With regard to the characteristics of spasm segment, had been clearly described by other invasive imaging methods including intravascular ultrasound and optical coherence tomography. However, there is potential risk during these invasive procedures, such as severe myocardial ischemia or fatal arrhythmia.

Presently available imaging test for coronary artery disease in multi detector-row computed tomography angiography (MDCTA) evaluation has high diagnostic accuracy to evaluate coronary artery stenosis. However, previous report assessing imaging findings or diagnostic accuracy of MDCTA in patients with vasospastic angina (VSA) is lacking.

Previously investigators analyzed the characteristics of coronary spasm segment in an observational individual dataset, suspected VSA patients (n=20) underwent dual-acquisition of MDCTA (initial and intravenous nitrate injected CT imaging), the diagnostic accuracy showed sensitivity: 73%, specificity: 100%, positive predictive value: 100%, and negative predictive value: 56%.

Further study is necessary because previous analysis presented limited sample size and deficiency of healthy control.

Therefore, investigators hypothesis that dual-acquisition of MDCTA in noninvasive tool for coronary assessment provide more information of coronary characteristics, and the diagnostic efficacy would be non-inferior as compared with the invasive coronary imaging modality in coronary spasm-induced angina attacks.

Inclusion Criteria:

• Subject is onset of angina-like attack at rest, during effort, or during rest and effort.
• Subject has chest pain between night and early morning.
• Subject is scheduled to undergo MDCTA.
• Subject is an acceptable candidate for CAG with an EG provocation test.
• Cardiac condition: BP>90/60mmHg, ECG: sinus rhythm with regular, left ventricular ejection fraction>55%, and resting heart rate<100 beats/min.
• Subject will be provided written informed consent.
• Subject is willing to comply with study follow-up requirement.

Exclusion Criteria:

• Subject has clinical evidence of acute coronary syndrome.
• Subject has evidence of significant narrowing (>50% stenosis by CAG).
• Subject has clinical evidence of cardiomyopathy or valvular heart disease.
• Subject is hemodynamically unstable.
• Subject has a history of PCI and CABG.
• Subject is pregnant and/or breastfeeding or intends to become pregnant during the duration of the study.
• Subject has known allergy to contrast medium.
• Subject has renal insufficiency (serum creatine >2.5 mg/dl).