Study Of Ultrasound Windows For Measuring Inferior Vena Cava Changes Before Cardiac Surgery (THRIVE-CARD)

December 11, 2025 updated by: Sunnybrook Health Sciences Centre

Comparison of Transhepatic and Subcostal Views for Assessing Inferior Vena Cava Diameter Variation in Cardiac Surgery Patients

This research study will compare two ultrasound methods for assessing the inferior vena cava (IVC), a major vein that reflects intravascular fluid status and cardiac function before and after surgery. The standard method uses a subcostal ultrasound view obtained below the breastbone, but this approach may be limited in patients with obesity, surgical dressings, or postoperative discomfort. An alternative approach, the transhepatic view, uses the liver as an acoustic window and may provide improved feasibility in these situations.

The study will evaluate whether the transhepatic view provides measurements comparable to the standard subcostal view and whether operators with different levels of ultrasound experience obtain consistent results using both methods. Adult patients who are awake and scheduled for cardiac surgery at Sunnybrook Health Sciences Centre will undergo a brief ultrasound examination before surgery. The scan takes less than 10 minutes, involves no discomfort, and does not alter clinical care. This is a minimal-risk observational study with no therapeutic interventions. Participation is voluntary, and all personal health information will remain confidential. Findings may inform future approaches to ultrasound-guided assessment and training in perioperative care.

Study Overview

Status

Not yet recruiting

Conditions

Detailed Description

Respiratory variation in inferior vena cava (IVC) diameter is a widely accepted non-invasive marker of intravascular volume status and fluid responsiveness, particularly in spontaneously breathing patients. Among transthoracic echocardiographic windows, this variation is most commonly assessed using the subcostal (SC) view, which is considered the clinical reference standard due to its direct acoustic pathway and extensive validation in research and clinical practice. The physiologic basis for this measure is strongest in the context of spontaneous respiration, where negative intrathoracic pressure significantly influences venous return dynamics. For this reason, the study population is limited to spontaneously breathing patients to ensure physiologic consistency and interpretive validity.

The SC view, however, may be limited by factors such as body habitus, postoperative dressings, or an obstructed subxiphoid window. The transhepatic (TH) view has been proposed as a complementary or alternative approach, providing an oblique acoustic window through the liver that facilitates visualization of the IVC long axis. Several observational studies have reported strong correlation and agreement between TH and SC measurements of IVC diameter and collapsibility, including in both spontaneously breathing and mechanically ventilated patients. Despite these promising findings, prior studies have been constrained by small sample sizes, heterogeneous methodologies, and limited assessment of reproducibility-particularly across operators with different levels of ultrasound experience. These gaps underscore the need for a larger, methodologically rigorous validation study.

The primary objective of this prospective, single-center observational study is to evaluate agreement between the SC and TH views using methodological standards aligned with diagnostic accuracy frameworks such as QUADAS-2, in a larger cohort of patients scheduled for cardiac surgery. The secondary objective is to assess interrater reliability of TH and SC IVC measurements obtained by novice and expert sonographers. The results are intended to strengthen the evidence base supporting the use of the transhepatic view in perioperative care and to inform future training, competency assessment, and quality-assurance processes in point-of-care ultrasound.

Study Type

Observational

Enrollment (Estimated)

283

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • Canada
    • Ontario
      • Toronto, Ontario, Canada, M4N 3M5

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

The study population consists of adult patients scheduled to undergo elective cardiac surgery at Sunnybrook Health Sciences Centre. Eligible participants will be spontaneously breathing and able to lie supine during ultrasound assessment. The study will include male and female patients aged eighteen years or older, with no upper age limit. Exclusion criteria focus on conditions that impair accurate visualization of the inferior vena cava, including right heart failure, significant tricuspid regurgitation, portal hypertension, end-stage renal disease, obstructive dressings, or inadequate acoustic windows despite optimization maneuvers. This population reflects typical perioperative cardiac surgery patients in whom reliable non-invasive assessment of fluid status is clinically relevant.

Description

Inclusion Criteria:

  • Adults aged eighteen years or older
  • Scheduled to undergo cardiac surgery at Sunnybrook Health Sciences Centre
  • Spontaneously breathing at the time of ultrasound assessment
  • Able to lie supine for image acquisition
  • Able to provide written informed consent

Exclusion Criteria:

  • Inability to lie supine
  • Known right heart failure
  • Moderate to severe tricuspid regurgitation
  • Portal hypertension
  • End-stage renal disease
  • Presence of abdominal dressings or conditions that preclude transhepatic imaging
  • Poor acoustic windows that prevent adequate measurement from either the subcostal or transhepatic view, despite standard optimization techniques (positioning, breathing coaching, depth and gain adjustment, probe angulation)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Adult Cardiac Surgery Patients
This group includes adult patients (Age ≥ 18) who are awake, spontaneously breathing, and scheduled to undergo cardiac surgery at Sunnybrook Health Sciences Centre. They must also be able to lie supine and provide informed consent.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Agreement for collapsibility index (cIVC) between transhepatic and subcostal views
Time Frame: Preoperative period, within twenty-four to forty-eight hours before cardiac surgery.

Outcome Metric: Intraclass correlation coefficient (ICC) for the collapsibility index (unitless).

