There are many patients hospitalized for chest pain, which don't have high risk features that require invasive coronary angiography, but are considered intermediate risk and for which ischemic heart disease can not be excluded.

The current management for these patients is to perform a non invasive test in order to classify their risk.

Exercise ergometry is a commonly used non invasive test to detect ischemia. that test is non-invasive, and does not involve radiation or intra-venous contrast. The test is limited for many patients, because of un-ability to exercise, or because of non-interpetable Electro Cardio-Graphy (ECG).

Heart rate variability is well known to be a marker of ischemic heart disease. Heart rate variability testing is a non-invasive ECG monitoring technique.

The study design is to identify hospitalized patients who are candidates for non-invasive stress testing, and to monitor their heart rate variability for one hour prior to the stress test.

Ischemic heart disease is among the leading causes of death and disability in the modern world. Effective treatment for cardiac ischemia is based on identification of the proper patients and assigning prompt treatment to those patients.

It is not simple identifying the proper patients. There are many patients complaining of typical anginal chest pain without coronary heart disease, and there are many patients with active angina who complain of non-typical symptoms or who don't feel any symptoms.

Management of hospitalized patients with suspected angina pectoris is based on their complaints, their risk factors and laboratory results (ECG, troponin). They are classified into low-risk, high risk and intermediate.

Intermediate risk patients usually require additional testing in the hospital in order to re-classify them into high or low risk.

Heart rate variability is a well-known marker of active cardiac ischemia. The investigators plan to perform a 60 minute heart rate variability monitoring.

Inclusion Criteria:

• Adult patients
• Hospitalized for Chest pain
• Intermediate probability for ischemic heart disease
• Selected management strategy is non invasive cardiac stress testing

Exclusion Criteria:

• Active Ischemic symptoms
• ECG changes suggestive of myocardial ischemia
• Troponin elevation on blood tests
• Atrial flutter
• Multiple APB's or VPB's on resting ECG

Hospitalized patients with suspected ischemic heart disease requiring further evaluation.