The Effect of Direct Current Stimulation versus T-Wave Shock on Defibrillation Threshold Testing.

INTRODUCTION: There are several methods to induce ventricular fibrillation (VF) during defibrillation threshold (DFT) testing. Delivering a shock at a critical time during the T wave (T-shock) is the conventional approach, while delivering a constant direct current voltage (DC stim) from the implantable cardioverter defibrillator is an alternative method. Only a few reports compare VF induction methods. The purpose of this study was to evaluate the effects and safety of DC stim versus T-shock. METHODS: We retrospectively investigated 414 consecutive patients undergoing DFT testing. We compared the two groups (DC stim and T-shock) with respect to clinical characteristics, electrocardiogram (ECG) changes, and complications. RESULTS: Ventricular arrhythmia, including ventricular tachycardia (VT) and VF, was induced by DC stim in 93 patients or T-shock in 321 patients. No more than three attempts were performed during one procedure. There was no significant difference in the baseline ECG, induced tachycardia cycle length (TCL), or complications between the two groups. However, the induced TCL was significantly shorter than the clinical TCL regardless of induction method (P = 0.001). Five patients suffered major complications (i.e., electromechanical dissociation or incessant VT). A history of atrial fibrillation was significantly greater in patients with major complications than the others (80% vs 24%, P = 0.004), and was an independent predictor on multivariate analysis. CONCLUSIONS: There is no significant difference in induced TCL or complications between the DC stim and T-shock. The induced TCL is significantly shorter than clinical TCL regardless of induction method.

Variable clinical features and ablation of manifest nodofascicular/ventricular pathways.

BACKGROUND: Manifest nodofascicular/ventricular (NFV) pathways are rare. METHODS AND RESULTS: From 2008 to 2013, 4 cases were identified with manifest NFV pathways from 3 centers. The clinical findings and ablation sites are reported. All 4 cases presented with a wide complex tachycardia but with different QRS morphologies. Case 1 showed a left bundle branch block/superior axis, case 2 showed a right bundle branch block/inferior axis, case 3 showed a left bundle branch block/inferior axis, and case 4 showed a narrow QRS tachycardia and a wide complex tachycardia with a left bundle branch block/inferior axis. Three of the 4 tachycardias had atrioventricular dissociation ruling out extranodal accessory pathways, including atriofascicular pathways. Programmed extrastimuli showed evidence of a decremental accessory pathway in 3 of the 4 cases. Coexisting tachycardia mechanisms were seen in 3 of the 4 cases (atrioventricular nodal reentry tachycardia [2] and atrioventricular reentrant tachycardia [1]). Ablation in the slow pathway region eliminated the NFV pathway in 3 (transient in 1) with the other responding to surgical closure of a large atrial septal defect. The NFV pathway was a critical part of the tachycardia circuit in 1 and proved to be a bystander in the other 3 cases. CONCLUSIONS: Manifest NFV pathways presented with variable QRS expression dependent on the ventricular insertion site and often coexisted with other tachycardia mechanisms (atrioventricular nodal reentry tachycardia and atrioventricular reentrant tachycardia). In most cases, the atrial insertion of the pathway was in or near the slow pathway region. The NFV pathways were either critical to the tachycardia circuit or served as bystanders.

His overdrive pacing during supraventricular tachycardia: a novel maneuver for distinguishing atrioventricular nodal reentrant tachycardia from atrioventricular reciprocating tachycardia.

