Short-axis imaging of the pulmonary valve through a modified parasternal view: A feasibility study in young children

Mani Ram Krishna; Usha Nandhini Sennaiyan

doi:10.4103/jiae.jiae_63_21

ORIGINAL RESEARCH

Year : 2022 | Volume : 6 | Issue : 3 | Page : 167-170

Short-axis imaging of the pulmonary valve through a modified parasternal view: A feasibility study in young children

Mani Ram Krishna, Usha Nandhini Sennaiyan
Department of Pediatric Cardiology, R.K. Hospital for Women and Children, Thanjavur, Tamil Nadu, India

Date of Submission	18-Nov-2021
Date of Decision	20-Jan-2022
Date of Acceptance	21-Jan-2022
Date of Web Publication	29-Sep-2022

Correspondence Address:
Dr. Mani Ram Krishna
R.K. Hospital for Women and Children, No 7, V.O.C. Nagar, Thanjavur - 613 007, Tamil Nadu
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jiae.jiae_63_21

Abstract

Background: The aortic and pulmonary valves are both tricuspid valves. All cusps of the aortic valve can be imaged in the parasternal short-axis view but the pulmonary valve cusps are not routinely imaged during trans-thoracic echocardiography. Methods: We evaluated the feasibility of imaging all three pulmonary valve cusps in the short-axis by a modified parasternal view in 100 consecutive children below the age of 5 years. Results: A satisfactory short-axis imaging of the pulmonary valve was possible in 96 of 100 consecutive children in whom a complete echocardiogram study was performed. This detected abnormalities in the pulmonary valve in 10 children. This included bicuspid pulmonary valves, tricuspid pulmonary valves with unequal cusps, and a quadricuspid pulmonary valve. Visualization of the pulmonary valve permitted preoperative planning of pulmonary valve repair in one infant with a concomitant large ventricular septal defect. Conclusion: An adequate visualisation of the pulmonary valve leaflets by a modified parasternal view during trans-thoracic echocardiography was feasible in a vast majority of young children. The modified pulmonary short-axis view should hence be included as the part of a comprehensive pediatric echocardiographic protocol.

Keywords: Short axis, transthoracic echocardiography, tricuspid pulmonary valve

How to cite this article:
Krishna MR, Sennaiyan UN. Short-axis imaging of the pulmonary valve through a modified parasternal view: A feasibility study in young children. J Indian Acad Echocardiogr Cardiovasc Imaging 2022;6:167-70

How to cite this URL:
Krishna MR, Sennaiyan UN. Short-axis imaging of the pulmonary valve through a modified parasternal view: A feasibility study in young children. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2022 [cited 2023 Sep 27];6:167-70. Available from: https://jiaecho.org/text.asp?2022/6/3/167/357594

Introduction

The aortic and pulmonary valves are both tricuspid valves. The parasternal short-axis imaging of the aortic valve is a well-established view in transthoracic echocardiography. However, the pulmonary valve is often imaged only in the long-axis during trans-thoracic echocardiography.^[1] It is possible to visualize only two of the three cusps simultaneously on long-axis imaging. This presents a challenge in understanding the nature of the pulmonary valve pathologies. The reasons attributed to the difficulty in imaging include the sub-sternal location of the pulmonary valve as well as its proximity to the upper lobe of the left lung.^[2],[3],[4] Abnormalities of the pulmonary valve and the right ventricular outflow tract occur in a sizable proportion of children with congenital heart diseases. These include variation in the number of cusps, inequality of cusps, commissural fusion, thickening and dysplasia of the cusps and absence of the pulmonary valve.^[2]

Some pediatric cardiologists and cardiac sonographers utilize a modified parasternal view to image the pulmonary valve in the short-axis. This is obtained by rotating the probe in the clockwise direction after obtaining an aortic valve short-axis view. In some cases, the probe will need to be moved one intercostal space above the aortic valve view along with clockwise rotation. The pulmonary valve in this view has an inverted Mercedes Benz appearance with an anterior cusp, a left posterior cusp, and a right posterior cusp [Figure 1]a and [Supplemental Video 1].^[5] The pulmonary valve can be readily imaged in the short-axis when there is malposition of the great arteries with the pulmonary valve posterior to the aortic valve.^[6] A short-axis of the pulmonary valve can be obtained in most infants and young children but becomes progressively difficult in older children. However, imaging of the pulmonary valve in the short-axis is not routinely performed by most pediatric cardiologists. We hence studied the feasibility of pulmonary valve short-axis imaging by trans-thoracic echocardiography in young children.

Figure 1: (a) Modified para-sternal short axis view of a normal tricuspid pulmonary valve. The cusps are marked as A-anterior cusp, L-left posterior cusp and R-right posterior cusp. (b) Modified para-sternal short axis view of a child with mild pulmonary stenosis demonstrating a bicuspid pulmonary valve. The cusps are denoted by green arrows

Click here to view

[Additional file 1]

Supplemental Video 1: Echocardiogram loop in the modified parasternal view of a child with a small muscular ventricular septal defect demonstrating the normal tricuspid pulmonary valve.

