7.3 Structural Heart Interventions: TAVR, MitraClip, Pericardiocentesis

Transcatheter Aortic Valve Replacement (TAVR)

Transcatheter Aortic Valve Replacement (TAVR) has revolutionized the management of severe, symptomatic aortic stenosis. The procedure involves percutaneous deployment of a collapsible bioprosthetic aortic valve—either balloon-expandable (e.g., Edwards SAPIEN) or self-expanding (e.g., Medtronic Evolut)—within the diseased native aortic valve under fluoroscopic and echocardiographic guidance.

Vascular Access Routes

• Transfemoral (TF) Access: The gold-standard primary approach (>90% of cases). Utilizes large-bore arterial sheaths (14 to 18 Fr) placed in the common femoral artery. Requires adequate luminal diameter (≥ 5.0–5.5 mm), minimal calcification, and absence of severe tortuosity.
• Alternative Access Routes: Utilized when femoral arterial anatomy is inadequate due to severe peripheral arterial disease:
  • Transaxillary / Subclavian Access: Percutaneous or surgical cutdown into the subclavian artery.
  • Transapical (TA) Access: Surgical mini-thoracotomy with direct puncture of the LV apex (associated with higher morbidity).
  • Transaortic (TAo) or Transcarotid Access: Surgical access via mini-sternotomy or carotid cutdown.

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Conduction Complications, Paravalvular Leak & Vascular Access Monitoring

Conduction System Injuries & Permanent Pacemaker Risk

The anatomical location of the aortic valve annulus creates an inherent vulnerability: the atrioventricular (AV) node and the bundle of His / left bundle branch traverse the membranous septum directly underneath the native aortic cusps. Radial compression exerted by the expanded bioprosthetic frame causes mechanical trauma, tissue edema, or hematoma formation in the conduction system.

Aortic Annulus Frame Radial Expansion ---> Mechanical Trauma to Membranous Septum
  └──> AV Node / Left Bundle Branch Compression ---> New LBBB / High-Degree AV Block ---> Permanent Pacemaker (PPM)

• High-Risk ECG Alterations: New-onset Left Bundle Branch Block (LBBB), 1st degree AV block paired with pre-existing RBBB, or complete high-degree AV block.
• Pacemaker Requirement Rates: Occurs in 5–15% of balloon-expandable valves and 15–25% of self-expanding valves (due to deeper nitinol frame expansion into the left ventricular outflow tract [LVOT]).
• Nursing Telemetry Standard: Continuous 12-lead ECG monitoring and telemetry tracking for at least 48 to 72 hours post-TAVR, with immediate availability of transcutaneous and temporary transvenous pacing.

Paravalvular Leak (PVL) Assessment

Paravalvular regurgitation occurs when incomplete sealing exists between the bioprosthetic valve frame and the asymmetric, heavily calcified native aortic annulus.

• Diagnostic Assessment: Transthoracic/transesophageal Doppler echocardiography measuring jet width and circumferential extent.
• Invasive Hemodynamic Index: Aortic Regurgitation Index (ARI) calculated during catheterization: $\text{ARI} = \left[ \frac{\text{DBP} - \text{LVEDP}}{\text{SBP}} \right] \times 100$ An ARI < 25 indicates hemodynamically significant PVL, which correlates directly with accelerated hemolysis and increased 1-year mortality.

Large-Bore Vascular Access Bleeding

Post-procedural nursing monitoring must focus on large-bore femoral puncture sites:

• Retroperitoneal Hemorrhage: Suspected when the patient exhibits unexplained hypotension, tachycardia, back/flank pain, or ipsilateral femoral neuropathy without visible groin bleeding. Obtain STAT abdominal/pelvic CT.
• Groin Complications: Hematoma formation, pseudoaneurysm (pulsatile mass with audible bruit), and acute arterial thrombosis/limb ischemia (loss of pedal pulses).

Transcatheter Edge-to-Edge Repair (MitraClip / TEER)

Transcatheter Edge-to-Edge Repair (TEER) using the MitraClip system is indicated for severe symptomatic primary (degenerative) or secondary (functional) mitral regurgitation in patients determined to be at high surgical risk.

