Introduction

Transcatheter tricuspid valve intervention radiation dose optimization has become a pressing clinical priority as procedural volumes for tricuspid regurgitation surge across Europe, North America, and Asia-Pacific. Severe tricuspid regurgitation (TR) affects more than 1.6 million people in the United States alone, with surgical mortality exceeding 10% in isolated tricuspid operations and rising sharply with age and comorbidity. Transcatheter solutions—transcatheter tricuspid valve replacement (TTVR) with the EVOQUE system and edge-to-edge repair (TEER) with the TriClip system—have demonstrated safety and efficacy in pivotal trials, driving rapid adoption and the need for standardized radiation safety protocols.[1]

These procedures are structurally complex. The tricuspid annulus is large (typically 35–45 mm in diameter), non-planar, and intimately related to the right coronary artery, the conduction system, and the inferior vena cava. Device delivery requires 20–28 French venous sheaths, steerable guiding systems, and precise coaxial alignment with the annular plane—often under prolonged fluoroscopic guidance. First-generation operator learning curves are steep, with procedural times frequently exceeding 90 minutes and fluoroscopy times of 45–60 minutes. In obese patients, where automatic exposure control (AEC) drives tube output to maximum, cumulative air kerma can exceed 2.5 Gy per procedure.[2]

For interventional cardiologists, radiographers, and cath lab administrators, mastering dose reduction during transcatheter tricuspid valve interventions is therefore essential. The good news is that these procedures are uniquely suited to dose optimization: unlike coronary interventions, which demand high temporal resolution for guidewire navigation in moving arteries, tricuspid procedures rely primarily on three-dimensional transesophageal echocardiography (3D TEE) and intracardiac echocardiography (ICE) for anatomical guidance. Fluoroscopy serves a secondary, confirmatory role—meaning that frame rates, projection angles, and cine acquisition can be aggressively minimized without compromising procedural safety. This article presents a comprehensive, evidence-based fluoroscopy protocol for transcatheter tricuspid valve intervention radiation dose optimization, integrating projection selection, exposure parameter modulation, echocardiography-first guidance, and scatter protection with SATPRO lead-free bismuth drapes.

Tricuspid valve anatomy and pathophysiology

The tricuspid annulus and its spatial complexity

The tricuspid valve is the largest of the cardiac valves, with an annular circumference of 100–120 mm and an area of 7–11 cm² in healthy adults. Unlike the relatively planar mitral annulus, the tricuspid annulus is distinctly non-planar, with its septal portion displaced apically by 5–10 mm relative to the anterior and posterior portions. This "apical displacement" is exaggerated in functional tricuspid regurgitation, where right ventricular dilation and annular stretch create a flattened, enlarged, and eccentric annular geometry that challenges device sizing and deployment.[3]

The annulus is intimately related to critical structures that demand precise visualization during intervention. The right coronary artery courses within 2–5 mm of the anterior annulus in 80% of patients, making coronary compression a recognized risk during TTVR implantation. The atrioventricular node and bundle of His lie near the septal annulus, explaining the 5–10% incidence of complete heart block requiring permanent pacemaker implantation after transcatheter tricuspid procedures. The inferior vena cava enters the right atrium posteriorly, and its relationship to the posterior annulus influences delivery sheath trajectory and stability. Each of these anatomical relationships demands careful imaging—but the majority of that imaging can be provided by echocardiography rather than fluoroscopy.

Mechanisms of tricuspid regurgitation

Functional (secondary) tricuspid regurgitation accounts for over 80% of cases referred for transcatheter intervention. The mechanism is leaflet tethering due to right ventricular dilation and papillary muscle displacement, combined with annular dilatation that prevents adequate leaflet coaptation. Primary tricuspid regurgitation—due to prolapse, flail, or endocarditis—is less common but may be more amenable to edge-to-edge repair because the leaflets themselves are structurally normal and the annulus is not massively dilated.[4]

The severity of TR and the mechanism of regurgitation directly influence procedural complexity and fluoroscopy demand. Massive functional TR with annular dilatation >50 mm requires larger devices, more extensive sheath manipulation, and often multiple grasping attempts to achieve adequate leaflet capture—each adding fluoroscopy time. The transcatheter tricuspid valve intervention radiation dose in these complex cases can exceed that of transcatheter aortic valve replacement (TAVR) by 30–50% if unoptimized protocols are used.

