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cardio.cardiogenic-shock.giant-cell-myocarditis.v1

Cardiogenic shock — giant cell myocarditis (GCM)

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Phase E variant of cardio.cardiogenic-shock.core.v1 — narrowed to idiopathic giant cell myocarditis (GCM) with cardiogenic shock per Cooper Multicenter GCM Registry NEJM 1997 (PMID 9197214) + GIANT-2 trial protocol (PMID 18369191) + Kandolin Finland Registry 2013 + Ekström 2024 transplant outcomes. Rare (incidence ~0.5-1 per million per year) but devastating: ~70% mortality at 1 year WITHOUT immunosuppression vs ~30-50% at 1 year WITH combined immunosuppression. Hallmarks: (1) acute / subacute heart failure progressing rapidly to CS in previously healthy young-to-middle-aged adult; (2) REFRACTORY VENTRICULAR ARRHYTHMIAS (sustained VT/VF storm, 50-60% of cases — distinct from most other myocarditis); (3) HIGH-GRADE AV BLOCK (15-50%, major diagnostic clue distinguishing GCM from viral); (4) ~20% autoimmune association (thymoma, IBD, autoimmune thyroid). Diagnosis: ENDOMYOCARDIAL BIOPSY GOLD STANDARD per AHA/ACC/ESC 2007 EMB consensus (Cooper PMID 17998456) — Class IIa for unexplained new-onset HF <2 wks with hemodynamic compromise + ventricular arrhythmia or AV block; histology: multinucleated giant cells (CD68+, S-100−) + lymphocyte infiltrate (T-cell predominant) + myocyte necrosis WITHOUT non-caseating granulomas (differentiates from cardiac sarcoidosis per Birnie HRS 2014 PMID 24682272). CMR Lake Louise 2018 (Ferreira PMID 30025572) + cMR-PET / FDG-PET for metabolic activity + chest CT for sarcoidosis lymphadenopathy + thymoma screen. Treatment ACUTE: standard CS support (NE first-line per SOAP-II PMID 20200382); inotropes CAUTIOUS — sustained VT/VF storm is the rule; escalate to MCS (IABP / Impella / VA-ECMO) over higher inotropes per ELSO 2020 ECMO myocarditis registry (60-70% survival to discharge) + DanGer Shock 2024 PMID 38587234 precedent. COMBINED IMMUNOSUPPRESSION per Cooper GIANT-2 protocol (PMID 18369191): (1) methylprednisolone 1g IV daily × 3-5 d → prednisone 1 mg/kg/d taper; (2) cyclosporine 3-5 mg/kg/d divided BID, trough 200-300 ng/mL acute then 100-200 maintenance; (3) IL-2 receptor antagonist basiliximab 20 mg IV day 0 + day 4 induction; (4) anti-T-cell rabbit ATG 1.5 mg/kg/d × 5-14 d (replaces historical OKT3 / muromonab no longer manufactured); (5) chronic maintenance with azathioprine 1-2 mg/kg/d or mycophenolate 1000 mg BID. Combined immunosuppression markedly improves transplant-free survival from ~10% to ~70%. Refractory VT/VF storm: amiodarone IV; lidocaine alternative; magnesium repletion; consider catheter ablation; transplant escalation. High-grade AV block: transvenous pacemaker → permanent pacemaker (often biventricular if HFrEF). Most GCM patients eligible for ICD post-acute phase per AHA 2017 VA/SCD guideline given high arrhythmic recurrence risk. TRANSPLANT LISTING: UNOS 1A priority (MCS-dependent OR refractory VT/VF on optimal therapy); GCM has HIGH RECURRENCE in graft (20-25% per Kandolin 2013 + Ekström 2024) but transplant remains BEST OPTION given dismal medical mortality; post-transplant immunosuppression maintained with surveillance EMB for graft GCM recurrence. OPPORTUNISTIC INFECTION PROPHYLAXIS required given high-intensity immunosuppression: PJP (TMP-SMX or atovaquone), CMV (valganciclovir per serostatus), antifungal per neutropenia; live vaccines CONTRAINDICATED lifelong on immunosuppression; AVOID NSAIDs lifelong per ESC 2013. Inherits parent CS framework; specialises for idiopathic GCM with EMB diagnostic gateway, combined immunosuppression per GIANT-2, transplant listing priority, lifelong immunosuppression maintenance, ICD pathway, and graft GCM recurrence surveillance. Status INTEGRATED until terminology + RxNav-validated drug codes are reconciled. Authored 2026-05-15 by shard-06-cardio-acute as Phase E wave 14 etiology variant.

