Mapping and Ablation of Arrhythmias from Uncommon Sites (Aortic Cusp, Pulmonary Artery, and Left Ventricular Summit).

Despite advances in our understanding of the relevant anatomy and mapping and catheter ablation techniques of idiopathic outflow tract ventricular arrhythmias, challenging sites for catheter ablation remain the aortic cusps, pulmonary artery, and notably the left ventricular summit. A systematic approach should be used to direct mapping efforts efficiently between endocardial, coronary venous, and epicardial sites. Foci at the left ventricular summit, particularly intraseptal and at the inaccessible epicardial region, remain difficult to reach and when percutaneous techniques fail, surgical ablation remains an option but with risk of late coronary artery stenosis.

Ventricular tachycardia in nonischemic cardiomyopathy: Anteroseptal vs inferolateral origin based on ICD ventricular electrogram timing.

INTRODUCTION: The majority of patients with nonischemic cardiomyopathy (NICM) present a perivalvular substrate that is either predominantly antero-septal (AS) or infero-lateral (IL), corresponding to specific ventricular tachycardia (VT) morphologies. The relative timing of far-field and near-field ventricular electrograms (EGMs) from stored implantable cardioverter-defibrillator (ICD) events of VT may be used to distinguish AS from IL VT in NICM. METHODS AND RESULTS: We analyzed 48 patients with NICM with either a primarily AS (54%) or IL (56%) VT source undergoing catheter ablation between 2003 and 2018. Only patients with retrievable ICD-EGMs of spontaneous VT events which could be matched with VTs induced during the ablation procedure were included. A total of 56 VT events (52% AS origin and 48% IL origin) were analyzed, yielding a mean far-field to near-field interval of 31 ± 13 milliseconds for AS VTs and 47 ± 19 milliseconds for IL VTs (P = .001). At receiver operating characteristic analysis (AUC = 0.734), a far-field to near-field interval of ≥ 60 milliseconds ruled out AS VTs in 29 (100%) cases and diagnosed IL VTs with a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 63%. An interval of ≤ 20 milliseconds ruled out IL VTs in 25 (93%) cases and diagnosed AS VTs with a PPV of 83% and NPV of 57%. Significant overlap between the two groups was observed among far-field to near-field intervals in between 20 milliseconds and 60 milliseconds. CONCLUSIONS: The relative timing of far-field and near-field EGMs from stored clinical ICD events of VT can be helpful to differentiate AS vs IL origin of VT in NICM.

Usefulness of ICD electrograms analysis to distinguish endocardial vs epicardial ventricular tachycardia in arrhythmogenic right ventricular cardiomyopathy.

INTRODUCTION: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by an epicardial (EPI) to endocardial (ENDO) fibrofatty infiltration of the RV predisposing to both EPI and ENDO ventricular tachycardia (VT). The relative timing between the VT QRS onset on the far-field ventricular electrogram (VEGM) to the local activation time recorded at the RV apex on the near-field VEGM from stored implantable cardioverter-defibrillator (ICD) events of VT can be helpful to discriminate ENDO from EPI VT in ARVC. METHODS AND RESULTS: We analyzed consecutive ARVC patients undergoing catheter ablation between 2006 and 2018. Only patients with retrievable ICD VEGMs of clinical VTs which could be matched with VTs induced at the time of ablation were included. A total of 26 VT events (16 ENDO, 10 EPI) from 19 ARVC patients were examined, yielding a mean far-field to near-field interval of 33 ± 15 ms for ENDO VTs and 52 ± 20 ms for EPI VTs (P = .020). At receiver-operating characteristic analysis, a far-field to a near-field interval of 60 ms or more ruled out ENDO VTs in 16 (100%) cases and identified EPI VTs with a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 73%. An interval of less than or equal to 30 ms ruled out EPI VTs in eight (80%) cases and diagnosed ENDO VTs with a PPV of 80% and an NPV of 50%. CONCLUSION: Far-field to near-field ICD VEGM timing may be used to predict ENDO vs EPI VT in ARVC before ablation, indicating an ENDO origin if the timing is less than or equal to 30 ms and an EPI origin if greater than or equal to 60 ms.