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cardio.atrial_flutter.thyroid-related.v1

Thyrotoxicosis-precipitated atrial flutter

cardiologyacuteadultacuteinpatienttransitionoutpatient
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Phase E variant of cardio.atrial_flutter.v1 — narrowed to thyrotoxicosis-precipitated atrial flutter. Inherits acute rate/rhythm + AC management from parent via routing; specializes for the thyroid-trigger axis with mechanism-aware drug choice (propranolol PREFERRED — also blocks T4→T3 conversion; AVOID AMIODARONE — 37% iodine by weight risks jodbasedow + storm), thionamide initiation (methimazole 20-30 mg/d preferred; PTU 1st trimester / storm / methimazole intolerance), and AC during active thyrotoxicosis even at low CHA2DS2-VASc per ATA 2016 + ACC/AHA 2024 endorsement. Distinguishing features vs general AFL: trigger is identifiable + reversible (~60-70% AFL resolves with euthyroid state); definitive thyroid therapy (RAI vs thyroidectomy vs prolonged thionamide × 12-18 mo with 45-60% Graves remission) is the long-term anchor; warfarin contraindicated relative (clotting factor metabolism shifts erratically during hyperthyroid → euthyroid transition) — DOAC preferred. Severity triggers: thyroid storm Burch-Wartofsky ≥45 (life-threatening — full storm protocol with PTU + SSKI ≥1h after + hydrocortisone + cholestyramine + cooling); amiodarone exposure error in active thyrotoxicosis (iodine precipitates worsening); AC bleed during transition (warfarin INR erratic — DOAC preferred + ANNEXA-4 reversal); persistent AFL post-euthyroid (substrate-driven — EP for CTI ablation); thionamide agranulocytosis or hepatotoxicity (immediate cessation + expedite definitive therapy). Routes thyroid storm to ICU + simultaneous storm protocol; routes persistent post-euthyroid AFL to cardio.atrial_flutter.typical-cavotricuspid.v1 for CTI ablation candidacy (curative >95% per Calkins 2007 PMID 17572388); routes thyrotoxicosis-induced HF to cardio.acute-hf.thyrotoxicosis.v1. Manifest pointer reuses cardio.atrial_flutter.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 as thyrotoxicosis-precipitated atrial flutter variant.

Entry points (4)

  • symptom
    Palpitations + tachycardia + heat intolerance + tremor + weight loss + diaphoresis in patient with new-onset AFL/AF — thyrotoxicosis screen mandatory
    palpitations_with_hyperthyroid_features
  • imaging
    Atrial flutter on 12-lead ECG + suppressed TSH (<0.1) + elevated free T4/T3 — thyrotoxicosis-precipitated AFL confirmed
    aflutter_with_suppressed_tsh
  • history
    Known Graves disease, toxic multinodular goiter, or toxic adenoma + new AFL/AF presentation
    graves_or_toxic_nodule_with_aflutter
  • symptom
    Burch-Wartofsky score ≥45 (thyroid storm) + AFL with hemodynamic instability — emergent simultaneous storm + arrhythmia management
    thyroid_storm_with_aflutter

Required inputs (18)

