Use of Programmed Ventricular Extrastimulus During Supraventricular Tachycardia to Differentiate Atrioventricular Nodal Re-Entrant Tachycardia From Atrioventricular Re-Entrant Tachycardia.

OBJECTIVES: This study hypothesized that early coupled ventricular extrastimuli (V2) stimulation might yield a more robust differentiation between atrioventricular nodal re-entrant tachycardia (AVNRT) and atrioventricular re-entrant tachycardia (AVRT). BACKGROUND: Programmed V2 during supraventricular tachycardia are useful to differentiate AVNRT from AVRT by subtracting the ventriculoatrial (VA) interval from the stimulus to atrial depolarization (stimulus atrial [SA]) interval, but all such maneuvers have limitations. METHODS: Patients with either AVNRT or AVRT were investigated. The entire tachycardia cycle length (TCL) was scanned with V2 delivered from the right ventricular apex. The SA-VA difference was calculated with V2 clearly resetting the tachycardia. The prematurity of V2 was calculated by dividing the coupling interval (CI) by the TCL. RESULTS: A total of 210 patients (102 with AVNRT) were included. The SA-VA difference was >70 ms in all AVNRT patients and was <70 ms in all AVRT patients with right and septal accessory pathways (APs), except for those with decremental APs, in whom there was an overlap between AVNRT and AVRT with left APs. However, a SA-VA difference >110 ms with a CI/TCL of <65% distinguished AVNRT from AVRT using the left AP, with sensitivity and specificity of 87% and 100%, respectively. Ventricular overdrive pacing resulted in tachycardia termination or AV dissociation in 28% of patients compared with 15% of patients using the V2 technique (p = 0.008). CONCLUSIONS: A SA-VA of >70 ms using the V2 technique differentiated AVNRT from AVRT using septal and right APs. Use of the V2 technique with a short CI differentiated AVNRT from AVRT using left APs. The V2 technique less frequently resulted in tachycardia termination compared with ventricular entrainment.

Percutaneous alternative to the Maze procedure for the treatment of persistent or long-standing persistent atrial fibrillation (aMAZE trial): Rationale and design.

BACKGROUND: Pulmonary vein antrum isolation (PVI) as a treatment of paroxysmal atrial fibrillation (AF) is associated with a high rate of success; however, outcomes for treating persistent and long-standing persistent AF with PVI alone are substantially lower and often require multiple procedures to maintain long-term freedom from atrial arrhythmias. Foci and/or substrate outside the pulmonary veins, particularly in the left atrial appendage (LAA), has been identified as a key mechanism in the maintenance of persistent AF and long-standing persistent AF. OBJECTIVE: The goals of the study are to evaluate the safety and effectiveness of the LARIAT System to percutaneously isolate and ligate the LAA and to determine if LAA ligation as adjunctive therapy to PVI improves maintenance of sinus rhythm in patients with persistent and long-standing persistent AF. STUDY DESIGN: The trial is a prospective, multicenter, randomized controlled study. The trial design incorporates a Bayesian adaptive design that will randomize a maximum of 600 patients with persistent or long-standing persistent AF to LAA ligation and PVI vs PVI alone in a 2:1 randomization. The primary end points include 30-day safety of the LARIAT procedure and freedom from documented AF, atrial flutter, or atrial tachycardia of more than 30 seconds at 12 months after the PVI off antiarrhythmic drugs. Key secondary outcomes include a composite of cardiovascular death and stroke, as well as quality of life. CONCLUSION: The aMAZE trial will determine if LAA ligation as adjunctive therapy to PVI increases the efficacy of maintaining sinus rhythm in patients with persistent and long-standing persistent AF.

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.

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.

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.

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.

High-resolution optical mapping of ventricular tachycardia in rats with chronic myocardial infarction.

