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cardio.nstemi.hcm-microvascular.v1

NSTEMI in hypertrophic cardiomyopathy — microvascular ischemia + supply-demand mismatch

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Phase E variant of cardio.nstemi.core.v1 — non-atherosclerotic NSTEMI in hypertrophic cardiomyopathy patients driven by microvascular ischemia + supply-demand mismatch. Substrate: intramural coronary arteriolar dysplasia + perfusion mismatch in hypertrophied septum + SAM-mediated LVOT obstruction. Coronary angiography typically unobstructed at epicardial level. Diagnostic anchor: stress CMR with first-pass perfusion + LGE is the gold-standard test (Petersen 2007 PMID 17502574); perfusion defects + mid-wall LGE in hypertrophied septum confirm HCM-microvascular MI substrate. PET-CT MBFR <2.0 = severe MVD. OVERRIDES parent: vasodilator avoidance (NTG/ACEi/ARB/ARNI/DHP-CCB drop afterload → worsen LVOT gradient → worsen microvascular ischemia); inotrope avoidance (dobutamine/milrinone/epinephrine worsen SAM); DAPT non-routine (no plaque rupture; ASA monotherapy reasonable; reserve P2Y12 only if concurrent atherosclerotic CAD on imaging); statin only-if-ASCVD; HCM-specific disease-modifying therapy ladder (BB/CCB → disopyramide → mavacamten → septal reduction therapy per ACC/AHA 2024 HCM). Acute hemodynamics: fluids + phenylephrine + esmolol (HCM-specific paradigm; never inotropes). Long-term: SCD risk stratification per ESC 2014 HCM-RISK-SCD + ACC/AHA 2024 modifiers (LGE >15%, family history SCD, syncope, NSVT, apical aneurysm, LV thickness ≥30 mm); cascade family screening (50% autosomal dominant); ICD primary prevention; AC for ANY AF Class I regardless of CHA2DS2-VASc. Sister-differentiated from cardio.acute-hf.hcm-decompensation.v1 (heart-failure presentation — same physiology, different presenting syndrome) and cardio.nstemi.minoca.v1 (broader MINOCA umbrella — HCM-microvascular MI is one MVD subtype routed here when HCM substrate identified). Manifest pointer reuses cardio.nstemi.core.v1 manifest. Design-brief pointer reuses parent. Status INTEGRATED until terminology + RxNav-validated drug codes are reconciled. Authored 2026-05-15 by shard-06-cardio-acute Phase E wave 25.

Entry points (6)

  • history
    Patient with known hypertrophic cardiomyopathy (resting or provocable LVOT gradient ≥30 mmHg, septal thickness ≥15 mm) presenting with ischemic chest pain + hsTn rise/fall + non-ST-elevation ECG — microvascular ischemia / supply-demand crisis on differential
    known_hcm_with_nstemi_pattern
  • imaging
    NSTE-ACS workup angiogram shows unobstructed epicardial coronaries + bedside echo reveals asymmetric septal hypertrophy (≥15 mm) with SAM and dynamic LVOT gradient → HCM-microvascular NSTEMI substrate
    angio_unobstructed_with_lv_hypertrophy_on_echo
  • imaging
    Stress CMR shows first-pass perfusion defect + mid-wall LGE in hypertrophied septum + unobstructed epicardial coronaries — confirms HCM-microvascular MI substrate per Petersen 2007 PMID 17502574
    cmr_first_pass_perfusion_defect_no_obstructive_cad
  • symptom
    New-onset AFib with rapid ventricular response in HCM patient + hsTn rise/fall + non-ST-elevation ECG — loss of atrial kick destabilizes LV filling → subendocardial ischemia / supply-demand mismatch in stiff hypertrophied LV
    new_afib_in_hcm_with_troponin_rise
  • history
    HCM patient with precipitant (GI losses, sepsis, fever, postoperative volume shift, diuretic over-shoot) + ischemic chest pain + hsTn rise — supply-demand crisis triggered by hypovolemia / tachycardia worsening LVOT obstruction
    hcm_with_volume_contraction_or_fever_precipitant
  • lab_abnormality
    hsTn rise/fall + ECG with LVH voltage criteria + lateral T-wave inversion + abnormal Q-waves in patient without conventional ASCVD risk factors → HCM screen with TTE + family history
    troponin_rise_with_lvh_pattern_on_ecg_no_classic_acs_risk

Required inputs (18)

