Marcio Sturmer

Reduced risk for inappropriate implantable cardioverter-defibrillator shocks with dual-chamber therapy compared with single-chamber therapy: results of the randomized OPTION study.

OBJECTIVES The OPTION (Optimal Anti-Tachycardia Therapy in Implantable Cardioverter-Defibrillator Patients Without Pacing Indications) trial sought to compare long-term rates of inappropriate shocks, mortality, and morbidity between dual-chamber and single-chamber settings in implantable cardioverter-defibrillators (ICDs) patients. BACKGROUND The use of dual-chamber ICDs potentially allows better discrimination of supraventricular arrhythmias and thereby reduces inappropriate shocks. However, it may lead to detrimental ventricular pacing. METHODS This prospective multicenter, single-blinded trial enrolled 462 patients with de novo primary or secondary prevention indications for ICD placement and with left ventricular ejection fractions ≤40% despite optimal tolerated pharmacotherapy. All patients received atrial leads and dual-chamber defibrillators that were randomized to be programmed either with dual-chamber or single-chamber settings. In the dual-chamber setting arm, the PARAD+ algorithm, which differentiates supraventricular from ventricular arrhythmias, and SafeR mode, to minimize ventricular pacing, were activated. In the single-chamber setting arm, the acceleration, stability, and long cycle search discrimination criteria were activated, and pacing was set to VVI 40 beats/min. Ventricular tachycardia detection was required at rates between 170 and 200 beats/min, and ventricular fibrillation detection was activated above 200 beats/min. RESULTS During a follow-up period of 27 months, the time to the first inappropriate shock was significantly longer in the dual-chamber setting arm (p = 0.012, log-rank test), and 4.3% of patients in the dual-chamber setting group compared with 10.3% in the single-chamber setting group experienced inappropriate shocks (p = 0.015). Rates of all-cause death or cardiovascular hospitalization were 20% for the dual-chamber setting group and 22.4% for the single-chamber setting group and satisfied the pre-defined margin for equivalence (p < 0.001). CONCLUSIONS Therapy with dual-chamber settings for ICD discrimination combined with algorithms for minimizing ventricular pacing was associated with reduced risk for inappropriate shock compared with single-chamber settings, without increases in mortality and morbidity. (Optimal Anti-Tachycardia Therapy in Implantable Cardioverter-Defibrillator [ICD] Patients Without Pacing Indications [OPTION]; NCT00729703).

Anticoagulation Management Pre- and Post Atrial Fibrillation Ablation: A Survey of Canadian Centres

BACKGROUND Anticoagulation in patients undergoing atrial fibrillation (AF) ablation is crucial to minimize the risk of thromboembolic complications. There are broad ranges of approaches to anticoagulation management pre and post AF ablation procedures. The purpose of this study was to determine the anticoagulation strategies currently in use in patients peri- and post AF ablation in Canada. METHODS A Web-based national survey of electrophysiologists performing AF ablation in Canada collected data regarding anticoagulation practice prior to ablation, periprocedural bridging, and duration of postablation anticoagulation. RESULTS The survey was completed by 36 (97%) of the 37 electrophysiologists performing AF ablation across Canada. Prior to AF ablation, 58% of electrophysiologists started anticoagulation for patients with paroxysmal AF CHADS(2) scores of 0 to 1, 92% for paroxysmal AF CHADS(2) scores ≥ 2, 83% for persistent AF CHADS(2) scores of 0 to 1, and 97% for persistent AF CHADS(2) scores ≥ 2. For patients with CHADS(2) 0 to 1, warfarin was continued for at least 3 months by most physicians (89% for paroxysmal and 94% for persistent AF). For patients with CHADS(2) ≥ 2 and with no recurrence of AF at 1 year post ablation, 89% of physicians continued warfarin. CONCLUSIONS Although guidelines recommend long-term anticoagulation in patients with CHADS(2) ≥ 2, 11% of physicians would discontinue warfarin in patients with no evidence of recurrent AF 1 year post successful ablation. Significant heterogeneity exists regarding periprocedural anticoagulation management in clinical practice. Clinical trial evidence is required to guide optimal periprocedural anticoagulation and therapeutic decisions regarding long-term anticoagulation after an apparently successful catheter ablation for AF.

