Radiofrequency (RF) ablation represents a standard of care for pulmonary vein isolation in patients with drug-refractory paroxysmal atrial fibrillation (AF). In this setting, cryoballoon (CB) ...ablation has emerged as alternative therapy. However, the efficacy and safety of CB vs. RF ablation in patients with paroxysmal AF remain a matter of debate.
We searched electronic scientific databases for studies of CB vs. RF ablation in patients with paroxysmal AF. Aggregate data were pooled to perform a meta-analysis. The primary efficacy and safety outcomes were the recurrence of any atrial arrhythmia and procedure-related complications, respectively. A total of 6473 participants from 10 studies (CB, n = 2232 vs. RF, n = 4241) were studied. After a median follow-up of 16 months, the risk of any atrial arrhythmia recurrence (risk ratio, RR 95% confidence interval 95% CI = 1.01 0.90-1.14, P = 0.83) and procedure-related complications (RR 95% CI = 0.92 0.66-1.28, P = 0.61) were comparable between CB vs. RF ablation. Cryoballoon ablation led to a higher risk of persistent phrenic nerve palsy (RR 95% CI = 13.60 3.87-47.81, P < 0.01) and a lower risk of cardiac tamponade (RR 95% CI = 0.48 0.25-0.89, P = 0.02) compared with RF ablation. There was a trend of statistically significant interaction between the type of CB and the duration of ablation (P for interaction = 0.09).
In patients with paroxysmal AF, ablation therapy with CB is associated with efficacy and safety comparable to that of RF. Second-generation CB catheters seem to reduce procedure duration. Further studies are warranted to disclose the impact of second-generation CB catheters compared with RF for ablation of paroxysmal AF.
Background
Compared with surgical aortic valve replacement, transcatheter aortic valve implantation (TAVI) is associated with a higher risk of developing a new conduction disorder that necessitates ...permanent pacemaker implantation (PM). The most frequently observed conduction disorder is left bundle branch block (LBBB), which impairs left ventricular function.
Objectives
The primary objective of this study was to assess the incidence and prognostic significance of persistent new-onset LBBB following TAVI. Factors predictive of persistent new-onset LBBB were also explored.
Methods
This study included a total of 793 patients who underwent TAVI between May 2008 and April 2012. Patients were divided into two groups: those with persistent new-onset LBBB and those without persistent new-onset LBBB. Follow-up was conducted within 1-year of TAVI.
Results
Persistent new-onset LBBB was observed in 31.1 % (
n
= 197) out of 634 eligible patients. At 30 days and 1-year post-TAVI, the all-cause mortality rate was higher in patients with persistent new-onset LBBB (6.1 %,
n
= 12 and 20.8 %,
n
= 41, respectively) than in patients without new-onset LBBB (3.3 %,
n
= 10 and 13.0 %,
n
= 57, respectively;
p
= 0.014 and
p
= 0.010 for the two time points). Multivariate regression analyses revealed, that persistent new-onset LBBB was an independent predictor of all-cause mortality at 1 year (HR 1.84, 95 %CI 1.35–2.02). PM implantation was observed slightly more frequently in patients with persistent new-onset LBBB (14.2 %) than in those without (9.4 %; HR 1.60, 95 %CI 0.96–2.67). Risk factors for pacemaker (PM) were baseline RBBB (HR 6.23, 95 %CI 3.76–10.33), chronic atrial fibrillation (HR 1.75, 95 %CI 1.10–2.56) and the Medtronic CoreValve implantation (HR 2.40, 95 %CI 1.55–3.75). At 1-year follow-up, the mean survival of patients with PM (81.2 %) was slightly lower, but not significantly different from that of patients without PM (85.0 %;
p
= 0.377). Upon multivariable logistic binary regression analysis Medtronic CoreValve was associated with an increase rate of persistent new-onset LBBB (HR 2.52, 95 %CI 1.67–3.80) and PM implantation. Mortality during 1 year of follow-up, however, was neither increased in the total population (
p
= 0.232), nor in a subgroup of those with LBBB in a comparison of Medtronic CoreValve and Edwards SAPIEN.
