Dimensions of the superior and inferior venae cavae (VC) at various levels are larger for patients with isolated severe tricuspid regurgitation (TR) compared with patients who have isolated mitral regurgitation (MR) or no valvular dysfunction. However, specific dimensions do not vary substantially in individuals throughout the cardiac cycle.

Cleveland Clinic researchers reached these conclusions after measuring VC anatomic dimensions using multiphase cardiac CT. Details of their study were discussed in a poster presentation at the 2023 scientific session of the American College of Cardiology.

“Knowing the dimensions of the venae cavae and their spatial relations to the tricuspid valve (TV) in the setting of severe TR has important implications for caval valve implantation devices, including sizing, delivery and anchoring,” explains Cleveland Clinic resident Osamah Badwan, MD, who presented the study.

Burgeoning field needs precise data

Transcatheter TV interventions are increasingly being developed and used to address severe TR in patients for whom surgery is too risky. Designed to prevent downstream complications of reflux, the devices either target the VC or use the VC for access while targeting the TV directly.

Devices for caval valve implantation must be sized correctly, but little is known about VC dimensions either normally or in the setting of severe TR. These transcatheter procedures can also be challenging because VC anatomy can vary with respect to angulation, distance and offset between the VC axes and the TV axis.

To address this lack of knowledge of VC anatomy, the Cleveland Clinic investigators sought to characterize important anatomic characteristics of the VC as well as spatial relationships between the VC and TV in severe TR, using patients without valve dysfunction and age-matched patients with severe isolated MR as comparison groups.

Study design and results

Three study cohorts were drawn from patients who had undergone multiphase cardiac CT with right-sided contrast at Cleveland Clinic between 2017 and 2022. They consisted of:

• 71 patients with isolated severe TR (mean age of 77 years, 58% female)
• 64 patients with isolated severe MR (mean age of 77 years, 64% female)
• 71 patients without valve dysfunction (mean age of 38 years, 56% female)

Multiple dimensions were compared, including measurements of key areas in systole and diastole. All measurements were indexed to body surface area.

Results included the following (see Figure):

• Inferior and superior VC dimensions — including offset between the VC axes, and the angle and height to the center of the TV annulus — were significantly larger in the severe TR cohort compared with the other groups.
• No significant differences were observed between systole and diastole within the groups in the following areas: (1) the right atrial junction levels of both the superior and inferior VC; (2) the level of the pulmonary artery for the superior VC; (3) the level of the suprahepatic vein junction of the inferior VC.

Significance of the findings

Co-investigator Samir Kapadia, MD, Chair of Cardiovascular Medicine at Cleveland Clinic, highlights key findings of the study and their implications:

• VC dimensions are substantially larger in the setting of severe TR. Knowing these dimensions is important for designing devices and finding the right balance between needing a large device in place and limits of transcatheter delivery systems. 
• Measurements were obtained of angulation, distance and offset required to reach the TV from both the superior and inferior VC. “When implanting a tricuspid clip or replacing the tricuspid valve, knowing the precise spatial relationships between the venae cavae and the tricuspid valve is critical for how you maneuver the catheters,” Dr. Kapadia explains.
• Dimensions remained fairly constant within cohorts between systole and diastole. “The fact that dimensions did not change significantly across the cardiac cycle indicates that single-phase CT is adequate for evaluation for transcatheter TV interventions,” adds Dr. Kapadia, who notes that theirs is the first known report of this finding. “Being able to safely avoid multiphase acquisition can substantially reduce radiation exposure to the patient.”

Anatomic understanding drives better innovation

Cleveland Clinic interventional cardiologist Rishi Puri, MD, PhD, another investigator in this study, points out that much innovation is taking place in the TV landscape, with repair, replacement and coaptation embodiments currently being tested at various stages of development.

“As some of these large-bore delivery systems undergo human trials, we have come to appreciate that how they are positioned at vena cava entry significantly affects one’s ability to orient in a coaxial manner to the tricuspid valve,” he says. “Understanding coaxiality is fundamental to optimizing many transcatheter TV device deployments, and this study’s data inform that.”

An overview of caval valve implantation therapies was published by Dr. Puri and European colleagues in the Journal of Clinical Medicine (2021;10:[19]:4601). Details of the TricValve® Transcather Bicaval Valves System were described in a previous Consult QD post. Testing of that system versus standard medical therapy in a pivotal randomized clinical trial is underway, with Drs. Kapadia and Puri as principal investigators under the coordination of the Cleveland Clinic Coordinating Center for Clinical Research (C5Research).

Dr. Badwan adds that the study detailing VC anatomic characteristics in severe TR is expected to be published as a full-length article soon.