Tetralogy Of Fallot 2j425f

TETRALOGY OF FALLOT

INTRODUCTION • Most common cyanotic congenital heart defect • The main causes of „blue baby syndrome‟ in neonates • Usually occurs due to a primary malformation resulting in a cascade of effects that lead to other malformations • Many variations in malformationsevery case is unique, but the classic anomalies remain the same.

HISTORY

• First observed and described by Steno of Denmark in 1673 • Further elaborated by Sandifort in 1773 in a 12 year old boy so meticulously that Willis(1948) wanted the disease named as „Tetralogy of Sandifort‟ • Named after French physician Etienne-Louis Arthur Fallot who referred to it as „maladie bleue‟ and focused on the frequency of the disorder in cyanotic infants in various research papers in 1888

EPIDEMIOLOGY

• One of the most frequently occurring congenital heart disease. • 3.5 – 8 % of all congenital anomalies in the western world • 4.6% of all congenital anomalies in India; 21% of all congenital heart diseases. • Occurs approximately 1 in every 1000 live births • Slightly more common in males than females

Preoperative diagnosis (n=100). ASD, Atrial Septal Defect; DORV, Double Outlet Right Ventricle; PDA, Patent Ductus Arteriosus; TGA, Transposition of great arteries; TOF, Tetralogy of Fallot; VSD, Ventricular Septal Defect. Kasar P A et al. Heart Asia 2011;3:135-139

AETIOLOGY • Attributed to environmental or genetic factors or a combination of both • Mainly associated with a chromosome 22q11 micro-deletion (DiGeorge syndrome). • Associated with Down syndrome, Alagille syndrome, CHARGE syndrome, VACTERL syndrome. • Predisposing factors – advanced maternal age; diabetic mother; maternal alcoholism(foetal alcohol syndrome); rubella or other viral disorders during pregnancy; poor maternal nutrition; exposure to radiation; modern lifestyle in itself.

EMBRYOLOGICAL BASIS • Mainly occurs due to defective anterior deviation of the twisting of the truncus arteriosus • This leads to less than 180 rotation of conotruncal septum resulting in anterior malaignment of membranous portion of interventricular septum.

EMBRYOLOGIAL BASIS

Prior to Septation = 5th week of embryonic development Post Septation = 9th week of embryonic development

EMBRYOLOGICAL BASIS • May also occur due to the unequal division of the cardiac outflow tract due to malpositioning of the conotruncal ridges, resulting in large aorta and small pulmonary artery.

PATHOPHYSIOLOGY

Primary Four Malformation –hence the name „TETRALOGY OF FALLOT‟

Pulmonic Stenosis (RVOTO) • Also known as Right Ventricular Outflow Tract Obstruction (RVOTO) • A narrowing of the right ventricular outflow tract and can occur at the pulmonary valve(valvular stenosis) or just below the pulmonary valve(infundibular stenosis). • Infundibular pulmonic stenosis is mostly caused by overgrowth of the heart muscle wall (hypertrophy of the septoparietal trabeculae), however the events leading to the formation of the overriding aorta are also believed to be a cause. • The pulmonic stenosis is the major cause of the malformations, with the other associated malformations acting as compensatory mechanisms to the pulmonic stenosis. • The degree of stenosis varies between individuals with TOF, and is the primary determinant of symptoms and

severity.

• This malformation is infrequently described as subpulmonary stenosis or subpulmonary obstruction.

“Overriding Aorta”

• The aorta, the main artery carrying blood out of the heart and into the circulatory system, exits the heart from a position overriding the right and left ventricles. • An aortic valve with biventricular connection, that is, it is situated above the ventricular septal defect and connected to both the right and the left ventricle. • The degree to which the aorta is attached to the right ventricle is referred to as its degree of "override." • The aortic root can be displaced toward the front (anteriorly) or directly above the septal defect, but it is always abnormally located to the right of the root of the pulmonary artery. • The degree of override is quite variable, with 5-95% of the valve being connected to the right ventricle.

Ventricular Septal Defect (VSD) • Anatomical Hallmark of Tetralogy of Fallot is the anterior malalignment of

the infundibular septum

• This results in a ventricular septal defect is centered around the most superior aspect of the ventricular septum (the outlet septum) • In the majority of cases the VSD is single and large. • In some cases thickening of the septum (septal hypertrophy) can narrow the margins of the defect.

Right Ventricular Hypertrophy • The right ventricle is more muscular than normal • Due to the misarrangement of the external ventricular septum, the right ventricular wall increases in size to deal with the increased obstruction to the right outflow tract. • This feature is now generally agreed to be a secondary anomaly, as the level of hypertrophy generally increases with age.

SIGNS AND SYMPTOMS • Various degrees of cyanosis may be present at birth or may appear later during infancy or childhood as a result of progression of the pulmonary stenosis. • Spells of paroxysmal sudden cyanosis and syncope – „Tet spells‟

SIGNS AND SYMPTOMS • Toddlers tend to occupy squatting position more often to decrease venous return to heart, especially during Tet spells,to increase systemic vascular resistance and allows for temporary reversal of the shunt.

