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 Table of Contents  
ORIGINAL RESEARCH
Year : 2019  |  Volume : 3  |  Issue : 3  |  Page : 127-134

Impact of Ventricular Morphology on Myocardial Deformation in Patients with Single Ventricle


Department of Cardiology, Faculty of Medicine, Ain Shams University, Cairo, Egypt

Date of Submission16-Aug-2018
Date of Decision03-Nov-2019
Date of Acceptance24-Nov-2019
Date of Web Publication18-Dec-2019

Correspondence Address:
Dina Adel Ezzeldin
Department of Cardiology, Ain Shams University, Cairo
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiae.jiae_42_19

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  Abstract 

Introduction: Functional single ventricle represent a heterogeneous group of anomalies sharing a common feature which is a functional single cardiac chamber. (1) In different series of congenital heart disease patients, cases of UVH represent about 1–2% of total congenital heart diseases. (2) Two-dimensional speckle-tracking echocardiography has recently emerged as a novel technique for objective and quantitative evaluation of global and regional myocardial function. Objectives: To determine impact of ventricular morphology on myocardial deformation in patients with single ventricle. Patients and Methods: The study included 47 patients with functional single ventricle whether they underwent cavopulmonary anastomosis or not. All patients were referred for elective cardiac catheterization or follow up echocardiography in Ain Shams university hospitals, Cardiology department, from November 2017 to July 2018. All patients underwent full echocardiographic assessment including assessment of the dominant ventricular function by STE. Results: The study included 47 patients, 30 males (63.8%) and 17 females (36.2%). Their age ranged between 6-12 years, with mean age of 8.22 ± 1.94. The morphology of the dominant ventricle determined ventricular function by both 2D parameters and STE. Patients with a dominant LV had higher strain values. Patients who underwent a cavopulmonary shunt also had better ventricular functions. All patients included in the study showed impaired dominant ventricular function by STE even those who had normal EF by standard 2D TTE suggesting that subtle ventricular dysfunction in patients with single ventricle can be unmasked by STE.

Keywords: Single ventricle, speckle-tracking echocardiography, ventricular deformation


How to cite this article:
Ezzeldin DA, Yasmin AE, Shouman K, Atteya H. Impact of Ventricular Morphology on Myocardial Deformation in Patients with Single Ventricle. J Indian Acad Echocardiogr Cardiovasc Imaging 2019;3:127-34

How to cite this URL:
Ezzeldin DA, Yasmin AE, Shouman K, Atteya H. Impact of Ventricular Morphology on Myocardial Deformation in Patients with Single Ventricle. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2019 [cited 2020 May 29];3:127-34. Available from: http://www.jiaecho.org/text.asp?2019/3/3/127/273299


  Introduction Top


Single ventricle is a complex congenital heart disease. It represents 7.7% of congenital heart disease diagnosed in childhood and has a birth incidence of approximately 4–8/10,000.[1]

Functional single ventricle (FSV) is a spectrum of severe congenital heart disease, with multiple anatomic variations but similar surgical treatment strategies.

Studies have demonstrated differences between the behavior of the ventricles, according to different morphologies, which is expected due to the different fiber arrangement and geometry between left ventricular (LV) and right ventricular (RV).

Based on the morphological characteristics, most ventricles can be recognized as being morphologically right or left. In rare situations, there is only one ventricular chamber in the ventricular mass, with a trabecular pattern typical of neither left nor right ventricle (indeterminate or mixed ventricular morphology).[2]

Surgical palliation of FSV began in 1971 with the treatment of tricuspid atresia (TA), described by Fontan and Baudet. These surgical palliative techniques were then further refined in 1980 by Norwood, specifically in patients with hypoplastic left heart. Subsequently, many variations of surgical palliation have been built on these original techniques enabling neonates, who previously would have suffered significant morbidity and mortality, to have a 70% chance of survival into adulthood.[3]

And these surgical procedures include Glenn, Kawashima, and Fontan procedures but Glenn shunt is the most commonly used in case of single ventricle patients in Egypt.

