Presenting novel 2D echocardiographic views for pulmonary valve assessment in tetralogy of fallot patients

Abstract

Background

Tetralogy of Fallot (TOF) is considered one of the most common surgically repaired congenital heart conditions. Continuous improvements in surgical techniques have aimed at preserving the pulmonary valve (PV). Therefore, evaluating PV morphology and the Right Ventricular Outflow Tract (RVOT) is clinically significant as it is enlightening in selecting therapeutic strategies. This study aims to clarify the practical use of 2D transthoracic echocardiography (TTE) in detecting 2-leaflet valves versus 3-leaflet valves and compare the assessment of PV by 2D TTE with surgical assessment.

Methods

A total of 52 TOF patients scheduled for surgical repair were prospectively included. PV morphology was assessed preoperatively using a novel 2D TTE technique, using subclavicular and subcostal en-face views. Echocardiographic findings were compared with intraoperative surgical visual assessments. Sensitivity, specificity, accuracy, and Cohen’s kappa coefficient were calculated to determine the agreement between 2D TTE and surgical findings in identifying the number of cusps of the pulmonary valve.

Results

The sensitivity, specificity, and accuracy of echocardiography in identifying bicuspid pulmonary valves using the previously mentioned echocardiographic views were 97.4%, 61.54%, and 88.46%, respectively. Cohen’s kappa coefficient was 0.657. The sensitivity, specificity, and accuracy of echocardiography in identifying tricuspid PV using the previously mentioned echocardiographic views were 63.64%, 95.12%, and 84.46%, respectively. The Cohen’s kappa coefficient was 0.629. Echocardiography could not detect the mono-cuspid morphology of PV in any case; however, two patients had mono-cuspid PV morphology according to the surgeon’s visual assessment.

Conclusion

2D TTE can be considered an accurate method for evaluating pulmonary valve (bicuspid vs. tricuspid) in patients with Tetralogy of Fallot when specific views are utilized.

Clinical trial number

Not Applicable.

Background

Tetralogy of Fallot (TOF) is considered one of the most common surgically repaired congenital heart conditions [1]. The clinical presentation varies, and symptoms such as reduced physical capacity and persistent cyanosis are directly related to the obstruction of the right ventricular outflow tract (RVOT) [2]. Most patients, especially infants, are asymptomatic and therefore left untreated, with only 10% surviving beyond the age of 20 years. However, it is expected that 90% of patients who undergo definitive surgery in childhood will survive up to the fifth decade of life [3]. Surgical repair aims to close the shunt and relieve the obstruction in the RVOT [4]. Continuous improvements in surgical techniques have focused on preserving pulmonary valve (PV) function to mitigate long-term consequences [5]. Guiding surgical decisions and maximizing patient outcomes depend on determining PV morphology prior to surgical repair in TOF patients. A precise preoperative assessment can influence the surgical strategy, including the decision to use a transannular patch (TAP) with significant long-term consequences or to preserve the PV [6]. In a study by Chako et al., bicuspid valves were the most commonly observed PV morphology in TOF patients (53.3%). PV atresia accounted for 16.3% of cases, followed by the absence of pulmonary valve in 6.3% of patients. Tricuspid valve morphology was observed in 10% of patients, while none had unicuspid or quadricuspid valves [7].

Surgical eyeball assessment has traditionally been considered the gold standard for evaluating PV morphology [8]. However, three-dimensional transthoracic echocardiography (3D TTE) has recently gained attention as a less invasive modality for assessing PV morphology [8]. Despite providing more accurate visualization of anatomical structures, 3D TTE has limitations such as operator dependency, time-consuming nature, and higher costs, making it less practical in clinical settings. Historically, two-dimensional TTE has been considered inferior in assessing PV morphology, although it has advantages over 3D TTE regarding image quality, cost-effectiveness, and being less operator-dependent [9].

In this study, we aim to clarify the practical use of 2D TTE novel views in detecting 2-leaflet valves vs. 3-leaflet valves and compare the PV morphology obtained by 2D TTE with the surgical assessment to determine the accuracy of this method.

Methods

Data collection

A total of 52 TOF patients scheduled for surgical repair were prospectively included in the study. These patients had no additional comorbidities and had not undergone previous surgical interventions before their visit. Age, weight, PV morphology assessed by echocardiography, and PV morphology evaluated by the surgeon’s visual assessment were collected.

