Antithrombotic Therapy in Pediatric Heart Disease

By lesion and procedure, neonate to adolescent: agent, start, target, duration; graded rows by source, adult rows labelled

Lesion or procedure

Systemic-to-PA shunt (mBTT, central) and Norwood

Agent: Aspirin; UFH, or bivalirudin, until aspirin starts (AATS 2026, neonates and infants)
Start: Parenteral anticoagulation should be considered until enteral aspirin can start after surgery. Norwood: consider UFH if aspirin cannot start within 48 h
Dose: Aspirin commonly 3–5 mg/kg/dose; UFH 10–15 units/kg/h in most studies, no optimal regimen established (AATS 2026 text)
Duration: Aspirin indefinitely (AATS 2026)
Monitoring: Routine aspirin monitoring typically not required (AATS 2026 Table 3); heparin targets in Targets
Shunt occlusion: IV heparin bolus 50–100 U/kg, raise systemic pressure, ventilate; expect cath, revision or ECMO. Systemic thrombolysis may be harmful (AHA 2013)
Next procedure: Avoid holding aspirin; if it must be held, bridge with LMWH or UFH (AATS 2026)

Graded rows

AATS 2026 Table 6, neonates and infants
Procedure	Post-procedure	Long-term	Before another procedure
Systemic-to-pulmonary shunt (mBTT, central shunt)	Post-procedure IB-NR Aspirin IIaB-NR UFH until aspirin is started IIbC-EO Bivalirudin until aspirin is started	Long-term IB-NR Aspirin indefinitely IIbC-EO Dual antiplatelet therapy for complex shunt scenarios	Before another procedure IIbC-EO Avoid holding aspirin; if holding is necessary, bridge with LMWH or UFH
Norwood (HLHS) (Sano)	Post-procedure IB-NR Aspirin IIaB-NR Consider UFH if aspirin cannot start within 48 h IIbC-EO Consider bivalirudin if aspirin cannot start within 48 h	Long-term IB-NR Aspirin indefinitely	Before another procedure IIbC-EO Avoid holding aspirin; if holding, bridge with LMWH or UFH

AHA 2013 §9.1, PTFE systemic-to-PA shunt, infants and children
Class	Recommendation	LOE
I	No increased bleeding risk: long-term low-dose aspirin	B
IIa	Continuous low-dose heparin infusion early after surgery, once surgical bleeding concerns have resolved	C
IIa	A thrombosis risk factor (suspected or confirmed infection, CVL thrombus, stented shunt, hypercoagulable state): systemic heparinization early after surgery (“probably recommended”)	C
IIa	Acute shunt thrombosis: IV heparin bolus 50–100 U/kg and consider an infusion; raise systemic pressure (phenylephrine or epinephrine to effect); intubate, ventilate, paralyse; anticipate cath, shunt revision or ECMO	C
IIb	Sustained high risk (stented shunt, hypercoagulable state): anticoagulant plus antiplatelet, e.g. LMWH plus aspirin or clopidogrel	C
III	Systemic thrombolysis (e.g. tPA) for shunt thrombosis may be harmful	C

CHEST 2012, modified Blalock-Taussig shunt (MBTS), neonates and children
Grade	Recommendation	No.
Grade 2C	Intraoperative UFH	2.6
Grade 2C	After surgery: aspirin or no antithrombotic therapy, rather than prolonged LMWH or VKA	2.6

Where sources differ

Long term: aspirin indefinitely (AATS 2026, I) or long-term aspirin (AHA 2013, I), but aspirin or no therapy (CHEST 2012, 2C).
Early heparin until aspirin: AATS 2026 (IIa) and AHA 2013 (IIa); CHEST 2012 grades intraoperative UFH only.

Palliated single ventricle at any stage (AHA 2013 §9.2): risk-factor assessment, TTE surveillance, confirming a suspected thrombus, starting or escalating therapy when risk factors are present: rows under .

RV–PA conduit (including Sano)

Norwood, Sano: AATS 2026 Table 6 prints a “Norwood (HLHS) (Sano)” row, shown under ; it does not state which row a Norwood with an mBTT shunt follows
Agent: None routinely after surgery; aspirin long term (AATS 2026, neonates and infants)
Start: Pulmonary atresia, RV–PA conduit: none. Rastelli/Nikaidoh, truncus (and Ross/Konno in Table 6): consider UFH if aspirin is necessary for the conduit type and cannot start within 48 h. Low-dose short-acting IV anticoagulation may be considered for the first 24–72 h and first week, until enteral antiplatelet therapy (S23, IIb)
Dose: Low-dose UFH 10–15 units/kg/h; aspirin 3–5 mg/kg/d (AATS 2026 text)
Duration: Aspirin 3–6 months (pulmonary atresia, Rastelli/Nikaidoh) or indefinitely (truncus); indefinitely may be considered by conduit material and risk
Next procedure: Avoid holding aspirin; if necessary, hold for 5–7 d

