11.1 CTO, Atherectomy & Alcohol Septal Ablation

11.1 CTO, Atherectomy & Alcohol Septal Ablation

Complex coronary intervention extends beyond routine balloon angioplasty and stent deployment into chronic total occlusions (CTOs), heavily calcified lesions requiring plaque modification, and structural septal reduction for hypertrophic obstructive cardiomyopathy (HOCM). The RCIS must anticipate equipment needs, recognize angiographic patterns, and support wire escalation, atherectomy setup, and alcohol septal ablation (ASA) protocols.

Chronic Total Occlusion (CTO) PCI

A chronic total occlusion is defined angiographically as TIMI flow grade 0 with an estimated occlusion duration of ≥3 months. Unlike acute occlusions, CTOs develop organized fibrocalcific caps, collateral circulation, and negative remodeling that make crossing and recanalization technically demanding. Successful CTO PCI can relieve angina, improve left ventricular function, and serve as a conduit for future bypass grafts.

J-CTO Score and Procedural Planning

The Japanese Multicenter CTO Registry (J-CTO) score estimates procedural difficulty on a 0–5 scale using four angiographic factors, each worth 1 point when present:

Scores of 0–1 predict high technical success; scores of 4–5 indicate very difficult lesions requiring experienced operators, dual injection, and specialized hardware. The RCIS prepares microcatheters (Finecross, Corsair Pro), dual-lumen microcatheters (Crusade), and a staged wire escalation tray before the case begins.

Antegrade CTO Techniques

The antegrade approach advances a guidewire from the proximal cap toward the distal true lumen. Wire escalation follows a deliberate sequence:

1. Soft polymer wires (Fielder XT, Fielder XT-A, Pilot 50) probe for microchannels and soft caps.
2. Intermediate tapered wires (Gaia First, Gaia Second, Gaia Third) provide controllable penetration with composite-core design.
3. Stiff tapered wires (Confianza Pro, Conquest Pro, Hornet 10/14) penetrate calcified or fibrotic caps when softer wires fail.

Tip load is matched to cap morphology: tapered caps favor polymer wires; blunt, calcified caps require stiff tapered wires. Once the wire enters the distal true lumen, dual injection (simultaneous contrast into donor and recipient territories) confirms position before balloon dilatation. IVUS or OCT can verify wire location in ambiguous cases.

Retrograde CTO Techniques

When antegrade crossing fails, the retrograde approach uses collateral channels—preferably septal collaterals (lower perforation risk) over epicardial collaterals—from a donor artery to reach the distal recipient vessel. The wire is then advanced retrograde through the occlusion.

Key retrograde subtechniques include:

• CART (Controlled Antegrade and Retrograde subintimal Tracking): Antegrade balloon creates a subintimal dissection plane that the retrograde wire enters.
• Reverse CART: Retrograde balloon creates the dissection plane for the antegrade wire.
• Knuckle wire technique: A looped, polymer-jacketed wire (e.g., Fielder XT-R) navigates the subintimal space without penetrating the vessel wall.

Wire externalization (RG3, R250) creates a continuous rail through the occlusion for antegrade balloon and stent delivery. Retrograde cases require additional heparin monitoring, longer ACT targets, and heightened vigilance for coronary perforation and tamponade.

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Coronary Atherectomy

When heavily calcified plaque prevents balloon expansion or stent delivery despite high-pressure non-compliant balloon inflation, plaque modification with atherectomy is indicated. Atherectomy physically ablates or cuts plaque to create a larger lumen for subsequent stenting.

Rotational Atherectomy (Rotablator) Setup and Technique

The Rotablator system consists of a console, advancer, and diamond-coated burr connected to a helical drive shaft. The RCIS responsibilities include:

1. Flush preparation: Connect pressurized heparinized saline (typically 5000 U heparin per 500 mL saline) to the advancer flush port. Continuous flush cools the burr and prevents thrombus formation on the drive shaft.
2. Burr sizing: Select a burr ≤0.6 times the reference vessel diameter (e.g., 1.5 mm burr for a 2.5 mm vessel).
3. Pecking technique: Advance the spinning burr in short, gentle pecks rather than sustained forward pressure. Avoid deceleration >5000 rpm during engagement, which indicates excessive pressure and risks slow-flow/no-reflow from microvascular debris and heat injury.
4. Speed settings: Standard speed is 140,000–160,000 rpm (up to 180,000 rpm for larger burrs). The console displays real-time rpm; audible pitch changes signal deceleration.
5. Post-rotablation: Administer intracoronary nitroglycerin and verapamil/nicardipine if slow-flow develops. Follow with low-pressure balloon predilatation and stent deployment.

Complications include slow-flow/no-reflow, coronary dissection, perforation (especially with oversized burrs), and burr entrapment. Temporary pacing should be available because rotablation can provoke transient bradycardia and AV block from microvascular debris embolization to the conduction system.

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Alcohol Septal Ablation (ASA) for HOCM

Alcohol septal ablation is a percutaneous alternative to surgical septal myectomy for symptomatic hypertrophic obstructive cardiomyopathy (HOCM) with a resting or provoked left ventricular outflow tract (LVOT) gradient ≥50 mmHg despite optimal medical therapy.

Patient Selection and Pre-Procedure Requirements

Candidates must have suitable septal perforator anatomy: a first or major septal perforator branch of the left anterior descending (LAD) artery that supplies the hypertrophied basal septum segment responsible for LVOT obstruction. Contraindications include unsuitable septal anatomy, significant mitral regurgitation requiring surgical repair, and prior septal infarction in the target territory.

Pre-procedure requirements include:

• Temporary pacing wire placement in the right ventricle (high incidence of transient complete heart block).
• Echocardiographic assessment of septal thickness, LVOT gradient, and mitral valve anatomy.
• Identification of the target septal perforator with contrast injection and echocardiographic correlation.

Procedural Steps

1. Septal perforator cannulation: Advance a guidewire into the target septal perforator branch arising from the LAD.
2. Temporary balloon occlusion: Inflate a small over-the-wire balloon (typically 2.0–2.5 mm) within the septal branch to prevent alcohol reflux into the LAD.
3. Ethanol injection: Inject 0.5–2.0 mL of absolute (dehydrated) ethanol through the central lumen while the balloon is inflated. The ethanol produces a controlled localized septal infarction, thinning the basal septum over weeks to months.
4. Monitoring: Continuous hemodynamic monitoring for LVOT gradient reduction, arrhythmias, and conduction block. Post-procedure echocardiography confirms gradient improvement.

Post-Procedure Considerations

Patients typically develop transient right bundle branch block (RBBB) from septal infarction (surgical myectomy more commonly causes left bundle branch block). Complete heart block requiring permanent pacemaker implantation occurs in approximately 5–10% of cases. Other complications include ventricular arrhythmias, coronary dissection of the LAD or septal branch, and non-target myocardial infarction from ethanol reflux.