© 2014, Wiley Periodicals, Inc.

DOI: 10.1111/echo.12437 Echocardiography

ECHO IN ADULT CONGENITAL HEART DISEASE

Echocardiographic Evaluation of Tetralogy of Fallot*

Pooja Swamy, M.D., Aditya Bharadwaj, M.D., Padmini Varadarajan, M.D., and Ramdas G. Pai, M.D.

Department of Cardiology, Loma Linda University Medical Center, Loma Linda, CA

Tetralogy of Fallot (TOF) is a cyanotic heart disease consisting of nonrestrictive ventricular septal defect,
overriding aorta, pulmonary stenosis, and right ventricular hypertrophy. Early total correction is the
treatment of choice and these patients with repaired TOF are increasingly seen in adult practice. This
review addresses echocardiographic evaluation of TOF, corrected TOF, its sequelae and various compli-
cations. A working knowledge of TOF assessment is essential for all adult cardiologists and sonogra-
phers. (Echocardiography 2015;32:40–48)

Key words: tetralogy of Fallot, echocardiography, pulmonary valve stenosis

Danish anatomist Neil Stensen was the first to center for congenital heart diseases may not be
identify the condition in 1672. It was, however, available.
Louis Arthur Fallot, who first described the ana- Hence, we outline the various key aspects of
tomical components and pathological features of the condition and its management through this
the condition. He called the condition “la mala- review on echocardiographic evaluation of TOF.
die bleue” (blue malady) or cyanose cardiaque
(cardiac cyanosis). Maude Abbott, a Canadian Etiology:
pioneer in pediatric cardiology used the term Its exact etiology remains unclear but has been
“tetralogy of Fallot” in 1924.1 Helen Taussig first associated with chromosomal anomalies includ-
postulated the progression of this condition ing 22q11 deletion syndrome (15% of TOF),
resulting in cyanosis and death to be secondary Down syndrome, trisomy 13 and 18, maternal
to diminished pulmonary blood flow. age >40 years, maternal diabetes mellitus, gesta-
Tetralogy of Fallot (TOF) is the most common tional exposure to hydantoin, retinoic acid,
cyanotic adult congenital heart disease with an rubella and alcohol (fetal alcohol syndrome),
incidence of 5 per 10,000 live births accounting maternal phenyl ketonuria, Alagille syndrome,
for 10% of all congenital cardiac malformations and cat eye syndrome. 22q11 microdeletion
and presents with equal gender prevalence. The (DiGeorge syndrome) is sporadic in 95% cases
prevalence of the condition is on the rise at the with remaining 5% being transmitted in an auto-
rate of 5% annually with the advent of successful somal dominant fashion.3 FISH testing is widely
corrective surgical procedures increasing the lon- available to test for this chromosomal abnormality
gevity of affected patients.2 When left untreated, and genetic counseling is offered in patients with
a survival of 30% has been noted in the first dec- TOF and other conotruncal anomalies. Mutation
ade of life that drops severely to a survival of 5% in coding region of GATA4/GATA6 (a gene encod-
after the fourth decade. Surgical correction has ing a zinc-finger transcription factor crucial for
proven to have a tremendous survival benefit in normal cardiogenesis) and mutations in the gene
these patients. coding for transforming growth factor b2 and
A thorough knowledge of the malformation JAG1 have been the most recently studied genetic
and the associated pathophysiological changes abnormalities to explain malformations in TOF.4,5
prior to and at various periods after reparative or
palliative surgery is crucial for a practicing cardi- Essential Components of TOF:
ologist. This is particularly true for the manage- There are four essential components of TOF. A
ment of a patient with TOF with cardiac or perimembranous ventricular septal defect (VSD),
noncardiac issues when support from a regional right ventricular outflow tract obstruction
(RVOTO), an overriding aortic root, and a hyper-
Address for correspondence and reprint requests: Ramdas G. trophied right ventricle.
Pai, M.D., Professor of Medicine, Loma Linda University
Medical Center, Loma Linda, CA 92354, Fax: 909-558-0903; It has been postulated that cluster of defects
E-mail: ramdaspai@yahoo.com caused by the anterior and cephalad migration
*[Corrections added on 26th June 2014, after first online pub- of the infundibular septum (or its fibrous
lication: article title was changed]

