5.1 Cardiac Catheterization, Percutaneous Interventions & Structural Heart

5.1 Cardiac Catheterization, Percutaneous Interventions & Structural Heart

[!NOTE] ANCC Blueprint Context: Domain II (Planning and Implementation) tests the cardiovascular nurse's proficiency in preparing patients for invasive percutaneous procedures, executing post-intervention vascular access care, identifying early signs of vascular compromise or contrast nephropathy, and managing structural heart therapies such as TAVR and TEER.

Invasive cardiac catheterization and percutaneous coronary interventions (PCI) represent the cornerstone of coronary artery disease diagnosis and revascularization. Safe care mandates mastery of procedural mechanics, access-site hemostasis protocols, and immediate recognition of life-threatening post-procedural complications.

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Diagnostic Cardiac Catheterization: Left vs. Right Heart Catheterization

Cardiac catheterization is classified into left heart catheterization (arterial system) and right heart catheterization (venous system), each addressing distinct diagnostic objectives.

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Percutaneous Coronary Interventions: Balloons and Stents

Percutaneous coronary intervention (PCI) restores lumen patency in stenotic coronary arteries:

1. Plain Old Balloon Angioplasty (POBA): Involves inflating a non-compliant or semi-compliant balloon across a plaque to fracture the atheroma and stretch the media. Used primarily for vessel pre-dilation, plaque preparation, or in small branch vessels where stenting is impractical. Alone, POBA carries a 30% to 50% risk of acute recoil and restenosis.
2. Bare-Metal Stents (BMS): Expandable balloon-mounted metallic scaffolds (stainless steel or cobalt-chromium) that permanently bridge the lumen. Although eliminating mechanical elastic recoil, BMS triggers extensive vascular smooth muscle proliferation (neointimal hyperplasia), resulting in a 20% to 30% rate of in-stent restenosis (ISR) within 6 months.
3. Drug-Eluting Stents (DES): Contemporary standard of care. Metallic or bioresorbable polymer backbones coated with cytostatic or antiproliferative agents (such as everolimus, zotarolimus, or sirolimus). These agents halt vascular smooth muscle cell replication, reducing in-stent restenosis rates to below 5% to 10%.

Dual Antiplatelet Therapy (DAPT) Requirements

Stent endothelialization requires weeks to months. Uncovered metallic struts exposed to high-shear intracoronary blood flow create a potent nidus for acute platelet activation and fatal in-stent thrombosis.

• Standard DAPT Regimen: Aspirin (81 mg daily indefinitely) paired with an oral $P2Y_{12}$ receptor inhibitor:
  • Ticagrelor (Brilinta): 90 mg BID (preferred in ACS; fast onset, reversible).
  • Prasugrel (Effient): 10 mg daily (contraindicated in patients with prior TIA or stroke; caution if age $\ge 75$ or weight $<60$ kg).
  • Clopidogrel (Plavix): 75 mg daily (prodrug; requires hepatic CYP2C19 activation; chosen in elective PCI or high bleeding risk).
• Mandatory Duration: Minimum of 6 to 12 months following DES implantation for acute coronary syndrome. Premature discontinuation within the first 30 to 90 days carries an exceptionally high risk of catastrophic stent thrombosis presenting as sudden death or transmural STEMI.

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Vascular Access Management: Transradial vs. Transfemoral

Per AHA/ACC guidelines, transradial access is the first-line standard of care for diagnostic catheterization and PCI due to superior clinical outcomes.

Radial Compression Devices & Patent Hemostasis

Radial compression bands (such as the TR Band) apply localized pneumatic pressure over the radial puncture site:

• Patent Hemostasis Protocol: The primary objective is achieving hemostasis while maintaining continuous antegrade radial blood flow. Compressing the artery to complete occlusion dramatically elevates the risk of permanent Radial Artery Occlusion (RAO).
• Verification Technique: Verify flow using the Barbeau test or plethysmography: place a pulse oximeter probe on the ipsilateral thumb and compress the ulnar artery. A continuous pulsatile plethysmographic waveform confirms antegrade radial flow through the banded site.
• Deflation Schedule: After an initial mandatory hold time (typically 2 hours for diagnostic cath, 3 to 4 hours for PCI), release 1 to 2 mL of air every 15 to 30 minutes while inspecting for bleeding or hematoma. If bleeding recurs, immediately re-inflate with 1 to 2 mL of air, hold for 30 minutes, and re-attempt weaning.

