Understanding Atrial Fibrillation

Atrial Fibrillation

• Atrial fibrillation is characterized by an irregular heartbeat.

Impact of Atrial Fibrillation

• Atrial fibrillation increases a person's risk of stroke by four to five times.
• Atrial fibrillation causes approximately 25% of ischemic strokes due to blockage of blood flow to the brain.
• Atrial fibrillation doubles the risk of heart-related deaths.
• Absence of atrial contraction can result in a loss of cardiac output anywhere from 15-30%, due to the absence of "atrial kick", contributing to heart failure.

Risk Factors

• Advancing age is a risk factor.
• High blood pressure is a risk factor.
• Coronary artery disease is a risk factor.
• Cardiomyopathy is a risk factor.
• Obesity is a risk factor.
• European ancestry is a risk factor.
• Being an athlete is a risk factor.
• Diabetes is a risk factor.
• Heart failure is a risk factor.
• Hyperthyroidism is a risk factor.
• Chronic kidney disease is a risk factor.
• Heavy alcohol use is a risk factor.
• Rheumatic heart disease is a risk factor.
• Valvular heart disease is a risk factor.
• Enlargement of the chambers on the left side of the heart is a risk factor.
• Pericarditis/myocarditis is a risk factor.
• Sleep apnea is a risk factor.

Valvular vs Non-Valvular Afib

• Valvular AFib involves moderate-to-severe mitral stenosis, potentially requiring surgical intervention, or the presence of an artificial (mechanical) heart valve.
• Non-valvular AFib occurs in the absence of moderate-to-severe mitral stenosis or a mechanical heart valve.

Clinical Presentation

• Many people do not experience any symptoms and are unaware of their diagnosis, which is sometimes an incidental finding upon examination.
• Symptomatic presentation can include general fatigue.
• Symptomatic presentation can include a rapid and irregular heartbeat.
• Symptomatic presentation can include fluttering or "thumping" in the chest.
• Symptomatic presentation can include dizziness.
• Symptomatic presentation can include shortness of breath and anxiety.
• Symptomatic presentation can include weakness.
• Symptomatic presentation can include faintness or confusion.
• Symptomatic presentation can include fatigue when exercising.
• Symptomatic presentation can include sweating.
• Symptomatic presentation can include chest pain or pressure, which requires calling 911.

Physical Exam

• Irregular heart rhythm is the hallmark finding on physical examination, along with tachycardia (typically 110s-140s) and hypotension.
• Possible findings include JVD, rales, or effusions from heart failure.
• Possible findings include murmurs suggesting stenosis or regurgitation.
• Possible findings include lower extremity edema (HF or DVT).
• Possible findings include exophthalmia.
• Possible findings include signs of stroke such as facial droop, arm weakness, and slurred speech.

EKG

• On EKG, there will be no visible P waves (no measurable PR interval) and an irregularly irregular QRS complex.
• Ventricular rate is frequently fast.
• EKG is the gold standard for Atrial Fibrillation diagnosis.

Classifying Atrial Fibrillation

• Paroxysmal AF terminates spontaneously or with intervention within 7 days of onset, and episodes may recur with variable frequency.
• Persistent AF is continuous and lasts greater than 7 days.
• Long-standing persistent AF is continuous and lasts more than 12 months in duration.
• Permanent AF occurs when the patient and clinician decide to stop further attempts to restore and/or maintain sinus rhythm.
• Acceptance of AF represents a therapeutic attitude on the part of the patient and clinician rather than an inherent pathophysiological attribute of AF.
• Acceptance of AF may change as symptoms, efficacy of therapeutic interventions, and patient and clinician preferences evolve.
• Nonvalvular AF occurs in the absence of rheumatic mitral stenosis, a mechanical or bioprosthetic heart valve, or mitral valve repair.

Labs

• Labs to run include CBC.
• Labs to run include CMP.
• Labs to run include TSH.
• Labs to run include BNP.
• Labs to run include PT/PTT/INR.

Other Diagnostic Tests

• Echocardiograms evaluate the size and function of atria and ventricles, detect valvular heart disease, left ventricular hypertrophy, and pericardial disease.
• Transesophageal Echocardiogram (TEE) is the most sensitive and specific technique to detect LA thrombi.
• Event Recorders (Implantable loop recorders, Holter monitors) identify arrhythmia if intermittent and to correlate symptoms or rate control strategies.
• Other diagnostic tests include stress tests.
• Other diagnostic tests include EP studies.

Management

• The goal of treatment for AF is prevention of thromboembolism, utilizing the CHADS score to determine stroke risk.
• Rate control is preferred over rhythm control.
• Beta-Adrenergic Receptor Blockers such as atenolol, metoprolol, nadolol, propranolol, and sotalol for rate control.
• Nondihydropyridine Calcium Channel Blockers such as diltiazem and verapamil for rate control.
• Digitalis Glycoside such as Digoxin for rate control.
• Rhythm control is for patients that do not tolerate loss of atrial kick (hemodynamic instability).
• Synchronized cardioversion for rhythm control.
• Pharmacologic cardioversion using dofetilide, flecainide, propafenone, ibutilide, or amiodarone (consider long half-life, pulmonary toxicity, thyroid dysfunction) for rhythm control.

Anticoagulation

• Use vitamin K antagonist, Warfarin (serum monitoring: goal INR 2-3).
• Use direct thrombin inhibitor: dabigatran (Pradaxa)- 150 mg PO bid (no serum monitoring).
• Use Factor Xa inhibitors rivaroxaban, edoxaban, and apixaban (no serum monitoring).
• Xarelto- 20 mg PO qd (if switching from warfarin to Xarelto, d/c warfarin and start Xarelto when INR < 3).
• Eliquis- 5 mg PO bid (2.5 mg PO bid if 2 of following apply: older than 80yrs, wt < 60kg, or Cr>1.5).
• Nonvitamin K antagonist oral anticoagulants (NOACs) are contraindicated in patients with clinically significant mitral stenosis or mechanical valves.

Other Treatments

• Watchman Device: left atrial appendage (LAA) closure device that is permanently implanted to close off the left atrial appendage, so that clots that form within the LAA can't enter circulation.
• Watchman Device is indicated for patients with non-valvular Afib at risk for stroke and is an alternative for patients who can't be on anticoagulation (h/o bleed, or high risk for bleeding, drug interactions, others).
• Risks of Watchman Device include LAA rupture during device implant and infection; patients probably still need to take ASA.
• Pacemaker: for slow heart rate.