How Should I Manage This Patient with Atrial Fibrillation

Family Practice Recertification, July 2015, Volume 33, Issue 7

A 59-year-old male with a history of hypertension and type 2 diabetes is admitted by you foratrial fibrillation found on routine examination. He indicates that the only symptoms he has experienced is tiredness for the last few weeks and mild dyspnea on exertion. He has not had any previous episodes of AF.

How should I manage this patient with atrial fibrillation?

A 59-year-old male with a history of hypertension and type 2 diabetes is admitted by you foratrial fibrillation (AF) found on routine examination. He indicates that the only symptoms he has experienced is tiredness for the last few weeks and mild dyspnea on exertion. He has not had any previous episodes of AF.

An echocardiogram 2 years ago showed a hypertrophied and slightly dilated left ventricle with mild mitral regurgitation. He has been treated effectively with enalapril HCl (Vasotec®) for blood pressure control. His blood pressure is 135/90 mm Hg; his pulse is 125 beats per minute and irregular. He has no jugular venous distention, and his lungs are clear. Cardiac examination reveals an irregularly irregular rhythm with a grade 2/6 holosystolic murmur at the apex radiating to the left axilla.

How would you initially evaluate this patient?

The history of a patient with new onset atrial fibrillation can be very useful in guiding further evaluation with testing. There are predisposing factors for atrial fibrillation and triggers. This patient carries predisposing conditions including diabetes and hypertensive heart disease.

Other predisposing factors include increasing age, thyroid disorders, obstructive sleep apnea, obesity, infiltrative disorders, cardiac ischemia and genetic variants. Triggers for atrial fibrillation include sleep deprivation, exogenous intake of certain drugs including alcohol, inflammation, infection and oxidative stress.

Following the history and physical exam, the electrocardiogram should be re-evaluated for possible clues to the etiology of the atrial fibrillation and associated conditions. Basic laboratory evaluation should include a complete blood count, basic chemistry panel and a thyroid-stimulating hormone (TSH). Further testing should be guided by the history and may include a D-Dimer or liver function testing.

While history, physical exam and labs may guide specific imaging, a chest X ray and an echocardiogram should be performed to exclude significant pulmonary or structural heart disease. The above patient has a history of mild mitral regurgitation and his exam suggests it is stable but an echocardiogram to confirm lack of progression should be performed.

Should he be evaluated for coronary heart disease?

Chest pain or exertional symptoms can be difficult to separate from symptoms related to a non-physiologic heart rate. In the inpatient setting, this often leads to some form of ischemic evaluation. Exercise stress testing with imaging may be performed but may be invalid due to abnormal resting heart rate, abnormal heart rate response with exercise, or nodal blockade from medications. The most common noninvasive modality employed is pharmacologic perfusion imaging because evaluation is not heart rate dependent. Coronary angiography may be preferred with significant anginal symptoms or a significant rise in cardiac enzymes.

Before initiating any long-term specific atrial fibrillation management strategies, treatment of precipitating or reversible causes of atrial fibrillation should be performed.

What agents are available for rate control and which do you favor?

Initial inpatient rate control strategies may be guided by institution protocols, but calcium channel blockers (CCBs), such as diltiazem and verapamil, or beta blockers (BBs), such as esmolol and metoprolol, are both acceptable initial bolus strategies. Diltiazem or esmolol drips are favored for continued intravenous rate control. Both are short-acting and can be used to transition to short-acting oral equivalents to be titrated with each subsequent dose. Once the rate is adequately controlled, the total daily dose of short-acting can be converted to long-acting with the same total daily dose.

If the patient is experiencing heart failure symptoms due to systolic dysfunction, CCBs may worsen the heart failure due to their negative inotropic effect. I favor BBs since they would also be indicated for mortality reduction in heart failure.

Occasionally, multiple nodal blocking agents will be required for adequate rate control. Digoxin is another rate controlling drug that is best reserved for patients with systolic heart failure, as a secondary agent or in patients who cannot tolerate the lowering blood pressure effect of CCBs or BBs.

