Differential changes in longitudinal and area-based right ventricular function after aortic surgery: an exploratory echocardiographic study

Abstract

Background

Reductions in right ventricular (RV) longitudinal parameters, particularly tricuspid annular plane systolic excursion (TAPSE), are frequently observed after cardiac surgery. However, postoperative changes in longitudinal RV motion may not occur in parallel with other conventional echocardiographic indices of RV function. This study aimed to evaluate early postoperative changes in longitudinal and area-based RV functional parameters after elective aortic surgery.

Methods

This single-center retrospective study included 102 patients undergoing elective aortic surgery. Preoperative and early postoperative transthoracic echocardiography was used to assess RV function, including TAPSE, fractional area change (FAC), and tissue Doppler-derived S′ velocity. Absolute and relative percentage changes in RV echocardiographic parameters were calculated. To summarize the relative behavior of longitudinal and area-based RV indices, the Right Ventricular Functional Dissociation Index (RV-FDI) was calculated as the ratio of postoperative-to-preoperative FAC to postoperative-to-preoperative TAPSE. RV-FDI was considered an exploratory descriptive ratio and not a validated diagnostic or prognostic marker.

Results

TAPSE decreased significantly from 22.0 ± 4.9 mm to 18.3 ± 5.9 mm (p < 0.001). FAC also decreased significantly from 41.9 ± 6.9% to 36.9 ± 7.3% (p < 0.001), and S′ velocity declined from 14.9 ± 3.0 cm/s to 12.6 ± 3.5 cm/s (p < 0.001). The relative reduction in TAPSE was significantly greater than that in FAC (− 17.8 ± 12.3% vs. −12.2 ± 6.3%, p = 0.00027), indicating non-uniform postoperative changes among conventional RV echocardiographic parameters. Mean RV-FDI was 1.09 ± 0.16. No significant differences in postoperative RV parameters or RV-FDI were observed between sternotomy and minimally invasive approaches. RV-FDI was not significantly associated with postoperative lactate levels, inotropic support, mechanical ventilation duration, ICU stay, or hospital stay.

Conclusion

Elective aortic surgery was associated with a greater early postoperative reduction in longitudinal RV indices than in FAC, suggesting that conventional echocardiographic parameters of RV function may not change uniformly after surgery. RV-FDI may provide a simple exploratory description of this relative pattern, but it should not be interpreted as a validated measure of RV mechanics, clinical RV dysfunction, or prognosis. Further studies incorporating RV strain, three-dimensional echocardiography, RV–pulmonary arterial coupling, and longitudinal clinical outcomes are required to clarify the physiological and prognostic significance of these findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12893-026-03941-w.

Introduction

Right ventricular (RV) dysfunction is a well-documented phenomenon after cardiac surgery and has been consistently associated with postoperative morbidity and mortality [1–3]. RV dysfunction has been described after coronary artery bypass grafting, valve surgery, and transcatheter procedures. Among conventional echocardiographic parameters, tricuspid annular plane systolic excursion (TAPSE) is commonly used to assess RV systolic function. Longitudinal shortening represents an important component of RV contraction, and TAPSE remains one of the most widely used parameters for evaluating RV systolic function in both clinical practice and research settings [4].

Paradoxically, several studies have demonstrated a significant reduction in TAPSE after cardiac surgery, even among clinically stable patients without overt postoperative RV failure or adverse early outcomes [5–7]. These observations raise important questions regarding the interpretation of postoperative reductions in longitudinal RV parameters. In particular, a decrease in TAPSE after surgery may not necessarily indicate a proportional deterioration across all components of RV systolic performance.

The mechanisms underlying postoperative changes in RV echocardiographic parameters are multifactorial. Myocardial ischemia, cardiopulmonary bypass, pulmonary hypertension, altered loading conditions, and perioperative myocardial stunning may all contribute to changes in RV function after cardiac surgery [8, 9]. In addition, surgical factors, particularly pericardial opening and changes in ventricular constraint or interaction, have been suggested to influence postoperative RV motion [7, 10]. Previous studies have shown that reductions in RV longitudinal motion may occur early after pericardiotomy, supporting the possibility that geometric and translational changes contribute to postoperative alterations in conventional RV indices.

RV contraction is not determined by longitudinal shortening alone. Rather, it reflects a complex interaction among longitudinal shortening, radial inward motion, free-wall contraction, and interventricular septal contribution [4, 11]. Therefore, postoperative changes in one echocardiographic parameter may not fully represent global RV systolic behavior. In this context, reductions in longitudinal parameters such as TAPSE or tissue Doppler-derived S′ velocity may occur in parallel with smaller changes in area-based indices such as fractional area change (FAC).

Despite extensive research on RV function after cardiac surgery, an important interpretative limitation remains. Most postoperative studies emphasize longitudinal parameters, particularly TAPSE. However, reductions in TAPSE may reflect geometric changes, altered loading conditions, annular translational changes, or postoperative alterations in RV mechanics rather than isolated longitudinal myocardial impairment [5, 7, 12]. Current echocardiographic recommendations emphasize the importance of multiparametric RV assessment, incorporating longitudinal, area-based, and deformation-based indices when available [10]. Among conventional parameters, FAC provides an area-based assessment of RV systolic function and may capture broader components of RV contraction than TAPSE alone.

