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Background
Severe scoliosis may impair cardiac structure and function. This study aims to evaluate the cardiac structural and functional changes in patients with severe thoracic scoliosis at rest, using echocardiography to inform perioperative strategies.
Methods
This retrospective cohort analysis included 294 patients with idiopathic scoliosis (IS) characterized by primary thoracic curvature and no history of previous spinal surgery. The study included 97 patients with severe scoliosis (defined as a Cobb angle ≥ 90°) and 197 patients with a Cobb angle < 90°, who were categorized as Non-severe scoliosis. General data, including age, gender, height, weight, BMI, and primary thoracic curve characteristics, were collected for all patients. Subgroup analyses were conducted based on age, gender, Cobb angle, and curve direction. Cardiac metrics, including structural and functional parameters, were compared, and correlations between Cobb angle and cardiac indicators in severe scoliosis were assessed.
Results
Patients with severe scoliosis exhibited significantly reduced cardiac parameters, including left ventricular diastolic diameter (LVDd), right ventricular diastolic diameter (RVDd), interventricular septal thickness (IVST), left ventricular posterior wall thickness (LVPWT), ejection fraction (EF), and fractional shortening (FS) (p < 0.05). Subgroup analysis revealed lower LVDd and cardiac index (CI) in patients with Cobb angles ≥ 120° compared to 90–120° (p < 0.05). The direction of the thoracic curve did not significantly impact cardiac structure or function (p > 0.05). Patients older than 18 years had significantly larger cardiac structural parameters than younger patients, although cardiac function remained similar. Male patients exhibited greater right heart dimensions compared to females. Correlation analysis demonstrated a negative association between Cobb angle and LVDd and CI (p < 0.05).
Conclusions
Severe thoracic scoliosis significantly affects cardiac structure and function at rest, primarily impacting left ventricular dimensions and cardiac index. Age and gender influence specific cardiac structural parameters but have a limited impact on cardiac function. Preoperative assessments should prioritize LVDd and CI for a thorough evaluation of cardiac health in these patients. The direction of the primary thoracic curve does not significantly influence cardiac structure or function. The severity of the spinal deformity, rather than the curvature direction, is the main determinant of its impact on cardiac health.
Background
Severe scoliosis is a complex three-dimensional spinal deformity characterized not only by pronounced lateral curvature and thoracic distortion but also by axial vertebral rotation [1]. Historically, scoliosis with a Cobb angle exceeding 80° has been considered severe [2, 3]. In 2017, Xie et al. [4] redefined severe scoliosis as a condition with a Cobb angle greater than 90° in the coronal and/or sagittal planes, which spinal surgeons now accept [5, 6]. Its etiology is widely considered to be a multifactorial condition involving genetic, biomechanical, neuromuscular, and hormonal factors [7, 8]. Severe scoliosis may also lead to twisting, angulation, and displacement of blood vessels. Furthermore, reduced thoracic volume can result in impaired cardiopulmonary function [9, 10, 11–12] caused by mechanical compression, ultimately reducing life expectancy. Severe scoliosis complicates anesthesia management and increases perioperative risks [13]. Structural cardiac problems or heart failure enhance anesthesia and operation risks, making severe spinal deformity surgery more difficult.
Although the effects of severe scoliosis on pulmonary function have been extensively studied [14, 15, 16–17], the specific impact on cardiac structure and function remains controversial. Liang et al. [18] suggested that severe scoliosis influences cardiac structure without affecting function, while Li et al. [2, 19] reported that both left and right heart functions are compromised in severe scoliosis patients. Despite growing interest in the cardiopulmonary consequences of scoliosis, much of the current literature remains limited by small sample sizes, a predominant focus on mild-to-moderate deformities, and the lack of detailed subgroup analyses based on curve severity, direction, or patient demographics. Notably, very few studies have focused specifically on individuals with Cobb angles ≥ 90°, who represent a distinct clinical subgroup with pronounced anatomical distortion and an elevated risk of significant cardiopulmonary compromise. To address these limitations, the present study analyzes echocardiographic changes in a large cohort of patients with idiopathic scoliosis, with particular attention to those with severe thoracic curvature, and through the application of comprehensive, multidimensional subgroup analyses. Accordingly, this study aims to address four key objectives: (1) To investigate whether severe thoracic scoliosis (Cobb angle ≥ 90°) significantly alters resting cardiac structure and function compared to less severe deformities; (2) To examine the relationship between increasing curve magnitude—particularly beyond 120°—and specific echocardiographic parameters such as left ventricular end-diastolic diameter (LVDd) and cardiac index (CI); (3) To explore whether the direction of the primary thoracic curve (left- vs. right-convex) is associated with differential cardiac effects; (4) To assess the impact of demographic factors, including age and sex, and to determine the correlation between scoliosis severity and echocardiographic findings. By systematically addressing these specific questions, the present study aims to elucidate the cardiac consequences of severe thoracic scoliosis and to generate clinically relevant evidence that may inform perioperative risk stratification and guide individualized management strategies.
