Diagnostic potential of relative changes in high-sensitivity troponin levels during intracoronary acetylcholine provocation testing

Abstract Background Intracoronary acetylcholine (ACh) provocation testing is useful for the diagnosis of vasospastic angina (VSA). However, the positive or negative diagnosis of ACh testing is often challenging when lacking typical anginal symptoms and electrocardiographic changes during provocation tests. We hypothesized that relative changes in cardiac troponin levels during ACh provocation testing may be suggestive of myocardial ischemia and would be helpful for the VSA diagnosis. Purpose To evaluate the diagnostic potential of relative changes in high sensitivity troponin I (hs-TnI) levels during intracoronary ACh provocation test. Methods This preliminary study included a total of 29 patients undergoing invasive coronary angiography with or without ACh provocation tests. Patients were divided into three groups; no ACh provocation tests (i.e. angiography alone), negative ACh tests, and positive ACh tests. Blood samples were obtained twice, before and after angiography, through the arterial sheath to evaluate hs-TnI. The primary measure was relative changes in hs-TnI (i.e. Δhs-TnI). Positive ACh provocation test was defined as total or subtotal coronary occlusion accompanied by chest pain and/or ischemic electrocardiographic changes. Results Of the 29 patients, 10 (34.5%) underwent coronary angiography alone, while ACh provocation testing was performed in 19 (65.5%) patients, of whom 7 (36.8%) and 12 (63.2%) had negative and positive ACh test results. Overall, the mean time interval between the blood sample collections was 76 minutes. Levels of hs-TnI before angiography did not differ significantly in the no, negative, and positive ACh test groups (5.3 [2.8, 8.6] vs. 2.9 [1.3, 8.8] vs. 3.3 [1.6, 8.5] pg/ml, p=0.76), while Δhs-TnI was highest in the positive ACh test group, followed by the negative and no ACh test groups (4.2 [0.5, 8.1] vs. 0.8 [0.4, 4.6] vs. −0.3 [−0.6, 0.3], p=0.002) (Figure). Conclusions In patients undergoing intracoronary ACh testing for the VSA diagnosis, a relative increase in Δhs-TnI during angiography was observed than in those who did not undergo the provocation tests, particularly when the ACh test diagnosis was positive. Our findings suggest that Δhs-TnI has the potential to aid in the positive or negative diagnosis of ACh provocation testing.