The present study was designed to evaluate early postoperative changes in conventional RV echocardiographic parameters after elective aortic surgery. The primary focus was the direct comparison of relative changes in longitudinal RV indices, including TAPSE and S′ velocity, with changes in FAC. To summarize the relative behavior of longitudinal and area-based parameters, we also calculated the Right Ventricular Functional Dissociation Index (RV-FDI), defined as the ratio of postoperative-to-preoperative FAC to postoperative-to-preoperative TAPSE. Importantly, RV-FDI was considered an exploratory descriptive ratio and not a validated diagnostic, mechanistic, or prognostic marker.

We hypothesized that early postoperative changes in RV echocardiographic parameters would not be uniform, with longitudinal indices showing greater relative reduction than FAC. Accordingly, the primary objective of this study was to compare the magnitude of postoperative changes in TAPSE, FAC, and S′ after elective aortic surgery. Secondary exploratory objectives were to describe the distribution of RV-FDI, compare postoperative RV echocardiographic changes between sternotomy and minimally invasive approaches, and assess whether this echocardiographic pattern was associated with early postoperative clinical recovery parameters.

Materials and methods

Study design and patient population

This single-center retrospective observational study included consecutive adult patients who underwent elective aortic surgery between January 2021 and December 2023. Patients undergoing either full median sternotomy or minimally invasive right anterior thoracotomy were evaluated.

Patients were eligible for inclusion if they underwent elective aortic valve, ascending aortic, or combined aortic procedures and had complete preoperative and early postoperative transthoracic echocardiographic data available for right ventricular (RV) functional assessment. Patients were excluded if they had prior cardiac surgery, congenital heart disease, inadequate echocardiographic image quality, or severe pre-existing RV dysfunction. Severe pre-existing RV dysfunction was defined as preoperative tricuspid annular plane systolic excursion (TAPSE) < 17 mm or fractional area change (FAC) < 35%, in accordance with accepted echocardiographic thresholds.

This study was approved by the Institutional Ethics Committee of Ankara Bilkent City Hospital. All procedures were performed in accordance with the ethical standards of the institutional research committee and with the 1964 Declaration of Helsinki and its later amendments. Owing to the retrospective observational design of the study, the requirement for informed consent was waived by the Institutional Ethics Committee.

Surgical technique

All procedures were performed under standard cardiopulmonary bypass using mild to moderate hypothermia and institutional myocardial protection protocols. Operative data included cardiopulmonary bypass (CPB) duration, aortic cross-clamp time, transfusion requirements, postoperative mechanical ventilation duration, inotropic support, intensive care unit (ICU) length of stay, hospital length of stay, postoperative complications, and early mortality.

The pericardial opening technique differed according to surgical approach. In patients undergoing full sternotomy, an anterior pericardiotomy was performed, resulting in extensive anterior pericardial opening. In patients undergoing minimally invasive aortic surgery, the pericardium was opened locally over the ascending aorta through a limited incision.

The comparison between sternotomy and minimally invasive approaches was considered exploratory. Because the groups were not randomized and differed in selected baseline characteristics, this comparison was not intended to establish equivalence or causality regarding the effect of surgical access or pericardial opening on postoperative RV function.

Echocardiographic assessment

Transthoracic echocardiography was performed preoperatively and before hospital discharge in the early postoperative period, generally within postoperative days 5–7, using standardized institutional protocols. RV function was assessed using a multiparametric conventional echocardiographic approach including TAPSE, RV FAC, and tissue Doppler-derived tricuspid annular systolic velocity (S′).

TAPSE was used as an index of longitudinal RV systolic motion. S′ velocity was used as an additional longitudinal tissue Doppler parameter. FAC was used as an area-based conventional echocardiographic parameter reflecting global RV systolic area change. All measurements were performed by the same experienced echocardiography team according to institutional practice.

Absolute changes in RV echocardiographic parameters were calculated as follows:

Relative percentage changes were calculated as follows:

The relative percentage changes in TAPSE, FAC, and S′ were used to evaluate whether early postoperative changes in conventional RV echocardiographic parameters occurred uniformly or differed between longitudinal and area-based indices.

Definition of right ventricular functional dissociation index

To summarize the relative behavior of longitudinal and area-based RV echocardiographic parameters, the Right Ventricular Functional Dissociation Index (RV-FDI) was calculated as an exploratory descriptive ratio.

RV-FDI was defined as:

RV-FDI = (postoperative FAC / preoperative FAC) ÷ (postoperative TAPSE / preoperative TAPSE).

An RV-FDI value greater than 1 indicates that the relative postoperative reduction in TAPSE is greater than the relative reduction in FAC.