Echocardiography technique

Two-dimensional Transthoracic Echocardiography was performed using the ACUSON X700 echocardiography system by Siemens, Munich, Germany. In addition to the routine full echocardiographic assessment, the PV enface view was obtained using two specific windows. In the subclavicular enface view, the cursor was positioned perpendicularly to the chest at the 3 o’clock setting (Fig. 1). This allowed for visualization of the circular structure of the pulmonary artery, with the appearance of a bicuspid or tricuspid valve and leaflet thickening (Fig. 2). To obtain the subcostal enface view, the cursor was placed in the subcostal position with a 45–60 degree angle tilt toward the anterior chest wall (Fig. 3). These two modalities were combined to evaluate the patients’ morphology and size of the PV.

Surgical repair

The TOF patients underwent surgical repair by a pediatric cardiothoracic surgery team. The surgical team was not informed of the echocardiographic morphology in advance. The surgeon’s direct view of the valve during pulmonary artery repair was documented for further analysis and comparison.

This study aims to determine the practical utility of 2D TTE in distinguishing between 2-leaflet valves and 3-leaflet valves and to compare the PV morphology obtained through 2D TTE with the surgical assessment in order to evaluate the accuracy of this method. Since the surgical outcome of TOF total correction is highly dependent on the morphology of the pulmonic valve, preoperative determination of the PV morphology is of great importance to the surgeons.

Fig. 1

The probe’s notch position is notable in the subclavicular en-face view (A, B)

Fig. 2

Subclavicular en-face view indicating bicuspid [1, 2] pulmonary valve (A) and tricuspid [1,2,3] pulmonary valve (B)

Fig. 3

The subcostal en-face view (A, B), the position of the probe’s notch is notable.^*

^*In order to achieve diagnostic-quality images from the subcostal view, a rotation of 15 degrees in a clockwise direction may be required for certain patients. Nevertheless, no additional probe rotation is necessary for the subclavicular view. It is important to note that, owing to anatomical variations, some patients may need minimal adjustments to these angles.

Statistical analysis

The data were analyzed using SPSS version 22. Descriptive statistics summarized the characteristics of the patients, with categorical variables displayed as percentages. Specificity, sensitivity, accuracy, and Cohen’s kappa coefficient were calculated to assess 2D echocardiography’s performance in determining the pulmonic valve’s morphology (mono-cuspid, bicuspid, or tricuspid).

Results

The study included 52 consecutive patients undergoing surgical correction of TOF at Children’s Medical Centre in Tehran, Iran. The study population appeared to be homogeneous, with 48.1% females. The median age at admission was 27.3 months (range: 2.50–75.00), and the median weight was 5.2 kg (range: 1.6–29.5).

Two weeks before the surgical TOF repair, the pulmonic valve was visualized using 2D echocardiography by a pediatric cardiologist expert. All images were of excellent quality, allowing for clear visualization of the entire view. Among the 52 visualized pulmonic valves, 43 (82.7%) were reported to have two leaflets, while the remaining nine (17.3%) were observed to be tricuspid. Consequently, the 2D echocardiography method was used to identify the morphology of the pulmonic valve regarding leaflet shape and number in all 52 patients. Bicuspid pulmonic valves were significantly more prevalent than tricuspid valves in this population.

The same study group was directly evaluated for pulmonic valve morphology during surgery. As can be observed in Table 1, among the 52 patients, 39 were found to have a bicuspid valve, consistent with the 2D echocardiography analysis of 43 patients. Eleven patients were observed to have a tricuspid valve, while previous echocardiographic studies had reported nine. In addition to the expected bicuspid and tricuspid valve groups, two patients could not be classified due to the surgeon’s assessment of a mono-cuspid view of their valve, which was initially interpreted as a bicuspid valve. In summary, among the 52 patients who underwent direct visualization during surgery, 75% had two leaflets, 21.2% had three leaflets, and 3.8% had one leaflet in their pulmonic valve.