Graded rows

AATS 2026 Table 6, neonates and infants
Procedure	Post-procedure	Long-term	Before another procedure
Pulmonary atresia, RV–PA conduit	Post-procedure IIbC-EO None	Long-term IIbC-EO Aspirin 3–6 mo	Before another procedure IIbC-EO Avoid holding aspirin; if necessary, hold 5–7 d
Rastelli or Nikaidoh (RV–PA conduit)	Post-procedure IIbC-EO None; consider UFH if aspirin is needed for the conduit type and cannot start within 48 h	Long-term IIbC-EO Aspirin 3–6 mo	Before another procedure IIbC-EO Avoid holding aspirin; if necessary, hold 5–7 d
Truncus arteriosus repair (RV–PA conduit)	Post-procedure IIbC-EO None; consider UFH if aspirin is needed for the conduit type and cannot start within 48 h	Long-term IIbC-EO Aspirin indefinitely	Before another procedure IIbC-EO Avoid holding aspirin; if necessary, hold 5–7 d

AATS 2026 statements, conduits, nonautologous patches, extensive baffles
CoR	Statement	LoE
IIb	Low-dose short-acting IV anticoagulation until enteral antiplatelet therapy is feasible, in the immediate (24–72 h) and early (first week) postoperative period (S23)	C-EO
IIb	Long term: aspirin monotherapy, duration by procedure and thrombotic risk (S24)	C-EO

AHA 2013 and CHEST 2012 give no conduit row. AHA 2013: after a bioprosthetic pulmonary valve it is reasonable to forgo anticoagulation ().

Ductal or RVOT stent

Risk tier: Ductal stent for pulmonary blood flow: High. Ductal stent for systemic blood flow, ventricular outflow tract: Low. Stent ≥4 mm (bare-metal or drug-eluting): Low; <4 mm: Moderate; covered stent: High (AATS 2026 Table 7)
Lower risk: Aspirin for 6 months (I); consider prophylactic UFH or LMWH if aspirin cannot start within 24 h (Table 6, IIb)
Higher risk: Therapeutic UFH or LMWH after the procedure (IIa), then aspirin ± clopidogrel for at least 3–6 months (I); aspirin ± LMWH or ± DOAC (IIb) (AATS 2026 Table 6)
Graded rows: ; AHA 2013 lists ductal stents among endovascular stents

Table 7 has a Moderate tier that Table 6 does not grade separately; the text says agents escalate from single antiplatelet (low) to dual antiplatelet (moderate) to antiplatelet plus anticoagulant (high), with the plan set by the team.

Bidirectional Glenn, hemi-Fontan, comprehensive stage 2

Early: Glenn or hemi-Fontan: none (AATS 2026, IIa) vs postoperative UFH (CHEST 2012, 2C). Comprehensive stage 2: UFH until aspirin starts (AATS 2026, IIb)
Agent, long term: Aspirin (AATS 2026, I); antiplatelet therapy may be reasonable (AHA 2013, IIb). Comprehensive stage 2: aspirin ± LMWH or ± DOAC for 3–6 months may be considered
Monitoring: Large, persistent pleural effusions: clotting studies, AT III and anti-Xa (AHA 2013, IIb)
Next procedure: Avoid holding aspirin; if holding, bridge with LMWH or UFH (AATS 2026)

Graded rows

AATS 2026 Table 6, neonates and infants
Procedure	Post-procedure	Long-term	Before another procedure
Bidirectional Glenn, hemi-Fontan	Post-procedure IIaB-NR None	Long-term IB-NR Aspirin	Before another procedure IIbC-EO Avoid holding aspirin; if holding, bridge with LMWH or UFH
Comprehensive stage 2	Post-procedure IIbC-EO UFH until aspirin is started	Long-term IB-NR Aspirin IIbC-EO Aspirin ± LMWH for 3–6 mo IIbC-EO Aspirin ± DOAC for 3–6 mo	Before another procedure IIbC-EO Avoid holding aspirin; if holding, bridge with LMWH or UFH

AHA 2013 §9.1–9.2, infants and children
Class	Recommendation	LOE
IIb	Long-term antiplatelet prophylaxis after a superior cavopulmonary anastomosis	C
IIb	Chronically draining pleural effusions of significant volume: closely monitor clotting studies, AT III and anti-FXa levels	C

CHEST 2012, bilateral cavopulmonary shunt (BCPS), children
Grade	Recommendation	No.
Grade 2C	Postoperative UFH	2.35

Where sources differ

Early UFH after a Glenn: none (AATS 2026, IIa, B-NR) vs postoperative UFH (CHEST 2012, 2C).
Long term: aspirin, Class I (AATS 2026) vs antiplatelet therapy, IIb (AHA 2013).

Fontan

Agent: Aspirin or anticoagulation (warfarin, LMWH). Rivaroxaban: US-labelled for thromboprophylaxis in pediatric patients >2 y of age after Fontan surgery (as stated in AATS 2026 Table 3)
After surgery: Aspirin, or therapeutic UFH then VKA, over no therapy (CHEST 2012, 1C); warfarin or LMWH for 3–12 months may be reasonable (AHA 2013, IIb)
Long term: Antiplatelet therapy reasonable (AHA 2013, IIa); warfarin with risk factors (IIb); escalate in adolescence or adulthood (IIb)
Target: Warfarin INR 2–3; Fontan loading dose 0.1 mg/kg/day (AHA 2013)
Adult: Anticoagulation with known or suspected thrombus, atriopulmonary Fontan, prior thromboembolism, or sustained atrial flutter or fibrillation; otherwise aspirin or anticoagulation (ACHD 2025, 1, B-NR)
Monitoring: Periodic TTE looking for thrombus (AHA 2013, I); INR in Targets. Large, persistent pleural effusions: clotting studies, AT III and anti-Xa (AHA 2013 §9.1, IIb; row under )