40
 Tetralogy of Fallot

remnant)6 while Van Praagh et al.1 believe that nary atresia. Right-sided arch occurs in about
these are caused by the underdevelopment of the one-fifth of patients.
subpulmonary infundibulum. The effective right- The overriding aortic root allows blood from
ward displacement the infundibular septum both ventricles due to the error in embryonic
results in a malalignment of the infundibular sep- septal migration. When there is moderate to
tum with respect to the trabecular septum. This severe obstruction of the right ventricular out-
narrows the right ventricular outflow tract result- flow tract, there is significant right to left contrib-
ing in a larger and overriding ascending aorta and uting to the blood flow into the aorta in addition
perimembranous VSD.6 Obstruction to right ven- to that from the left ventricle.6 Over a period of
tricular (RV) outflow results in RV hypertrophy.1,6 time, in unrepaired TOF, this volume overload
The anterocephalad deviation of the RV out- along with intrinsic structural abnormalities of
let septum and the failure of the outflow ventric- the aortic wall results in aneurysmal dilation of
ular cushion to muscularize results in an the aortic root. Aortic root dilatation can also be
infundibular septal defect (often perimembra- seen in repaired TOF attributed to the histologi-
nous type of VSD). The size of this defect is vari- cal changes (medionecrosis, fibrosis, cystic med-
able. When there is a nonrestrictive type of ial necrosis, and elastic fragmentation) in the
septal defect, it results in equalization of the aortic wall. Overriding of aorta is also seen in
pressures between both ventricles and an unre- context of a double outlet right ventricle. Right
stricted bidirectional flow between the ventri- ventricular hypertrophy develops as a conse-
cles. The impact of flow across the septum (or quence to the increased pressure overload
shunting) varies inversely with the degree of caused by the RVOTO and an overriding aorta.
RVOTO.
In a majority of patients posterior–inferior mar- Anatomical Variants of TOF:
gin of the opening between the ventricles is Some of the variants of TOF include:
formed by a fibrous continuity between the leaf-
lets of the aortic and tricuspid valves. The remnant (1) TOF with pulmonary atresia with or with-
of the inter-ventricular portion of the membra- out major aortopulmonary collaterals.
nous septum also forms this part of the VSD. (2) TOF with absent PV, bicuspid or unicuspid
In a minority of patients, the posteroinferior PV with or without pulmonary stenosis.
region of the defect is muscular and in such (3) TOF with double outlet right ventricle.
cases, the muscular tissue is formed by continuity (4) TOF with atrio-VSD.
of the posteroinferior limb of the septomarginal
trabeculation with the infundibular fold. This
structure protects the conduction axis in the ven- Associated Anomalies of TOF:
tricle during closure of the ventricular defect. The Tetralogy of Fallot may be associated with a vari-
failure of muscularization of the outlet septum ety of congenital anomalies due to the nature of
results in a fibrous band between the aortic and its development and the risk factors associated
pulmonary valves (PVs). This forms the anterosu- with its occurrence. These anomalies are summa-
perior margin of the septal defect some patients rized in Table II.
of Caucasian descent, from the Far East, Central, Anomalous anterior descending artery
and South America. deserves a special mention due to its surgical sig-
Right ventricular outflow tract obstruction is a nificance. It is seen in about 5–12% cases of
conotruncal developmental anomaly that occurs patients with TOF. Instead of arising from the left
in the 4th–5th week of embryonic development main coronary artery, it arises from the right cor-
of the heart. The level of outflow obstruction and onary artery and courses through the right
its severity can be variable. The levels of RVOTO ventricular infundibulum (RVOTO). The artery
can occur at one or more of the following levels: can be accidentally injured during the surgical
correction of infundibular obstruction resulting in
(1) Right ventricular infundibulum: atretic ischemia and arrhythmias. It is therefore essential
outflow tract to delineate the origin and course of the coro-
(2) PV: Bicuspid PV with supravalvular hypo- nary arteries prior to surgical correction in TOF.
plasia, subvalvular stenosis, or PV atresia At a similar note, it is equally important to realize
(with or without collaterals between sys- that the anticipated and rare complication of
temic and pulmonary vasculature) transection frequently results in inadequate
(3) Pulmonary artery RVOTO release.
(4) Branch pulmonary arteries
Natural History of TOF:
Bronchial collaterals (systemic to pulmonary) The variable severity of the condition and the
are seen with severe RVOT obstruction/pulmo- concurrence of the associated major intra-cardiac

