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Case Study: New Onset Atrial Fibrillation
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A 74-year-old woman presents for her annual physical examination and notes increasing fatigue over the prior 3 months. Her history is notable for longstanding, but now well-controlled, systolic hypertension. A physical examination demonstrates a blood pressure of 120/70 mm Hg and an irregular pulse of approximately 120 bpm at rest. The patient weighs 130 pounds with a body mass index of 22.
The remainder of her examination is completely normal with no clinical evidence of right- or left-sided congestive heart failure. An electrocardiogram confirms the diagnosis of atrial fibrillation with a ventricular response of 120 bpm and voltage criteria for left ventricular hypertrophy. An echocardiogram done a year earlier to evaluate left ventricular hypertrophy was notable only for mild, global left ventricular dysfunction with a left ventricular ejection fraction of 40% and mild mitral regurgitation. A subsequent exercise echocardiogram showed no evidence of myocardial ischemia.
The patient’s chronic medical regimen includes lisinopril 20 mg, metoprolol XL 25 mg and 81 mg aspirin daily.
A repeat echocardiogram performed in the office demonstrates an ejection fraction of 20% with global hypokinesis but normal left ventricular systolic and diastolic dimensions with normal pulmonary arterial systolic pressure. The patient has no family history of coronary artery disease, cardiomyopathy or atrial fibrillation.
Her review of systems is notable only for fatigue without complaint of snoring, chest pain, palpitations, weight gain or loss, orthopnea, dyspnea, peripheral edema or syncope. Tests including complete blood count, electrolytes, HbA1c and liver function to eliminate potential causes of fatigue were within normal limits.
Clinical Questions
This is a common clinical scenario that raises a number of important management questions:
- What medications should be chosen to control the rate acutely?
- What further work up is required for new onset AF?
- Should one restore sinus rhythm or choose a strategy of rate control?
- What are the anticoagulation requirements for this patient?
- If the decision is made to maintain sinus rhythm after the cardioversion, what are the best medical or procedural options?
Medications
The primary goals of AF management include symptom relief and thromboembolic prophylaxis. The acute management of this patient should be centered first on symptom relief in the form of improved rate control to reduce the resting heart rate to less than 110 bpm. Digoxin is less effective for rate control than beta-blockers or nondihydropyridine calcium-channel blockers (e.g., verapamil or diltiazem), but it can be considered if blood pressure is low.
Laboratory Tests
The standard laboratory evaluation for newly recognized AF is a thyroid stimulating hormone test. Assessing renal function is also reasonable if dabigatran is chosen as an anticoagulant or a renally cleared antiarrhythmic drug (e.g., sotalol, dofetilide) is contemplated for maintenance of sinus rhythm.
Rate vs. Rhythm Control
The decision to maintain sinus rhythm or choose a strategy of rate control is generally based on how easily symptoms can be mitigated with rate control. If the rate is easily controlled, it is reasonable to forego cardioversion. Conversely if the rate is difficult to control and the patient has progressive symptoms including those of heart failure, a strategy of cardioversion and maintenance of sinus rhythm is preferred.
In this patient case, the presence of worsened left ventricular function is likely the result of tachycardia and necessitates aggressive rate control in the short term. The condition is a reasonable justification to attempt restoration of sinus rhythm with the hope that left ventricular function will return to normal.
Restoring sinus rhythm by cardioversion should be preceded by measures to reduce the risk of pericardioversion stroke, including either a transesophageal echocardiogram to exclude left atrial appendage clot or a minimum of 3 consecutive weeks of dabigatran or 3 consecutive weeks with an INR of ³ 2, if using warfarin.
Anticoagulation
Recommendations for chronic anticoagulation in patients with AF are determined by clinical risk factors such as history of congestive heart failure, hypertension, age older than 64 or 75, diabetes mellitus or past stroke or TIA (Table 1). In addition, female sex and vascular disease also appear to increase the risk of stroke and have been added to a new risk stratification scheme called CHA2DS2-VASc. Regardless of the scheme, associated clinical characteristics rather than the pattern or frequency of AF determines stroke risk.
Source: Peter Zimetbaum, MD.
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In this patient’s case the risk factors for stroke, including sex, age and hypertension, together mandate chronic anticoagulation regardless of the decision to maintain sinus rhythm or control rate (Table 1). The choices for anticoagulation include warfarin with a target INR of ³ 2 or dabigatran 150 mg, provided that the creatinine clearance is greater than 30 ml/min. If the creatinine clearance is between 15 and 30 ml/min, a dabigatran dose of 75 mg twice a day is recommended. Continuing aspirin along with either warfarin or dabigatran is not necessary.
Other Options
In this case dabigatran was initiated. Rate control was attempted with an increased dose of metoprolol XL but was limited by hypotension. As a consequence, a TEE was performed to exclude an existing thrombus and allow cardioversion. The procedure demonstrated a left atrial appendage (LAA) velocity of > 20 cm/sec with faint contrast in the left atrium. This preserved LAA velocity and the absence of dense spontaneous left atrial contrast allowed DC cardioversion to be performed safely. In addition, an antiarrhythmic drug was prescribed to increase likelihood of maintenance of sinus rhythm prior to a reassessment for recovery of ventricular function. In this woman with left ventricular dysfunction without congestive heart failure, potential drug choices include dronedarone, dofetilide, sotalol or amiodarone (Table 2).
Source: Peter Zimetbaum, MD.
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here
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Amiodarone was chosen and initiated at a dose of 200 mg three times a day for 1 month with reduction to 200 mg a day after 1 month. Liver function tests, thyroid function tests and pulmonary function tests and a baseline chest x-ray were obtained at the time of amidoarone initiation. Left ventricular function returned to the baseline of 40% after 6 weeks of amiodarone. Given the high likelihood of recurrent AF and the patient’s presentation with tachycardia-mediated myopathy, her low, 200 mg/day dose of amiodarone was continued. Ultimately, if amiodarone proves unsuccessful or not tolerated, referral for catheter-based pulmonary vein isolation is an option.