Graded rows

AHA 2013 §9.2, palliated single ventricle (any stage)
Class	Recommendation	LOE
IIa	Long-term antiplatelet therapy after the Fontan	C
IIb	Warfarin or LMWH for 3 to 12 months after the Fontan	C
IIb	Long-term warfarin after the Fontan with anatomic or hemodynamic risk factors	C
IIa	Start or escalate therapy (antiplatelet to anticoagulant, or higher targets) if risk factors are present (become present) at any stage	C
IIb	Start or escalate therapy after the Fontan in adolescence or adulthood	C
I	Assess anatomic and hemodynamic risk factors; correct or minimize them	B
I	Reassess risk factors serially; correct new ones	C
I	Periodic TTE with attention to thrombus	C
IIa	Suspected thrombus: confirm with TEE, MRI, CT, CT angiography, lung perfusion scan or venography/angiography	C
IIb	With risk factors, TEE or MRI for surveillance	C

CHEST 2012, children
Grade	Recommendation	No.
Grade 1C	Aspirin, or therapeutic UFH followed by VKA, over no therapy	2.36

Adult ACHD 2025, adults with Fontan circulation
COR	Recommendation	LOE
1	Adult Known or suspected thrombus, atriopulmonary Fontan, history of thromboembolism, or sustained atrial flutter or fibrillation: anticoagulation	B-NR
1	Adult No high-risk features and no bleeding contraindication: aspirin or anticoagulation	B-NR

AHA 2019 Fontan statement, Table 18 (no class): risk of thromboembolism is increased; the best prevention is unclear, but some thromboprophylaxis, antiplatelet or anticoagulant, is warranted.

Direct oral anticoagulant trials

UNIVERSE (McCrindle 2021): ages 2–8 y, within 4 months of the Fontan, open-label, 12 months; rivaroxaban (weight-adjusted, twice daily) vs aspirin about 5 mg/kg daily. Thrombotic events 2% vs 9% (not powered for efficacy); major bleeding 2% (1 epistaxis needing transfusion) vs 0.
SAXOPHONE (Payne 2023) abstract: 28 days to <18 y, 74% single ventricle; apixaban vs VKA or LMWH, 1 year. Major or clinically relevant bleeding 0.8% vs 4.8%; all bleeding nearly twice as frequent on apixaban; no thromboembolic events.
ENNOBLE-ATE (Portman 2022) abstract: <18 y with cardiac disease; edoxaban once daily vs standard care, 3 months: one nonmajor clinically relevant bleed per group; one standard-care patient with DVT and PE.

Where sources differ

CHEST 2012 recommends aspirin or UFH then VKA (1C); AHA 2013 grades antiplatelet IIa and early warfarin or LMWH IIb; ACHD 2025 (Adult): with high-risk features, anticoagulation; otherwise “either aspirin or anticoagulation is recommended” (both 1, B-NR).

Mechanical valve

Agent: VKA (warfarin) for the life of the valve; UFH, or bivalirudin, until therapeutic on enteral anticoagulation (AATS 2026)
Mitral INR: 2.5–3.5 (AATS 2026 infants, I, A; AHA 2013, I, C)
Aortic INR: 2–3 (AATS 2026 infants, I, A). AHA 2013: bileaflet or Medtronic Hall 2.0–3.0; 2.5–3.5 with risk factors, with Starr-Edwards valves or mechanical disk valves (other than Medtronic Hall), and in the first 3 months
Add aspirin: May be considered with an indication and low bleeding risk, low dose 3–5 mg/kg (AATS 2026, IIb); recommended in adults (AHA 2013, I, Adult; data in children limited)
Bridging: If the procedure requires bridging, consider LMWH or UFH if INR <2 (mitral) or <1.5 (aortic) during VKA interruption (AATS 2026, IIb, C-EO, both)
Monitoring: INR daily until therapeutic, then at least monthly; retest with illness, diet or drug change (AHA 2013)
Avoid: DOACs should not be used in infants with mechanical valves (AATS 2026 Table 3)

Graded rows

AATS 2026 Table 6, neonates and infants
Procedure	Post-procedure	Long-term	Before another procedure
Mitral valve replacement (mechanical)	Post-procedure IA UFH until therapeutic on enteral anticoagulation IIbC-EO Bivalirudin until therapeutic on enteral anticoagulation	Long-term IA VKA, INR goal 2.5–3.5, + aspirin if there is an indication for antiplatelet therapy	Before another procedure IIbC-EO If the procedure requires bridging, consider LMWH or UFH if INR <2 during VKA interruption
Aortic valve replacement (mechanical)	Post-procedure IA UFH until therapeutic on enteral anticoagulation IIbC-EO Bivalirudin until therapeutic on enteral anticoagulation	Long-term IA VKA, INR goal 2–3, + aspirin if there is an indication for antiplatelet therapy	Before another procedure IIbC-EO If the procedure requires bridging, consider LMWH or UFH if INR <1.5 during VKA interruption

AATS 2026 statement, infants
CoR	Statement	LoE
IIb	Aspirin added to VKA (mechanical mitral or aortic) with an indication for antithrombotic therapy and low bleeding risk (S34)	C-EO

