Question 2

College Answer

Management of atrial fibrillation requires consideration of urgency of treatment, reversal of potentially reversible causes, rate control, rhythm control and risks of thromboembolism. In the acute setting either rate control or reversion to sinus rhythm may provide haemodynamic benefits. Reversion to sinus rhythm is reasonable if atrial thrombi not expected (AF or more than 48 hrs duration or unknown duration). The use of trans-oesophageal echocardiography in excluding atrial thrombi is still uncertain (as not all thrombi identified). If reversion would add risks of thromboembolism then rate control and anticoagulation is preferred. In the presence of haemodynamic instability synchronised cardioversion (before or after administration of drugs/electrolytes) should be considered. If reversion is desired, correction of electrolytes (K and Mg) and specific drugs may be successful (eg. one of amiodarone [especially if impaired LV function], flecainide, procainamide, ibutilide or propafenone). If rate control only is desired then calcium channel blockers, beta-blockers or digoxin can be considered. Many critically ill patients are resistant to rate control with digoxin. Beta- blockers, calcium channel blockers and digoxin can be harmful if the rapid AF is due to Wolff-Parkinson-White syndrome.
Specific reversible causes may include drugs (eg. beta-agonists), mechanical stimuli (eg. guidewire, or catheters) and systemic disorders (eg. thyrotoxicosis, sepsis). Published guidelines (ILCOR, AHA) are available.

Discussion

The question calls for a systematic approach.

Such an approach can be reviewed in the ILCOR guidelines, from which the local ARC guidelines are derived.

A fresh recently published article presents a lovely table of causes of AF in the ICU (Table 1) as well as a lucid and detailed discussion of the therapeutic options. My answer was largely modelled on these suggestions.

• Assess  the patient by history physical examination; establish the duration of AF and the likely cause for its onset (if possible)
• Stratify into hemodynamically stable or compromised category on the basis of changes in vital signs and tissue perfusion before and after the episode

Hemodynamically stable patient:

• Rate control with beta blockers, calcium channel blockers, digoxin or amiodarone
• Reverse any potentially reversible factors
• Consider DC or chemical cardoversion if AF is of recent onset
• Commence anticoagulation if AF is of uncertain onset, or longer than 48 hrs duration. The options are:
  • Warfarin: relative risk reduction for stroke 62%; absolute risk reduction 2.8% per year
  • Aspirin: relative risk reduction for stroke 22%; absolute risk reduction 1.5% per year
  • Warfarin plus aspirin: no additional benefit over warfarin alone
  • Dabigatran: 35% reduction in stroke compared to warfarin
• Consider TOE to rule out intracardiac thrombi
• Reverse any potentially reversible factors

Hemodynamically compromised patient

• Basic  life support as needed
• Synchronised DC cardioversion
• Hemodynamic and respiratory support as needed, including emchanical ventilation and inotropes/vasopressors
• Reverse any potentially reversible factors

Investigation of causes, reversal of reversible factors, and preventative strategies

• Investigate causes and institiute preventive corrections
  • Screen for sepsis
  • Correct electrolyte abnormalities
  • Correct hypothermia
  • Correct mechanical stimulus to the atria, eg. central lines
  • Corect atrial distension, eg. fluid overload
  • Address issues of pain and anxiety
  • Investigate for cardiac ischaemia
  • Investigate for endocrine abnormalities, eg. thyroid function and phaemochromocytoma

Morrison, Laurie J., et al. "Part 8: advanced life support 2010 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations." Circulation 122.16 suppl 2 (2010): S345-S421.

Arrigo, Mattia, Dominique Bettex, and Alain Rudiger. "Management of Atrial Fibrillation in Critically Ill Patients." Critical Care Research and Practice 2014 (2014).