Methods
Study design and subjects
This retrospective study was approved by the Ethics Committee of the Second Affiliated Hospital of Kunming Medical University. This retrospective cohort study investigated 294 patients with idiopathic scoliosis (IS) and primary thoracic curvature who underwent their first spinal corrective surgery at Kunming Medical University’s Second Affiliated Hospital from January 2018 to December 2023. The thoracic Cobb angle classified patients as severe scoliosis or Non-severe scoliosis on preoperative standing posteroanterior radiographs. Patients in the severe scoliosis group met the following criteria: IS diagnosis, main thoracic curve, Coronal Cobb angle ≥ 90°, and no prior spinal surgical history. Patients in the Non-severe scoliosis group met the same criteria, except for a coronal Cobb angle < 90°. Both groups were excluded if they had (1) congenital heart disease (confirmed by a team of 3 cardiologists through clinical evaluation and echocardiography), (2) congenital scoliosis, (3) spinal deformities from tuberculosis, fractures, or other etiologies, (4) any known cardiovascular disease (e.g., hypertension, cardiomyopathy), (5) pulmonary disorders (e.g., chronic obstructive pulmonary disease, restrictive lung disease), (6) systemic diseases (e.g., diabetes mellitus, chronic kidney disease), (7) neuromuscular conditions or (8) incomplete preoperative diagnostic data. A total of 97 patients comprised the severe scoliosis group, whereas 197 patients were assigned to the control group.
Radiological measurement
All patients underwent preoperative standing full-length anteroposterior and lateral spine radiographs. The primary thoracic Cobb angle was independently measured by three experienced spine surgeons using the standard Cobb method to ensure consistency and minimize measurement error [20, 21]. These measurements were averaged to determine the final value.
Echocardiographic measurement
All patients receiving scoliosis correction surgery at our institution had routine cardiac assessment with preoperative transthoracic echocardiography (TTE). This technique follows institutional guidelines for severe spinal deformities (Cobb angle ≥ 90°) and addresses baseline cardiac function and perioperative treatment for all surgical candidates. TTE exams were done by a team of two clinical cardiology and echocardiography-trained sonographers using a standard imaging technique. Each echocardiogram was analyzed by a team of three experienced cardiologists with echocardiography skills. This centralized interpretation decreased inter-observer variability and ensured uniformity.
The recorded parameters included cardiac structural metrics such as left ventricular diastolic diameter (LVDd), left atrial diameter (LAD), right ventricular diastolic diameter (RVDd), right atrial diameter (RAD), right ventricular outflow tract (RVOT), interventricular septal thickness (IVST), and left ventricular posterior wall thickness (LVPWT). Additionally, cardiac functional metrics such as ejection fraction (EF), fractional shortening (FS), and cardiac index (CI) were measured.
Grouping
This study investigated the cardiac effects of the primary thoracic curve in patients with and without severe scoliosis. Patients with a Cobb angle ≥ 90° were classified as the severe scoliosis group (Group S), while those with < 90° served as Non-severe scoliosis group(Group N).
To assess the impact of scoliosis severity, Group S was further divided into Group S1 (90° ≤ Cobb angle < 120°) and Group S2 (Cobb angle ≥ 120°). To explore the influence of curve direction, patients with leftward convexity were assigned to Group S-L, and those with rightward convexity to Group S-R.
To evaluate the effects of age, patients ≤ 18 years were categorized as the pediatric (Group P), and those > 18 years as the adult (Group A). Gender-based analysis was performed by grouping male and female patients into Group M and Group F, respectively.
Statistical analysis
Statistical analysis was conducted using GraphPad Prism 8.0.2 (GraphPad Software Inc., USA). Continuous variables were expressed as mean ± standard deviation. Group comparisons were performed using independent samples t-tests for continuous data and chi-square tests for categorical data. Correlation analysis assessed the relationship between the main thoracic Cobb angle and cardiac parameters in severe scoliosis patients. A two-sided p-value < 0.05 was considered statistically significant.
Results
Demographics and baseline characteristics
The study included 97 severe scoliosis patients, comprising 65 females and 32 males. The average age was 15.90 ± 6.91 years, with a mean coronal Cobb angle of 114.20 ± 19.42°. The Non-severe scoliosis group included 197 patients—152 females and 45 males. The average age was 14.94 ± 4.78 years, with a mean coronal Cobb angle of 54.31 ± 11.66°. Gender, age, BMI, and main thoracic curve direction did not differ between groups (p > 0.05). However, the severe scoliosis group had significantly lower weight and height than the Non-severe scoliosis group (Table 1).