AHA 2013 §9.3, children
Class	Recommendation	LOE
I	Mitral, any mechanical valve: warfarin, INR 2.5–3.5	C
I	Aortic, bileaflet or Medtronic Hall: warfarin, INR 2.0–3.0; with risk factors 2.5–3.5	C
I	Aortic, Starr-Edwards valves or mechanical disk valves (other than Medtronic Hall), no risk factors: warfarin, INR 2.5–3.5	C
IIa	First 3 months after mechanical aortic valve: warfarin, INR 2.5–3.5	C
I	Unable to take warfarin after mitral or aortic replacement: low-dose aspirin	C
I	Adult Add low-dose aspirin to warfarin: mechanical valves, and bioprosthetic valves with risk factors (adult guidelines; data in children limited)	C

Where sources differ

Mechanical aortic valve: INR 2–3 in infants (AATS 2026, I, A) vs 2.5–3.5 with risk factors, with Starr-Edwards or non-Medtronic Hall disk valves, or in the first 3 months (AHA 2013).
Adding aspirin: IIb, C-EO in infants (AATS 2026 S34) vs Class I for adults (AHA 2013).

Bioprosthetic or transcatheter valve

Aortic, mitral: No risk factors: low-dose aspirin; warfarin INR 2.0–3.0 reasonable for the first 3 months. With risk factors: warfarin INR 2.0–3.0 (AHA 2013)
Pulmonary: Reasonable to forgo anticoagulation (AHA 2013, IIa)
Tricuspid: Warfarin INR 2.0–3.0 for 3–6 months and lifelong low-dose aspirin (IIa); long-term warfarin with reduced RV function or risk factors (IIb)
Neonates, infants: By valve type, position and risk (AATS 2026, IIa); Melody mitral: institutional pathway (IIa). Text: high-risk infants may benefit from short-term IV, then enteral anticoagulation for 3 months, then lifelong antiplatelet therapy
Transcatheter: No graded pediatric row for transcatheter pulmonary valves in these sources

Graded rows

AATS 2026 statements, neonates and infants
CoR	Statement	LoE
IIa	Thromboprophylaxis after any valve replacement based on valve characteristics, location, bleeding and thrombotic risk (S30)	C-EO
IIa	Melody (Medtronic) mitral valve: institutional care pathways and multidisciplinary team (S32)	C-EO

AHA 2013 §9.3, children (risk factors: previous thromboembolism, systemic ventricular dysfunction, hypercoagulable condition)
Class	Recommendation	LOE
I	Aortic or mitral, no risk factors: low-dose aspirin	C
I	Aortic with risk factors: warfarin, INR 2.0–3.0	C
I	Mitral with risk factors: warfarin, INR 2.0–3.0	C
IIa	Aortic or mitral, no risk factors, first 3 months: warfarin, INR 2.0–3.0	C
IIa	Pulmonary: forgo anticoagulation	C
IIa	Tricuspid, with or without decreased function: warfarin, INR 2.0–3.0 for 3–6 months	C
IIa	Tricuspid: lifelong low-dose aspirin	C
IIb	Tricuspid with decreased RV function or risk factors: long-term warfarin, INR 2.0–3.0	C

Low-dose aspirin if warfarin cannot be taken after mitral or aortic replacement (AHA 2013, I), and aspirin added to warfarin with risk factors (AHA 2013, I, Adult): rows under . CHEST 2012 (2.40–2.42, no grade printed): follow the adult recommendations for prosthetic valves.

Endovascular stents and septal devices

Lower risk: Aspirin for 6 months (AATS 2026, I; AHA 2013 noncoronary stents, at least 6 months, I). If aspirin cannot start within 24 h and the risk of thrombosis is deemed to outweigh the risk of bleeding, parenteral anticoagulation at prophylaxis dosing may be considered: UFH 10–15 units/kg/h or LMWH to anti-Xa 0.2–0.5 U/mL, or per institutional protocol (AATS 2026 text; Table 6, IIb)
Higher risk: Therapeutic UFH or LMWH after the procedure (AATS 2026, IIa, C-EO), then aspirin ± clopidogrel for at least 3–6 months (I, B-NR); aspirin ± LMWH or ± DOAC (IIb, C-EO). AHA 2013: in the absence of contraindications, warfarin or LMWH ± antiplatelet for 3–6 months, then antiplatelet (IIa)
Septal devices: Aspirin for at least 6 months (AHA 2013: ASD I, VSD IIa)
At placement: UFH 100 U/kg (maximum 5000 U); ASD devices at least 100 U/kg (AHA 2013, I)
Next procedure: Lower risk: avoid holding aspirin; if necessary, hold 5–7 d. Higher risk: avoid holding aspirin; if holding aspirin, bridge with LMWH or UFH (AATS 2026)

Thrombosis risk after catheter procedures, AATS 2026 Table 7
	Low	Moderate	High
Hardware	Low Bare-metal stent ≥4 mm Drug-eluting stent ≥4 mm Intracardiac devices	Moderate Bare-metal stent <4 mm Drug-eluting stent <4 mm Flow restrictor (modified Medtronic microvascular plug)	High Covered stent
Location	Low Ductal stent for systemic blood flow Pulsatile pulmonary artery Systemic artery Atrial or ventricular septum Ventricular outflow tract Ventricle–pulmonary artery conduit	Moderate Coronary artery Nonpulsatile pulmonary artery Systemic vein Pulmonary vein	High Ductal stent for pulmonary blood flow Postoperative (<30 d) nonpulsatile pulmonary artery Recanalized or severely hypoplastic pulmonary vein