Device landscape: TTVR and TEER systems

Transcatheter tricuspid valve replacement (TTVR)

The EVOQUE tricuspid valve replacement system (Edwards Lifesciences) is a self-expanding nitinol frame with tri-leaflet bovine pericardial tissue, delivered via a 28 French transfemoral venous sheath. The device is available in three sizes (44 mm, 48 mm, and 52 mm annular diameter) and is designed to anchor within the native tricuspid annulus using nine ventricular anchors that grip the leaflet tissue. The procedure involves femoral venous access, transseptal puncture (in some early iterations, though later versions use direct venous approach), steerable sheath advancement to the right atrium, and device deployment under 3D TEE and fluoroscopic guidance.[5]

From a fluoroscopy perspective, TTVR is demanding. The large delivery system (28 French) requires substantial sheath support and frequent position adjustments. The nine ventricular anchors must be deployed with precise rotational alignment to the native leaflets, requiring multiple angiographic and echocardiographic confirmations. Device recapture and repositioning—necessary in 15–20% of cases—adds significant fluoroscopy time. The cumulative transcatheter tricuspid valve intervention radiation dose for TTVR can exceed 2.0 Gy air kerma in complex cases.

Transcatheter edge-to-edge repair (TEER)

The TriClip transcatheter tricuspid valve repair system (Abbott) is an evolution of the mitral MitraClip platform, adapted for the larger tricuspid anatomy. The device uses a steerable guiding catheter (24 French) and a clip delivery system that grasps the anterior and septal (or posterior) leaflets, creating a double-orifice valve. The procedure involves femoral venous access, advancement of the steerable guide to the right atrium, clip arm orientation perpendicular to the line of coaptation, leaflet grasping, and deployment under simultaneous 3D TEE and fluoroscopic guidance.[6]

TEER is less fluoroscopy-intensive than TTVR because the device is smaller and does not require annular anchoring. However, the grasping phase—where the clip arms are advanced into the ventricle, opened, retracted to capture leaflets, and closed—requires precise fluoroscopic confirmation of arm position relative to the annular plane. Multiple grasping attempts (average 2.5–3.5 per procedure in early experience) add cumulative fluoroscopy time. The protocol for dose optimization must address both the primary deployment phase and the iterative grasping process.

Projection optimization for dose reduction

Pure AP as the default angle

The single most effective strategy for reducing transcatheter tricuspid valve intervention radiation dose is maintaining the C-arm in pure anteroposterior (AP, 0°) for the majority of the procedure. The tricuspid valve sits anteriorly in the chest, and in AP projection, the annulus is sufficiently visualized to confirm sheath coaxiality, device trajectory, and gross positioning. More importantly, AP provides the shortest beam path through the thorax, minimizing tissue attenuation and scatter generation. Compared with RAO 30°—the traditional tricuspid annulus profile view—AP reduces entrance skin dose by 25–30%.[7]

The protocol mandates that pure AP (0°) be the default projection for: femoral venous access and large-bore sheath insertion, steerable guide advancement from the inferior vena cava to the right atrium, device delivery system introduction and orientation, and all equipment exchanges. RAO 30°—which profiles the tricuspid annulus and separates the right atrium from the right ventricle—should be reserved for three specific moments: (1) initial annular sizing angiography, (2) confirmation of device alignment with the annular plane, and (3) post-deployment assessment of device position and residual regurgitation.

LAO 30°/caudal 20° for transgastric views

The LAO 30° with 20° caudal angulation—the "transgastric" or "hepatic" view—profiles the inferior vena cava entry into the right atrium and the posterior tricuspid annulus. This view is useful during initial sheath advancement, particularly in patients with dilated right atria or prominent Eustachian valves that may deflect the delivery system. However, caudal angulation increases beam path length through the upper abdomen and elevates scatter generation. The protocol recommends using this view briefly (≤2 minutes) during sheath introduction, then reverting immediately to AP for all subsequent steps.[8]

Projection minimization through echocardiography primacy

The revolutionary aspect of tricuspid intervention dose optimization is that the procedure can be performed with minimal C-arm movement. Because 3D TEE provides superior visualization of annular geometry, leaflet coaptation, and device-annulus interaction, the C-arm need not hunt for the "perfect" fluoroscopic angle. A single pre-procedural angiographic run in RAO 30° defines the annular plane; all subsequent guidance is provided by TEE. This "fluoroscopy-sparing" approach—pioneered in mitral TEER and now adapted for tricuspid procedures—can reduce total fluoroscopy time by 40–50% compared with fluoroscopy-dependent workflows.[9]

Exposure parameters and pulse-rate selection

Automatic exposure control and obesity

The automatic exposure control (AEC) circuit modulates tube potential (kV) and current (mA) to maintain constant image brightness at the detector. In average-sized adults, tricuspid interventions typically require 70–85 kV and 80–250 mA during fluoroscopy, with cine acquisition peaking at 300–500 mA.

