Clopidogrel Response Assay 5 µl ADP and 0.2 ml blood will be added into a micro tube (2 ml) (final ADP concentration 1.25 µM). The tube will be rotated on the tube mixer at 10 rpm for 1 minute. 130 µl will be placed in a well and tested with the cone and platelet analyzer. (Varon D et al 1997) Arterial stiffness Assessment of arterial stiffness will be performed by a noninvasive technique using the commercially available SphygmoCor System (AtCor Medical LTD, Australia). All measurements will be performed while the patient is in a recumbent position at a room temperature of 25۫ C, between 06:30 and 08:30 A.M. after an overnight fasti (8-10 hours) and after a short period of rest. Peripheral pressure waveforms will be recorded from the radial artery at the wrist, using applanation tonometry with a high fidelity micromanometer. When sequential waveforms will be recorded, a validated 16-18 generalized transfer function will be applied to generate the corresponding central pressure waveform. The integral system software will be used to calculate an average radial artery waveform and to derive a corresponding central aortic pressure waveform using a previously validated generalized transfer function. From these data the indexes of arterial stiffness will be obtained. The augmentation of central arterial pressure is the difference between the first and second systolic peaks of the central pressure waveforms, and the central augmentation index (AIx) is the augmentation expressed as a percentage of the pulse pressure.