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cardio.acute-hf.iatrogenic-hypothyroid.v1

Acute HF — Iatrogenic hypothyroid (post-thyroidectomy / post-RAI / over-treated thionamide)

cardiologyacuteadultacuteinpatienttransitionoutpatient
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Phase E variant of cardio.acute-hf.core.v1 — iatrogenic hypothyroid acute HF (post-thyroidectomy / post-RAI for Graves / over-treated hyperthyroid on thionamide / central from pituitary surgery / sunitinib / bexarotene). Distinguished from sibling cardio.acute-hf.thyrotoxicosis.v1 by OPPOSITE thyroid physiology: hormone DEFICIENCY → impaired myocardial relaxation + reduced CO + bradycardia + pericardial effusion + accelerated CAD via hyperlipidemia. Severe form = myxedema coma (mortality 30-60%). Workup specializes TSH (markedly elevated >50 in primary; LOW in central post-pituitary), free T4, cortisol (rule out concurrent adrenal insufficiency in 5-10%), sodium (hyponatremia common), CK (rhabdomyolysis), ECG (bradycardia, low voltage, QT prolongation), echo (pericardial effusion + tamponade screen). Treatment ACUTE: HYDROCORTISONE 100 mg IV q8h FIRST (mandatory before T4; concurrent adrenal insufficiency in 5-10%; T4 without cortisol can precipitate adrenal crisis); LEVOTHYROXINE 200-500 µg IV LOAD (lower 100-200 µg in elderly/CAD/AF) → 50-100 µg IV daily; LIOTHYRONINE T3 5-20 µg IV q8h adjunct controversial in severe; PASSIVE rewarming (avoid active); cautious diuresis (mucinous edema not volume); rate support (atropine, pacing, isoproterenol bridge); DEFER beta-blocker initiation until euthyroid + bradycardia resolved. GDMT 4-pillar deferred until euthyroid trajectory + hemodynamic stability achieved. Manifest pointer reuses cardio.acute-hf.core.v1 manifest. Design-brief pointer reuses parent (iatrogenic-hypothyroid-specific differences documented inline). Status INTEGRATED until terminology + RxNav-validated drug codes are reconciled.

Entry points (5)

  • history
    Post-total or completion thyroidectomy patient presenting with new HF, fatigue, weight gain, cold intolerance, or bradycardia — replacement gap or non-adherence
    post_thyroidectomy_with_replacement_gap
  • history
    Post-RAI ablation for Graves disease (typically 3-12 mo prior) presenting with new HF or myxedema features — predictable iatrogenic hypothyroidism not yet replaced
    post_rai_for_graves_disease_with_new_hf
  • medication
    Patient on methimazole or PTU for hyperthyroid with rapid TSH rise and new HF symptoms — over-treatment / overshoot
    thionamide_overshoot_with_hypothyroid_hf
  • lab_abnormality
    TSH >50 mIU/L + free T4 low + new HF or hemodynamic decompensation — primary iatrogenic hypothyroidism
    tsh_markedly_elevated_with_hf
  • symptom
    Hypothermia + altered mentation + bradycardia + hypotension + hyponatremia in known thyroidectomy/RAI patient — myxedema coma until proven otherwise (mortality 30-60%)
    myxedema_coma_features

Required inputs (14)

  • agerequired
    demographic • used at CONTEXT
    Elderly patients more vulnerable to myxedema coma + require lower starting levothyroxine dose due to CAD/arrhythmia risk
  • thyroid_intervention_history_thyroidectomy_or_rai_or_thionamiderequired
    history • used at CONTEXT
    Identifies iatrogenic trigger: thyroidectomy date, RAI date for Graves, thionamide agent + dose + duration; replacement adherence
  • current_levothyroxine_dose_and_adherencerequired
    medication • used at CONTEXT
    Replacement dose vs ideal weight-based (1.6 µg/kg ideal body weight in adults); adherence; recent dose changes; PPI / iron / calcium interactions impair absorption
  • tshrequired
    lab • used at INITIAL_WORKUP
    TSH primary screen — markedly elevated >50 mIU/L in primary hypothyroid; LOW or inappropriately normal in central hypothyroid (post-pituitary surgery / radiation / sunitinib / bexarotene)
  • free_t4required
    lab • used at INITIAL_WORKUP
    Free T4 confirms biochemical hypothyroid; helps distinguish from sick euthyroid syndrome; trend during treatment
  • cortisol_serum_random_or_acth_stimrequired
    lab • used at INITIAL_WORKUP
    Cortisol to rule out concurrent adrenal insufficiency (5-10% in myxedema coma; thyroid replacement without cortisol can precipitate adrenal crisis); ACTH stim if concerning
  • creatininerequired
    lab • used at CONTEXT
    eGFR for fluid management + medication dosing; rhabdomyolysis can elevate Cr
  • sodium_serumrequired
    lab • used at INITIAL_WORKUP
    Hyponatremia common in severe hypothyroid; impaired free water excretion + SIADH-like mechanism; affects fluid + diuretic strategy
  • ck_totalrequired
    lab • used at INITIAL_WORKUP
    Hypothyroid myopathy + rhabdomyolysis common; CK elevation can be marked
  • lipid_panel
    lab • used at INITIAL_WORKUP
    Hypothyroid hypercholesterolemia accelerates CAD; informs cardiac risk + statin
  • ecg_with_brady_low_voltage_qtrequired
    imaging • used at INITIAL_WORKUP
    ECG: sinus bradycardia, low voltage, prolonged QT, J wave in myxedema; AV block possible
  • echo_with_pericardial_effusion_screenrequired
    imaging • used at INITIAL_WORKUP
    Echo: pericardial effusion common (may be hemodynamically significant), impaired relaxation, possible reduced LVEF in severe; screen for tamponade physiology
  • temperature_corerequired
    vital • used at RED_FLAGS
    Hypothermia is hallmark of myxedema coma; passive rewarming preferred over active
  • sbprequired
    vital • used at RED_FLAGS
    Hypotension in myxedema coma (decreased CO + adrenal insufficiency overlap); guides pressor + cortisol decision

