Left Ventricular End-Diastolic Dimension for the Assessment of the Pulmonary to Systemic Flow Ratio in Congenital Heart Diseases

Ventricular septal defect (VSD) and patent ductus arteriosus (PDA) are the most common pediatric heart diseases, typically exhibiting an increase in pulmonary flow induced by a left-to-right shunt. Even with apparent heart failure (HF) symptoms in pediatric VSD or PDA induced by a large shunt, the normal myocardium with abnormal volume overload is in striking contrast to adult HF with reduced ejection fraction. Indications for surgical closure of pediatric VSD and PDA must be carefully determined based on various considerations.¹ Among these, the pulmonary to systemic blood flow ratio (Qp/Qs) is an important index of disease severity, reflecting the shunt volume. Classically, cardiac catheterization can quantify Qp/Qs. However, as cardiac catheterization is an invasive procedure, establishing a noninvasive method for evaluating Qp/Qs is of clinical relevance.

Article p ????

As the left-to-right shunt of the VSD and PDA increases pulmonary flow,² the elevated pulmonary venous return enters the left atrium and left ventricle (LV), unless a significant atrial septal defect is encountered; thus, the left heart size should reflect the shunt volume and Qp/Qs in such a situation. However, body size varies greatly in children. Therefore, the LV end-diastolic dimension (LVEDd) corrected by body size has been used as one of the echocardiographic indices reflecting the shunt volume in VSD and PDA,^1,3 using the ratio of the measured LVEDd to the “normal” LVEDd estimated by body height⁴ or body surface area (BSA)^5–11 (% normal LVEDd). The LVEDd (calculated by body height) of 87% of preterm infants who underwent surgical ligation of PDA reportedly exceeded 130% of the normal.³ Although some studies have used % normal LVEDd,³ others used Z-scores for LVEDd.^5,11,12 However, to date, no study has confirmed the potential relationship between any indexed LVEDd by body size and Qp/Qs by cardiac catheterization in this population.

In this issue of the Journal, the study by Sumitomo et al¹³ resulted in a clinically relevant contribution because it indicated that the Z-score of the LV diameter strongly correlates with the Qp/Qs. The Z-score calculation was substantially complicated when compared with that of % normal LVEDd. The authors used the method described by Pettersen et al¹¹ to calculate the expected LV diameters (Z=0, or 100% normal) using BSA and Z-score. Figure 1 shows the expected value curve of LVEDd by BSA, as reported by Pettersen et al¹¹ and others.^5–10 The line of Pettersen et al¹¹ was found to lie between the regression lines of 2 oriental population studies of Aotsuka et al (Japan)¹⁰ and Wang et al (China),⁵ which are not markedly far apart. Thus, it appears reasonable to apply Pettersen’s method¹¹ to the study by Sumitomo et al¹³ performed in Japan.

Figure 1.

Normal values of left ventricular end-diastolic dimension (LVEDd) predicted according to body surface area (BSA). The red line is the regression line reported by Pettersen et al,¹¹ which was used in the study by Sumitomo et al¹³ and previous regressions by Gutgesell et al,⁷ Henry et al,⁸ Pearlman et al,⁶ Kampmann et al,⁹ Aotsuka et al,¹⁰ and Wang et al⁵ are superimposed.

As stated by the authors, the Z-score of LVEDd by Pettersen’s method, using a single value of mean square error,¹¹ demonstrated a 1 : 1 relationship with % normal LVEDd (Figure 2). Moreover, these 2 parameters demonstrated an almost linear relationship in the physiological range of −2 to +4 SD. Thus, the clinical significance of the 2 indices is considered equal as long as a single value of mean square error is used;¹¹ however, both concepts tend to differ, as the Z-score indicates how far apart in the population and % normal directly indicates how much the LV expands. Their results¹³ indicated that Qp/Qs=2 corresponds to a Z-score of LVEDd=3.25 and % normal LVEDd=138%.

Figure 2.

Relationship between % normal and Z-score of the left ventricular end-diastolic dimension (% normal LVEDd and Zd, respectively) in the study by Pettersen et al¹¹ and Sumitomo et al.¹³ The relationship between the two is nearly linear in the physiological range.