In the present study, RV-FDI was not considered a validated diagnostic, mechanistic, or prognostic marker. It was not intended to replace direct analysis of TAPSE, FAC, or their relative percentage changes. Instead, RV-FDI was used only as an exploratory descriptive ratio to summarize the relationship between two routinely available conventional echocardiographic parameters. Because RV-FDI is mathematically derived from TAPSE and FAC, all analyses involving RV-FDI were interpreted cautiously.

Clinical outcomes

Postoperative clinical outcomes included mechanical ventilation duration, ICU stay, hospital stay, transient inotropic support, postoperative lactate levels, early mortality, and clinically overt RV failure.

Transient inotropic support was recorded according to the requirement for postoperative pharmacological hemodynamic support. Postoperative lactate levels were assessed at 1, 6, 12, and 24 h after surgery.

Clinically overt RV failure was defined as persistent postoperative hemodynamic instability requiring prolonged inotropic support or mechanical circulatory support in the presence of suspected or documented RV dysfunction. Requirement for extracorporeal membrane oxygenation was also recorded.

Statistical analysis

Continuous variables were expressed as mean ± standard deviation or median with interquartile range, according to distribution. Categorical variables were presented as number and percentage. Normality was assessed using the Shapiro–Wilk test.

Preoperative and postoperative echocardiographic parameters were compared using paired Student’s t-test for normally distributed variables and the Wilcoxon signed-rank test for non-normally distributed variables. Relative percentage changes in TAPSE, FAC, and S′ were calculated. The relative decline in TAPSE was directly compared with the relative decline in FAC using paired analysis to determine whether longitudinal RV motion decreased disproportionately compared with area-based RV functional change.

Because RV-FDI is mathematically derived from TAPSE and FAC, analyses involving RV-FDI were considered exploratory and descriptive. ROC analysis using TAPSE-derived endpoints was not performed because of mathematical coupling. RV-FDI was therefore analyzed as a continuous exploratory ratio rather than as an independently validated discriminatory marker.

Exploratory linear regression was performed to examine clinical, operative, and echocardiographic variables associated with RV-FDI. Variables entered into the model included age, hypertension, CPB duration, aortic cross-clamp duration, surgical approach, preoperative TAPSE, and preoperative FAC. Multicollinearity was assessed using variance inflation factors, and residual plots were visually inspected to assess assumptions of linearity and homoscedasticity.

Importantly, because preoperative TAPSE and FAC are mathematically embedded in the RV-FDI formula, associations between these variables and RV-FDI were interpreted as expected mathematical relationships rather than independent biological predictors. Given the modest sample size, the exploratory nature of the derived outcome, and the potential risk of model instability and overfitting, multivariable findings were considered hypothesis-generating and were not used to support causal, prognostic, or mechanistic conclusions.

Additional exploratory analyses evaluated the association between RV-FDI and postoperative clinical recovery parameters, including transient inotropic support, postoperative lactate levels, mechanical ventilation duration, ICU stay, and hospital stay. Logistic regression was used for binary outcomes, and correlation analyses were used for continuous postoperative outcomes. These analyses were interpreted cautiously because of the low number of adverse clinical events.

All statistical analyses were performed using IBM SPSS Statistics for Windows, Version 26.0 (IBM Corp., Armonk, NY, USA). A two-sided p value < 0.05 was considered statistically significant.

Study design and patient population

This single-center retrospective observational study included consecutive adult patients undergoing elective aortic surgery between January 2021 and December 2023. Patients undergoing either full median sternotomy or minimally invasive right anterior thoracotomy were evaluated.

Patients were eligible for inclusion if they underwent elective aortic valve, ascending aortic, or combined aortic procedures and had complete preoperative and early postoperative transthoracic echocardiographic data available for right ventricular functional assessment.

Patients were excluded if they had prior cardiac surgery, congenital heart disease, inadequate echocardiographic image quality, or severe pre-existing right ventricular dysfunction. Severe pre-existing RV dysfunction was defined as preoperative TAPSE < 17 mm or FAC < 35%, in accordance with accepted echocardiographic thresholds.

This study was approved by the Institutional Ethics Committee of Ankara Bilkent City Hospital. All procedures were performed in accordance with the ethical standards of the institutional research committee and with the 1964 Declaration of Helsinki and its later amendments. Due to the retrospective observational design of the study, the requirement for informed consent was waived by the Institutional Ethics Committee of Ankara Bilkent City Hospital.

Surgical technique

All procedures were performed under standard cardiopulmonary bypass under mild to moderate hypothermia with institutional myocardial protection protocols. Operative data included; cardiopulmonary bypass duration (CPB), aortic cross-clamp time (XCL), transfusion requirements (erythrocyte suspension, fresh frozen plasma, platelet suspension), postoperative ventilation duration, need and type of inotropic support, intensive care unit (ICU) length of stay, hospital length of stay, postoperative complications and mortality.

The pericardial opening technique varied between different surgical techniques.

In patients undergoing sternotomy, an anterior T-shaped pericardiotomy was carried out, which resulted in extensive anterior pericardial constraint relief. In patients undergoing minimally invasive surgery, the pericardium was opened locally over the ascending aorta through a limited incision.

