Low Cardiac Output Syndrome occurs frequently after cardiac surgery, especially when pre-operative LVEF is altered (LVEF≤45%). The correction of hemodynamic failure requires adapted treatments: fluid expansion and/or inotropic or vasoactive drugs. Predictive indices of a response to fluid challenge may allow an earlier hemodynamic optimization, which has not been showed until now when LVEF is altered.

Inclusion Criteria:

• patients >18 years old in the immediate post-operative period after cardiac surgery
• ASA 1 - 3
• Pre-operative LVEF≤45%
• Sedated with Ramsay score: 6
• Mechanically ventilated with tidal volume at 8ml/kg, PEEP at 0mmHg, I/Eat 0,5
• With hemodynamic failure: SAP≤90mmHg and/or inotropic or vasoactive drug started in the operating room and/or clinical sign of shock and/or CI ≤2,3l/min/m2
• Affiliation to Health Insurance
• Consent form signed

Exclusion Criteria:

• Cardiac arrhythmia: frequent atrial or ventricular extra systoles, atrial fibrillation
• Intracardiac shunt
• Weight less than 50 kg
• History of central nervous system illness
• Pulmonary oedema (clinical and/or radiological and/or wedge pressure>18mmHg)
• Right ventricular failure suspected (CVP> wedge pressure) or diagnosed (trans thoracic and/or transesophageal echocardiography)
• Acute kidney injury with oligoanuria
• Severe post operative bleeding (chest tubes volume of >200ml/h for 3 hours or more)
• Severe hypoxia (PaO2/FIO2< 100)
• Administrative control (patient under guardianship or curatorship)