Nonsustained Ventricular Tachycardia Is Independently Associated With Sustained Ventricular Arrhythmias in Nonischemic Dilated Cardiomyopathy.

BACKGROUND: Spontaneous nonsustained ventricular tachycardia (NSVT) on Holter, VT inducibility during electrophysiology study, and late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) have been associated with sustained ventricular arrhythmias (SVAs) in nonischemic dilated cardiomyopathy (DCM). This study aimed to analyze whether these parameters carry independent prognostic value for spontaneous SVA in DCM. METHODS: Between 2011 and 2018, patients with the DCM clinical spectrum and documented SVA, suspected SVA, or considered to be at intermediate or high risk for SVA were enrolled in the prospective Leiden Nonischemic Cardiomyopathy Study. Patients underwent a comprehensive evaluation including 24-hour Holter, LGE-CMR, and electrophysiology study. Holters were assessed for the presence of NSVT (≥3 beats; rate, ≥120 bpm; lasting <30 s) and NSVT characteristics (coupling interval, duration, cycle length, morphology, regularity). Patients were followed at 6 to 12 monthly intervals. RESULTS: Of all 115 patients (age, 59±12 years; 77% men; left ventricular ejection fraction, 33±13%; history of SVA, 36%; LGE in 63%; median LGE mass, 13 g; interquartile range, 8-23 g), 62 (54%) had NSVT on Holter, and sustained monomorphic VT was inducible in 34 of 114 patients (30%). NSVT was not associated with LGE on CMR or VT inducibility during electrophysiology study nor were its features (all P>0.05). During 4.0±1.8 years of follow-up, SVA occurred in 39 patients (34%). NSVT (HR, 4.47 [95% CI, 1.87-10.72]; P=0.001) and VT inducibility (HR, 3.08 [95% CI, 1.08-8.81]; P=0.036) were independently associated with SVA during follow-up. A bivariable model including only noninvasively acquired parameters also allowed identification of a high-risk subgroup (ie, those with both NSVT and LGE on CMR). The findings remained similar when only patients without prior SVA were included. CONCLUSIONS: In patients with DCM, NSVT on Holter and VT inducibility during electrophysiology study predict SVA during follow-up independent of LGE on CMR. NSVTs may serve as an initiator, and sustained VT inducibility indicates the presence of the substrate for SVA in DCM. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01940081.

Slow Conducting Electroanatomic Isthmuses: An Important Link Between QRS Duration and Ventricular Tachycardia in Tetralogy of Fallot.

OBJECTIVES: This study sought to evaluate the influence of slow conducting anatomic isthmuses (SCAI) as dominant ventricular tachycardia (VT) substrate on QRS duration. BACKGROUND: QRS prolongation has been associated with VT in repaired tetralogy of Fallot. METHODS: Seventy-eight repaired tetralogy of Fallot patients (age 37 ± 15 years, 52 male, QRS duration 153 ± 29 ms, 67 right bundle branch blocks [RBBB]) underwent programmed stimulation and electroanatomic activation mapping during sinus rhythm. Right ventricular (RV) surface, RV activation pattern, RV activation time, conduction velocity at AI, and remote RV sites were determined. RESULTS: Twenty-four patients were inducible for VT (VT+); SCAI was present in 22 of 24 VT+ but only in 2 of 54 patients without inducible VT (VT-). Conduction velocity through AI was slower in VT+ patients (median of 0.3 [0.3 to 0.4] vs. 0.7 [0.6 to 0.9] m/s; p < 0.01) but conduction velocity in the remote RV did not differ between groups. In non-RBBB, QRS duration was similar in VT+ patients (n = 6) and VT- patients (n = 5), but RV activation within SCAI exceeded QRS offset in VT+ patients (37 ± 20 ms vs. -5 ± 9 ms, p < 0.01). In RBBB, both QRS duration and RV activation time were longer in VT+ patients (n = 18, 17 of 18 QRS > 150 ms) compared with VT- patients (n = 49, 27 of 49 QRS > 150 ms) (173 ± 22 ms vs. 156 ± 20 ms; p < 0.01; 141 ± 22 ms vs. 129 ± 21 ms; p = 0.04). In VT+ patients, QRS prolongation >150 ms (n = 17) was due to SCAI or blocked isthmus in 15 patients (88%) and 1 (6%). In contrast, in VT- patients, QRS prolongation >150 ms (n = 27) was due to enlarged RV or blocked isthmus in 10 patients (37%) and 8 (30%), but due to SCAI in only 1 (4%). After exclusion of a severely enlarged RV, a QRS duration >150 ms was highly predictive for SCAI/blocked AI (OR: 17; 95% CI: 3.3 to 84; p < 0.01). CONCLUSIONS: A narrow QRS interval does not exclude VT-related SCAI. In the presence of RBBB, SCAI further prolongs QRS duration. QRS duration >150 ms is highly suspicious for SCAI or isthmus block distinguishable by electroanatomic mapping.

Re-entry using anatomically determined isthmuses: a curable ventricular tachycardia in repaired congenital heart disease.

