A 21-year-old woman presents with palpitations and anxiety. She had a recent outpatient ECG that was suggestive of supraventricular tachycardia, but her previous physician failed to find any underlying disease. No other significant past medical history. Her vital signs include blood pressure 102/65 mm Hg, pulse 120/min, respiratory rate 17/min, and temperature 36.5℃ (97.7℉). Electrophysiological studies reveal an atrioventricular nodal reentrant tachycardia. The patient refuses an ablation procedure so it is decided to perform synchronized cardioversion with consequent ongoing management with verapamil. Which of the following ECG features should be monitored in this patient during treatment?

Amplitude and direction of the T wave

A 29-year-old woman with Wolff-Parkinson-White syndrome presents to her cardiologist’s office for a follow-up visit. She collapsed at her job and made a trip to the emergency department 1 week ago. At that time, she received a diagnosis of atrial fibrillation with rapid ventricular response and hemodynamic instability. While in the emergency department, she underwent direct-current cardioversion to return her heart to sinus rhythm. Her current medications include procainamide. At the cardiologist’s office, her heart rate is 61/min, respiratory rate is 16/min, the temperature is 36.5°C (97.7°F), and blood pressure is 118/60 mm Hg. Her cardiac examination reveals a regular rhythm and a I/VI systolic ejection murmur best heard at the right upper sternal border. An ECG obtained in the clinic is shown. Which of the following is the most appropriate treatment to prevent further episodes of tachyarrhythmia?

Refer her for electrophysiology (EP) study and ablation

Begin anticoagulation with dabigatran

Add verapamil to her medication regimen

Begin anticoagulation with warfarin

Refer her for right heart catheterization

A 44-year-old woman comes to the physician because of progressively worsening shortness of breath with exertion and intermittent palpitations over the last 2 months. She has had neither chest pain nor a cough. Her pulse is 124/min and irregular. Physical examination shows a grade 4/6 high-pitched holosystolic murmur that is best heard at the apex and radiates to the back. The murmur increases in intensity when she clenches her hands into fists. The lungs are clear to auscultation. Further evaluation of this patient is most likely to show which of the following findings?

Dilation of left atrium on echocardiogram

Obstruction of the right marginal artery on coronary angiogram

Diffuse ST elevations on electrocardiogram

Reversible area of myocardial ischemia on nuclear stress test

Pulmonary artery thrombus on computed tomography scan

A 63-year-old woman presents to the primary care physician’s clinic complaining of fatigue, diarrhea, headaches, and a loss of appetite. She denies any personal history of blood clots in her past, but she says that her mother has also had to be treated for pulmonary embolism in the recent past. Her past medical history is significant for preeclampsia, hypertension, polycystic ovarian syndrome, and hypercholesterolemia. She currently smokes 1 pack of cigarettes per day, drinks a glass of wine per day, and she currently denies any illicit drug use, although she has a remote past of injection drug use with heroin. The vital signs include: temperature 36.7°C (98.0°F), blood pressure 126/74 mm Hg, heart rate 111/min and irregular, and respiratory rate 17/min. On physical examination, her pulses are bounding and complexion is pale, but breath sounds remain clear. Oxygen saturation was initially 91% on room air and electrocardiogram (ECG) showed atrial fibrillation. Upon further discussion with the patient, her physician discovers that she is having some cognitive difficulty. The laboratory results reveal: mean corpuscular volume (MCV) 111 fL; hemoglobin (Hgb) 9.3 g/dL; methylmalonic acid (MMA) and homocysteine are both elevated. Schilling test is positive. What is the next best step in the management of this patient?

Lifelong Vitamin B12 supplementation

Lifelong folic acid supplementation

Give corticosteroids and iron supplementation

Iron supplementation for 4–6 months

Atrial fibrillation and flutter for USMLE Step 1: High-Yield Internal Medicine Lessons

ECG & Pathophysiology - Chaotic Conduction

Atrial Fibrillation (A-Fib):
- ECG: Irregularly irregular rhythm, no P waves, chaotic fibrillatory (f) waves, narrow QRS.
- Pathophysiology: Multiple ectopic foci near pulmonary vein ostia fire chaotically (>350 bpm), leading to asynchronous atrial contraction & variable AV node conduction.
Atrial Flutter:
- ECG: "Sawtooth" flutter (F) waves (best in II, III, aVF). Atrial rate ~300 bpm. Ventricular rate is a fraction of atrial rate due to AV block (e.g., 2:1, 3:1).
- Pathophysiology: Large re-entrant circuit.

