A case of coronary microvascular spasm with slow flow induced by the intracoronary acetylcholine provocation test

Role of acetylcholine spasm provocation test as a pathophysiological assessment in nonobstructive coronary artery disease

Coronary angiography (CAG) sometimes shows nonobstructive coronary arteries in patients with suspected angina or acute coronary syndrome (ACS). The high prevalence of nonobstructive coronary artery disease (CAD) in those patients has recently been reported not only in Japan but also in Western countries, and is clinically attracting attention. Coronary spasm is considered to be one of the leading causes of both suspected stable angina and ACS with nonobstructive coronary arteries. Coronary spasm could also be associated with left ventricular dysfunction leading to heart failure, which could be improved following the administration of calcium channel blockers. Because we rarely capture spontaneous attacks of coronary spasm with electrocardiograms or Holter recordings, an invasive diagnostic modality, acetylcholine (ACh) provocation test, can be useful in detecting coronary spasm during CAG. Furthermore, we can use the ACh-provocation test to identify high-risk patients with coronary spasm complicated with organic coronary stenosis, and then treat with intensive care. Nonobstructive CAD includes not only epicardial coronary spasm but also microvascular spasm or dysfunction that can be associated with recurrent anginal attacks and poor quality of life. ACh-provocation test could also be helpful for the assessment of microvascular spasm or dysfunction. We hope that cardiologists will increasingly perform ACh-provocation test to assess the pathophysiology of nonobstructive CAD.

Decreased coronary blood flow velocity in two patients with coronary microvascular spasm: case series†

Introduction

Diagnostic criteria for coronary microvascular spasm (CMS) have not yet been fully established.

Case presentation

We present two cases of CMS in which decreased coronary blood flow velocities were observed during acetylcholine (ACH) provocation tests. The first patient suffered from chest pain occurring while at rest. The patient underwent coronary angiography (CAG), which revealed a decrease in the average peak velocity (APV) from 29 cm/s to 14 cm/s and a slow flow phenomenon following ACH injection. The second patient suffered from chest pain occurring during the night. The patient underwent CAG, which revealed a decrease in the APV from 17 cm/s to 7 cm/s with no significant epicardial coronary artery spasm following ACH injection. Both patients complained of chest pain, and electrocardiogram changes were observed in leads equivalent to the distal area of the vessel during an ACH provocation test. These findings were consistent with CMS, and their conditions improved under medical treatment.

Discussion

A transient decrease in coronary blood flow velocity following ACH administration might be a phenomenon specific to CMS. These cases may provide some insight into the underlying pathophysiology of CMS.