Acetylcholine Rechallenge Testing for Coronary Vasospasm
- Acetylcholine (ACh) rechallenge is a novel testing method that can help differentiate between epicardial and microvascular vasospasm. Ach provocation is repeated 3 minutes after intracoronary nitroglycerin among patients with previously induced spasm.
- Coexisting spasm of both the epicardial and microvascular beds was noted in nearly half of the patients (48%).
- Nitroglycerin was most effective at relieving focal epicardial spasm (100%) followed by diffuse spasm (80%) and least effective against microvascular spasm (20%).
What is the feasibility and clinical value of acetylcholine (ACh) rechallenge for the detection of coexisting epicardial and microvascular spasm, and what is the efficacy of nitroglycerin in patients with known coronary spasm?
In this multicenter study, 95 patients with coronary spasm were included to undergo ACh rechallenge, which consisted of repeated ACh provocation 3 minutes after intracoronary nitroglycerin administration using the same dose that previously induced spasm.
In total, 95 patients (ages 61 ± 12 years, 69% female) were included. Fifty-five patients (58%) had microvascular spasm, and 40 patients (42%) had epicardial spasm during initial ACh provocation. In 48% of patients with epicardial spasm, ACh rechallenge revealed coexisting nitroglycerin-persistent microvascular spasm. Nitroglycerin administration before ACh rechallenge prevented reinducibility of epicardial spasm in all patients with focal spasm and in 80% of patients with diffuse spasm. Microvascular spasm was prevented in only 20% by prior nitroglycerin administration but was attenuated in another 49% of patients.
This study demonstrates a high frequency of epicardial spasm with coexisting nitroglycerin-persistent microvascular spasm. Intracoronary nitroglycerin was very effective in preventing reinducibility of epicardial spasm, whereas it prevented microvascular spasm in only 20% of patients. ACh rechallenge is a novel method that facilitates the detection of coexisting spasm endotypes and may pave the way towards tailored treatment of vasospastic angina.
The authors introduce ACh rechallenge as a novel testing method to help differentiate between epicardial and microvascular vasospasm. In addition, they assessed the efficacy of nitroglycerin in treating epicardial and microvascular spasm. Findings show that further classification of coronary spasm can be safely made using the ACh rechallenge and that coexisting epicardial and microvascular spasm appear to be common (48% of patients). In this study, nitroglycerin was most effective at relieving focal epicardial spasm (100%) followed by diffuse spasm (80%) and least effective against microvascular spasm (20%). ACh rechallenge testing could be an important diagnostic tool in not only differentiating between different types of vasospasm but also in studying treatment response.
Keywords: Acetylcholine, Angina Pectoris, Coronary Angiography, Coronary Vasospasm, Coronary Vessels, Diagnostic Techniques, Cardiovascular, Microcirculation, Nitroglycerin, Secondary Prevention, Spasm
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