Christophe Garweg

Efficacy of radiofrequency catheter ablation in athletes with atrial fibrillation

AIMS Endurance sports activities have been associated with the development of atrial fibrillation (AF). Pulmonary vein isolation (PVI) by means of radiofrequency catheter ablation has been established as an effective treatment for AF. The aim of the present study was to analyse the efficacy of AF ablation in athletes. METHODS AND RESULTS We compared procedural outcome and median term follow-up in 94 consecutive athletes (>3 h of sports/week for ≥ 10 years or ≥ 1500 h lifetime) who underwent PVI (94% men, 51 ± 8 years, 87% paroxysmal AF, left atrial (LA) diameter 40 ± 8 mm, mean follow-up 41 months), and 41 contemporary controls. Sixty-three per cent of athletes performed endurance sports (running, cycling, swimming, and rowing). Documented focal induction of AF and failed treatment with ≥ 1 anti-arrhythmic drug were pre-requisites for selection of ablation treatment. Patients with long-standing persistent or permanent AF or an LA diameter ≥ 55 mm were not considered for ablation. Median lifetime cumulative hours of sports was 8638 (4175-13 688) in athletes vs. 450 (280-600) in controls (P < 0.001). Other baseline characteristics except for gender (94 vs. 66% men, respectively, P < 0.001) were comparable between both groups, as was the total number of ablation procedures per patient (1.2 ± 0.5, P = 0.62). Survival analysis showed similar AF recurrence rate after a first ablation for controls and endurance athletes, though non-endurance athletes had a significantly higher AF recurrence rate (48 vs. 46 vs. 34% freedom from AF at 3 year follow-up after a single ablation, P= 0.04). Final outcome after all ablations was similar (87 vs. 84 vs. 85% freedom from AF at 3-year follow-up, P = 0.88). No other independent predictor for AF recurrence was identified. CONCLUSION In patients with documented focal induction of non-permanent AF and absence of structural heart disease, PVI is as effective in endurance athletes as in other patients.

Which QT Correction Formulae to Use for QT Monitoring

Background Drug safety precautions recommend monitoring of the corrected QT interval. To determine which QT correction formula to use in an automated QT‐monitoring algorithm in our electronic medical record, we studied rate correction performance of different QT correction formulae and their impact on risk assessment for mortality. Methods and Results All electrocardiograms (ECGs) in patients >18 years with sinus rhythm, normal QRS duration and rate <90 beats per minute (bpm) in the University Hospitals of Leuven (Leuven, Belgium) during a 2‐month period were included. QT correction was performed with Bazett, Fridericia, Framingham, Hodges, and Rautaharju formulae. In total, 6609 patients were included (age, 59.8±16.2 years; 53.6% male and heart rate 68.8±10.6 bpm). Optimal rate correction was observed using Fridericia and Framingham; Bazett performed worst. A healthy subset showed 99% upper limits of normal for Bazett above current clinical standards: men 472 ms (95% CI, 464–478 ms) and women 482 ms (95% CI 474–490 ms). Multivariate Cox regression, including age, heart rate, and prolonged QTc, identified Framingham (hazard ratio [HR], 7.31; 95% CI, 4.10–13.05) and Fridericia (HR, 5.95; 95% CI, 3.34–10.60) as significantly better predictors of 30‐day all‐cause mortality than Bazett (HR, 4.49; 95% CI, 2.31–8.74). In a point‐prevalence study with haloperidol, the number of patients classified to be at risk for possibly harmful QT prolongation could be reduced by 50% using optimal QT rate correction. Conclusions Fridericia and Framingham correction formulae showed the best rate correction and significantly improved prediction of 30‐day and 1‐year mortality. With current clinical standards, Bazett overestimated the number of patients with potential dangerous QTc prolongation, which could lead to unnecessary safety measurements as withholding the patient of first‐choice medication.