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Swamy, et al.

anomalies determine the natural history or post- genated blood flow into the systemic circulation.
surgical long-term outcomes in adults with TOF. Central cyanosis is associated with varying
Without surgical intervention, 25% of the degrees of hypoxia, which if left untreated can
affected infants die in the first year of life with cause syncope and mortality.
mortality reaching up to 40% age of 3 years; Congestive heart failure is a common initial
70% by the end of first decade of life; and 90% presentation in infancy due to a large VSD while
by the end of 4th decade. progressive PS develops a picture more consis-
Major causes of death in surgically untreated tent with TOF.
patients include hypoxic spells (62%), cerebrovas-
cular accidents (17%), and brain abscesses (13%).
With early reparative surgery in these patients Evolutions of Surgical Corrections of TOF:
there has been a sharp decline in mortality in the It is important for the echocardiographer to
affected patients. As a result, we frequently understand the various surgical procedures per-
encounter patients in their adulthood presenting formed along with their time frames. In the year
with the complications of reparative or palliative 1944, Helen Taussig, a cardiologist Johns Hopkins
shunt surgeries. in collaboration with a surgeon, Alfred Blalock
and his able surgical assistant Vivien Thomas
Physiology: developed creation of an “artificial ductus arterio-
Ventricular septal defect in TOF is nonrestrictive sis” connecting the systemic circulation to the
leading to equal pressures in both ventricles. The pulmonary circulation to relieve cyanosis in chil-
direction and magnitude of flow through the dren with assumed TOF anatomy. This was a
defect depends on the severity of pulmonic ste- landmark in pediatric surgery and was the first
nosis. Moderate pulmonary stenosis (PS) is asso- type of palliative surgery which came to be
ciated with a net left to right shunt at the known as “Blalock–Taussig Thomas” (BTT) shunt.
ventricular level, and pulmonary flow exceeds This shunt established connection between the
systemic flow. More severe stenosis causes equal subclavian artery and the pulmonary artery.7 Very
resistance to outflow into pulmonary and sys- soon, the procedure became palliative not only
temic circuits that causes bidirectional shunting. for TOF but also for many other cyanotic congeni-
Severe obstruction to right ventricular outflow tal heart diseases. In 1946, Potts shunt was
causes a large right to left shunt with markedly reported. This was described as an anastomosis
reduced pulmonary blood flow. between the descending aorta and the left pul-
Factors that can cause reduced arterial oxygen monary artery. The procedure was later aban-
saturation are exercise-induced drop in systemic doned because of the difficulty in closing the
vascular resistance, hypercyanotic spells causing shunt at the time of complete repair. In 1962,
metabolic acidosis, and an increase in heart rate Waterston shunt was reported and described as
leading to increase in right to left shunt. anastomosis between ascending aorta to pulmo-
nary artery that was easy to perform and simple
Clinical Features and Diagnosis: to close. In 1966, Cooley shunt was reported. It
About half of the patients are diagnosed antena- was described as an intra-pericardial anastomosis
tally by a fetal echocardiogram during preg- from ascending aorta to right pulmonary artery.
nancy. The remaining patients are identified The Potts, Waterston, and Cooley shunts were all
upon their presentation with cyanosis early in central shunts and were less likely to thrombose
infancy or in the first few years of life. compared with the relatively peripherally placed
Cyanosis can be seen early in life or may BTT shunt. The modified BTT shunt used a pros-
develop later in life. Those who become cyanotic thetic tube graft interposed between the systemic
in adulthood typically have milder forms of the artery (subclavian artery) and the pulmonary
defect complex and or have a predominant left artery, instead of the direct anastomosis first
to right shunt mechanism until later in life. described. Surgeons in the current use this modi-
“Tet spells” or hypercyanotic episodes are fication for palliation.
more commonly observed in early childhood and It was only in 1954 that Walton Lillehei of Uni-
infrequently in adulthood. The spells are typically versity of Minnesota performed the first total
precipitated by agitation or decreased hydration. repair in 1954 using controlled cross circulation.
With a decrease in systemic vascular resistance This method used a single pump that controlled
(due to decreased hydration) or an increase in the reciprocal exchange between the patient and
pulmonary vascular resistance (resulting from the donor. The commonest long-term issue after
infundibular muscle obstruction or spasm during an intra-cardiac repair in TOF is progressive pul-
agitation or crying) a significant right-to-left monary regurgitation.
shunt across the VSD occurs. As a result, there is In 1955, at the Mayo Clinic, John Kirklin
decreased pulmonary flow and increased deoxy- and associates reported the use of a modified