The comparison between sternotomy and minimally invasive approaches was used to explore whether different surgical access and pericardial opening patterns were associated with postoperative RV functional changes.

Echocardiographic assessment

Transthoracic echocardiography was performed preoperatively and prior to hospital discharge postoperatively within postoperative days 5–7 using standardized institutional protocols (Philips, Healthcare, Andover, The Netherlands).

RV function was assessed using a multiparametric approach including:

• Tricuspid annular plane systolic excursion (TAPSE)

• Right ventricular fractional area change (FAC)

• Tricuspid annular systolic tissue Doppler velocity (S′)

TAPSE was used as an index of longitudinal RV systolic motion. FAC was used as an area-based echocardiographic parameter reflecting multiple components of RV contraction. S′ velocity was used as an additional longitudinal tissue Doppler parameter.

All measurements were performed by the same experienced echocardiography team.

The following absolute changes were calculated:

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Relative percentage changes were calculated as:

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Definition of Right Ventricular Functional Dissociation Index (RV-FDI)

The Right Ventricular Functional Dissociation Index was calculated to describe the relative magnitude of postoperative longitudinal RV reduction compared with FAC change.

RV-FDI was defined as:

An RV-FDI value greater than 1 indicates that the relative decline in TAPSE is greater than the relative decline in FAC.

In the present study, RV-FDI was not considered a validated diagnostic marker. Instead, it was analyzed as an exploratory descriptive index intended to describe the relationship between longitudinal RV motion and area-based RV functional change after aortic surgery.

Clinical outcomes

Postoperative clinical outcomes included mechanical ventilation duration, intensive care unit stay, hospital stay, transient inotropic support, postoperative lactate levels, early mortality, and clinically overt RV failure.

Transient inotropic support was recorded according to the need for postoperative pharmacological support. Postoperative lactate levels were assessed at 1, 6, 12, and 24 h after surgery.

Clinically overt RV failure was defined as persistent hemodynamic instability requiring prolonged inotropic or mechanical circulatory support in the presence of suspected or documented RV dysfunction. Requirement for extracorporeal membrane oxygenation was also recorded.

Statistical analysis

Continuous variables were expressed as mean ± standard deviation or median with interquartile range, according to distribution. Categorical variables were presented as number and percentage. Normality was assessed using the Shapiro–Wilk test.

Preoperative and postoperative echocardiographic parameters were compared using paired Student’s t-test for normally distributed variables and Wilcoxon signed-rank test for non-normally distributed variables.

Relative percentage changes in TAPSE, FAC, and S′ were calculated. The relative decline in TAPSE was compared with the relative decline in FAC using paired analysis to determine whether longitudinal RV motion decreased disproportionately compared with FAC.

Because RV-FDI mathematically incorporates TAPSE, ROC analysis using a TAPSE-derived endpoint was not retained due to potential mathematical coupling. Therefore, RV-FDI was analyzed as a continuous exploratory descriptive index rather than as an independently validated discriminatory marker.

Multivariable linear regression analysis was performed to identify factors independently associated with RV-FDI. Variables entered into the model included age, hypertension, cardiopulmonary bypass duration, aortic cross-clamp duration, surgical approach, preoperative TAPSE, and preoperative FAC.

Multicollinearity was assessed using variance inflation factors, and no clinically significant multicollinearity was identified. Residual plots were visually inspected to assess assumptions of linearity and homoscedasticity.

Additional exploratory analyses evaluated the association between RV-FDI and postoperative clinical recovery parameters, including transient inotropic support, postoperative lactate levels, mechanical ventilation duration, ICU stay, and hospital stay. Logistic regression was used for binary outcomes, and correlation analyses were used for continuous postoperative outcomes.

All statistical analyses were performed using IBM SPSS Statistics for Windows, Version 26.0 (IBM Corp., Armonk, NY, USA). A two-sided p value < 0.05 was considered statistically significant.

Results

Patient characteristics and operative data

A total of 102 patients undergoing elective aortic surgery were included in the study. Of these, 51 patients underwent full sternotomy and 51 underwent minimally invasive aortic surgery.

Baseline demographic and clinical characteristics are presented in (Table 1). The two surgical groups were generally comparable; however, patients in the sternotomy group were older and had a higher prevalence of hypertension. Operative and early postoperative variables are shown in (Table 2). There were no statistically significant differences between the sternotomy and minimally invasive groups in terms of cardiopulmonary bypass duration, aortic cross-clamp time, transfusion requirements, mechanical ventilation duration, ICU stay, or hospital stay.

Table 1.