Most children with single ventricle present as neonates. However, an increasing proportion of patients with functional univentricular heart (UVH) are diagnosed prenatally.

Advances in ultrasound technology and resolution have allowed accurate prenatal diagnoses of all forms of single ventricle.

No matter what the underlying ventricular anatomy, the adequacy of pulmonary and systemic blood flow will determine the timing and type of presentation.

Echocardiography has been the only imaging modality that allows dynamic imaging of the heart; it is only natural that researchers and manufacturers of ultrasound imaging equipment have driven new, increasingly automated techniques for sophisticated analysis of cardiac mechanics.[4]

Several such techniques have emerged over the past decades to address the issue of reader's experience and intermeasurement variability in interpretation. Some of them were widely embraced by echocardiographers around the world and became part of the clinical routine, whereas others remained limited to research and exploration of new clinical applications.[5]

Speckle-tracking echocardiography (STE) is a new, noninvasive method for the assessment of LV global and regional function. STE offers the opportunity to track myocardial deformation independently of both cardiac translation and the insonation angle. Before the advent of STE, the only technique for angle-independent assessment of LV deformation and rotation was tagged cardiac magnetic resonance (cMR). Although tagged cMR remains the reference method for the assessment of LV deformation, its use is limited by an inherent low frame rate acquisition, high cost, and time-consuming and complex data analysis. Recently, STE was proposed as an alternative method to assess LV deformation and torsion, and it has been systematically validated by reference to sonomicrometry, tagged cMR, and color-coded tissue Doppler echocardiography. Several studies have proven its accuracy and consistency.[6]


  Patients and Methods Top


The study included 47 patients with FSV whether they underwent cavopulmonary anastomosis or not. All patients included were referred for elective cardiac catheterization or followup echocardiography in Ain Shams University Hospitals, Cardiology Department, from November 2017 to July 2018.

Inclusion criteria

  1. All patients with single ventricle morphology or physiology, patients who were not fit for biventricular repair including TA, double-inlet left ventricle, double-outlet right ventricle with a small LV, unbalanced complete atrioventricular (AV) canal, pulmonary atresia with intact ventricular septum and a hypoplastic RV, and severe form of Ebstein's anomaly of the tricuspid valve referred to Ain-Shams University Hospitals for follow-up echocardiography or diagnostic cardiac catheterization
  2. Pediatric and adult patients were both included in the study, and the results were categorized according to body surface area.


Exclusion criteria

  1. Critically ill patients
  2. Patients with more than mild AV valve regurgitation.


All patients were subjected to the following:

History

Proper history taking

Age at presentation, age and weight at time of operation if done, duration after the shunt operation if shunt operation was done, assessment of functional capacity by New York Heart Association [NYHA] class and modified ross heart failure classification for children, history of previous interventions, for example, pulmonary artery (PA) stenting or venovenous collateral closure.

Clinical examination

As regards general and local examination, oxygen saturation tracking and cyanosis, signs of shunt dysfunction if present were noted.

Conventional two-dimensional echocardiography

Standard two-dimensional (2D) echocardiogram was performed using G.E echocardiography machine.

Sedation

In agitated infants and children, sedation with chloral hydrate aqueous solution (50 mg/kg) 15 min before the study was done.

Probe selection

A phased array S8-3 pediatric probe with frequency range from 8 to 3 MHz was used for infants below 1 year and a phased array S5-1 probe with frequency range from 5 to 1 MHz for infants older than 1 year and children.

