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Page 4 of 13 Misra et al. Vessel Plus 2022;6:32 https://dx.doi.org/10.20517/2574-1209.2021.104

In patients with adequate echocardiographic windows, the branch pulmonary arteries dimensions and RV
outflow tract size should be measured as this information can be useful in future surgical or catheter-based
[16]
intervention planning .

Recently, RV strain has been a topic of interest in evaluating RV function in patients with repaired TOF; 2D
RV global longitudinal strain less than -17% has been associated with reduced RV ejection fraction on
[17]
cardiac MRI . Three-dimensional speckle-tracking has also been utilized in order to evaluate dysynchrony
between the right and left ventricles in a patient with TOF .
[18]

Advantages
Transthoracic echocardiography is noninvasive and provides excellent information in pediatric patients,
especially those who have optimal acoustic windows for imaging. It is considered the first-line modality in
the diagnostic toolbox for evaluating patients with TOF . It has higher axial and lateral resolution than CT
[13]
[13]
and MR imaging . Besides, it provides excellent morphological definitions of heart valves and, in some
cases, coronary arteries. It can also provide usable hemodynamic data, including RV systolic pressure and
pressure gradients across RVOT . The left ventricle (LV) anatomy, dimensional measurements, and
[12]
function can reliably be obtained by 2D and 3D echocardiography.

Limitations
In some patients, especially adults with congenital heart disease, the right ventricular outflow tract and
pulmonary valve annulus may be difficult to see, especially in patients who have multiple previous
operations. Additionally, the RVOT is an anterior structure and is difficult to visualize for patients who have
had extensive revisions. For surgical planning purposes, measurements of the right ventricular outflow tract
and pulmonary valve dimensions are not entirely accurate, and it is preferred to have CT and/or MRI
imaging . The echocardiography is limited in defining RV dimensions and systolic function. It may not
[12]
reliably define branch pulmonary artery anatomy .
[13]

CARDIAC MAGNETIC RESONANCE IMAGING FOR EVALUATION OF REPAIRED TOF
Diagnostic role
Advances in MRI have made this modality an important tool for the evaluation of congenital heart disease.
Faster scanning techniques, high spatial resolution, limitless windows, lack of ionizing radiation, lack of
dependence on contrast material, and capability for functional imaging have made it a noninvasive
diagnostic tool of great potential in patients with repaired TOF.

Advantages
Cardiac MR is the single noninvasive modality that provides all the information needed (see below) in
patients with repaired TOF, which no other single modality has the capability to provide. It is a particularly
effective tool in patients with limited acoustic windows. It has a wide field of view covering and is capable of
[19]
imaging extra-cardiac blood vessels . It can provide all hemodynamic data needed for decision making.
For all these reasons, CMR has become the preferred method of noninvasive imaging in adult patients with
repaired TOF [19,20,21] .

Limitations
CMR, particularly in children, is not available in all centers. It is a time-intensive procedure and also an
expensive tool. In infants and children, there is a requirement for sedation/anesthesia to perform CMR,
limiting its wide applicability. CMR usually cannot be performed in patients with pacemaker and
ferromagnetic devices .
[13]