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cardio.atrial_flutter.adult-congenital-heart-disease.v1

Atrial flutter / IART in adult congenital heart disease (ACHD)

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Phase E variant of cardio.atrial_flutter.v1 — narrowed to atrial flutter / intra-atrial reentrant tachycardia (IART) in adults with congenital heart disease (ACHD). Substrate: post-Fontan, post-Mustard/Senning, repaired TOF, repaired ASD/VSD/AVSD, Ebstein, cc-TGA — congenital atrial scar + chamber dilation + chronic substrate. Critical management distinctions: 1:1 AV conduction with collapse common in Mustard/Senning (DCCV 200 J biphasic emergent); rate-only strategy INADEQUATE in failing systemic RV or failing Fontan (rhythm control preferred); ACHD center referral MANDATORY for 3D electroanatomic mapping ablation (success only 50–70% vs >95% for CTI). AC essentially universal per PACES/HRS 2014 (PMID 24681262) — overrides CHA2DS2-VASc score for Fontan / Mustard / Senning / repaired-cyanotic patients; warfarin often preferred over DOAC in Fontan/cyanotic due to limited safety data. Amiodarone first-line AAD given structural HD substrate; class IC AAD (flecainide, propafenone) ABSOLUTELY CONTRAINDICATED per CAST (PMID 1900101); sinus node dysfunction common (post-Mustard/Senning ~30–50%) — pacemaker often needed before rate-control AAD. Sister-differentiated from cardio.atrial_flutter.post-cardiac-surgery.v1 (acquired surgical scar, time-limited POAF) and cardio.atrial_flutter.atypical-left-atrial.v1 (post-PVI/post-CABG acquired substrate). Inherits AC + acute rate/rhythm management arc from parent cardio.atrial_flutter.v1; specializes for congenital substrate + systemic ventricular failure context + ACHD-center ablation pathway. 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 Phase E wave 24.

Entry points (6)

  • history
    Sustained atrial tachycardia / IART in adult with prior Fontan palliation (single-ventricle physiology) — high-risk hemodynamic substrate; ACHD center referral mandatory
    sustained_atrial_tachycardia_post_fontan
  • history
    Sustained atrial tachycardia / IART in adult with prior Mustard or Senning atrial-switch repair for d-TGA — risk of 1:1 AV conduction and systemic RV failure
    sustained_atrial_tachycardia_post_mustard_or_senning
  • history
    Sustained atrial tachycardia / IART in adult with repaired tetralogy of Fallot, ASD, VSD, AVSD, or other congenital lesion with atrial scar substrate
    sustained_atrial_tachycardia_post_repaired_tof_or_asd
  • symptom
    Palpitations / dyspnea / fatigue / syncope in adult with known congenital heart disease history — high pre-test probability of IART
    palpitations_with_known_achd_history
  • imaging
    ECG showing atypical flutter morphology (no classic sawtooth, slow cycle length 250–350 ms, often 1:1 conduction) in patient with known ACHD
    achd_ecg_with_atypical_flutter_morphology
  • vital_abnormality
    Sudden hemodynamic collapse with rapid regular tachycardia in Mustard/Senning patient — suspect 1:1 AV conduction during IART; emergent DCCV
    sudden_hemodynamic_collapse_with_1to1_av_conduction_post_atrial_switch

Required inputs (15)