Echocardiographic assessment

Sequential analysis

Two-dimensional and M-mode echocardiography (according to The American society of Echocardiography 2015 updated guidelines)

  1. Sequential analysis was applied for all patients to determine the situs, AV, and ventriculoarterial connections, great vessel relation and abnormalities, ventricular dimensions and functions, state of cardiac valves, venous connections, and any intracardiac shunts
  2. Description of AV connection as being double-inlet, atresia of one of the inlets, or a common AV valve, best viewed from subcostal and apical four-chamber views delineating the crux of the heart[7]
  3. The morphology of the dominant ventricle (right, left, or indeterminate), the location of the rudimentary ventricles or outlet chambers (anterior or posterior, left or right); the location of the papillary muscles and chordal attachments within the ventricular chambers (straddling and/or overriding) [Figure 1]
  4. The size of the interatrial and interventricular communications was assessed by 2D echocardiography, and the degree of restriction was assessed by color and continuous flow Doppler[8]
  5. If the dominant ventricle was a LV, M-mode was used to estimate the LV end-diastolic diameter and LV end-systolic diameter by applying the m-mode to the LV just below the mitral valve in a parasternal long-axis view. Biplane-modified Simpson method was used to assess the dominant ventricle diastolic, systolic volumes, and ejection fraction (EF). Also, 2D eye balling visual estimation of ventricular systolic function was done by an experienced echocardiographer.[7],[8]
Figure 1: Parasternal short axis view. The small left ventricle posteriorly and the right ventricle anteriorly in patient number 4

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Doppler evaluation

  • The status of the AV valve leaflets, evaluation of the severity of AV valve regurgitation
  • Pulsed wave (PW) and continuous wave (CW) Doppler evaluation of pulmonary flow to identify site and degree of pulmonary stenosis (PS). Pulmonary regurgitation jet used to estimate mean and diastolic PA pressures
  • Cavopulmonary anastomosis assessment of the flow was done by color Doppler, PW and CW Doppler, and the presence of respiratory variation and evidence of obstruction or reversal of flow.[9]


Speckle-tracking echocardiography: According to the European Society of Cardiology Current and evolving Echocardiographic techniques, 2011

Probe selection: The same probe used to obtain the usual 2D images was used for recording the 2D loops used for STE.

Image acquisition: Images were acquired during breath holds with stable electrocardiographic (ECG) recordings and digitally stored for offline analysis. At least three cycles were stored to perform offline STE analysis.

The LV was imaged in the apical four-chamber view; conventional 2D echocardiographic grayscale apical four-chamber images were recorded [Figure 2]. An optimal frame rate of 60–80 frames/s was obtained by adjusting the sector width and depth of the image to focus on the LV.[10]
Figure 2: Conventional two-dimensional apical four-chamber view stored for offline analysis in case number 7

Click here to view


Methods of analysis

Analysis was done offline using the GE software (GE echocardiography machine, Vivid 9) and quantification system; it was done mostly on the echocardiography machine and rarely on the workstation.

The following methods were used for analysis:

Dominant ventricular strain was analyzed using conventional 2D echocardiographic grayscale apical four-chamber images. The region of interest was obtained by tracing the LV endocardial borders at the level of the septum and the free wall in a still frame at end systole. An automated software program was used to calculate the frame-to-frame displacements of speckle pattern within the region of interest throughout the cardiac cycle.[11]

Longitudinal strain and strain rate (SR) [Figure 3] curves were obtained; the global LV strain curve was based on the average. The extent of myocardial deformation (defined as the peak longitudinal systolic strain) was expressed as a percentage of the longitudinal shortening in systole compared with diastole for each segment of interest.
Figure 3: Longitudinal strain rate curves for patient number 18

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Statistical analysis

All data were gathered, statistically analyzed, and tabulated. All numerical variables were expressed as mean ± standard deviation, and categorical variables were expressed as percentage (%). Changes in continuous variables were evaluated with the paired t-test. Linear regression analysis was employed for assessment of correlations between continuous variables. For all analyses, P < 0.05 was considered statistically significant.


  Results Top


The study included 47 patients with FSV whether they underwent superior cavopulmonary anastomosis or not. Patients were referred for clinical follow-up, echocardiographic assessment, or elective cardiac catheterization in Ain Shams University Hospitals, Cardiology Department, from November 2017 to July 2018.