Graded rows

AATS 2026 Table 6, catheterization, neonates and infants
Thrombosis risk	Post-procedure	Long-term	Before another procedure
Lower risk	Post-procedure IIbC-EO None; consider prophylactic UFH or LMWH if aspirin cannot start within 24 h	Long-term IB-NR Aspirin for 6 mo	Before another procedure IIbC-EO Avoid holding aspirin; if necessary, hold 5–7 d
Higher risk	Post-procedure IIaC-EO Therapeutic UFH or LMWH	Long-term IB-NR Aspirin ± clopidogrel for at least 3–6 mo IIbC-EO Aspirin ± LMWH for at least 3–6 mo IIbC-EO Aspirin ± DOAC for at least 3–6 mo	Before another procedure IIbC-EO Avoid holding aspirin; if holding, bridge with LMWH or UFH

AHA 2013 §13.3, children
Class	Recommendation	LOE
I	Stent placement: UFH bolus 100 U/kg (maximum 5000 U)	C
I	Noncoronary stents: low-dose aspirin for at least 6 months	C
IIa	Higher-risk lesions (nonpulsatile flow, previous complete occlusion, thrombophilic abnormality), in the absence of contraindications: warfarin or LMWH ± antiplatelet for 3–6 months, then antiplatelet alone	C
I	ASD device: at least 100 U/kg UFH (maximum 5000 U) at implantation	C
I	ASD device: low-dose aspirin for at least 6 months	C
IIb	ASD device, older children and adults: another anticoagulant with aspirin for 3–6 months	C
I	VSD device: UFH 100 U/kg (maximum 5000 U) at implantation	C
IIa	VSD device: low-dose aspirin for at least 6 months	C

CHEST 2012, children
Grade	Recommendation	No.
Grade 2C	Endovascular stents: UFH perioperatively	2.37

Where sources differ

Higher-risk stents: a combination including aspirin ± clopidogrel, Class I (AATS 2026), vs warfarin or LMWH ± antiplatelet, IIa (AHA 2013).
Lower-risk stents, 6 months of aspirin: level B-NR (AATS 2026) vs C (AHA 2013).

Catheter-related (CVL) thrombosis

Prevention: Remove lines once no longer essential (AHA 2013, I). Children with short- or medium-term CVADs: no routine systemic prophylaxis (CHEST 2012, 1B). Neonates and infants with CVCs: may be considered by risk (AATS 2026, IIb). Fontan candidates, or bacteremia or a hypercoagulable factor: low-dose IV heparin may be reasonable (AHA 2013, IIb). Neonates: UFH 0.5 units/kg/h is recommended to maintain CVAD patency, over no prophylaxis (CHEST 2012, 1A)
Treatment: Anticoagulate symptomatic thrombosis (ASH 2018, strong): UFH or LMWH initially, for at least 5 days (CHEST 2012, 1B); LMWH or VKA (ASH 2018, conditional)
Duration: ≤3 months if provoked; longer could be considered if the risk factor persists (ASH 2018). 3 months once the risk factor resolves; beyond 3 months while a reversible risk factor is ongoing (CHEST 2012, 2C). Neonates, if anticoagulated: 6 weeks to 3 months; or supportive care with imaging (CHEST 2012)
The line: Nonfunctioning or not needed: remove after at least 3–5 days of anticoagulation (CHEST 2012; ASH 2018: some days after anticoagulation starts). Functioning and needed: keep it (ASH 2018; CHEST 2012)
Line kept: After 3 months: prophylactic VKA, INR 1.5–1.9, or LMWH, anti-Xa 0.1–0.3 units/mL, until removal (CHEST 2012, 2C)
Right atrium: Anticoagulation for right atrial thrombosis (ASH 2018, conditional)

Graded rows

AATS 2026 statement, neonates and infants with CHD
CoR	Statement	LoE
IIb	Thromboprophylaxis with a CVC, by patient and anatomic risk factors, weighed against bleeding (S29)	C-EO

AHA 2013 §8.1, children with CHD
Class	Recommendation	LOE
I	Remove CVLs as soon as no longer clinically essential; review every line daily	C
IIa	Thrombus on imaging: consider removing the CVL, weighing embolization; follow with serial imaging	C
IIa	Documented acute CVL thrombus: anticoagulation if no contraindication	B
IIb	Future Fontan candidates: low-dose IV heparin until the CVL is removed	C
IIb	CVL with bacteremia or a hypercoagulable risk factor (high hematocrit, prior thrombosis, thrombophilia): low-dose IV heparin until removal	C

