Objective：

1. To evaluate the consistency of cardiac output measured by different hemodynamic monitoring methods in patients with VA-ECMO
2. To evaluate whether different hemodynamic monitoring methods can accurately detect the trend of cardiac output changes

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) has been used for profound cardiogenic shock to bridge to decision,ventricular assist devices,or transplant.Close monitoring of cardiac output, especially in patients before and after intervention (such as volume expansion, diuresis, vasoconstriction, vasodilation therapy), can help to adjust the treatment strategy. Hemodynamic monitoring in ECMO patients requires familiarity with the underlying pathophysiology and circulatory mechanics of extracorporeal flow.Limited to the actual clinical situation of patients, one or two hemodynamic monitoring methods may be accepted. Is there consistency between different hemodynamic monitoring results? And whether hemodynamic monitoring can accurately detect the changes of these parameters before and after intervention is an important issue in clinical practice. This study will provide important reference for VA-ECMO patients how to choose appropriate hemodynamic monitoring tools and how to interpret the results of hemodynamic monitoring.

Inclusion Criteria:

1. cardiac surgery
2. treatment with VA-ECMO
3. mechanical ventilation
4. hemodynamic monitoring according to patient's condition (PAC, Flotrac, echocardiography)

Exclusion Criteria:

1. age < 18
2. cardiac arrhythmia
3. moderate to severe aortic, mitral and tricuspid regurgitation
4. active hemorrhage
5. IABP
6. spontaneous triggering of the ventilator