Anatomy and pathophysiology of tetralogy of Fallot

Yun Hee Chang

Division of Pediatric Cardiac Surgery

Department of Thoracic & Cardiovascular Surgery

Seoul St. Mary’s Hospital

Catholic University of Korea / Catholic Medical Center

History

1671

1777

1785

1793

1797

1812

1814

1816

1846

1881

1888

Niels Stensen

Eduard Sandifort

Willam Hunter

Pulteney

1784

Abernethy

Bell

Dorsey

J.P.Farre

Thaxter

Thomas Bevil Peacock

Widman

Fallot: La maladie bleue

1924

Maude Abbott: “tetralogy of Fal-lot”

4 Anatomic features(1) Pulmonary (or RV) outflow stenosis(2) Ventricular septal defect(3) Aortic overriding(4) Right ventricular hypertrophy

Subtypes of TOF

Tetralogy of Fallot, Pulmonary stenosis Tetralogy of Fallot, Absent pulmonary valve (3-6%) Tetralogy of Fallot, Common atrioventricular canal (2%)

Tetralogy of Fallot, Pulmonary atresia (20%)

TOF with Pulmonary stenosis

Anatomic features

Overriding of the aortaSubpulmonary stenosis

Ventricular septal defect Right ventricular hypertrophy

Van Praagh R et al. - Underdevelopment of the subpulmonary infundibulum

Normal TOF

Pathognomonic lesions

Anderson RH et al.

- Anterocephalad deviation of the outlet septum

(relative to the limb of the septomarginal trabeculation)

- Malformation of the septoparietal trabeculation

Normal TOF

A

P

Deviated outlet septum

Septal attachment of the muscular outlet septum

Antero-cranial limb of TSM

Hypertrophied Septoparietal trabeculation

Subvalvar stenosis

Infundibular stenosis - Essential part of tetralogy - Produced by the ‘Squeeze’

between the anterocephalad malalignment of the outlet septum and the abnormal situated septoparietal tra-beculations

Pulmonary outflow stenosis

Anterocephalad malalignment of the outlet septum without abnormal situated septoparietal trabeculations

* vs. Eisenmenger type ventricular septal defect

Additional muscular stenosis - By hypertrophy of the moderator band or by prominent apical tra-

beculations. - Often described as “two-chambered right ventricle”.

Moderator band

Apical trabeculations

-The pulmonary valve is stenotic in 75% cases : usually caused by hypoplasia and fusion of bicuspid leaflets, supravalvar tether-

ing. -The valve is bicuspid in ½ to 2/3 of cases. - The pulmonary valve annulus is invariably smaller than the aorta; however, it is not necessarily significant obstructive.

Valvar stenosis

-The main PA is usually somewhat diffusely small and is often short.- The narrowed portion of the main pulmonary artery is often at the sinotubular junction.

- Branch PA abnormalities occurred in only 10 % of cases.

Sinotubular junction

Supravalvar stenosis

Outlet from left ventricleInterventricular plane

Ventricular septal defect

Ventricular septal defect

3 important planes

Perimembranous defect - In about 4/5 of Caucasian patients - VIF stops short of the postero-caudal limb of TSM, permitting fibrous conti-nuity to exist between the leaflets of the aortic & tricuspid valves

Muscular out-let septumVentricular in-

fundibular fold

Remnant of the interventricular

membranous sep-tum

AV node

Right bundle branch

Left bundle branch

Postero-caudal limb of TSM

Types of ventricular septal defect

Ventricular infundibular fold

Septomarginal trabeculation

Septoparietal trabeculation

Aortic-tricuspid continuity

Muscular defect - In about 1/5 of Caucasian patients - Postero-caudal limb of the TSM fuses with VIF, permitting muscular continuity throughout the right ventricular margin of the defect.

