Defining Metrics and the Framework for the Invasive Assessment of Patients with Presumed Coronary Microvascular and Vasomotor Dysfunction.

The objective of diagnostic investigations should be to confirm or refute the presence of abnormal coronary function and to identify patients who might benefit from specific therapeutic interventions. In the field of coronary microvascular and vasomotor dysfunction, progress toward this goal is hampered if diagnostic pathways differ amongst sites, the meaning of the results are unclear or the potential benefits of current therapies are not well established. In this second companion paper, we define the metrics that can be derived from the invasive assessment of the coronary function assessed in the Canadian Coronary Physiology Registry, discuss the theoretical and practical value and limitations of singular versus multiple combined metrics, and propose a flexible interpretative framework. We also provide early phenomapping analysis of the non-invasive data which both confirm the complexity and demonstrate the power of machine learning to unravel this problem. The combination of the multiple invasive metrics with the comprehensive clinical assessment will determine the phenotypic and pathophysiologic relevance of these metrics which will guide further research efforts.