Catheter Ablation of Scar-mediated Ventricular Tachycardia: Are Substrate-based Approaches Replacing Mapping?

Scar-mediated ventricular tachycardia (VT) is a recognized cause of morbidity and mortality in patients with ischemic cardiomyopathy and other cardiomyopathies such as nonischemic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, and cardiac sarcoidosis. Implantable cardioverter-defibrillator (ICD) therapy improves survival but does not prevent the onset of recurrent VT or associated morbidity from ICD shocks. While randomized controlled trials have demonstrated advantages of scar-mediated VT ablation in comparison with antiarrhythmic drugs, procedural success has remained overall modest at between 50% and 70%. Standard scar-mediated VT ablation has relied on the use of activation and entrainment mapping during sustained VT to identify critical isthmuses for ablation. Substrate-based approaches have emerged as options to address hemodynamically unstable VT and have focused on identifying electrograms characteristic of critical isthmuses (eg, late potentials, local abnormal ventricular activities, conducting channels) within dense scar during sinus rhythm. Scar homogenization, a more recent approach, relies minimally on mapping and focuses on complete substrate modification. Core isolation, on the other hand, another recent development, relies heavily on mapping to identify regions within scar that are "cores" for arrhythmogenicity and then concentrates ablation to these areas. At this time, scar-mediated VT ablation appears to be at a crossroads wherein evolving substrate-based approaches are exploring whether to rely less or increasingly more on mapping. This review will therefore discuss the evolution of substrate-based, scar-mediated VT ablation and in the process try to answer whether there is still a role for mapping.

Left Atrial Appendage Isolation in Patients With Longstanding Persistent AF Undergoing Catheter Ablation: BELIEF Trial.

BACKGROUND: Longstanding persistent (LSP) atrial fibrillation (AF) is the most challenging type of AF. In addition to pulmonary vein isolation, substrate modification and triggers ablation have been reported to improve freedom from AF in patients with LSPAF. OBJECTIVES: This study sought to assess whether the empirical electrical isolation of the left atrial appendage (LAA) could improve success at follow-up. METHODS: This was an open-label, randomized study assessing the effectiveness of empirical electrical left atrial appendage isolation for the treatment of LSPAF. Patients were randomly assigned to undergo empirical electrical left atrial appendage isolation along with extensive ablation (group 1; n = 85) or extensive ablation alone (group 2; n = 88). Recurrence of atrial arrhythmias was the primary endpoint. Secondary endpoints included cardiac-related hospitalization, all-cause mortality, and stroke at follow-up. RESULTS: Major clinical characteristics were not different between the 2 groups. At 12-month follow-up, 48 (56%) patients in group 1 and 25 (28%) in group 2 were recurrence free after a single procedure (unadjusted hazard ratio [HR] for recurrence with standard ablation: 1.92; 95% confidence interval [CI]: 1.3 to 2.9; log-rank p = 0.001). After adjusting for age, sex, and left atrial size, standard ablation was predictive of recurrence (HR: 2.22; 95% CI: 1.29 to 3.81; p = 0.004). During repeat procedures, empirical electrical left atrial appendage isolation was performed in all patients. After an average of 1.3 procedures, cumulative success at 24-month follow-up was reported in 65 (76%) in group 1 and in 49 (56%) in group 2 (unadjusted HR: 2.24; 95% CI: 1.3 to 3.8; log-rank p = 0.003). CONCLUSIONS: This randomized study showed that both after a single procedure and after redo procedures in patients with LSPAF, empirical electrical isolation of the LAA improved long-term freedom from atrial arrhythmias without increasing complications. (Effect of Empirical Left Atrial Appendage Isolation on Long-term Procedure Outcome in Patients With Persistent or Longstanding Persistent Atrial Fibrillation Undergoing Catheter Ablation [BELIEF]; NCT01362738).

Feasibility and safety of uninterrupted periprocedural apixaban administration in patients undergoing radiofrequency catheter ablation for atrial fibrillation: Results from a multicenter study.