Postero-caudal limb of TSM

Ventricular in-fundibular fold

Muscular outlet septum

Hypertrophied septopari-etal trabeculation

Right bundle branch

Left bundle branchAV node

Ventricular infundibular fold

Septomarginal trabeculation

Septoparietal trabeculation

Doubly committed & juxta-arterial defect - Commoner in the Far East and South America - Consequence of failure of formation of a complete muscular subpulmonary infundibulum

Ventricular in-fundibular fold

Fibrous continuity between the leaflets of the arterial valves

Postero-caudal limb of TSM

Unobstructed but relatively high-resistance systemic vascu-lar bed

Obstructed pulmonary outflow tract

Anatomic route of balance be-tween the two circulatory beds

RV hypertension

Normal or low PA pressure

Pathophysiology

Hypercyanotic spell

CatecholamineState of low intravascular volume stateCrying /feeding, etc

TOF with Pulmonary atresia

Anatomic features

- Confluent or non-confluent.

- Confluent in about 2/3 of the cases

- The caliber of the central PAs varies

: When the ductus or collateral arteries connect proximally to the central PAs or their lobar branches, the central vessels may be only mildly hypoplastic or even normal in size.

Atretic arterial segment

- Can be recognized as a solid elastic cord in about ¾ - Rarely only the PV is imperforate.

The central right & left PAs

“Entirely from the systemic circulation”. - Ductus arteriosus

- Systemic-to - pulmonary collateral arteries

- Coronary artery

- Plexus of bronchial or pleural arteries

The blood supply to the lungs

Systemic-to-pulmonary collateral arteries

Pulmonary arteries

Pulmonary atreisia

Patent ductus arteriosus

* Ductal & collateral sources may coexist in the same patients but only rarely coexist in the same lung segment.

Ductus arteriosus - Usually is a unilateral structure

- Associated with confluent PAs in > 80% of cases

- Rarely, bilateral ductus may occur with non-confluent arteries

- Because the ductus is widely patent during fetal life, the PAs may be a normal size at birth.

- Normal postnatal ductal narrowing usually occurs and produce distal stenosis in 35-50% of cases.

Patent ductus arteriosus

Pulmonary coarctation

Collateral arteries - Most commonly from the descending thoracic aorta

- Less commonly the subclavian arteries

- Rarely from the abdominal aorta

- Their number varies from 1 to 6

- Their diameter ranges from 1 to 20mm

- More stable source of pulmonary blood flow

- Anastomoses between the central PAs (or their branches) and the collateral arteries

: About 40% of subjects

: May occur at the hilum or within the lung

: In the remaining 60%, the collateral arteries enter the pul-monary hilum, travel with the bronchi as PAs

- Stenosis

: nearly 60% of collateral arteries

: tend to occur near the aortic or intrapulmonary anastomosis

: may be discrete or segmental

: may be congenital or acquired

- Ductus supplies confluent central PAs

: Intra-PAs of both lungs are normal

- Ductus supplies one of the non-confluent central PAs

: Contra-lateral lung usually has arborization abnormalities

- Ductus is absent

: Both lungs have arborization abnormalities

Intrapulmonary artery distribution

Classification- There is no standard classification system for PAVSD, but several have been pro-posed.- Most classification schemes focus on the patterns of pulmonary blood flow.

Congenital Heart Surgery Nomenclature and Database Project

Boston group

IIIa. Central pulmonary artery Z – score > -2.5IIIb. Central pulmonary artery Z – score < -2.5

Pathophysiology

One of Three Marked heart failure because of lung overflow Cyanotic because of reduced lung flow Fairly well balanced with systemic oxygen saturation in the high 70s to low 80s

Extrapulmonary collateral

Obstruction

Collateral stenosis

Intrapulmonary collateral has thin-walled elastic media

TOF with Absent Pulmonary Valve

Absence of ductus arteriosus

Pulmonary annular hypoplasia

Anatomic features

Dilated pulmonary arterial trees

Deviated muscular outlet septum

Rudimentary leaflets of PV

Pathophysiology Free pulmonary regurgitation throughout fetal life - Transmission of chronic volume load of the RV to PAs

Proximal PA : aneurismal dilatation

PA

Normal TOF with APV

Airway compression

Common atrioventricular canal

Anatomic features

Septoparietal trabeculations

Outlet septum

Pulmonary trunk

Aorta

Anterior papillary muscle

Common atrioventricular valve