In obese patients—body mass index >30 kg/m² or chest thickness >28 cm—AEC drives output toward maximum rated values, often reaching 90–115 kV and 300–700 mA. Under these conditions, entrance skin dose rate can exceed 100 mGy/min, and cumulative air kerma may surpass 2.5 Gy before device deployment is complete.[10] Proactive manual adjustment of the kV setpoint toward the higher end of the range (85–90 kV) while accepting slightly increased image noise can reduce mA demand and total dose by 15–20%. Collimating tightly to the right-heart silhouette further constrains AEC output.

Pulse-rate selection: 3.75–7.5 fps

Tricuspid valve procedures do not require the 15 frames per second (fps) continuous fluoroscopy used in coronary interventions. Because catheter movement in the low-pressure right heart is slower than coronary guidewire manipulation, and because 3D TEE provides the primary navigational data, fluoroscopy serves only as a confirmatory overlay.

The protocol mandates low pulse-rate fluoroscopy at 3.75–7.5 fps: 3.75 fps during stable phases such as sheath introduction, steerable guide positioning, and device advancement; 7.5 fps during dynamic phases including clip arm opening, leaflet grasping, and anchor deployment. Switching from 15 fps continuous to 3.75 fps pulsed reduces patient entrance dose by up to 75% and operator scatter exposure by a commensurate margin without impairing procedural safety.[11][12] Modern flat-panel detectors with dose-saving algorithms can further reduce output by 20–30% at equivalent perceived image quality.

Cine acquisition limits

Cine radiography—high-dose digital acquisition used for documentation—consumes 10–20 times the dose of fluoroscopy per second. In unoptimized tricuspid workflows, operators may acquire 3–5 minutes of cine for annular angiography, device positioning, and final result assessment. The protocol limits total cine time to <60 seconds for the entire procedure. Specific limits: annular sizing angiography ≤15 seconds, device deployment documentation ≤20 seconds, final result assessment ≤15 seconds. All equipment exchanges and wire repositioning must use last-image hold rather than cine. Stored fluoroscopy loops (15–30 seconds at 3.75 fps) provide adequate documentation for medicolegal and educational purposes at roughly 5% of the dose of an equivalent cine run.[13] Enforcing these limits can reduce cumulative air kerma by 40–50% compared with conventional workflows.

3D TEE and ICE as primary visual guidance

3D TEE for annular sizing and device alignment

Three-dimensional transesophageal echocardiography is the cornerstone of safe tricuspid intervention. Multiplanar reconstruction (MPR) allows the operator to generate an en face view of the tricuspid valve from the right atrial perspective, precisely delineating the anterior, septal, and posterior leaflets. For TTVR, 3D TEE confirms annular diameter, measures the distance to the right coronary artery, and guides rotational alignment of the ventricular anchors. For TEER, real-time 3D color Doppler identifies the regurgitant jet origin and guides clip trajectory toward the zone of maximal leaflet malcoaptation.

Because these assessments are performed without contrast injection or C-arm rotation, they eliminate the need for repeated angiographic "test shots" that add dose. Studies of mitral TEER have shown that 3D TEE-primary guidance reduces fluoroscopy time by 45–60%; similar reductions are achievable in tricuspid procedures.[14]

ICE as an alternative in general anesthesia contraindications

Intracardiac echocardiography (ICE) offers an alternative when general anesthesia for TEE is contraindicated—such as in patients with severe esophageal disease, prior esophageal surgery, or difficult intubation anatomy. A 10 French ICE catheter is advanced via femoral venous access into the right atrium, providing high-resolution 2D and Doppler imaging of the tricuspid apparatus from an intracardiac vantage point. While ICE does not yet match the spatial resolution of 3D TEE for annular sizing, it is sufficient for clip orientation, leaflet grasping confirmation, and residual TR assessment. The trade-off is procedural cost and an additional venous access site, but the radiation benefit is preserved because ICE-guided tricuspid TEER can be performed with the same minimal fluoroscopy protocol as TEE-guided cases.[15]

Fusion imaging and roadmap integration

Emerging technologies integrate pre-procedural cardiac CT or intra-procedural 3D TEE with live fluoroscopy, creating a fused roadmap that overlays anatomical landmarks on the X-ray image. For tricuspid intervention, CT-fluoroscopy fusion can mark the tricuspid annular plane, the right coronary artery course, and the optimal device trajectory before the patient enters the cath lab. During the procedure, TEE-fluoroscopy fusion tracks the delivery system in real time relative to the echo-defined annulus, reducing the need for contrast angiography and multiple projection changes. Early experience suggests that fusion imaging can reduce fluoroscopy time by an additional 20–25% beyond TEE-primary guidance alone.[16]

Scatter mitigation with SATPRO protection

Operator dose during femoral venous access

Transcatheter tricuspid procedures require sustained operator presence at the right groin for large-bore venous access, sheath exchanges, and device delivery. During these phases, the operator's hands and torso are positioned within 30–50 cm of the irradiated volume, placing them in the highest scatter zone. Scattered radiation intensity peaks at 90–100 cm from the X-ray source and falls with the inverse square law, but prolonged exposure during 60–90 minute procedures results in non-negligible cumulative operator dose.

