How to use the Astato XS wire for septal ablation in hypertrophic cardiomyopathy (HCM)?

Alcohol Septal Ablation Procedure Using Astato XS Wire for Hypertrophic Cardiomyopathy

Alcohol septal ablation using the Astato XS wire should be performed only by experienced operators in dedicated HCM centers for eligible patients with severe drug-refractory symptoms and LVOT obstruction, particularly when surgery is contraindicated or high-risk due to comorbidities or advanced age. 1

Patient Selection Criteria

Eligible patients for alcohol septal ablation must meet all of the following criteria:

1. Clinical: Severe dyspnea or chest pain (usually NYHA class III or IV) or other exertional symptoms that interfere with daily activities despite optimal medical therapy
2. Hemodynamic: Dynamic LVOT gradient ≥50 mmHg at rest or with physiologic provocation
3. Anatomic: Adequate septal thickness for safe and effective procedure 1

Contraindications

• Age <21 years (absolute contraindication)
• Age <40 years (relative contraindication if myectomy is viable)
• Septal thickness >30 mm (limited effectiveness)
• Concomitant cardiac disease requiring surgical correction
• Asymptomatic patients or those controlled on medical therapy 1

Procedural Technique with Astato XS Wire

Pre-procedure Assessment

• Comprehensive echocardiography to confirm:
  • Location and extent of septal hypertrophy
  • Area of SAM-septal contact
  • Degree of LVOT obstruction
  • Mitral regurgitation

Procedure Steps

1. Access and Catheterization:

   • Obtain femoral arterial access
   • Place temporary pacemaker via femoral venous access (for potential heart block)
   • Perform baseline hemodynamic assessment with LVOT gradient measurement

2. Target Vessel Selection:

   • Cannulate left coronary artery
   • Identify first septal perforator artery that supplies the basal septum at SAM-septal contact point
   • Advance Astato XS wire into the target septal branch

3. Balloon Occlusion and Verification:

   • Advance an over-the-wire balloon into the septal branch
   • Inflate balloon to occlude the vessel
   • Inject contrast through balloon lumen to verify:
     • No extravasation into LAD
     • No collateral supply to papillary muscles or free wall 1

4. Echocardiographic Guidance:

   • Perform intraprocedural myocardial contrast echocardiography by injecting echo contrast through balloon lumen
   • Confirm contrast enhancement limited to target septal area
   • Change target vessel if contrast shows atypical perfusion pattern 2

5. Alcohol Injection:

   • Once target area is confirmed, slowly inject 1-3 mL of 96% ethanol through the balloon lumen
   • Maintain balloon inflation for 5-10 minutes after alcohol injection
   • Monitor ECG continuously for arrhythmias and heart block 1, 3

6. Post-injection Assessment:

   • Measure LVOT gradient immediately after procedure
   • Expect immediate gradient reduction due to stunning effect
   • Further gradient reduction occurs over 3-12 months due to remodeling 1

Post-procedure Management

Immediate Care

• Continuous cardiac monitoring for at least 48-72 hours
• Watch for complete heart block (occurs in approximately 50% temporarily)
• Monitor for ventricular arrhythmias (occur in ~5% during hospitalization)
• Expect post-procedural chest pain for 24 hours
• Monitor CK levels (typically peak at ~780 U/L after 11 hours) 4

Complications and Management

• Permanent heart block: Occurs in 10-20% of patients, requiring permanent pacemaker implantation
• Ventricular arrhythmias: Monitor closely and treat appropriately
• Ventricular septal defect: Rare complication, especially if target septal thickness <15 mm
• Remote myocardial infarction: Can occur if alcohol reaches non-target areas 1

Follow-up Protocol

• Echocardiography at 1,3,6, and 12 months
• Expect progressive LVOT gradient reduction over 3-12 months
• Clinical assessment of symptom improvement
• Exercise testing to evaluate functional capacity improvement 5

Expected Outcomes

• Reduction in LVOT gradient by 70-90% in successful cases
• Improvement in NYHA functional class by at least one class in 88% of patients
• Reduction in septal thickness from baseline
• Improvement in exercise capacity and quality of life 3, 4

Alternative Approaches

For patients with unfavorable anatomy for alcohol septal ablation, radiofrequency catheter ablation (RFCA) of the hypertrophied septum may be considered as an emerging alternative technique, though this is not yet included in guidelines 6.

Important Caveats

• Success depends on septal artery anatomy, which may not supply the target area in 20-25% of patients
• Operator experience is crucial - should be performed by operators with at least 20 procedures or in centers with cumulative volume of at least 50 procedures
• Target mortality rate should be ≤1% and major complication rate ≤3% 1
• Long-term risk of ventricular arrhythmias remains a concern due to the myocardial scar created