Myocardial ischemia occurs when myocardial oxygen demand exceeds coronary blood supply. The etiology is usually atherosclerotic obstructive epicardial coronary artery disease (CAD). However with this being said, the angiographic evidence of “normal” or mildly diseased epicardial coronary arteries, usually defined as the absence of a luminal diameter reduction of ≥50% (or >70% of the luminal area reduction), is a common finding, documented in approximately 25% of patients with chest pain undergoing coronary angiography. This condition is usually defined as ischemia with no obstructive coronary arteries (INOCA) and likely related to so-called microcirculatory or microvascular dysfunction.

In addition, in a substantial proportion of patients with acute coronary syndromes, normal or near normal coronary angiograms are found. This condition is known as myocardial infarction with no obstructive coronary arteries (MINOCA). Moreover, microvascular dysfunction is a major player in the no reflow phenomenon in primary percutaneous coronary intervention (PCI) for STEMI.

As such, microvascular dysfunction constitutes a therapeutic problem with considerable residual morbidity associated with functional limitations, reduced quality of life, and increasing economic burden for the health authority system.

The mechanisms underlying the development of microvascular dysfunction are multifactorial and only partly explained by current research. Established diagnostic tools for assessing microvascular disease are not readily available in most cath labs, leaving many patients with no, or a wrong, diagnosis. Therefore, a growing part of the interventional cardiology community is looking for available means to diagnose and quantify microvascular dysfunction in order to find the appropriate and accurate diagnosis for the individual patient. In this special issue, we aim to update the available and emerging strategies for assessing microvascular dysfunction .We invite authors to submit manuscripts pertaining to the current and emerging mechanisms and the potential related targets for future therapy. We welcome both original research papers and review articles.

Potential topics include but are not limited to the following:

• Invasive assessment of myocardial microvascular physiology in healthy persons and in patients with chest pain (chronic and acute coronary syndromes CCS and ACS) and ischemia and normal coronary arteries (INOCA/MINOCA)
• The coronary microcirculation after revascularization
• Invasive assessment of microvascular physiology in chronic total occlusions (CTOs)
• Invasive assessment of the coronary microcirculation in acute coronary syndromes
• The coronary microcirculation during cardiogenic shock
• The coronary microcirculation in aortic stenosis
• The coronary microcirculation in heart failure