Conclusion
This study demonstrated that persistent new-onset LBBB was associated with increased mortality in patients undergoing TAVI. Compared with the Edwards SAPIEN valve, implantation of the Medtronic CoreValve resulted in a higher rate of both persistent new-onset LBBB and PM but not death.
Background
Several observational studies have suggested a worrying reduction in hospitalisations for acute coronary syndromes in the emergency cardiology department in the last few months all over ...the world. The aim of the present study is to assess the impact of the current COVID-19 health crisis on admission for acute coronary syndrome (ACS) in the cardiology department of a tertiary general hospital in Germany with a COVID-19 ward.
Methods and results
The authors retrieved clinical data evaluating consecutive patients with ACS admitted to their emergency cardiology department. Data from January to June 2020, as well as for a 5-week period corresponding to this yearʼs COVID-19 outbreak in south-west Germany (23rd March–26th April), were analysed and compared to data from equivalent weeks in the previous 2 years. A trend of reduction in admissions for ACS was observed from the beginning of the outbreak in the region at the end of March 2020. This trend continued and even intensified after a fall in COVID-19 cases in the area; the number of ACS patients in April 2020 was 25% and in June 29% lower than in January 2020 (
p
-value for linear trend <0.001). An even more consistent reduction was observed as compared with the equivalent weeks in the previous 2 years (38% and 30% lower than in 2019 and 2018, respectively;
p
= 0.009).
Conclusions
The COVID-19 health and social crisis has caused a worrying trend of reduced cardiological admissions for ACS, without evidence of a decrease in its incidence. Understanding and counteracting the causes appears to be crucial to avoiding major long-term consequences for healthcare systems worldwide.
Atypical atrial flutter (AFlut) is a reentrant arrhythmia which patients frequently develop after ablation for atrial fibrillation (AF). Indeed, substrate modifications during AF ablation can ...increase the likelihood to develop AFlut and it is clinically not feasible to reliably and sensitively test if a patient is vulnerable to AFlut. Here, we present a novel method based on personalized computational models to identify pathways along which AFlut can be sustained in an individual patient. We build a personalized model of atrial excitation propagation considering the anatomy as well as the spatial distribution of anisotropic conduction velocity and repolarization characteristics based on a combination of a priori knowledge on the population level and information derived from measurements performed in the individual patient. The fast marching scheme is employed to compute activation times for stimuli from all parts of the atria. Potential flutter pathways are then identified by tracing loops from wave front collision sites and constricting them using a geometric snake approach under consideration of the heterogeneous wavelength condition. In this way, all pathways along which AFlut can be sustained are identified. Flutter pathways can be instantiated by using an eikonal-diffusion phase extrapolation approach and a dynamic multifront fast marching simulation. In these dynamic simulations, the initial pattern eventually turns into the one driven by the dominant pathway, which is the only pathway that can be observed clinically. We assessed the sensitivity of the flutter pathway maps with respect to conduction velocity and its anisotropy. Moreover, we demonstrate the application of tailored models considering disease-specific repolarization properties (healthy, AF-remodeled, potassium channel mutations) as well as applicabiltiy on a clinical dataset. Finally, we tested how AFlut vulnerability of these substrates is modulated by exemplary antiarrhythmic drugs (amiodarone, dronedarone). Our novel method allows to assess the vulnerability of an individual patient to develop AFlut based on the personal anatomical, electrophysiological, and pharmacological characteristics. In contrast to clinical electrophysiological studies, our computational approach provides the means to identify all possible AFlut pathways and not just the currently dominant one. This allows to consider all relevant AFlut pathways when tailoring clinical ablation therapy in order to reduce the development and recurrence of AFlut.
