Microvolt T-Wave Alternans (MTWA) is a relatively new non-invasive method for identifying patients at increased risk of sudden death from ventricular arrhythmias. MTWA can be measured during a routine exercise test, during pharmacologic stress or during cardiac pacing. Its clinical performance compares favorably with that of other non-invasive risk stratifiers and invasive electophysiologic studies. The purpose of the present study is to define the reproducibility of MTWA testing.

The study will be performed in the Cardiac Rehabilitation Center at Assaf Harofeh Medical Center. Patients with coronary artery disease will be eligible to enroll.

Patient will undergo an exercise test on a stationary bicycle. TWA will be measured at heart rate of 105 and 115 BPM. The test will be repeated one week later in the same fashion. The patient will continue follow-up in the rehabilitation center as dictated by the rehabilitation program. Patients will be kept on their regular medications and there will be no change of the medications from the first TWA measurement to the second.

Inclusion Criteria:

1. Patients enrolled in the cardiac rehabilitation center program
2. Patients with CAD
3. Age >18 and < 80 YO
4. Patients with a pacemaker or defibrillator with normal AV conduction

Exclusion Criteria:

1. Patients with chronic AF
2. Patients with multiple APB's or PVC's
3. Patients who are unable to increase their heart rate to 115 BPM and don't have a pacemaker.
4. Patients who are unable to exercise on a bicycle.

Patients with coronary artery disease enrolled in a cardiac rehabilitation program.