Safety and Efficacy of the Gastric Reactance (XL) in Patients Post-operated of Elective Cardiac Surgery

Inclusion Criteria: * Women and men within an age equal or greater than 18 years old. * Subjects scheduled to an elective cardiac surgery for valvular surgery, revascularization or a combination of both. * Subjects compliant with the indication to be placed a floating pulmonary artery catheter. * Marks results previous to surgery: STS mortality risk equal or greater than 6% of the day before or Euro Score II with a mortality risk equal or greater than 6% or left ventricle ejection fraction (LVEF/FEVI) less than 45% (patients with cardiac failure or right ventricle dysfunction or a combination of both), tricuspid annular plane systolic excursion (TAPSE) less than 17 mm, peak systolic velocity of tricuspid lateral ring measured by Tissue Doppler (LVOT/TSVI) less than 0.1 m/s; patient with elective surgery of: aortic and mitral valve replacement or aortic and mitral valve replacement + tricuspid valve plasty or aortic valve replacement + mitral valve plasty or mitral valve replacement + tricuspid valve plasty or aortic, mitral and tricuspid valve replacement or aortic valve replacement + tricuspid valve plasty or double valve replacement (any combination) + revascularization or aortic valve replacement + revascularization + mitral valve plasty. * Subject is not enrolled in another investigational protocol. * Informed consent has been signed of acceptance by the subject before study procedures. * Subject in sinus rhythm before surgery. Exclusion Criteria: * Subjects with records of recent digestive tube bleeding (last 30 days). * Paraplegic or hemiplegic subjects. * Subjects with congenital background (interauricular communication, ventricular atrial channel, coarctation of the aorta, persistent arterial duct, pulmonary stenosis, ventricular septal defect, tetralogy of fallot, total or partial anomalous pulmonary venous drainage, transposition of the great vessels, tricuspid atresia, arterial trunk, etc). * Maxillofacial malformation. * Catheter placement failure. * Known pregnancy or discovered pregnancy after admission (before surgery). * Woman in breastfeeding period. * Subjects not compliant with clinical indication of nasogastric catheter placement or contraindicated to place a nasogastric catheter. * Subjects with an implanted pacemaker or permanent defibrillator. * Medication supply that impedes contact between Florence catheter and the gastric mucosa (barrier effect) like sucralfate, aluminum hydroxide, bismuth subsalicylate, magaldrate, etc.