Table 1. Baseline demographics of group S and group N
index | Group S | Group N | P-value |
|---|---|---|---|
No. Of patients | 97 | 197 | |
Sex(M/F) | 32/65 | 45/152 | 0.063 |
Age(y) | 15.90 ± 6.91 | 14.94 ± 4.78 | 0.169 |
Weight(kg) | 35.74 ± 12.25 | 41.33 ± 11.50 | < 0.0001 |
Height(cm) | 138.20 ± 17.97 | 155.40 ± 15.52 | < 0.0001 |
BMI | 18.34 ± 4.42 | 18.59 ± 3.49 | 0.592 |
Cobb’s angle(degree) | 114.20 ± 19.42 | 54.31 ± 11.66 | < 0.0001 |
Side of main thoracic curvature(L/R) | 24/73 | 45/152 | 0.718 |
Statistical significance was set at P < 0.05
Group S, severe scoliosis group; Group N, Non-severe scoliosis group
Impact of severe scoliosis on cardiac structure
In the severe scoliosis group, cardiac structure indicators such as LVDd (35.30 ± 4.96 mm vs. 38.50 ± 4.35 mm, p < 0.0001), RVDd (17.62 ± 3.21 mm vs. 18.57 ± 2.67 mm, p = 0.008), IVST (6.77 ± 1.57 mm vs. 7.31 ± 1.16 mm, p = 0.001), and LVPWT (6.78 ± 1.35 mm vs. 7.23 ± 1.13 mm, p = 0.004) were significantly lower compared to the Non-severe scoliosis group (Fig. 1a, c, f, g).
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Fig. 1
Comparison of cardiac structural and function indices between Group S and Group N
*P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; ns, Not significant
Group S: severe scoliosis group; Group N: Non-severe scoliosis group; LVDd: Left Ventricular Diastolic Diameter; RVDd: Right Ventricular Diastolic Diameter; IVST: Interventricular Septal Thickness; LVPWT: Left Ventricular Posterior Wall Thickness; LAD: Left Atrial Diameter; RAD: Right Atrial Diameter; RVOT: Right Ventricular Outflow Tract EF: Ejection Fraction; FS: Fractional Shortening; CI: Cardiac Index
The two groups did not differ significantly in LAD (23.58 ± 4.69 mm vs. 23.74 ± 3.65 mm, p = 0.744), RAD (25.95 ± 3.89 mm vs. 26.35 ± 3.73 mm, p = 0.389), or RVOT (19.15 ± 3.49 mm vs. 19.77 ± 3.10 mm, p = 0.127) (Fig. 1b, d, e).
Effect of severe scoliosis on cardiac function
In terms of cardiac function in patients with severe scoliosis, both EF and FS were significantly lower compared to the Non-severe scoliosis group (EF: 66.67 ± 4.33% vs. 68.35 ± 4.42%, p = 0.002; FS: 36.58 ± 3.50% vs. 38.02 ± 3.57%, p = 0.001)(Fig. 1h, i). However, no significant difference in CI was observed between groups (2.90 ± 0.46 L/min/m² vs. 2.94 ± 0.48 L/min/m², p = 0.431) (Fig. 1j).
Cardiac differences across cobb angle intervals
Cardiac structure and function are greatly affected by severe scoliosis deformity. Patients with severe scoliosis having a 120°>Cobb angle ≥ 90° were categorized into Group S1 (n = 62) and those with a Cobb angle ≥ 120° into Group S2 (n = 35) to investigate cardiac impact.
The average Cobb angle of the main thoracic curve in Group S1 was 101.75 ± 8.86°, while in Group S2, it was 136.17 ± 12.01°. Among the cardiac structure indicators, the LVDd in Group S2 (33.95 ± 4.97 mm) was significantly lower than that in Group S1 (36.07 ± 4.82 mm)(p < 0.05). However, no significant differences were found between the two groups in other cardiac structure indicators, including LAD, RVDd, RAD, RVOT, IVST, and LVPWT (p > 0.05). In terms of cardiac function indicators, the CI in Group S2 (2.72 ± 0.45 L/min/m²) was significantly lower than that in Group S1 (3.00 ± 0.43 L/min/m²)(p < 0.05). No significant differences were observed in EF and FS between groups(p > 0.05)(Table 2).
Table 2. Comparison of cardiac structure and function indices between group S1 and group S2
variable | Group S1(n = 62) (90°—120°) | Group S2(n = 35) (Cobb’s angle ≥ 120°) | P-value |
|---|---|---|---|
LVDd(mm) | 36.07 ± 4.82 | 33.95 ± 4.97 | 0.042 |
LAD(mm) | 23.77 ± 4.55 | 23.24 ± 4.98 | 0.591 |
RVDd(mm) | 17.50 ± 3.14 | 17.83 ± 3.36 | 0.624 |
RAD(mm) | 26.40 ± 3.75 | 25.14 ± 4.06 | 0.126 |
RVOT(mm) | 19.16 ± 3.74 | 19.14 ± 3.07 | 0.977 |
IVST(mm) | 6.80 ± 1.53 | 6.72 ± 1.66 | 0.812 |
LVPWT(mm) | 6.69 ± 1.24 | 6.92 ± 1.53 | 0.423 |
EF(%) | 66.82 ± 3.93 | 66.40 ± 5.01 | 0.647 |
FS(%) | 36.66 ± 3.29 | 36.43 ± 3.89 | 0.755 |
CI(L/min.m2) | 3.00 ± 0.43 | 2.72 ± 0.45 | 0.003 |
Statistical significance was set at P < 0.05
LVDd: Left Ventricular Diastolic Diameter; LAD: Left Atrial Diameter; RVDd: Right Ventricular Diastolic Diameter; RAD: Right Atrial Diameter; RVOT: Right Ventricular Outflow Tract; IVST; Interventricular Septal Thickness; LVPWT: Left Ventricular Posterior Wall Thickness; EF, Ejection Fraction; FS, Fractional Shortening; CI, Cardiac Index
Influence of thoracic curve direction on cardiac outcomes
Patients with severe scoliosis deformity were classified into Group S-L (n = 24) for left-convex main thoracic curves and Group S-R (n = 73) for right-convex main thoracic curves. The average Cobb angle of the main thoracic curve was 114.79 ± 19.90° in Group S-L and 113.96 ± 19.39° in Group S-R. No significant differences were observed in cardiac structure or function indicators between groups (p > 0.05) (Table 3).
