Patients Study protocol was approved by the National Ethics Committee of Slovenia, informed consent was obtained from all patients or their relatives. Study was performed during October 2004 and January 2006. After initial hemodynamic resuscitation, transthoracic ultrasound heart examination was performed in all patients admitted to our ICU. In patients with primary heart disease, low cardiac output, and no signs of hypovolemia, a right heart catheterization with a pulmonary artery floating catheter (PAFC)(Swan-Ganz CCOmboV CCO/SvO2/CEDV, Edwars Life Sciences, USA) was performed after decision of treating physician. The site of insertion was confirmed by the transducer waveform, the length of catheter insertion and chest radiography. In all patients systemic arterial pressure was measured invasively using radial or femoral arterial catheterization. Patients with inserted PAFC and signs of low flow state (cardiac index less then 3.0 L/min/m2) were included in our study. PAFC data were calculating using standard formula.