42
 Tetralogy of Fallot

Gibbons CPB circuit (Gibbon-Mayo pump oxy- the PV is small a right ventricular outflow
genator) in the open repair of complex congeni- augmentation with placement of a transannular
tal heart defects including VSD and TOF with a patch is performed. Due to rapid growth in
60% survival rate.8 infancy and childhood, every attempt is made to
In 1970s, Bonchek and Starr evaluated the util- preserve the native PV when initial intra-cardiac
ity of surgical intervention in infancy. Among the repair is performed in infancy.
28 patients who had severe symptoms at the time When complete repair is performed in adult-
of diagnosis and underwent immediate complete hood, PV replacement is usually required if the
repair, the mortality was only 7%. Patient who native PV integrity is disrupted. In case of severe
received shunts at the time of diagnosis had a unresectable infundibular stenosis/pulmonary
mortality of 31% (pulmonary atresia or severe atresia or an anomalous coronary artery cruising
hypoplasia only). The study established the supe- through the infundibulum or RVOT, an extracar-
riority of complete repair at an earlier age.9 diac conduit with a right ventricle to pulmonary
artery connection is created.
Current Surgical Trend in TOF: It is noteworthy that though the anomalous
The timing of surgical repair is controversial and origin of left anterior descending artery from RCA
has been evolving over the years. Prior to 1970s, has been reported to vary from 5 to 12% in vari-
all patients with TOF mainly underwent palliative ous literatures, its occurrence is in real practice
surgery that involved creation of a pulmonary relatively rare. The complications arising from its
systemic shunt followed by delayed intra-cardiac transection during the RVOTO release is detri-
repair. After the 1970s, primary intra-cardiac mental though rare. The anticipation of this com-
repair became the treatment of choice in both plication during the procedure often results in
symptomatic and asymptomatic patients with incomplete or inadequate release of RVOTO.
TOF. For the exceptional cases with hypoplastic Over the years, materials used for surgical cor-
pulmonary arteries, small-sized left ventricular rection of right ventricular outflow obstruction
(LV), anomalous origin of left coronary artery, have included placement of homografts, bovine
multiple VSDs, the surgical techniques adopted jugular valved conduits (Contegra), stentless
in the treatment have evolved tremendously. valves, stented tissue valves, monocusp valves,
mechanical valves, autologous pericardial valves,
Palliative Surgery for TOF: and transcatheter PVs. In 2010, the US Food and
In the current era, palliative shunts are only per- Drug Administration formally approved the Med-
formed in those who are poor candidates for tronic Melody (Medtronic, Minneapolis, MN,
intra-cardiac repair. The goal is to increase pul- USA) Transcatheter Pulmonary Valve. This device
monary blood flow by creating systemic artery to is indicated for use as an adjunct to surgery in the
pulmonary artery connections. management of pediatric and adult patients with
the following clinical conditions:
Initial Repair for TOF:
Intra-cradiac surgical repair of TOF is usually per- (1.) Existence of a full (circumferential) RVOT
formed in the first year of life; in patients who conduit that was equal to or greater than
have undergone prior palliative surgery without 16 mm in diameter when originally
development of pulmonary arterial hypertension; implanted and
or in adults who have remained unoperated due (2.) Dysfunctional RVOT conduits with a clini-
to various circumstances. A complete TOF repair cal indication for intervention, and either
consists of two major components: regurgitation (>moderate) or stenosis
(mean RVOT gradient >35 mmHg).
Closure of the VSD: Closure is usually per-
formed with continuous polypropylene suture,
polyethylene terephthalate material, or Gore-Tex Adults with Corrected TOF:
(W. L. Gore and Associates, Inc., Elkton, MD, The long-term sequelae and complications of
USA) patch through either a transventricular or TOF that are surgically corrected are discussed as
transatrial approach. The complications include below. Table I summarizes these problems and
residual VSD or leak from around the patch. with suggested management. The sequelae and
Infundibular muscle may be resected if required. complications of TOF are summarized in
Inter-atrial communications are also closed with Table II.10
VSD closure. Atrial and ventricular scarring resulting in AV
block, atrial flutter, and/or atrial fibrillation, ven-
Relieving the RVOT obstruction: Resection of tricular tachycardia (sustained or nonsustained).
infundibular stenosis (with muscle resection if Chronic pulmonary regurgitation leads to
needed) is the most widely used method. When stretching of the right ventricular myocardium

