Imaging Diagnosis Of Tetralogy Of Fallot

Ministry of Health of the Republic of Moldova

State University of Medicine and Pharmacy

"Nicolae Testemițanu"

Faculty of General Medicine II

Department of Radiology

Imaging diagnosis of Tetralogy of Fallot (TOF)

Diploma Thesis

Student: Salam Abd Elghany.

Group: 1050

Academic adviser:

MD, PhD, Associated Professor

Chișinău, 2016

Contents.

Chapter I.

1. Introduction 3

Purposes and objectives of the thesis 4

Chapter II.

2. Bibliographic review and analysis 5

2.1. Definition 5

2.2. Prevalence of Tetralogy of Fallot 6

2.3. Symptoms

2.4. Etiology

2.5. Risk factors

2.6. Complications

2.7. Tests and diagnosis

2.8. Differential diagnosis

2.9. Treatment

3. Ongoing care

Chapter I.

Introduction.

Actuality and level of study of the investigated topic;

This thesis is a pre-graduate, self-made project of a 6th year medical student level, which is entirely based on actual data and real information derived from authentic and authorized resources and references.

Purposes and objectives of the thesis

Through this thesis, I’m going to overview and highlight the main diagnostic imaging (imaging studies) of one of the most common cyanotic congenital heart defects, which is Tetralogy of Fallot, and to reveal the contributory beneficial role of each radiological investigation method in the diagnosis of this disease.

The diagnostic imaging methods we are going to discuss in this thesis are :

Chest X-ray (CXR). 

Echocardiography (echo). 

MRI.

Before sliding into bibliographic review and analysis chapter to discuss in more details, let’s take first a quick synopsis about the subject; “Tetralogy of Fallot”.

Tetralogy of Fallot (TOF): is a complex form of congenital heart disease first described by Neils Stensen but was identified as a clinical entity by Arthur Louis etienne Fallot. TOF is classified as a cyanotic heart disorder, because tetralogy of Fallot leads to inadequate flow of blood into lungs for the process of oxygenation (right to-left shunt) (see Fig.1.1).

Patients with tetralogy of Fallot initially present with cyanosis shortly after birth, thereby attracting early medical attention.

Conclusion:

The imaging studies; chest x ray (CXR), echocardiography (Echo) and magnetic resonance imaging (MRI) are considered to be the most effective diagnostic imaging studies in investigating the most common cyanotic congenital heart disease “Tetralogy of Fallot”, through this thesis I’m going to demonstrate and illustrate the diagnostic importance and necessity of each method in revealing and confirming the diagnosis of the tetrad complex “Tetralogy of Fallot”.

Fig.1.1

Chapter II.

Bibliographic review and analysis.

Definition & Overview of TOF

TOF is a rare congenital heart condition consists of a complex of four heart abnormalities that are present at birth. This complex of defects, affect the function of the heart, causing insufficient (poor) oxygenated blood being ejected out of the heart towards the rest of the body resulting in cyanosis.

Infants and children with TOF, usually have a blue-tinged skin because their blood carry insufficient amount of oxygen.

TOF occurs in 3-6 infants for every 10,000 births, and is the most common cause of cyanotic congestive heart failure (CHD). This disorder accounts for one third of all CHD’s in patients younger than 15 years.

In most cases, TOF is sporadic and non-familial. The incidence in siblings of affected parents is 1-5%, and it occurs more commonly in males than in females. This disorder is associated with extracardiac anomalies e.g.; cleft of lip and palate, hypospadias, and skeletal and craniofacial abnormalities.

Genetic studies have indicated that in some patients with TOF, there is an association with genetic syndromes, they include; 22q11 deletion syndrome previously known as DiGeorge/Velocardiofacial Syndrome (VCFS) and Allagile Syndrome which is associated with a deletion of chromosome 20p12 or the mutation of JAG 1 gene.

