Abstract Body (Do not enter title and authors here): Introduction/Background
Retrograde aortic valve crossing is a fundamental step in transcatheter aortic valve replacement (TAVR). With the expansion of TAVR programs, rare but challenging cases of failure to cross the valve may arise. Alternate access routes, while helpful, may still prove ineffective in select anatomies or re-operative valves.

Research Question
What are the alternative strategies when retrograde crossing of the aortic valve fails during TAVR, and can a transseptal approach provide a viable solution in anatomically complex or previously operated patients?

Goals/Aims
To describe a case of bioprosthetic valve-in-valve TAVR complicated by inability to cross the aortic valve via both transfemoral and transcarotid retrograde approaches, requiring an unconventional transseptal antegrade solution.

Case Presentation
A 73-year-old male with prior type A aortic dissection repair and a 27 mm bioprosthetic aortic valve (Magna) presented with progressive dyspnea. Echo revealed severe valve stenosis (mean gradient 40 mmHg, AVA 0.6 cm, EF 55–60%). After surgical turndown, valve-in-valve TAVR was pursued. Despite multiple attempts by three experienced operators, retrograde valve crossing failed via transfemoral and left carotid routes, even with a stiff wire support. A transseptal puncture was then performed under TEE and fluoroscopic guidance using the VersaCross system. A balloon catheter and wire were passed antegrade from the left atrium through the left ventricle and across the aortic valve into the descending aorta. The wire was snared retrogradely via the carotid sheath, establishing rail access. This enabled retrograde valve crossing and delivery of a 26 mm Sapien Resilia valve.

Management/Outcome
The valve was deployed successfully after balloon valvuloplasty under rapid pacing. TEE confirmed optimal position with a mean post-deployment gradient of 4 mmHg and no paravalvular leak. The patient remained stable and experienced no procedural complications.

Conclusion
Although rare, failure to cross the aortic valve retrogradely can occur, particularly in patients with prior complex aortic surgery. When standard retrograde and alternate access routes fail, a transseptal antegrade approach may offer a safe and effective bailout strategy. Familiarity with this technique can be critical for heart teams managing complex valve-in-valve scenarios in high-risk patients.