Definition:
In this study NOAF was defined as episodes of paroxysmal or persistent AF occurred during ICU stay with no previous diagnosis of AF. All patients were attached to continuous cardiac monitor and episodes were confirmed on 12 lead electrocardiography. Chronic kidney disease was classified in stages by eGFR according to the KDIGO (Kidney Disease: Improving Global Outcomes) clinical practice guidelines. Acute kidney injury was also classed according to the KDIGO clinical practice guidelines.
Acute cardiac injury was diagnosed if serum levels of cardiac biomarker (Troponin T) were above the 99th percentile of the upper reference range and if new abnormalities were shown in echocardiography or electrocardiogram. Patients with heart failure with reduced ejection fraction (HFrEF) as per ESC guidelines (left ventricular ejection fraction less than 40%) were classed under chronic heart failure. The linear dimension (anteroposterior measurement on parasternal long axis view) was taken into consideration for measuring left atrial (LA) size and was categorised according to the reference values from British Society of Echocardiography. Extra corporeal membrane oxygenation (ECMO) was offered to patients with acute severe and potentially reversible respiratory failure despite ventilator support who fulfilled the NHS England ECMO guidelines (version 1- revised in response to the COVID-19 pandemic). All documented diagnoses of pulmonary embolism (PE) were confirmed radiologically following computed tomography pulmonary angiogram (CTPA). The highest value of the laboratory markers prior to the AF episode were taken into account for the purpose of analysis in table 2.