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Purpose: To determine whether monomorphic ventricular tachycardias (VTs) have different characteristics and/or responses to antitachycardia pacing (ATP) with respect to the indication-primary prevention (PP) versus secondary prevention (SP)-among ICD patients with left ventricular dysfunction., Methods: We prospectively studied 551 VT (cycle length [CL] 329 ± 35 ms; PP 34%) occurring in 67 ICD patients with left ventricular dysfunction (LVEF 35 ± 8%). ICD programming was standardized, including ATP for slow (CL 400-321 ms) and fast VT (CL 250-320 ms). We analyzed the following aspects: CL, percentage of variability of the 12 RR intervals prior to ATP (P-RR)-which was calculated by dividing the mean difference between each R-R interval with the next one by the CL × 100-and type of termination: immediate (VT ceased immediately upon ATP completion) or delayed (VT persisted after ATP)., Results: ATP was successful in 86% of VTs. VTs occurring in SP patients had a lower P-RR, median (IQR) 2.7% (1.2-3.7) versus 1.9% (0.9-3.2); p = 0.002; they terminated immediately after ATP less frequently (27% versus 12%; p < 0.001), and although they were more frequently slow (51% versus 67%; p = 0.01), ATP was less effective in them, 92 versus 80% (p = 0.02)., Conclusions: VTs occurring in SP patients are slower, more stable, and they terminate less frequently at ATP. Therefore, compared with PP, SP patients seem to have fewer self-terminating VTs.

The purposes of this study were to characterize and quantify concordance between consecutive atrial and ventricular activation time points through analysis of phases and to explore its association with outcomes in patients with implantable cardioverter-defibrillator (ICD). Patients with structural heart disease and dual-chamber ICDs underwent 5min baseline right ventricular (V) near-field and atrial (A) electrogram (EGM) recording. The cross-dependencies of phase dynamics of the changes in consecutive A (AA') and V (VV') were quantified and the AV phase dependency index was determined. In Cox regression analysis, a high AV phase index (in the highest quartile, >0.259) was significantly associated with higher risk of ventricular tachyarrhythmias (HR 2.84; 95% CI 1.05-7.67; P=0.04). In conclusion, in ICD patients with structural heart disease, high sinus AV phase dependency index on EGM is associated with the risk of ventricular arrhythmia., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Aims: The prognostic significance of ventricular tachycardia (VT) induced by three extrastimuli (ES) is similar to that of VT induced by one or two ES in patients with coronary disease and abnormal left ventricular (LV) function. The significance of VT inducible with four ES is unclear. To examine the prognostic significance of VT inducible with the fourth ES in patients with post-myocardial infarct (MI) LV dysfunction., Methods and Results: Consecutive patients (n= 432) with post-MI LV ejection fraction ≤40% underwent electrophysiological (EP) studies for risk stratification. Inducible VT ≥ 200 ms cycle length (CL) with one to four ES was considered inducible. The primary endpoint of arrhythmia (sudden death or spontaneous VT/ventricular fibrillation) was compared among patients with VT inducible with less than or equal to two, three, and four ES. The incidence of inducible VT was 37.9% (n= 164). In patients with inducible VT, inducibility was with less than or equal to two, three, and four ES in 24% (n= 39), 46% (n= 75), and 30% (n= 50). Compared to VT induced with less than or equal to three ES, VT induced with the fourth ES was of shorter CL (218 vs. 256 ms, P = 0.01) and more likely to be haemodynamically unstable requiring cardioversion (77 vs. 55%, P = 0.05). After 3 years the primary endpoint occurred in 28 ± 8, 28 ± 6, and 18 ± 6% in patients with VT induced with less than or equal to two, three, and four ES, respectively (P= 0.31) and in 5 ± 2% of EP-negative patients (P< 0.01)., Conclusion: In patients with post-MI LV dysfunction, VT can be induced in a significant proportion of patients with the fourth ES. These patients are at comparable risk of arrhythmia to patients with inducible VT with less than or equal to three ES.

Background: Aim of our study is to evaluate the role of T-wave alternans (TWA) to stratify the risk of sudden cardiac death in athletes (Ath) with complex ventricular arrhythmias (VA), and to document a possible correlation between TWA and electrophysiological testing (EPS) results., Methods: We studied 85 Ath with VA (61 M, mean age 32 +/- 11 years). In all cases a cardiological evaluation was performed, including TWA and EPS. The patients were evaluated during a follow-up of 30 +/- 21 months. The end point was the occurrence of sudden death (SD) or malignant ventricular tachyarrhythmias (VT)., Results: TWA was negative in 57 Ath (68%), positive in 15 (18%) and indeterminate in 13 (14%). All subjects with negative TWA did not show induction of VT at EPS, with significant correlation between negative TWA and negative EPS (P < 0.001). All Ath with positive TWA also had VT induced by a EPS, with significant correlation (P < 0.001). By contrast, our data did not show significant correlation between indeterminate TWA and positive or negative EPS. However, there was significant correlation between abnormal TWA test (positive + indeterminate) and inducibility of VT at EPS (P < 0.001). During follow-up we observed a significant difference in end point occurrence (VT or SD) between Ath with negative or abnormal TWA and between Ath with negative or positive EPS., Conclusion: TWA confirm its role as a simple and noninvasive test, and it seems useful for prognostic stratification of Ath with VA.