Cardiac three-dimensional rotational angiography can be performed with low radiation dose while preserving image quality

AIMS The effective radiation dose (ED) of three-dimensional rotational angiography (3DRA) is 5-8 mSv, leading to reticence on its use. We evaluated the potential of 3DRA with a reduced number of frames (RNF) and a reduced dose per frame. METHODS AND RESULTS Three-dimensional rotational angiography was performed in 60 patients (52.5 ± 9.6 years, 16 females) referred for ablation in the right (RA; n = 10) and left atrium (LA; n = 50). In a simulation group (n = 20), the effect of dropping frames from a conventional 248 frames 3DRA LA acquisition was simulated. In a prospective group (n = 40), RNF 3DRA were acquired of LA (n = 30) and RA (n = 10) with 67 frames (0.24 Gy/frame) and 45 frames (0.12 μGy/frame), respectively. Accuracy was evaluated qualitatively and quantitatively. Effective radiation dose was determined by Monte Carlo simulation on every frame. In the simulation group, surface errors increased minimally and non-significantly when reducing frames from 248 to 124, 83, 62, 50, 42, and 31: 0.49 ± 0.51, 0.52 ± 0.46, 0.61 ± 0.49, 0.62 ± 0.47, 0.71 ± 0.48, and 0.81 ± 0.47 mm, respectively (Pearson coefficient 0.20). All 3D LA images were clinically useful, even with only 31 frames. In the prospective group, good or optimal 3D image quality was achieved in 80% of LA and all of RA reconstructions. These accurate models were obtained with ED of 2.6 ± 0.4 mSv for LA and 1.2 ± 0.5 mSv for RA. CONCLUSION Three-dimensional rotational angiography is possible with a significant reduction in ED (to the level of prospectively gated cardiac computed X-ray tomography) without compromising image quality. Low-dose 3DRA could become the preferred online 3D imaging modality for pulmonary vein isolation and other anatomy-dependent ablations.

Changes in Implantation Patterns and Therapy Rates of Implantable Cardioverter Defibrillators over Time in Ischemic and Dilated Cardiomyopathy Patients.

Clinical guidelines on implantable cardioverter defibrillator (ICD) therapy changed significantly in the last decades with potential inherent effects on therapy efficacy. We aimed to study therapy rates in time and the association between therapies and mortality.

Asymmetric collimation can significantly reduce patient radiation dose during pulmonary vein isolation.

AIMS Current fluoroscopic and 3D image-guided treatment of atrial fibrillation (AF) by radiofrequency ablation is characterized by a substantial amount of X-ray radiation. We investigated the potential of an asymmetric collimation technique to reduce dose. METHODS AND RESULTS For 30 patients, referred for AF ablation, we determined the received fluoroscopy dose for various collimation scenarios: a single collimation window encompassing all veins as used in most labs (Sc 1), an optimal adjusted symmetric collimation window encompassing each two ipsilateral veins (Sc 2) or each individual vein (Sc 3) and an optimal asymmetric collimation window encompassing each two ipsilateral veins (Sc 4) or each individual vein (Sc 5). Twenty patients were studied retrospectively and 10 were studied prospectively. Total fluoroscopy effective dose for all collimation strategies amounted to 45 ± 31 mSv for a single collimation field (Sc 1), 36 ± 25 mSv (Sc 2), and 24 ± 14 mSv (Sc 3) for a symmetrically adjusted collimation window and 15 ± 10 (Sc 4) and 5 ± 3 mSv (Sc 5) for an asymmetrically adjusted collimation approach. Validation of symmetric (Sc 2) and asymmetric (Sc 4) collimation in 10 patients confirmed the retrospective analysis. CONCLUSIONS Implementation and effective application of an optimal asymmetric collimation approach would yield an average three- to nine-fold reduction of fluoroscopy dose during AF ablation procedures. This reduction exceeds what has been previously reported by implementing an electromagnetic catheter tracking approach. Furthermore, it can be easily integrated in the clinical workflow with limited additional one-time cost. Manufacturers of imaging systems should consider its implementation a priority, and physicians should adopt it in their workflow.