43
Swamy, et al.

TABLE I
Surgical Procedures for Rerepair of Tetralogy of Fallot in Adults (Adapated from ACC/AHA guidelines – Warnes et al. (2008)10
Pulmonary valve replacement (PVR)
Heterograft (porcine or pericardial) or homograft
Mechanical PVR in patients who require warfarin anticoagulation for other reasons. This procedure has been associated with late
malfunction from pannus formation.
Patch augmentation of the pulmonary annulus for proper prosthetic valve sizing
Subvalvular obstruction or pulmonary artery stenosis
Resection of subvalvular obstruction and/or patch augmentation of the RVOT, pulmonary annulus, main or branch pulmonary
arteries
Usually occurs in combination with PVR
Residual/recurrent VSD closure
Direct suture
Patch revision
AVR (tissue or mechanical) for aortic regurgitation
Replacement of ascending aorta for dilatation
Tube graft
Bentall procedure (composite valve conduit with coronary reimplantation)
Aneurysm or pseudoaneurysm formation of RVOT
Resection and patch replacement
Atrial arrhythmias
Maze procedure or 1 of its modifications
Ventricular arrhythmias (ventricular tachycardia, ventricular fibrillation)
Preoperative EP testing and ablation in the catheterization laboratory
If unsuccessful, intra-operative mapping, and ablation are performed
Focus is most often in the RVOT between the VSD patch and the pulmonary annulus
Postoperative placement of an ICD for patients at high risk of sudden death
Tricuspid valve repair for significant tricuspid regurgitation
Tricuspid valve replacement for a markedly abnormal tricuspid valve Closure of residual PFO or ASD, especially if there is cyanosis,
history of paradoxical embolism, or anticipated need for a permanent pacemaker or ICD.

RVOT = right ventricular outflow tract; VSD = ventricular septal defect; ICD = intra-cardiac defibrillator; PFO = patent foramen
ovale; ASD = atrial septal defect.