BACKGROUND: Ventricular tachycardia (VT) is a common cause of mortality in post-myocardial infarction (MI) patients, even in the current era of coronary revascularization treatment. We report a reproducible VT model in rats with chronic MI induced by ischemia-reperfusion and describe its electrophysiological characteristics using high-resolution optical mapping. METHODS: An MI was generated by left anterior descending coronary ligation (25 minutes) followed by reperfusion in 20 rats. Electrophysiology study and optical mapping were performed 5 weeks later using a Langendorff-perfused preparation and compared to normal rats. RESULTS: The conduction velocity of the MI border zone was decreased to 53% of the normal areas remote from the infarct (0.37 +/- 0.16 m/sec vs 0.70 +/- 0.09 m/sec, P < 0.0001). The rate of VT inducibility in MI rats was significantly greater than in normal control rats (70% vs 0%, P = 0.00002). VT circuits involving the infarct area were identified with optical mapping in 83% MI rats. In addition, fixed and functional conduction block were observed in the infarct border zone. CONCLUSION: This ischemia-reperfusion MI rat model is a reliable VT model, which simulates clinical revascularization treatment. High-resolution optical mapping in this model is useful to study the mechanism of VT and evaluate the effects of therapies.

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.

Surface electrocardiographic characteristics of right and left atrial flutter.

BACKGROUND: There is little information about the surface expression of non-cavotricuspid isthmus (CTI)-dependent right atrial (RA) or left atrial (LA) flutter circuits. METHODS AND RESULTS: We retrospectively evaluated 32 episodes (in 26 patients) of atypical RA and 22 episodes (in 21 patients) of LA flutter. The surface ECG of 13 patients with lower-loop reentry was similar to that of their pattern during counterclockwise (CCW) CTI atrial flutter (AFL), except for decreased amplitude of the terminal forces in the inferior leads. In 11 of 24 episodes characterized by high or multiple breaks over the crista, the ECG showed changes that depended on the initial activation sequence of the LA. In 7 of 8 episodes of upper-loop reentry, the ECG pattern completely mimicked that for clockwise (CW) CTI AFL. All 11 patients with an LA septal circuit showed a typical ECG pattern characterized by prominent forces in lead V1 with flat deflections in the other surface leads. Eleven patients with other LA circuits had a more variable pattern but showed decreased voltage in the inferior leads compared with that of a group with CCW-CTI AFL (1.6+/-1 vs 2.68+/-0.7 mV, respectively; P<0.05). CONCLUSIONS: The RA surface-ECG patterns different from those of CCW or CW-CTI could still be CTI dependent. In contrast, a typical CW-CTI surface pattern was always seen in patients with upper-loop reentry, which was non-CTI dependent. LA AFL circuits had either flat or low-amplitude forces in the inferior leads.

Postresuscitation stunning: postfibrillatory myocardial dysfunction caused by reduced myofilament Ca2+ responsiveness after ventricular fibrillation-induced myocyte Ca2+ overload.

INTRODUCTION: Resuscitation from ventricular fibrillation (VF), particularly from prolonged VF, frequently is complicated by postfibrillatory myocardial dysfunction (postresuscitation stunning). We tested whether this dysfunction can be caused by reduced myofilament Ca2+ responsiveness after VF-induced myocyte Ca2+ overload. We also tested whether electrical defibrillation shocks contribute to this dysfunction. METHODS AND RESULTS: Myofilament Ca2+ responsiveness was estimated as ratio of left ventricular developed pressure over myocyte Ca2+ transient amplitudes (assessed as indo-1 fluorescence) in isolated perfused rat hearts before, during, and after VF (1.5 or 10 min) comparing three modes of defibrillation (biphasic electrical shocks, lidocaine, or spontaneous). We found that, independent of these defibrillation modes, myofilament Ca2+ responsiveness was significantly reduced, particularly after prolonged VF, although hearts were not ischemic or acidotic during and after VF (unchanged coronary flow, myocardial oxygen consumption, and pH of the coronary effluent). This reduction was associated with VF-induced myocyte Ca2+ overload and increasing or decreasing Ca2+ overload during VF (using 1 microM diltiazem or 6 mM extracellular calcium) led to parallel changes of myofilament Ca2+ responsiveness. However, myofilament Ca2+ responsiveness was not associated with the defibrillation shock energy (range 0.1-15.0 J/g wet heart weight). CONCLUSION: Postfibrillatory myocardial dysfunction can be caused by reduced myofilament Ca2+ responsiveness after VF-induced myocyte Ca2+ overload. Electrical defibrillation shocks (up to 15 J/g wet heart weight), however, do not significantly contribute to this dysfunction. Our findings suggest that early additional therapy targeting intracellular Ca2+ overload may normalize myocyte Ca2+ and partially prevent postresuscitation stunning.