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Drug Starting Dosage Maximum Dosage Comments
Metoprolol IV: load 5 mg over 1 min, repeat twice at 5-min intervals
PO: 450 mg/day. Metabolized by liver; available in once-a-day
extended-release formulation (metoprolol succinate). PO: start 50 mg bid
Atenolol IV: 5 mg over 5 min, repeat after 10 min
PO: 200 mg/day. Excreted by kidney.
PO: start 50 mg qd Propranolol IV: 1–3 mg at 1 mg/min;
can repeat after 2 min, then every 4 hr
PO: 640 mg/day. Metabolized by liver; available in once-a-day extended-release formulation (Inderal LA). PO: start 10 mg tid or qid
Calcium channel blockers Do not attempt in patients with Wolff-Parkinson-White
syndrome. Verapamil IV: 2.5–10 mg over 2 min;
can repeat 5–10 mg after 15–30 min
IV: 20 mg. Dosage adjustment needed for renal and hepatic insufficiency; consider starting bowel regimen; several once-a-day preparations available.
PO: 480 mg/day. PO: 80–120 mg tid or qid PO: 360 mg. Diltiazem IV: 20 mg over 2 min
bolus, 5–15 mg/hr drip for 24 hr
Hepatic metabolism and excretion; several once-a-day preparations available.
PO: start 30 mg qid Others
Digoxin IV: 0.5–1 mg, 50% initially, then 25% 6 to 12 hr later twice
Check levels and electrocardiogram.
Primary metabolism via kidney; avoid serum levels >2 ng/ml (stay at lower end of therapeutic range for women and older adults).
PO: load 0.75–1.25 mg, then 0.05–0.25 mg/day Amiodarone IV: 150 mg IV bolus over
10 min, then 1 mg/min for 6 hr, then 0.5 mg/min for 18 hr
Monitor for thyroid, hepatic, and thyroid toxicity; amiodarone should not be used as the first agent for rate control in the ambulatory setting; IV amiodarone can be helpful as a second-line rate control agent in hospitalized patients.
PO: 800–1600 mg qd for 1–3 wk for load, divided bid or tid, maintenance at 200–400 mg/day
IV, intravenous; PO, per os.
C. ASSESSING THE NEED FOR STROKE PROPHYLAXIS
1. Based on the Framingham data, AF increases the risk of stroke fivefold, independent of heart failure and coronary artery disease. The overall incidence of stroke is 5% per year.[12]
2. Patients with AF and established risk factors should receive anticoagulation (warfarin) if no contraindications exist, targeting the international normalized ratio (INR) between 2 and 3.[11] Warfarin decreases the risk of stroke by two thirds in the following high-risk patients [13] [14] [15] [16] [17] [18] [19]:
▪ Those with valvular heart disease (most importantly mitral stenosis)
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▪ Those with a history of transient ischemic attack or stroke
▪ Those with evidence of an ischemic event on brain computed tomography
▪ Those with a history of hypertension (especially systolic blood pressure greater than 160 mmHg) ▪ Those with heart failure or cardiomegaly (on chest film)
▪ Those with diabetes
▪ Those with coronary artery disease
▪ Those with atrial thrombi or spontaneous echo contrast in left atrial appendage seen on TEE 3. Patients between the ages 65 and 75 without any of these conditions may benefit more from warfarin than
aspirin if no contraindications to anticoagulation exist.
4. In patients younger than 65 years old with none of these conditions, aspirin alone generally is sufficient. Aspirin is also acceptable in patients with contraindications to oral anticoagulation. Aspirin decreases the risk of stroke by one third.
D. RESTORING AND MAINTAINING SINUS RHYTHM
1. Rate and rhythm control in the treatment of AF have been compared in two recent clinical trials: Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM)[20] and RACE.[21] These studies indicate that a strategy of rhythm control has no significant mortality benefit over rate control with anticoagulation among older adults with minimally symptomatic AF.
2. Elective cardioversion and, if necessary, antiarrhythmic therapy should be used to restore and maintain sinus rhythm in patients with disabling or otherwise unacceptable symptoms (ACC/AHA/ECS class I
recommendation).[11]
3. Circumferential pulmonary vein ablation uses radiofrequency ablation to electrically isolate the pulmonary veins. It has been associated with improved survival (hazard ratio for death 0.46), 70% lower rates of AF recurrence, 55% reduction in major morbidities (heart failure, stroke, and transient ischemic attack), and improved quality of life. In addition, the maintenance of sinus rhythm in both ablation and antiarrhythmic groups was associated with significantly lower morbidity and mortality, challenging the results of AFFIRM and RACE.
E. ANTICOAGULATION BEFORE RESTORING SINUS RHYTHM
The ACC/AHA/ECS[11] class I recommendations for antithrombotic therapy to prevent ischemic stroke and systemic
embolism in patients with AF undergoing cardioversion are as follows:
1. Administer anticoagulation therapy regardless of the method (electrical or pharmacologic) used to restore sinus rhythm.
2. Anticoagulate patients with AF lasting more than 48 hours or of unknown duration for at least 4 weeks before and after cardioversion (INR 2 to 3).
3. For patients who need immediate cardioversion:
a. If not contraindicated, administer heparin concurrently with a weight-based intravenous bolus followed by a continuous infusion adjusted to prolong the activated partial thromboplastin time to 1.5 to 2 times the reference control value.
b. Next, provide oral anticoagulation (INR 2 to 3) for a period of at least 4 weeks, as for patients undergoing elective cardioversion.
c. Limited data from recent studies support the use of low molecular weight heparin for this indication.
4. Screening for the presence of thrombus in the left atrium or left atrial appendage with TEE is an alternative to routine pre-anticoagulation in candidates for cardioversion of AF. The risk of stroke is not different in patients who receive anticoagulation for 4 weeks than in those who undergo TEE-guided cardioversion.
5. TEE-guided cardioversion does not eliminate the need for at least 4 weeks of anticoagulation after cardioversion because the risk of thromboembolic events is higher in the 4 weeks immediately after
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to atrial stasis and subsequent thrombus formation.
6. Anticoagulation in chronic AF. Although a number of risk stratification models are available for patients with chronic AF, the CHADS2 score is currently the best validated ( Table 16-2 ).[22]
TABLE 16-2 -- CHADS2[*] AND ANTICOAGULATION IN ATRIAL FIBRILLATION