Methods

All echocardiograms included in the study were performed between December 2020 and February 2021. We attempted to image the pulmonary valve in the short-axis in 100 consecutive children below 5 years of age in whom a complete echocardiographic study was possible. Children in whom only a screening echocardiogram was performed as well as children in whom only a limited study was possible were not considered for inclusion in the study. The common reasons for an incomplete study included very sick children, severe tachypnea, and a frightened child in whom a nonsedated study was performed. Children who had previously underwent a cardiac surgical intervention where not included. The sternotomy results in a pectus carinatum like deformity in most children and the modified parasternal short-axis view is often challenging in these children. All studies were performed by a single operator with more than 8 years' experience in performing pediatric echocardiograms. All studies were performed on an Epiq Elite ultrasound machine (Philips Medical Systems, Andover, MA, USA) using a S9-3 single crystal transducer.

Results

The age distribution of the 100 children included 18 neonates, 59 infants (1 month–2 years of age) and 23 children between 2 and 5 years of age. There were 56 female children. The heart was structurally normal in 68 children. This included two children with mild pulmonary valve pathologies which did not merit an immediate intervention and 5 infants of diabetic mother with mild ventricular hypertrophy. Infants with small and moderate sized atrial septal defects (<8 mm) were classified to have normal hearts. Simple shunt lesions (ventricular septal defects, patent arterial duct or aorto-pulmonary window) were identified in 17 children. More complex abnormalities were identified in 15 children. This included five children with tetralogy of Fallot. Three children in the entire cohort had Trisomy 21 while other genetic syndromes were detected or suspected in six other children. None of the young infants in this series had thymic hypoplasia and none of the children had proven di George syndrome. The pulmonary valve was adequately imaged in 96 of the 100 children included in this study. This included 67 of the 68 children with a structurally normal heart. The child in whom the pulmonary valve could not be imaged adequately had a skeletal dysplasia later identified as short rib thoracic dysplasia. The pulmonary valve was imaged in the short-axis in 15 of the 17 children with shunt lesions and 14 of 15 children with more complex abnormalities. Both the children with shunt lesions in whom the pulmonary valve could not be visualized were tachypneic with increased work of breathing and although adequately sedated, imaging in the parasternal windows was limited. One of the children with tetralogy of Fallot had a rotated right ventricular outflow tract and the pulmonary valve could not be visualized in the short-axis.

The pulmonary valve was tricuspid with thin leaflets in 86 children. Among the remaining children, the pulmonary valve was quadricuspid in one child with Wolff-Parkinson-White Syndrome, functionally bicuspid in one child with Edwards syndrome and bicuspid in three children [Figure 1]b and [Supplemental Video 2] including one with tetralogy of Fallot and one with a large ventricular septal defect. The pulmonary valve was tricuspid but with cusp inequality and a very small left posterior cusp resulting in moderate pulmonary regurgitation in a child with moderate pulmonary regurgitation. One child with a functionally univentricular heart had a tricuspid valve with a large left cusp and smaller right and anterior cusps [Figure 2]a and [Supplemental Video 3]. The pulmonary valve was tricuspid with thickened dysplastic leaflets in one child with a large patent ductus arteriosus and a dysplastic aortic valve and in two others with mild pulmonary valve abnormalities [Figure 2]b. The results are summarized in [Table 1].

Table 1: Summary of demographics and pulmonary valve morphology of the entire patient cohort

Click here to view

Figure 2: (a) Modified parasternal short-axis view of a child with functionally univentricular heart. The pulmonary valve is tricuspid with a larger left posterior cusp and smaller right posterior cusp as well as anterior cusp. (b) Modified parasternal short-axis view of a child with mild pulmonary stenosis. The pulmonary valve is tricuspid with mild thickening of leaflets

Click here to view

[Additional file 2]

Supplemental Video 2: Echocardiogram loop in the modified parasternal view of a child with mild pulmonic stenosis demonstrating a bicuspid pulmonary valve.

[Additional file 3]

Supplemental Video 3: Echocardiogram loop in the modified parasternal view of a child with a functionally univentricular heart and posterior pulmonary artery demonstrating a tricuspid pulmonary valve with inequality of cusps.

Discussion

Congenital heart diseases occur in approximately 1% of pregnancies. Abnormalities of the right ventricular outflow tract and pulmonary valve are estimated to complicate one fifth of congenital heart diseases.^[7] In the adult population, cardiologists have relied on three dimensional echocardiography for evaluation of pulmonary valve pathology^[8] because of the factors described earlier. However, these factors are negated by the thin and compliant chest wall in children. In addition, the presence of a large thymus in infants provides a good acoustic window and permits excellent imaging in the parasternal views.^[9]

A potential clinical application of accurately determining the morphology of the pulmonary valve is in the surgical repair of tetralogy of Fallot. In recent years, pediatric cardiologists and cardiac surgeons have focused on surgical repair without disruption of the pulmonary valve function. One of the “valve sparing” approaches utilized is intra-operative balloon pulmonary valvuloplasty.^[10] Others include utilization of a right ventricular outflow tract patch and the passage of a Hegar dilator through the annulus. It is believed that the balloon dilatation can result in splitting of the leaflet commissures. However, no study has focused on assessing the morphology of the pulmonary valve and matched this to the appropriate valve sparing surgical approach. We were able to determine the anatomy of the pulmonary valve in 4 of the 5 infants with tetralogy of Fallot who were part of this study.