Inferior and anterior QRS fragmentation have different prognostic value in patients who received an implantable defibrillator in primary prevention of sudden cardiac death

AIMS QRS fragmentation (fQRS) has been proposed as a predictor of sudden cardiac death (SCD) and all-cause mortality in ischemic (ICM) and non-ischemic cardiomyopathy patients. However the value of fQRS in patients with a LVEF <35% is a matter of debate. METHODS All consecutive patients with an indication for an ICD in primary prevention of SCD were included in a retrospective registry from 1996 until 2013. Twelve lead electrocardiograms before implant were analyzed for the presence of fQRS in different regions. Adjusted Cox regression analysis for first appropriate ICD shock (AS) and all-cause mortality was performed. RESULTS In total 407 patients were included with a mean follow-up of 4.2±3.3y (age 60.6±11.9y, 15.7% female and 52.8% ICM). fQRS was present in 46.7% of patients, predominantly inferior (30.7%) followed by anterior (21.4%) and lateral (11.1%) coronary artery territories. fQRS was significantly more prevalent in ICM (p=0.004). Inferior fQRS was an independent predictor of a first AS within 1y (HR 2.55, 95%CI 1.28-5.07) and 3y (HR 1.90, 95%CI 1.14-3.18) after implantation. Whereas, anterior fQRS was an independent predictor of all-cause mortality within 1y (HR 4.58, 95%CI 1.29-16.19), 3y (HR 3.92, 95%CI 1.77-8.65) and the complete follow-up (HR 2.22, 95%CI 1.33-3.69). Lateral fQRS was only a predictor of late (>3y of follow-up) all-cause mortality (HR 2.04, 95%CI 1.09-3.81). CONCLUSIONS fQRS in a specific coronary artery territory might be promising to discriminate arrhythmic from mortality risk. Inferior fQRS was a predictor of early arrhythmia, while anterior fQRS was related to mortality.

Multi-phase rotational angiography of the left ventricle to assist ablations: feasibility and accuracy of novel imaging.

AIMS Interventional left ventricular (LV) procedures integrating static 3D anatomy visualization are subject to mismatch with dynamic catheter movements due to prominent LV motion. We aimed to evaluate the accuracy of a recently developed acquisition and post-processing protocol for low radiation dose LV multi-phase rotational angiography (4DRA) in patients. METHODS AND RESULTS 4DRA image acquisition of the LV was performed as investigational acquisition in patients undergoing left-sided ablation (11 men; BMI = 24.7 ± 2.5 kg/m²). Iodine contrast was injected in the LA, while pacing from the RA at a cycle length of 700 ms. 4DRA acquisition and reconstruction were possible in all 11 studies. Reconstructed images were post-processed using streak artefact reduction algorithms and an interphase registration-based filtering method, increasing contrast-to-noise ratio by a factor 8.2 ± 2.1. This enabled semi-automatic segmentation, yielding LV models of five equidistant phases per cardiac cycle. For evaluation, off-line 4DRA fluoroscopy registration was performed, and the 4DRA LV contours of the different phases were compared with the contours of five corresponding phases of biplane LV angiography, acquired in identical circumstances. Of the distances between these contours, 95% were <4 mm in both incidences. Effective radiation dose for 4DRA, calculated by patient-specific Monte-Carlo simulation, was 5.1 ± 1.1 mSv. CONCLUSION Creation of 4DRA LV models in man is feasible at near-physiological heart rate and with clinically acceptable radiation dose. They showed high accuracy with respect to LV angiography in RAO and LAO. The presented technology not only opens perspectives for full cardiac cycle dynamic anatomical guidance during interventional procedures, but also for 3DRA without need for very rapid pacing.

Twiddler syndrome causing an inappropriate implantable cardioverter-defibrillator shock

A 72-year-old man was implanted with a dual-chamber cardioverter defibrillator (Lumax 540-HFT, Biotronik, Germany, Berlin) in secondary prevention. An atrial active fixation lead (Biotronik Solia S53) and a ventricular active fixation lead (Biotronik Linox S65) were used. Predischarge an X-ray showed a good position of both leads ( Panel A ) and the internal cardioverter defibrillator was checked and functioned correctly. The patient was followed on remote …

Individualized corrected QT interval is superior to QT interval corrected using the Bazett formula in predicting mutation carriage in families with long QT syndrome