Baseline characteristics. Baseline demographic and clinical characteristics of patients undergoing full sternotomy and minimally invasive aortic surgery. Continuous variables are presented as mean ± standard deviation and categorical variables as number (%). Baseline characteristics were largely similar, although age and hypertension differed between groups. Because this was a non-randomized retrospective cohort, differences in age and hypertension between groups should be considered when interpreting comparisons between surgical approaches

Variable	Sternotomy (n = 51)	MIAS (n = 51)	p value
Age (years)	56.9 ± 10.5	49.8 ± 11.7	0.002
Male sex (%)	33 (64.7)	33 (64.7)	1.000
Smoking (%)	4 (7.8)	4 (7.8)	1.000
Hypertension (%)	33 (64.7)	18 (35.3)	0.005
Diabetes mellitus (%)	21 (41.2)	12 (23.5)	0.090
COPD (%)	15 (29.4)	12 (23.5)	0.654
CRF (%)	0	0	—
CVE (%)	0	0	—
CAD (%)	0	0	—

COPD Chronic obstructive pulmonary disease, CRF Chronic renal failure, CVE Cerebrovascular event, CAD Coronary artery disease

Table 2.

Operative & postoperative outcomes. Comparison of intraoperative variables and early postoperative outcomes between sternotomy and minimally invasive surgery groups. Continuous variables are presented as mean ± standard deviation

Variable	Sternotomy (n = 51)	MIAS (n = 51)	p value
Mechanical Ventilation time (h)	20.8 ± 39.0	8.3 ± 4.3	0.206
ICU stay (h)	36.5 ± 38.7	18.9 ± 9.1	0.085
Hospital stay (days)	7.3 ± 3.9	6.0 ± 2.5	0.258
CPB time (min)	121.9 ± 33.4	109.8 ± 32.0	0.291
Cross-clamp time (min)	96.0 ± 24.6	87.2 ± 27.1	0.331
PRBC transfusion (units)	0.6 ± 0.7	0.3 ± 0.7	0.285
FFP transfusion (units)	0.4 ± 0.8	0.1 ± 0.3	0.160
Platelet transfusion (units)	0.1 ± 0.2	0.1 ± 0.2	0.966
Mortality (%)	1 (2.0)	1 (2.0)	1.000
Transient inotrope requirement (%)	15 (29.4)	12 (23.5)	0.72
Acute kidney injury (%)	3 (5.8)	3 (5.8)	1.00
Stroke	0	0	—

ICU Intensive care unit, CPB Cardiopulmonary bypass, PRBC Packed red blood cell, FFP Fresh frozen plasma

Early mortality occurred in two patients (2.0%), one in each surgical group. Both deaths were attributed to multi-organ failure. No patient developed clinically overt right ventricular failure, and no patient required extracorporeal membrane oxygenation.

Changes in conventional right ventricular echocardiographic parameters

Preoperative and postoperative RV echocardiographic parameters are presented in (Table 3). Conventional echocardiographic assessment demonstrated significant early postoperative reductions in all measured RV functional parameters.

Table 3.

Changes in conventional right ventricular echocardiographic parameters. Comparison of preoperative and postoperative right ventricular echocardiographic parameters in the overall cohort demonstrating significant reduction in TAPSE and FAC and RV S′ velocity

Variable	Preoperative	Postoperative	p value
TAPSE (mm)	22.0 ± 4.9	18.3 ± 5.9	< 0.001
FAC (%)	41.9 ± 6.9	36.9 ± 7.3	< 0.001
TV-TDI S′ (cm/s)	14.9 ± 3.0	12.6 ± 3.5	< 0.001

TAPSE Tricuspid annular plane systolic excursion, FAC Fractional area change, TV-TDI S′ Tricuspid annular systolic tissue Doppler velocity

TAPSE decreased significantly from 22.0 ± 4.9 mm preoperatively to 18.3 ± 5.9 mm postoperatively (p < 0.001). FAC also decreased significantly from 41.9 ± 6.9% to 36.9 ± 7.3% (p < 0.001). Similarly, tissue Doppler-derived tricuspid annular S′ velocity declined from 14.9 ± 3.0 cm/s to 12.6 ± 3.5 cm/s (p < 0.001).

Relative changes in longitudinal and area-based RV parameters

Relative percentage changes were analyzed to compare the magnitude of postoperative reduction between longitudinal and area-based RV echocardiographic parameters.

The relative reduction in TAPSE was significantly greater than the relative reduction in FAC (− 17.8 ± 12.3% vs. −12.2 ± 6.3%, p = 0.00027). S′ velocity, another longitudinal RV parameter, showed a relative reduction of − 15.8 ± 10.5%, supporting the observation that longitudinal RV indices were consistently affected in the early postoperative period (Table 4). This finding indicates that early postoperative changes in conventional RV echocardiographic parameters were not uniform, with longitudinal RV motion showing a greater relative reduction than area-based RV functional change (Fig. 1).

Table 4.

Relative changes in right ventricle parameters. The p value refers to the paired comparison between relative percentage changes in TAPSE and FAC

Parameter	Relative change (%)	p value
%ΔTAPSE	−17.8 ± 12.3
%ΔFAC	−12.2 ± 6.3	0.00027
%ΔS′	−15.8 ± 10.5

TAPSE Tricuspid annular plane systolic excursion, FAC Fractional area change, S′ Tricuspid annular systolic tissue Doppler velocity, Δ Change, %Δ Relative percentage change

Fig. 1.

