Am J Cardiol. 2014 Nov 15;114(10):1590-8. doi: 10.1016/j.amjcard.2014.08.028.

Reference Values and Calculation of Z-Scores of Echocardiographic Measurements of the Normal Pediatric Right Ventricle

 

Martin Koestenbergera, MD, Bert Nagela, MD; William Ravekesb, Alexander Avianc, PhD, Ante Burmasa, MD, Gernot Grangla, MD, Andreas Gamillschega, MD

aDivision of Pediatric Cardiology, Department of Pediatrics, Medical University Graz, Austria

bDivision of Pediatric Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA

cInstitute for Medical Informatics, Statistics and Documentation, Medical University Graz, Austria

 

Correspondence to:

Martin Koestenberger, MD

Department of Pediatrics; Medical University Graz

Auenbruggerplatz 34/2; A-8036 Graz, Austria

Tel.: +43 316 385 84276, Fax: +43 316 385 13682

E-mail: martin.koestenberger@medunigraz.at or koestenbergerm@gmx.at

 

Abstract

Determination of right ventricular (RV) size and function has gained more interest during recent years in both adults and children, especially in patients with congenital heart disease. Data of normal RV size parameters in children is scant. We investigated growth related changes of RV internal dimensions in a healthy pediatric cohort and the predictive value of RV parameters in identifying enlarged RVs in children with a secundum type atrial septal defect (ASD). A prospective study was conducted in a group of 576 healthy children (age: day 1 to 18 years) and 37 children (age range: 1.4 – 17.7 years) with a moderate-sized to large ASD. We determined the effects of age, body length (BL), body weight (BW), and body surface area (BSA) on the following RV parameters: end-diastolic basal-diameter (EDb-d), end-diastolic mid-cavity diameter (EDm-d), end-diastolic length (EDL), end-systolic length (ESL), end-diastolic area (EDa), and end-systolic area (ESa). The predictive value of normal values stratified for age, BW, BL, and BSA was tested in our ASD children. RVEDb-d, RVEDm-d, RVEDL, RVESL, RVEDa, and RVESa showed a positive correlation with age, BL, BSA, and BW. In our population RV z-scores showed a high specificity for detecting ASD patients with sensitivity up to 89%, especially in children below eight years of age. In conclusion the normal ranges of pediatric RV internal dimensions are provided. Z-scores of these RV parameters were also calculated. Normal RV z-scores might be important predictors in identifying enlarged RVs in ASD patients.

 

Supplement:

Enlarged RV dimensions can provide relevant hints for the diagnosis of congenital heart defects (CHD), such as atrial septal defect (ASD). RV volume and pressure overloading conditions after cardiac surgery of CHD can cause remodeling and dysfunction of the RV. Therefore, accurate assessment of RV size and function has become critically important for guiding treatment and follow-up in a large number of cardiovascular conditions including structural, electrical and functional abnormalities. Reference values of RV diameter measurements for the adult population are available [1]. Based on RV guidelines [1] 2D echocardiographic measurements from the apical 4-chamber view were described to be useful for the assessment of RV size: the RV end-diastolic basal diameter (RVEDb-d), the RV end-diastolic mid-cavity diameter (RVEDm-d), the RV end-diastolic length (RVEDL), the RV end-diastolic area (RVEDa), and the RV end-systolic area (RVESa). These parameters were easy to determine, and therefore may be used as a non-invasive measurement to study RV size and performance also in children [2]. In the pediatric age group the influence of growing age, body length (BL), body weight (BW), and body surface area (BSA) on RV internal dimensions have not been appropriately analyzed to date.

Our healthy study group consisted of 576 children (328 male; 248 female). The study group encompassed neonates to adolescents (age: 1 day to 18 years; BW: 2.8 kg to 98.0 kg; BSA: 0.20 to 2.23 m²), including 46 neonates and 64 infants. Our ASD study group consisted of 37 patients (16 male, 21 female; median age: 6.2 years; range: 1.4 – 17.7 years) with unrepaired isolated secundum type ASDs with moderate to large left-to-right shunting at the atrial level and signs of RV volume overload.

 

MK Fig 1

Figure 1: RV measurements in end-diastole in the apical 4-chamber view. Figure 1A) The RVEDb-d was measured as the distance between the RV free wall and septum, just distal to the tricuspid annulus. The RVEDm-d is measured in the middle third of the RV at the level of the LV papillary muscles. The RVEDb-d, and RVEDm-d were measured from the leading edge to the leading edge of the endocardial signals. The measurements of the RVEDb-d, RVEDm-d, RVEDL, and RVEDa were performed at end-diastole, which was defined as the frame closest to the onset of the R wave of the electrocardiogram. The RVEDa was measured by outlining the endocardial borders of the RV in end-diastole in the apical 4-chamber view.