For this patient, I would start an intravenous nodal agent with a bolus to get to therapeutic levels. I often start a PO medication almost immediately and titrate up with each dose at 6 hours while titrating the drip off at the same time.

Is cardioversion appropriate for this patient?

Cardioversion is reasonable in patients with rates that cannot be controlled, have exertional symptoms despite rate control, comorbid heart failure or patient preference. The decision to cardiovert an asymptomatic patient is complex and has been the matter of study and debate for many years.

The AFFIRM and RACE trials show that there is no mortality reduction with a rhythm control strategy over rate control and RACE-2 suggested that we could be more lenient in certain patients when a rate control strategy was chosen. If rate control strategy is chosen, exercise testing may be of use in highly functional patients to ensure adequate rate control at higher exertion. These rhythm versus rate control studies cannot be broadly applied to all patients, particularly the young, since the study population’s average age was 69 with a range of 60-80 years old.

Many physicians will give patients a “shot “ at normal sinus rhythm and plan an electrical cardioversion for anyone who presents with their first episode of atrial fibrillation. This may be reasonable since atrial tachycardia remodeling may predispose to more difficult-to-control atrial fibrillation in the future. The patient’s age, comorbidities and particular echo characteristics may inform the physician about success of an electrical cardioversion attempt. It should be noted that in the stable patient, cardioversion should not be attempted unless the patient can tolerate anticoagulation.

For this patient, I would favor rate control and consider an electrical cardioversion attempt if no reversible precipitating factor was found.

What is the role of chemical cardioversion?

Sometimes electrical cardioversion is unsuccessful, or there may be an early return of atrial fibrillation. In these situations, chemical cardioversion or chemically-assisted electrical cardioversion, may be more successful. There are a number of available antiarrhythmics for atrial fibrillation and the drug chosen is often based on physician familiarity, but should be also guided by the presence or absence of structural heart disease and comorbidities. The risks of antiarrhythmics, due to possible toxicity or proarrhythmic properties should be considered prior to initiation.

Flecainide, dofetilide, propafenone and IV ibutilide are useful for cardioversion if contraindications are not present. Amiodarone may also be considered. Flecainide and dofetilide can be used for cardioversion in the outpatient setting once they have been attempted once and shown to be safe in a monitored setting. Dofetilide should never be initiated outside of the hospital.

Once a patient is in permanent atrial fibrillation, antiarrhythmics should be discontinued.

Due to the side effects and monitoring required for antiarrhythmics, I would not consider antiarrhythmics as an initial strategy in this patient.

When should cardioversion be performed?

Cardioversion can be attempted during the hospitalization if the provoking factor is no longer active. Since our patient was asymptomatic, it is unknown when his atrial fibrillation started. Atrial fibrillation that has been present for more than 48 hours should not be cardioverted without an extended period of anticoagulation (3 weeks), or performing a transesophageal echocardiogram to exclude left atrial appendage thrombus. Cardioembolic risk is a significant concern with atrial fibrillation and the risk is greater after cardioversion if atrial thrombus is not excluded.

Why a transesophageal echocardiogram?

During atrial fibrillation, the flow in the atria is reduced. The left atrial appendage is a posterior structure where velocities are significantly lower and stasis can occur.

Because of its posterior location in the chest, it is difficult to evaluate with enough accuracy when imaging from the chest wall. Therefore, transthoracic echocardiogram is not appropriate and prior to performing electrical cardioversion, a transesophageal echocardiogram is required if the patient has not been anticoagulated for 3 weeks prior to cardioversion attempt.

In the absence of a precipitating cause, and the absence of heart failure requiring diuresis, I would consider initiating therapeutic anticoagulation, followed by a transesophageal echocardiogram and cardioversion, if no thrombus is identified.

Since you mentioned cardioembolic risk, what is the risk of stroke?

For years, the CHADS2 algorithm for deciding on risk of cardioembolic risk was utilized but has now been increasing replaced by the CHA2DS2-VASC calculation. CHA2DS2-VASC includes major and minor risk factors listed below with an associated point system. Vascular disease is defined as a history of myocardial infarction, peripheral arterial disease and aortic plaque.