BACKGROUND: Periprocedural anticoagulation management with uninterrupted warfarin and a "therapeutic" international normalized ratio is the best approach for reducing both thromboembolic and bleeding complications in the setting of catheter ablation for atrial fibrillation (AF). OBJECTIVE: The purpose of this study was to evaluate the safety and feasibility of uninterrupted apixaban in this setting. METHODS: This was a prospective multicenter registry of AF patients undergoing radiofrequency catheter ablation at 4 institutions in United States and Europe with uninterrupted apixaban. These patients were compared with an equal number of patients, matched for age, gender, and type of AF, undergoing AF ablation on uninterrupted warfarin. The apixaban group was comprised of consecutive patients who had taken their last dose of apixaban the morning of the procedure. A subset of 29 patients in the apixaban group underwent diffusion magnetic resonance imaging (dMRI) to detect silent cerebral ischemia. RESULTS: A total of 400 patients (200 patients in each group) were included in the study. The average age was 65.9 ± 9.9 years, 286 (71.5%) were male, and 334 (83.5%) had nonparoxysmal AF. There were no statistical differences with regard to major complications (1% vs 0.5%, P = 1), minor complications (3.5% vs 2.5%, P = .56), or total bleeding complications (4.5% vs 3%, P = .43) between the apixaban and warfarin groups. There were no symptomatic thromboembolic complications. All dMRIs were negative for "new" silent cerebral ischemia in the apixaban group. CONCLUSION: Uninterrupted apixaban administration in patients undergoing AF ablation seems to be feasible and effective in preventing clinical and silent thromboembolic events without increasing the risk of major bleeding.

Ablation of Stable VTs Versus Substrate Ablation in Ischemic Cardiomyopathy: The VISTA Randomized Multicenter Trial.

BACKGROUND: Catheter ablation reduces ventricular tachycardia (VT) recurrence and implantable cardioverter defibrillator shocks in patients with VT and ischemic cardiomyopathy. The most effective catheter ablation technique is unknown. OBJECTIVES: This study determined rates of VT recurrence in patients undergoing ablation limited to clinical VT along with mappable VTs ("clinical ablation") versus substrate-based ablation. METHODS: Subjects with ischemic cardiomyopathy and hemodynamically tolerated VT were randomized to clinical ablation (n = 60) versus substrate-based ablation that targeted all "abnormal" electrograms in the scar (n = 58). Primary endpoint was recurrence of VT. Secondary endpoints included periprocedural complications, 12-month mortality, and rehospitalizations. RESULTS: At 12-month follow-up, 9 (15.5%) and 29 (48.3%) patients had VT recurrence in substrate-based and clinical VT ablation groups, respectively (log-rank p < 0.001). More patients undergoing clinical VT ablation (58%) were on antiarrhythmic drugs after ablation versus substrate-based ablation (12%; p < 0.001). Seven (12%) patients with substrate ablation and 19 (32%) with clinical ablation required rehospitalization (p = 0.014). Overall 12-month mortality was 11.9%; 8.6% in substrate ablation and 15.0% in clinical ablation groups, respectively (log-rank p = 0.21). Combined incidence of rehospitalization and mortality was significantly lower with substrate ablation (p = 0.003). Periprocedural complications were similar in both groups (p = 0.61). CONCLUSIONS: An extensive substrate-based ablation approach is superior to ablation targeting only clinical and stable VTs in patients with ischemic cardiomyopathy presenting with tolerated VT. (Ablation of Clinical Ventricular Tachycardia Versus Addition of Substrate Ablation on the Long Term Success Rate of VT Ablation (VISTA); NCT01045668).

Remote monitoring of implantable pacemakers: in-office setup significantly improves successful data transmission.