BACKGROUND: Ventricular tachycardia (VT) is an important cause of late morbidity and mortality in repaired congenital heart disease. The substrate often includes anatomic isthmuses that can be transected by radiofrequency catheter ablation similar to isthmus block for atrial flutter. This study evaluates the long-term efficacy of isthmus block for treatment of re-entry VT in adults with repaired congenital heart disease. METHODS AND RESULTS: Thirty-four patients (49±13 years; 74% male) with repaired congenital heart disease who underwent radiofrequency catheter ablation of VT in 2 centers were included. Twenty-two (65%) had a preserved left and right ventricular function. Patients were inducible for 1 (interquartile range, 1-2) VT, median cycle length: 295 ms (interquartile range, 242-346). Ablation aimed to transect anatomic isthmuses containing VT re-entry circuit isthmuses. Procedural success was defined as noninducibility of any VT and transection of the anatomic isthmus and was achieved in 25 (74%) patients. During long-term follow-up (46±29 months), all patients with procedural success (18/25 with internal cardiac defibrillators) were free of VT recurrence but 7 of 18 experienced internal cardiac defibrillator-related complications. One patient with procedural success and depressed cardiac function received an internal cardiac defibrillator shock for ventricular fibrillation. None of the 18 patients (12/18 with internal cardiac defibrillators) with complete success and preserved cardiac function experienced any ventricular arrhythmia. In contrast, VT recurred in 4 of 9 patients without procedural success. Four patients died from nonarrhythmic causes. CONCLUSIONS: In patients with repaired congenital heart disease with preserved ventricular function and isthmus-dependent re-entry, VT isthmus ablation can be curative.

Left-sided ablation of ventricular tachycardia in adults with repaired tetralogy of Fallot: a case series.

BACKGROUND: Radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) in repaired Tetralogy of Fallot focuses on isthmuses in the right ventricle but may be hampered by hypertrophied myocardium or prosthetic material. These patients may benefit from ablation at the left side of the ventricular septum. METHODS AND RESULTS: Records from 28 consecutive repaired Tetralogy of Fallot patients from 2 centers who underwent VT ablation were reviewed. Ablation targeted anatomic isthmuses containing VT re-entry circuits, which were identified by 3-dimensional substrate, pace, and entrainment mapping. A left-sided approach was considered beneficial if (1) right-sided RFCA failed, (2) part of the circuit was mapped to the left side, and (3) left-sided RFCA resulted in isthmus transection and prevention of VT induction. In 4 of 28 patients (52±13 years; 75% men), inducible for 1.5 (quartiles, 1.0 - 2.0) VTs (335±58 ms), left-sided RFCA was performed. In 3 patients, RFCA at aortic sites terminated VT related to a septal isthmus and prevented reinduction. In 1 patient, with prior biventricular implantable cardioverter-defibrillator, diastolic activity was recorded at the left side of the septum in proximity to the His-bundle. RFCA prevented VT reinduction with anticipated complete atrioventricular block. The left-sided approach resulted in complete procedural success (transection of anatomic isthmus and noninducibility) and freedom of VT recurrence during follow-up (20±15 months) in all patients. Right-sided RFCA failure was likely because of septal hypertrophy in 2, overlying pulmonary homograft in 1, and overlying ventricular septal defect patch in 1. CONCLUSIONS: Left-sided RFCA for VTs dependent on septal anatomic isthmuses improves ablation outcome in repaired Tetralogy of Fallot.

Endocardial or epicardial ventricular tachycardia in nonischemic cardiomyopathy? The role of 12-lead ECG criteria in clinical practice.

BACKGROUND: Specific 12-lead ECG criteria have been reported to predict an epicardial site of origin (SoO) of induced ventricular tachycardias (VTs) in left ventricular nonischemic cardiomyopathy. OBJECTIVE: The purpose of this study was to (1) determine the value of ECG criteria to predict an epicardial SoO of clinically documented VTs, (2) analyze the effect of VT cycle length (CL) and antiarrhythmic drugs on the accuracy of ECG criteria, and (3) assess interobserver variability. METHODS: In 36 consecutive patients with nonischemic left ventricular cardiomyopathy (age 58 ± 16 years, 75% male) who underwent combined endocardial/epicardial VT ablation, all clinically documented and induced right bundle branch block VTs were analyzed for previously reported ECG criteria to determine the SoO, as defined by ≥11/12 pace-map, concealed entrainment, and/or VT termination during ablation. RESULTS: In 21 patients with clinically documented (25 mm/s) right bundle branch block VT, none of the ECG criteria differentiated between patients with and those without an epicardial SoO. In induced VTs (100 mm/s), 2 of 4 interval criteria differentiated between an endocardial and epicardial SoO for slow VTs (CL >350 ms) and 2 of 4 criteria in patients on amiodarone, but none for fast VTs (CL ≤350 ms) or patients off amiodarone. The Q wave in lead I was the most accurate criterion for an epicardial SoO (sensitivity 88%, specificity 80%). In both clinically documented and induced VTs, interobserver agreement was poor for pseudodelta wave and moderate for other criteria. CONCLUSION: When applied to clinically documented VTs, no ECG criterion could differentiate between patients with and those without an epicardial SoO. Published interval-based ECG criteria do not apply to fast VTs and patients off amiodarone.