CHEST 2012, central venous access devices (CVADs)
Grade	Recommendation	No.
Grade 1B	Children, short- or medium-term CVADs: against routine systemic thromboprophylaxis	2.31
Grade 1A	Neonates: UFH continuous infusion at 0.5 units/kg per h to maintain CVAD patency, over no prophylaxis	2.4
Grade 1B	Children, first VTE: UFH or LMWH, initially for at least 5 days	2.22.1
Grade 2C	Children, secondary VTE with the risk factor resolved: anticoagulate for 3 months; with an ongoing but potentially reversible risk factor, continue beyond 3 months (therapeutic or prophylactic doses) until it resolves	2.22.3
Grade 1B	CVAD no longer required or nonfunctioning: remove	2.22.6
Grade 2C	At least 3–5 days of anticoagulation before removal	2.22.6
Grade 2C	CVAD functioning and still required: leave in place and anticoagulate	2.22.6
Grade 2C	CVAD still needed after 3 months: prophylactic VKA (INR 1.5–1.9) or LMWH (anti-Xa 0.1–0.3 units/mL) until removal; if thrombosis recurs on prophylaxis, therapeutic doses until the CVAD is removed and for a minimum of 3 months following the VTE	2.22.7
Grade 2C	Neonates, CVAD or UVC with confirmed thrombosis: either initial anticoagulation or supportive care with radiologic monitoring for extension, rather than no follow-up; in previously untreated patients, start anticoagulation if extension occurs	2.1
Grade 2C	Neonates, CVAD or UVC with thrombosis: remove after 3–5 days of therapeutic anticoagulation	2.1
Grade 2C	Neonates, if anticoagulated: LMWH, or UFH then LMWH, for 6 weeks to 3 months in total	2.1
Grade 2C	Neonates, line still in place when treatment ends: prophylactic dose until removal	2.1

ASH 2018, pediatric VTE (all very low certainty of evidence)
Strength	Recommendation	Certainty
Strong	Symptomatic DVT or PE: anticoagulation rather than none	very low
Conditional	LMWH or VKA	very low
Conditional	Provoked DVT or PE: ≤3 months rather than longer	very low
Conditional	Functioning CVAD still needed: do not remove	very low
Strong	Nonfunctioning or unneeded CVAD: remove	very low
Conditional	Remove it some days after anticoagulation starts, not immediately	very low
Conditional	Right atrial thrombosis: anticoagulation rather than none	very low

Where sources differ

Thrombus on a line: consider removal (AHA 2013, IIa) vs keep a functioning line that is still needed (ASH 2018; CHEST 2012).
Prophylaxis, in different groups: against routine use in children with short- or medium-term CVADs (CHEST 2012, 1B); may be considered by risk in neonates and infants with CVCs (AATS 2026, IIb); low-dose heparin may be reasonable in Fontan candidates or with bacteremia or a hypercoagulable factor (AHA 2013, IIb).
Duration: ≤3 months if provoked (ASH 2018) vs 3 months (CHEST 2012, children) vs 6 weeks to 3 months if anticoagulated (CHEST 2012, neonates); both allow longer while a risk factor persists.

Kawasaki disease

Antithrombotic management by coronary risk level (AHA 2024 Table 2) is on Kawasaki Coronary Z-Scores.

Targets and doses as printed

Agent	Target or dose	Source
UFH, therapeutic	Anti-Xa 0.35–0.7 U/mL; if unavailable, PTT 1.5–3× baseline	AHA 2013 Table 3; CHEST 2012 1.1
UFH, low dose	10–15 U/kg/h	AHA 2013 Table 3; AATS 2026
LMWH, therapeutic	Anti-Xa 0.5–1.0 U/mL at 4–6 h after the dose (or 0.5–0.8 at 2–6 h, CHEST)	CHEST 2012 1.2; AHA 2013 Table 3
LMWH, prophylactic	Anti-Xa 0.2–0.5 U/mL after a lower-risk stent (AATS) · 0.1–0.3 units/mL with a line kept after VTE (CHEST)	AATS 2026 text; CHEST 2012 2.22.7
Warfarin (VKA)	INR 2–3 (CHEST: 2.5, range 2.0–3.0); mechanical mitral 2.5–3.5; mechanical aortic in Mechanical valve	AHA 2013 Table 3; CHEST 2012 1.3
Warfarin, prophylactic	INR 1.5–1.9 (line kept after VTE)	CHEST 2012 2.22.7
Aspirin	1–5 mg/kg/day (maximum 81–325 mg/day, AHA) · AATS: 3–5 (unit as printed varies, frequency not stated)	AHA 2013 Table 3; CHEST 2012 1.5; AATS 2026
Clopidogrel	0.2–1 mg/kg/day	AHA 2013 Table 3

Starting doses, holds before procedures, DOAC labels

Starting doses (AHA 2013 Table 3; CHEST 2012 Table 5): UFH therapeutic 28 U/kg/h under 12 months, 20 U/kg/h from 12 months (AHA). Enoxaparin, therapeutic (initial treatment dose) every 12 h: 1.5 mg/kg per dose under 2 months, 1.0 mg/kg from 2 months (AHA ≥2 mo; CHEST >2 mo); neonates may need higher doses (AHA 2013, AATS 2026). Enoxaparin, initial prophylactic dose every 12 h: 0.75 mg/kg per dose under 2 months, 0.5 mg/kg per dose over 2 months (CHEST Table 5). Warfarin load 0.2 mg/kg/day, after Fontan 0.1 mg/kg/day (AHA).
Approximate hold before a moderate- or high-bleeding-risk procedure (AATS 2026 Table 9; longer with renal impairment or high bleeding risk): UFH 4–6 h; LMWH 12–24 h; bivalirudin 2–3 h; argatroban 8–10 h; rivaroxaban 6–10 h; apixaban 24–48 h; dabigatran 36–72 h; edoxaban no infant data; warfarin 3–5 d; aspirin 5–7 d; clopidogrel 5–7 d; dipyridamole 24–48 h. Bridging is not typically used for DOACs. AHA 2013: aspirin commonly stopped 7 d before surgery; LMWH held 24 h.
DOACs, US-labelled pediatric uses as AATS 2026 Table 3 states them: dabigatran, VTE treatment after at least 5 d of UFH or LMWH and secondary prophylaxis (3 months to <12 y); rivaroxaban, VTE treatment after at least 5 d of UFH or LMWH and thromboprophylaxis after Fontan surgery from >2 y; apixaban, VTE treatment after at least 5 d of UFH or LMWH; edoxaban, not approved in children. None should be used in infants with mechanical valves or antiphospholipid syndrome.