Evaluation of a subject-specific transfer-function-based nonlinear QT interval rate-correction method.

The QT interval in the electrocardiogram (ECG) is a measure of total duration of depolarization and repolarization. Correction for heart rate is necessary to provide a single intrinsic physiological value that can be compared between subjects and within the same subject under different conditions. Standard formulas for the corrected QT (QTc) do not fully reproduce the complexity of the dependence in the preceding interbeat intervals (RR) and inter-subject variability. In this paper, a subject-specific, nonlinear, transfer function-based correction method is formulated to compute the QTc from Holter ECG recordings. The model includes five parameters: three describing the static QT-RR relationship and two representing memory/hysteresis effects that intervene in the calculation of effective RR values. The parameter identification procedure is designed to minimize QTc fluctuations and enforce zero correlation between QTc and effective RR. Weighted regression is used to better handle unbalanced or skewed RR distributions. The proposed optimization approach provides a general mathematical framework for further extensions of the model. Validation, robustness evaluation and comparison with existing QT correction formulas is performed on ECG signals recorded during sinus rhythm, atrial pacing, tilt-table tests, stress tests and atrial flutter (29 subjects in total). The resulting average modeling error on the QTc is 4.9 ± 1.1 ms with a sampling interval of 2 ms, which outperforms correction formulas currently used. The results demonstrate the benefits of subject-specific rate correction and hysteresis reduction.

QT interval measurement and correction in patients with atrial flutter: a pilot study

BACKGROUND AND PURPOSE Measurement of QT intervals during atrial flutter (AFL) is relevant to monitor the safety of drug delivery. Our aim is to compare QT and QTc intervals in AFL patients before and after catheter ablation in order to validate QT measurement during AFL. METHODS 25 patients suffering from AFL underwent catheter ablation; 9 were in sinus rhythm and 16 were in AFL at the time of the procedure. Holter ECGs were continuously recorded before, during and after the procedure. In AFL signals, flutter waves were subtracted using a previously-validated deconvolution-based method. Fridericias QTc was computed before and after ablation after hysteresis reduction. RESULTS Comparing QTc values obtained before and after ablation showed that (1) the intervention did not significantly affect QTc, and (2) the QTc during AFL was concordant with the QTc value in sinus rhythm. CONCLUSION QTc can be reliably measured in patients with AFL using flutter wave subtraction and hysteresis reduction.

Extraction and Analysis of

Analysis of T waves in the ECG is an essential clinical tool for diagnosis, monitoring, and follow-up of patients with heart dysfunction. During atrial flutter, this analysis has been so far limited by the perturbation of flutter waves superimposed over the T wave. This paper presents a method based on missing data interpolation for eliminating flutter waves from the ECG during atrial flutter. To cope with the correlation between atrial and ventricular electrical activations, the CLEAN deconvolution algorithm was applied to reconstruct the spectrum of the atrial component of the ECG from signal segments corresponding to TQ intervals. The locations of these TQ intervals, where the atrial contribution is presumably dominant, were identified iteratively. The algorithm yields the extracted atrial and ventricular contributions to the ECG. Standard T-wave morphology parameters (T-wave amplitude, T peak-T end duration, QT interval) were measured. This technique was validated using synthetic signals, compared to average beat subtraction in a patient with a pacemaker, and tested on pseudo-orthogonal ECGs from patients in atrial flutter. Results demonstrated improvements in accuracy and robustness of T-wave analysis as compared to current clinical practice.

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Background:  Implantable cardioverter‐defibrillators (ICDs) represent the treatment of choice for primary and secondary prevention of sudden cardiac death but ICD therapy is also plagued by inappropriate shocks due to supraventricular tachyarrhythmias. Dual‐chamber (DC) ICDs are considered to exhibit an enhanced discrimination performance in comparison to single‐chamber (SC) ICDs, which results in reduction of inappropriate detections in a short‐ to mid‐term follow‐up. Comparative data on long‐term follow‐up and especially on inappropriate shocks are limited.