The Baltimore-Washington Infant Study (BWIS) conducted between 1981-1982 is the most recent and probably the most accurate study that assess the prevalence of the different subgroups of TOF. According this study the overall prevalence of TOF was 0.33 per 1000 live births, accounting for 6.8% of all forms of congenital heart diseases.

Risk factors, etiology and pathogenesis.

TOF occurs during fetal growth, when developing the fetus heart. Factors such:

A mother viral disease during pregnancy, such as rubella.

Maternal alcoholism.

Maternal poor nutrition.

A mother older than 40 years.

One parent suffers of TOF.

Babies who are born with pathological syndromes such Down’s syndrome or DiGeorge syndrome.

may increase the risk of this condition, however in most cases the etiology of TOF still unclear (idiopathic).

Etiology and pathogenesis: The four defects that build up the TOF’s complex are;

Pulmonary valve stenosis. It’s a narrowing of the pulmonary valve, that separates the right ventricle from the pulmonary artery (the major blood vessel flows into the lungs). Narrowing (stenosis) of the pulmonary valve lowers the blood flow into lungs. It may also affect the muscle structure below the pulmonary valve.

Ventricular septal defect. This is a hole in the wall that separates the two ventricles of the heart. This hole allows deoxygenated blood inside the right ventricle (blood that has circulated already over the body and is in his way to the lungs to re-enrich it with oxygen) to leak into the left ventricle allowing mixing with the fresh oxygenated blood from the lungs. Blood from the left ventricle also leaks back into the right ventricle leading to dilution of the oxygenated blood supply towards the body which results eventually in an impaired heart function.

Overriding aorta.  In TOF, the aorta is shifted slightly to the right (dextroposition) laying directly above the ventricular septal defect. By this congenital abnormal position, the aorta receives directly the blood from both ventricles (instead from left ventricle only), which is already mixed or diluted (as we mentioned above) because of the ventricular septal defect.

Right ventricular hypertrophy. When the heart's pumping function is overworked (to compensate the improper oxygen delivery), it causes enlargement (hypertrophy) and thickening in the muscular structure of the right ventricle wall. Over time this may cause stiffening or hardening of the heart which becomes weaker and eventually fails.

Rarely, some babies with TOF will have another hole between the heart's atria (atrial septal defect), as well. When this happens, the condition is known as pentalogy of Fallot.

Symptoms and clinical presentation.

Symptoms of TOF vary, depending on the degree of blood flow obstruction which is expelled out of the right ventricle towards the lungs. Signs and symptoms may include:

The skin’s bluish discoloration is caused by a low-oxygenated blood flow to the body’s tissues (cyanosis).

Dyspnea and hyperventilation (more prominent during feeding).

Syncope.

Poor weight gain.

Fatigue easily on exertion.

Irritability.

Prolonged crying.

Physical findings (clinical presentation) include the following:

Most infants are smaller than expected for age

Cyanosis of the lips and nail bed is usually pronounced at birth

After age 3-6 months, the fingers and toes show clubbing

During cyanotic episodes, murmurs may disappear

In individuals with aorto-pulmonary collaterals, continuous murmurs may be auscultated

A crescendo-decrescendo systolic murmur which is heard usually along the 2nd or 3rd left intercostal space as a sign of pulmonary stenosis. The intensity of the murmur may vary in correlation with the degree of the stenosis.

Treatment for Tetralogy of Fallot (operative and post-operative).

In TOF, surgery is the only effective treatment. The two types of surgery that may be performed in TOF are;

1) Intracardiac repair (most babies and children will have this procedure).

2) A temporary procedure that uses a shunt (bypass).

Intracardiac repair.

Intracardiac repair in TOF for most babies consists of a type of open-heart surgery. This surgery is usually performed during the first year of life. Through this procedure, the surgeon places a patch over the ventricular septal defect to close the hole between the ventricles. Surgeon also repairs the narrowed (stenotic) pulmonary valve and widens the pulmonary arteries in purpose to increase blood flow into the lungs. After intracardiac repair, the oxygen level in the blood increases and the baby's symptoms will be diminished.