Key points

Systemic-to-PA shunt: aspirin indefinitely, with UFH (IIa) or bivalirudin (IIb) until it starts (AATS 2026, neonates and infants). CHEST 2012 also allows aspirin or no therapy (2C).
Norwood (HLHS) (Sano): aspirin indefinitely; consider UFH (IIa) or bivalirudin (IIb) if aspirin cannot start within 48 h (AATS 2026).
Glenn: sources differ on early UFH (AATS 2026: none, IIa; CHEST 2012: UFH, 2C). Long term: aspirin, Class I (AATS 2026); antiplatelet therapy, IIb (AHA 2013).
Fontan: aspirin or anticoagulation; adults with known or suspected thrombus, atriopulmonary Fontan, prior thromboembolism or sustained atrial flutter or fibrillation need anticoagulation (ACHD 2025, Adult).
Mechanical valve: VKA for life; INR 2.5–3.5 mitral; aortic 2–3 in infants (AATS 2026) or 2.5–3.5 with risk factors (AHA 2013). No DOACs in infants with mechanical valves (AATS 2026 Table 3).
Stents (neonates and infants): lower risk, aspirin for 6 months; higher risk (e.g. ductal stent for pulmonary blood flow, covered stent), therapeutic UFH or LMWH, then aspirin ± clopidogrel for at least 3–6 months (AATS 2026 Tables 6–7).
Lines: remove when no longer needed; treat symptomatic thrombosis, ≤3 months if provoked (ASH 2018).
Most rows are expert consensus and the drugs off-label in children; set intensity and duration against bleeding risk (AATS 2026 S19, IIa).

Sources and how this page was checked

Full text read

Nathan M, Kiskaddon AL, Emani S, et al. 2026 American Association for Thoracic Surgery (AATS) expert consensus statement: antithrombotic management of neonates/infants undergoing cardiac interventions. J Thorac Cardiovasc Surg 2026;172(3):618-662.e7. doi:10.1016/j.jtcvs.2026.03.617. Publisher PDF, including Tables 3, 4, 6, 7 and 9 and the Delphi worksheet (34 statements, modified Delphi; classes I–III, levels A to C-EO).
Giglia TM, Massicotte MP, Tweddell JS, et al. Prevention and treatment of thrombosis in pediatric and congenital heart disease: a scientific statement from the American Heart Association. Circulation 2013;128(24):2622-2703. doi:10.1161/01.cir.0000436140.77832.7a. Archived publisher copy (2026), which carries a correction notice; the correction itself (Circulation 2014;129(2):e23) was not available to read.
Monagle P, Chan AKC, Goldenberg NA, et al. Antithrombotic therapy in neonates and children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest 2012;141(2 Suppl):e737S-e801S. doi:10.1378/chest.11-2308. Archived open-access PDF (PMC3278066), checked against a 2026 archived copy of the PMC full text. Two 2014 corrections: Chest 2014;146(6):1694 (doi:10.1378/chest.14-2560) changes recommendation 2.11 (UFH through peripheral arterial catheters) to 5 units/mL at 1 mL/h, not 0.5; Chest 2014;146(5):1422 (doi:10.1378/chest.14-2167) changes the Table 6 VKA maintenance band 1.15–1.9 to 1.5–1.9, and Crossref links it to the 8th edition. Neither value is used on this page. The correction notices themselves were not read; the corrections are as listed by CHEST.
Monagle P, Cuello CA, Augustine C, et al. American Society of Hematology 2018 guidelines for management of venous thromboembolism: treatment of pediatric venous thromboembolism. Blood Adv 2018;2(22):3292-3316. doi:10.1182/bloodadvances.2018024786. Archived open-access copy (PMC6258911).
Rychik J, Atz AM, Celermajer DS, et al. Evaluation and management of the child and adult with Fontan circulation: a scientific statement from the American Heart Association. Circulation 2019;140(6):e234-e284. doi:10.1161/CIR.0000000000000696. Archived publisher copy; Thrombosis section and Table 18.
Gurvitz M, Krieger EV, Fuller S, et al. 2025 ACC/AHA/HRS/ISACHD/SCAI guideline for the management of adults with congenital heart disease. Circulation 2026;153(8):e115-e251 (also J Am Coll Cardiol 2026;87(7):822-976). doi:10.1161/CIR.0000000000001402. Archived publisher copy with the Fontan recommendation-table image; its correction concerns the byline only. Adult.
McCrindle BW, Michelson AD, Van Bergen AH, et al. Thromboprophylaxis for children post-Fontan procedure: insights from the UNIVERSE study. J Am Heart Assoc 2021;10(22):e021765. doi:10.1161/JAHA.120.021765. Open access; its correction concerns the byline only.