Table 3. Comparison of cardiac structure and function indices between group S-L and group S-R
variable | Group S-L(n = 24) | Group S-R(n = 73) | P-value |
|---|---|---|---|
LVDd(mm) | 36.69 ± 6.22 | 34.85 ± 4.42 | 0.189 |
LAD(mm) | 23.58 ± 4.80 | 23.58 ± 4.49 | 0.997 |
RVDd(mm) | 17.93 ± 3.27 | 17.51 ± 3.20 | 0.581 |
RAD(mm) | 26.43 ± 4.81 | 25.79 ± 3.56 | 0.550 |
RVOT(mm) | 19.43 ± 4.13 | 19.06 ± 3.28 | 0.663 |
IVST(mm) | 6.52 ± 1.61 | 6.85 ± 1.56 | 0.368 |
LVPWT(mm) | 6.70 ± 1.31 | 6.80 ± 1.37 | 0.368 |
EF(%) | 66.42 ± 5.36 | 66.75 ± 3.98 | 0.743 |
FS(%) | 36.50 ± 4.16 | 36.60 ± 3.29 | 0.902 |
CI(L/min.m2) | 2.95 ± 0.47 | 2.88 ± 0.45 | 0.556 |
Statistical significance was set at P < 0.05
LVDd: Left Ventricular Diastolic Diameter; LAD: Left Atrial Diameter; RVDd: Right Ventricular Diastolic Diameter; RAD: Right Atrial Diameter; RVOT: Right Ventricular Outflow Tract; IVST; Interventricular Septal Thickness; LVPWT: Left Ventricular Posterior Wall Thickness; EF, Ejection Fraction; FS, Fractional Shortening; CI, Cardiac Index
Impact of age on cardiac structure and function
Patients with severe scoliosis were categorized into two age groups: Group P (≤ 18 years, n = 77) and Group A (> 18 years, n = 20). The average age was 13.17 ± 3.18 years in Group P and 22.29 ± 2.36 years in Group A (p < 0.05). The Cobb angle of the main thoracic curve averaged 111.94 ± 18.35° in Group P and 122.75 ± 21.48° in Group A (p < 0.05). Group P had significantly lower cardiac structure indicators than Group A, with LVDd 34.70 ± 5.28 mm vs. 37.60 ± 2.35 mm (p = 0.019), LAD 22.89 ± 4.18 mm vs. 26.25 ± 5.65 mm (p = 0.004), RVDd 17.18 ± 3.23 mm vs. 19.30 ± 2.54 mm (p = 0.008), RAD 25.58 ± 4.04 mm vs. 26.35 ± 2.93 mm (p = 0.042), RVOT 18.75 ± 3.35 mm vs. 20.70 ± 3.70 mm (p = 0.026), IVST was 6.51 ± 1.54 mm vs. 7.75 ± 1.29 mm (p = 0.001), and LVPWT was 6.55 ± 1.30 mm vs. 7.64 ± 1.18 mm (p = 0.001)(Fig. 2a-g). No significant differences in cardiac function were found between groups, with EF 66.71 ± 4.35% vs. 66.50 ± 4.40% (p = 0.845), FS 36.56 ± 3.54% vs. 36.65 ± 3.44% (p = 0.918), and CI 2.87 ± 0.46 L/min/m² vs. 2.99 ± 0.44 L/min/m² (p = 0.282) (Fig. 2h, i,j).
