Journal of The Indian Academy of Echocardiography & Cardiovascular Imaging

ORIGINAL RESEARCH
Year
: 2022  |  Volume : 6  |  Issue : 1  |  Page : 8--12

Measurement of Caval Aorta Diameter Index by Transthoracic Echocardiogram in Normal Indian Population


Shailendra Sompura, Venkatesan Sangareddi, N Swaminathan 
 Department of Cardiology, Institute of Cardiology, Madras Medical College, Rajiv Gandhi Government General Hospital, Chennai, Tamil Nadu, India

Correspondence Address:
N Swaminathan
A1, Ground Floor, Govindraj Apartment, Boopathy Nagar, Gengu Reddy Road, Egmore, Chennai - 600 008, Tamil Nadu
India

Abstract

Background: Bedside ultrasonography is a promising noninvasive and rapid technique to assess body fluid status. Early detection of hypovolemia and hypervolemia is crucial to guide management in critically ill patients. There is a considerable demographic variability in the normal range of inferior vena cava dimensions as seen in numerous studies and a steadfast formula to calculate caval diameter based on demographic parameters and body growth is not available till date. Caval aorta diameter index had a positive correlation with invasively measured central venous pressure as established by previous studies done in intensive care units. The simplicity of examination technique makes this index useful in every situation where body fluid status has therapeutic and prognostic implications. This study aims to identify standard normal measurement of caval aorta index by easily available two-dimensional echocardiography in subcostal view and by right coronal approach/transhepatic view in different age groups in Indian patients. Materials and Methods: One hundred and two patients referred for routine cardiac status evaluation who were asymptomatic and clinically normal without any major medical illness with normal echocardiogram were prospectively analyzed and caval aorta index assessed in both subxiphoid and transhepatic right coronal view. Results: Normal caval aorta index measured in subcostal view was 1.108 ± 0.076 and measured in transhepatic view was 1.101 ± 0.082 (mean ± 2 standard deviation). The difference of caval aorta index measured in both views was not significant statistically (P = 0.207). Conclusion: In this study, we provide a normal reference level for sonographic caval aorta index in Indian population measured in subxiphoid and transhepatic views. We also conclude that transhepatic right coronal view measurements for this index are comparable to subcostal view, so both views can be used alternatively when one window is suboptimal.



How to cite this article:
Sompura S, Sangareddi V, Swaminathan N. Measurement of Caval Aorta Diameter Index by Transthoracic Echocardiogram in Normal Indian Population.J Indian Acad Echocardiogr Cardiovasc Imaging 2022;6:8-12


How to cite this URL:
Sompura S, Sangareddi V, Swaminathan N. Measurement of Caval Aorta Diameter Index by Transthoracic Echocardiogram in Normal Indian Population. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2022 [cited 2022 Jul 6 ];6:8-12
Available from: https://www.jiaecho.org/text.asp?2022/6/1/8/330347


Full Text



 Introduction



An accurate assessment of body fluid status is quite challenging in clinical practice, and inappropriate assessment can lead to severe therapeutic complications. Methods currently used for body fluid and hydration status assessment such as physical examination and central venous pressure (CVP) measurement have considerable inter- and intra-observer variability and are prone to erroneous judgment. Ultrasound imaging allows direct rapid noninvasive assessment of hydration status at the bedside and can guide further management.[1],[2] Sonographic inferior vena cava (IVC) diameter assessment has been used for decades, but demographic variability in normal reference range makes the interpretation highly error prone. Moreover, a positive correlation between IVC diameter, aortic dimensions, and body surface area (BSA) has been established already. Correlating IVC dimensions with BSA in critically ill patients is not only difficult but also time-consuming, especially when rapid therapeutic decisions are warranted in intensive care unit settings. The adult echocardiography guidelines (American Society of Echocardiography chamber quantification guidelines 2015) do not recommend correlating IVC diameter with age, gender, body weight, etc., among adult subjects. Instead, only one single cutoff value (21 mm) has been recommended.[3] Using a single cutoff for everyone is obviously inappropriate as numerous studies have shown variability in IVC size based on BSA and demographic parameters. The caval aorta diameter index compares IVC diameter with aortic diameter. Aortic diameter is independent of body fluid status and correlates with body growth and surface area similar to IVC diameter.[4],[5] Caval aorta index obviates the need to measure BSA in critically ill patients and at the same time provides a reliable estimate of body fluid status as it has a significant positive correlation with invasively measured CVP as established by previous studies done in critical care settings.[6],[7] Caval aorta index can be assessed bedside by readily available two-dimensional (2D) echocardiography in subxiphoid and right coronal transhepatic view to guide further management based on body fluid status. However, normal values of caval aorta index for Indians are not available.