BACKGROUND: Because the His bundle is intrinsic to the circuit in orthodromic reciprocating tachycardia and remote from that of atrioventricular nodal reentrant tachycardia (AVNRT), pacing the His bundle during supraventricular tachycardia (SVT) may be useful to distinguish these arrhythmias. OBJECTIVE: The purpose of this study was to test the hypothesis that His overdrive pacing (HOP) would affect SVT immediately for orthodromic reciprocating tachycardia and in a delayed manner for AVNRT. METHODS: Once SVT was induced, HOP was performed by pacing the His bundle 10-30 ms faster than the SVT cycle length. The maneuver was determined to have entered the tachycardia circuit when a nonfused His-capture beat advanced or delayed the subsequent atrial electrogram by ≥10 ms or when the tachycardia was terminated. The number of beats required to enter each tachycardia with HOP was recorded. RESULTS: HOP was performed during 66 SVTs (26 atrioventricular reciprocating tachycardia [AVRT] and 40 AVNRT). Entry into the tachycardia within 1 beat had sensitivity of 92%, specificity of 92%, positive predictive value (PPV) of 89% and negative predictive value (NPV) of 95% to confirm the diagnosis of AVRT. A cutoff ≥3 beats to enter the circuit had sensitivity of 90%, specificity of 92%, PPV of 95% and NPV of 86% to confirm the diagnosis of AVNRT. HOP had sensitivity, specificity, PPV, and NPV of 100% for distinguishing septal AVRT from atypical AVNRT. CONCLUSION: HOP during SVT is a novel technique for distinguishing orthodromic reciprocating tachycardia from AVNRT. It can reliably distinguish between these arrhythmias with high sensitivity and specificity.

Safety of new oral anticoagulants for patients undergoing atrial fibrillation ablation.

BACKGROUND: The new oral anticoagulants (NOAC), dabigatran and rivaroxaban, have been demonstrated to be at least equivalent to warfarin for preventing cardiac thromboembolism (TE) in patients with atrial fibrillation (AF). However, there is limited data regarding use around catheter ablation (CA) procedures. OBJECTIVE: We evaluated the risk of bleeding and TE complications associated with NOAC use during AF ablation. METHODS: Consecutive patients undergoing AF ablation between January 2011 and 6 September 2013 were grouped based on peri-procedural anticoagulation regimen: (1) uninterrupted warfarin with therapeutic INR (WARF), n = 114, (2) dabigatran, n = 89, or (3) rivaroxaban, n = 98. NOACs were held for 24 h (dabigatran) or 36 h (rivaroxaban) prior to the procedure. Heparin infusion was initiated 6 h post-procedure for the NOAC groups; NOACs were resumed the morning after the procedure. Antral PVI was performed with activated clotting time (ACT) maintained >300 s. TE or bleeding complications during ablation and through 30 days were compared. RESULTS: Three hundred and one patients underwent ablation for paroxysmal (71%) or persistent (29%) AF. International Normalization Ratio (INR) for the WARF group was 2.0 ± 0.5. Baseline characteristics were similar among the groups. There were two TE events (asymptomatic cerebral emboli and TIA), and there were 17 bleeding events (large hematoma n = 4; pericardial effusion n = 6; persistent hematuria n = 1; pseudoaneurism/AV fistula n = 6). Of the six pericardial effusions, three required drainage. There was no significant difference in combined TE/bleeding risk among the groups (WARF vs. dabigatran vs. rivaroxaban; 6.2% vs. 6.7% vs. 6.0%; p = 0.82) CONCLUSIONS: In this group of AF patients undergoing CA, use of peri-procedure dabigatran or rivaroxaban compared to uninterrupted warfarin did not lead to an increase in bleeding or TE complications.

Coupling interval dispersion and body mass index are independent predictors of idiopathic premature ventricular complex-induced cardiomyopathy.