BACKGROUND: Remote wireless follow-up of implanted pacemakers (PM) has become an attractive method of follow-up. Although wireless PM follow-up has several advantages compared with transtelephonic and office-based follow-up, its utility depends on successful transmission. HYPOTHESIS: Initial in-office setup of wireless PM will improve transmission rate as compared with home setup. METHODS: A total of 202 consecutive patients from 2 medical centers were included in this retrospective study. Patients in the home setup group (N = 101) had traditional home setup of wireless PM, whereas patients in the in-office group (N = 101) had setup of PMs by allied health professionals during the postoperative office visit. Successful transmission was defined as successful initial wireless transmission of PM data by 2 months postimplant. RESULTS: Of the 101 patients in the home setup group, 22 (22%) patients had successful transmission. Of the 101 patients in the in-office group, 92 (91%) patients had successful transmission (P < 0.0001). Logistic regression analysis showed that that the in-office group was independently associated with successful transmission (odds ratio: 114.5; 95% confidence interval: 32.1-408.4; P < 0.0001). CONCLUSIONS: In patients implanted with PM capable of remote wireless data transmission, initial home setup of the wireless monitoring device was frequently unsuccessful. In-office PM setup was associated with a significantly higher rate of successful transmission.

Ablation of perimitral flutter following catheter ablation of atrial fibrillation: impact on outcomes from a randomized study (PROPOSE).

INTRODUCTION: Patients with previous ablation for atrial fibrillation (AF) may experience recurrence of perimitral flutter (PMFL). These arrhythmias are usually triggered from sources that may also induce AF. This study aims at determining whether ablation of triggers or completing mitral valve isthmus (MVI) block prevents more arrhythmia recurrences. METHODS AND RESULTS: Sixty-five patients with recurrent PMFL after initial ablation of long standing persistent AF were included in this study. Thirty-two patients were randomized to MVI ablation only (Group 1) and 33 were randomized to cardioversion and repeat pulmonary vein (PV) isolation plus ablation of non-PV triggers (Group 2). MVI bidirectional block was achieved in all but 1 patient from Group 1. In Group 2, reconnection of 17 PVs was detected in 14 patients (42%). With isoproterenol challenge, 44 non-PV trigger sites were identified in 28 patients (85%, 1.57 sites per patient). At 18-month follow-up, 27 patients (84%) from Group 1 had recurrent atrial tachyarrhythmias, of whom 15 remained on antiarrhythmic drug (AAD); however, 28 patients from Group 2 (85%, P < 0.0001 vs Group 1) were free from arrhythmia off AAD. The ablation strategy used in Group 2 was associated with a lower risk of recurrence (hazard ratio = 0.10, 95% CI 0.04-0.28, P < 0.001) and an improved arrhythmia-free survival (log rank P < 0.0001). CONCLUSION: In patients presenting with PMFL after ablation for longstanding persistent AF, MVI block had limited impact on arrhythmia recurrence. On the other hand, elimination of all PV and non-PV triggers achieved higher freedom from atrial arrhythmias at follow-up.

Status of computerized electrocardiography.

Since the first reports on computerized ECG analysis were published in the early 1960s, there have been major advancements in this technology that have led to the availability of a computer interpretation for nearly all ECGs processed in the United States. Misinterpretation of the ECG is still a problem, however, especially with rhythm diagnoses and correctly identifying pacemaker activity. A sound understanding of the strengths and limitations of the current computer analysis programs is essential to avoid over-reliance on computer analysis and to prevent the inappropriate management of patients. The reliability of computerized ECG analysis programs will only continue to improve, and the degree to which expert readers will continue to be needed remains to be seen. In the meantime, until there is true automated ECG analysis, computerized interpretations should be viewed as an adjunct to, not a substitute for, interpretation by a competent and experienced physician.

Use of ibutilide in cardioversion of patients with atrial fibrillation or atrial flutter treated with class IC agents.

