Atrial fibrillation

Atrial fibrillation = incomplete atrial contraction → blood stasis and thrombus formation → clot to brain and ischemic stroke (5-fold ↑ stroke risk)
Risk factors: age, HTN, heart failure, cardiomyopathies - structural heart disease promotes remodeling that can lead to foci for AF

Definitions

Paroxysmal AF: self-terminating AF (< 7 d, usually < 48 hr)

Risk of complications does not change whether AF is paroxysmal or sustained!
Episodes lasting > 48 hrs unlikely to spontaneously terminate; should be anticoagulated
Most will progress to persistent AF over time

Persistent AF: episode > 7 d, or required cardioversion (with drugs or electrical)
Long-standing persistent AF: > 1 yr - should pursue rhythm control
Permanent (accepted) AF: > 1 yr - rhythm control methods no longer pursued/unsuccessful

Symptoms - palpitations, SOB

May be asymptomatic about 1/3 of the time ("silent" AF)

Exam

Irregularly irregular HR (but EKG necessary for diagnosis)
May have s/sx of heart failure - decreased breath sounds, crackles, lower leg swelling/pitting edema

EKG findings

No P waves; irregularly irregular rhythm
Afib with RVR (rapid ventricular response) - rate > 100 bpm; typically 110-160 bpm

Other workup

Echo - may show dilated left atrium if long history of AF
TSH - hyperthyroid may cause AF
Post-operative risk factors/management:

Hypoxia
Pain (sympathetic response)
Fluid balance (hypovolemia leads to poor perfusion of myocardium; hypervolemia stretches the atria)
↓K, ↓Mg

Goal of therapy

Anticoagulation - reduce risk of ischemic stroke. Only antithrombotics reduce AF-related death
Rate and rhythm control - manage symptoms; reduce risk of tachycardia-induced cardiomyopathy

Rate control can be through medications (below) or electrical cardioversion if hemodynamically unstable
Long-term management of AF may try rhythm control - antiarrhythmic drugs, cardioversion, or radiofrequency catheter ablation

Treat co-existing heart disease

Rate control

AF with RVR (rapid ventricular response HR > 100) should be rate controlled to avoid symptoms/hemodynamic instability
Long-term rate control should aim for resting HR < ~ 100 (no additional benefit with strict rate control < 80), or until asymptomatic

	Dose (IV acute)	Dose (PO maintenance)	Notes
Metoprolol (β-blocker)	5 mg (tartrate) over 2 min Can repeat q5 min x 3	25-100 mg (succinate/XL) BID/TID	Preferred if CAD (bronchospasm bad for COPD)
Diltiazem (non-DHP CCB)	0.25 mg/kg IV over 2 min (~12.5 - 25 mg) Can repeat after 5 min, or start drip of 5-15 mg/hr	120-360 mg (ER) QD, divided	Preferred if COPD (negative inotrope bad for HF)
Digoxin	0.25 mg q2h, up to 1.5 mg	0.125-0.375 qd (renal dosing)	Consider in HF or low BP (βB/CCB lower BP; digoxin is +inotrope) (beware in renal failure/electrolyte imbalance, can be pro-arrhythmic)
Amiodarone	150 mg bolus over 10 min x 1-2, then 1 mg/min x 6 hrs, 0.5 mg/min x 18 hrs, then convert to PO		Consider in critically ill pts that cannot tolerate lower blood pressures (e.g. on pressors) Can cardiovert - caution if risk of thrombus (afib > 48 hrs; TEE first to look for clot)

Rhythm control (cardioversion)

When to pursue

Rate control fails to relieve symptoms
Existing heart failure - rhythm control improves cardiac performance

When not to pursue

Asymptomatic new onset AF, esp. if elderly (may not tolerate drugs/electrical cardioversion). New onset AF typically spontaneously cardioverts in < 24 hrs

Duration of AF, anticoagulation, and cardioversion

1st episode of AF - rate control; patients may spontaneously cardiovert
Episode < 48 hrs - may cardiovert on heparin w/o risk for stroke
Episode > 48 hrs - cardioversion may dislodge an existing thrombus → stroke

Should perform TEE to r/o atrial thrombus, then cardiovert on heparin if no thrombus

TTE cannot rule out a thrombus in the left atrium

Otherwise must anticoagulate for ~ 3 weeks before cardioversion, and continue for 4 wks after

If still see a thrombus, may opt to rate control instead of rhythm control

If stroke risk factors (see CHA₂DS₂VASC score) - continue lifelong anticoagulation

Pharmacologic - flecainide, amiodarone - need more info here
Direct current cardioversion - use if hemodynamically unstable; requires sedation/anesthesia
Other treatments (if refractory to rx)

Radiofrequency catheter ablation
Watchman device - close off the left atrial appendage, which is the main site for thrombus formation
AV node ablation - leads to complete heart block and pacemaker dependence

Anticoagulation

Balance stroke risk (CHA₂DS₂-VASc) vs. hemorrhage risk (HAS-BLED)

Risk stratification for ischemic stroke in AF (paroxysmal AF has same stroke risk as persistent AF)

Schemes: CHADS₂ vs CHA₂DS₂-VASc (stroke risk factors)

Include data on one vs. another, etc.

Anticoagulation generally reduces stroke risk by 1/3
Score = 0: don't anticoagulate
Score = 1: consider antiplatelet/anticoagulation
Score ≥ 2: anticoagulation candidate

	CHADS₂	CHA₂DS₂-VASc
CHF	1	1
HTN	1	1
Age >75	1	2
DM	1	1
CVA/TIA/TE	2	2
Vascular disease (e.g. MI, PAD)		1
Age 65-74		1
Female Sex		1
Max Score	6	9

Score	Adjusted Stroke Rate (%/year)
Score	CHADS₂	CHA₂DS₂-VASc
0	1.9	0
1	2.8	1.3
2	4.0	2.2
3	5.9	3.2
4	8.5	4.0
5	12.5	6.7
6	18.2	9.8
7		9.6
8		6.7
9		15.2

Risk benefit of anticoagulation in afib

HAS-BLED - risk of major bleeding with anticoagulation in afib at 1 year

**hide** Outperforms other scores like ATRIA, HEMORR₂HAGES

Major bleeding defined as: intracranial, hospitalization, hemoglobin decrease > 2 g/L, and/or transfusion
Score ≥ 3: high risk; caution with anticoagulation

HTN	1
Abnormal renal or liver function	1 pt each
Stroke	1
Bleeding tendency	1
Labile INR’s	1
Elderly (>65 yo)	1
Drugs (ASA/NSAIDs or EtOH abuse)	1 pt each
Max score	9

Score	Bleeds per 100 pt-years
0	1.13
1	1.02
3	3.74
4	8.7
5-9	Insufficient data

A flutter

Treat like a-fib
More difficult to rate control - may need to go to cardioversion earlier

author: admin | last edited: June 11, 2018, 5:21 p.m. | pk: 4 | unpublished