TAVR Procedural Planning for Patients With Supra-Annular and Sinotubular Junction Constriction

Abstract

Objectives

Calcific constriction of the supra-annular aorta and sinotubular junction (STJ) can significantly impair transcatheter aortic valve replacement (TAVR), leading to suboptimal valve expansion and leaflet dysfunction. We describe a case of severe STJ constraint in which bench testing demonstrated constrained expansion dynamics and informed a tailored transcatheter strategy resulting in successful valve deployment with favorable hemodynamics.

Key Steps

1) Recognition of severe STJ-annulus mismatch and high-risk anatomy on preprocedural computed tomography; 2) bench testing demonstrating constrained expansion and leaflet “cogwheeling”; 3) selection of an appropriate transcatheter valve platform based on anatomical considerations; 4) careful balloon predilation and iterative deployment with optimized (relatively infra-annular) positioning; and 5) use of meticulous procedural techniques to minimize embolic and conduction risk.

Potential Pitfalls

Failure to recognize STJ constraint may result in asymmetric expansion, leaflet dysfunction, sinus sequestration, paravalvular regurgitation, coronary obstruction, or annular injury. Balloon-expandable valves may carry increased risk in rigid anatomies due to abrupt radial force transmission.

Take-Home Messages

Constricted supra-annular aorta and STJ represent a significant challenge in transcatheter aortic valve replacement. Careful 3-dimensional planning, appropriate valve selection, and tailored deployment strategies are essential to optimize procedural and hemodynamic outcomes.

Visual Summary

Summary of STJ Constraint Mechanism and Procedural Strategy

Transcatheter aortic valve replacement (TAVR) has transformed the management of symptomatic severe aortic stenosis, offering a minimally invasive alternative across the full spectrum of surgical risk.¹ Detailed anatomical assessment is increasingly important to anticipate complications related to valve deployment and expansion dynamics.

Supra-annular anatomy plays a critical role in procedural planning. The sinotubular junction (STJ), although not a primary anchoring site, significantly influences stent frame expansion and valve function.² Constriction of the STJ represents an uncommon but important limitation to safe TAVR. In this report, we present a case of severe STJ constraint and highlight a mechanism-guided procedural strategy to optimize valve deployment in this high-risk anatomy.

Case Summary

A 71-year-old man with symptomatic severe aortic stenosis (peak gradient 73 mm Hg, mean gradient 49 mm Hg), prior coronary artery bypass grafting, and NYHA functional class III symptoms underwent transfemoral TAVR. Given prior coronary artery bypass grafting and comorbidities, the patient was considered at increased risk for surgical aortic valve replacement, with an estimated Society of Thoracic Surgeons predicted operative mortality of approximately 3% and a combined morbidity/mortality of 12%, supporting a transcatheter approach despite complex anatomy. Preprocedural computed tomography demonstrated significant annulus-STJ mismatch. The STJ was markedly narrowed and elliptical, measuring 16.8 × 21.2 mm (average diameter, ∼19 mm), compared with an annular mean diameter of 24.7 mm. Severe circumferential calcification (Agatston score, 3,287) further contributed to a rigid, noncompliant supra-annular anatomy. The STJ was located approximately 23.4 mm above the annulus. With an anticipated implantation depth of approximately 3 mm below the annulus, the STJ calcium was estimated to be approximately 26.4 mm from the base of the valve frame, placing the constricted STJ in close proximity to the leaflet-bearing segment of the valve and raising concern for constrained expansion and leaflet dysfunction (Table 1, Video 1).

Table 1.