BACKGROUND Long QT syndrome (LQTS) is characterized by reduced penetrance and variable QT prolongation over time, resulting in an estimate of 25% carriers of a pathogenic mutation with a normal corrected QT (QTc) interval on the resting electrocardiogram (ECG). OBJECTIVE The purpose of this study was to test the hypothesis that an individualized corrected QT interval derived from 24-hour Holter data more accurately predicts carriage of a pathogenic LQTS mutation than did QT derived from a standard 12-lead ECG and corrected using the Bazett formula (QTc interval). METHODS Carriers of a pathogenic LQTS mutation and their genotype-negative family members who had both resting ECG and Holter recordings available were included. Automated and manual measurements of QTc were performed. QTi was derived from 24-hour Holter recordings and defined as the QT value at the intersection of an RR interval of 1000 ms, with the linear regression line fitted through QT-RR data points of each individual patient. RESULTS In total, 69 patients with LQTS (23 long QT type 1, 39 long QT type 2, and 7 long QT type 3) and 55 controls were selected. Demographic characteristics were comparable. A comparison of the receiver operating characteristic curves indicates that the test added diagnostic value compared to manual measurement (P = .02) or automated measurement (P = .005). The diagnostic accuracy of manually measured QTc using conventional cutoff criteria was 72%, while it was 92% using a sex-independent QTi cutoff of 445 ms. This was caused by a 39% increase in sensitivity without compromising the specificity. CONCLUSION QTi derived from Holter recordings is superior to conventional QTc measured from a standard 12-lead ECG in predicting the mutation carrier state in families with LQTS.

Response of Robyns to the Tse's letter to editor

Dear Editor, We would like to thank Gary Tse and Bryan P. Yan for their interest in our research regarding the index of electrophysiological balance (iCEB), a novel marker of arrhythmic risk (Lu, Yan, & Gallacher, 2013; Robyns et al., 2016). We illustrated that QT/QRS is a simple surrogate for cardiac wavelength that otherwise can only be measured from invasive recordings. Cardiac wavelength plays an important role in arrhythmogenesis, and therefore, an ECG surrogate of wavelength is an interesting tool with potential large interest for clinical practice. We showed that iCEB is reduced in conditions with increased propensity for nontorsadogenic ventricular fibrillation (patients with Brugada syndrome and flecainide use) and that iCEB is increased in conditions with increased risk for torsadogenic ventricular fibrillation (long QT syndrome and sotalol use). In their letter to the editor, Tse and Yan highlight their description of novel markers in a recent issue of europace and present two additional novel risk markers (Tse & Yan, 2017, 2016). The similarity between iCEB and these novel markers is that they are based on inclusion of both a repolarization and a depolarization parameter. The first two markers (TpTe/QRS and TpTe/(QT × QRS)) include TpTe instead of QT, based on the fact that TpTe is probably a better marker for increased risk of sudden death compared to the QT interval (Tse & Yan, 2017). The markers they propose in their letter to the editor include the addition of QRS dispersion in their formula. Again, based on the fact that QRS dispersion is a marker of conduction velocity dispersion which might be a better marker for increased risk compared to QRS (Yamada et al., 2004). We do agree that these are interesting markers to evaluate; however, our main antagonism is that, compared to iCEB, it is not based on any pathophysiological background such as cardiac wavelength. Indeed, TpTe is related to transmural or global dispersion of repolarization (Izumi et al., 2012; Yan & Antzelevitch, 1998). Replacing QT by TpTe therefore moves away from the idea to measure cardiac wavelength from the surface ECG. Furthermore, as Tse and Yan correctly underline, none of these parameters have been clinically evaluated. Therefore, we tested in our described cohort of patients with long QT syndrome and Brugada syndrome and individuals started on either flecainide or sotalol whether the parameters including TpTe show any signal. Similar to iCEB, the two parameters proposed by Tse are decreased in Brugada syndrome and increased in long QT syndrome (Table 1). However, the overlap between controls and patients with BrS is larger with TpTe/QRS compared to iCEB (post hoc pvalue only .12 for TpTe/QRS compared to <.001 for iCEB). In individuals started on flecainide or sotalol on the other hand, there is no significant difference in the parameters proposed by Tse in contrast to iCEB (Table 2). To conclude, in our population of patients with arrhythmogenic heart disease, the parameters proposed by Tse including TpTe are similarly altered as iCEB, while they do not show any signal in patients started on drugs with potential proarrhythmic effect. Further evaluation of these parameters in large patient cohorts with endpoints of sudden death is required to establish their role in risk stratification.