Temporary surgery.

Occasionally babies need to undergo a temporary surgery before having intracardiac repair. If the baby was born prematurely (pre-term) or has pulmonary arteries that are underdeveloped (hypoplastic), surgeons will perform a bypass (shunt) between the aorta and pulmonary artery. This bypass allows increased blood flow into the lungs. (When the baby is ready for intracardiac repair, the shunt is removed).

After the surgery (post-operative).

Despite that most babies do well after intracardiac repair, but complications still possible. Such complications are; chronic pulmonary regurgitation (in which blood leaks back through the pulmonary valve), and an irregular heartbeat rhythm (arrhythmia).

Sometimes blood flow to the lungs remains restricted after intracardiac repair. Infants or children with those complications may require another surgery, and in some cases, the pulmonary valves may be replaced by artificial valves. Pulmonary valve replacement sometimes isn't necessary until decades after the original surgery. Besides, as with any other surgery, there's a risk of infection, unexpected bleeding or thrombotic disorders.

Arrhythmias are usually treated with medications, but some patients may need a pacemaker or implantable defibrillator later during the life.

Complications can continue throughout patient’s childhood, adolescence and adulthood. The child will need lifelong medical follow-up to monitor and treat any complication.

Complications.

All babies with TOF need a corrective surgery. Without treatment, the baby may not grow and develop properly. He or she will be also at high risk of serious complications, such as infective endocarditis (inflammation of the inner lining of the heart caused by a bacterial infection).

The severe complications which may develop the untreated cases of TOF over time may result in their death or a disability during the early adulthood.

Conclusion:

From all what was mentioned till now, we can extrapolate that Tetralogy of Fallot is a congenital (since born) cyanotic heart disease, in which the affected newborns can be easily observed and suspected for “TOF” due to their cyanosis which is manifested shortly after birth.

Despite the fact that “TOF” may be associated with some risk factors which may elevate the disease risk potential, however it still of unknown etiology.

TOF patients should be treated and managed soon after birth (during the 1st year of life) through undergoing a corrective surgery to improve their thrive and development and of course to avoid the severe complications which may result in their early death.

Chapter III.

Materials and methods of the research.

In this chapter I’m going to introduce and explain/define each one of the three imaging studies I’m investigating in my thesis, and to highlight the role (advantages, disadvantages/limitations and findings) of each of them in establishing the diagnosis of TOF.

Shortly, after a newborn is being delivered, physician may suspect TOF if the baby has blue-tinged skin or if an audible heart murmur (an abnormal whooshing sound caused by turbulent blood flow) presents in the child's chest.

To confirm the diagnosis of TOF must be performed the following several tests.

Chest X-ray (CXR). The typical sign of TOF on chest X-ray is "Coeur en sabot” (boot-shaped heart), resulted from the enlarged right ventricle.

Echocardiography (echo). Echocardiograms use high-pitched sound waves, inaudible to the human ear, in order to produce an image of the heart. Sound waves bounce off the baby's heart and produce moving images are viewed on a video screen. This test helps to diagnose TOF, because it allows seeing if there is a ventricular septal defect, abnormal structure of the pulmonary valve, improperly functioning right ventricle, and abnormally positioned aorta.

MRI. Provides fine delineation of the aorta, right ventricle out tract (RVOT), VSDs, RVH, and the pulmonary artery with its branches. It also can be used to measure intracardiac pressures, gradients, and blood flows.

Diagnostic tests; advantages, disadvantages (limitations) and their findings.

Plain chest x-rays, advantages disadvantages (limitations) and its findings

•it provides characteristic changes in the heart and pulmonary vasculature which can be shown on a plain chest film.

•it’s a fast, inexpensive, and non-invasive procedure.