Background: Although electrophysiologic study (EPS) is one of the most reliable methods for selecting preventive therapy for patients with sustained ventricular tachycardia (VT), VT may recur during EPS-guided effective therapy; therefore, the importance of implantable cardioverter-defibrillator (ICD) has been emphasized. In this study, the prognoses of VT patients were evaluated to clarify the importance of EPS-guided therapy for the secondary prevention of VT., Methods and Results: The study population consisted of 99 consecutive patients with a history of sustained VT, which was inducible in EPS. The VT induction protocol used 1-3 extrastimuli and rapid ventricular pacing at 2 right ventricular sites and included additional isoproterenol infusion. ICD implantation was applied to all patients with an episode of hemodynamically unstable VT, regardless of the result of preventive therapy. For preventive therapy, an antiarrhythmic drug and/or catheter ablation were selected, and they were defined as being effective in the EPS-guided therapy when the induction of VT was completely prevented. When no therapy was effective for prevention, an antiarrhythmic drug was prescribed under ICD implantation. During the follow-up period of 19+/-20 months, VT recurred in 17 of 32 patients (53%) in the ineffective group and in 10 of 67 patients (15%) in the effective group (p=0.0001). The therapies used in the effective group were class I antiarrhythmic drug in 9, class III in 15, and catheter ablation in 35 patients. Between the patients with and without VT recurrence, there were no significant differences in the left ventricular ejection fraction and the maximum number of repetitive ventricular responses that remained in VT induction in EPS., Conclusions: Although VT may recur in up to 15% of patients with EPS-guided effective therapy, the recurrence rate was significantly reduced in comparison to that in the ineffective group. EPS-guided therapy may be useful to reduce the clinical recurrence of VT, as well as the action of ICD.

QRS prolongation on surface electrocardiography has been identified as a marker for increased cardiac mortality. A potential mechanism for increased mortality is ventricular tachycardia (VT). This study aimed to evaluate the relation between bundle branch block and sustained monomorphic VT inducibility in patients referred for electrophysiologic studies. We analyzed a cohort of 777 patients (age 63 +/- 18 years, 67% men, left ventricular [LV] ejection fraction [EF] 45% +/- 16, prior myocardial infarction 41%) referred for electrophysiologic studies between 1994 and 2001 who underwent programmed stimulation for VT. Forty-five percent of patients were referred for syncope or a history of VT and/or ventricular fibrillation. Thirty-one percent of patients had prolonged QRS duration (> or =120 ms). Patients with prolonged QRS duration were older, had lower LVEFs, and were more likely to have a history of myocardial infarction. Prolonged QRS was a significant predictor of sustained monomorphic VT inducibility (p <0.0001). On multivariate analysis correcting for age, sex, LVEF, history of myocardial infarction, medications, and QRS conduction delay proved to be independently associated with sustained monomorphic VT inducibility (relative risk 3.290, 95% confidence interval 2.185 to 4.953 for prolonged vs normal QRS duration). Thus, a prolonged QRS duration on surface electrocardiography is a strong, independent predictor of inducible sustained monomorphic VT. Conduction delay may be an important risk factor, providing a substrate for the development of reentrant monomorphic VT, and furthermore suggests a potential mechanism for the increased mortality observed in patients with prolonged QRS.

Objectives: We sought to determine the value of electrophysiology (EP) testing in patients with ventricular fibrillation (VF), ventricular tachycardia (VT) with syncope, or sustained VT in the setting of left ventricular dysfunction., Background: Traditionally, EP testing is part of the workup of patients with sustained VT or VF. Recently, some have suggested that EP testing is unnecessary in these patients, many of whom are likely to receive an implantable cardioverter-defibrillator (ICD)., Methods: Within a multicenter trial (Antiarrhythmics Versus Implantable Defibrillators) designed to evaluate whether drugs or ICD resulted in a better outcome, data were analyzed regarding EP testing. Although this testing was not required, it was performed in >50% of patients. Information regarding the results of EP testing was correlated to baseline clinical characteristics and outcome., Results: Of 572 patients subjected to an EP test, 384 (67%) had inducible sustained VT or VF. Inducible patients were more likely to have coronary artery disease, previous infarction, and VT as their index arrhythmic event. Inducibility of VT or VF did not predict death or recurrent VT or VF., Conclusions: Information derived from EP testing in this patient population, particularly those with VF, is of limited value and may not be worth the risks and costs of the procedure, particularly in those patients likely to receive an ICD.

Background: The use of coronary angiography and revascularization is lower than expected among black patients. It is uncertain whether use of other cardiac procedures also varies according to race and ethnicity and whether outcomes are affected., Methods: We analyzed discharge abstracts from all nonfederal hospitals in California of patients hospitalized for a primary diagnosis of ventricular tachycardia or ventricular fibrillation between 1992 and 1994. We compared mortality rates and use of electrophysiologic study (EPS) and implantable cardioverter-defibrillator (ICD) procedures according to the race and ethnicity of the patient., Results: Among 8713 patients admitted with ventricular tachycardia or ventricular fibrillation, 29% (n = 2508) had a subsequent EPS procedure, and 9% (n = 818) had an ICD implanted. After controlling for potential confounding factors, we found that black patients were significantly less likely than white patients to undergo EPS (odds ratio 0.72, CI 0.56-0.92) or ICD implantation (odds ratio 0.39, CI 0.25-0.60). Blacks discharged alive from the initial hospital admission had higher mortality rates over the next year than white patients, even after controlling for multiple confounding risk factors (risk ratio 1.18, CI 1.03-1.36). The use of EPS and ICD procedures was also significantly affected by several other factors, most notably by on-site procedure availability but also by age, sex, and insurance status., Conclusions: In a large population of patients hospitalized for ventricular arrhythmia, blacks had significantly lower rates of utilization for EPS and ICD procedures and higher subsequent mortality rates.