stenoses. Furthermore, physiology allows the identification of specific vascular dysfunction mechanisms in patients without obstructive CAD. Currently, more than 10 modalities of functional coronary assessment are available, although the overall adoption of these physiological tools, of either intracoronary or image-based nature, is still low. In this paper the authors review these modalities of functional coronary assessment according to their timing of use: outside the catheterization laboratory, in the catheterization laboratory prior to the percutaneous coronary intervention (PCI), and in the catheterization laboratory during or after PCI. The authors discuss how the information obtained can be used in setting the indication for PCI, in planning and guiding the procedure, and in documenting the final functional result of the intervention. The advantages and limitations of each modality in each setting are discussed. Furthermore, the key value of intracoronary physiology in diagnosing mechanisms of microcirculatory dysfunction, which account for the presence of ischemia in many patients without obstructive CAD, is revisited. On the basis of the opportunities generated by the multiplicity of diagnostic tools described, the authors propose an algorithmic approach to physiological coronary investigations in clinical practice, with the key aims of: 1) avoiding unneeded revascularization procedures; 2) improving procedural PCI and long-term outcomes in patients with obstructive CAD; and 3) diagnosing vascular dysfunction mechanisms that can be effectively treated in patients with NOCAD. The authors believe that such structured approach may also contribute to the wider adoption of available technologies for functional assessment of patients with CAD.