To investigate the superior vena cava collapsibility index (SVC-CI), measured via transesophageal echocardiography (TEE), as a marker of fluid responsiveness. Two groups will be compared in this study. Groups will be identified by obtaining cardiac output (CO) by standard means using the TEE or pulmonary arterial catheter (PAC). Both of these monitors are considered standard for patient's undergoing coronary artery bypass grafting surgery (CABG) and recording initial CO readings. Based on CO, the patient's will be placed in study groups one or two. Participants with normal and mildly reduced left ventricular ejection fraction (LVEF >40%) for group one and those with moderately to severely reduced LVEF (<40%) in the second group.

Following group separation, we will measure the SVC-CI and CO metric in both groups. The intervention will be an operating room table tilt test (head up and then head down) to artificially simulate giving the patient additional fluid. Before and after table tilt, the SVC-CI and CO will be obtained and measured. The SVC-CI is a mathematical equation determined by distance measurements taken via TEE to identify how much the superior vena cava has collapsed following table tilt. Participants will be considered responders if the CO increases by 12% following intervention. Non responders less than 12% change in CO following intervention. Our hypothesis is that the SVC-CI can differentiate responders vs non-responders with regards to fluid responsiveness with adequate sensitivity and specificity in participants with CAD undergoing isolated CABG. The SVC-CI numerical values for the two groups, responders and non-responders, will calculate a threshold of sensitivity and specificity percentages for future patients undergoing CABG.

Inclusion Criteria:

1. Age ≥ 18
2. Participants with CAD undergoing CABG utilizing cardiopulmonary bypass
3. Participants who are able to consent for themselves
4. Primary language is English

Exclusion Criteria:

1. Age less than 18 years of age
2. Participants with CAD undergoing off-pump coronary artery bypass (OP-CAB)
3. Severe cardiac valvular pathologies or active congestive heart failure
4. Participants in active arrhythmia such as atrial fibrillation and atrial flutter at the time of data collection.
5. Participants who are unable to consent for themselves
6. Primary language is something other than English

Participants with CAD undergoing CABG utilizing cardiopulmonary bypass

It will depend if the data is shared in data bases and what kind of data bases. this has not been determined.