 Materials and Methods



Clinically normal asymptomatic Indian patients referred for routine cardiac evaluation at outpatient department were prospectively recruited. All subjects had no prior history of diabetes mellitus, hypertension, chronic kidney/liver/lung disease, brain stroke, smoking, connective tissue disorder, bicuspid aortic valve/congenital heart disease, coronary artery disease, valvular heart disease, heart failure, or cardiomyopathy. The study population consisted of 102 subjects aged between 18 and 50 years evaluated at outpatient department, institute of cardiology (December 2020–May 2021). Informed consent of all patients was obtained and prior permission from the institute of cardiology was obtained for the study. All subjects had a structurally normal heart with normal electrocardiogram and normal biventricular function, normal chamber size on 2D echocardiography.

Transthoracic echocardiogram was performed using a 3.5 MHz transducer in the supine position. All measurements were done twice and images were acquired by a single observer. IVC and aorta dimension measurements were done in subcostal and right coronal transhepatic view. In subcostal long-axis view, maximum expiratory and minimum inspiratory IVC diameter was measured in M-mode image which was acquired by placing the M-mode line through IVC, 1 cm caudal to its junction with hepatic vein [Figure 1]. This ensured that we did not measure intrathoracic IVC during any part of the respiratory cycle. Only outpatients who had more than 50% inspiratory collapse of IVC were taken for study and subjects were asked to take short sniffs during M-mode measurement of IVC diameter so that inspiratory collapse could be measured accurately. Maximum systolic diameter in M-mode of the aorta from inner wall to inner wall was recorded in subxiphoid-long axis view [Figure 2]. Similarly, maximum IVC and aorta diameters were measured in the right coronal transhepatic view [Figure 3] and [Figure 4]. Caval aorta index was calculated as the ratio of maximum IVC diameter to maximum aortic diameter calculated separately for subxiphoid long-axis and right coronal transhepatic views.{Figure 1}{Figure 2}{Figure 3}{Figure 4}

 Results



The study consisted of 102 subjects including 60 males and 42 females (male – 59%, female – 41%). The age distribution of the study subjects is shown in [Table 1].{Table 1}

When measured in subxiphoid long-axis view [Table 2] and [Table 3], the following values were obtained:{Table 2}{Table 3}

Maximum expiratory IVC diameter (dm) – 16.18 ± 3.62 mm (mean ± 2 standard deviation [SD])Minimum inspiratory IVC diameter – 7.05 ± 2.26 mm (mean ± 2 SD)Maximum aortic diameter – 14.59 ± 3.32 mm (mean ± 2 SD)Caval aorta diameter index (Maximum IVC diameter/Maximum Aortic diameter) – 1.108 ± 0.076 (mean ± 2SD).

Collapsibility index in all subjects was measured and was more than 50%, as mentioned in inclusion criteria in materials and methods.

When measured in transhepatic right coronal view [Table 4] and [Table 5], the following values were obtained:{Table 4}{Table 5}

Maximum expiratory IVC diameter – 16.39 ± 3.44 mm (mean ± 2 SD)Maximum aortic diameter – 14.89 ± 3.26 mm (mean ± 2 SD)Caval aorta diameter index (maximum IVC diameter/maximum aortic diameter) – 1.101 ± 0.082 (mean ± 2 SD).

Difference between caval aorta diameter index obtained from subxiphoid and transhepatic right coronal views was not significant statistically [Table 6], P = 0.207.{Table 6}

 Discussion



A fast and reliable noninvasive tool to assess intravascular volume status is of prime significance in both medical and surgical illnesses, especially in those with clinical instability. Recently, there is an interest in a new tool to assess volume status in emergency settings, the sonographic caval aorta diameter index which had been shown to correlate with CVP, as studied by Baradey and Shmaa.[8],[9] The correlation of IVC diameter, body height, and BSA has already been proven in critically ill or emergency patients but accessing BSA in these circumstances is difficult and time-consuming. To increase accuracy, IVC diameter may be compared with a parameter independent of intravascular fluid status and correlating with BSA. Abdominal aorta is noncollapsible and maintains a relatively constant diameter irrespective of the body fluid status. The aortic diameter correlates with BSA, age, and sex of the patient. Sridhar et al. compared caval aorta index with the CVP for fluid administration and concluded that caval aorta index was quick, simple, and reliable noninvasive method to assess fluid status in busy setups like an emergency room.[10],[11] Thus, the caval aorta index may play an important role in diagnosing fluid status in emergency patients. The simplicity of the examination technique with quite constant measurement points can eliminate the examiner dependence. The caval aorta index assessment may be used in every situation where body fluid status affects further treatment and prognosis. CVP being an invasive mode has its own list of complications which makes sonographic caval aorta index a preferable noninvasive option.

