In patients with chest pain and/or shortness of breath coronary artery disease (CAD) is suspected depending on the pattern of symptoms and the electrocardiogram (ECG). Coronary angiography is the method of choice to verify this suspicion. If the patient coronary arteries on coronary angiography are totally normal or unobstructed, one can only speculate if the patients' discomfort is from the heart or not. A possibility to get further information about the healthiness of the coronary arteries is the acetylcholine test (ACH-test). When injecting this natural, body produced-substance into the coronary arteries one can test if the vessels develop coronary spasm which can be the reason for the patient's symptoms. The investigators therefore use this test in this study to look for coronary spasm in patients with suspected CAD but normal/unobstructed coronary arteries. In case of a positive test, the patient profits from having found a cause for his/her symptoms making treatment with special tablets possible. Furthermore, the investigators want to analyze blood samples of every patient to look for signs of inflammation, vasoconstriction and genetic variants that seem to be linked with coronary spasms. On the basis of these results the ACH-test could probably be avoided in the future.

Inclusion Criteria:

• Adults between 35 and 95 years old with angina pectoris and/or dyspnea suggestive of coronary artery disease with non-invasive proof of coronary ischemia or high pre-test probability for CAD who will be referred for coronary angiography
• Serum creatinine < 1,4 md/dl
• Left ventricular ejection fraction > 50%

Exclusion Criteria:

• Patients under 35 years and above 95 years of age
• Severe chronic obstructive pulmonary disease (contraindication for acetylcholine-testing)