Core Content: The Irregular Irregularities of Atrial Fibrillation
Incidence
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
Physiology
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
Treatment
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
More FOAM
Pulmcrit episode: https://emcrit.org/squirt/af/
PCCM - Atrial Fib for the Intensivist: https://pulmccm.org/review-articles/atrial-fibrillation-for-the-intensivist-part-2/
CHEST 2018 review: https://journal.chestnet.org/article/S0012-3692(18)30545-2/fulltext
HD stable new onset Afib: https://emcrit.org/pulmcrit/treatment-of-hemodynamically-stable-new-onset-af-in-critical-illness/
NAFCI (new onset AF in Critically ill) is associated with 2% risk of ischemic stroke among patients with severe sepsis : https://www.ncbi.nlm.nih.gov/pubmed/22081378
Risk of Hemorrhage in ICU patients: https://www.sciencedirect.com/science/article/pii/S1875213615000091?via%3Dihub
Attributions
Coming soon