Demographic data

The study included 47 patients, 30 males (63.8%) and 17 females (36.2%) [Figure 1]. Their age ranged between 6 and 12 years, with mean age of 8.22 ± 1.94 years. Their weight ranged between 20 and 45 kg, with mean weight of 33.40 ± 6.47 kg. Their height ranged between 107 and 150 cm, with mean height of 134.57 ± 9.71 cm. The body surface area ranged between 0.59 and 1.7 m2, with mean BSA of 1.21 ± 0.27 m2 [Table 1].
Table 1: Demographic data

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Clinical and laboratory data

Clinically, 35 cases (74.5%) showed mild cyanosis, while 12 cases (25.5%) showed moderate cyanosis. Regarding clubbing degree, only 25 patients (53.2%) showed 2nd-degree clubbing and 22 cases (46.8%) showed 3rd-degree clubbing. According to NYHA and modified ross classifications of dyspnea, 26 cases had dyspnea Class I, and 21 cases had dyspnea Class II. The patients' hemoglobin level was 9 g/dl in 1 case; in 15 cases, it ranged between 11 and 13 g/dl; and in 31 cases, it ranged between 14 and 17 g/dl. While the patients' O2 saturation on room air ranged between 60%–80% in 5 cases, and 81%–90% in 42 cases, none of the patients showed signs of Glenn dysfunction.

Previous interventions

None of the patients had any percutaneous intervention done. Regarding surgical intervention, only 5 cases (10.6%) underwent PA banding. Twenty-three cases (48.9%) had right-sided Glenn shunt, 19 of them underwent surgery within the 1st year of life, and the remaining 4 cases underwent surgery within the 2nd year of life.

Echocardiographic data

Regarding the basic anatomy, 8 cases (17%) had TA, 3 cases (6.4%) had mitral atresia, 14 cases (29.8%) had double inlet left ventricle, 20 cases (42.6%) had double outlet right ventricle, and 2 cases (4.3%) had double inlet right ventricle.

Twenty-five cases (53.2%) had dominant right ventricle while 22 cases (46.8%) had dominant left ventricle.

All cases had dilated dominant ventricle volumes. EF was assessed by modified Simpson's method and 2D eyeballing, 26 cases (55.3%) had impaired systolic function, while the remaining had normal systolic function.

Regarding pulmonary hypertension, 24 cases (51.1%) had pulmonary hypertension.

Regarding level of PS, 11 cases (23.4%) had valvular PS, 12 cases (25,5%) had subvalvular PS, and 6 cases (12.7%) had supravalvular PS.

Regarding degree of PS, 4 cases (8.5%) had mild PS, 7 cases (14.9%) had moderate PS, and 16 cases (34%) had severe PS.

Regarding the global longitudinal strain (GLS), all patients had low global strain values; so, we divided them into patients with mildly impaired systolic function by STE and patients with moderately impaired systolic function by STE. 26 cases (55.3%) had a GLS from −11 to −15 (mild ventricular dysfunction) and 20 cases (44.7%) had a GLS from − 6 to − 10 (moderate ventricular dysfunction).

Regarding the SR/sec, 26 cases (55.3%) ranged from −1.15 to −1.22. 21 cases (44.7%) had SR more negative than −1.22 [Table 2].
Table 2: The echocardiographic data

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Ventricular morphology significantly affected GLS values; patients with LV-dominant ventricular morphology had higher strain and SR values. 28% of patients with dominant LV morphology had moderate ventricular dysfunction by STE while 63.6% of patients with the RV as the dominant ventricle had moderate ventricular dysfunction [Table 3] and [Figure 4].
Table 3: Relation between the side of dominance of the ventricle, the estimated ejection fraction, the global strain and strain rate

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Figure 4: The significant relation between the side of dominance and the global strain (blue stands for left ventricular, green for the right ventricular)

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Patients who underwent a Glenn shunt had higher EF. The age at time of Glenn operation had a strong correlation with the function assessed by modified Simpson's method and 2D eyeballing with P = 0.00.