OBJECTIVES: We sought to assess the efficacy and safety of ibutilide cardioversion for those with atrial fibrillation (AF) or atrial flutter (AFL) receiving long-term treatmentwith class IC agents. BACKGROUND: Attenuation of ibutilide-induced QT prolongation has been observed in a small number of patients pretreated with class IC agents. The clinical significance of the interaction between ibutilide and class IC agents is unknown. METHODS: Seventy-one patients with AF (n = 48) or AFL (n = 23), receiving propafenone 300 to 900 mg/day (n = 46) or flecainide 100 to 300 mg/day (n = 25), presented for ibutilide (2.0 mg) cardioversion. RESULTS: The mean durations of arrhythmia episode and arrhythmia history were 25 +/- 48 days and 4.4 +/- 6.4 years, respectively. Sixty-five patients (91.5%) had normal left ventricular systolic function. Twenty-three of 48 patients (47.9%; 95% confidence interval, 33.3% to 62.8%) with AF and 17 of 23 patients (73.9%; 95% confidence interval, 51.6% to 89.8%) with AFL converted with mean conversion times of 25 +/- 14 min and 20 +/- 12 min, respectively. There was a small increase in corrected QT interval after ibutilide (from442 +/- 61 ms to 462 +/- 59 ms, p = 0.006). One patient developed non-sustained polymorphous ventricular tachycardia and responded to intravenous magnesium. Another developed sustained torsade de pointes and was treated effectively with direct-current shock and intravenous dopamine. CONCLUSIONS: Our observations suggest that the use of ibutilide in patients receiving class IC agents is as successful in restoring sinus rhythm and has a similar incidence of adverse effects as the use of ibutilide alone.

Famotidine and long QT syndrome.

Numerous drugs have been implicated in causing a prolonged QT interval and Torsades de pointes. However, the association of famotidine and acquired long QT syndrome has rarely been reported. We report 2 cases of famotidine-associated acquired long QT syndrome.

Pseudo-cross-stimulation due to first degree AV block.

During routine interrogation of a dual chamber pacemaker, atrial pacing stimulus outputs were found to coincide with surface electrogram QRS complexes raising concern for cross-stimulation. Scrutiny of the native rhythm, however, confirmed this to be "pseudo-cross-stimulation" where marked first degree AV block resulted in alignment of atrial stimulus outputs with preceding QRS complexes. Although cross-stimulation is rare, familiarity with cross-stimulation and pseudo-cross-stimulation is important because its recognition will avoid erroneous diagnoses of lead dislodgment or device malfunction.

Cutting balloon angioplasty through stent struts of a jailed sidebranch ostial lesion.

The treatment of sidebranch ostial lesions jailed after stent implantation is challenging. We report a case of successful Cutting Balloon angioplasty through stent struts of a severe, elastic sidebranch ostial lesion. Three-day follow-up angiography showed no recurrent stenosis. The patient was discharged with complete resolution of chest discomfort and the post-hospitalization course was uneventful. Cutting Balloon angioplasty may be an optimal strategy for the treatment of elastic ostial lesions in smaller vessels that are suboptimal for stenting. The long-term benefits of using a Cutting Balloon for the treatment of sidebranch ostial lesions are still to be determined.

The effect of clopidogrel in combination with aspirin when given before coronary artery bypass grafting.

OBJECTIVES: This study was designed to evaluate the effect of preoperative clopidogrel on coronary artery bypass graft surgery (CABG) outcomes. BACKGROUND: Clopidogrel in combination with aspirin, given before percutaneous coronary intervention, has become the standard for stent thrombosis prevention. Some premedicated patients, however, are found to have surgical disease on angiography, and irreversible platelet inhibition becomes a concern for upcoming CABG. METHODS: We prospectively studied 224 consecutive patients undergoing nonemergent first-time CABG, and compared those with preoperative clopidogrel exposure within seven days (n = 59) to those without exposure (n = 165). RESULTS: The groups were comparable in age, gender, body surface area, preoperative hematocrit, preoperative prothrombin time and prior myocardial infarction. The clopidogrel group had higher 24-h mean chest tube output (1,224 ml vs. 840 ml, p = 0.001), and more transfusions of red blood cells (2.51 U vs. 1.74 U, p = 0.036), platelets (0.86 U vs. 0.24 U, p = 0.001) and fresh frozen plasma (0.68 U vs. 0.24 U, p = 0.015). Moreover, reoperation for bleeding was 10-fold higher in the clopidogrel group (6.8% vs. 0.6%, p = 0.018). The clopidogrel group also had less extubation within 8 h (54.2% vs. 75.8%, p = 0.002) and a trend towards less hospital discharge within five days (33.9% vs. 46.7%, p = 0.094). CONCLUSIONS: Clopidogrel in combination with aspirin before CABG is associated with higher postoperative bleeding and morbidity. These findings raise concern regarding the routine administration of clopidogrel before anticipated coronary stent implantation.