Relative changes in TAPSE and FAC following aortic surgery. Boxplot comparison showing a greater relative postoperative reduction in TAPSE than in FAC. This figure illustrates non-uniform changes among conventional RV echocardiographic parameters and does not imply validation of RV-FDI as an independent physiological marker

Exploratory description using RV-FDI

RV-FDI was calculated as an exploratory descriptive ratio to summarize the relative behavior of FAC and TAPSE. The mean RV-FDI was 1.09 ± 0.16 and was significantly greater than unity (p = 0.00016), consistent with a greater relative reduction in TAPSE than in FAC.

Because RV-FDI is mathematically derived from TAPSE and FAC, this finding was interpreted as a descriptive summary of the observed non-uniform changes in conventional RV echocardiographic parameters rather than as evidence of a validated independent physiological index.

Comparison between surgical approaches

Postoperative RV echocardiographic parameters were compared between sternotomy and minimally invasive aortic surgery groups (Table 5). No statistically significant differences were observed between groups in postoperative TAPSE, FAC, S′ velocity, or RV-FDI.

Table 5.

Exploratory comparison of RV echocardiographic parameters between surgical approaches. Comparison of preoperative and postoperative RV functional parameters between sternotomy and minimally invasive groups. No statistically significant differences were observed between surgical approaches

Variable	Sternotomy (n = 51)	MIAS (n = 51)	p value
TAPSE Preoperative (mm)	22.9 ± 4.3	21.1 ± 5.3	0.283
TAPSE Postoperative (mm)	18.8 ± 5.8	17.9 ± 6.1	0.668
FAC Preoperative (%)	42.1 ± 7.8	41.6 ± 6.1	0.864
FAC Postoperative (%)	35.6 ± 8.1	38.2 ± 6.3	0.548
S′ Preoperative (cm/s)	14.8 ± 3.1	15.0 ± 2.9	0.742
S′ Postoperative (cm/s)	12.5 ± 3.6	12.7 ± 3.4	0.801
RV-FDI	1.09 ± 0.17	1.09 ± 0.15	0.994

MIAS Minimally invasive aortic surgery, TAPSE Tricuspid annular plane systolic excursion, FAC Fractional area change, S′ Tricuspid annular systolic tissue Doppler velocity, RV-FDI Right ventricular functional dissociation index

However, this comparison was considered exploratory because the study was not randomized, the groups differed in selected baseline characteristics, and the sample size was not powered for equivalence testing between surgical approaches. Therefore, the absence of statistically significant differences should not be interpreted as evidence that surgical approach or pericardial opening pattern has no effect on postoperative RV functional changes.

Exploratory regression analysis

Exploratory multivariable linear regression was performed to examine variables associated with RV-FDI. The detailed model is provided in Supplementary Table 1.

Preoperative TAPSE and preoperative FAC were associated with RV-FDI in the exploratory model. However, because both variables are mathematically embedded in the RV-FDI formula, these associations were considered expected mathematical relationships rather than independent biological predictors. Operative variables, including cardiopulmonary bypass duration, aortic cross-clamp duration, and surgical approach, were not independently associated with RV-FDI.

Given the modest sample size, the exploratory nature of RV-FDI, and the mathematically coupled dependent variable, these regression findings were interpreted as hypothesis-generating only and were not used to support mechanistic or prognostic conclusions.

Association between RV-FDI and early postoperative clinical outcomes

Exploratory analyses evaluating the relationship between RV-FDI and early postoperative clinical recovery parameters are presented in (Table 6).

Table 6.

Exploratory association between RV-FDI and early postoperative recovery parameters. These analyses were exploratory and underpowered for prognostic inference because overt RV failure did not occur and adverse event rates were low

Outcome	Estimate	95% CI	p value
Inotropic support (per 0.1 RV-FDI)	OR 1.30	0.81–2.09	0.283
Lactate 1 h	r = − 0.193	—	0.273
Lactate 6 h	r = 0.026	—	0.883
Lactate 12 h	r = − 0.068	—	0.703
Lactate 24 h	r = 0.159	—	0.368
Mechanical ventilation duration	r = 0.186	—	0.292
ICU stay	r = 0.158	—	0.371
Hospital stay	r = 0.134	—	0.448

OR Odds ratio, r Spearman correlation coefficient, ICU Intensive care unit, RV-FDI Right ventricular functional dissociation index

RV-FDI was not significantly associated with transient inotropic support, postoperative lactate levels at 1, 6, 12, or 24 h, mechanical ventilation duration, ICU stay, or hospital stay. However, because clinically overt RV failure did not occur and early adverse event rates were low, the absence of significant associations should not be interpreted as evidence that the observed echocardiographic pattern is clinically benign or prognostically irrelevant.

Discussion

Principal findings

The principal finding of this study is that conventional echocardiographic indices of right ventricular function did not change uniformly after elective aortic surgery. Longitudinal RV parameters, particularly TAPSE and tissue Doppler-derived S′ velocity, showed significant early postoperative reductions. FAC also decreased significantly; however, the relative reduction in FAC was smaller than that observed for TAPSE. Therefore, the main observation of the present study is a differential postoperative behavior between longitudinal and area-based RV echocardiographic parameters rather than the validation of a new RV functional index.