INTRODUCTION: Patients with frequent premature ventricular complexes (PVCs) might be at risk for the developing or exacerbation of left ventricular (LV) dysfunction. However, some patients with a high-PVC burden do not develop cardiomyopathy, while other patients with low-PVC burden can develop cardiomyopathy. The purpose of this study was to evaluate the positive predictors of idiopathic PVCs-induced cardiomyopathy. METHODS AND RESULTS: We investigated 214 patients undergoing successful ablation of PVCs who had no other causes of cardiomyopathy. We divided the study cohort into 2 groups: ejection fraction (EF) ≥ 50% (normal LV) and EF < 50% (LV dysfunction). We analyzed the clinical characteristics, including the electrocardiogram and findings at electrophysiology study. Among these patients, 51 (24%) had reduced LVEF and 163 (76%) had normal LV function. Patients with LV dysfunction had significantly longer coupling interval (CI) dispersion (maximum-CI-minimum-CI) and had significantly higher PVC burden compared to those with normal LV function (CI-dispersion: 115 ± 25 milliseconds vs. 94 ± 19 milliseconds; P < 0.001; PVC burden: 19% vs. 15%; P = 0.04). Furthermore, patients with LV dysfunction had significantly higher body mass index (BMI) compared to those with normal LV function (BMI > 30 kg/m(2) ; 37% vs. 13%; P = 0.001). Logistic regression analysis showed that CI-dispersion, PVC burden, and BMI (>30 kg/m(2) ) are independent predictors of PVC-induced cardiomyopathy. CONCLUSIONS: In addition to the PVC burden, the CI-dispersion and BMI are associated with PVC-induced cardiomyopathy.

Frequency of atrial flutter after adult lung transplantation.

Lung transplantation, which involves an anastomosis of the graft to the native left atrium, may increase the risk of left-side atrial flutter (AFL). Our aim was to evaluate the incidence, predisposing conditions, and course of AFL after lung transplantation in adults. Two hundred sixty-nine consecutive patients who underwent lung transplantation were studied retrospectively. All patients received a preoperative echocardiogram and postoperative electrocardiographic monitoring. All 12-lead electrocardiograms were reviewed. Typical or atypical AFL was diagnosed by 2 independent reviewers based on accepted criteria. Predictors of AFL were investigated separately using univariate and multivariate logistic regression analyses. AFL occurred in 35 of 269 patients (13%) over a mean of 12 days after transplantation. All patients who developed AFL had no previous atrial arrhythmia. Of these 35 patients, 24 (68.6%) had atypical AFL by electrocardiographic criteria. In multivariate logistic regression analysis, patients with idiopathic pulmonary fibrosis (IPF) were 2.9 times more likely to have AFL than those patients with lung transplant without IPF (p = 0.009). Other independent risk factors for AFL were advanced age and preoperative left atrial enlargement. Only 3 of 35 patients (8.6%) with AFL had persistent atrial arrhythmia and needed electrophysiologic study and ablation. In conclusion, AFL is common soon after lung transplantation. Those with IPF, advanced age, or left atrial enlargement are at increased risk. In most cases, AFL is a self-limited arrhythmia that resolves spontaneously with no need for ablation.

Differences in accessory pathway location by sex and race.

BACKGROUND: The etiology of accessory pathway (AP) formation is generally unknown. OBJECTIVE: The purpose of this study was to test the hypothesis that AP formation is genetically mediated by examining whether AP location differs by sex and/or race, using sex and race as proxies to distinguish genetically different individuals. METHODS: This was a single-center, retrospective cohort study of 282 consecutive patients undergoing their first electrophysiology study that revealed at least one AP between 2004 and 2008. Sex and race were compared with AP location determined by invasive electrophysiology study. RESULTS: Eighty-nine (52%) males and 40 (36%) females had a left posterior AP (P = .006). Sixty-four (57%) females had a right annular AP, compared with 55 (32%) males (P <.001). After adjusting for age and race, females had 2.8-fold greater odds of having a right annular AP compared with males (95% confidence interval [CI] 1.70-4.65 greater odds; P <.001). While right anterior (free-wall) pathways were rare in all other races (12%), a significantly larger proportion of Asians (n = 10, 26%) had a right anterior AP (P = .017). After adjusting for sex and age, Asians had 3.8-fold greater odds of having a right anterior AP compared with other races (95% CI 1.5-9.4 greater odds; P = .004). CONCLUSIONS: Females more commonly had right annular APs, and Asians had right anterior APs substantially more frequently than other races. These findings suggest that the pathogenesis of AP formation may have a genetic component.

Test characteristics of neck fullness and witnessed neck pulsations in the diagnosis of typical AV nodal reentrant tachycardia.