Atrial flutter (AFL) is a common atrial arrhythmia typically characterized by electrical activity propagating around specific anatomical regions. It is usually treated with catheter ablation. ...However, the identification of rotational activities is not straightforward, and requires an intense effort during the first phase of the electrophysiological (EP) study, i.e., the mapping phase, in which an anatomical 3D model is built and electrograms (EGMs) are recorded. In this study, we modeled the electrical propagation pattern of AFL (measured during mapping) using network theory (NT), a well-known field of research from the computer science domain. The main advantage of NT is the large number of available algorithms that can efficiently analyze the network. Using directed network mapping, we employed a cycle-finding algorithm to detect all cycles in the network, resembling the main propagation pattern of AFL. The method was tested on two subjects in sinus rhythm, six in an experimental model of
simulations, and 10 subjects diagnosed with AFL who underwent a catheter ablation. The algorithm correctly detected the electrical propagation of both sinus rhythm cases and
simulations. Regarding the AFL cases, arrhythmia mechanisms were either totally or partially identified in most of the cases (8 out of 10), i.e., cycles around the mitral valve, tricuspid valve and figure-of-eight reentries. The other two cases presented a poor mapping quality or a major complexity related to previous ablations, large areas of fibrotic tissue, etc. Directed network mapping represents an innovative tool that showed promising results in identifying AFL mechanisms in an automatic fashion. Further investigations are needed to assess the reliability of the method in different clinical scenarios.
Robust and exact automatic P wave detection and delineation in the electrocardiogram (ECG) is still an interesting but challenging research topic. The early prognosis of cardiac afflictions such as ...atrial fibrillation and the response of a patient to a given treatment is believed to improve if the P wave is carefully analyzed during sinus rhythm. Manual annotation of the signals is a tedious and subjective task. Its correctness depends on the experience of the annotator, quality of the signal, and ECG lead. In this work, we present a wavelet-based algorithm to detect and delineate P waves in individual ECG leads. We evaluated a large group of commonly used wavelets and frequency bands (wavelet levels) and introduced a special phase free wavelet transformation. The local extrema of the transformed signals are directly related to the delineating points of the P wave. First, the algorithm was studied using synthetic signals. Then, the optimal parameter configuration was found using intracardiac electrograms and surface ECGs measured simultaneously. The reverse biorthogonal wavelet 3.3 was found to be optimal for this application. In the end, the method was validated using the QT database from PhysioNet. We showed that the algorithm works more accurately and more robustly than other methods presented in literature. The validation study delivered an average delineation error of the P wave onset of -0.32±12.41 ms when compared to manual annotations. In conclusion, the algorithm is suitable for handling varying P wave shapes and low signal-to-noise ratios.
There is evidence that rotors could be drivers that maintain atrial fibrillation. Complex fractionated atrial electrograms have been located in rotor tip areas. However, the concept of electrogram ...fractionation, defined using time intervals, is still controversial as a tool for locating target sites for ablation. We hypothesize that the fractionation phenomenon is better described using non-linear dynamic measures, such as approximate entropy, and that this tool could be used for locating the rotor tip. The aim of this work has been to determine the relationship between approximate entropy and fractionated electrograms, and to develop a new tool for rotor mapping based on fractionation levels. Two episodes of chronic atrial fibrillation were simulated in a 3D human atrial model, in which rotors were observed. Dynamic approximate entropy maps were calculated using unipolar electrogram signals generated over the whole surface of the 3D atrial model. In addition, we optimized the approximate entropy calculation using two real multi-center databases of fractionated electrogram signals, labeled in 4 levels of fractionation. We found that the values of approximate entropy and the levels of fractionation are positively correlated. This allows the dynamic approximate entropy maps to localize the tips from stable and meandering rotors. Furthermore, we assessed the optimized approximate entropy using bipolar electrograms generated over a vicinity enclosing a rotor, achieving rotor detection. Our results suggest that high approximate entropy values are able to detect a high level of fractionation and to locate rotor tips in simulated atrial fibrillation episodes. We suggest that dynamic approximate entropy maps could become a tool for atrial fibrillation rotor mapping.
