Catheter Ablation of the Scar
For a patient with recurrent ventricular tachycardia despite ICD and amiodarone therapy, catheter ablation is the definitive next step. This scenario represents electrical storm or recurrent VT refractory to medical management, which is a Class I indication for urgent catheter ablation. 1
Why Ablation is the Answer
Urgent catheter ablation is specifically recommended (Class I, Level B) for patients presenting with recurrent VT or electrical storm resulting in multiple ICD shocks. 1 The 2015 ESC Guidelines explicitly state that catheter ablation is recommended in patients with recurrent ICD shocks due to sustained VT, particularly when this occurs despite amiodarone therapy. 1
Key Supporting Evidence:
Patients with sustained monomorphic VT and an ICD who are receiving multiple shocks not manageable by reprogramming or concomitant drug therapy have a Class I indication for catheter ablation. 1
Catheter ablation can acutely terminate electrical storms and has been shown to decrease the rate of recurrent electrical storm episodes when compared with medical treatment alone. 1
The combination of amiodarone plus beta-blocker reduces ICD shocks, but when this fails, catheter ablation becomes the recommended intervention. 1
Why Not Biventricular Pacing?
Biventricular pacing (CRT) is not indicated for refractory VT management unless the patient separately meets criteria for cardiac resynchronization therapy (heart failure with NYHA class II-III, LVEF ≤35%, and wide QRS with LBBB morphology). 1 CRT is a heart failure therapy that may have some antiarrhythmic effects, but it is not a treatment for electrical storm or recurrent VT refractory to medical therapy.
Clinical Approach to Scar-Related VT Ablation
Pre-Procedural Considerations:
Cardiac MRI should be used to plan and guide the ablation procedure by identifying scar tissue and the substrate for VT. 1
The patient likely has scar-related heart disease (ischemic or non-ischemic cardiomyopathy) as the substrate for recurrent monomorphic VT. 1
Ablation Strategy:
Three-dimensional electro-anatomical mapping systems permit substrate ablation in sinus rhythm without requiring VT induction, which is particularly useful when VT is hemodynamically unstable. 1
Multiple techniques can be employed including scar dechanneling, linear lesion sets, or ablation of local abnormal ventricular activity to achieve scar homogenization. 1
Epicardial mapping and ablation may be required, particularly in patients with dilated cardiomyopathy or ARVC. 1
Expected Outcomes:
Catheter ablation decreases the likelihood of subsequent ICD shocks and prevents recurrent episodes of VT based on prospective randomized multicenter trials. 1
The SMASH-VT trial demonstrated that catheter ablation reduced appropriate ICD shocks from 31% to 9% in patients with ischemic heart disease. 1
Success rates vary: acute success ranges from 41-81% depending on the study, with mid-term freedom from VT in 46-53% of patients. 1
Important Caveats
ICD shocks are associated with higher mortality and impaired quality of life, making prevention of recurrent shocks a critical therapeutic goal. 1 This underscores why ablation is preferred over simply accepting recurrent shocks.
The ICD should remain in place after ablation, as patients who undergo catheter ablation and satisfy eligibility criteria for ICD should maintain their device (Class I recommendation). 1
If catheter ablation fails after being performed by experienced electrophysiologists, surgical ablation guided by preoperative and intraoperative electrophysiological mapping at an experienced center is recommended (Class I, Level B). 1
Complications of catheter ablation occur in approximately 3% of cases and include damage to coronary vasculature, inadvertent puncture of surrounding organs, left phrenic nerve palsy, or pericardial tamponade. 1