Pocket Medicine

CARDIOLOGY

ATRIAL FIBRILLATION

Classification (Circ 2006;114:e257 & 2011;123:104)

•  Paroxysmal (self-terminating, usually <48 h) vs. persistent (sustained >7 d or terminated after Rx) vs. permanent (typically >1 y and when cardioversion has failed or is foregone)

•  Valvular (rheumatic MV disease, prosthetic valve or valve repair) vs. nonvalvular

•  Lone AF = age <60 y and w/o clinical or echo evidence of cardiac disease (including HTN)

Epidemiology and etiologies (Annals 2008;149:ITC5-2)

•  1–2% of pop. has AF (8% of elderly); lifetime risk 25%; mean age at presentation ~75 y

•  Acute (up to 50% w/o identifiable cause)

Cardiac: HF, myo/pericarditis, ischemia/MI, hypertensive crisis, cardiac surgery

Pulmonary: acute pulmonary disease or hypoxia (eg, COPD flare, PNA), PE, OSA

Metabolic: high catecholamine states (stress, infection, postop, pheo), thyrotoxicosis

Drugs: alcohol (“holiday heart”), cocaine, amphetamines, theophylline, caffeine

Neurogenic: subarachnoid hemorrhage, ischemic stroke

•  Chronic: ↑ age, HTN, ischemia, valve dis. (MV, TV, AoV), CMP, hyperthyroidism, obesity

Evaluation

•  H&P, ECG, CXR, TTE (LA size, thrombus, valves, LV fxn, pericardium), K, Mg, FOBT before anticoag, TFTs; r/o MI not necessary unless other ischemic sx

Figure 1-5 Approach to acute AF

(Adapted from NEJM 2004;351:2408; JACC 2006;48:e149)

Strategies for recurrent AF (Circ 2011;123:104; Lancet 2012;379:648)

•  Rate control: goal HR <110 at rest if EF >40% and asx (NEJM 2010;362:1363)

AV node ablation + PPM as a last resort (NEJM 2001;344:1043; 2002;346:2062)

•  Rhythm control: no clear survival benefit vs. rate cntl (NEJM 2002;347:1825 & 2008;358:2667)

Consider if sx w/ rate cntl, difficult to cntl rate, ? unable to anticoag, ? benefit in CRT

Cardioversion

•  Consider pharm or electrical cardioversion w/ 1st AF episode or if sx;
if AF >48 h, 2–5% risk stroke w/ cardioversion (pharmacologic or electric) ∴ either TEE to r/o thrombus or ensure therapeutic anticoagulation for ≥3 wk prior

•  Likelihood of success ∝ AF duration & atrial size; control precip. (eg, vol status, thyroid)

•  Consider pre-Rx w/ antiarrhythmic drugs (esp. if 1st cardioversion attempt fails)

•  For pharmacologic cardioversion, class III and IC drugs have best proven efficacy

•  If SR returns (spont. or w/ Rx), atria may be mech. stunned; also, high risk of recurrent AF over next 3 mo. ∴ Anticoag postcardioversion ≥4–12 wk (? unless <48 h and low risk).

Nonpharmacologic therapy

•  Radiofrequency ablation (circumferential pulm. vein isolation; Lancet 2012;380:1509): ~80% success; reasonable alternative to AAD in sx persistent or paroxysmal AF w/o ↑↑ LA or ↓ EF (NEJM 2012;367:1587; RAAFT 2, HRS 2012)

•  Surgical “maze” procedure (70–95% success rate) option if undergoing cardiac surgery

•  LA appendage closure/resection: reasonable if another indication for cardiac surgery

percutaneous closure noninferior to warfarin, ↓ risk of ICH, but w/ procedural complic; additional studies & approaches underway (Lancet 2009;374:534; PREVAIL, ACC 2013)

Oral anticoagulation (Chest 2012;141:e531S; EHJ 2012;33:2719; Circ 2013;127:1916)

•  All valvular AF as stroke risk very high

•  Nonvalvular AF: stroke risk ~4.5%/y; anticoag → 68% ↓ stroke; use a risk score to guide Rx:

CHADS2: CHF (1 point), HTN (1), Age ≥75 y (1), DM (1), prior Stroke/TIA (2)

CHA2DS2-VASc: adds 65–74 y (1), >75 y (2); vasc dis. (1);  sex (1)

score >2 → anticoag; score 1 → consider anticoag or ASA (? latter reasonable if risk factor 65–74 y, vasc dis. or ); antithrombotic Rx even if rhythm cntl

•  Rx optionsfactor Xa or direct thrombin inhib (non-valv only; no monitoring required) or warfarin (INR 2–3; w/ UFH bridge if high risk of stroke); if Pt refuses anticoag, consider

ASA + clopi or, even less effective, ASA alone (NEJM 2009;360:2066)