Microcirculation by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783030281991
Publisher: Springer International Publishing

Role of Acetylcholine Vasomotor Testing (for Protocols Please Refer to Chap. 3)

In one of the largest cohort of INOCA patients (1379 patients) in Europe with Ach testing [16], one third were positive with a microvascular pattern, one quarter were positive with epicardial pattern, another third were ambiguous and less than one eights were normal. However, acetylcholine testing may be interpreted in two different ways. It might be used as a tool for coronary spasm diagnosis (especially when variant angina is suspected) or to evaluate endothelial ( epicardial and microcirculatory) function in different clinical settings. When the diagnosis of coronary spasm is challenged there are certain thresholds used (>90% reduction in luminal diameter together with ECG changes and reproduction of symptoms) [6]. However, when endothelial dysfunction is tested [17] the threshold for a positive result is either a diameter reduction of >20% (for epicardial endothelial dysfunction) or a flow increase of <50% (for microcirculatory dysfunction). These are based on the fact that in coronary arteries with normal endothelial function acetylcholine infusion induces an increase in epicardial artery diameter and flow, and this finding are associated with good prognosis. Several outcome studies showed significant differences in parameters of endothelial function between patients with and without events during follow-up, especially for epicardial endothelial function, and these differences remained predictive even after adjusting for the presence of cardiovascular risk factors [18, 19]. Consequently, it is difficult to determine based on available prognostic data which is the significance of epicardial narrowing between 20% and 75% (90)% and this might be important especially in patients with inconclusive results (one third of cases in the study mentioned earlier). Moreover, the doses of acetylcholine might be a matter of debate. In previous prognostic trials testing for endothelial dysfunction [20, 21] the doses were generally 18 μg/min (1 mL/min from solution 10−4 M) much smaller than those used for coronary spasm testing trials [16] in (up to 200 μg in 3 min) and also from those recommended in the last consensus from Japanese Circulation Society guidelines ( doses up to 100 μg injected over 20 s) [22].

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