atrial fibrillation

• atrial fibrillation is a supraventricular attack arrhythmia, meaning this arrhythmia originates from irritability or re-entrant circuit above the ventricles
• anything that stretches the myocardium,causes ischaemia to the heart, causes inflammation or stimulates SNS can lead to atrial fibrillation
• cardiac causes of Atrial fibrillation include: CHF(stretch), dilated cardiomyopathy(stretch), valvular disease especial mitral stenosis(stretch), CAD or MI(ischemia), rheumatic fever that lead to rheumatic heart disease(inflammation) and hypertension that leads to ventricular hypertrophy(stretch).
• non-cardiac causes of atrial fibrillation include: COPD/Pneumonia/pulmonary embolism(cause of hypoxemia), thyrotoxicosis/hyperthyroidism(stimulate SNS that will stimulate atria), Holiday heart syndrome(stimulate SNS,electrolyte change especially k and mg), Pheochromocytoma(SNS)
• factors that increase SNS include: sepsis,post-operation,pheochromocytoma(noncancerous tumor on adrenal glands),thyrotoxicosis and sympathomimetics include cocaine, methamphetamines etc
• atrial fibrillation less than 7 days is called paroxysmal atrial fibrillation.
• atrial fibrillation more than 7 days is called persistent atrial fibrillation.
• atrial fibrillation that has been present for more than 1 year is called permanent atrial fibrillation
• complications of atrial fibrillation include: thromboembolic, stroke/TIA/CVA, acute mesenteric ischemia/ ischemic colitis, acute limb ischemia, acute heart failure/shock, pulmonary edema/dyspnea, tachycardia. prolong tachycardia can lead to dilated cardiomyopathy.
• atrial fibrillation diagnostics include: 12-lead ECG, ecocardiogram, 24-hr holter monitor and transesophageal echocardiogram(TEE)
• we do ECG to determine the rate of ventricles, if their slow,normal or rapid
• we do echocardiogram to check for big dilatation of left atrium, if there is any thrombus or if there is any vascular disease like mitral stenosis
• 24-hr holter monitor we do it if both echo and ECG does not show any signs of A-fib but we still suspect it
• for treatment of A-fib, we focus on rate control(less than 110), rhythm control(restore to sinus rhythm), and anticoagulation.
• rate control treatment include: beta-blocker(metoprolol,carvidelol), calcium channel blocker( verapamil,diltiazem) and cardiac glycoside(digoxin)
• rhythm control treatment include: direct current cardioversion and antiarrhythmics(amiodarone and flecainide)
• we do direct current cardioversion in patients that are hemodynamically unstable, they had A-fib for less than 48(no thrombus) or if they had thrombus they have anticoagulated for 3-4 weeks before doing cardioversion.
• We do TEE to confirm left atrium thrombus
• antiarrhythmetics increase risk of torsades de poites(prolonged QT)
• If rate control therapy and rhythm control therapy are not effective, consider surgical intervention(radio frequency ablation and maze procedure)
• for anticoagulation, do CHADSVASC score to determine if the patient is at high risk of thromboemboli or not before you can give anticoagulats
• CHADVASC criteria: CHF(1),HTN(1),AGE>75(2),DM(1),STROKE/TIA(2),VASCULAR DISEASE(1),AGE64-75(1),SEX-FEMALE(1)
• 2 or more points they are at high risk of stroke give anticoagulants
• 1 point, they might be having GI bleeding or at high risk of bleeding
• zero point no need to give anticoagulats
• for non-valvular atrial fibrillation give direct oral anticoagulants(DOACs)- rivaroxaban, apixaban and edoxaban
• if patient has valvular atrial fibrillation or they are non-valvular atrial fibrillation but have chronic kidney disease give warfarin
• when you give warfarin monitor INR- make sure it is in the therapeutic range(safety of drug). no valvular disease (INR 2-3). IF there is valvular disease ( INR 2.5-3.5)
• stroke reduction therapy we give warfarin,oral,5mg daily
• therapeutic range INR is 2-3 in atrial fibrillation patients
• INR should be checked 48hrs after giving warfarin and therefore should be monitored every day or every 2 days
• rate control therapy include atenolol,oral,50-100mg daily
• atenolol is contraindicated in patients asthma,Hf, bradycardia and peripheral vascular disease
• rate control therapy also include carvedilol,oral, 3.125mg 12hourly. double dose every 2 weeks but max dose is 25mg 12hrly. decrease dose if they do not tolerate the given new dose
• digoxin is added if the rate is not controlled by beta-blocker.
• digoxin,oral,0.125mg daily then adjust dose according to how the rate is responding and trough plasma level. digoxin plasma level should be 0,6-1 mmol/L
• patients at high risk of digoxin toxicity include: ederly,renal dysfunction patients,hypokalemia and patients with lean body mass
• we can give calcium channel blocker to patients who are contraindicated for beta-blocker. Verapamil,oral,40-120mg 8hrly.
• verapamil is also contraindicated in HF due to LV dysfunction. rememmber verapamil is a negative inotrope hence is contraindicated in Heart failure
• if atrial fibrillation still continues despite giving beta blockers and CCB, then refer to specialist for consideration of giving antiarrhythmic(amiodarone), atrioventricular node ablation and pacemaker insertion.