Importance of the Spasm Provocation Test in Diagnosing and Clarifying the Activity of Vasospastic Angina

Background: Some patients with Intractable Vasospastic Angina (i-VSA) have angina attacks, irrespective of vasodilator treatment. Despite the significance of the prediction of i-VSA in the clinical setting, the means to accomplish it remain unclear. Therefore, we investigated the relationship between i-VSA clinical parameters, including angiographic findings from the Spasm Provocation Test (SPT), and i-VSA to predict factors responsible for i-VSA. Methods: We examined 155 patients (98 males and 57 females; mean age, 66 years) with VSA diagnosed using the SPT. We focused on the following two findings in the SPT: the positive SPT by a low dose of acetylcholine (L-ACh; 30 μg for the right coronary artery and 50 μg for the left coronary artery) and the total occlusion (TOC) due to coronary spasm. i-VSA was defined as uncontrollable angina even after the administration of two types of coronary vasodilators. Results: There were 38 patients with i-VSA (25%). Positive L-ACh and TOC were more frequently observed in the i-VSA group (L-ACh, 78% vs. 19% in treatable VSA; TOC, 33% vs. 6% in treatable VSA; both p<0.0001). The logistic regression analysis demonstrated that L-ACh (odds ratio [OR] 26.54; p<0.0001) and TOC (OR, 8.36; p=0.0038) were significant predictors of i-VSA. Conclusions: These results suggested that the occurrence of L-ACh and/or TOC during the SPT are predictive markers for i-VSA. The SPT may not only establish a diagnosis of VSA but also provide prognostic information in such patients.