Visit 1 (initial examination): First of all the patient will be informed about the study. If the patient consents to participate, a short clinical history and physical examination will be carried out. Then the criteria of inclusion and exclusion will be checked. The blood pressure, pulse rate and body mass index will be determined. Subsequently the patient will be asked about previous diseases, with specific questioning about the occurrence of diabetes mellitus, coronary heart disease, stroke (including transitory ischaemic attacks [TIA] and prolonged reversible ischaemic neurological deficit [PRIND]) and peripheral arterial occlusive disease. The patient will be enrolled in the study if he/she fulfils the inclusion criteria and there are no exclusion criteria. Should the patient be taking a calcium channel blocker at the time of enrolment in the study, this will be withdrawn insofar as the attending physician considers that this is possible. Other existing medication will be retained. The interval between Visit 1 and Visit 2 is one week.