This finding is consistent with previous reports showing that reductions in longitudinal RV parameters are frequently observed after cardiac surgery, even in patients without overt postoperative RV failure [5, 6]. The present study extends these observations to an elective aortic surgery cohort by directly comparing the relative magnitude of change in TAPSE and FAC. The results suggest that a postoperative reduction in TAPSE should not automatically be interpreted as a proportional deterioration across all conventional RV functional parameters.

Interpretation of postoperative RV echocardiographic changes

RV systolic function is complex and cannot be fully characterized by a single echocardiographic parameter. Longitudinal shortening is an important component of RV contraction, but RV performance also depends on radial inward motion, free-wall contraction, septal contribution, loading conditions, and ventricular interaction [4, 11, 13]. Therefore, postoperative changes in TAPSE may reflect several mechanisms, including altered geometry, annular translational motion, changes in pericardial constraint, loading alterations, or transient myocardial dysfunction.

In the present cohort, TAPSE and S′ both declined significantly after surgery, supporting the observation that longitudinal RV indices are particularly affected in the early postoperative period. However, FAC showed a smaller relative reduction. This pattern may be compatible with non-uniform changes among conventional RV echocardiographic parameters. Nevertheless, the present study cannot determine whether the smaller reduction in FAC represents true preservation of non-longitudinal RV contraction, changes in loading conditions, geometric effects, or methodological differences between the measured parameters.

Previous studies have reported early postoperative reductions in longitudinal RV motion after cardiac surgery and have suggested that pericardiotomy, changes in ventricular interaction, and procedure-related geometric alterations may contribute to this finding [7, 14–16]. However, because RV strain, three-dimensional RV imaging, pulmonary pressure measurements, RV–pulmonary arterial coupling indices, and cardiac magnetic resonance imaging were not available in the present study, mechanistic interpretation must remain cautious. Accordingly, the observed pattern should be regarded as an echocardiographic finding rather than direct evidence of postoperative RV mechanical remodeling.

RV-FDI as an exploratory descriptive ratio

RV-FDI was calculated to summarize the relative behavior of FAC and TAPSE in a single descriptive ratio. In this cohort, RV-FDI values were greater than unity on average, reflecting the greater relative reduction in TAPSE compared with FAC. However, this result should be interpreted strictly as a descriptive expression of the directly observed difference between percentage changes in TAPSE and FAC.

RV-FDI should not be considered a validated diagnostic, mechanistic, or prognostic marker. Because it is mathematically derived from TAPSE and FAC, it is inherently coupled to its component variables. Therefore, associations between RV-FDI and baseline TAPSE or FAC are expected mathematical relationships rather than independent biological predictors. In addition, ratio-based indices may be affected by measurement variability, scaling differences, regression-to-the-mean effects, and the reproducibility characteristics of their component parameters.

For these reasons, the present analysis does not establish RV-FDI as superior to direct evaluation of %ΔTAPSE and %ΔFAC. Rather, the direct comparison of relative changes in TAPSE and FAC should be considered the primary finding. RV-FDI may be useful only as an exploratory descriptive framework for summarizing this relationship in future hypothesis-generating studies.

Clinical interpretation

Right ventricular dysfunction has been associated with adverse outcomes after cardiac surgery, including increased morbidity and mortality [17, 18]. However, the clinical meaning of isolated early postoperative reductions in longitudinal RV indices remains challenging. In the present study, RV-FDI was not significantly associated with postoperative lactate levels, transient inotropic support, mechanical ventilation duration, ICU stay, or hospital stay.

These findings should not be interpreted as evidence that the observed echocardiographic pattern is clinically benign. The study was not powered to assess prognostic outcomes, and clinically overt RV failure did not occur in this cohort. In addition, only two early deaths were observed, and follow-up was limited to the early postoperative period. Therefore, the absence of significant associations between RV-FDI and clinical recovery parameters may reflect limited statistical power and low event rates rather than true lack of clinical relevance.

The practical implication of the present findings is therefore limited but important: early postoperative RV assessment should be multiparametric. A reduction in TAPSE after aortic surgery should be interpreted alongside FAC, S′ velocity, clinical status, hemodynamics, and other available measures of RV performance. This approach is consistent with current recommendations emphasizing multiparametric RV assessment rather than reliance on a single echocardiographic parameter [10, 19].

Surgical approach and pericardial opening

The comparison between sternotomy and minimally invasive aortic surgery was exploratory. No statistically significant differences were observed between surgical approaches in postoperative TAPSE, FAC, S′ velocity, or RV-FDI. However, the study was not designed or powered to determine whether surgical access or pericardial opening pattern independently influences postoperative RV function.

