Atrial Fibrillation in Critical Illness: The Irregular Irregularities

Written By Rachel F
Pulmcast podcast cover artwork for Atrial Fibrillation in Critical Illness episode
Pulmcast podcast hosts discussing atrial fibrillation management in the ICU

How Common Is AFib in Critically Ill Patients?

  • It can be as high as 78% in the critically ill population but its hard to nail down an exact number

  • Having new onset atrial fibrillation in critical illness increases your mortality risk from 22% to 44%. In surgical ICUs that’s a little worse. Mortality rates of 45% vs 16% without a fib.

    • Correlation??? afib is unlikely to cause the mortality increase but it is a marker of disease severity

Underlying Physiology and Triggers

  • Some processes are thought to prime the heart for afib

    • chronic processes like: metabolic syndrome, HTN, Mitral valve disease, and age

    • acute processes like inflammation and bacterial deposits in the endocardium

    • persistent tachycardia of any kind can prime the system for A fib

  • Then, an arrhythmogenic trigger occurs

    • Changes in atrial architecture (stretch, congenital/surgical lesion, myxoma)

    • Changes in membrane potentials (drugs, lytes, inflammation - myocarditis)

    • Increased sympathetic tone

  • Why AFib Matters in the ICU

    • Electrical chaos - 700 impulses/min (can’t get through) - leads to loss of coordinated atrial contraction

    • Blood pooling - esp left atrial appendage - stasis, incr risk of clot cardioembolic event (small microemboli or larger microemboli - consider when cardioverting)

    • Loss of atrial kick - 20 NBD routinely maybe, but shock states - 20% is KBD

    • Unlike sinus tach (increased chronotropy WITH a concomitant increase in dromotropy and lusitropy) rapid AF is irregular, uncoordinated, and can quickly reach non-physiologic rates

    • Cardiac output eq is CO x HR, but there is an upper limit to HR before you reduce SV from a reduction in filling time

Treatment Pathways: Rate vs Rhythm Control

  • 1) Is the patient stable or unstable?

    • Unstable (e.g. hemodynamics change)

      • Are the hemodynamics changing because of the critical illness or the afib itself?

      • Synchronized cardioversion

    • Stable

  • 2) Can you fix the underlying trigger of afib?

    • Can be difficult to determine

  • 3) Rate or rhythm control?

    • In the non-ICU population - rate control

    • otherwise, it’s the wild wild west

Algorithm from Pulmcrit

Hand-drawn infographic explaining atrial fibrillation incidence, physiology, and treatment in critically ill patients

Learning Resources and Further Reading

Rachel F

Rachel is a physician assistant who has been holding down the ICU since 2016. She joined the Pulmcast podcast in 2017 and has been hooked on FOAMed ever since. Rachel has a passion for teaching using technology with a special focus on preserving dignity in the ICU. When she's not at work, you’ll find her playing with her golden retriever, hunting for thrift store treasures, and soaking up time with her husband and son.

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