The following cases and commentary, which focus on atrial fibrillation, are excerpted from ACP's Medical Knowledge Self-Assessment Program (MKSAP 16). Part A of MKSAP 16 was released on July 31.
Case 1: Acute, symptomatic onset
A 76-year-old woman is evaluated in the emergency department for dizziness, shortness of breath, and palpitations that began acutely one hour ago. She has a history of hypertension and heart failure with preserved ejection fraction. Medications are hydrochlorothiazide, lisinopril, and aspirin.
On physical examination, she is afebrile, blood pressure is 80/60 mm Hg, pulse rate is 155/min, and respiration rate is 30/min. Oxygen saturation is 80% with 40% oxygen by face mask. Cardiac auscultation reveals an irregularly irregular rhythm, tachycardia, and some variability in S1 intensity. Crackles are heard bilaterally one-third up in the lower lung fields.
Electrocardiogram demonstrates atrial fibrillation with a rapid ventricular rate.
Which of the following is the most appropriate acute treatment?
Case 2: Episodes after MI
A 56-year-old man is evaluated in the hospital for paroxysmal episodes of atrial fibrillation. The patient develops increasing shortness of breath during these episodes. Five days ago, he was admitted for an acute myocardial infarction and cardiogenic shock and received a drug-eluting stent in the left anterior descending coronary artery. Medications are lisinopril, digoxin, furosemide, aspirin, clopidogrel, eplerenone, simvastatin, and unfractionated heparin.
On physical examination, the patient is afebrile, blood pressure is 92/65 mm Hg, and pulse rate is 75/min. Oxygen saturation is 95% with 3 L oxygen by nasal cannula. Cardiac examination reveals estimated central venous pressure of 12 cm H2O. Heart sounds are distant and regular. There is a grade 2/6 holosystolic murmur at the cardiac apex. A summation gallop is present. Crackles are auscultated bilaterally in the lower lung fields.
Transthoracic echocardiogram shows left ventricular ejection fraction of 32%.
Which of the following is the most appropriate treatment for this patient's atrial fibrillation?
Case 3: Post-ablation follow-up
A 61-year-old man is evaluated during a follow-up examination. He has a four-year history of atrial fibrillation and underwent atrial fibrillation ablation six months ago. He has had no symptoms of palpitations, fatigue, shortness of breath, or presyncope since the procedure. He has hypertension and type 2 diabetes mellitus. Medications are lisinopril, atenolol, metformin, and warfarin.
Blood pressure is 124/82 mm Hg and pulse rate is 72/min. Cardiac examination discloses regular rate and rhythm. The rest of the physical examination is normal.
Electrocardiogram demonstrates normal sinus rhythm.
Which of the following is the most appropriate treatment?
A. Continue warfarin
B. Switch to aspirin
C. Switch to clopidogrel
D. Switch to aspirin and clopidogrel
Case 4: Palpitations and mitral regurgitation
A 54-year-old woman is evaluated for palpitations. For the past week, she has noted an irregular heart rhythm. She has not experienced chest discomfort, lightheadedness, syncope, orthopnea, paroxysmal nocturnal dyspnea, or edema.
She has a history of chronic severe mitral regurgitation due to myxomatous mitral valve degeneration. Her annual transthoracic echocardiogram two months ago showed left ventricular ejection fraction of 65% with left ventricular end-diastolic diameter of 53 mm and end-systolic diameter of 38 mm. The left atrium was dilated, with an area of 28 cm2. The mitral valve leaflets were thickened and redundant, with posterior prolapse and severe, anteriorly directed mitral regurgitation (effective regurgitant orifice area of 0.4 cm2). The estimated right ventricular systolic pressure was 38 mm Hg.
On physical examination, temperature is 37.4°C (99.3°F), blood pressure is 132/74 mm Hg, pulse rate is 95/min and irregular, and respiration rate is 15/min. Estimated central venous pressure and carotid upstrokes are normal. The apical impulse is not palpable. There is a grade 3/6 holosystolic murmur at the apex radiating to the right upper sternal border. Lungs are clear to auscultation.
Electrocardiogram shows atrial fibrillation with a ventricular rate of 95/min with left axis deviation and normal intervals.
In addition to starting warfarin, which of the following is the most appropriate management at this time?
B. Direct-current cardioversion
C. Exercise echocardiography
D. Mitral valve repair surgery
Answers and commentary
Correct answer: C. Cardioversion.
This patient with atrial fibrillation is hemodynamically unstable and should undergo immediate cardioversion. She has hypotension and pulmonary edema in the setting of rapid atrial fibrillation. In patients with heart failure with preserved systolic function, usually due to hypertension, the loss of the atrial “kick” with atrial fibrillation can sometimes lead to severe symptoms. The best treatment in this situation is immediate cardioversion to convert the patient to normal sinus rhythm. Although there is a risk of a thromboembolic event since she is not anticoagulated, she is currently in extremis and is at risk of imminent demise if not aggressively treated. In addition, she acutely became symptomatic 1 hour ago, and while this is not proof that she developed atrial fibrillation very recently, her risk of thromboembolism is low if the atrial fibrillation developed within the previous 48 hours.
