Critical Care Atrial Fibrillation Evaluation (CAFE)

Background

The University of Oxford Critical Care Research Group worked in collaboration with ICNARC to investigate patients who developed atrial fibrillation (AF) during their stay in intensive care. The project looked into how best to treat this common problem.

AF is a heart problem causing a fast, irregular heartbeat. This reduces the heart’s ability to pump blood around the body. It also causes blood clots to form inside the heart. These can spread through the blood vessels to other parts of the body. These clots can cause strokes if they spread to the brain.

New-onset AF (NOAF) is a common problem in patients outside intensive care units (ICUs) and good, evidence-based, guidelines exist to help doctors treat people who develop this condition. Around 10% of people treated on an ICU develop atrial fibrillation as a complication of their severe underlying illness. This additional problem makes them more unstable, so they stay longer in the ICU and have worse outcomes. Atrial fibrillation therefore needs prompt and effective treatment to prevent further harm.

Treatments for atrial fibrillation that work in people outside the ICU may not work in people treated on an ICU who are already very ill before their heart changes rhythm. This means that guidelines for treating atrial fibrillation outside ICU are not helpful for patients treated on an ICU. There is uncertainty about what is the best treatment and practices differ between countries, and between different ICUs in the same country.

The CAFE study comprised:

1) A scoping review evaluating the evidence for the clinical effectiveness of pharmacological and non-pharmacological treatments for NOAF in patients admitted to an ICU. The review included quantitative studies such as randomized trials, cohort studies, case series, and trial protocols. The review found that the evidence base supporting NOAF treatment was limited. However, beta blockers or amiodarone appeared superior to CCBs as first line therapy in undifferentiated patients in ICU. The little evidence available did not support therapeutic anticoagulation for NOAF whilst patients are critically ill. We found that consensus definitions for NOAF, rate and rhythm control are needed. Most included studies concluded that further research was needed;

2) A multicentre retrospective cohort study investigating comparative effectiveness of common NOAF treatments. We included adult patients admitted to 3 ICUs in the UK and 5 ICUs in the USA who developed NAOF during their ICU stay. We analysed the haemodynamic changes associated with NOAF. We analysed rate control, rhythm control, and hospital mortality associated with common NOAF treatments. We balanced admission and post-NOAF, pre-treatment covariates across treatment groups.

We found that ICU-acquired NOAF was followed by decreases in blood pressure. Beta blockers and and amiodarone amiodarone were associated with similar cardiovascular control and appeared superior to digoxin and CCBs. Accounting for key confounders removed previously reported mortality benefits associated with beta blocker treatment; and

3) A retrospective cohort study investigating the longer-term outcomes associated with ICU-acquired NOAF. We included 4615 patients with NOAF and 27 690 matched controls admitted to 248 adult ICUs in England, from April 2009 to March 2016. We found that patients who developed NOAF during an ICU admission are at a higher risk of in-hospital death and readmissions to hospital with AF, heart failure, and stroke than those who did not.

Impact

 As a result of this work, the NIHR has funded a randomised trial of amiodarone versus beta blockers for the treatment of ICU-acquired NOAF (NIHR 21/504).

Publications from the CAFE study:

The CAFE Scoping Review

Comparative effectiveness of common treatments for new-onset atrial fibrillation within the ICU

New-onset atrial fibrillation in intensive care: epidemiology and outcomes

For more information about the CAFE study, please visit the ICNARC website.