First-generation operators performing tricuspid TEER have reported personal dosimeter readings equivalent to 5–10 conventional diagnostic catheterizations per case.[17] The left-sided operator—typically controlling the delivery system—is exposed to more scatter than the right-sided assistant because the beam path traverses the patient's left chest before exiting to the detector in standard AP projection.

SATPRO positioning for tricuspid procedures

SATPRO lead-free bismuth scatter drapes are positioned over the patient's lower abdomen and pelvis, covering the femoral venous access site and the inferior vena cava trajectory.

This placement intercepts scattered radiation at its source before it propagates toward the operator's standing position. The bismuth composite attenuates up to 95% of scatter at diagnostic energies (60–100 kV), with equivalent protection to 0.5 mm lead but without the weight and rigidity of traditional lead aprons.[18] For tricuspid interventions, the drape should be placed immediately after sterile preparation and before sheath insertion, ensuring continuous coverage during all groin manipulation. Additional sterile SATPRO drapes may be suspended vertically between the patient's right thigh and the operator to create a lateral scatter barrier during prolonged device positioning.

Dose monitoring and quality assurance

Real-time dosimetry

Every tricuspid intervention must be performed with active dose monitoring. The interventional reference point air kerma (K_a,r) and kerma-area product (KAP, P_KA) should be displayed in real time on a visible monitor. Alert thresholds are set at 1.5 Gy cumulative air kerma (yellow warning) and 2.0 Gy (red alert), triggering a mandatory timeout to reassess projection, pulse rate, and cine usage. Peak skin dose (PSD) should be estimated post-procedure using available software or the FDA-recommended approximation method.[19] For patients with pre-procedure K_a,r >1.0 Gy from prior interventions within 60 days, the procedure should be staged or alternative non-fluoroscopic guidance maximized to prevent deterministic skin injury.

Quality assurance benchmarks

Cath labs should establish institutional benchmarks for tricuspid intervention dose. Targets for optimized workflows: fluoroscopy time <30 minutes, cine time <60 seconds, cumulative air kerma <1.5 Gy, and KAP <150 Gy·cm² for standard-body patients. Obese patients may exceed these targets by 50%, but any case >3.0 Gy requires root-cause analysis. Quarterly review of dose metrics by procedure type, operator, and device allows identification of outliers and protocol drift.[20] Comparison with published benchmarks from the TRILUMINATE and EVOQUE trials provides external validation; early cohorts in these trials reported median fluoroscopy times of 28–42 minutes and air kerma of 1.2–1.8 Gy, establishing realistic goals for high-volume centers.

Learning curve considerations

The learning curve for transcatheter tricuspid intervention significantly impacts radiation dose. First-generation operators typically require 15–25 cases to achieve proficiency, during which fluoroscopy time and air kerma may be 50–100% higher than experienced operators. Proctored introduction, simulation-based training, and strict adherence to the dose-optimized protocol can compress this curve. We recommend that new operators perform their first 10 cases under direct proctorship with a mandatory "fluoroscopy timeout" every 15 minutes to review projection and pulse-rate compliance. After 20 independent cases, operators should be required to demonstrate fluoroscopy time <35 minutes and air kerma <2.0 Gy before receiving unrestricted privileges.[21]

Conclusion

Transcatheter tricuspid valve intervention represents one of the most radiation-intensive structural heart procedures in contemporary practice—but it does not have to be. The unique anatomy of the tricuspid valve, the large delivery systems, and the prolonged procedural times create genuine challenges, yet these same factors make the procedure exceptionally amenable to dose optimization.

By maintaining pure AP projection for 80% of the case, reducing pulse rates to 3.75–7.5 fps, limiting cine acquisition to <60 seconds, and relying on 3D TEE or ICE as the primary imaging modality, operators can reduce cumulative air kerma by 40–50% without compromising safety or efficacy.[23][25] The addition of SATPRO lead-free bismuth scatter shields over the lower abdomen and groin access site protects both patient and operator from scatter generated during prolonged femoral venous manipulation. Real-time dosimetry, institutional benchmarking, and learning-curve management complete the quality assurance framework. As procedural volumes grow and indications expand to moderate tricuspid regurgitation, implementing these evidence-based protocols will be essential for sustainable, safe delivery of transcatheter tricuspid care.

Further reading

References