• it can be useful in the follow-up of patients after surgical correction.

• Limitations: often, its findings are non-specific, plain films can’t allow visualization of intracardiac anatomy.

Findings on plain chest x-rays in TOF patients:

• Four (4) plain films of the chest may be obtained after barium administration to outline the esophagus texture, in order to obtain characteristic findings:

Frontal CXR

Lateral CXR

Other film findings

Echocardiogram advantages and disadvantages (limitations) and its findings

Two-dimensional Echo:

• It’s easily accessible, and relatively inexpensive.

• May be it’s the only imaging required to precisely diagnose TOF and its associated lesions.

• It can detect and display anatomic abnormalities; walls, valves motion, abnormal shunts, and intracardiac masses (vegetations, thrombi, tumors).

• Transesophageal echo is especially a useful procedure in identifying aortic and atrial anomalies.

In TOF, 2-D Echo is used in order to:

• establish the presence of associated anomalies,

• assess the severity of the obstruction of the right outflow tract.

• assess the size of the main pulmonary artery and its branches.

• determine the number and size of ventricular septal defects.

Limitations: provides a narrow field of view.

MRI advantages and disadvantages (limitations) and its findings

• It provides anatomic and functional imaging in arbitrary anatomic section.

• Spin echo provides the highest contrast resolution, but limited temporal resolution.

• Gradient reversal echo has limited contrast resolution but can be used to reconstruct images obtained from many short intervals of the cardiac cycle.

• Limitations:

It’s less accessible than an ultrasound, and is contraindicated in patients with metallic hardware or claustrophobia.

It’s more expensive than ultrasound, but also cheaper than angiography.

Conclusion:

Throughout what was introduced till here in this chapter, we can see that among the three imaging tests, there are some advantages which give the priority for one method rather than the other, as well as do the disadvantages (limitations).

Therefore and based on these facts we can deduce that the echocardiography is the “optimal” among the three, and emerges to be the most efficient test to start with and to obtain through it the majority of possible diagnosis about “TOF”.

Chapter IV.

Personal results and discussion.

In this chapter I’m going initially to show and demonstrate the film findings of each type of the three diagnostic imaging tests I’m investigating in my thesis, in order to enhance and support what we have discussed theoretically in the previous chapter by getting access into the field of practical investigation (real images).

Furthermore in this chapter, I’ll provide a table of differential diagnosis in “Tetralogy of Fallot” based on symptoms and diagnostic tests in purpose to distinguish this condition with other diseases may have similar presentation and diagnostic findings.

Later in this chapter we’ll see several tables showing variable numeral values of the heart chambers dimensions during systolic and diastolic phases, which describe the pre and post-operative changes in the size of each chamber, provided by echocardiography of patients with TOF which have had undergone a corrective surgery.

Chest X-ray (CXR). 

Frontal Chest X-Ray

Film findings:

• Mild cardiomegaly along

with narrowing of cardiac base

and a rounded elevated apex,

(red dashed curve).

• Right side positioned aorta,

(Yellow arrow).

• Concavity in the territory of

the main pulmonary artery

and diminished vascularity.

(blue arrow).

Fig.1.1

Lateral Chest X-Ray:

Fig.1.2

Other CXR film findings:

•A normal size of the heart.

• An elevation of the cardiac

Apex above the diaphragm

.(red arrow).

• Pulmonary vessels are

Diminished.

Fig.1.3 (4-years old boy)

• The classic "Coeur en sabot" (boot-shaped), cardiac silhouette (shadow) is resulted from the elevation of the apex due to right ventricular hypertrophy,

Combined with a concavity

In the territory of the main

Pulmonary artery (MAP).

• In summary: A cyanotic baby

With diminished pulmonary

Vascularity and a heart with a

Boot-shaped is highly

Suggestive of TOF.

Fig.6. (A baby with TOF)

Echocardiography (TTE).