Transeptal Puncture & Procedural Steps

1. Femoral venous access is obtained, advancing a steerable guide catheter into the right atrium.
2. Transeptal Puncture: Under real-time transesophageal echocardiography (TEE) and fluoroscopy, a needle punctures the interatrial septum across the fossa ovalis to enter the left atrium.
3. The clip delivery system is maneuvered into the left ventricle, aligning the clip perpendicular to the mitral coaptation line. The mechanical arms grasp the anterior and posterior mitral valve leaflets together (creating a tissue bridge and a double-orifice mitral valve).

Transeptal Puncture (RA ---> LA) ---> Mitral Valve Alignment ---> Grasp Anterior + Posterior Leaflets ---> Double-Orifice MV

Left Atrial Pressure (LAP) Monitoring & Waveform Signatures

Direct invasive left atrial pressure monitoring (or PCWP tracing) evaluates clip efficacy in real time:

• Pre-Clipping Waveform: Characterized by a massive, prominent v-wave during late systole, created by regurgitant blood jetting backward into the non-compliant left atrium.
• Post-Clipping Target: Successful clip placement produces an immediate, dramatic reduction in v-wave amplitude and a drop in mean LA pressure.
• Mitral Gradient Safety Limit: Post-procedure mean mitral valve pressure gradient must remain < 5 mmHg. A mean gradient ≥ 5 mmHg indicates iatrogenic mitral stenosis, requiring clip adjustment prior to release.

Post-Procedure Nursing Management

• Transeptal Site Monitoring: Monitor for an iatrogenic Atrial Septal Defect (ASD) with persistent left-to-right shunting, and monitor for pericardial effusion/tamponade resulting from accidental puncture of the LA free wall during transeptal access.
• Post-Sheath Removal Care: Enforce flat bedrest for 4 to 6 hours post-venous sheath removal, and monitor telemetry for atrial fibrillation or supraventricular arrhythmias induced by atrial manipulation.

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Pericardiocentesis & Post-Drainage Pulmonary Edema

Emergency pericardiocentesis is performed to evacuate fluid from the pericardial sac in patients presenting with cardiac tamponade (characterized by Beck's triad: hypotension, muffled heart sounds, and elevated CVP/jugular venous distension; along with pulsus paradoxus >10 mmHg).

Guidance & Catheter Technique

• Performed under real-time echocardiographic or fluoroscopic guidance.
• Subxiphoid Approach: An 18-gauge spinal needle is inserted between the xiphoid process and left costal margin at a 30–45 degree angle, aiming toward the left shoulder. Alternatively, an apical approach is utilized.
• A soft-tip guidewire is advanced, followed by a multi-holed pigtail drainage catheter secured to the skin.

Drainage Protocol & Re-accumulation Tracking

• Connect the pigtail catheter to a closed gravity drainage bag.
• Drainage Limit Rule: Avoid rapidly evacuating more than 500 to 1000 mL of pericardial fluid in a single initial bolus.
• Catheter Maintenance: Record drainage volume, color (serous, sanguineous, purulent), and consistency every hour. The catheter is removed when 24-hour output drops below <25–50 mL.
• Re-accumulation Monitoring: Sudden cessation of drainage accompanied by recurrent hypotension, surging CVP, or pulsus paradoxus indicates catheter occlusion by clot/fibrin or recurrent loculated tamponade.

Post-Drainage Pulmonary Edema (Pericardial Decompression Syndrome)

Post-pericardiocentesis pulmonary edema is a rare, life-threatening paradoxical complication that occurs immediately or hours after rapid drainage of a large, chronic pericardial effusion.

• Pathophysiological Cascade:
  1. Chronic pericardial tamponade suppresses both right and left ventricular end-diastolic volumes.
  2. Evacuating the pericardial fluid suddenly removes external compressive forces. The thin-walled Right Ventricle recovers instantly, leading to a massive surge in RV venous return and RV stroke volume.
  3. However, the thicker, non-compliant Left Ventricle remains transiently stunned and incapable of handling the sudden surge in blood volume returning from the lungs.
  4. Blood backs up rapidly from the stunned LV into the left atrium and pulmonary capillaries, causing acute severe pulmonary capillary hypertension and fulminant cardiogenic pulmonary edema.
• Prevention & Nursing Care: Limit initial pericardial fluid withdrawal to <500 mL, clamping the catheter if necessary to allow gradual hemodynamic re-equilibration. If edema develops, provide mechanical ventilation with PEEP, judicious inotropic support, and diuretics.