Radio frequency ablation for VT – A cost-effective tool to combat SCD in developing countries

Abstract

The primary focus of ventricular tachycardia (VT) management is the assessment of subsequent risk of sudden death and its prevention, followed by management of symptomatic arrhythmias. Antiarrhythmic drugs usually do not provide sufficient protection from sudden death, but do have a role in reducing arrhythmias that cause symptoms. Role of catheter ablation for the management of VT comes in various clinical settings. Some patients might not need ICDs at all. Idiopathic VT generally has a benign prognosis and in the absence of structural heart disease, symptomatic patients can undergo stand-alone ablation without need for an ICD. Catheter ablation is a reasonable first-line therapy for many symptomatic idiopathic ventricular tachycardia.1 Patients with polymorphic VT and VF can have a triggering PVC originating from Purkinje fibers or from the right ventricular outflow. Perhaps those patients can have an excellent prognosis with focal catheter ablation and can be saved from the financial burden of ICD. It is generally recognized that ablation of VT in the setting of structural heart disease is more difficult than ablation of idiopathic VT. In patients with structural heart disease, adequate tissue ablation is often difficult to achieve due to the presence of relatively large re-entrant circuits that they may be located deep in the myocardium and patients have multiple re-entrant circuits, which further complicate the procedure. Catheter ablation of VT in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy was shown to be associated with high acute procedural success and good intermediate-term outcomes with the use of non-contact electro anatomical mapping systems to guide the ablation.2 Better understanding of arrhythmia mechanism and demonstration of cardiac anatomy from use of electro anatomic mapping systems, intracardiac echocardiography, and pre acquired MRI or CT images incorporated into mapping systems are improving ablation therapy. Patients with a substantial risk of sudden death usually need an ICD. ICDs effectively treat most episodes of ventricular tachycardia or ventricular fibrillation and decrease mortality in patients who are at high risk of sudden cardiac death but they also have inherent risks and limitations.3 Approximately 20% of patients in primary prevention and 45% of patients in secondary prevention receive an appropriate ICD intervention within the 2 years following ICD implantation.4–6 Although ICDs have been shown to improve survival when placed for primary or secondary prevention in the presence of structural heart disease, ICDs are not a cure for VT and do not prevent recurrence of arrhythmias. Catheter ablation of ventricular arrhythmias plays a big role in some patients with ICD who are having recurrent shocks and may even be curative for some patients. Ablation can be life saving for patients with very frequent or incessant ventricular tachycardia. Electrical storm has been defined as three or more separate episodes of VT within a 24 h period and has been associated with increased mortality in patients with ICDs and may affect 4% and 20% of the patients in the primary and secondary prevention, respectively.7,8 These are usually scar-related re-entrant ventricular tachycardias that can cause hemodynamic collapse, which prevents extensive mapping during ventricular tachycardia. To avoid hemodynamic compromise, substrate mapping during stable sinus rhythm is often used to identify the area of scar and probable arrhythmia origin from electrogram characteristics. In patients presenting with electrical storm, catheter ablation may serve as the only viable treatment option if antiarrhythmic therapy fails. Now the question is whether catheter ablation can eliminate the need for an ICD? Cost of catheter ablation is much less than the cost of ICD and in a developing country like India, cost-effectiveness is extremely relevant. To date, results of two randomized prospective multicentre studies have been published in patients with ischemic cardiomyopathy and VT undergoing prophylactic catheter ablation to prevent further VT. The SMASH-VT study9 assessed the role of catheter ablation in 128 patients (64 patients in each group) with previous myocardial infarction and reduced LV ejection fraction undergoing ICD implantation for secondary prevention of sudden cardiac death. None of the patients received Class I or III antiarrhythmic drug therapy. The control arm underwent ICD implantation only. Importantly, catheter ablation was performed utilizing a substrate-guided approach. During an average follow-up period of 22.5 ± 5.5 months, there was a significant decrease in appropriate ICD therapy in the ablation group compared with the control arm (12 vs. 33%, p = 0.007). In addition, the number of appropriate shock deliveries was reduced and there was a trend to a reduction in the number of patients with electrical storm. The number of patients that needed to be treated with ablation (NNT) to avoid 1 appropriate ICD intervention was 5, resulting in a total of 200 appropriate ICD interventions prevented every 1000 patients treated with catheter ablation. The other multicentre VTACH study,10 assessed the role of VT ablation in patients with prior myocardial infarction, reduced EF ≤ 50%, and haemodynamically stable VT. One hundred and ten patients were prospectively randomized to ICD only or VT ablation at the time of ICD implantation. Ablation was guided by a combination of substrate mapping, activation mapping, and pace mapping. The use of antiarrhythmic medication was at the discretion of the treating physician. The median time to first recurrence of ventricular arrhythmias was longer in the ablation group than the ICD only group (18.6 vs. 5.9 months). There was a significantly better rate of survival free from recurrent VT in the ablation group (47 vs. 29%, hazard ratio = 0.61, p = 0.045). Upon subgroup analysis, patients with an EF of ≤30% derived no benefit from catheter ablation, while patients with an EF of >30% demonstrated a statistically significant decrease in arrhythmia recurrence. Some recent studies demonstrated that a more extensive substrate ablation targeting local abnormal ventricular activities, late potential and also going  for epicardial ablation were associated with a very favorable outcome approaching around 85% freedom from any VT at 2 years follow up and with a more limited use of antiarrhythmics.11–13 Extensive endo-epicardial substrate based ablation concepts targeting all the potential VT circuits within the scar can increase the procedural success in patients with infarct-related VT. Study involving newer ablation techniques as first-line therapy can answer the question about the role of ICD implantation in these patients. Though not well established by randomized data, selected patients with stable VT, and relatively preserved LV function generally have a sufficiently good prognosis to undergo ablation as a stand-alone therapy without placing an ICD and two to three cases can be done with a single patch/catheter to bring the cost further down. Patient with sustained monomorphic scar-related VT may be treated with ablation early in its clinical course. Early referral for catheter ablation following ICD intervention has the potential to decrease arrhythmia recurrence and ICD intervention. Available data do not allow conclusion on the impact of primary VT ablation on mortality and further studies are required. The concept of prophylactic catheter ablation before ICD implantation has special implications for countries such as India as a) it reduces device therapy therefore increasing quality of life and device longevity b) patients may require less costly and sophisticated device and c) with increasing experience and evidence, catheter ablation has the potential for being “stand alone” in selected patients with structural heart disease and risk of SCD.