Even in this era of three-dimensional echocardiography, LVEDd, a classical and simple echocardiographic linear measurement, continues to play an important role in reflecting Qp/Qs in children with VSD and PDA, as shown by Sumitomo et al.¹³

Financial Disclosure

The author has no financial relationships relevant to this article to disclose.

Conflict of Interest

The author has no conflicts of interest relevant to this article to disclose.

References

• 1.   Toyoshima K, Isayama T, Kobayashi T, Su C, Mikami M, Yokoyama T, et al. What echocardiographic indices are predictive of patent ductus arteriosus surgical closure in early preterm infants?: A prospective multicenter cohort study. J Cardiol 2019; 74: 512–518.
• 2.   Masutani S, Isayama T, Kobayashi T, Pak K, Mikami M, Tomotaki S, et al. Ductus diameter and left pulmonary artery end-diastolic velocity at 3 days of age predict the future need for surgical closure of patent ductus arteriosus in preterm infants: A post-hoc analysis of a prospective multicenter study. J Cardiol 2021; 78: 487–492.
• 3.   Nagasawa H, Terazawa D, Kohno Y, Yamamoto Y, Kondo M, Sugawara M, et al. Novel treatment criteria for persistent ductus arteriosus in neonates. Pediatr Neonatol 2014; 55: 250–255.
• 4.   Nagasawa H. Novel regression equations of left ventricular dimensions in infants less than 1 year of age and premature neonates obtained from echocardiographic examination. Cardiol Young 2010; 20: 526–531.
• 5.   Wang SS, Hong WJ, Zhang YQ, Chen SB, Huang GY, Zhang HY, et al. Regression equations for calculation of Z scores for echocardiographic measurements of left heart structures in healthy Han Chinese children. J Clin Ultrasound 2018; 46: 328–333.
• 6.   Pearlman JD, Triulzi MO, King ME, Newell J, Weyman AE. Limits of normal left ventricular dimensions in growth and development: Analysis of dimensions and variance in the two-dimensional echocardiograms of 268 normal healthy subjects. J Am Coll Cardiol 1988; 12: 1432–1441.
• 7.   Gutgesell HP, Paquet M, Duff DF, McNamara DG. Evaluation of left ventricular size and function by echocardiography: Results in normal children. Circulation 1977; 56: 457–462.
• 8.   Henry WL, Ware J, Gardin JM, Hepner SI, McKay J, Weiner M. Echocardiographic measurements in normal subjects: Growth-related changes that occur between infancy and early adulthood. Circulation 1978; 57: 278–285.
• 9.   Kampmann C, Wiethoff CM, Wenzel A, Stolz G, Betancor M, Wippermann CF, et al. Normal values of M mode echocardiographic measurements of more than 2000 healthy infants and children in central Europe. Heart 2000; 83: 667–672.
• 10.   Aotsuka H, Murakami T, Ishikawa S, Nakazawa M. Normal values of cardiac structures and great vessels in children: Review of the literature and comparisons with normal values. Pediatr Cardiol Card Surg 2003; 19: 421–430 [in Japanese].
• 11.   Pettersen MD, Du W, Skeens ME, Humes RA. Regression equations for calculation of Z scores of cardiac structures in a large cohort of healthy infants, children, and adolescents: An echocardiographic study. J Am Soc Echocardiogr 2008; 21: 922–934.
• 12.   Lopez L, Colan S, Stylianou M, Granger S, Trachtenberg F, Frommelt P, et al. Relationship of echocardiographic z scores adjusted for body surface area to age, sex, race, and ethnicity: The Pediatric Heart Network Normal Echocardiogram Database. Circ Cardiovasc Imaging 2017; 10: e006979.
• 13.   Sumitomo NF, Kodo K, Maeda J, Miura M, Yamagishi H. Echocardiographic left ventricular Z-score utility in predicting pulmonary-systemic flow ratio in children with ventricular septal defect or patent ductus arteriosus. Circ J, doi:10.1253/circj.CJ-21-0559.