  • agerequired
    demographic • used at CONTEXT
    HCM-microvascular NSTEMI spans wide age range; younger patients more likely to have genetic HCM (sarcomeric mutation); older patients may have HCM phenocopies (TTR amyloid, hypertensive HD); informs SCD risk + cascade screening
  • known_hcm_diagnosis_and_phenotyperequired
    history • used at CONTEXT
    Pre-existing HCM diagnosis with documented LVOT gradient + LV thickness pattern (asymmetric septal vs apical vs concentric) + family history drives diagnostic confidence and immediate management; recent echo + CMR results critical
  • family_history_scd_or_hcmrequired
    history • used at CONTEXT
    ESC HCM-RISK-SCD component + ACC/AHA 2024 SCD risk stratification; cascade family screening referral (50% autosomal dominant inheritance); informs ICD primary-prevention decision
  • unexplained_syncope_historyrequired
    history • used at RISK_STRATIFICATION
    Major SCD risk modifier in HCM (ESC 2014; ACC/AHA 2024); unexplained syncope shifts ICD decision toward primary prevention regardless of HCM-RISK-SCD score
  • current_medsrequired
    history • used at CONTEXT
    Detect inadvertent vasodilators (ACEi, ARB, ARNI, NTG, nitrates, DHP-CCB amlodipine), inotropes (rare outpatient), or aggressive diuretics that may have precipitated LVOT obstruction crisis with supply-demand mismatch; need to stop or switch immediately
  • sbprequired
    vital • used at RED_FLAGS
    Hypotension in HCM-microvascular NSTEMI = SAM-mediated LVOT obstruction crisis with supply-demand mismatch — treat with FLUIDS + phenylephrine + esmolol, NOT inotropes or vasodilators; SBP <90 triggers HCM-specific obstruction-crisis pathway
  • hrrequired
    vital • used at RED_FLAGS
    Tachycardia worsens LVOT gradient by shortening diastolic filling AND raises myocardial O2 demand → worsens supply-demand mismatch; HR target <80 with esmolol IV → metoprolol succinate / carvedilol PO; new AFib RVR requires emergent rate control or cardioversion
  • spo2required
    vital • used at RED_FLAGS
    Pulmonary edema secondary to acute diastolic dysfunction + SAM-driven mitral regurgitation precipitating subendocardial ischemia; SpO2 <92% triggers cautious NIPPV (avoid pre-load drop)
  • ecg_serialrequired
    imaging • used at INITIAL_WORKUP
    Confirms NSTE-ACS pattern (T-wave inversion, dynamic ST depression, new BBB) + characterizes baseline HCM ECG (LVH voltage, lateral T-wave inversion, abnormal Q-waves); detects new AFib or VT/VF
  • hs_troponin_serialrequired
    lab • used at INITIAL_WORKUP
    Defines NSTEMI per 4th UDMI (PMID 30153967) rise/fall criteria; chronic mild troponin elevation common in HCM (microvascular dysfunction baseline) — ACUTE rise/fall above baseline drives NSTEMI label
  • creatinine_egfrrequired
    lab • used at INITIAL_WORKUP
    eGFR for contrast load at cath / CMR gadolinium (avoid if eGFR <30); apixaban dosing if AF (2.5 mg BID per FDA criteria); disopyramide renal-adjustment; KDIGO 2021 race-free baseline
  • cbcrequired
    lab • used at INITIAL_WORKUP
    Baseline before any antiplatelet / AC; rules out anemia mimic for ischemia (anemia in HCM worsens supply-demand mismatch dramatically due to high O2 demand from hypertrophied myocardium)
  • potassiumrequired
    lab • used at CONTEXT
    HypoK in stiff hypertrophied LV worsens VT/VF risk; also affects disopyramide proarrhythmia (QT prolongation); replete K to ≥4.0
  • magnesium
    lab • used at CONTEXT
    HypoMg ↑ TdP risk on disopyramide (QT prolongation); maintain Mg ≥2.0
  • echo_lvot_gradient_and_samrequired
    imaging • used at INITIAL_WORKUP
    Bedside or formal TTE — resting + provocable LVOT gradient (Valsalva, squat-to-stand), SAM, septal thickness, LVEF, mitral regurgitation severity — drives ALL drug decisions and management strategy
  • cor_angio_to_exclude_obstructive_cadrequired
    imaging • used at INITIAL_WORKUP
    Coronary angiography typically UNOBSTRUCTED at epicardial level (HCM-microvascular substrate by definition); if focal lesion identified, dual aetiology (HCM + atherosclerotic NSTEMI) may apply; IVUS/OCT can detect microvascular dysfunction signs
  • stress_cmr_perfusion_lgerequired
    imaging • used at BRANCHING_WORKUP
    Stress CMR with first-pass perfusion + late gadolinium enhancement (LGE) — gold-standard test for microvascular dysfunction in HCM per Petersen 2007 PMID 17502574; perfusion defects + mid-wall LGE in hypertrophied septum confirm HCM-microvascular MI substrate
  • cha2ds2_vasc_factorsrequired
    history • used at RISK_STRATIFICATION
    AF stroke risk if AF detected — but in HCM, ANY AF = AC regardless of CHA2DS2-VASc score per ACC/AHA 2024 HCM Class I (atrial myopathy + LA enlargement drive elevated stroke risk); calculator used for documentation