Adenosine can be useful for diagnosing a supraventricular tachycardia and can treat atrioventricular node-dependent tachycardias such as atrioventricular nodal reentrant tachycardia, but it is not useful in the treatment of atrial fibrillation.
Amiodarone can convert atrial fibrillation to normal sinus rhythm as well as provide rate control, but immediate treatment is needed and amiodarone may take several hours to work. Oral amiodarone may be a reasonable option for long-term atrial fibrillation prevention in this patient given the severity of her symptoms, especially if she has significant left ventricular hypertrophy.
Metoprolol or diltiazem would slow her heart rate; however, she is hypotensive and these medications could make her blood pressure lower. In addition, she is in active heart failure, and metoprolol or diltiazem could worsen the pulmonary edema.
- Patients with atrial fibrillation who are hemodynamically unstable should undergo immediate cardioversion.
Correct answer: A. Amiodarone.
Amiodarone is the best option for managing symptomatic atrial fibrillation in the setting of heart failure. Patients with heart failure and myocardial infarction are at an increased risk of developing atrial fibrillation. Although amiodarone has many extracardiac side effects, it is the most effective agent for preventing atrial fibrillation recurrences, and it is one of the few agents proved safe in patients with heart failure, left ventricular hypertrophy, coronary artery disease, or previous myocardial infarction. In addition, amiodarone has β-blocking properties that can help with rate control. This patient is not currently taking a β-blocker because of the cardiogenic shock, but one should be started as soon as the patient's heart failure is stabilized.
Disopyramide has negative inotropic effects, which can be detrimental to someone with reduced left ventricular function and heart failure, and is contraindicated in this setting.
Dronedarone increases mortality in patients with New York Heart Association class IV heart failure or class II or III heart failure with recent decompensation, such as this patient, and thus should not be used.
Flecainide is contraindicated after a myocardial infarction because it increases the risk of polymorphic ventricular tachycardia.
Like amiodarone, sotalol is a class III antiarrhythmic agent, but because of its more potent β-blocking effects, it should not be used in the setting of acute heart failure.
While not one of the options listed, dofetilide is another medication for prevention of atrial fibrillation in the setting of heart failure, but this agent requires careful monitoring of the QT interval.
- Amiodarone is the best option for managing symptomatic atrial fibrillation in the setting of structural heart disease or heart failure.
Correct answer: A. Continue warfarin.
Warfarin should be continued in this patient. For the first 2 to 3 months after an atrial fibrillation ablation, all patients should take warfarin. The best management strategy thereafter is to provide anticoagulation as if the ablation did not occur, using a tool such as the CHADS2 score to risk stratify. Although the patient has had no symptoms of atrial fibrillation since his ablation procedure, patients may have either asymptomatic episodes or a symptomatic recurrence of atrial fibrillation after the ablation and can be at risk for stroke. This patient has hypertension and diabetes mellitus and, with a CHADS2 score of two, has a 4.0% risk of stroke per year. Even though his blood pressure is currently controlled, he is taking blood pressure-lowering agents and has a history of hypertension.
Switching to aspirin or clopidogrel does not provide the same protective benefit, and it is not appropriate to discontinue all anticoagulation. If the CHADS2 score is zero, aspirin alone is the preferred agent. If the CHADS2 score is one, either aspirin or warfarin is acceptable. If a patient is unable take warfarin, aspirin and clopidogrel provide a greater stroke reduction than aspirin alone, but this combination is less effective for stroke reduction than warfarin and carries a higher bleeding risk. New agents such as dabigatran and rivaroxaban may also be an option; however, they have not been studied in the post-atrial fibrillation ablation setting.
- Following atrial fibrillation ablation, anticoagulation should continue for 2 to 3 months; thereafter, anticoagulation should be guided by risk stratification (CHADS2 score).
Correct answer: D. Mitral valve repair surgery.
This patient should undergo mitral valve repair surgery. In patients with chronic severe mitral regurgitation and normal left ventricular systolic function, surgical repair is indicated in the setting of new-onset atrial fibrillation to reduce possible long-term adverse events. Pulmonary vein isolation or a maze procedure may be performed concomitantly at the time of mitral valve repair to reduce the risk of recurrent atrial fibrillation. In addition, chronic anticoagulation therapy with warfarin is indicated to reduce the risk of thromboembolism, which is much higher than in nonvalvular atrial fibrillation.
A rhythm-control strategy using an antiarrhythmic drug such as amiodarone is not likely to maintain sinus rhythm over the long term in this patient and may have a high risk of adverse effects with prolonged use.
Direct-current cardioversion (after ruling out a left atrial thrombus) is not likely to be associated with long-term maintenance of sinus rhythm given this patient's severe mitral regurgitation and left atrial dilation.
Exercise echocardiography may be useful in patients with chronic severe mitral regurgitation to evaluate the pulmonary artery pressure during exercise by Doppler imaging, but this diagnostic test does not offer additional useful information for this patient who already meets the criteria for valve repair surgery.
- In patients with chronic severe mitral regurgitation and normal left ventricular systolic function, surgical repair is indicated in the setting of new-onset atrial fibrillation.