Anatomic Risk Features and Procedural Implications in Sinotubular Junction (STJ)–Constrained Transcatheter Aortic Valve Replacement

Feature	Finding in This Case	Procedural Implication
STJ diameter	16.8 × 21.2 mm (average diameter, ∼19 mm)	Severe constraint limits valve expansion and promotes leaflet displacement
STJ height from the annulus	23.4 mm	Short vertical clearance may exacerbate leaflet interaction with coronary sinuses
STJ height from the base of the valve frame	26.4 mm	Frame-referenced STJ height indicates the constraint falls at the leaflet level
Ascending aorta diameter	∼33.2 mm	Relative mismatch between the STJ and the ascending aorta highlights focal constraint
Aortic annulus diameter	22-27 mm (mean, ∼24.7 mm)	Larger annulus relative to STJ increases the risk of constrained expansion
Annulus perimeter/area	76 mm/461 mm2	Supports selection of a 27-mm valve platform
STJ-to-annulus relationship	0.77; markedly reduced ratio	Predicts nonuniform expansion and increased procedural risk
Aortic valve calcium burden	Agatston score 3,287	High rigidity → increased risk of leaflet displacement and obstruction
Leaflet morphology	Heavily calcified trileaflet valve	Reduced compliance, increased risk of sinus sequestration
L/R/N Sinus of Valsalva diameters	∼33/33/32 mm	Adequate sinus size but functionally compromised by STJ constraint
Left coronary artery height	13.7 mm	Borderline → increased risk of coronary obstruction
Right coronary artery height	17.0 mm	Moderate risk depending on leaflet displacement
Aortic root angle (coplanar view)	∼53°	Important for procedural alignment and deployment control
Peripheral access (femoral)	≥8-mm vessels bilaterally	Suitable for the transfemoral approach
Valve selection	27-mm Navitor (self-expanding)	Intra-annular leaflets, allows controlled deployment and repositionability
Predilation strategy	22-mm True balloon	Limited by STJ size

Bench Testing and Mechanistic Insight

To better understand the implications of this constrained anatomy on valve expansion, ex vivo bench testing was performed using a simplified mechanical model simulating severe STJ constraint. A commercially available nitrile butadiene rubber O-ring with an internal diameter of approximately 19 mm, corresponding to the patient's measured STJ dimensions, was used to create a fixed supra-annular constraining structure (Figure 1). A 29-mm Evolut (Medtronic) transcatheter valve was deployed within the ring under direct visualization, with the constraining ring positioned approximately 27 mm above the inflow portion of the valve to approximate the patient's measured STJ height (Figure 2). Bench testing demonstrated impaired frame expansion, resulting in leaflet crowding and deformation consistent with "cogwheeling" under constrained conditions (Figures 3 and 4). Frame expansion and leaflet motion were further qualitatively assessed and recorded using video imaging. To qualitatively simulate cyclical blood flow, the deployed valve-ring assembly was subsequently moved through the water surface in a controlled up-and-down fashion, generating alternating flow across the valve. This dynamic assessment further demonstrated restricted leaflet excursion, incomplete leaflet coaptation, and incomplete valve closure (Video 2). These observations provide a plausible mechanistic explanation for the constrained expansion and leaflet behavior observed in this anatomy.

Figure 1.

Digital Caliper Measurement of the Nitrile Butadiene Rubber O-Ring (∼19 mm Internal Diameter) Used to Simulate Severe Sinotubular Junction Constriction

Figure 2.

Bench-Testing Model Demonstrating a 29-mm Evolut Valve Deployed Within an O-Ring Positioned Approximately 27 mm From the Base of the Valve Frame, Corresponding to the Patient's Measured Sinotubular Junction Height

Figure 3.

En Face View of the Constrained Valve From the Outflow (Aortic) Aspect, Demonstrating Leaflet Crowding and Central Coaptation Deformity Consistent With Leaflet "Cogwheeling"

Figure 4.

En Face View of the Constrained Valve From the Inflow (Ventricular) Aspect, Further Illustrating Asymmetric Leaflet Configuration and Restricted Effective Orifice Area Under Severe Supra-Annular Constraint

Although simplified, this model provided mechanistic insight into the effects of severe STJ constraint on valve expansion, leaflet behavior, and the procedural strategy ultimately used in this case. Cross-platform comparative testing was not performed, and these findings should be interpreted as reflecting general principles of constrained valve expansion rather than device-specific performance.

Visual Summary.