Femoral Manual Compression & Vascular Closure Devices (VCDs)

• Manual Compression: Following sheath removal in the absence of a closure device, apply firm continuous digital pressure 1 to 2 cm proximal to the skin puncture site (directly overlying the common femoral arteriotomy over the femoral head) for 20 to 30 minutes. The patient must remain on strict supine bed rest with the affected leg immobilized straight for 4 to 6 hours.
• Vascular Closure Devices (VCDs):
  • Angio-Seal: Deploys a bioabsorbable polymer anchor inside the vessel, an external collagen sponge against the adventitia, and a cinch suture. Bed rest reduced to 2 hours. Clinical Pearl: Re-puncture of the same femoral artery is contraindicated for 90 days.
  • Perclose ProGlide: Suture-mediated active closure device deploying needles and polyglycolic acid sutures directly across the arteriotomy. Bed rest reduced to 1 to 2 hours.
  • Mynx: Passive sealant deploying an extravascular PEG (polyethylene glycol) hydrogel that expands upon contact with fluid, sealing the tract without intravascular components.

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Recognition and Management of Post-Catheterization Complications

Cardiovascular nurses must execute rapid physical assessments of the access extremity, groin, and systemic hemodynamics.

[ Post-Cath Groin Deterioration ]
       │
       ├─> Local Firmness / Swelling / Ecchymosis ──────> Access Site Hematoma (Manual compression)
       ├─> Pulsatile Mass + Systolic Bruit ─────────────> Pseudoaneurysm (Ultrasound thrombin injection)
       ├─> Continuous Machinery Bruit + Thrill ─────────> AV Fistula (Vascular surgical consult)
       └─> Flank/Back Pain + Hypotension + Tachycardia ──> Retroperitoneal Hemorrhage (Emergent CT / Resuscitate)

1. Retroperitoneal Hemorrhage (RPH)

• Pathophysiology: Occurs when the femoral arterial puncture is placed above the inguinal ligament into the high common femoral or external iliac artery. Blood tracks freely into the non-distensible retroperitoneal space with no external hematoma visible in the groin.
• Cardinal Manifestations: Severe, unyielding lower back or ipsilateral flank pain, diaphoresis, unexplained resting sinus tachycardia, profound refractory hypotension, and a rapid drop in hemoglobin/hematocrit.
• Nursing Actions: Immediately palpate the femoral pulse and apply firm manual pressure cephalad to the puncture site; administer rapid IV isotonic crystalloid boluses; draw emergent type and cross-match for packed red blood cells (PRBCs); discontinue active antithrombin and antiplatelet infusions (heparin, bivalirudin, glycoprotein IIb/IIIa inhibitors); obtain an emergent non-contrast CT scan of the abdomen and pelvis; and alert interventional cardiology and vascular surgery for endovascular balloon occlusion or open repair.

2. Femoral Pseudoaneurysm

• Pathophysiology: Incomplete arteriotomy closure allowing blood to pulsate through a defect ("neck") into adjacent fibromuscular tissue, creating a false, perfused cavity.
• Manifestations: Painful, pulsatile groin mass accompanied by a harsh systolic bruit on auscultation.
• Management: Confirm via duplex Doppler ultrasound demonstrating swirling flow ("yin-yang sign"). Definitive bedside therapy is ultrasound-guided percutaneous thrombin injection into the false lumen, which induces immediate coagulation while sparing the parent artery.

3. Arteriovenous (AV) Fistula

• Pathophysiology: Inadvertent puncture connecting the common femoral artery and adjacent femoral vein, creating an abnormal low-resistance shunt.
• Manifestations: Continuous "machinery-like" thrill on palpation and a continuous bruit on auscultation over the groin; can cause downstream lower extremity venous congestion and edema.
• Management: Monitored conservatively if small; large fistulas causing high-output cardiac failure require surgical or covered-stent repair.

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Contrast-Induced Nephropathy (CIN) Prevention Protocols

Contrast-Associated Acute Kidney Injury (CA-AKI / CIN) is defined as an absolute rise in serum creatinine $\ge 0.5$ mg/dL or a relative increase $\ge 25%$ from baseline occurring 48 to 72 hours after intravascular iodinated radiocontrast administration.

