**1. Introduction**

The term sepsis derives from ancient Greek "sêpsis" ("putrefaction" or "decay of organic matter") and was first used in a medical context in Homer's Iliad more than 2700 years ago. Currently, sepsis is defined as a life-threatening organ dysfunction due to a dysregulated host response to infection [1]. Since 2016, the updated operative definition of sepsis no longer considers the presence of systemic inflammatory response syndrome, but requires an infection plus organ dysfunction indicated by an acute change in Sequential Organ Failure Assessment (SOFA) [2] of at least two points (see **Table 1**). Septic shock is defined as sepsis plus circulatory failure with increased risk of death, indicated by hypotension requiring vasopressor therapy to maintain a mean arterial pressure (MAP) 65 mmHg or greater and a serum lactate of greater than 2 mmol/L despite adequate fluid resuscitation [3]. Other indices of tissue hypoperfusion (e.g. altered mental status, oliguria, delayed capillary refill) are acceptable alternatives whenever serum lactate determination is not available.

In high-income countries, sepsis represents approximately 6% of adult hospitalizations and 10–37% of intensive care unit (ICU) admissions. Mortality estimates from sepsis and septic shock vary widely, rounding 15% and 22% respectively [4]. In low-income regions, sepsis and septic shock predictably carry an even higher mortality, up to 50% [5].

Generally speaking, atrial fibrillation (AF) is the most frequently found cardiac arrhythmia in the ICU setting. Previously known AF is significantly prevalent among older patients with chronic conditions who are at risk for critical illness. New-onset AF (NOAF), on the other hand, is frequently triggered by accelerated


**Table 1.**

*Sequential organ failure assessment (SOFA) score [2].*

#### *Infections and Sepsis Development*

#### *Atrial Fibrillation during Septic Shock DOI: http://dx.doi.org/10.5772/intechopen.100317*

atrial remodeling and by concomitant stressors during critical illness, such as electrolyte imbalances and use of vasopressor drugs [6].

In this narrative review, the pathogenesis, risk factors, incidence, prognosis and management of AF in septic shock patients are summarized.