Waves in Electrocardiograms During Atrial Flutter

Implantable cardioverter defibrillator (ICD) leads are subject to technical failures and the impact of the resulting public advisories on patient welfare is unclear. The psychological status of patients who received an advisory for their Medtronic Fidelis ICD lead (Medtronic Inc., Minneapolis, MN, USA) and followed either by self‐surveillance for alarm or home monitoring with CareLink was evaluated prospectively and compared to patients with ICDs not under advisory.

Rationale and Design of the OPTION Study: Optimal Antitachycardia Therapy in ICD Patients without Pacing Indications

AIMS To quantify the sensitivity of QT heart-rate correction methods for detecting drug-induced QTc changes in thorough QT studies. METHODS Twenty-four-hour Holter ECGs were analyzed in 66 normal subjects during placebo and moxifloxacin delivery (single oral dose). QT and RR time series were extracted. Three QTc computation methods were used: (1) Fridericias formula, (2) Fridericias formula with hysteresis reduction, and (3) a subject-specific approach with transfer function-based hysteresis reduction and three-parameter non-linear fitting of the QT-RR relation. QTc distributions after placebo and moxifloxacin delivery were compared in sliding time windows using receiver operating characteristic (ROC) curves. The area under the ROC curve (AUC) served as a measure to quantify the ability of each method to detect moxifloxacin-induced QTc prolongation. RESULTS Moxifloxacin prolonged the QTc by 10.6 ± 6.6 ms at peak effect. The AUC was significantly larger after hysteresis reduction (0.87 ± 0.13 vs. 0.82 ± 0.12, p<0.01) at peak effect, indicating a better discriminating capability. Subject-specific correction further increased the AUC to 0.91 ± 0.11 (p<0.01 vs. Fridericia with hysteresis reduction). The performance of the subject-specific approach was the consequence of a substantially lower intra-subject QTc standard deviation (5.7 ± 1.1 ms vs. 8.8 ± 1.2 ms for Fridericia). CONCLUSION The ROC curve provides a tool for quantitative comparison of QT heart rate correction methods in the context of detecting drug-induced QTc prolongation. Results support a broader use of subject-specific QT correction.

Psychological Impact of Surveillance in Patients with a Defibrillator Lead under Advisory: A Prospective Evaluation

Radiofrequency (RF) ablation is effective for slow pathway ablation, but carries a risk of inadvertent AV block requiring permanent pacing. By comparison, cryoablation with a 4‐mm distal electrode catheter has not been reported to cause permanent AV block but has been shown to be less effective than RF ablation. We sought to define the safety and efficacy of a 6‐mm distal electrode cryoablation catheter for slow pathway ablation in patients with atrioventricular nodal reentry tachycardia (AVNRT).

Assessment of the sensitivity of detecting drug-induced QTc changes using subject-specific rate correction

The programming of implantable cardioverter-defibrillators (ICDs) influences inappropriate shock rates. The aim of the study is to analyse rates of patients with appropriate and inappropriate shocks according to detection zones in the OPTION trial. All patients received dual chamber (DC) ICDs randomly assigned to be programmed either to single chamber (SC) or to DC settings including PARAD+ algorithm. In a post-hoc analysis, rates of patients with inappropriate and appropriate shocks were calculated for shocks triggered at heart rates ≥170 bpm (ventricular tachycardia zone) and at rates ≥200 bpm (ventricular fibrillation zone). In the SC group, higher rates of patients with total and inappropriate shocks were delivered at heart rates ≥170 bpm than at rates ≥200 bpm (total shocks: 21.1% vs. 16.6%; p = 0.002; inappropriate shocks: 7.6% vs. 4.5%, p = 0.016; appropriate shocks: 15.2% vs. 13.5%; p = n.s.). No such differences were observed in the DC group (total shocks: 14.3% vs. 12.6%; p = n.s.; inappropriate shocks: 3.9% vs. 3.6%; p = n.s.; appropriate shocks: 12.2% vs. 10.4%; p = n.s.). The higher frequency of patients with total shocks with SC settings than with DC settings that benefit from PARAD+ was driven by a higher percentage of patients with inappropriate shocks in the VT zone (170–200 bpm) in the SC population.