  • agerequired
    demographic • used at CONTEXT
    Hyperthyroidism + AFL prevalence rises with age (~25 % >60 y); CHA2DS2-VASc + bleed risk for AC decision
  • sexrequired
    demographic • used at CONTEXT
    Female sex = +1 CHA2DS2-VASc; F:M ≈ 4:1 for thyrotoxicosis itself; pregnancy considerations affect thionamide choice (PTU 1st trimester, methimazole 2nd/3rd)
  • sbprequired
    vital • used at RED_FLAGS
    SBP <90 with flutter RVR + thyrotoxicosis → DCCV or aggressive BB; high-output state may have widened pulse pressure with normal SBP but compromised CO
  • hrrequired
    vital • used at CONTEXT
    Resting HR >100 even in NSR is hallmark; flutter HR commonly 130–180; rate control target 80–110
  • temperaturerequired
    vital • used at RED_FLAGS
    Hyperpyrexia ≥38.5 °C is a Burch-Wartofsky storm criterion; differentiates simple thyrotoxicosis from storm
  • ecg_12_leadrequired
    imaging • used at INITIAL_WORKUP
    Confirm flutter morphology + rate; rule out concomitant AF; QT for medication risk; check for ischemic changes (demand-ischemia possible at high rates)
  • echo_screening_for_structural_diseaserequired
    imaging • used at INITIAL_WORKUP
    TTE for LV function (often preserved or hyperdynamic in thyrotoxicosis; LV dysfunction suggests tachycardia-mediated cardiomyopathy or chronic substrate); LA size; valvular disease screen
  • tsh_free_t4_free_t3required
    lab • used at INITIAL_WORKUP
    Cornerstone diagnostic — TSH suppressed (<0.1) + elevated free T4 and/or free T3 confirms overt hyperthyroidism; T3 toxicosis pattern (T4 normal, T3 high) seen in early Graves or toxic adenoma
  • tsi_or_trab
    lab • used at BRANCHING_WORKUP
    TSI (thyroid-stimulating immunoglobulin) or TRAb to confirm Graves etiology; positive in ~95 % of Graves; guides definitive therapy choice
  • thyroid_ultrasound_or_raiu
    imaging • used at BRANCHING_WORKUP
    Thyroid ultrasound or RAIU/scan to differentiate Graves (diffuse uptake, vascular) from toxic nodule (focal uptake) from thyroiditis (low uptake) — affects definitive therapy decision
  • lft_panelrequired
    lab • used at CONTEXT
    Baseline LFTs before thionamide initiation (methimazole + PTU both have hepatotoxicity risk; PTU > methimazole); thyrotoxicosis itself can elevate ALP; severe LFT abnormality affects DOAC vs warfarin choice
  • cbc_with_diffrequired
    lab • used at CONTEXT
    Baseline before thionamide (agranulocytosis risk 0.2–0.5 %); leukocytosis can occur in storm
  • troponinrequired
    lab • used at INITIAL_WORKUP
    Rule out demand-ischemia at high rates; tachycardia-mediated injury possible; baseline before high-dose BB
  • creatininerequired
    lab • used at TREATMENT
    eGFR for DOAC dosing; thyrotoxicosis can transiently affect renal function via volume changes
  • cha2ds2_vasc_factorsrequired
    history • used at RISK_STRATIFICATION
    CHA2DS2-VASc for AC indication; CRITICAL CAVEAT — thyrotoxicosis itself raises stroke risk independent of CHA2DS2-VASc, so AC is generally indicated during active thyrotoxicosis even at score 0–1 (ACC/AHA 2024 + ATA 2016 endorsement)
  • bleeding_historyrequired
    history • used at RISK_STRATIFICATION
    HAS-BLED for AC bleed-risk; warfarin dosing erratic in hyperthyroid → euthyroid transition (clotting factor metabolism shifts) — DOAC preferred
  • iodine_exposure_recentrequired
    history • used at CONTEXT
    Recent iodinated contrast, amiodarone exposure, kelp/iodine supplements — affects RAI eligibility (need 4–6 wk washout); jodbasedow risk in nodular goiter
  • burch_wartofsky_scorerequired
    history • used at RED_FLAGS
    Burch-Wartofsky Point Scale for thyroid storm severity (45+ = storm, 25–44 = impending storm, <25 = unlikely); drives ICU vs floor disposition + simultaneous storm protocol

12-phase flow (11)