 

The measurements of the RVEDb-d, RVEDm-d, RVEDL, and RVEDa were performed at end-diastole (Figure 1). The RVEDb-d, and RVEDm-d were measured from the leading edge to the leading edge of the endocardial signals. The measurements of the RVESL, and RVESa were performed at end-systole (Figure 2).

All investigated RV variables, the RVEDb-d, RVEDm-d, RVEDL, RVESL, RVEDa, and RVESa values increased from neonates to adolescents in a nonlinear way. In our patients with moderate-sized to large secundum ASDs the median age specific RVEDb-d z-score was 3.3, the median age specific RVEDm-d z-score was 2.1, the median age specific RVEDL z.score was 1.7, the median age specific RVESL z-score was 2.6, the median age specific RVEDa z-score was 3.0, and the median age specific RVESa z-score was 4.0, respectively. Younger children had high age-specific RVEDb-d, RVEDm-d, RVESL, RVEDa, and RVESa z-scores. With growing age these z-scores decreased in our ASD patients (r < -0.37, p < 0.024). Age specific z-scores came closer to the mean of our healthy children. Similar developments were observed in BSA, BW and BL–specific z-scores.

Our study was undertaken to obtain normal RV internal dimensions values in a healthy pediatric study group. It is important to create age-related normal values for children because pediatricians, unlike their adult colleagues, need to have indexed measurements to age, BL, BW, and BSA due to the variability of growth. We may mention the difficulty in making quantitative assessments of dilated RV dimensions using 2D echocardiography in children with e.g. an ASD without having age-related normative data. Before determining RV internal parameters in children with various forms of CHDs, sufficient quantitative pediatric reference data of echocardiographic normal patients from infants to adolescents are required. We found that pediatric values of the RVEDb-d, RVEDm-d, RVEDL, RVESL, RVEDa, and the RVESa increased with age, BL, BW, and BSA, respectively. As expected the normal values for all RV internal parameters in our older adolescents are similar to adult RV diameter normal reference data [1]. Clinically relevant difference of the RV internal parameter values between male and female subjects were only seen in age specific RVESL values. Normal ranges of the pediatric RV internal parameters RVEDb-d, RVEDm-d, RVEDL, RVESL, RVEDa, and RVESa, respectively, are provided and z-scores of these RV parameters were calculated. All RV internal parameters showed a positive correlation with age, BW, BL, and BSA and increased from neonates to adolescents in a nonlinear way. In our population RV z-scores showed a high specificity for detecting ASD patients with sensitivity up to 89% and might therefore be important predictors in identifying pediatric ASD patients, especially in children below eight years of age.

 

MK Fig 2

Figure 2: RV measurements in end-systole in the apical 4-chamber view. The measurements of RVESL, and RVESa were performed at end-systole, which was defined as the time frame preceding tricuspid valve opening, showing the minimal RV area (in most instances the time of the end of the T wave). The RVESa was measured by outlining the endocardial borders of the RV in end-systole. Abbreviations: LV, left ventricle; RV, right ventricle; EDb-d, end-diastolic basal diameter; EDm-d, end-diastolic mid-cavity diameter, EDL, end-diastolic length; ESL, end-systolic length; EDa, end-diastolic area; ESa, end-systolic area.

 

References

1.) Rudski LG, et al. 2010; Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiography endorsed by the European Association of Echocardiography, a registered branch of the European Society of Cardiology, and the Canadian Society of Echocardiography. J Am Soc Echocardiogr; 23: 685-713.

2.) Lopez L, et al. 2010; Recommendations for quantification methods during the performance of a pediatric echocardiogram: a report from the Pediatric Measurements Writing Group of the American Society of Echocardiography Pediatric and Congenital Heart Disease Council. J Am Soc Echocardiogr; 23: 465-495.

 

Highlights of this study are:

1) Normal pediatric RV dimensions were measured and z-scores calculated in 576 healthy children and 37 children with hemodynamic relevant ASDs

2) This is the first study presenting normal ranges of RV systolic and diastolic dimensions in children from infancy to 18 years of age

3) RV z-scores > 2 SD were predictive for detecting ASD patients younger than 8 years with enlarged RVs

 

 

 

 

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