Congenital heart disease (CHD) remains the most common birth defect, affecting approximately 0.8% to 1.2% of live births across the globe [1]. There has been an increasing birth prevalence of CHD last decade, with a rise from 4.55 per thousand in 1970–1974 to 9.41 per thousand in 2010–2017 [2]. CHD is characterized by a structural abnormality of the heart and/or great vessels that is present at birth [2]. Almost one-third of all major congenital anomalies consist of heart defects [3], and CHD malformations can occur as single lesions or in combination with other heart defects [4]. Isolated or single lesions include atrial septal defects, ventricular septal defects, and pulmonary stenosis; complex or combination lesions include atrioventricular septal defects, tetralogy of Fallot, and transposition of the great arteries (TGA) [4, 5]. In 2017, atrial septal defects and ventricular septal defects were reported as the most common subtype of CHD, accounting for almost 30% of all cases of CHD [1]. With only about 15% of CHD cases being attributable to a known cause [4], it presents a significant challenge in developing countries, where both the incidence and mortality rates of CHD have been rising [1]. Therefore, early detection and diagnosis as well as timely interventions are critical to reducing morbidity and mortality [5].

However, the diagnosis of CHD is challenging especially among children due to the numerous clinical signs including, dyspnea, cough, and failure to thrive, which can be misinterpreted as symptoms of other illnesses until the diagnosis of CHD is confirmed [6]. Taking a thorough medical history and performing a physical examination remain integral aspects of diagnosing CHD. Despite asymptomatic and normal physical examination, many children are diagnosed with CHD necessitating the use of other diagnostic modalities for early detection and intervention as clinically required in these subsets [7].

Clinical assessment along with chest radiographs and electrocardiograms remain the core of evaluating children with suspected CHD [8]. However, due to the advent of advanced imaging technologies such as echocardiography, computed tomography (CT), and magnetic resonance imaging (MRI), chest radiographs and electrocardiograms have become traditional approaches [9]. Especially with echocardiography being considered as the primary diagnostic tool, the utility of these imaging modalities for the preliminary diagnosis of CHD is in a decreasing trend. Despite advanced imaging options, chest radiographs and electrocardiograms remain the most accessible and cost-effective techniques for the initial assessment of suspected CHD. Especially in developing countries, these imaging modalities can still be valuable tools for the detection of CHD.

The effectiveness of advanced imaging modalities including echocardiography, CT, and MRI in the diagnosis and management of CHD is well-established [9]. Advanced computer and medical imaging technologies are often employed to obtain the local hemodynamics of the investigated site and illustrate the hemodynamic characteristics [10]. However, there is a paucity of studies demonstrating the significance of chest radiographs and electrocardiograms in the detection of CHD. A prior study conducted in the United States demonstrated the advantages of chest radiographs and electrocardiograms in diagnosing certain cardiac defects precisely and emphasized that these diagnostic tools should be retained as a part of the routine evaluation of CHD [8]. Another study conducted in Egypt examined the value of chest radiographs and electrocardiograms in the evaluation of patients with heart murmurs in the presence of echocardiography [11]. Nonetheless, to the best of our knowledge, there is no single study that demonstrates the role of these diagnostic tools for the assessment of the hemodynamics of CHD.

The study aimed to evaluate the role of chest radiographs and electrocardiograms in predicting the hemodynamics of CHD, taking echocardiography as the diagnostic standard.

This was a retrospective study carried out in the Department of Pediatric Cardiology at Max Super Specialty Hospital in New Delhi, India. Ethics approval was attained from the Institutional Ethics Committee, Devki Devi Foundation (Reference No: RS/MSSH/DDF/SKT-2/IEC/PED-CARDIO/20-44), prior to study commencement. All patients with a diagnosis of CHD who had undergone any form of cardiac intervention, either surgical or nonsurgical between September 2019 and September 2020, were included in this study. The CHD included in this study are outlined in Table 1. However, those patients who had not undergone any cardiac intervention, either invasive or noninvasive, and were managed medically were excluded.

All data were collected pre-operatively or pre-intervention, and data collection was conducted in a pre-designed and pre-tested proforma. All three tests (i.e., chest radiographs, electrocardiograms, and echocardiography) were conducted on the same day for each patient. The evaluation of chest radiographs, electrocardiograms, and echocardiography was performed within three days of the initial assessment. The chest radiographs and electrocardiograms were evaluated by three pediatric cardiologists, of which two were blinded about the diagnosis, and the results were compared with the final diagnosis of echocardiography. Similarly, echocardiography was conducted by an experienced pediatric cardiologist, and the images were cross-verified by two pediatricians who were blinded about the diagnosis.