High-Risk Patient Profiles

• Pre-existing Chronic Kidney Disease (baseline $\text{eGFR} <60\text{ mL/min/1.73m}^2$ or serum creatinine $>1.5\text{ mg/dL}$).
• Diabetic nephropathy (synergistic risk multiplier).
• Dehydration, intravascular volume depletion, or congestive heart failure.
• Advanced age ($>75$ years), multiple myeloma, and concurrent nephrotoxic medications (NSAIDs, aminoglycosides, vancomycin, ACE inhibitors/ARBs).

Guideline-Directed Prevention Strategies

1. Isotonic Hydration: The single most effective validated prophylactic intervention. Administer isotonic $0.9%$ Normal Saline at 1.0 to 1.5 mL/kg/hr for 3 to 12 hours pre-procedure and 6 to 12 hours post-procedure (adjusted downward in severe LV systolic dysfunction to prevent volume overload).
2. Contrast Volume Minimization: Maintain a ratio of total contrast volume (mL) to estimated glomerular filtration rate (eGFR) of $<3.7$. Use low-osmolar or iso-osmolar non-ionic contrast.
3. Metformin Protocol: Metformin does not cause nephropathy; however, if contrast induces acute kidney injury, metformin accumulates, inhibiting hepatic gluconeogenesis and mitochondrial lactate clearance, precipitating life-threatening metformin-associated lactic acidosis. Withhold metformin on the morning of the procedure and maintain the hold for 48 hours post-procedure. Recheck serum creatinine at 48 hours; resume metformin only after stable renal function is confirmed.

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Transcatheter Structural Heart Interventions: TAVR & TEER

Transcatheter structural technologies provide minimally invasive alternatives for patients with severe valvular disease who present with high or prohibitive surgical risk.

Transcatheter Aortic Valve Replacement (TAVR)

• Indication: Severe symptomatic native aortic valve stenosis (aortic valve area $<1.0\text{ cm}^2$, mean gradient $>40\text{ mmHg}$, or peak velocity $>4.0\text{ m/s}$) across high, intermediate, and select low surgical risk profiles.
• Procedural Mechanics: A balloon-expandable (Edwards SAPIEN) or self-expanding (Medtronic CoreValve/Evolut) bioprosthetic valve is advanced retrograde across the native calcified aortic valve via transfemoral access (or transaxillary/subclavian if iliofemoral vessels are prohibitive).
• High-Yield Post-TAVR Complications:
  1. Conduction Disturbances & Complete Heart Block: The aortic annulus lies immediately adjacent to the AV node and bundle of His within the membranous septum. Radial expansion of the prosthetic frame exerts direct mechanical pressure and hematoma on the conduction tissue. Nurses must monitor continuous telemetry for new-onset Left Bundle Branch Block (LBBB), PR interval prolongation, or high-grade AV block. Approximately 10% to 15% of patients require permanent pacemaker (PPM) implantation (higher incidence with self-expanding valves).
  2. Ischemic Stroke: Embolization of calcific annular debris during balloon valvuloplasty or valve seating. Dual-filter cerebral embolic protection devices (Sentinel) are deployed in the brachiocephalic and left carotid arteries during the procedure to capture debris.
  3. Paravalvular Leak (PVL): Incomplete circumferential sealing between the prosthetic valve skirt and irregular native calcification causes aortic regurgitation jets, predisposing to mechanical hemolysis and heart failure.

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

• Indication: Severe symptomatic primary (degenerative) mitral regurgitation in patients at prohibitive surgical risk, or secondary (functional) mitral regurgitation in optimized heart failure with reduced ejection fraction (HFrEF) meeting COAPT trial criteria.
• Procedural Mechanics: Accessed via the femoral vein into the right atrium, followed by a fluoroscopy- and transesophageal echocardiography (TEE)-guided transseptal puncture across the fossa ovalis into the left atrium. The delivery system positions a mechanical clip (MitraClip) that grasps the free edges of the anterior ($A_2$) and posterior ($P_2$) mitral valve leaflets, creating a permanent double-orifice mitral valve.
• Nursing Surveillance: Monitor for post-transseptal puncture complications including iatrogenic atrial septal defect (ASD) with right-to-left shunting, pericardial effusion, and acute cardiac tamponade. Assess for elevated transmitral gradients to ensure leaflet approximation has not induced functional mitral stenosis.