Entry points (5)

  • symptom
    Previously healthy young-to-middle-aged adult with rapid (days-to-weeks) progression of acute HF to cardiogenic shock — high suspicion for GCM, especially if associated with VT/VF storm or AV block
    rapid_progression_acute_hf_to_shock_in_young_healthy_adult
  • symptom
    Sustained VT/VF storm (≥3 episodes in 24 h) in setting of acute myocarditis — GCM until proven otherwise (50-60% of GCM cases per Cooper 1997 + Kandolin 2013); emergent EMB indication
    sustained_vt_vf_storm_in_acute_myocarditis
  • symptom
    New high-grade AV block (Mobitz II / complete heart block) in acute myocarditis — GCM is the leading clue (15-50% per Kandolin 2013); emergent EMB indication
    high_grade_av_block_in_acute_myocarditis
  • imaging
    Endomyocardial biopsy showing multinucleated giant cells (CD68+, S-100−) + lymphocyte infiltrate (T-cell predominant) + myocyte necrosis WITHOUT non-caseating granulomas (differential vs sarcoidosis) — diagnostic GCM
    emb_giant_cells_multinucleated
  • history
    Known autoimmune disease (thymoma, IBD, autoimmune thyroid) presenting with acute severe HF — GCM association in ~20% per Cooper 1997
    autoimmune_disease_with_acute_severe_hf

Required inputs (18)

  • agerequired
    demographic • used at CONTEXT
    GCM mean age ~42-43 yo per Cooper 1997 + Kandolin 2013; younger than typical AMI-CS; informs prognosis + transplant candidacy
  • sbprequired
    vital • used at RED_FLAGS
    SCAI 2022 staging baseline; gates vasopressor escalation
  • hrrequired
    vital • used at CONTEXT
    Sustained VT/VF storm + AV block both common in GCM; informs telemetry and arrhythmia management
  • troponinrequired
    lab • used at INITIAL_WORKUP
    Markedly elevated typical; persistent elevation reflects ongoing myocyte injury despite immunosuppression
  • bnp_ntprobnprequired
    lab • used at INITIAL_WORKUP
    Acute HF marker; trend tracks LV recovery on combined immunosuppression
  • lactaterequired
    lab • used at RISK_STRATIFICATION
    SCAI 2022 staging + CardShock prognostication (Harjola EHJ 2015 PMID 26333869)
  • creatininerequired
    lab • used at CONTEXT
    End-organ damage marker + cyclosporine renal dose adjustment + gadolinium contrast safety for CMR
  • cbc_with_diffrequired
    lab • used at INITIAL_WORKUP
    Baseline cytopenias + ATG / cyclosporine + steroid bone marrow surveillance
  • lftrequired
    lab • used at INITIAL_WORKUP
    Cyclosporine + ATG hepatotoxicity surveillance; baseline before immunosuppression
  • tsh
    lab • used at BRANCHING_WORKUP
    Autoimmune thyroid disease association with GCM (Cooper 1997)
  • ana
    lab • used at BRANCHING_WORKUP
    Autoimmune disease screen; thymoma association
  • echorequired
    imaging • used at INITIAL_WORKUP
    Biventricular dysfunction; effusion screen; no regional wall motion crossing single coronary territory
  • ecgrequired
    imaging • used at INITIAL_WORKUP
    AV block (15-50% of GCM cases) — high diagnostic value; diffuse ST/T-wave changes
  • cor_angiorequired
    imaging • used at BRANCHING_WORKUP
    Mandatory rule-out of obstructive CAD (myocarditis is an MI mimic); typically clean coronaries in GCM
  • cmrrequired
    imaging • used at BRANCHING_WORKUP
    Lake Louise Criteria 2018 (Ferreira PMID 30025572); patchy or extensive transmural LGE possible in GCM
  • fdg_pet_or_cmr_pet
    imaging • used at BRANCHING_WORKUP
    Metabolic activity assessment; differential vs cardiac sarcoidosis (Birnie HRS 2014 PMID 24682272)
  • chest_ctrequired
    imaging • used at BRANCHING_WORKUP
    Hilar / mediastinal lymphadenopathy screen for sarcoidosis differential; thymoma screen for paraneoplastic GCM
  • endomyocardial_biopsyrequired
    imaging • used at BRANCHING_WORKUP
    GOLD STANDARD per AHA/ACC/ESC 2007 EMB consensus (Cooper PMID 17998456) — Class IIa for unexplained new-onset HF <2 wks with hemodynamic compromise + ventricular arrhythmia or AV block; multinucleated giant cells + lymphocyte infiltrate + myocyte necrosis WITHOUT non-caseating granulomas (vs sarcoidosis)

12-phase flow (11)