Data on normal reference range for caval aorta index are limited, esp. in Indian patients. Kosiak et al. calculated the normal value of caval aorta index as 1.2 ± 0.34 measured in traditional subcostal long-axis view and also established that caval aorta index was a handy tool and could be assessed reliably by sonographers with little ultrasound experience. They concluded that application of this method by physicians who are not radiologists would enable fast, emergency sonographic assessment of the hydration status in daily practice.[12],[13]

We studied 102 Indian participants and calculated caval aorta index in both subcostal long-axis and transhepatic views. Caval aorta diameter index measured in subcostal long-axis view was 1.108 ± 0.076 and in transhepatic right coronal view, it measured 1.101 ± 0.082. The difference was not significant statistically which gives the impression that both views can be used with reliability in emergency care settings. Furthermore, one can alternatively use transhepatic right coronal view when subcostal view image quality is poor and vice versa. Caval aorta index calculated in our study was comparable across all age groups and both genders with nonsignificant variations which again reiterates the claim of previous studies which established that caval aorta index was not significantly affected by body size as opposed to IVC and aorta diameter, e.g., as studied by Gui et al.[14],[15]

Limitations

In this study, we recruited subjects who were euvolemic as per clinical assessment and obtained sonographic parameters to calculate the normal reference range for caval aorta index. A large study involving patients with varying fluid status is required to demonstrate applicability of our findings to wider clinical settings. Correlation with invasive parameters like CVP was not assessed in this study.

 Conclusions



In this study, we provide a normal reference level for sonographic caval aorta index in Indian population measured in subxiphoid and transhepatic views.

Caval aorta diameter index measured in subcostal long-axis view was 1.108 ± 0.076 and in transhepatic right coronal view, it measured 1.101 ± 0.082.

We also conclude that transhepatic right coronal view measurements for this index are comparable to subcostal view, so both views can be used alternatively when one window is suboptimal.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Carr BG, Dean AJ, Everett WW, Ku BS, Mark DG, Okusanya O, et al. Intensivist bedside ultrasound (INBU) for volume assessment in the intensive care unit: A pilot study. J Trauma 2007;63:495-500.
2Stawicki SP, Braslow BM, Panebianco NL, Kirkpatrick JN, Gracias VH, Hayden GE, et al. Intensivist use of hand-carried ultrasonography to measure IVC collapsibility in estimating intravascular volume status: Correlations with CVP. J Am Coll Surg 2009;209:55-61.
3Lang RM, Badano LP, Mor-Avi V, Afilalo J, Armstrong A, Ernande L, et al. Recommendations for cardiac chamber quantification by echocardiography in adults: An update from the American society of echocardiography and the European association of cardiovascular imaging. J Am Soc Echocardiogr 2015;28:1-39.e14
4Pearce WH, Slaughter MS, LeMaire S, Salyapongse AN, Feinglass J, McCarthy WJ, et al. Aortic diameter as a function of age, gender, and body surface area. Surgery 1993;114:691-7.
5Son KH, Kim MR, Kim YW, Yoon YS. The utility of the IVC/Aorta diameter index in trauma patients. J Korean Soc Emerg Med 2010;21:35-43.
6Yang JI, Han KH, Cho SU, Lee SH, You YH, Ryu S, et al. Correlation between sonographic inferior vena cava/aorta diameter index and central venous pressure. J Korean Soc Emerg Med 2010;21:341-6.
7Yanagawa Y, Sakamoto T, Okada Y. Hypovolemic shock evaluated by sonographic measurement of the inferior vena cava during resuscitation in trauma patients. J Trauma 2007;63:1245-8.
8Choi YA, Kwon H, Lee JH, Jung JY, Choi YJ. Comparison of sonographic inferior vena cava and aorta indexes during fluid administered in children. Am J Emerg Med 2018;36:1529-33.
9Baradey GF, Shmaa NS. Does caval aorta index correlate with central venous pressure in intravascular volume assessment in patients undergoing endoscopic transuretheral resection of prostate? Saudi J Anaesth 2016;10:174-8.
10Krause I, Birk E, Davidovits M, Cleper R, Blieden L, Pinhas L, et al. Inferior vena cava diameter: A useful method for estimation of fluid status in children on haemodialysis. Nephrol Dial Transplant 2001;16:1203-6.
11Sridhar H, Mangalore P, Chandrasekaran VP, Manikam R. Caval aorta index and central venous pressure correlation in assessing fluid status! Ultrasound bridging the gap. ISRN Emerg Med 2012;2012:1-5.
12Kosiak W, Žwiętoń D, Czarniak P, Kujawa M, Piskunowicz M. Usefulness of ultrasound examination in evaluation of body fluid status. Ultrasonografia 2008;8:12-4.
13Durajska K, Januszkiewicz E, Szmygel Ł, Kosiak W. Inferior vena cava/aorta diameter index in the assessment of the body fluid status – A comparative study of measurements performed by experienced and inexperienced examiners in a group of young adults. J Ultrason 2014;14:273-9.
14Chen L, Kim Y, Santucci KA. Use of ultrasound measurement of the inferior vena cava diameter as an objective tool in the assessment of children with clinical dehydration. Acad Emerg Med 2007;14:841-5.
15Gui J, Yang Z. Impact of body characteristics on ultrasound-measured inferior vena cava parameters in Chinese population. Braz J Med Bio Res 2019;52:e8122.