Summary of STJ Constraint Mechanism and Procedural Strategy

Left panel: Preprocedural computed tomography demonstrating sinotubular junction (STJ)-annulus mismatch and severe calcification. (A) STJ measurement 16.8 × 21.2 mm (average diameter ∼19 mm). (B) Annular diameter 24.7 mm, demonstrating annulus-STJ size discrepancy. (C) Severe circumferential calcification at the level of the STJ, consistent with a rigid, noncompliant anatomy predisposing to constrained valve expansion. Middle panel: Mechanism of STJ-constrained expansion. Proximal restriction at the STJ with continued distal expansion results in asymmetric frame geometry and leaflet crowding, impaired coaptation, and "cogwheeling." Right panel: Mechanism-guided procedural strategy. Balloon valvuloplasty facilitates expansion within a calcified STJ, and final deployment with infrannular positioning moves the leaflet level away from the constricted STJ, promoting more symmetric valve expansion and leaflet function. TAVR = transcatheter aortic valve replacement.

Procedural Steps

The procedure was performed via transfemoral access under fluoroscopic and transesophageal echocardiographic guidance. Vascular access was obtained in the common femoral artery, with additional access for pigtail catheter positioning and temporary pacing. After crossing the native aortic valve, balloon aortic valvuloplasty was performed using a 22-mm True balloon (BD) under rapid pacing. Given the risk of conduction disturbance with relatively deeper implantation, a temporary pacing wire was prophylactically placed. A 27-mm Navitor (Abbott Vascular) intra-annular self-expanding transcatheter valve was then advanced across the annulus and deployed. Given the high calcium burden and risk of embolization, the use of cerebral embolic protection was considered but not used based on operator judgment.

Fluoroscopy demonstrated nonuniform expansion, with relative narrowing at the level of the STJ and greater expansion below, consistent with a “bottleneck” configuration (Video 3). This dynamic pattern, visually appreciated as “cogwheeling,” reflected differential frame expansion across the STJ, as illustrated mechanistically.

The valve was recaptured once because of suboptimal depth and redeployed in a slightly “deeper” (infra-annular position) position to allow greater leaflet expansion, positioning the leaflets further from the calcified STJ, resulting in improved symmetry and leaflet coaptation. Final deployment was performed only after confirming stable positioning, symmetric frame expansion, and normalization of leaflet motion (Video 4).

After valve deployment, a new conduction delay was observed; the pacing wire was maintained for monitoring, and the abnormality improved during recovery without the need for permanent pacemaker implantation.

Final angiography demonstrated stable valve positioning with symmetric expansion and no significant paravalvular regurgitation. Hemodynamic assessment confirmed resolution of transvalvular obstruction. The previously observed oscillatory leaflet motion resolved after positional optimization, supporting its association with nonuniform frame expansion (Video 4). Postprocedural transesophageal echocardiography demonstrated satisfactory valve position, no significant paravalvular leak, and preserved left ventricular systolic function (Videos 5 and 6).

At 1-month follow-up, transthoracic echocardiography demonstrated normal prosthetic valve function, with a mean gradient of 9 mm Hg, an effective orifice area of 2.6 cm², an acceleration time of 70 milliseconds, and a dimensionless index of 0.7.

Procedural Pitfalls

In STJ-constrained anatomy, rapid full deployment may increase the risk of annular or aortic root injury.³ Failure to recognize constrained expansion may result in frame deformation, paravalvular regurgitation, elevated gradients, or coronary obstruction from displaced calcified leaflets.^4,5

Discussion

Progressive calcific atherosclerotic disease often renders the STJ rigid and noncompliant, frequently in a circumferential or asymmetric pattern that alters expansion behavior.⁶ In the presence of a narrowed STJ, valve expansion may be limited despite appropriate annular sizing, resulting in nonuniform radial force distribution and asymmetric frame geometry. Although no universally accepted threshold exists, a reduced STJ-to-annulus ratio–particularly when the STJ diameter is smaller than the annulus, as observed in this case (STJ-to-annulus ratio, ≈0.77) is associated with constrained expansion and increased procedural complexity. This relationship creates a supra-annular constraint that limits frame expansion despite appropriate annular sizing. Importantly, unfavorable STJ-annulus relationships may confer risk even in the absence of significant calcification.^7,8