[See PDF for image]
Fig. 2
Comparison of Cardiac Structural and Function Indices between Group P and Group A
*P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; ns, Not significant. Group P: Pediatric-group; Group A: Adult-group; LVDd: Left Ventricular Diastolic Diameter; LAD: Left Atrial Diameter; RVDd: Right Ventricular Diastolic Diameter; RAD: Right Atrial Diameter; RVOT: Right Ventricular Outflow Tract; IVST: Interventricular Septal Thickness; LVPWT: Left Ventricular Posterior Wall Thickness; EF: Ejection Fraction; FS: Fractional Shortening; CI: Cardiac Index
Gender-related variations in cardiac structure and function
The impact of gender on cardiac parameters in patients was investigated in two groups: male (Group M, n = 32) and female (Group F, n = 65). The average age was 17.06 ± 6.01 years in Group M and 15.32 ± 7.29 years in Group F; the average Cobb angle of the main thoracic curve was 115.01 ± 23.22° in Group M and 113.75 ± 17.44° in Group F, with no significant differences. Group M had considerably higher RVDd, RAD, and RVOT compared to Group F (Fig. 3c, d,e). No significant differences were found in LVDd (36.08 ± 5.43 mm vs. 34.92 ± 4.70 mm, p = 0.279), LAD (24.62 ± 4.25 mm vs. 23.07 ± 4.85 mm, p = 0.126), IVST (7.12 ± 1.65 mm vs. 6.59 ± 1.51 mm, p = 0.119), and LVPWT (7.02 ± 1.49 mm vs. 6.66 ± 1.26 mm, p = 0.215)(Fig. 3a, b,f, g) as well as cardiac function with EF (66.03 ± 5.19% vs. 66.98 ± 3.85%, p = 0.311), FS (36.28 ± 4.14% vs. 36.72 ± 3.17%, p = 0.562), and CI (2.97 ± 0.46 L/min/m² vs. 2.86 ± 0.45 L/min/m², p = 0.268) between groups(Fig. 3h, i,j).
[See PDF for image]
Fig. 3
Comparison of Cardiac Structural and Function Indices between Group F and Group M
*P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; ns, Not significant
Group F: Female-group; Group M: Male-group; LVDd: Left Ventricular Diastolic Diameter; LAD: Left Atrial Diameter; RVDd: Right Ventricular Diastolic Diameter; RAD: Right Atrial Diameter; RVOT: Right Ventricular Outflow Tract; IVST: Interventricular Septal Thickness; LVPWT: Left Ventricular Posterior Wall Thickness; EF: Ejection Fraction; FS: Fractional Shortening; CI: Cardiac Index
Correlation between cobb angle and cardiac parameters in severe scoliosis
Pearson correlation analysis was conducted to evaluate the relationship between the coronal main thoracic Cobb angle and cardiac structural and functional parameters in the severe scoliosis group. As shown in Table 4, the Cobb angle was significantly negatively correlated with LVDd (r= − 0.234, p = 0.021; Fig. 4a) and cardiac index (CI) (r= − 0.374, p < 0.001; Fig. 4b), indicating that increasing curvature severity is associated with reduced left ventricular dimensions and cardiac output.
Table 4. Correlation analysis of cobb’s angle with cardiac structure and function indices in group S
Cobb’s angle | ||||
|---|---|---|---|---|
r | (95% CI) | P-value* | R2 | |
LVDd | -0.234 | (-0.414, -0.036) | 0.021 | 0.055 |
LAD | -0.089 | (-0.283, 0.112) | 0.386 | 0.008 |
RVDd | 0.012 | (-0.188,0.211) | 0.906 | 0.000 |
RAD | -0.187 | (-0.373, 0.013) | 0.066 | 0.035 |
RVOT | -0.008 | (-0.207, 0.192) | 0.936 | 0.000 |
IVST | -0.071 | (-0.266,0.131) | 0.491 | 0.005 |
LVPWT | 0.056 | (-0.145, 0.253) | 0.588 | 0.003 |
EF | -0.081 | (-0.276, 0.121) | 0.432 | 0.006 |
FS | -0.074 | (-0.270, 0.127) | 0.471 | 0.005 |
CI | -0.374 | (-0.534, -0.189) | < 0.001 | 0.140 |
*Correlation Analysis, Statistical significance was set at P < 0.05; CI: confidence interval
LVDd, Left Ventricular Diastolic Diameter; LAD, Left Atrial Diameter; RVDd, Right Ventricular Diastolic Diameter; RAD, Right Atrial Diameter; RVOT, Right Ventricular Outflow Tract; IVST, Interventricular Septal Thickness; LVPWT, Left Ventricular Posterior Wall Thickness; EF, Ejection Fraction; FS, Fractional Shortening; CI, Cardiac Index
[See PDF for image]
Fig. 4
Scatter charts show the relationship between the Cobb angle and left ventricular diastolic diameter (LVDd) and cardiac index (CI)
Discussion
Severe scoliosis, characterized by pronounced spinal curvature, often leads to thoracic deformity and compromised cardiopulmonary function. These anatomical and physiological changes increase the risk of perioperative complications and pose significant challenges for surgical correction, particularly in maintaining respiratory and circulatory stability.
At our institution, preoperative echocardiography is a routine and essential evaluation for all patients undergoing scoliosis correction surgery. As a non-invasive and reliable method for assessing cardiac structure and function [15, 22, 23, 24–25], echocardiography plays a critical role in identifying cardiovascular abnormalities. This study emphasizes the necessity of preoperative cardiac examination in severe scoliosis patients for perioperative planning, surgical safety, and reduced postoperative complications.
Impact of main curve angles on cardiac structure and function between severe and non-severe scoliosis
With the advancement of early scoliosis screening [26] and treatments, the prevalence of severe scoliosis has decreased. This study began data collection in 2018 and included 97 patients with a primary Cobb angle exceeding 90°. Compared to patients with non-severe scoliosis, those with severe deformities demonstrated significant structural abnormalities (p < 0.05).
