Dynamic assessment of the tricuspid annulus in a healthy Asian population: A four‐dimensional echocardiography study

Tricuspid annulus (TA) geometry and function reference values are limited, especially for Asian populations. We aimed to explore TA using four‐dimensional echocardiography (4DE) in a healthy Asian population.

The purposes of the present study were (i) to obtain accurate reference values for the morphological structure and dynamic changes of the TA in healthy Asian volunteers during the cardiac cycle, (ii) to evaluate the effects of sex and age on TA parameters, and (iii) to evaluate TA parameters in relation to tricuspid valve (TV) tenting, right ventricle (RV), and right atrium (RA) parameters.

Study population
A group of 372 healthy Asian volunteers was prospectively recruited from April 2021 to July 2021. The inclusion criteria were as follows: age ≥18 years, body mass index < 30 kg/m 2 , normal electrocardiogram, normal results on physical examination, no history of cardiovascular or respiratory diseases, and normal results on 2DE (according to the current guidelines and normal values of cardiac size and function of the World Alliance of Societies of Echocardiography Study). [7][8][9][10][11][12][13] The protocol was approved by the Institutional Ethics Committee, and all volunteers provided written informed consent before undergoing the examinations. Body surface area (BSA) was calculated by using the formula of Du Bois and Du Bois. 14

Echocardiographic acquisition
Transthoracic 4DE was acquired using a Vivid E95 scanner (GE Vingmed Ultrasound) equipped with a 4 Vc matrix array transducer. Full-volume, multibeat (3-4 beats) live 4DE images of the TV, RV, and RA was obtained over 3-4 consecutive cardiac cycles from the RV-focused apical view. The average frame rate was >20 vps. All 4D datasets were stored digitally and analyzed offline.

Echocardiographic measurements
4DE images were analyzed using EchoPAC v204 (GE Vingmed Ultrasound). Quantitative parameters of the RV were analyzed with a software package (4D Auto RVQ) ( Figure 1A). Quantitative parameters of the RA were analyzed with a software package (4D Auto LAQ) designed for the quantitative analysis of the left atrium ( Figure 1B).
Quantitative parameters of the TV were analyzed with a software package (4D Auto TVQ). First, the Align Views stage was used to display a 3D volume rendering to obtain optimal four-chamber (4Ch) and orthogonal views at the TA level ( Figure 2A). Then, the anchor points were placed appropriately ( Figure 2B). Segmentation was performed automatically when the final anchor point was set ( Figure 2C). Further editing was made on the rotational plane if needed. In the dynamic layout interface, a plot of measurements obtained during the cardiac cycle was displayed with two-dimensional (2D) slices and a 3D view ( Figure 2D). The corresponding dynamic value curve is shown by select-ing a measurement in the right panel. Several measurements were calculated automatically from the obtained 4DE images ( Figure 3). The intra-and inter-observer variability of the TA parameters at end diastole (ED) was estimated in 20 random subjects by Bland-Altman analysis. One observer analyzed the same 4DE images at two different times to evaluate intra-observer variability. Two independent, blinded observers analyzed the 4DE images to assess inter-observer variability.

Statistical analysis
All data were analyzed using SPSS 25.0 (SPSS, Chicago, IL, USA).
When p < 0.05, the difference between variables was considered significant.

RESULTS
Seventeen subjects were excluded from enrollment due to poor 2DE or 4DE images, leading to the feasibility of TA quantitative assessment being 95.4%. The clinical characteristics and right heart parameters of the enrolled population are summarized in Table 1. As expected, the RV and RA ejection fractions were significantly lower, and other right heart parameters were significantly larger in males.

Sex differences in TA parameters
TA parameters were compared between sexes at ED (

Age differences in TA parameters
There was no significant difference in most TA geometry parameters by age group at ED, except for some 2Ch and 4Ch diameters ( Table 5, and ≥50 years groups.

Correlations with TV tenting volume and right heart parameters
The maximum TV tenting heights were 8 mm (7-9), 5 mm (4-6), and 4 mm (4-5) at ED, MS, and ES, respectively. The TV tenting volumes were 1.5 ml (1.2-2.0), 1.0 ml (.8-1.2), and .8 ml (.5-1.0) at ED, MS, and ES, respectively. The relationships between the parameters of TA at ED and the parameters of the TV at ED and right heart are detailed in Table 7.

Inter-observer and intra-observer variability
The intra-and inter-observer variability of the 4DE TA parameters at ED are shown in Table 8 and indicated very high intra-and inter-observer reproducibility.

DISCUSSION
This study is the first to use 4DE to quantitatively analyze the TA nonplanar geometry and dynamic changes in a healthy Asian population.
Due to the complex 3D geometry of the TA, the parameters of the TA  18 It is reasonable to assume that the same finding will occur in the TA. Guta et al. 16

Sex and age differences
Our study identified sex as a contributing factor to TA geometry and function. Nonindexed TA parameters in females were significantly smaller than those in males. However, BSA-indexed TA dimensions at ED were significantly larger in females, which is consistent with the study by Addetia et al. 2 Fractional changes in TA 3D areas, 2D areas, perimeters, 2Ch diameters and minor diameters were larger in males than females, implying that the TA is more dynamic in normal males than in females. This result is contrary to that from the study by Addetia et al. 2 Most TV parameters did not differ significantly by age group, suggesting that age is not an independent predictor of TA dilatation.
Notably, the fractional changes in some TA parameters were significantly greater in persons aged ≥ 50 than in persons aged < 50, implying that TA mobility is greater in older adults.

Clinical implications
As a noninvasive and convenient technique, 4DE enables the quantification of the dynamic changes in the normal TA geometry during the cardiac cycle.

Study limitations
Acquiring and quantifying 4DE datasets using a single provider platform may affect the applicability of these reference values to data obtained from other provider platforms. Moreover, the limited availability of cardiac magnetic resonance and ethical considerations prevented us from verifying the validity of the TA measurements in this study. However, the quantitative measurements of the parameters in our study were well described, and prognostic validation was performed. 31 Finally, although all subjects were asymptomatic on regular exams, the possibility of subclinical cardiovascular or respiratory disease cannot be ruled out, particularly in elderly subjects.