The younger age at the time of the operation correlated with higher EF and higher GLS values where 81% of patients with normal systolic functions by M mode and Simpson's method underwent the operation within the 1st year of life while those with impaired systolic functions by M mode and the modified Simpson's method, 80.8% of them did not undergo a Glenn operation and 11.5% of them underwent Glenn shunt within the 2nd year of life [Table 4].
Table 4: Predictors of better systolic ventricular functions

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There was a strong correlation between the basic anatomy of the single ventricle and the EF assessed by modified Simpson's method and 2D eyeballing with P = 0.000. 57.1% of patients with a dominant RV had normal EF; there was also a strong correlation between PA pressure and the EF; most patients with unprotected pulmonary circulations had impaired ventricular functions [Table 5].
Table 5: Relation between different echocardiographic parameters and ejection fraction of dominant ventricle

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Regarding speckle-tracking echocardiography of the dominant ventricle, all patients included in the study had a low GLS values; so, patients were divided into 2 subgroups: patients with mild ventricular dysfunction by STE where the GLS ranged from − 11 to − 15 and patients with moderate ventricular dysfunction by STE where the GLS ranged from − 6 to − 10.

Younger patients had higher (more negative strain values).

Patients with higher O2 saturation on room air had higher SR values.


  Discussion Top


Functionally single ventricle arrangements represent a heterogeneous group of anomalies sharing common feature which is functional single cardiac chamber. In most patients with functionally UVHs, there are two morphologic ventricles (dominant left and dominant right ventricle), one of which is too small to sustain one of the circulations.[1]

There are different morphological types of FSV that include TA, mitral atresia, double outlet right ventricle, double inlet left ventricle, and double inlet right ventricle; in these types, the dominant ventricle sustains the pressure and volume overload from the systemic and pulmonary circulation.[2]

Surgical palliation of anatomic and FSV usually requires a series of operative procedures. Common surgical pathway for all these variants is Glenn shunt procedure and later completion of Fontan in which the systemic venous return is diverted directly to the pulmonary arteries and the pulmonary venous return crosses the AV valve(s) and is pumped by the “single ventricle” to the systemic vascular bed.[12]

Theoretically, when the dominant ventricle sustains a lot of pressure from the systemic and pulmonary circulation which is already not prepared for that, it will eventually fail. This study was conducted to evaluate the impact of the morphology of the dominant ventricle on myocardial deformation assessed using conventional 2D and speckle-derived strain echocardiography.

Previously published studies have demonstrated acceptable accuracy and reliability of speckle-tracking echocardiographic modalities in assessing global and regional myocardial function in children.[8]

Our study included 47 patients with FSV. All these 47 patients were feasible for assessment by STE.

25 patients had a dominant RV and 22 patients had a dominant LV. The study showed that most patients had normal systolic ventricular functions as assessed by 2D eye balling and modified Simpson's method. All patients had low GLS values; however, patients with morphological LV had better (more negative) GLS values as compared to those with a dominant RV.

These findings are concordant with the study conducted by Suntratonpipat et al.[13]

The study included 32 infants with functional single right ventricle and 16 cases with functional single left ventricle. Suntratonpipat et al. compared the dominant left and right ventricles regarding global longitudinal and circumferential strain and found that the patient with functional right ventricle had a mechanical disadvantage since birth in comparison with patients with dominant left ventricle.[13]

We studied patients between 6 and 12 years of age not infants, and we included 23 patients who underwent Glenn shunt.

Our results also were different when compared to Petko et al.; they examined 29 children with systemic right ventricle (Group 1: mean age 2.7 years, mean time after Fontan 3.0 years) and 22 children with systemic left (Group 2: mean age 4.8 years, mean time after Fontan 4.2 years) after Fontan surgery using 2D speckle tracking. They compared global and regional longitudinal strain and SR as well as time to peak strain in basal lateral and septal segments. The results were that the Global strain (−18.5 3.5 vs. −17.9 3.2%, P = not significant [NS]) and global SR (−1.0 0.2 vs. −1.0 0.2/s, P = NS) did not differ between the two groups. Regional strain (−8.7 8.6 vs. −14.7 6.7%, P = 0.008) and SR (−0.7 0.4 vs. −1.0 0.3%, P = 0.002) in the basal septal segment were lower in Group 1, while regional strain was higher in group 1 in the apical septal segment (−23.5 8.0 vs. −18.4 5.9%, P = 0.402). Time to peak strain was higher in the basal septal segment in Group 1 (410 78 vs. 338 90 ms, P = 0.004) but not different in the basal lateral segment.[14]

The study conclusion was despite minor regional differences in longitudinal deformation and dyssynchrony, overall ventricular longitudinal deformation was not different between morphologic right and left ventricles. These findings may reflect similar adaptation of longitudinal function of both ventricular morphologies to the single-ventricle circulation after Fontan surgery.