Abstract only

Payne RM, Burns KM, Glatz AC, et al. Apixaban for prevention of thromboembolism in pediatric heart disease. J Am Coll Cardiol 2023;82(24):2296-2309. doi:10.1016/j.jacc.2023.10.010.
Portman MA, Jacobs JP, Newburger JW, et al. Edoxaban for thromboembolism prevention in pediatric patients with cardiac disease. J Am Coll Cardiol 2022;80(24):2301-2310. doi:10.1016/j.jacc.2022.09.031.
Derridj N, Linglart L, Lasne D, et al. Thromboprophylaxis in congenital and acquired heart disease across the lifespan. A French consensus position statement: Part 1, from infancy to adolescence. Arch Cardiovasc Dis 2026. doi:10.1016/j.acvd.2026.07.005. Its graded recommendations are not reproduced; Part 2 (adolescence to adulthood, doi:10.1016/j.acvd.2026.07.006) likewise.

How it was checked

Agents, doses, targets, durations, classes and levels are copied from the sources (November 2026); wording is condensed. Doses appear only as printed; nothing is calculated. Each table keeps its source’s grading: AATS 2026 CoR I, IIa, IIb, III with LoE A, B-R, B-NR, C-LD, C-EO; AHA 2013 Class I, IIa, IIb, III with LOE A–C; CHEST 2012 Grades 1A–2C; ASH 2018 strong or conditional with certainty of evidence; ACHD 2025 COR 1, 2a, 2b, 3 with LOE. Terms follow each source (mBTT, MBTS, PTFE shunt; CVC, CVL, CVAD; BCPS, superior cavopulmonary anastomosis).
Convention: the newest society document leads. AATS 2026 for neonates and infants; AHA 2013 and CHEST 2012, the newest pediatric statements for older children, for lesions AATS 2026 does not cover (Fontan, older children’s valves) and alongside it where they differ; ASH 2018 for treating line-related thrombosis; ACHD 2025 for adults.
Rows shown: AATS 2026 Table 6 rows for the procedures above (44 graded cells) and statements S23, S24, S29, S30, S32 and S34; AHA 2013 §8.1, §9.1 (its effusion row under Glenn), §9.2, §9.3 and §13.3.1–13.3.2 in full; CHEST 2012 2.1, 2.4, 2.6, 2.22.1, 2.22.3, 2.22.6, 2.22.7, 2.31, 2.35, 2.36 and 2.37; ASH 2018 recommendations 1, 9, 10, 11, 13, 14 and 17; ACHD 2025 Fontan recommendations 12 and 13. 121 graded rows in all.
As printed, inside single sources: AATS 2026 prints S22’s level as B-R in the text and B-NR in the appendix and Table 6 (shown: B-NR); S26 and S27 grade the stent options differently from Table 6 (shown: Table 6, statements in the tip); the valve bivalirudin cells read “IIb-C-EO”; aspirin sits inside the I, A valve cells while S34 grades it IIb, C-EO; the PRU range is printed “∼50-200” in Table 4 and “∼50200” in the text. CHEST 2012 prints no grade for 2.40–2.42 (follow adult recommendations for prosthetic valves).
Between sources: each panel lists where they differ (shunt long term, Glenn early UFH and long-term aspirin, Fontan, mechanical aortic INR, aspirin with VKA, stent regimens, line removal, line prophylaxis, treatment duration). Aspirin: AHA 2013 and CHEST 2012 print 1–5 mg/kg/day; AATS 2026 prints 3–5 as mg/kg/dose (shunt text, S30 text), mg/kg/d (conduit text) and mg/kg (S34 text), with no frequency stated. Prophylactic LMWH anti-Xa ranges come from different settings (0.2–0.5 U/mL after stents, AATS 2026; 0.1–0.3 units/mL with a line kept after VTE, CHEST 2012).

Not covered on this page

Procedural anticoagulation for diagnostic catheterization, cardiopulmonary bypass and ECMO; heparin-induced thrombocytopenia; thrombolysis doses; arrhythmia, cardiomyopathy, pulmonary hypertension and stroke rows of AHA 2013 and CHEST 2012; other AATS 2026 Table 6 procedures (pulmonary artery band, septostomy, arch repair, tetralogy, arterial switch, ALCAPA, coronary unroofing, septal defects, TAPVR, Ebstein, Ross/Konno, transplant); DOAC trial dosing; adult valve targets (ACHD 2025 gives none). Kawasaki disease: see Kawasaki Coronary Z-Scores.

Systemic-to-PA shunt (mBTT, central) and Norwood

Graded rows

Where sources differ

RV–PA conduit (including Sano)

Graded rows

Ductal or RVOT stent

Bidirectional Glenn, hemi-Fontan, comprehensive stage 2

Graded rows

Where sources differ

Fontan

Graded rows

Where sources differ

Mechanical valve

Graded rows

Where sources differ

Bioprosthetic or transcatheter valve

Graded rows

Endovascular stents and septal devices

Graded rows

Where sources differ

Catheter-related (CVL) thrombosis

Graded rows

Where sources differ

Kawasaki disease

Targets and doses as printed

Key points

Related on HeartCalc

Full text read

Abstract only

How it was checked

Not covered on this page