  • agerequired
    demographic • used at CONTEXT
    ACHD patients live decades with congenital substrate; arrhythmias typically appear in 3rd–4th decade and accelerate; informs lifelong AC + AAD planning
  • congenital_diagnosis_and_repair_historyrequired
    history • used at CONTEXT
    Fontan vs Mustard/Senning vs repaired TOF vs repaired ASD/VSD/AVSD vs Ebstein vs cc-TGA — drives substrate, ablation approach, AC threshold, and systemic ventricular dysfunction risk
  • systemic_ventricular_morphologyrequired
    history • used at CONTEXT
    Systemic LV (most repaired ACHD) vs systemic RV (Mustard/Senning, cc-TGA) vs single ventricle (Fontan) — determines GDMT applicability and rate-vs-rhythm preference
  • sbprequired
    vital • used at RED_FLAGS
    Hemodynamic stability + 1:1 AV conduction risk in Mustard/Senning drives emergent DCCV decision; SBP <90 with rapid regular tachycardia → DCCV 200 J biphasic immediately
  • hrrequired
    vital • used at CONTEXT
    Atrial rate vs ventricular rate (often 1:1 or 2:1 in ACHD); cycle length 250–350 ms common; 1:1 conduction at HR 200–250 with hemodynamic collapse mandates DCCV
  • spo2required
    vital • used at CONTEXT
    Cyanotic ACHD baseline (SpO2 80–88% in unrepaired or palliated cyanotic lesions); acute drop signals tachycardia-mediated decompensation or pulmonary embolism
  • ecg_12_leadrequired
    imaging • used at INITIAL_WORKUP
    IART morphology — slow cycle length, atypical wave morphology, often 1:1 AV conduction; baseline ECG comparison essential because ACHD baseline often abnormal (RBBB, RVH, axis deviation)
  • prior_arrhythmia_and_AAD_historyrequired
    history • used at CONTEXT
    Prior IART episodes, AAD trials, ablation attempts inform recurrence risk and ablation candidacy; many ACHD patients have decades of arrhythmia history
  • creatinine_egfrrequired
    lab • used at INITIAL_WORKUP
    DOAC + AAD dosing; contrast for 3D mapping/ablation; many ACHD patients have CKD from chronic Fontan circulation or cyanotic-nephropathy
  • tsh_lft_pre_amiorequired
    lab • used at INITIAL_WORKUP
    Amiodarone toxicity baseline (TFTs, LFTs, PFTs) — required pre-amiodarone load especially given decades of anticipated treatment in young ACHD patients
  • cbc_with_hematocritrequired
    lab • used at INITIAL_WORKUP
    Cyanotic ACHD often have erythrocytosis (Hct 50–65%) — elevated thrombosis risk + relative anemia of cyanosis if Hct lower than expected; informs AC management
  • tte_with_systemic_ventricular_assessmentrequired
    imaging • used at INITIAL_WORKUP
    Systemic ventricular function (LV vs RV vs single), valve status, residual shunts, atrial chamber size, baseline saturations; ACHD-specific echo expertise often needed
  • tee_or_cardiac_mri_pre_ablation_or_dccv
    imaging • used at TREATMENT
    TEE or cardiac MRI to exclude atrial thrombus pre-DCCV/ablation when AFL persistent >48h and AC not therapeutic ≥3 wk; ACHD-specific anatomy often requires cardiac MRI for chamber definition
  • cha2ds2_vasc_factorsrequired
    history • used at RISK_STRATIFICATION
    CHA2DS2-VASc undervalues ACHD-specific stroke risk; PACES/HRS 2014 (PMID 24681262) recommends AC for any sustained atrial arrhythmia in Fontan or cyanotic patients regardless of score
  • bleeding_historyrequired
    history • used at RISK_STRATIFICATION
    HAS-BLED + ACHD-specific bleed risk (cyanotic patients have qualitative platelet dysfunction; Fontan patients have hepatic congestion → coagulopathy)

12-phase flow (11)