None of our patients underwent the Fontan operation, and this may explain the different results.

Koopman et al.'s results were different than our study results; they aimed to describe the association between myocardial deformation assessed by STE and single ventricle function assessed by cMR imaging (cMRI) and to evaluate differences in myocardial deformation in children with single left and single RV morphology. Cross-sectional, multicenter study in 77 children after total cavopulmonary connection (TCPC) was conducted. STE segmental and global longitudinal peak strain and systolic SR of the dominant ventricle were measured.

Koopman et al. used the conventional echocardiographic measures and only the GLS and SR in the assessment of myocardial deformation by STE.

Global single ventricle longitudinal strain and SR was similar in patients after TCPC with single left and single RV morphology (−19.0 ± 3.1% vs. 19.2 ± 3.2%, P = 0.94) based on STE-derived parameters; the myocardial function in morphological RVs is similar compared to morphological LVs.[15]

As regards the EF (assessed by 2D and modified Simpson's method) and the demographic, clinical, surgical and echocardiographic parameters, our study included 26 patients that had impaired function with percentage (55.3%) of total patients and 24 of them had pulmonary hypertension (80.0%) and did not underwent Glenn shunt procedure as a palliative procedure.

Our study demonstrated that in 23 patients that underwent Glenn shunt (as a palliative procedure and they represent 48.9% of total patients), 18 of them had a normal function and that was assessed by 2D eyeballing and modified Simpson's method and the remaining five had impaired function, regarding the age at time of operation; there was a significant relation between that and the function with P = 0.00. Eighty-one percent of patient with normal function underwent the operation in the 1st year of life in comparison with 80.8% of patients with impaired function did not undergo the operation. So that means younger age at time of operation is associated with better EF.

In contrary to all the previously mentioned studies, all our patients had GLS values less than normal; so, we divided the patients into two subgroups, those with mildly reduced GLS and those with moderately reduced GLS.

Regarding the relation between the laboratory data as O2 saturation and the myocardial deformation, our study found that patients with higher O2 saturation in room air had a significantly higher SR (>−1.22/s) with P = 0.34.

These findings are discordant with the study conducted by Koopman et al. on patients with FSV and the GLS and SR was assessed by cMRI and the results were that there is no significant relation between the resting O2 on the myocardial deformation.[15]

Our study also demonstrated that patient that never underwent shunt operation and had pulmonary hypertension (23 patients) had a significantly lower SR between (−1.15 and -1.22/sec) with P = 0.029.

It also demonstrated that the basic anatomy of the heart had no effect on the SR assessed by STE with P = 0.128.

These finding are concordant with the study conducted by Petko et al. on 51 patients with FSV, and the results were that there is no significant difference on the SR determined by the type of the basic anatomy of the heart.[14]

Limitations and recommendations

  • The study was done on a small number of cases (47 cases); a larger sample size will demonstrate more accurate data
  • Only longitudinal deformation was investigated in this study. This partial approach to myocardial deformation did not allow the description of the complex 3D pattern of dominant ventricular contraction. We recommend studying both circumferential and radial strain, together with the longitudinal strain in future studies
  • An additional limitation of the technique is that results depend critically on the machine with which the analysis is performed
  • We recommend more complex and accurate tools can be used for assessment of volumes and myocardial dyssynchrony as cMRI.



