Acute coronary syndromes in patients with angiographically normal or near normal (non-obstructive) coronary arteries

Patients with acute coronary syndrome (ACS) with normal or near-normal (non-obstructive) coronary arteries (ACSNNOCA) constitute an important, albeit heterogeneous, patient subset of younger patients, more commonly females, who may have lower risk of cardiovascular events compared to patients with obstructive coronary artery disease; however this risk remains substantial, hence needing further investigation to identify the underlying cause and devise a proper therapeutic strategy. A diagnostic algorithm starts during coronary angiography with some essential additional diagnostic steps, such as a left ventricular angiogram that may readily identify the underlying cause, e.g. Takotsubo syndrome, while intravascular imaging and vascular reactivity testing may need to be considered for assessing other diagnostic possibilities (e.g. occult atherosclerotic plaque rupture, spontaneous coronary dissection or microvascular dysfunction). Nevertheless, pursuing further investigation with less risky noninvasive tests, such as echocardiography and cardiac magnetic resonance imaging, may effectively identify the cause of ACSNNOCA (e.g. myocarditis or Takotsubo syndrome), and guide management.