BACKGROUND: Claims in the medical literature suggest that neck fullness and witnessed neck pulsations are useful in the diagnosis of typical AV nodal reentrant tachycardia (AVNRT). HYPOTHESIS: Neck fullness and witnessed neck pulsations have a high positive predictive value in the diagnosis of typical AVNRT. METHODS: We performed a cross-sectional study of consecutive patients with palpitations presenting to a single electrophysiology (EP) laboratory over a 1 year period. Each patient underwent a standard questionnaire regarding neck fullness and/or witnessed neck pulsations during their palpitations. The reference standard for diagnosis was determined by electrocardiogram and invasive EP studies. RESULTS: Comparing typical AVNRT to atrial fibrillation (AF) or atrial flutter (AFL) patients, the proportions with neck fullness and witnessed neck pulsations did not significantly differ: in the best case scenario (using the upper end of the 95% confidence interval (CI), none of the positive or negative predictive values exceeded 79%. After restricting the population to those with supraventricular tachycardia (SVT) other than AF or AFL, neck fullness again exhibited poor test characteristics; however, witnessed neck pulsations exhibited a specificity of 97% (95% CI: 90%-100%) and a positive predictive value of 83% (95% CI: 52%-98%). After adjustment for potential confounders, SVT patients with witnessed neck pulsations had a seven-fold greater odds of having typical AVNRT, p = 0.029. CONCLUSIONS: Although neither neck fullness nor witnessed neck pulsations are useful in distinguishing typical AVNRT from AF or AFL, witnessed neck pulsations are specific for the presence of typical AVNRT among those with SVT.

Regional left atrial voltage in patients with atrial fibrillation.

BACKGROUND: Regional differences in fibrosis, particularly related to the posterior wall and septum, may be important in atrial fibrillation (AF). Using electroanatomic mapping, voltage can be used as a measure of fibrosis. OBJECTIVES: The purpose of this study was to determine if patients with AF have disproportionately lower voltage in the septal and posterior walls of the left atrium. METHODS: Sinus rhythm left atrial electroanatomic maps were used in serial patients presenting for left atrial ablation of AF (8-mm tip). Patients undergoing left atrial mapping for focal atrial tachycardia (AT) were used as a comparison group (4-mm tip). Animal experiments were performed to assess the influence of ablation catheter tip size on voltage amplitude. RESULTS: The posterior and septal walls exhibited the lowest voltages in both groups. Compared with the anterior wall, there was a 3.78-fold greater odds of finding a low-voltage point (<0.5 mV) in the septum (P <.001) and a 3.37-fold greater odds of finding a low-voltage point in the posterior wall (P <.001) in the AF patients; the proportion of low-voltage points by region were not significantly different in the AT group. In the animal model, the mean voltage obtained from an 8-mm ablation catheter was significantly higher (0.30 +/- 0.17 mV) than that obtained from the same points using a 4-mm catheter (0.22 +/- 0.17, P = .05). CONCLUSION: Regional differences in voltage are present in patients with atrial arrhythmias, with AF patients exhibiting significantly more low-voltage areas in the septum and posterior walls.

Usefulness of a ventricular extrastimulus from the summit of the ventricular septum in diagnosis of septal accessory pathway in patients with supraventricular tachycardia.

To compare usefulness of a ventricular extrastimulus (VES) from the right ventricular (RV) apex versus the RV septum in patients with a septal accessory pathway (AP), VES was applied from the RV apex and the summit of the RV septum in patients with septal APs. A VES from the RV apex and from the summit was diagnostic of the presence of an AP in 13 of 28 patients (83%) and in 10 of 12 patients, respectively (46% p <0.05), and VES proved an AP as a part of the tachycardia circuit in 5 of 28 patients (18%) and 6 of 12 patients, respectively (50%, p <0.05). A VES during His bundle refractoriness from the RV summit increases the diagnostic yield for both the presence of an AP and its participation in the tachycardia circuit with respect to RV apical VES.