Echo Findings:

1. VSD

2. Overriding

Aorta

Fig.2 (A pediatric patient, pre-operation)

Magnetic resonance imaging (MRI).

Findings on MR imaging in Tetralogy:

Fig.3.1 (40-years old woman with severe Tetralogy variant – pulmonary atresia and aorto- pulmonary collaterals)

Other MRI film findings:

1. Right ventricular

Hypertrophy.

2. Pulmonary stenosis.

3. Post-stenotic dilatation.

Fig.3.2 (22-year old man with uncorrected)

Differential Diagnoses based on symptoms and diagnostic tests.

Table.1. medial dimensions of left ventricle end diastolic diameter (LVEDd) in patients with TOF.

Table.2. medial dimensions of anterior-posterior diameter (A-Pd) of left atrium (LA) in patients with TOF.

Table.3. medial dimensions of superior-inferior diameter (S-Ad) of left atrium (LA) in patients with TOF

Table.4. medial dimensions of medio-lateral diameter (M-Ld) of left atrium (LA) in patients with TOF

Table.5. medial dimensions of right ventricle end diastolic diameter (RVEDd) in patients with TOF.

Table.6.medial dimensions of preoperative Aortic and Pulmonary valvular rings diameters in patients with TOF.

Conclusion:

As a summary at the end of this chapter I would like to summarize the whole mentioned above by this chapter in the same order as I’ve presented the data:

Chest radiographs have the following attributes:

Often normal initially

Diminished vascularity in the lungs and diminished prominence of the pulmonary arteries gradually become apparent

The classic boot-shaped heart ( coeur en sabot) is the hallmark of the disorder

Echocardiography has the following attributes:

Color-flow Doppler echocardiography accurately diagnoses muscular VSD, or atrial septal defect

Valvar alterations can be detected easily

MRI has the following attributes:

Provides good delineation of the aorta, RVOT, VSDs, RV hypertrophy, and the pulmonary artery and its branches 

Can also be used to measure intracardiac pressures, gradients, and blood flows

From differential diagnosis we can see narrow variations in the basics of clinical signs and symptoms, and diagnostic tests noted in the differentiation between TOF and other diseases. Pathophysiology in TOF primarily depends on the severity of the right ventricular (RV) outflow tract (RVOT) obstruction. RVOT obstruction determines the severity of right-to-left shunting, which is typical.

From tables we can observe the major role of the corrective surgery (intracardiac repair) in improving the patient symptoms by increasing the blood flow into and out of heart chambers (especially from right ventricle out into the small circulation) after closing the VSD (by placing a patch) and widening the pulmonary stenosis in which both ensure better oxygenation of blood returning from the body (great circulation) to heart besides no further mixture between left and right ventricles fillings.

Bibliographic references

http://www.mayoclinic.org/diseases-conditions/tetralogy-of-fallot/basics/definition/con-20043262

http://emedicine.medscape.com/article/2035949-overview#showall

http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/AboutCongenitalHeartDefects/Tetralogy-of-Fallot_UCM_307038_Article.jsp

http://www.nhlbi.nih.gov/health/health-topics/topics/tof

Baron M. “Plain film diagnosis of common cardiac anomalies in the adult” Radiologic Clinics of North America. 37(2):411-420. March

1999

Behrman: Nelson Textbook of Pediatrics, Sixteenth edition, Chapter 437 “Cyanotic congenital heart lesions: lesions associated with decreased pulmonary blood flow” pp. 1385-1395. 2000

Brickner E, Hillis D, Lange RA. “Congenital heart disease in adults” New England Journal of Medicine. 342(5):334-342. February 2000

Lilly: Pathophysiology of Heart Disease, Second edition, Chapter 3 “Diagnostic imaging and catheterization techniques” pp. 39-65. 1998

Wimpfheimer O. and Boxt L. “MR imaging of adult patients with congenital heart disease” Radiologic Clinics of North America.