12-phase flow (12)

  1. 1FRAME
    NSTEMI in HCM = microvascular ischemia + supply-demand mismatch (NOT atherosclerotic plaque rupture) driven by SAM-mediated LVOT obstruction + intramural arteriolar dysplasia + perfusion mismatch in hypertrophied septum; coronary angio typically unobstructed; treatment paradox vs atherosclerotic NSTEMI: AVOID NTG/ACEi/ARB/ARNI/DHP-CCB/aggressive diuretics/inotropes — TREAT the HCM physiology with BB or non-DHP CCB → disopyramide → mavacamten → septal reduction therapy
    inputs: known_hcm_diagnosis_and_phenotype, echo_lvot_gradient_and_sam
    advance: HCM-microvascular paradigm framed before any drug ordered
  2. 2ENTRY
    Recognize HCM patient (known or newly suspected from ECG LVH + asymmetric septal hypertrophy on echo) presenting with NSTE-ACS pattern; activate cath lab for diagnostic angio AND obtain bedside echo for LVOT gradient + SAM + LVEF; emergent cardiology consult
    inputs: age, known_hcm_diagnosis_and_phenotype
    actions: acs_pathway
    advance: HCM substrate confirmed + cath lab activated for unobstructed-coronary cause-finding
  3. 3CONTEXT
    Family history SCD or HCM (cascade screening trigger), prior HCM workup (CMR LGE, Holter NSVT, genetic testing, mavacamten exposure history), current chronic regimen (BB, CCB, disopyramide, mavacamten), home meds review for inadvertent vasodilators / inotropes / aggressive diuretics that precipitated obstruction crisis
    inputs: family_history_scd_or_hcm, current_meds, creatinine_egfr, cbc, potassium, hr
    advance: context complete + precipitant identified
  4. 4RED_FLAGS
    SAM-mediated LVOT obstruction crisis with supply-demand mismatch (SBP <90 + worsening gradient — give fluids + phenylephrine + esmolol, NEVER inotropes); new AFib with RVR (emergent rate control / cardioversion + Class I AC regardless of CHA2DS2-VASc); ventricular arrhythmia / SCD; aortic dissection mimic must be ruled out before any heparin (CT-A if any concern); refractory pulmonary edema from SAM-driven MR (cautious NIPPV — avoid pre-load drop)
    inputs: sbp, hr, spo2
    actions: cardiogenic_shock, chest_pain
    advance: red flags screened + obstruction-crisis pathway initiated if needed
  5. 5INITIAL_WORKUP
    ECG + serial hsTn + BMP + Mg + CBC + CXR + bedside TTE with LVOT gradient (resting + Valsalva) + SAM + LVEF + MR severity; cath to exclude obstructive CAD (typically unobstructed); intracoronary imaging if any focal lesion identified
    inputs: ecg_serial, hs_troponin_serial, creatinine_egfr, cbc, echo_lvot_gradient_and_sam, cor_angio_to_exclude_obstructive_cad
    actions: acs_pathway, panel.cardiac, panel.renal, panel.cbc
    advance: workup documented + epicardial obstruction excluded + LVOT gradient quantified
  6. 6BRANCHING_WORKUP
    Stress CMR with first-pass perfusion + LGE (cornerstone for HCM-microvascular MI substrate per Petersen 2007 PMID 17502574); PET-CT MBFR if available (severe MVD if MBFR <2.0); identify precipitant (sepsis bundle if applicable, AFib rate/rhythm); HOCM provocative testing at bedside (Valsalva for gradient unmasking)
    inputs: stress_cmr_perfusion_lge, creatinine_egfr
    advance: HCM-microvascular MVO confirmed + precipitant identified or empirical management initiated
  7. 7DIFFERENTIAL
    HCM-microvascular NSTEMI vs atherosclerotic NSTEMI (concurrent epicardial CAD on cath) vs vasospastic angina (Prinzmetal) vs broader MINOCA umbrella vs takotsubo overlap (apical ballooning + recent stressor) vs aortic dissection mimic vs HCM phenocopies (TTR amyloid, Fabry, Danon, hypertensive HD)
