Near Infrared Spectroscopy (NIRS) monitoring has proven beneficial in increasing safety and improving patient care during pediatric cardiac surgery and during Pediatric Intensive Care Unit (PICU) stays. NIRS estimates the amount of oxygen in tissues by comparing the tissue's absorption of two wavelengths of light corresponding to hemoglobin carrying oxygen and hemoglobin without oxygen.

During cardiac surgery, multi-site NIRS monitoring is used to determine the heart's output by comparing the amount of oxygen available to discrete regions of the body nourished by different parts of the circulatory system. NIRS leads placed on the forehead detect oxygen available to the brain (cerebral), while leads placed over the kidney reflect oxygen available to the internal organs (somatic).

NIRS monitoring has been used for studying muscle oxygen usage during exercise in normal and disease states. Cerebral oxygenation at peak exercise at has been studied with NIRS monitoring. The use of multi-site NIRS monitoring during exercise stress testing for studying cardiac output through the patterning of somatic and cerebral oxygenation in combination with exercise stress test data has not been researched.

We hypothesize that addition of multi-site NIRS monitoring to the standard data collection already achieved during exercise testing, will enable calculation of anaerobic threshold and cardiac output prediction. This will assist in determining appropriate timing for surgical intervention, predicting the post operative course and testing response to medication.

Inclusion Criteria:

• Children and adolescents from age 6 to 20 undergoing exercise stress testing on treadmill

Exclusion Criteria:

• Children and adolescents unable to exercise or unable to follow directions or unable to understand English.

Children and adolescents from age 6 to 20 undergoing exercise stress testing