15.1 Nonvalvular Structural Therapies

15.1 Nonvalvular Structural Therapies

Quick Answer: Nonvalvular structural cath lab work centers on closing congenital shunts (ASD, VSD, PDA), PFO closure after cryptogenic stroke, and LAA occlusion (Watchman-class devices) for non-valvular AF when anticoagulation is contraindicated or declined. RCIS staff prepare ICE/TEE imaging, transseptal access, device inventory, ACT targets, and complication recognition—not independent patient selection.

Structural heart cases that do not involve native or prosthetic valve replacement still demand the same cath lab discipline as PCI: sterile technique, radiation ALARA, hemodynamic vigilance, and crisp team communication. CCI's Interventional domain expects you to anticipate equipment, support imaging guidance, and recognize procedural complications for septal defect closure and left atrial appendage (LAA) occlusion. These therapies sit under Domain C, tasks 13–14 in the RCIS matrix: device-based structural interventions beyond routine coronary work.

Congenital and Acquired Septal Defects

Atrial Septal Defect (ASD)

An ASD is a persistent opening in the interatrial septum, most commonly secundum type amenable to percutaneous closure. Hemodynamically significant ASDs produce a left-to-right shunt, right heart volume overload, and—if uncorrected—late pulmonary hypertension or arrhythmia.

Diagnostic clues RCIS should recognize:

• Fixed split S2 on auscultation (exam vignette context).
• Right heart catheterization: elevated Qp:Qs, elevated PA pressures if long-standing.
• Oximetry step-up at the RA level ≥7% compared with superior vena cava saturation localizes an atrial-level shunt (ASD or partial anomalous pulmonary venous return).

Percutaneous closure: Device families (Amplatzer-type septal occluders and equivalents) are delivered via femoral venous access through the defect under TEE and/or ICE guidance. The RCIS role includes verifying device size matrices on the table, maintaining heparin per lab protocol (often targeting ACT 250–300 seconds during transseptal work—follow your institution's order set), and ensuring the ICE catheter is prepped when TEE is not used.

Closure thresholds (guideline context, not RCIS to decide): Significant shunt with Qp:Qs > 1.5:1, right heart enlargement, or symptoms. Exam items may test contraindications: unrepaired primum ASD requiring surgery, deficient rims (<5 mm) preventing device seating, active endocarditis, or prohibitive pulmonary vascular disease.

Patent Foramen Ovale (PFO)

A PFO is a flap-like potential channel between atria, not a true congenital defect in the same sense as ASD. It can permit paradoxical embolism. Percutaneous PFO closure is considered after cryptogenic stroke in selected patients when alternative stroke etiologies are excluded.

RCIS differences from ASD cases:

• Often younger patients; stroke work-up documentation appears in the chart.
• Device selection overlaps with ASD occluders but sizing emphasizes tunnel length and aneurysmal septum features (imaging-dependent).
• Post-closure DAPT duration varies by device IFU and operator plan—know whether your lab uses aspirin + clopidogrel for 1–6 months post procedure as a default teaching point.

Ventricular Septal Defect (VSD)

VSD percutaneous closure targets restrictive, muscular, or post-infarction defects when surgical risk is high. Membranous VSDs near the aortic valve carry higher complication risk and are often surgical.

Oximetry localization: Step-up at the RV level ≥5% suggests ventricular-level shunt.

Device delivery crosses the ventricular septum from venous to arterial side (or vice versa depending on approach). RCIS must anticipate longer sheaths, snares, and possible temporary arterial access for device stability. Complications include complete heart block (especially membranous location), aortic regurgitation from device impingement, and embolization—have retrieval snares and surgical backup confirmed in the timeout.

Patent Ductus Arteriosus (PDA)

The PDA connects pulmonary artery to aorta. In adults, closure treats left-to-right shunt with Qp:Qs > 1.5 or clinical sequelae. Oximetry step-up at the PA level ≥5% localizes ductal shunt.

Devices include Amplatzer duct occluders and coils for small PDAs. Access is typically femoral venous and/or arterial depending on approach (antegrade venous vs retrograde arterial). RCIS prepares coils of multiple sizes, verifies compatibility with delivery catheters, and monitors for hemolysis or CoA if oversized devices protrude into the aorta.

Shunt Quantification Essentials

The Fick equation and thermodilution cardiac output methods underpin Qp:Qs calculations. You may not compute on exam day in the lab, but RCIS items expect you to know that elevated Qp:Qs with chamber enlargement supports closure candidacy.

Left Atrial Appendage Occlusion (LAAO)

Indication and Device Classes

Non-valvular atrial fibrillation carries stroke risk largely from thrombus in the left atrial appendage (LAA)—source of >90% of cardioembolic thrombi in NVAF. When long-term oral anticoagulation (OAC) is contraindicated or refused despite elevated CHA₂DS₂-VASc risk, LAA occlusion with Watchman-class (Boston Scientific Watchman/FLX) or Amulet-class (Abbott) devices is an alternative.

RCIS must not confuse LAAO with valve therapy:

• Watchman/Amulet → LAA occlusion for AF stroke prevention.
• MitraClip → mitral valve repair (covered in Section 15.2).

Procedural Flow

1. Transseptal puncture from femoral vein into the left atrium—guided by TEE and/or ICE (RCIS: verify ICE catheter, flush transseptal needle, prepare Brockenbrough kit).
2. Angiography of LAA (often multiple projections) to measure landing zone depth and diameter.
3. Device deployment in the LAA ostium; TEE/ICE pull test confirms stability and seal.
4. Post-implant leak assessment: peri-device leak ≤ 5 mm is commonly acceptable per protocol thresholds—know your lab's echo criteria.

Antithrombotic Protocol (Teaching Framework)

Protocols evolve; exam scenarios often reference:

• Warfarin + aspirin for ~45 days post implant, then OAC discontinued if appendage sealed and clinical plan allows.
• Transition to single antiplatelet (aspirin or clopidogrel) after successful endothelialization window.

Document ACT during transseptal access (many labs target 250–300 s). Reversal agents and protamine availability should match your structural heart cart standard.

Complications to Monitor

Imaging and Radiation Considerations

Structural cases run long fluoroscopy times. Apply ALARA: collimate, use low frame rates when safe, monitor cumulative air kerma and DAP. ICE reduces fluoroscopy dependence for transseptal and LAA sizing—support ICE catheter setup and sterile ICE sheath management.

RCIS Checklist: Nonvalvular Structural Case

• Device serial numbers, sizes, and backup device on field
• TEE/ICE probe availability and qualified operator
• Heparin bolus and ACT machine QC documented
• Closure device inventory for access (ProGlide, Perclose, MANTA for large bore if applicable)
• Blood products and tamponade kit verified
• Post-procedure bed rest and antithrombotic orders understood for handoff

Nonvalvular structural therapy questions on RCIS reward anatomy localization, device-indication matching, and complication preparedness—the same triad that keeps real LAA and septal closure days safe.