Core Content: The Irregular Irregularities of Atrial Fibrillation



  • 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


  • 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 is it more serious than sinus tach?

    • 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


  • 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



Coming soon

Rachel MulderComment