Epicardial Radiofrequency Ablation Failure During Ablation Procedures for Ventricular Arrhythmias: Reasons and Implications for Outcomes.

BACKGROUND Radiofrequency ablation (RFA) from the epicardial space for ventricular arrhythmias is limited or impossible in some cases. Reasons for epicardial ablation failure and the effect on outcome have not been systematically analyzed. METHODS AND RESULTS We assessed reasons for epicardial RFA failure relative to the anatomic target area and the type of heart disease and assessed the effect of failed epicardial RFA on outcome after ablation procedures for ventricular arrhythmias in a large single-center cohort. Epicardial access was attempted during 309 ablation procedures in 277 patients and was achieved in 291 procedures (94%). Unlimited ablation in an identified target region could be performed in 181 cases (59%), limited ablation was possible in 22 cases (7%), and epicardial ablation was deemed not feasible in 88 cases (28%). Reasons for failed or limited ablation were unsuccessful epicardial access (6%), failure to identify an epicardial target (15%), proximity to a coronary artery (13%), proximity to the phrenic nerve (6%), and complications (<1%). Epicardial RFA was impeded in the majority of cases targeting the left ventricular summit region. Acute complications occurred in 9%. The risk for acute ablation failure was 8.3× higher (4.5-15.0; P<0.001) after no or limited epicardial RFA compared with unlimited RFA, and patients with unlimited epicardial RFA had better recurrence-free survival rates (P<0.001). CONCLUSIONS Epicardial RFA for ventricular arrhythmias is often limited even when pericardial access is successful. Variability of success is dependent on the target area, and the presence of factors limiting ablation is associated with worse outcomes.

Better outcome of ablation for sustained outflow-tract ventricular tachycardia when tachycardia is inducible.

AIMS In patients presenting with spontaneous sustained ventricular tachycardia (VT) from the outflow-tract region without overt structural heart disease ablation may target premature ventricular contractions (PVCs) when VT is not inducible. We aimed to determine whether inducibility of VT affects ablation outcome. METHODS AND RESULTS Data from 54 patients (31 men; age, 52 ± 13 years) without overt structural heart disease who underwent catheter ablation for symptomatic sustained VT originating from the right- or left-ventricular outflow region, including the great vessels. A single morphology of sustained VT was inducible in 18 (33%, SM group) patients, and 11 (20%) had multiple VT morphologies (MM group). VT was not inducible in 25 (46%) patients (VTni group). After ablation, VT was inducible in none of the SM group and in two (17%) patients in the MM group. In the VTni group, ablation targeted PVCs and 12 (48%) patients had some remaining PVCs after ablation. During follow-up (21 ± 19 months), VT recurred in 46% of VTni group, 40% of MM inducible group, and 6% of the SM inducible group (P = 0.004). Analysis of PVC morphology in the VTi group further supported the limitations of targeting PVCs in this population. CONCLUSION Absence of inducible VT and multiple VT morphologies are not uncommon in patients with documented sustained outflow-tract VT without overt structural heart disease. Inducible VT is associated with better outcomes, suggesting that attempts to induce VT to guide ablation are important in this population.

Long Term Outcomes Following Catheter Ablation of Ventricular Tachycardia in Patients with and without Structural Heart Disease.

BACKGROUND Long-term outcomes following ventricular tachycardia (VT) ablation are sparsely described. OBJECTIVES To describe long term prognosis following VT ablation in patients with no structural heart disease (no SHD), ischemic (ICM) and non-ischemic cardiomyopathy (NICM). METHODS Consecutive patients (n=695; no SHD 98, ICM 358, NICM 239 patients) ablated for sustained VT were followed for a median of 6 years. Acute procedural parameters (complete success [non-inducibility of any VT]) and outcomes after multiple procedures were reported. RESULTS Compared with patients with no SHD or NICM, ICM patients were the oldest, had more males, lowest left ventricular ejection fraction (LVEF), highest drug failures, VT storms and number of inducible VTs. Complete procedure success was highest in no SHD, compared ICM and NICM patients (79%, 56%, 60% respectively, P<0.001). At 6 years, ventricular arrhythmia (VA)-free survival was highest in no SHD (77%) than ICM (54%) and NICM (38%, P<0.001) and overall survival was lowest in ICM (48%), followed by NICM (74%) and no SHD patients (100%, P<0.001). Age, LVEF, presence of SHD, acute procedural success (non-inducibility of any VT), major complications, need for non-radiofrequency ablation modalities, and VA recurrence were independently associated with all cause mortality. CONCLUSIONS Long term follow up following VT ablation shows excellent prognosis in the absence of SHD, highest VA recurrence and transplantation in NICM and highest mortality in patients with ICM. The extremely low mortality for those without SHD suggests that VT in this population is very rarely an initial presentation of a myopathic process.