  Conclusion Top


We concluded that patients with dominant RV have lower GLS values and a significant mechanical disadvantage when it comes to myocardial deformation; early Glenn shunt is associated with better ventricular systolic functions and thus better morbidity and mortality for single ventricle patients.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Wilkinson JL, Anderson RH. Anatomy of functionally single ventricle. World J Pediatr Congenit Heart Surg 2012;3:159-64.  Back to cited text no. 1
    
2.
Edwards RM, Reddy GP, Kicska G. The functional single ventricle: How imaging guides treatment. Clin Imaging 2016;40:1146-55.  Back to cited text no. 2
    
3.
Bonnet D, Fermont L, Kachaner J, Sidi D, Amiel J, Lyonnet S, et al. Tricuspid atresia and conotruncal malformations in five families. J Med Genet 1999;36:349-50.  Back to cited text no. 3
    
4.
Mor-Avi V, Lang RM, Badano LP, Belohlavek M, Cardim NM, Derumeaux G, et al. Current and evolving echocardiographic techniques for the quantitative evaluation of cardiac mechanics: ASE/EAE consensus statement on methodology and indications endorsed by the Japanese Society of Echocardiography. Eur J Echocardiogr 2011;12:167-205.  Back to cited text no. 4
    
5.
Voigt JU. Quantification of myocardial deformation. In: Flachskampf FA, editor. Praxis der Echokardiographie. Stuttgard: Thieme; 2010.  Back to cited text no. 5
    
6.
Moen CA, Salminen PR, Dahle GO, Hjertaas JJ, Grong K, Matre K. Is strain by speckle tracking echocardiography dependent on user controlled spatial and temporal smoothing? An experimental porcine study. Cardiovasc Ultrasound 2013;11:32.  Back to cited text no. 6
    
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Lai WW, Mertens LL, Geva T, Cohen MS, Geva T, editors. Echocardiography in Pediatric and Congenital Heart Disease: From Fetus to Adult. USA: Wiley-Blackwell; 2012.  Back to cited text no. 7
    
8.
Truong UT, Sun HY, Tacy TA. Myocardial deformation in the fetal single ventricle. J Am Soc Echocardiogr 2013;26:57-63.  Back to cited text no. 8
    
9.
Glenn WW. Circulatory bypass of the right side of the heart. IV. Shunt between superior vena cava and distal right pulmonary artery; report of clinical application. N Engl J Med 1958;259:117-20.  Back to cited text no. 9
    
10.
Henaine R, Vergnat M, Mercier O, Serraf A, De Montpreville V, Ninet J, et al. Hemodynamics and arteriovenous malformations in cavopulmonary anastomosis: The case for residual antegrade pulsatile flow. J Thorac Cardiovasc Surg 2013;146:1359-65.  Back to cited text no. 10
    
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d'Udekem Y, Xu MY, Galati JC, Lu S, Iyengar AJ, Konstantinov IE, et al. Predictors of survival after single-ventricle palliation: The impact of right ventricular dominance. J Am Coll Cardiol 2012;59:1178-85.  Back to cited text no. 11
    
12.
O'Leary PW. Prevalence, clinical presentation and natural history of patients with single ventricle. Prog Pediatric Cardiol 2002;16:31-8.  Back to cited text no. 12
    
13.
Suntratonpipat S, Khoo NS, Colen T. Impaired single right ventricular function compared to single left ventricles during the early stages of palliation: A longitudinal study. J Am Soc Echocardiogr 2017;30:469.  Back to cited text no. 13
    
14.
Petko C, Hansen JH, Scheewe J, Rickers C, Kramer HH. Comparison of longitudinal myocardial deformation and dyssynchrony in children with left and right ventricular morphology after the Fontan operation using two-dimensional speckle tracking. Congenit Heart Dis 2012;7:16-23.  Back to cited text no. 14
    
15.
Koopman LP, Geerdink LM, Bossers SSM, Duppen N, Kuipers IM, Ten Harkel AD, et al. Longitudinal myocardial deformation does not predict single ventricle ejection fraction assessed by cardiac magnetic resonance imaging in children with a total cavopulmonary connection. Pediatr Cardiol 2018;39:283-93.  Back to cited text no. 15
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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