    inputs: echo_lvot_gradient_and_sam, stress_cmr_perfusion_lge
    advance: HCM-microvascular substrate label committed
  8. 8RISK_STRATIFICATION
    TIMI / GRACE / HEART scores LESS validated in HCM-microvascular NSTEMI — atypical demographics undervalue risk; CMR LGE burden + LVOT gradient + LVEF are dominant prognostic inputs; ESC 2014 HCM-RISK-SCD 5-year score (driver for primary-prevention ICD); ACC/AHA 2024 multi-modality SCD refinement; CHA2DS2-VASc inapplicable for stroke (ANY AF in HCM = Class I AC); SCAI staging if shock complicates
    inputs: family_history_scd_or_hcm, unexplained_syncope_history, cha2ds2_vasc_factors, sbp, hr, creatinine_egfr
    actions: calc.heart, calc.cha2ds2vasc
    advance: risk band documented + ICD + AC decisions made
  9. 9TREATMENT
    ACUTE: fluids 250-500 mL crystalloid bolus, phenylephrine 50-200 mcg IV bolus or 0.5-3 mcg/kg/min infusion for hypotension, esmolol 50-300 mcg/kg/min IV titrate to HR <80, AC if AFib (apixaban Class I per ACC/AHA 2024 HCM regardless of CHA2DS2-VASc), electrical cardioversion if hemodynamically unstable AFib. AVOID dobutamine/milrinone/epinephrine, AVOID NTG/ACEi/ARB/ARNI, AVOID DHP-CCB amlodipine, AVOID aggressive diuresis (cautious if frank pulmonary edema). CHRONIC: BB (carvedilol/metoprolol succinate) or non-DHP CCB (verapamil/diltiazem) at maximally tolerated dose; disopyramide if symptomatic refractory obstruction (Class IIa); mavacamten REMS enrollment if persistent symptomatic HOCM (Class IIa); septal reduction therapy referral (surgical myectomy gold standard or alcohol septal ablation) for refractory NYHA III-IV + LVOT gradient ≥50 mmHg (Class I); ICD evaluation per SCD criteria. ASA monotherapy reasonable (no plaque rupture); DAPT NOT routine (reserve P2Y12 only if concurrent atherosclerotic CAD); statin only if concomitant ASCVD or guideline-meeting LDL
    inputs: sbp, hr, creatinine_egfr, cbc
    advance: acute hemodynamic crisis resolved + chronic HCM disease-modifying plan documented
  10. 10DISPOSITION
    CICU 48-72 h for monitoring (obstruction crisis + arrhythmia surveillance window); cardiology + EP + HCM-specialist consult; cardiac surgery on standby if severe LVOT gradient + refractory symptoms (septal reduction therapy referral)
    advance: unit assigned + HCM-specialist consult activated
  11. 11MONITORING
    Telemetry continuous first 48-72 h (arrhythmia surveillance + AF detection); serial echo for LV function recovery; serial hsTn to peak; BMP daily + Mg + K repletion; QT on disopyramide; if AFib AC therapeutic; serial Holter for NSVT (SCD modifier); echo q4w during mavacamten titration per REMS
    inputs: hs_troponin_serial, echo_lvot_gradient_and_sam, potassium, creatinine_egfr
    actions: panel.cardiac
    advance: monitoring schedule documented
  12. 12FOLLOWUP
    HCM specialist clinic within 1-2 weeks; cascade family genetic counseling + screening (50% autosomal dominant inheritance per ACC/AHA 2024); mavacamten REMS echo q4w during titration then q12w maintenance; ICD/septal reduction decision finalized per SCD criteria; AC continuation indefinite if AF; sports clearance shared decision; cardiac rehab if NYHA II-III (modified intensity — avoid heavy isometric exercise); long-term cardiology surveillance
    advance: long-term plan + family screening + follow-up cadence finalized