SIGNS AND SYMPTOMS • Adults show pronounced digital clubbing of finger nails with cyanotic nail beds with tetralogy of Fallot

DIAGNOSIS • Physical examination: 1. Normal S1 and single loud S2 secondary to a more anteriorly located aorta 2. Systolic ejection murmur at left upper sternal border secondary to RVOTO

DIAGNOSIS • Chest radiograph: Right aortic arch (30%), decreased pulmonary vascular markings, bootshaped heart (coeur en sabot) with concave main pulmonary artery (PA) segment

DIAGNOSIS • Electrocardiography: Right axis deviation (+90–180°), RVH

DIAGNOSIS

•

Echocardiography: Anterior malalignment VSD, infundibular stenosis, overriding aorta, RVH. May also see: Other (muscular) VSDs, valvular pulmonary stenosis and/or branch PA stenosis, abnormal (right-sided) aortic arch anatomy, coronary artery anomalies

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This still frame of a modified parasternal long axis view demonstrates the large ventricular septal defect, aortic override, and right ventricular hypertrophy charactistic of patients with tetralogy of Fallot.

This still frame image of a parasternal short axis view of the echocardiogram of a patient with tetralogy of Fallot demonstrates the antero-cephalad deviation of the outlet septum into the right ventricular outflow tract.

DIAGNOSIS

• Cardiac catheterization: Generally not indicated unless concern is present regarding branch PA anatomy, coronary anatomy, or multiple additional VSDs that need to be defined before surgery

TREATMENT Emergency management of Tet spell 1. Knee-chest position 2. Oxygen(100%) 3. Morphine sulfate (0.1 mg/kg IV or IM) 4. IV fluid bolus and/or NaHCO 5. Beta-blocker (esmolol infusion for immediate therapy, propranolol for long-term prophylaxis) 6. Phenylephrine (0.02 mg/kg IV)

Preoperative

1. Polycythemia: Oral iron supplement for iron deficiency to avoid microcytosis 2. Beta-blocker for “tet spell” prophylaxis 3. Subacute bacterial endocarditis (SBE) prophylaxis

Surgery Palliative

Corrective

Blalock–Taussig systemiulmonary shunt

VSD patch closure and right ventricular outflow tract reconstruction (either an RV-to-PA conduit or a patched reconstruction of the MPA segment)

Complications1. Right ventricular dysfunction and ventricular arrhythmia 2. Postoperative sudden death (ventricular arrhythmias and/or complete heart block) 3. Exercise intolerance and dyspnea due to severe RV dilatation/dysfunction in the setting of PI

Knee-chest position.

Placing the child in the knee-chest position either lying supine or over the parent‟s shoulder

Blalock-Taussig shunt

PROGNOSIS • • • • • • • • •

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• • • •

Generally good if condition treated surgically in a timely manner: >90% of children with TOF are expected to survive to adulthood. Surgical mortality is low in most centers: 5-year survival >95%, 20-year survival ~94% Long-term quality of life in adulthood is comparable with that of the general population. Young patients with TOF have a greater risk of requiring additional help in school. Residual hemodynamic abnormalities are quite common Pulmonary insufficiency (PI) is common with transannular patch repair: Residual RVOTO(residual right ventricular outflow track obstruction) may occur. Right ventricular dysfunction +/− ventricular arrhythmias in adulthood from right ventricular volume overload secondary to PI In the setting of severe RV dysfunction and dilatation due to severe PI, some patients require surgical revision of the right ventricular outflow tract in adolescence or adulthood Left PA stenosis Residual VSD occurs rarely Conduction abnormalities (e.g., complete heart block, right bundle branch block [RBBB]) Supraventricular and ventricular arrhythmias

REFERNCES

• Schoenwolf G.C., Bleryl S.B., Brauer P.R., Francis-West P.H. Development of the heart. In “Larsen‟s Human Embryology”,4th ed. • Gray S.W., Skandalakis J.E. The Heart. In “Embryology for surgeons: the embryological basis for the treatment of congenital defects”,3rd ed. • Bailliard F., Anderson R.H. Tetralogy of Fallot: A Review. Orphanet Journal of Rare Diseases 2009, 4:2 doi:10.1186/1750-1172-4-2 • Pankajkumar A.K., Raghavan Nair S.K., Vellappillil R.K.

Somatic growth following congenital heart surgery in economically underprivileged children. Heart Asia 2011; 3:135-139 doi.

• Tetralogy of Fallot. A.D.A.M. Medical Encyclopaedia. U.S. National Library of Medicine. • Tetrallogy of Fallot: An Overview – eMedicine.

emedicine.medscape.com/article/2035949-overview • Tetralogy of Fallot – Wikipedia. en.wikipedia.org/wiki/Tetralogy_of_Fallot