resulting in areas of inhomogeneous electrical the key features for a comprehensive echocardio-
activity. Structural changes in the myocardium graphic examination.
along with scarring from reparative surgeries Transthoracic images should be obtained from
result in increased refractoriness that predisposes all standard views, especially the suprasternal
to reentrant electrical activity causing ventricular view. The latter is vital for the evaluation of the
arrhythmias. Right ventricular dysfunction and arch and its associated anomalies; systemic to pul-
dilatation is associated with right atrial dilatation. monary shunts and for estimating the size of the
Right atrial dilatation and scarring from repara- pulmonary artery branches.11 Parasternal views
tive surgeries result in a similar reentrant electrical are important for assessment of the RVOT, PV,
activity causing atrial fibrillation, atrial flutter, main pulmonary artery, VSD patch, ascending
and other sustained/nonsustained atrial tach- aortic size, and aortic valve (Figs. 4–5). The short-
yarhhythmias. axis view not only allows us to visualize the RVOT
but also determine the size and extent of the sep-
Echocardiographic Features of TOF: tal defect. As mentioned earlier, RVOTO can
In adults with unrepaired TOF, the key echocar- occur at various anatomic levels and the paraster-
diographic features are listed under main features nal short-axis and subcostal coronal views must
and associated anomalies (Figs. 1–3). In adults be used to meticulously evaluate each potential
who have undergone intra-cradiac surgical level of obstruction. While color Doppler is useful
repair, an echocardiographer should look for a in assessing the location of turbulent flow, contin-
residual VSD, pulmonary regurgitation with asso- uous-wave Doppler helps in determining pressure
ciated RV dilation/dysfunction, infundibular gradients across the various levels of obstruction.
stenosis, aortic root dilation, residual uncorrected Apical views are important for determining the RV
anomalies, hypoplastic pulmonary annulus, pul- size and function and the subcostal view allows
monary artery or its branches, or pulmonary visualization of the inferior venacava (IVC) size
artery branch stenosis. Complications related to and atrial septum. Sometimes when transthoracic
these may unfold over time. Table II summarizes images are suboptimal, a transesophageal echo

44
 Tetralogy of Fallot

TABLE II
Echocardiographic Findings in TOF

Repair-Related Findings or Long-Term

Uncorrected TOF Associated Anomalies Sequelae

Large unrestrictive Atrial septal defect and PFO in 10% of Blalock Taussing shunt or
perimembranous VSD patients.17 Commonly seen with modified BT shunt
Overriding aorta Down syndrome Glen Shunt and Waterston
(i.e., <50% override) Partial anomalous pulmonary venous shunt
Pulmonary stenosis drainage and pulmonary artery VSD patch and residual VSD
Right ventricular anomalies seen in 30% of infants Hypoplastic pulmonary annulus
hypertrophy Branch pulmonary vein or PA
stenosis-LPA in 40% Pulmonary regurgitation
Pulmonary valve anomaly- Pulmonary stenosis at, below
unicuspid or bicuspid pulmonary or above the valve
valve (in 60%) with/without Prosthetic pulmonary valve
annular stenosis RV to PA conduit and related
Right aortic arch in 25% issues
LAD from right coronary sinus Ascending aortic dilation and
with course anterior to RVOT in 10% aneurysm
Major aortopulmonary collaterals Aortic root dilatation and
seen in 5% of patients. Bronchial aortic regurgitation
collaterals LV systolic and diastolic
A left SVC draining into coronary dysfunction
sinus or rarely directly into the x RV and LV dilatation associated
left atrium with systolic and diastolic dysfunction
Noncardiac associations include RV outflow tract fibrosis
spinal and musculoskeletal anomalies RV aneurysm from outflow
tract patch or from ventriculotomy
Tricuspid regurgitation
AV scarring and arrhythmias
Endocarditis

VSD = ventricular septal defect; PA = pulmonary artery; RV and LV = right and left ventricular; LAD = left anterior descending artery;
PFO = patent foramen ovale.

A B

RV
Ao

LV

Figure 1. A patient with uncorrected tetralogy of Fallot

(TOF) showing a large membranous ventricular septal defect
(VSD) and overriding of the aorta denoted by the arrow.

may be needed for better anatomic and func-

tional evaluation of TOF.12 Transesophageal
echocardiographic exam is also pivotal for Figures 2. The flow across the ventricular septal defect
perioperative and intra-operative assessment dur- (VSD) is of low velocity as systolic pressures in LV and RV are
ing TOF intra-cardiac repair surgeries.12,13 equal because of nonrestrictive VSD.

