Red cell distribution width variations are increased in a variety of medical conditions such as congestive heart failure, acute myocardial infarction, pulmonary embolism, pneumonia, critical illness, and cardiac arrest , and is a predictor of mortality in the general population..

This study was done retrospectively on sepsis patients admitted to intensive care units. data will be retrieved from patient medical records. The primay end point will be occurrence of new-onset AF during ICU stay. The secondary outcomes will be 28-day mortality.

The presence of anisocytosis or RDW variations has been classicaly used as a test for iron deficiency anemia. Increasing evidence points to its potential as a predictor for various conditions such as heart failure , malignancy, ischemic heart disease and sepsis.

Study investigators will examine the relationship between RDW levels and incidence of atrial fibrillation in critically ill sepsis patients as well as 28-day mortality.

Inclusion Criteria:

• For all patients According to Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) , adult patients with suspected infection are identified, having quickSOFA (qSOFA) score meeting ≥2 of the following criteria: respiratory rate of 22/min or greater, altered mentation, or systolic blood pressure of 100 mmHg or less
• Sepsis patients with newly developed Atrial fibrillation during ICU stay.

Exclusion Criteria:

All patients with concomitant valvular disease, cardiomyopathy, cardiac dysrhythmias, previous cardiac surgery, secondary hypertension, hyperthyroidism, severe head injury, stroke, coma, acute coronary artery disease or underlying cardiac dysfunction[cardiac index (CI) <2.2 l/min/m 2 ], severe liver disease (Child-Pugh grade C), chronic renal failure were excluded from the study. In addition, pregnant patients were excluded.

70 patients of both sexes were enrolled in this study. They were admitted to the general ICU of Ain Shams University Hospitals with sepsis or septic shock