Assessment of the pulmonary valve morphology aided the surgical repair of one infant in our cohort. This infant had a large ventricular septal defect and a dysplastic pulmonary valve with a small left posterior cusp. There was moderate pulmonary regurgitation and aneurysmal dilatation of the main pulmonary trunk. During the surgical repair, the surgeon performed a pulmonary trunk reduction arterioplasty and augmented the left posterior pulmonary cusp. This resulted in a reduction in the quantum of pulmonary regurgitation in the immediate postoperative echocardiogram.

It has been incorrectly claimed in the past that imaging of all the three pulmonary valve cusps is not possible during two-dimensional echocardiography.^[8] Our preliminary work suggests that imaging of the pulmonary valve in the short-axis is feasible in most young children on trans-thoracic echocardiogram. Chest wall deformities, an irritable young child and a tachypneic child present challenges with obtaining a short-axis view of the pulmonary valve.

There were several limitations in this study. The sample size was chosen arbitrarily and was small. There was an over-representation of infants in this study due to the referral pattern during the time of the study. The imaging was performed using high-end equipment which may not be widely available and which may have facilitated the ease with which the imaging was achieved. However, in the authors' experience, a satisfactory image can be obtained in most instances with patience and persistence. We had previously published the short-axis images of the pulmonary valve obtained in one of our patients in this series without focusing on the imaging technique.^[11] Although similar experience has been reported in the past,^[2] pediatric cardiologists and cardiac sonographers continue to ignore this important view.

Conclusion

The inclusion of the short-axis view of the pulmonary valve in standard imaging guidelines as well as training of pediatric cardiologists in obtaining this view would enable accurate preoperative identification of the pulmonary valve pathologies. This could in turn facilitate planning of surgical repair individualized to the anatomy of the valve cusps. The current clinical application of understanding cusp architecture of the pulmonary valve remains limited. However, focused studies should be planned where the utility of this imaging in appropriate surgical planning can be explored in detail.

Informed consent

Informed consent was obtained from the parents of the neonate who was involved in the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1.	McAleer E, Kort S, Rosenzweig BP, Katz ES, Tunick PA, Phoon CK, et al. Unusual echocardiographic views of bicuspid and tricuspid pulmonic valves. J Am Soc Echocardiogr 2001;14:1036-8.
2.	Wang SS, Xu MG, Zhuang J, Li WB, Zhang ZW, Xu G. Transthoracic echocardiographic evaluation of pulmonary valve anomalies in pediatric patients. J Ultrasound Med 2019;38:1091-6.
3.	Saremi F, Gera A, Ho SY, Hijazi ZM, Sánchez-Quintana D. CT and MR imaging of the pulmonary valve. Radiographics 2014;34:51-71.
4.	Foale R, Nihoyannopoulos P, McKenna W, Kleinebenne A, Nadazdin A, Rowland E, et al. Echocardiographic measurement of the normal adult right ventricle. Br Heart J 1986;56:33-44.
5.	Shriram Lovhale P, Misra S, Koshy T. Midesophageal short-axis views of the pulmonary valve with conventional 2-dimensional transesophageal echocardiography: A useful view in pediatric patients. J Cardiothorac Vasc Anesth 2017;31:e36-8.
6.	Mahle WT, Gonzalez JH, Kreeger J, Marx G, Duldani G, Silverman NH. Echocardiography of transposition of the great arteries. Cardiol Young 2012;22:664-70.
7.	Sulejmani F, Pokutta-Paskaleva A, Salazar O, Karimi M, Sun W. Mechanical and structural analysis of the pulmonary valve in congenital heart defects: A presentation of two case studies. J Mech Behav Biomed Mater 2019;89:9-12.
8.	Anwar AM, Soliman O, van den Bosch AE, McGhie JS, Geleijnse ML, ten Cate FJ, et al. Assessment of pulmonary valve and right ventricular outflow tract with real-time three-dimensional echocardiography. Int J Cardiovasc Imaging 2007;23:167-75.
9.	Joshi P, Vasishta A, Gupta M. Ultrasound of the pediatric chest. Br J Radiol 2019;92:20190058.
10.	Robinson JD, Rathod RH, Brown DW, Del Nido PJ, Lock JE, McElhinney DB, et al. The evolving role of intraoperative balloon pulmonary valvuloplasty in valve-sparing repair of tetralogy of fallot. J Thorac Cardiovasc Surg 2011;142:1367-73.
11.	Krishna MR. ALCAPA – A reversible cause of dilated cardiomyopathy in infants. Indian J Pediatr 2022;89:197.