HY lecture notes:
Atrial fibrillation –> absent p-waves + irregularly irregular intervals between QRS complexes.
For Step 1, you literally just need to know the ECG strip. For 2CK, you need to know how to Tx.
There are two arms of management: 1) blood-thinning, and 2) actual Tx of the AF.
Regarding blood thinning, we use the CHADS2 / CHA2DS2-VASc score.
Congestive heart failure, HTN, Age 75 or older, Diabetes, Hx of Stroke/TIA (the latter is 2 points).
If a patient has AF and has 0 or 1 points, give aspirin.
If a patient with AF has 2 or more points, give anticoagulation:
- If valvular AF (meaning pt has MR/MS or prosthetic valve), give warfarin.
- If non-valvular AF (meaning pt doesn’t have any valve issues), give a NOAC (New Oral AntiCoagulants). NOACs refer to the direct thrombin inhibitor dabigatran and the direct Xa inhibitors rivaroxaban, apixaban, and edoxaban.
Because there are variants to this score, the USMLE will never be borderline or ambiguous with what kind of answer they want: you’re either going to get a vignette where he or she has AF but no other CHADS risk factors, or you’ll get a vignette where the patient literally has all of the risk factors, where you don’t even need to calculate the score because qualitatively the result is obvious for needing to give anticoagulation.
Then to address the actual AF, do rate control before rhythm control. Management is complex and pedantic, but for the USMLE what you need to know is:
First drug we give is metoprolol. If cannot receive, give verapamil. These drugs both intercept the AF rhythm at the AV node.
Contraindications to beta-blockers are depression (beta-blockers cause depression), sexual dysfunction, COPD, asthma (if Hx of hospitalization or oxygen use), and 2nd or 3rd-degree heart block. Although metoprolol is beta-1 selective, there’s still considered to be marginal degree of beta-2 overlap such that we simply avoid the drug if the patient has any of the aforementioned contraindications.
If patient fails rate control, we go to rhythm control.
If the patient has no structural (e.g., LVH) or coronary artery disease, the first drug we use is flecainide, which is a type Ic sodium channel blocker.
If the patient has structural or coronary artery disease, use one of the other antiarrhythmics such as amiodarone, dronedarone, or dofetilide.