  1. 1FRAME
    Suspect GCM in previously healthy young-to-middle-aged adult with rapid progression of acute HF to CS, especially with sustained VT/VF storm or new high-grade AV block; EMB is the gateway diagnostic — multidisciplinary alignment for emergent biopsy
    inputs: echo, ecg, cor_angio
    advance: GCM clinical suspicion stated and EMB pathway engaged
  2. 2ENTRY
    CS team activation; emergency cath to exclude obstructive CAD; echo for biventricular function + effusion; mobilize MCS team early — GCM almost always requires MCS bridge to immunosuppression response, recovery, or transplant
    inputs: sbp, lactate
    advance: CS team activated + obstructive CAD excluded + MCS team aware + EMB pathway engaged
  3. 3CONTEXT
    Prior autoimmune disease (thymoma, IBD, autoimmune thyroid), recent infection, drug exposure, oncology history; arrhythmia and AV block history; pacemaker / ICD history; transplant candidacy assessment criteria
    inputs: age, hr, creatinine, cbc_with_diff, lft
    advance: Context complete and sarcoidosis vs GCM working differential stated
  4. 4RED_FLAGS
    Sustained VT/VF storm (50-60% of GCM cases — distinct from most viral); high-grade AV block (15-50%); refractory shock requiring MCS escalation; transplant listing criteria met
    inputs: sbp, hr
    actions: cardiogenic_shock, cardiac_tamponade
    advance: Arrhythmia + AV block screened; MCS pathway engaged if needed; transplant evaluation initiated
  5. 5INITIAL_WORKUP
    ECG (AV block, diffuse ST/T-wave changes), echo (biventricular dysfunction, effusion), troponin, BNP, BMP, lactate, CBC w/ diff, LFT, TSH; serial telemetry; SCAI 2022 staging
    inputs: ecg, echo, troponin, bnp_ntprobnp, lactate, cbc_with_diff, lft
    actions: cardiogenic_shock, panel.cardiac, panel.renal, panel.abg, panel.cbc
    advance: Workup complete and SCAI stage assigned
  6. 6BRANCHING_WORKUP
    EMERGENT ENDOMYOCARDIAL BIOPSY — diagnostic gateway; cardiac MRI (Lake Louise 2018) when stable; FDG-PET / cMR-PET if available for metabolic assessment + sarcoidosis differential; chest CT for sarcoidosis lymphadenopathy + thymoma screen; ANA + autoimmune workup; viral PCR (rule out viral co-existence)
    inputs: cor_angio, cmr, chest_ct, endomyocardial_biopsy
    advance: EMB sent and processed; CMR + chest CT documented
  7. 7RISK_STRATIFICATION
    SCAI 2022 staging; CardShock prognostication; GCM transplant-free survival ~70% at 1 year WITH combined immunosuppression vs ~10% WITHOUT per Cooper 1997 + Kandolin 2013; transplant recurrence rate 20-25% per Kandolin 2013 + Ekström 2024 — but transplant remains best option given dismal medical mortality
    inputs: sbp, lactate, troponin
    advance: Risk stratified, transplant candidacy assessed, immunosuppression eligibility confirmed
  8. 8TREATMENT
    Standard CS support (NE first-line per SOAP-II); inotropes CAUTIOUS in inflamed myocardium with VT/VF storm — escalate to MCS rather than higher inotropes; COMBINED IMMUNOSUPPRESSION per Cooper GIANT-2 protocol — methylprednisolone 1g IV daily + cyclosporine 3-5 mg/kg/d (trough 200-300 ng/mL) + IL-2 receptor antagonist (basiliximab) + ATG (rabbit anti-thymocyte globulin) induction; chronic maintenance with cyclosporine + low-dose steroids + azathioprine or mycophenolate; transplant LISTING priority (UNOS 1A); high-grade AV block → transvenous pacemaker → permanent pacemaker (often biventricular)
    inputs: sbp, lactate
    actions: cardiogenic_shock
    advance: Combined immunosuppression started + MCS plan documented + transplant listed if eligible
  9. 9DISPOSITION
    CICU at MCS-capable + TRANSPLANT-CAPABLE center (UNOS 1A listing); advanced HF + transplant team activation; arrhythmia management with EP
    advance: Disposition assigned with MDT mobilised (cards, IC, advanced HF, transplant, EP, transplant immunology)
  10. 10MONITORING
    A-line, central line, lactate clearance, urine output; continuous telemetry (high VT/VF risk); serial echo q24h for LV recovery; daily troponin and BNP; cyclosporine trough q24h to maintain 200-300 ng/mL acute then 100-200 ng/mL maintenance; daily CBC + LFT for immunosuppression toxicity; opportunistic infection surveillance (CMV, PJP prophylaxis)
    inputs: lactate, troponin
    actions: panel.cardiac, panel.renal
    advance: Monitoring cadence set + immunosuppression trough plan documented
  11. 11FOLLOWUP
    Repeat echo + CMR at 4-8 wks; continued combined immunosuppression LIFE-LONG OR until transplant; transplant evaluation completion if not yet listed; cardiac rehab; EP follow-up for ICD eligibility per AHA 2017 VA/SCD guideline (high arrhythmic recurrence — most GCM patients receive ICD after acute phase); post-transplant immunosuppression maintained with surveillance for graft GCM recurrence (20-25% per Kandolin 2013 + Ekström 2024)
    advance: Recovery echo, CMR, continued immunosuppression, transplant evaluation, ICD pathway booked