  1. 1FRAME
    Thyrotoxicosis-precipitated AFL = trigger-identifiable + reversible arrhythmia. Acute focus: BB-first rate control (mechanism-aware — also reduces T4→T3 conversion at high propranolol doses) + AVOID AMIODARONE (iodine load) + thionamide initiation + AC during active thyrotoxicosis even at low CHA2DS2-VASc; Long-term focus: definitive thyroid therapy (RAI vs thyroidectomy vs prolonged thionamide) — AFL usually resolves with euthyroid state
    inputs: ecg_12_lead, tsh_free_t4_free_t3
    advance: Thyrotoxicosis + flutter pattern framed
  2. 2ENTRY
    Quantify thyroid status (TSH, free T4, free T3); document flutter morphology + rate + symptom burden; CV/respiratory exam for hemodynamic stability + thyroid storm features (Burch-Wartofsky)
    inputs: age, hr, temperature
    advance: Thyroid status + flutter + storm screen documented
  3. 3CONTEXT
    Etiology workup (Graves vs toxic nodule vs thyroiditis); pregnancy status (affects thionamide choice); recent iodine exposure (amiodarone, contrast — affects RAI timing + jodbasedow risk); prior thyroid history; LFT + CBC baseline before thionamide
    inputs: sex, lft_panel, cbc_with_diff, iodine_exposure_recent
    advance: Etiology + pregnancy + iodine exposure + baseline labs documented
  4. 4RED_FLAGS
    Thyroid storm (Burch-Wartofsky ≥45 — hyperpyrexia + tachycardia + CNS dysfunction + GI/hepatic + cardiovascular) requiring ICU + simultaneous storm protocol; hemodynamic instability with flutter (DCCV); high-output HF; demand-ischemia at high rates
    inputs: sbp, burch_wartofsky_score
    actions: acs_pathway
    advance: Storm severity + hemodynamic stability + ischemia screen complete
  5. 5INITIAL_WORKUP
    12-lead ECG + telemetry; TTE (LV function, LA size, valvular); TSH + free T4 + free T3 (mandatory cornerstone); CMP + Mg + LFTs + CBC + troponin; pregnancy test in reproductive-age women
    inputs: ecg_12_lead, echo_screening_for_structural_disease, tsh_free_t4_free_t3, troponin, creatinine
    actions: panel.cardiac, panel.renal
    advance: Workup confirms thyrotoxicosis + flutter + structural assessment + baseline labs
  6. 6BRANCHING_WORKUP
    TSI/TRAb for Graves confirmation; thyroid US or RAIU/scan for etiology (Graves vs nodule vs thyroiditis); endocrinology consult; TEE if cardioversion >48 h after symptom onset (LAA thrombus screen — but most thyrotoxicosis-AFL of unknown duration so often AC × 4 wk pre-CV alternative)
    actions: afib_new_onset, tachycardia
    advance: Etiology + cardioversion strategy documented
  7. 7RISK_STRATIFICATION
    CHA2DS2-VASc for AC indication WITH CRITICAL CAVEAT — thyrotoxicosis itself raises stroke risk independent of score; AC generally indicated during active thyrotoxicosis even at score 0–1; HAS-BLED for AC bleed-risk; eGFR for DOAC dosing; Burch-Wartofsky tier for storm severity
    inputs: cha2ds2_vasc_factors, bleeding_history
    actions: calc.cha2ds2vasc, calc.has_bled, calc.ckd_epi_2021
    advance: AC + storm tier + DOAC dose documented
  8. 8TREATMENT
    Acute: PROPRANOLOL FIRST (40 mg PO q4-6h or 1 mg IV slow up to 5 mg — also reduces T4→T3 conversion at high doses) for rate control + symptom palliation; metoprolol/atenolol/esmolol acceptable alternatives; AVOID AMIODARONE (37 % iodine by weight — can precipitate or worsen storm/jodbasedow); DCCV ONLY if hemodynamically unstable (flutter often refractory until euthyroid; spontaneous CV common with euthyroid state); methimazole 20–30 mg/d initiation (PTU 100 mg q8h for 1st-trimester pregnancy, storm, or methimazole intolerance); cholestyramine 4 g QID adjunct in storm; iodine (SSKI 5 drops PO q6h) starting ≥1 h AFTER thionamide for storm to block release; hydrocortisone 100 mg IV q8h for storm (blocks T4→T3 conversion + autoimmune component); apixaban 5 mg BID DOAC preferred during active thyrotoxicosis even at low CHA2DS2-VASc
    inputs: creatinine
    advance: BB + thionamide + AC initiated; storm protocol active if applicable
  9. 9DISPOSITION
    Outpatient management feasible if mild thyrotoxicosis + stable flutter + euthyroid trajectory + endocrinology engagement positive; admit if Burch-Wartofsky 25–44 (impending storm) or hemodynamic instability or new severe LV dysfunction; ICU if Burch-Wartofsky ≥45 (storm)
    advance: Disposition documented
  10. 10MONITORING
    24-48 h telemetry for rhythm response to BB; daily TFTs in storm (every 24-48 h until trending normal then weekly); LFT + CBC at 2 + 4 wk on thionamide (hepatotoxicity + agranulocytosis surveillance); INR weekly if warfarin (erratic during transition); 4-wk post-CV AC adherence + bleed surveillance
    inputs: ecg_12_lead
    advance: Monitoring complete + thyroid trajectory + flutter response documented
  11. 11FOLLOWUP
    Endocrinology q4-6 wk during thionamide titration to euthyroid; definitive therapy decision (RAI 6-12 mo of thionamide, OR thyroidectomy if large goiter/compressive symptoms/pregnancy planned/RAI-ineligible, OR continued thionamide); cardiology surveillance for AFL recurrence post-euthyroid (most resolve; ablation if persistent); long-term AC reassessment (typically discontinue once euthyroid + sustained NSR + low CHA2DS2-VASc; continue if recurrent or score ≥2)
    advance: Endocrine + cardiology + definitive therapy + AC plan documented