Subinternship Medicine · Year 4 · from Subinternship Medicine

Case 2: Atrial Fibrillation with Rapid Ventricular Response and Supervision-Seeking

Clinical Presentation

Patient Demographics: 72-year-old female

Chief Complaint: "My heart is racing and I feel weak"

History of Present Illness: Mrs. Garcia is a 72-year-old female with a history of heart failure with preserved ejection fraction (HFpEF), hypertension, and chronic kidney disease stage 3 who presents with 2 days of palpitations, fatigue, and mild dyspnea on exertion. She notes she has not been taking her medications consistently over the past week due to running out of prescriptions. She denies chest pain, syncope, or lower extremity swelling.

Past Medical History:

  • HFpEF (EF 55%)
  • Hypertension
  • CKD stage 3 (baseline creatinine 1.5 mg/dL)
  • Hypothyroidism
  • Osteoarthritis

Medications (when compliant):

  • Metoprolol succinate 50 mg daily
  • Losartan 50 mg daily
  • Furosemide 20 mg daily
  • Levothyroxine 75 mcg daily
  • Acetaminophen PRN

Physical Examination:

  • Vital Signs: Temperature 37.0C, HR 142 bpm (irregular), BP 156/92 mmHg, RR 18/min, SpO2 96% on room air
  • General: Elderly female, appears fatigued but in no acute distress
  • Cardiovascular: Irregularly irregular rhythm, tachycardic, no murmurs, JVP 10 cm H2O
  • Lungs: Clear to auscultation bilaterally
  • Abdomen: Soft, non-tender
  • Extremities: Trace bilateral ankle edema

Inpatient Workup

Laboratory Studies:

  • WBC 7,200/uL
  • Hemoglobin 11.8 g/dL
  • BUN 32 mg/dL, Creatinine 1.7 mg/dL
  • TSH 6.8 mIU/L (elevated)
  • BNP 420 pg/mL
  • Troponin I < 0.01 ng/mL (x2, 6 hours apart)
  • Magnesium 1.6 mEq/L, Potassium 3.8 mEq/L

Imaging:

  • ECG: Atrial fibrillation with rapid ventricular response (rate 138), no ST changes
  • Chest X-ray: Mild cardiomegaly, no pulmonary edema
  • Echocardiogram: EF 50-55%, mild left atrial enlargement, no significant valvular disease

Diagnosis

Primary Diagnosis: Atrial fibrillation with rapid ventricular response, new onset vs. paroxysmal

Secondary Diagnoses:

  • Heart failure with preserved ejection fraction (compensated)
  • Subclinical hypothyroidism (contributing factor)
  • Chronic kidney disease stage 3 with mild acute worsening

Treatment Plan

Immediate Management:

  1. Admit to telemetry for cardiac monitoring
  2. Rate control: Metoprolol IV 5 mg, then restart metoprolol succinate 50 mg daily
  3. Replete magnesium (2g IV)
  4. Anticoagulation assessment: CHA2DS2-VASc score = 5 (age, female, HTN, HF) - initiate anticoagulation
  5. Apixaban 5 mg BID (dose-adjusted for age and renal function)
  6. Resume home medications with adjustment of levothyroxine
  7. Gentle diuresis if symptoms of congestion

Sub-Intern Learning Points: This case demonstrates critical supervision-seeking behaviors:

  1. When to Staff: New arrhythmia requiring anticoagulation decision - staff before initiating
  2. Presenting Plans: "My assessment is new atrial fibrillation likely triggered by medication non-adherence and thyroid dysfunction. I'd like to rate control with IV metoprolol, replete electrolytes, and discuss anticoagulation with you given her CHA2DS2-VASc score of 5."
  3. Recognizing Complexity: Multiple comorbidities affecting drug choices (CKD affecting DOAC dosing)
  4. Building Autonomy: Calculating risk scores independently, then confirming with the team

Clinical Image

Image Description: 12-lead electrocardiogram demonstrating atrial fibrillation with rapid ventricular response, showing an irregularly irregular rhythm without discrete P waves.

Image Source: Wikimedia Commons - "Atrial fibrillation ECG"

  • URL: https://commons.wikimedia.org/wiki/File:Atrial_fibrillation_-_ECG.png
  • License: Public Domain
  • Author: CardioNetworks

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