  1. 1FRAME
    IART in ACHD = scar-mediated macroreentry from congenital atriotomy + chamber dilation + chronic substrate. Distinct from typical CTI flutter: slow cycle length 250–350 ms, often 1:1 AV conduction, atypical morphology, lifelong substrate. ACHD center referral MANDATORY for sustained arrhythmia in Fontan, Mustard/Senning, repaired-cyanotic patients. Rate-only strategy INADEQUATE in failing systemic RV — rhythm control preferred.
    inputs: congenital_diagnosis_and_repair_history, systemic_ventricular_morphology
    advance: ACHD substrate + systemic ventricular morphology documented
  2. 2ENTRY
    Palpitations / dyspnea / fatigue / syncope / sudden hemodynamic collapse in adult with congenital heart disease history; ACHD-specific ECG interpretation critical (baseline often abnormal: RBBB, RVH, axis deviation)
    inputs: age
    advance: engine entered + ACHD center notified
  3. 3CONTEXT
    Detailed congenital diagnosis (Fontan / Mustard / Senning / repaired TOF / ASD / VSD / AVSD / Ebstein / cc-TGA), prior surgeries, current systemic ventricular function, baseline saturation, prior arrhythmia history, prior AAD trials, current AC therapy, sinus node function, pacemaker status
    inputs: hr, spo2, cha2ds2_vasc_factors, bleeding_history, prior_arrhythmia_and_AAD_history
    advance: context complete + ACHD provider identified
  4. 4RED_FLAGS
    Hemodynamic instability with 1:1 AV conduction (Mustard/Senning at HR 200–250) → emergent synchronized DCCV 200 J biphasic; cyanotic ACHD with acute SpO2 drop → suspect tachycardia-mediated decompensation OR pulmonary embolism (high baseline risk in Fontan); sudden hemodynamic collapse → DCCV first then workup; failing Fontan with new IART → ICU + heart-failure team
    inputs: sbp
    actions: tachycardia, cardiogenic_shock
    advance: stable or cardioverted + ACHD center notified
  5. 5INITIAL_WORKUP
    ECG + TSH/LFTs (amiodarone screen) + BMP + Mg + creatinine + CBC with Hct (cyanotic erythrocytosis) + BNP + ACHD-specific TTE; baseline Holter if not recently done
    inputs: ecg_12_lead, tsh_lft_pre_amio, creatinine_egfr, cbc_with_hematocrit, tte_with_systemic_ventricular_assessment
    actions: acs_pathway, panel.cardiac, panel.renal, panel.cbc
    advance: workup complete + ACHD-specific echo read
  6. 6BRANCHING_WORKUP
    TEE or cardiac MRI to exclude atrial thrombus pre-DCCV/ablation when AFL persistent >48h and AC not therapeutic ≥3 wk; concomitant AF surveillance via Holter; cardiac MRI for chamber-anatomy definition pre-ablation; PE workup if SpO2 drop in Fontan (high baseline risk); chest pain workup for ACS (rare in ACHD without coronary anomaly)
    inputs: tee_or_cardiac_mri_pre_ablation_or_dccv
    actions: afib_new_onset
    advance: branch resolved + thrombus exclusion documented
  7. 7RISK_STRATIFICATION
    CHA2DS2-VASc + PACES/HRS 2014 ACHD-specific AC criteria (universal AC for Fontan / cyanotic / Mustard / Senning regardless of score); HAS-BLED + ACHD-specific bleed risk (cyanotic platelet dysfunction, Fontan hepatic congestion); SOFA if shock complicates; eGFR for DOAC + AAD dosing
    inputs: cha2ds2_vasc_factors, bleeding_history
    actions: calc.cha2ds2vasc, calc.ckd_epi_2021
    advance: risk tier + AC indication documented
  8. 8TREATMENT
    Acute: rate control limited by ventricular dysfunction (BB cautious if failing systemic RV; non-DHP CCB CONTRAINDICATED if EF <40 — common in this cohort); rhythm control PREFERRED for failing systemic RV — amiodarone first-line; DCCV 200 J biphasic for hemodynamic instability or 1:1 AV conduction. Long-term: ACHD-center 3D electroanatomic mapping + ablation (success 50–70%, lower than CTI); AC essentially universal per PACES/HRS 2014 (PMID 24681262); sinus node dysfunction often requires pacemaker. Class IC AAD CONTRAINDICATED in systemic ventricular dysfunction (CAST PMID 1900101).
    inputs: hr, creatinine_egfr, cbc_with_hematocrit
    advance: acute strategy + lifelong AC + ACHD center referral booked for 3D mapping
  9. 9DISPOSITION
    Admit if unstable, new HF, AAD initiation (esp dofetilide REMS), recent ablation, peri-ablation bridging, or any Fontan/Mustard/Senning patient with sustained IART; transfer to ACHD center if not already at one for 3D mapping; ICU if hemodynamic compromise or 1:1 AV conduction risk
    advance: disposition documented + ACHD center transfer arranged if applicable
  10. 10MONITORING
    Telemetry continuous; QTc on amiodarone / sotalol; post-ablation observation for groin hematoma, tamponade, AV block (more common in ACHD ablation), atrioesophageal fistula (rare with right-sided ACHD ablation); AC adherence; cyanotic erythrocytosis monitoring; Fontan-failure surveillance
    inputs: ecg_12_lead, cbc_with_hematocrit
    advance: monitoring orders documented + ACHD-specific complication watch in place
  11. 11FOLLOWUP
    ACHD-center cardiology q3–6 mo; AC continuation indefinite (lifelong); post-ablation 4-week ECG + Holter at 3/6/12 mo for IART/AF screen; pacemaker interrogation if applicable; systemic ventricular function surveillance; pregnancy counseling (high-risk in ACHD with arrhythmia + AC); cardiac rehab (ACHD-specific protocol); mental-health support (chronic-disease anxiety high in ACHD)
    advance: lifelong follow-up booked at ACHD center + AC + AAD plan documented