The absence of statistically significant differences should therefore not be interpreted as evidence of equivalence between sternotomy and minimally invasive approaches. The groups were not randomized, differed in selected baseline characteristics, and included heterogeneous aortic procedures. Moreover, the mechanisms through which pericardial opening, ventricular constraint, and surgical manipulation may influence postoperative RV indices are complex and cannot be adequately resolved using conventional two-dimensional echocardiographic parameters alone.

Accordingly, the present findings do not exclude a potential role of pericardial mechanics or surgical approach in postoperative RV functional changes. They only indicate that, within this limited retrospective cohort, no clear difference between approaches was detected using the available conventional echocardiographic measures.

Limitations

This study has several limitations. First, it was a single-center retrospective observational study with a modest sample size, which may limit generalizability and introduce selection bias. Only patients with complete preoperative and early postoperative echocardiographic data were included; therefore, the findings may not be applicable to all patients undergoing aortic surgery.

Second, echocardiographic assessment was limited to conventional two-dimensional and tissue Doppler parameters. RV strain, three-dimensional RV volumes, pulmonary pressure measurements, RV–pulmonary arterial coupling indices, and cardiac magnetic resonance imaging were not available. This substantially limits mechanistic interpretation of the observed findings. Therefore, the present study cannot determine whether the differential postoperative changes in TAPSE and FAC reflect altered loading conditions, geometric changes, pericardial effects, transient myocardial dysfunction, true changes in RV contractile mechanics, or measurement-related factors.

Third, FAC is itself load-dependent and geometrically limited. Therefore, a smaller relative reduction in FAC should not be interpreted as definitive evidence of preserved radial or non-longitudinal RV function. Similarly, TAPSE and S′ may be influenced by postoperative translational motion, annular displacement, and changes in cardiac geometry. The present findings should therefore be interpreted as a pattern of conventional echocardiographic parameter change rather than direct evidence of a specific physiological mechanism.

Fourth, RV-FDI is a mathematically derived ratio constructed from TAPSE and FAC. As such, it is intrinsically coupled to its component variables and may be affected by measurement variability, scaling differences, regression-to-the-mean effects, and ratio instability. RV-FDI was not validated against advanced imaging or clinical endpoints and should not be interpreted as a diagnostic, mechanistic, or prognostic marker. Associations between RV-FDI and baseline TAPSE or FAC should be regarded as expected mathematical relationships rather than independent biological predictors.

Fifth, multivariable modeling was exploratory and statistically limited by the modest sample size, the derived nature of the dependent variable, and the number of candidate predictors. No internal validation or bootstrap assessment was performed. Therefore, regression findings should be considered hypothesis-generating only and should not be used to support causal or mechanistic conclusions.

Sixth, adverse clinical events were infrequent. No patient developed clinically overt RV failure, only two early deaths occurred, and follow-up was limited to the early postoperative period. Accordingly, the absence of significant associations between RV-FDI and postoperative clinical recovery parameters should not be interpreted as evidence of clinical benignity or lack of prognostic relevance.

Finally, the comparison between sternotomy and minimally invasive aortic surgery was exploratory. The groups were not randomized, differed in selected baseline characteristics, and included heterogeneous aortic procedures. Therefore, the absence of statistically significant differences between surgical approaches should not be interpreted as evidence of equivalence or as proof that pericardial opening pattern has no effect on postoperative RV echocardiographic changes.

Conclusions

Elective aortic surgery was associated with significant early postoperative reductions in conventional right ventricular echocardiographic parameters. Longitudinal indices, particularly TAPSE and S′ velocity, showed marked postoperative decline, while FAC demonstrated a smaller relative reduction. These findings suggest that conventional RV echocardiographic parameters may not change uniformly after aortic surgery.

The primary observation of this study is the differential behavior of longitudinal and area-based RV indices, rather than validation of a new RV functional marker. RV-FDI may provide a simple exploratory description of the relative change between TAPSE and FAC; however, it should not be interpreted as a validated measure of RV mechanics, clinical RV dysfunction, or prognosis.

Postoperative RV assessment should therefore remain multiparametric and clinically contextual. Further prospective studies incorporating RV strain, three-dimensional echocardiography, RV–pulmonary arterial coupling, cardiac magnetic resonance imaging, and longitudinal clinical outcomes are required to clarify the physiological and prognostic significance of these findings.

Supplementary information

Below is the link to the electronic supplementary material.

Abbreviations

RV

Right ventricle

TAPSE

Tricuspid annular plane systolic excursion

FAC

Fractional area change

RV-FDI

Right Ventricular Functional Dissociation Index

Authors' contributions

BBA conceived and designed the study. EBG and DES collected and analyzed the data. MMY and AY performed echocardiographic evaluation. MA and MK performed statistical analysis. HLM supervised the study and critically revised the manuscript. All authors read and approved the final manuscript.

Funding

No funding was received for this study.

Data availability

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved by the Institutional Ethics Committee of Ankara Bilkent City Hospital. All procedures were performed in accordance with the ethical standards of the institutional research committee and with the 1964 Declaration of Helsinki and its later amendments. Due to the retrospective observational design of the study, the requirement for informed consent was waived by the Institutional Ethics Committee of Ankara Bilkent City Hospital.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.