Echocardiography’s LVDd reflects the left ventricle’s internal diameter at the diastole’s end, indicating preload and diastolic capacity. Our findings revealed a significant reduction in LVDd in severe scoliosis cases, suggesting that greater thoracic curvature directly impacts left heart dimensions. LVDd reductions may indicate inadequate ventricular filling or structural compression, which affects cardiac output and functional reserve.
Previous studies have explored the relationship between scoliosis severity and LVDd. Liang et al. [18] categorized 176 congenital scoliosis patients by Cobb angle (40°–80° vs. >80°). Their results showed considerably decreased LVDd in the > 80° group, consistent with our findings. In contrast, Li et al. [19] found no significant change in LVDd between healthy controls and 23 patients with an average Cobb angle of 61°. Scoliosis severity, sample size, and control group design may cause these disparities, emphasizing the need for methodological consistency in cardiac effect assessments.
In our study, a significant reduction in LVDd was observed in those with severe scoliosis. Several mechanisms may explain this: (1) Mechanical compression from thoracic deformity may reduce left ventricular chamber volume; (2) Decreased thoracic compliance can impair venous return due to limited chest wall mobility and intrathoracic negative pressure; and (3) Pulmonary hypertension from restricted lung function may reduce preload and promote ventricular remodeling.
Our study found that severe scoliosis patients had significantly lower IVST and LVPWT than Non-severe scoliosis, suggesting myocardial remodeling due to progressive spinal deformity. Severe thoracic deformities can compromise pulmonary function and cause chronic hypoxia, which can cause myocardial atrophy. Malnutrition and poor health, typical in severe scoliosis patients, may further limit myocardial growth and thin ventricular walls.
These findings differ from those reported by Liang et al. [18], who observed no significant differences in IVST and LVPWT across patient groups. This variation may be due to the study population and scoliosis severity classifications. Liang et al. focused on congenital scoliosis, which typically has multisystem malformations [27, 28–29], while our study eliminated such individuals to create a more homogeneous idiopathic or non-congenital cohort. Moreover, we adopted the ‘Kunming Consensus’ by Xie et al. [4], which defined severe scoliosis as a Cobb angle ≥ 90°, comprising patients with more severe deformities than studies using lower thresholds.
The study revealed that the primary thoracic curve angle in severe scoliosis significantly impacts the structure of the right heart, as evidenced by a marked decrease in the RVDd. This finding is likely attributable to severe thoracic deformity, which alters the heart’s position and morphology [2]. The right ventricle, located anteriorly, is particularly susceptible to mechanical compression from the thoracic deformity, leading to reduced RVDd.
Significant reductions in LVDd, RVDd, IVST, and LVPWT may impact cardiac geometry and function. For instance, a decreased LVDd may impact ventricular filling during diastole, limiting cardiac output. Patients with severe scoliosis may have more perioperative cardiac complications due to cumulative structural and functional changes. Thus, these seemingly modest but statistically significant cardiac parameter changes affect preoperative assessment and surgical management.
In severe scoliosis patients, EF and FS decreased significantly, indicating a decline in cardiac systolic function. These parameters are clinically significant for assessing cardiac performance and left ventricular function [2]. Li et al. [19] examined left ventricular myocardium in scoliosis patients using cardiac ultrasonography and found that larger thoracic curve angles were associated with worsening systolic function. Consistently, our study found a greater decline in systolic function in patients with more severe deformities, demonstrating the profound impact of severe scoliosis on left ventricular performance.
Despite the slight difference in EF between the severe scoliosis and Non-severe scoliosis groups (66.67% vs. 68.35%), this reduction is clinically significant. EF decreases may suggest early myocardial dysfunction for cardiac function. A slight decrease in EF can increase the risk of heart failure over time, especially when accompanied by surgical physiological stress. FS is a sensitive indicator of cardiac contractility, hence a reduction may indicate a less efficient heart pump. FS decreased from 38.02% in the Non-severe scoliosis group to 36.58% in the severe scoliosis group, also suggesting left ventricular systolic dysfunction. These findings emphasize the importance of preoperative cardiac function evaluation in severe scoliosis patients.
Effects of cobb angle intervals on cardiac structure and function in severe scoliosis
This study investigated the effects of severe and non-severe scoliosis on cardiac structure and function, revealing that severe scoliosis exerts a substantial impact on both. To further explore the cardiac effects within severe scoliosis, patients were stratified into two groups based on the Cobb angle of the major thoracic curvature: Group S1 (120°>Cobb angle ≥ 90°) and Group S2 (Cobb angle ≥ 120°).
The LVDd in Group S2 was significantly lower than in Group S1, indicating greater left ventricular compression and remodeling with increasing curvature severity. Functionally, the CI was significantly lower than Group S1, indicating a decline in cardiac performance in patients with more severe deformities.
The findings demonstrate that severe scoliosis significantly impairs cardiac structure and function, with deformity severity directly affecting cardiac dysfunction. Greater Cobb angle intervals significantly damage the left ventricle. These findings emphasize the need to categorize patients by curvature severity for better clinical assessment and treatment.
