Cardiovascular · Year 1 · from Cardiovascular

Case 2: High-Output Heart Failure in Severe Anemia

Patient Presentation

Demographics: 45-year-old female

Chief Complaint: Progressive fatigue and shortness of breath for 2 weeks

History of Present Illness: A 45-year-old female with history of uterine fibroids and heavy menstrual bleeding presents with 2 weeks of progressive fatigue, exertional dyspnea, and palpitations. She reports being able to walk only half a block before becoming short of breath. She has also noticed dizziness when standing and her heart "racing." She has been having heavy periods for 6 months but did not seek care.

Physical Examination:

  • Vital Signs: BP 105/55 mmHg, HR 118 bpm, RR 22/min, SpO2 97% on room air
  • General: Pale, fatigued-appearing female
  • Cardiovascular:
  • Hyperdynamic precordium
  • Grade 2/6 systolic flow murmur at LUSB
  • Bounding pulses
  • S3 gallop
  • JVP mildly elevated
  • Lungs: Bibasilar crackles
  • Extremities: Warm, trace edema
  • Conjunctivae: Markedly pale

Workup

  • Labs:
  • Hemoglobin: 4.2 g/dL (severely reduced)
  • MCV: 68 fL (microcytic)
  • Iron: 15 μg/dL, Ferritin: 5 ng/mL, TIBC: 450 μg/dL (iron deficiency)
  • Reticulocyte count: 0.5% (inappropriately low)
  • BNP: 650 pg/mL
  • ECG: Sinus tachycardia, nonspecific ST-T changes
  • Echocardiogram:
  • Hyperdynamic LV function (EF 70%)
  • Mildly dilated LV
  • Elevated cardiac output estimated at 9 L/min
  • Mild tricuspid regurgitation

Diagnosis

High-output heart failure secondary to severe iron deficiency anemia

Cardiac Output Correlation: Oxygen Delivery = Cardiac Output × Oxygen Content

In severe anemia:

  • Oxygen content reduced: Hgb 4.2 g/dL severely limits oxygen-carrying capacity
  • Compensatory increase in CO: Heart increases output to maintain tissue oxygen delivery
  • Mechanisms of increased CO:
  • Tachycardia (HR 118) increases CO
  • Decreased blood viscosity reduces SVR (afterload)
  • Increased preload from fluid retention
  • Enhanced contractility (sympathetic activation)
  • Hyperdynamic circulation: Bounding pulses, flow murmur, warm extremities

Why heart failure develops: Despite high CO, the heart cannot sustain the increased workload indefinitely → eventually leads to volume overload and heart failure symptoms (dyspnea, edema, S3 gallop).

High-output HF causes: Anemia, thyrotoxicosis, AV fistula, beriberi, Paget's disease

Treatment

  1. Blood transfusion: Slow transfusion of packed RBCs (risk of volume overload)
  • Transfuse 1 unit at a time with diuretic coverage
  1. IV furosemide: Prevent/treat volume overload during transfusion
  2. Iron supplementation: IV iron preferred for severe deficiency
  3. Treat underlying cause: Gynecology referral for fibroid management
  4. Monitor for transfusion reactions
  5. Heart failure should resolve with correction of anemia

Clinical Image

Image Description: Peripheral blood smear showing microcytic, hypochromic red blood cells characteristic of iron deficiency anemia. The RBCs appear pale with increased central pallor and are smaller than normal.

Source: Wikimedia Commons - Iron deficiency anemia blood smear License: CC BY-SA 3.0 URL: https://commons.wikimedia.org/wiki/File:Iron_deficiency_anemia_blood_smear.jpg

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