The investigators intend to study how baseline arterial compliance (as defined by stroke volume/pulse pressure) influences the clinical success of intraaortic balloon counterpulsation (IABC) in patients with cardiogenic shock (CS). The investigators aim to compare clinical outcomes in CS patients requiring IABC with normal compliance versus low compliance. The study will enroll patients undergoing IABC that are clinically indicated. Baseline hemodynamic measurements will be obtained and then patients would be stratified based on their compliance. Post IABC, serial hemodynamic measurements will be obtained and compared between groups. Patients will continue to be followed longitudinally until the IABC has been discontinued for any reason. The proposed study will yield results that will aid in developing a larger clinical trial and ultimately assist clinicians in determining if IABC is appropriate therapy for patients in cardiogenic shock.