Atrial Fibrillation vs. Atrial Flutter ECG Comparison

⭐ High-Yield: The re-entrant circuit in typical atrial flutter involves the cavo-tricuspid isthmus, a key target for catheter ablation.

Presentation & Workup - Spotting the Signs

Presentation: Palpitations, dyspnea, fatigue, or asymptomatic.
Physical Exam: Irregularly irregular pulse (AFib) or a rapid, regular pulse (AFlutter).

Key Investigations

ECG is diagnostic:
- AFib: No P waves, irregularly irregular R-R intervals, fibrillatory waves.
- AFlutter: Characteristic "sawtooth" flutter waves, especially in leads II, III, aVF.
Labs: Check TSH/T4 (thyrotoxicosis), electrolytes (K+, Mg++), CBC.
Echocardiogram (TTE): Crucial to assess for underlying structural heart disease, valvular function, and chamber size. TEE is better for spotting left atrial appendage thrombus.

⭐ In a young patient without structural heart disease, always ask about triggers like binge drinking ("holiday heart syndrome"), stress, or caffeine.

Acute Management - Taming the Tachycardia

Initial assessment hinges on hemodynamic stability. The primary goal is controlling the rapid ventricular rate (RVR).

Rate Control Agents:
- β-Blockers: Metoprolol, Esmolol.
- Non-DHP CCBs: Diltiazem, Verapamil (Avoid in HFrEF).
- Digoxin: Slower onset; useful in hypotension or HFrEF.
- Amiodarone: Refractory cases or if other agents are contraindicated.
Anticoagulation: Assess stroke risk (CHA₂DS₂-VASc). If AF duration >48h or unknown, anticoagulation is needed before elective cardioversion.

⭐ In patients with Heart Failure with reduced Ejection Fraction (HFrEF), non-dihydropyridine calcium channel blockers (Verapamil, Diltiazem) are contraindicated due to their negative inotropic effects, which can worsen heart failure.

ECG: Atrial fibrillation with rapid ventricular response

Chronic Management - Clots & Control

1. Anticoagulation (Clot Prevention)

Stroke Risk: Assessed via CHA₂DS₂-VASc score to guide therapy.
Action Thresholds:
- Score ≥ 2 (males) or ≥ 3 (females): Anticoagulation indicated.
- Options: Direct Oral Anticoagulants (DOACs) are first-line over Warfarin.
📌 CHA₂DS₂-VASc: CHF, HTN, Age ≥75 (2), Diabetes, Stroke/TIA (2), Vascular dz, Age 65-74, Sex category (Female).

2. Rate & Rhythm Control

Rate Control First:
- Goal: Lenient resting HR < 110 bpm if asymptomatic.
- Agents: β-blockers, non-dihydropyridine CCBs (diltiazem, verapamil).
Rhythm Control:
- Consider for persistent symptoms despite rate control.
- Methods: Cardioversion, antiarrhythmic drugs (amiodarone, flecainide).

⭐ The HAS-BLED score (HTN, Abnormal renal/liver fxn, Stroke, Bleeding history, Labile INRs, Elderly >65, Drugs/alcohol) assesses bleeding risk before starting anticoagulants.

Atrial Fibrillation Management Algorithm

High‑Yield Points - ⚡ Biggest Takeaways

Atrial fibrillation is an irregularly irregular rhythm with no P waves; atrial flutter shows a sawtooth pattern.

The biggest risk is thromboembolism (stroke); use the CHA₂DS₂-VASc score to guide anticoagulation.

Rate control is the initial strategy, most commonly with β-blockers or calcium channel blockers.

Rhythm control (cardioversion, ablation) is reserved for persistent symptoms or hemodynamic instability.

For stroke prevention, direct oral anticoagulants (DOACs) are preferred over warfarin.

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