12-phase flow (10)

  1. 1FRAME
    Iatrogenic hypothyroid HF = thyroid hormone deficiency from thyroidectomy / RAI / over-treated thionamide / central pituitary cause; impaired myocardial relaxation + reduced CO + bradycardia + pericardial effusion + hyperlipidemia accelerating CAD; severe form = myxedema coma (mortality 30-60%)
    inputs: thyroid_intervention_history_thyroidectomy_or_rai_or_thionamide, tsh, free_t4
    advance: iatrogenic etiology + biochemical hypothyroid confirmed
  2. 2ENTRY
    Recognition: bradycardia + hypothermia + altered mentation + thyroidectomy/RAI history; STAT TSH + free T4 + cortisol; endocrinology + cardiology activation
    inputs: age, temperature_core
    advance: endocrinology activated for severe cases
  3. 3CONTEXT
    Thyroid intervention timeline (thyroidectomy / RAI date), replacement regimen + adherence + interactions (PPI, iron, calcium, food timing); thionamide dose history; pituitary surgery / radiation / oncologic therapy for central cause; comorbidities (CAD, AF)
    inputs: creatinine, current_levothyroxine_dose_and_adherence
    advance: iatrogenic context complete
  4. 4RED_FLAGS
    Myxedema coma (hypothermia + altered mentation + bradycardia + hypotension + hyponatremia); concurrent adrenal insufficiency (5-10% — precipitate crisis if T4 given before steroid); pericardial tamponade; symptomatic bradycardia / AV block; severe hyponatremia; rhabdomyolysis with renal failure
    inputs: sbp, temperature_core, sodium_serum
    actions: cardiogenic_shock
    advance: red flags screened + steroid + T4 strategy decided
  5. 5INITIAL_WORKUP
    TSH, free T4, free T3 (sick euthyroid distinction), cortisol (random or ACTH stim), ACTH if central, BMP (hyponatremia), CBC (anemia), CK (rhabdomyolysis), LFTs, lipid panel, ABG (hypoventilation in myxedema), ECG (brady, low voltage, QT), echo (pericardial effusion, tamponade screen, LVEF), CXR
    inputs: tsh, free_t4, cortisol_serum_random_or_acth_stim, sodium_serum, ck_total, ecg_with_brady_low_voltage_qt, echo_with_pericardial_effusion_screen
    actions: acute_pulm_edema, panel.cardiac, panel.renal
    advance: workup documented + adrenal status known
  6. 6BRANCHING_WORKUP
    Pituitary MRI if central hypothyroid suspected (low/inappropriate TSH); ACTH stim test if borderline cortisol; pericardiocentesis if tamponade physiology; coronary CT/cath if ischemia suspected (hypothyroid + lipid abnormalities); rule out concomitant ACS confounder; central nervous system imaging if myxedema coma with focal deficits
    actions: acs_pathway
    advance: differential narrowed + adrenal/pituitary workup complete
  7. 7TREATMENT
    STEROID FIRST then T4: hydrocortisone 100 mg IV q8h until adrenal insufficiency excluded (mandatory in myxedema coma; concurrent adrenal insufficiency in 5-10%; T4 without steroid → adrenal crisis). LEVOTHYROXINE 200-500 µg IV LOAD (lower 100-200 µg if elderly, CAD, AF risk) → 50-100 µg IV daily until tolerating PO. LIOTHYRONINE (T3) 5-20 µg IV q8h adjunct controversial — used in severe myxedema coma at some centers. SUPPORTIVE: passive rewarming (avoid active rewarming → vasodilation + hypotension); cautious fluids (hyponatremia + cardiac strain); mechanical ventilation if hypoventilating; standard ADHF management with cautious diuresis (peripheral edema may be mucinous not volume); rate support (atropine, transcutaneous pacing, isoproterenol bridge) if symptomatic bradycardia. ADJUST THIONAMIDE if over-treatment (reduce methimazole / PTU dose). REPLACE adequately post-thyroidectomy (1.6 µg/kg IBW). MONITOR TSH q4-6 weeks during titration.
    inputs: sbp
    actions: protocol.cardiogenic_shock
    advance: steroid + T4 + supportive bundle active + iatrogenic trigger addressed
  8. 8DISPOSITION
    ICU for myxedema coma or hemodynamic instability; cardiology + endocrinology floor if stable; outpatient endocrinology if mild
    advance: unit assigned + endocrinology multidisciplinary plan documented
  9. 9MONITORING
    Continuous telemetry (bradycardia, AV block, QT prolongation), q6h vitals + temperature + mental status, daily BMP (sodium correction not too rapid), daily TSH + free T4 trend (peaks slow over weeks), q6h glucose during hydrocortisone, daily echo if pericardial effusion present, neuro checks q4h in myxedema coma
    inputs: tsh, free_t4, sodium_serum
    actions: panel.cardiac
    advance: monitoring + thyroid replacement titration cadence booked
  10. 10FOLLOWUP
    Endocrinology clinic at 2 weeks then q4-6 weeks during titration; TSH at 4-6 weeks then q3 mo once stable; cardiac follow-up for any persistent dysfunction; address iatrogenic trigger (thionamide dose adjustment, RAI follow-up replacement schedule, post-thyroidectomy lifelong replacement education); lipid management; pituitary follow-up if central hypothyroid
    advance: endocrinology + replacement-titration plan + iatrogenic-trigger-addressed plan documented