Rationale: To determine agreement between transhepatic and subcostal cIVC measurements.
Preoperative period, within twenty-four to forty-eight hours before cardiac surgery.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Inter-rater reliability for transhepatic collapsibility index (cIVC)
Time Frame: Preoperative period, during the same imaging session.

Metric: ICC(2,1) for cIVC (unitless).

Rationale: To assess reproducibility between novice and expert sonographers.
Preoperative period, during the same imaging session.
Agreement for IVC maximum diameter (IVCmax)
Time Frame: Preoperative period, during the same imaging session.
Metrics: ICC for IVC maximum diameter (millimetres). Rationale: To determine whether transhepatic and subcostal measurements of IVC maximum diameter demonstrate sufficient agreement to support interchangeable use of the two ultrasound views for this parameter.
Preoperative period, during the same imaging session.
Bland-Altman analysis for IVC diameter ratio (IVCmax:IVCmin)
Time Frame: Preoperative period, during the same imaging session.

Outcome Metric:

Bland-Altman bias and limits of agreement for the IVC diameter ratio (unitless).

Rationale:

To assess systematic bias and variability in the ratio of IVC maximum to minimum diameter across the two ultrasound views, offering an additional perspective on agreement in dynamic IVC behavior.
Preoperative period, during the same imaging session.

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
Agreement for IVC minimum diameter (IVCmin)
Time Frame: Preoperative period, during the same imaging session.

Outcome Metric:

Intraclass correlation coefficient (ICC) for IVC minimum diameter (millimetres).

Rationale:

To evaluate the agreement between transhepatic and subcostal measurements of IVC minimum diameter, which contributes to understanding the consistency of static diameter assessment across imaging windows.
Preoperative period, during the same imaging session.
Agreement for IVC diameter ratio (IVCmax:IVCmin)
Time Frame: Preoperative period, during the same imaging session.

Outcome Metric:

Intraclass correlation coefficient (ICC) for the ratio of IVC maximum to IVC minimum diameter (unitless).

Rationale:

To assess agreement for the proportional relationship between maximum and minimum IVC diameters, providing additional information on dynamic venous diameter behavior across ultrasound views.
Preoperative period, during the same imaging session.
Bland-Altman analysis for collapsibility index (cIVC)
Time Frame: Preoperative period, during the same imaging session.

Outcome Metric:

Bland-Altman bias and limits of agreement for the collapsibility index (unitless).

Rationale:

To quantify systematic bias and random variation between transhepatic and subcostal collapsibility index measurements, complementing correlation-based agreement metrics.
Preoperative period, during the same imaging session.
Bland-Altman analysis for IVC maximum diameter
Time Frame: Preoperative period, during the same imaging session.

Outcome Metric:

Bland-Altman bias and limits of agreement for IVC maximum diameter (millimeters).

Rationale:

To characterize systematic differences and dispersion between transhepatic and subcostal measurements of IVC maximum diameter, informing clinical interpretability of any observed discrepancies.
Preoperative period, during the same imaging session.
Bland-Altman analysis for IVC minimum diameter
Time Frame: Preoperative period, during the same imaging session.

Outcome Metric:

Bland-Altman bias and limits of agreement for IVC minimum diameter (millimeters).

Rationale:

To evaluate the magnitude and spread of measurement differences in IVC minimum diameter between transhepatic and subcostal views, providing a detailed assessment of potential measurement error.
Preoperative period, during the same imaging session.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sunnybrook Health Sciences Centre

Investigators

  • Principal Investigator: Jacobo Moreno Garijo, MD, PhD, Sunnybrook Health Science Centre

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

January 1, 2026

Primary Completion (Estimated)

October 1, 2028

Study Completion (Estimated)

December 1, 2028

Study Registration Dates

First Submitted

November 17, 2025

First Submitted That Met QC Criteria

December 11, 2025

First Posted (Actual)

December 26, 2025

Study Record Updates

Last Update Posted (Actual)

December 26, 2025

Last Update Submitted That Met QC Criteria

December 11, 2025

Last Verified

July 1, 2025

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • 6762

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

De-identified individual participant data (IPD) underlying published results (including ultrasound measurements and basic demographic variables) will be made available to qualified researchers upon reasonable request to the Principal Investigator, following publication of the primary manuscript. Data will be stored on secure institutional servers at Sunnybrook Research Institute.

IPD Sharing Time Frame

De-identified individual participant data (IPD) and supporting documents (study protocol, statistical analysis plan, and analytic code) will be made available beginning 12 months after publication of the primary manuscript. Data will remain available for a minimum of 5 years following publication, through secure institutional servers at Sunnybrook Research Institute. Access will be granted to qualified researchers upon reasonable request to the Principal Investigator, subject to a data sharing agreement that ensures privacy and appropriate use.

IPD Sharing Access Criteria

De-identified individual participant data (IPD) and supporting documents (study protocol, statistical analysis plan, and analytic code) will be accessible to qualified researchers affiliated with academic or healthcare institutions. Requests must include a brief research proposal outlining objectives, methods, and intended use of the data. Access will be granted upon approval by the Principal Investigator and execution of a data-sharing agreement that ensures compliance with privacy, confidentiality, and ethical use standards. Approved researchers will receive access to the data through secure institutional servers at Sunnybrook Research Institute.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ANALYTIC_CODE

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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