Severe sepsis and septic shock are causes of admission in intensive care units.Modification of natriuretic peptid including NT-proBNP and cardiac autonomic nervous system alteration are reported in sepsis shock and severe sepsis and seems to link to patient prognosis admitted to intensive care units.

Our principal aim is to characterize modulation of cardiac sympathic nervous system in sepsis through the study of sinusal change and myocardiac fixing of MIBG.

The second aim is 1)to assess links between alteration of cardiac sympathic nervous system and NT-PRoBNP variations in sepsis and 2)To know prognostic impact in sympathic nervous system compare to NTproBNP.

Inclusion Criteria:

• Patient over 18 years admitted in intensive care unit and having severe sepsis criteria or septic shock documented or suspected define as Bone Criteria
• hemodynamically stable situation
• sinusal rhythm
• Patient for social security

Exclusion Criteria:

• Minors
• Patient under guardianship or trusteeship
• pregnant or lactating women
• diabetic
• cardiomyopathy known and/or treated or detect in admission
• electro-systolic process permanent or transitory
• neurological history or degenerative pathology
• chronic respiratory insufficiency
• Chronic renal insufficiency

All patient transfer in intensive care unit with sepsis chock or severe sepsis define as Bone criteria.