Invasive assessment of the coronary microcirculation in the catheter laboratory

•Physiologic assessment of major epicardial vessels is well established.•Abnormal coronary microcirculation is associated with worse clinical outcomes.•Many techniques exist for assessment of the microcirculation.•Techniques may be angiographic or wire-based.•Current assessment of microcirculation best suited to STEMI.

Historically much of our understanding of the coronary circulation has been centered towards the epicardial vessels. However, recent work has highlighted the importance of the coronary microcirculation across a broad spectrum of clinical conditions in influencing patient outcomes. Therefore an ability to measure microvascular function is most valuable. While evaluation of the epicardial coronary circulation is widely understood, interrogation of the coronary microcirculation is more complex. Many methods are available to assess the integrity of the microcirculation in the catheter laboratory. This review will discuss the physiology of the coronary microcirculation and evaluate the utility of available invasive techniques.