Chest radiographs in anterior-posterior, posterior-anterior, and lateral view were evaluated for the following parameters, namely situs, cardiac position, thymic shadow, cardiomegaly, right atrium enlargement, left atrium enlargement, right ventricle enlargement, left ventricle enlargement, position of the aortic knuckle, ascending aorta dilatation, descending aorta dilatation, main pulmonary artery dilatation, right pulmonary artery dilatation, and left pulmonary artery dilatation (Figure 1). Similarly, radiographic features for pulmonary plethora, pulmonary oligemia, pulmonary arterial hypertension, and pulmonary venous hypertension were evaluated. The criteria used for chest radiographs were as per the standard guidelines [12].

The 12 lead electrocardiograms were evaluated for sinus rhythm, rate, P-axis, QRS axis, PR interval, QTc interval, QRS duration, right atrial enlargement, left atrial enlargement, bundle branch block, and biventricular hypertrophy as per standard guidelines [13]. Electrocardiogram features for volume overload and pressure overload of the right and left ventricles were evaluated.

The findings of chest radiographs and electrocardiograms were compared with the findings of echocardiography, taking this tool as the diagnostic standard. The findings from echocardiography were validated using standardized recommendations. The echocardiographic parameters were taken using cardiac Z score as the reference values for the pediatric population [14]. The study by Kampmann et al. [14] was referred for M mode measurements, and the article by Pettersen et al. [15] was referred to for other variables such as mitral valve, left ventricle, aortic valve, aortic arch, pulmonary valve, and pulmonary arteries. Moreover, the pediatric echocardiography quantification criteria were taken from the article by Lopez et al. [16]. The detailed criteria used for chest radiographs, electrocardiograms, and echocardiography in this study are summarized in Tables 2, 3, and 4, respectively.

A total of 50 patients (36 male, 14 female), aged 2 months to 23 years, who had a diagnosis of CHD, were included in this study. The median age of the participants was 1.9 years (interquartile range 4.95). Chest radiographs and electrocardiograms, as well as the diagnostic gold standard echocardiography, had been performed for all patients. The examples of pathologies measured on chest radiographs and corresponding changes in electrocardiograms are presented in the supplementary material (Table S1).

Given that undiagnosed CHD can lead to life-threatening cardiovascular collapse and cardiac arrest, which are leading causes of death in children, screening and early detection of CHD are vital [7, 18]. Traditional teaching methods always highlight chest radiographs and electrocardiograms as essential tools that add substantial value to the diagnosis of cardiac diseases in children [11]. However, the role of chest radiographs and electrocardiograms in the detection of CHD is still questionable due to previous studies showing low sensitivity and specificity of these diagnostic tools [8, 19, 20]. Nonetheless, prior studies do recommend routine use of chest radiographs and electrocardiograms for the preliminary detection of CHD [8, 11].

The current study demonstrated the role of chest radiographs and electrocardiograms in predicting the hemodynamics of CHD, taking echocardiography as the diagnostic standard. CHD with right sided obstructive lesions (tetralogy of Fallot, pulmonary stenosis), aortic stenosis, and pulmonary artery hypertension cause pressure overload, whereas, left to right shunts such as ventricular septal defect and patent ductus arteriosus cause volume overload. The hemodynamics of these pressure overload and volume overload conditions can be assessed by chest radiographs and electrocardiograms. Chest radiographs had the highest sensitivity, specificity, and accuracy, with all being 100.00%, in detecting situs and cardiac position. There was a very good agreement between chest radiographs and echocardiography in the detection of both situs and cardiac position, while moderate agreement was observed for the detection of cardiomegaly, position of aortic knuckle, main pulmonary artery dilation, and right pulmonary artery dilation. Electrocardiograms had a high sensitivity of 100.00%, but modest specificity and accuracy for the detection of left ventricle pressure overload. For the detection of left atrial enlargement and left ventricle volume overload, electrocardiograms had high specificity but low sensitivity and modest accuracy. There was a moderate agreement between electrocardiograms and echocardiography in the detection of right ventricle pressure overload and left ventricle volume overload. Varied results were obtained for other chest radiograph and electrocardiogram variables in terms of sensitivity, specificity, accuracy, and concordance with echocardiography. Nonetheless, the study findings indicate that chest radiographs and electrocardiograms alone are not adequate for the assessment of hemodynamics of CHD and reinstates the recommendation that in addition to routine chest radiographs and electrocardiograms, echocardiography should be performed.