Comparison of cardiac function between severe and non-severe scoliosis
Compared to non-severe scoliosis groups, severe spinal deformity negatively impacts EF and FS. According to further subgroup analysis, the CI is severely degraded when the Cobb angle exceeds 120° in severe scoliosis. This shows that cardiac impairment develops with curvature severity. Although EF, FS, and CI are influenced differently depending on the evaluation method, the three metrics are essential to measuring cardiac function, and their interaction provides a comprehensive understanding of scoliosis’ cardiovascular effects.
Impact of major thoracic curvature direction on cardiac function in severe scoliosis
The analysis was performed to investigate how the major thoracic curvature direction affects cardiac structure and function in severe scoliosis. The analysis revealed no significant differences in cardiac structure or function between patients with left or right convex curves in the severe scoliosis group.
These findings differ from those of Liang et al. [18], who reported that right-sided thoracic curves in congenital scoliosis had a more pronounced effect on cardiac structure, though without significant impact on cardiac function. Notably, most patients in their study had Cobb angles below 90°, which may partly account for the discrepancy. We speculate that at lower curvature angles, the heart’s spatial displacement varies depending on the curve direction [30, 31]. However, with increasing deformity severity, thoracic distortion intensifies and eventually stabilizes, prompting the heart to adapt to its altered position and shape. This adaptation may reduce the directional influence of the curve on cardiac structure and function in severe cases.
Impact of age on cardiac function in severe scoliosis
This study investigated age-related cardiac structure and function in severe scoliosis patients. Scoliosis severity was substantially higher in adults (> 18 years) compared to adolescents (≤ 18 years), with Cobb angles of 122.75°±21.48° vs. 111.94°±18.35°(p < 0.05). Scoliosis deteriorates with age, probably due to continuous skeletal development and inadequate early therapy during adolescence. Although skeletal growth stabilizes in adulthood, excessive mechanical stress may result in spine deterioration [32].
Significant cardiac structural differences were identified across groups. Group A had higher LVDd, LAD, RVDd, RAD, RVOT, IVST, and LVPWT (p < 0.05). Long-term scoliosis progression and compensatory cardiac remodeling may cause these discrepancies. Spinal abnormalities may limit cardiac development in adolescence, resulting in smaller cardiac chambers. Persistent hemodynamic stress in adulthood may cause compensatory chamber dilatation and myocardial hypertrophy to adjust to circulatory demands [33].
Although structural changes were observed, EF, FS, and CI did not differ between groups (p > 0.05). Cardiac function may be maintained by compensatory mechanisms of myocardial adaptability in severe scoliosis [34]. However, because of the limited adult cohort (n = 20) and the likelihood of late-onset cardiac dysfunction caused by persistent scoliosis-related stress, more extensive, longitudinal investigations are needed to determine long-term cardiac function effects. This study shows that severe scoliosis patients’ cardiac structure changes with age, however, cardiac function remains preserved in the early stages. These findings highlight the cardiovascular risks of scoliosis and the need for early intervention, personalized care, and long-term follow-up.
Gender differences in cardiac parameters in patients with severe scoliosis
Gender-related differences in cardiac parameters were investigated in severe scoliosis patients. Male and female subgroups had similar ages and main thoracic Cobb angles, ensuring comparability.
In terms of cardiac structure, males exhibited significantly larger RVDd, RAD, and RVOT than females. This finding aligns with the physiological characteristic that male hearts are generally larger than female [35]. In severe scoliosis, the relatively broader and more rigid male thorax may exert greater mechanical compression on the right hearts by scoliosis-induced thoracic deformities. Additionally, androgens such as testosterone promote cardiomyocyte growth and remodeling, further contributing to right heart enlargement [36]. Conversely, no significant differences were observed in left heart parameters between genders, likely due to the left heart’s posterior position, which reduces its direct exposure to scoliosis-induced thoracic deformation.
In cardiac function, male and female groups had comparable EF, FS, and CI. This supports the physiological observation that cardiac function is identical between genders. Due to compensating mechanisms such as myocardial hypertrophy and heart rate modulation, the right heart can maintain its pumping function despite gender-related anatomical variations.
Our study shows that gender is critical to heart structural changes in severe scoliosis, particularly right heart remodeling. Clinicians should consider gender differences during the assessment to personalize treatment and reduce potential cardiac complications.
Correlation between curvature angle and cardiac parameters in severe scoliosis patients
A negative association was found between severe scoliosis patients’ main thoracic curvature angle and heart anatomy and function. The Cobb angle was negatively correlated with LVDd (r=-0.234, p = 0.021) and CI (r=-0.374, p < 0.001). These findings highlight the detrimental effects of increasing spinal curvature severity on cardiac morphology and performance.
Li et al. [19] found a negative connection between major thoracic curvature angle and cardiac performance in 23 congenital scoliosis patients without heart failure by echocardiography. Their study did not stratify patients by Cobb angle, making it difficult to analyze how curvature severity affects cardiac outcomes. We found that severe scoliosis affects heart structure and function, especially in patients with extreme curvature angles.