The sensitivity, specificity, and accuracy of 2D echocardiography in determining bicuspid pulmonic valve morphology using the subcostal and subclavicular views were 97.4%, 61.54%, and 88.46%, respectively, with a Cohen’s kappa coefficient of 0.657. The sensitivity, specificity, and accuracy of 2D echocardiography for tricuspid pulmonic valve morphology were 63.64%, 95.12%, and 84.46%, respectively, with a Cohen’s kappa coefficient of 0.629. Notably, 2D echocardiography using these views did not identify any mono-cuspid morphology of the pulmonic valve; however, two patients were found to have mono-cuspid morphology based on the surgeon’s assessment.

Table 1 Morphology of PV

Discussion

2D TTE is the standard initial diagnostic approach and is widely recognized as a cost-effective tool for heart valve evaluation. Yet, assessing the pulmonary valves with conventional 2D TTE views remains challenging due to their anatomical location beneath the sternum and the limitations of ultrasound penetration through the chest wall and pulmonary tissue [10]. A study on PV assessment by Anwar et al. showed that diagnostic-quality images of the PV leaflets are obtained in only half of the patients while using parasternal long axis view (PLAX) and parasternal short axis view (PSAX) [11]. However, the findings of this study suggest that the newly implemented 2D TTE en-face views offer a reliable method for assessing the number of leaflets in the pulmonary valve in individuals with Tetralogy of Fallot. The sensitivity and specificity metrics reported in this study for bicuspid (97.4%, 61.54%) and tricuspid valve (63.64%, 95.12%) morphologies indicate that 2D TTE could offer reliable accuracy comparable to the surgical visual assessment. Traditionally, surgical visual assessment has been considered the definitive method for PV evaluation; however, it is inherently invasive and restricted to intraoperative situations [8]. Three-dimensional transthoracic echocardiography has alleviated certain limitations by offering detailed spatial representations of the PV. Nonetheless, 3D TTE is resource-intensive, reliant on operator skill, and less accessible, especially in low-resource environments [12].

In contrast, 2D TTE, as shown in this study, provides an efficient, non-invasive, and readily available option for preoperative PV evaluation. These results align with earlier research highlighting the feasibility and accessibility of 2D echocardiography imaging in cardiac diagnosis and preserving the pulmonary valve during surgical repair in TOF patients [5].

The lower sensitivity for tricuspid valves (63.64%) and the inability to identify mono-cuspid valves could be due to specific tissue characteristics and thickness of the cusps. These results are consistent with previous research indicating challenges in identifying rare PV morphologies through 2D imaging [12]. This study demonstrates that 2D TTE may reliably assess PV leaflets, supporting its inclusion in clinical protocols, especially in resource-limited settings where 3D imaging may be impractical.

Limitations

While our study offers valuable insights, it is crucial to address its limitations. The single-center design and small sample size significantly restrict the generalizability of our findings. To improve the relevance of our results for a broader population, we recommend larger multicenter studies that can confirm our findings in diverse patient groups and medical contexts. We acknowledge that while our research maintained high image quality, practical applications can vary due to patient anatomy, operator skill, and equipment discrepancies. Due to the innovative nature of our echocardiographic method, only one experienced cardiologist performed the imaging to ensure consistency, and a single pediatric cardiac surgeon assessed the pulmonary valve morphology. As a result, interobserver agreement could not be tested in this study. Future studies with multiple observers across different centers are needed to evaluate reproducibility and generalizability. Another notable limitation of the study is its focus on bicuspid and tricuspid valves, while mono-cuspid valves, which pose diagnostic challenges for 2D TTE, receive relatively less attention. Future studies may investigate the integration of 2D TTE with other imaging techniques, such as cardiac magnetic resonance imaging, to provide a more comprehensive evaluation of PV anatomy [8]. Moreover, advancements in image processing techniques and the use of artificial intelligence and machine learning may further improve the diagnostic effectiveness of 2D imaging [9].

Conclusion

In conclusion, this study demonstrates that the newly applied two-dimensional echocardiographic techniques can be considered an accurate method for evaluating pulmonary valve morphology in TOF patients when specific views are utilized. These views show good agreement with direct visualization during surgery and can be regarded as a reliable method for preoperative assessment. The findings from this study could potentially enhance surgical planning and outcomes for patients with TOF who underwent preoperative 2D TTE evaluation. Further research is needed to broaden the application of these views and address the challenges associated with diagnosing unusual pulmonic valves.