In this study, the sensitivity and specificity of chest radiographs for the detection of cardiomegaly were 85.00% and 66.67%, respectively with a positive predictive value of 62.96% and a negative predictive value of 86.96%. In a study conducted by Satou et al. [21], chest radiographs had a high specificity (92.30%) and negative predictive value (91.10%), a low sensitivity (58.80%) and positive predictive value (62.50%) in predicting cardiac enlargement in children. Nonetheless, the presence of cardiomegaly can be suspected if the cardiothoracic ratio is > 60% in neonates, > 55% in infants, and > 50% in children. In this study, accuracy of the chest radiograph in detecting cardiac chamber enlargement was 70.00% for right and left atrium, 50.00% for right ventricle, and 68.00% for left ventricle, which was lower than that reported in a prior study [11]. Tumkosit et al. [22] reported moderate to high accuracy (73–92%) and specificity (61–96%) of chest radiographs to characterize pulmonary vascularity patterns, with moderate to good agreement (κ = 0.53–0.67). In our study, although high accuracy (82.00%) and specificity (95.24%) were obtained for the detection of pulmonary arterial hypertension, there was poor agreement between chest radiographs and echocardiography (κ = 0.1).

In the current study, the sensitivity, specificity, and accuracy of electrocardiogram in detecting right atrial enlargement were 53.57%, 77.27%, and 64.00%, respectively, which were lower than the 100.00%, 97.70%, and 98.50% reported in a prior study [11]. The differences in the results could be attributed to the differences in sample size as well as the age group of patients included in the study. There is also a possibility of differences in measurement methods used; while this study used standard criteria for detecting right atrial enlargement [13], the criteria used have not been indicated in the prior study [11].

Electrocardiogram had a high sensitivity (100.00%), modest specificity (54.17%), and accuracy (56.00%) for the detection of left ventricle pressure overload, but modest sensitivity (50.00%), specificity (62.50%), and accuracy (62.00%) for detecting biventricular hypertrophy. Murphy et al. [23] suggest that the use of a single criterion to detect left ventricular hypertrophy is often ineffective when the patients under study have diverse cardiac diseases and recommend using methods that integrate multiple electrocardiographic criteria.

While this study was focused on the role of chest radiographs and electrocardiograms in predicting the hemodynamics of CHD taking echocardiography as the diagnostic standard, several prior studies have investigated the accuracy of these tools in detecting several cardiac defects. Danford et al. [8] demonstrated that chest radiographs and electrocardiograms had no independent advantage for defect-specific diagnosis of cardiac murmurs in children. The findings of many prior studies indicate that chest radiographs and electrocardiograms have low sensitivity and specificity that can result in the misinterpretation of diagnosis for CHD [7, 19, 20, 22, 24, 25]. In a retrospective study by Laya et al. [19], the authors concluded that chest radiograph alone is not diagnostic of specific congenital cardiac lesions. Similarly, Fonseca et al. [26] reported that chest radiography had a low sensitivity for structural heart disease, and concluded that chest radiography does not function as a screening test for neonates with suspected heart disease, particularly in small or premature neonates. Birkebaek et al. [25] evaluated the diagnostic value of chest radiography and electrocardiography while evaluating if asymptomatic children with a cardiac murmur had heart disease as defined by echocardiography. However, their study demonstrated no role of these diagnostic tools in the detection of heart disease. Corroborating the findings of the aforementioned studies, this study identified the need for other diagnostic tools in addition to chest radiographs and electrocardiograms for the preliminary diagnosis of CHD.

To the best of our knowledge, this study is one of the first to evaluate the role of chest radiographs and electrocardiograms in predicting the hemodynamics of CHD, taking echocardiography as the diagnostic standard. Set in a real-world clinical setting, this study illustrates the importance of these readily available and economically viable imaging tools for predicting the hemodynamics of CHD, especially in resource-constraint settings. Nonetheless, this study has a few limitations. As the data were collected retrospectively from the hospital records, the skills of the individuals performing and reporting the chest radiographs, electrocardiograms, and echocardiography were not assessed, which could have increased the technical variability. However, the chest radiographs and electrocardiograms were evaluated and compared with the final diagnosis of echocardiography by a pediatric cardiologist in this study. In recognizing the limitations of our study, including the exclusion of specific blood flow criteria, future research can fuse prospectively and comprehensively into this dimension of CHD hemodynamics. Due to the retrospective nature of this study, there were a number of patients who could not be tracked for further evaluation. Consequently, this led to a small sample size that, although modest, was deemed sufficient (n = 50). Prospective clinical studies that include large sample sizes are needed to support or refute the findings from this study regarding the hemodynamic evaluation of CHD using chest radiographs and electrocardiograms, as compared to echocardiography. In the context of evolving diagnostic imaging for CHD, our study, while focusing on chest radiographs and electrocardiograms, acknowledges the need to discuss the current relevance and utility of these traditional tools alongside advanced modalities like MRI, and CT scan. Future research can explore the synergy between these techniques for comprehensive CHD assessment.