45
Swamy, et al.

A: TR B: TR

RV RV

LV LV
LV
RA

Figure 5. Small residual ventricular septal defect (VSD)

which are common after tetralogy of Fallot (TOF) repair
Figure 3. Patients with tetralogy of Fallot (TOF) may have (arrow).
tricuspid regurgitation (TR). This patient had severe TR with a
TR velocity of 5.3 m/sec suggesting systemic level of RV sys-
tolic pressure, which results because of severe pulmonary ste-
nosis
A B

RV

Figure 6. A. shows a parasternal short-axis view with color

flow in early diastole showing wide open PR (arrow) in a
patient with tetralogy of Fallot (TOF) repair. B. shows the
AO capillary wedge signal. Note rapidly decelerating PR signal,
which is common in severe PR.
LV
branches, or pulmonary artery branch stenosis.
From the parasternal long-axis view, the VSD
LA patch is seen as a linear structure passing obli-
quely from the septum to the anterior aortic root.
Doppler imaging is very useful in detecting resid-
ual shunting at the margins of the VSD patch,
residual RVOTO and its location and severity, and
pulmonary regurgitation. Complications related
Figure 4. Parasternal long-axis view in a patient post–tetral-
to the surgical repair may unfold over time.
ogy of Fallot (TOF) repair. Note the ventricular septal defect Table II summarizes the key features for a com-
(VSD) patch denoted by the arrow. prehensive echocardiographic examination.
Three-dimensional echocardiography may
add incremental value to imaging if the baseline
In adults who have undergone intra-cradiac images are optimal for evaluation of the right
surgical repair, echocardiography plays a key role ventricular size and function. It also helps in iden-
in assessing the surgical results. The echocardiog- tifying vegetations on valves or pacemaker/defi-
rapher should look for a residual VSD, pulmonary brillator leads.
regurgitation with associated RV dilation/dys- One of the most vexing problems is determin-
function, infundibular stenosis, aortic root dila- ing the optimal timing of pulmonary valve repla-
tion, residual uncorrected anomalies, hypoplastic cement in adults with severe pulmonary
pulmonary annulus, pulmonary artery or its regurgitation (PR) relative to the impact of the

46
 Tetralogy of Fallot

A B

Figure 7. A patient who had a homograft for severe PR post TOF repair. Note the homograft A. mild stenosis on color flow B. and
capillary wedge signal C. showing mild pulmonary stenosis (PS) and moderately dense PR signal indicating significant PR in the pros-
thetic valve.

long-term PR on the RV size and function (Fig. 6). flow through both the left and right pulmonary
The hemodynamic burden of PR also increases arteries, and permits calculation of the size and
the likelihood of ventricular tachycardia arising function of the ventricles. However, the disad-
from the postventriculostomy scar. vantages of MRI are that it cannot be performed
Cardiac MRI is currently the imaging modality in adults with pacemakers or defibrillators and
of choice, given its accuracy and reproducibility contrast material cannot be administered in
in measuring RV size and function. It also allows patients with advanced renal failure. Cardiac CT
visualization of the extracardiac structures is useful for the evaluation of right ventricular
including the aorta and the conduits and permits size/function, assessment of aortic dilatation/
flow quantitation by using velocity-encoded cine aneurysm, extracardiac structures/conduits in
sequences. MRI is useful in measuring the pulmo- adults with devices that prohibit the current use
nary regurgitant fraction, provides information of MRI. Major drawbacks are that it is associated
regarding the ratio of pulmonary and systemic with both contrast and radiation exposure; and
blood flow through a VSD, the differential blood the temporal resolution is lower than cardiac

47
Swamy, et al.

MRI. Figure 7 shows a pulmonary homograft 2. Warnes CA: The adult with congenital heart disease: Born
replacement in an adult who had severe PR. Over to be bad? J Am Coll Cardiol 2005;46:1–8.
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nous VSD results from malalignment of the infun- tion during heart development. Trends Cardiovasc Med
2009;19:130–135.
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septum. The infundibulum is narrowed in almost diovascular phenotype and genotype-phenotype correla-
all patients with TOF. Other sites of obstruction tion in individuals with a JAG1 mutation and/or Alagille
are the PV which is abnormal in most cases. It syndrome. Circulation 2002;106:2567–2574.
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Fallot with pulmonary stenosis. Cardiol Young 2008;18
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