Because of the increased number of variables in the CHA2DS2-Vasc system, more patients are categorized as being high enough risk for anticoagulation. The low risk group (score = 0) are therefore believed to be more reliably defined as being low risk enough to consider not giving anticoagulation.

Risk Factor

Score

Congestive heart failure or LV dysfunction

1

Hypertension

1

Age ≥ 75

2

Diabetes mellitus

1

Stroke TIA or systemic embolism

2

Vascular disease

1

Age 65-74

1

Sex category - female

1

Score total

Adjusted Stroke Rate

(% per year)

0

0

1

1.3

2

2.2

3

3.2

4

4.0

5

6.7

6

9.8

7

9.6

8

6.7

9

15.2

Who should be treated with anticoagulation?

Similar to the CHADS2 scheme, a score of 2 or greater should lead the patient and provider towards anticoagulating the patient, taking into account bleeding risks and patient preferences, with a vitamin K antagonist or a target-specific direct acting oral anticoagulant.

A score of one in a man should prompt consideration of anticoagulation. A man with no risk factors, or a woman with no other risk factors, may forego anticoagulation. Anyone undergoing cardioversion, regardless of risk status, should be anticoagulated for 4 weeks following a cardioversion.

Our patient has a CHA2DS2-Vasc score of 2 (for hypertension and diabetes) that equates to a risk of 2.2% annual risk of thromboembolism. Therefore in the absence of an elevated bleeding risk, I would anticoagulate this patient.

Is aspirin an acceptable alternative to anticoagulation?

Aspirin therapy (325 mg) may be reasonable in a patient with a CHA2DS2-Vasc score of 1, but strong consideration should be made for full anticoagulation in a patient with low bleeding risk.

In my practice, for patients with a CHA2DS2-Vasc of 1 or higher, I recommend anticoagulation and discuss with the patient the options available. Any decision pertaining to anticoagulation should be reevaluated on a regular basis since bleeding risks and thrombotic risks change over time.

Are there drugs for the primary prevention of atrial fibrillation?

Drugs for primary prevention have been tested in the highest risk populations who would develop atrial fibrillation. For instance, ACE inhibitors or ARBs may reduce frequency of new-onset atrial fibrillation in patients with reduced ejection fraction, and may be reasonable to prevent new-onset AF in patients with hypertension. Statins may reduce frequency of atrial fibrillation in patients after coronary bypass surgery. These drugs should not be used for primary prevention if the patient has no history of cardiovascular disease.

Are there special groups of patients where the above general recommendations may not apply?

Yes. Patients with hypertrophic cardiomyopathy may not tolerate AF well and may need cardioversion early and initiation of antiarrhythmics. Regardless of their CHA2DS2 score, patients with AF and hypertrophic cardiomyopathy should be anticoagulated. In a patient presenting with acute coronary syndrome, IV BB is preferred to CCB and urgent cardioversion may be required. For adequate rate control in the patient with hemodynamic instability or heart failure, amiodarone or digoxin may be useful.

In patients with Wolff-Parkinson-White syndrome, presenting with an irregular wide complex rhythm, typical nodal blocking agents can cause harm by accelerating conduction to the ventricle through a bypass tract. Therefore, IV procainamide or ibutilide is recommended in the stable patient and urgent cardioversion is recommended in the unstable patient. Beta blockers are preferred in patients with thyrotoxicosis and CCB are preferred in patients with pulmonary disease. Lastly, there are a number of preventive strategies and treatment considerations for the postoperative cardiac and thoracic surgery patient that may be employed.

When would you consider catheter ablation for atrial fibrillation?

If a rhythm control strategy is preferred for symptomatic paroxysmal AF, but the rhythm is refractory to, or the patient is intolerant of, at least one antiarrhythmic, catheter ablation should be considered. Catheter ablation is also reasonable in symptomatic paroxysmal atrial fibrillation rather than antiarrhythmic trials if the patient prefers and if there is available expertise after discussion of the procedural risks and benefits.