In smaller annuli, excessive oversizing particularly in the presence of infra-annular calcification may increase the risk of annular or left ventricular outflow tract injury, underscoring the importance of careful computed tomography–based sizing.⁸ These conditions have been associated with paravalvular regurgitation, elevated transvalvular gradients, valve malposition, coronary obstruction, and, in severe cases, structural injury to the annulus or aortic root.^3,5

Valve selection should be individualized, as both balloon-expandable and self-expanding platforms have limitations in constrained anatomies. Balloon-expandable valves may carry increased risk of annular injury or suboptimal expansion in a narrow, noncompliant STJ, whereas self-expanding valves may be prone to underexpansion and altered leaflet mechanics. Prior reports have demonstrated successful use of alternative transcatheter valve platforms in STJ-constrained anatomy.6, 7, 8, 9 Procedural success is therefore driven by anatomy-specific planning rather than valve platform alone.^6,7

Three-dimensional printing along with benchmark testing and simulation models may assist in predicting expansion dynamics and understanding constrained leaflet motion, thereby informing procedural planning in selected complex anatomies. Cogwheeling is not device-specific and may occur across transcatheter valve platforms in the setting of constrained expansion. Although it was demonstrated in a supra-annular valve model (Evolut), this phenomenon reflects constrained leaflet motion due to asymmetric frame expansion rather than a platform-specific property, and similar dynamics may be observed with intra-annular systems under STJ constraint.

Balloon predilation can be useful in STJ-constrained anatomy to assess compliance and facilitate controlled expansion, particularly when using intra-annular systems such as the Navitor valve, with careful attention to the risks of aortic injury and embolization. Transesophageal echocardiography provides valuable real-time assessment of valve expansion, leaflet motion, and paravalvular regurgitation, especially in complex anatomies such as STJ constraint. Procedural strategy should incorporate controlled deployment with attention to valve positioning, as relatively infra-annular deployment may facilitate more symmetric expansion. Aborting a TAVR procedure should be considered in the presence of inadequate valve expansion, persistent severe paravalvular regurgitation,⁴ elevated mean pressure gradients across valve (>20 mm Hg), coronary compromise,⁵ or hemodynamic instability, as these complications are associated with adverse outcomes and may necessitate escalation of management.

Limitations

Limitations include the use of a simplified bench model that does not reproduce physiologic hemodynamics, absence of comparative valve-platform testing, and lack of a complete fluoroscopic deployment recording.

Conclusions

TAVR, in the presence of a narrow, calcified, and noncompliant STJ, presents unique anatomical and mechanical challenges related to constrained expansion and altered leaflet dynamics. This case highlights the importance of integrating detailed anatomical assessment, appropriate valve selection, and procedural adaptation to optimize valve expansion and function.

Funding Support and Author Disclosures

The authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Take-Home Messages

• •STJ-annulus mismatch is associated with increased procedural risk, leading to constrained valve frame expansion, leaflet dysfunction, and impaired valve hemodynamics.
• •Successful transcatheter aortic valve replacement requires early recognition of STJ constraint and a tailored anatomy-guided procedural strategy.

Appendix

Video 1

Preprocedural Computed Tomography Findings Demonstrating Sinotubular Junction Anatomy

Video 2

Dynamic Bench-Testing Demonstration of a Constrained 29-mm Evolut Valve Within a Simulated Severe STJ Constriction, Illustrating Restricted Leaflet Excursion, Incomplete Leaflet Coaptation, Incomplete Valve Closure, and Leaflet “Cogwheeling”

Video 3

Balloon Valvuloplasty of the Valve Using a 22-mm True Balloon

Leaflets demonstrate normal excursion with symmetric opening and no evidence of leaflet restriction but compressed valve outflow by a calcific ridge.

Video 4

Final Valve Depth Before Deployment

Fluoroscopy demonstrates relative “deep implantation” trying to avoid the STJ calcific zone and minimize the effects of valve-cage deformity on subannular leaflets.

Video 5

TEE Visualization of the Deep Deployment Depth and Calcific STJ Constraints of Valve Outflow

Video 6

Postdeployment Short-Axis TEE

Mid-esophageal short-axis view demonstrating normal prosthetic valve function with symmetric leaflet motion and no evidence of paravalvular leak.