Cardiac parameters, clinical significance, and perioperative risk considerations
Despite no cardiac symptoms in this study cohort, severe scoliosis patients’ decreased LVDd and CI may indicate cardiovascular dysfunction. Normal adult LVDd is 42–56 mm, with values below 40 mm indicating cardiac pathology [37, 38–39]. Similarly, a CI indicates insufficient cardiac output [38, 40]. In adolescents, normal LVDd and CI ranges are 37–54 mm and 2.5–4.2 L/min/m² [41, 42, 43–44], respectively. LVDd values below 30–32 mm or CI values under 2.2–2.0 L/min/m² often indicate significant cardiac impairment, correlating with symptoms such as dyspnea, fatigue, and palpitations [45, 46].
Patients with severe scoliosis exhibited a mean LVDd of 35.30 ± 4.96 mm and a mean CI of 2.90 ± 0.46 L/min/m² in this study. Further reductions were noted in Group S2, with LVDd averaging 33.95 ± 4.97 mm and CI 2.72 ± 0.45 L/min/m². These results approach perioperative cardiac risk criteria albeit not being prospectively inspected for clinical symptoms. Studies suggest that LVDd < 35 mm in adults may indicate left ventricular hypoplasia or restrictive physiology [37, 47], while in adolescents, it may indicate ventricular remodeling from prolonged mechanical compression [48]. A CI < 2.2 L/min/m² is a sign of inadequate cardiac output, associated with poor tissue perfusion and higher perioperative mortality [40, 49]. Among Group S2 patients, 11.4% (n = 4/35) had CI < 2.2 L/min/m², and 37.1% (n = 13/35) had LVDd values < 35 mm, emphasizing the importance of perioperative attention.
Hence, we recommend a multidisciplinary examination, including cardiology and cardiac anesthesia, for patients with severe scoliosis who match the following criteria: LVDd < 35 mm, CI < 2.5 L/min/m², or EF < 55%, based on our study and previous studies. Without preoperative cardiac optimization or staged-spinal correction strategies, patients with CI < 2.2 L/min/m² or LVDd < 35 mm may face increased perioperative risks. Those with clinical signs like impaired exercise tolerance or dyspnea should delay elective scoliosis surgery until a cardiac examination is done. To ensure appropriate hemodynamic control, patients with LVDd < 30 mm or CI < 2.0 L/min/m² need enhanced intraoperative cardiac anesthesia monitoring in our clinical practice.
These findings underline the importance of early diagnosis of cardiac compromise as well as personalized perioperative evaluation and management to reduce cardiac risks from scoliosis surgery.
Limitations
This study analyzed 97 patients with severe scoliosis, offering a representative but modest sample. Larger cohorts are needed to improve statistical power and enable detailed subgroup analyses.
Cardiac assessment relied on resting echocardiography, which does not capture functional changes under stress. Future studies incorporating dynamic evaluations may provide a more complete picture of cardiac involvement.
Pulmonary function, a key factor in cardiopulmonary interaction, was not assessed. Integrating pulmonary evaluation in future research could enhance preoperative risk assessment and management.
Conclusion
Severe scoliosis significantly affects cardiac structure and function at rest, with notable involvement of the left heart. Parameters such as LVDd and CI are critical for preoperative evaluation and should guide clinical decision-making.
Cardiac alterations are more closely associated with the severity of spinal deformity than with curve direction. While age and gender influence certain structural indices, their impact on cardiac function is limited. These findings underscore the importance of individualized assessment based on deformity severity rather than curve orientation.
Acknowledgements
We thank all colleagues from Department of Orthopedics, the Second Affiliated Hospital of Kunming Medical University who provided insightful discussions and constructive suggestions throughout the study.
Author contributions
Jie Xiao and Tao Li (co-first authors): Contributed equally to this work. Responsible for study concept, data collection, and initial drafting of the manuscript.Yingsong Wang and Zhi Zhao: Contributed to data analysis, interpretation of results, and manuscript revision.Jingming Xie (corresponding author): Designed the study, supervised all stages of the project, and finalized the manuscript.Jin Zhou (co-corresponding author): Coordinated the study design and critically reviewed the manuscript for important intellectual content.
Funding
This study was funded by the National Natural Science Foundation of China (No. 82260447) and the Key Research and Development Program of Yunnan Provincial Science and Technology Department (No. 202403AC100008).
The funding body had no role in study design, data collection, data analysis, manuscript preparation, or the decision to publish.
Data availability
The datasets used and/or analyzed during the current study are mostly included in the published article and also available from the corresponding author on reasonable request.
Declarations
Ethics approval and consent to participate
This study complied with the Declaration of Helsinki and was approved by the Human Research Ethics Committee of the Second Affiliated Hospital of Kunming Medical University. Informed consent was waived owing to the retrospective nature of the study and approved by the Human Research Ethics Committee of the Second Affiliated Hospital of Kunming Medical University.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Abbreviations
Idiopathic scoliosis
Left ventricular diastolic diameter
Left atrial diameter
Right ventricular diastolic diameter
Right atrial diameter
Right ventricular outflow tract
Interventricular septal thickness
Left ventricular posterior wall thickness
Ejection fraction
Fractional shortening
Cardiac index
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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