The treatment of atrial fibrillation and other cardiac arrhythmias as a major cause of cardiovascular hospitalization has remained a challenge predominantly for patients with severely remodeled ...substrate. Individualized ablation strategies are extremely important both for pulmonary vein isolation and subsequent ablations. Current approaches to identifying arrhythmogenic regions rely on electrogram-based features such as activation time and voltage. Novel technologies now enable clinical assessment of the local impedance as tissue property. Previous studies demonstrated its use for ablation monitoring and indicated its potential to differentiate healthy substrate, scar, and pathological tissue. This study investigates the potential of local electrical impedance-based substrate mapping of the atria for human
data. The presented pipeline for impedance mapping particularly contains options for dealing with undesirable effects originating from cardiac motion, catheter motion, or proximity to other intracardiac devices. Bloodpool impedance was automatically determined as a patient-specific reference. Full-chamber, left atrial impedance maps were drawn up from interpolating the measured impedances to the atrial endocardium. Finally, the origin and magnitude of oscillations of the raw impedance recording were probed into. The most dominant reason for exclusion of impedance samples was the loss of endocardial contact. With median elevations above the bloodpool impedance between 29 and 46 Ω, the impedance within the pulmonary veins significantly exceeded the remaining atrial walls presenting median elevations above the bloodpool impedance between 16 and 20 Ω. Previous ablation lesions were distinguished from their surroundings by a significant drop in local impedance while the corresponding regions did not differ for the control group. The raw impedance was found to oscillate with median amplitudes between 6 and 17 Ω depending on the patient. Oscillations were traced back to an interplay of atrial, ventricular, and respiratory motion. In summary, local impedance measurements demonstrated their capability to distinguish pathological atrial tissue from physiological substrate. Methods to limit the influence of confounding factors that still hinder impedance mapping were presented. Measurements at different frequencies or the combination of multiple electrodes could lead to further improvement. The presented examples indicate that electrogram- and impedance-based substrate mapping have the potential to complement each other toward better patient outcomes in future.
The incidence of atrial tachycardia steadily increases in industrial nations. During invasive electrophysiological studies, a catheter measures electrograms within the atrium to assist detailed ...diagnosis and treatment planning. With unipolar and bipolar electrograms, two different acquisition modes are clinically available. Unipolar electrograms have several advantages over bipolar electrograms. However, unipolar electrograms are more affected by noise and the ventricular far field. Therefore, only bipolar electrograms are typically used in clinical settings. A recently published ventricular far field removal technique models the ventricular far field by a set of dipoles and yielded promising results in a simulation study. However, the method lacks quantitative clinical validation. Therefore, we adapted the technique to clinical needs and applied it to data sets of two patients using four different lengths of the removal window. Results were compared quantitatively by a tailored residual error measure. The used method resulted in a median reduction of the ventricular far field by approximately 89% using a removal window of optimal length for both patients. The results showed that the dipole method provides an alternative to other VFF removal techniques in clinical practice because it can reveal AA originally hidden by VFF without leading to a prolongation of the electrophysiological study.
Rate-varying S1S2 stimulation protocols can be used for restitution studies to characterize atrial substrate, ionic remodeling, and atrial fibrillation risk. Clinical restitution studies with ...numerous patients create large amounts of these data. Thus, an automated pipeline to evaluate clinically acquired S1S2 stimulation protocol data necessitates consistent, robust, reproducible, and precise evaluation of local activation times, electrogram amplitude, and conduction velocity. Here, we present the CVAR-Seg pipeline, developed focusing on three challenges: (i) No previous knowledge of the stimulation parameters is available, thus, arbitrary protocols are supported. (ii) The pipeline remains robust under different noise conditions. (iii) The pipeline supports segmentation of atrial activities in close temporal proximity to the stimulation artifact, which is challenging due to larger amplitude and slope of the stimulus compared to the atrial activity.
The S1 basic cycle length was estimated by time interval detection. Stimulation time windows were segmented by detecting synchronous peaks in different channels surpassing an amplitude threshold and identifying time intervals between detected stimuli. Elimination of the stimulation artifact by a matched filter allowed detection of local activation times in temporal proximity. A non-linear signal energy operator was used to segment periods of atrial activity. Geodesic and Euclidean inter electrode distances allowed approximation of conduction velocity. The automatic segmentation performance of the CVAR-Seg pipeline was evaluated on 37 synthetic datasets with decreasing signal-to-noise ratios. Noise was modeled by reconstructing the frequency spectrum of clinical noise. The pipeline retained a median local activation time error below a single sample (1 ms) for signal-to-noise ratios as low as 0 dB representing a high clinical noise level. As a proof of concept, the pipeline was tested on a CARTO case of a paroxysmal atrial fibrillation patient and yielded plausible restitution curves for conduction speed and amplitude.
The proposed openly available CVAR-Seg pipeline promises fast, fully automated, robust, and accurate evaluations of atrial signals even with low signal-to-noise ratios. This is achieved by solving the proximity problem of stimulation and atrial activity to enable standardized evaluation without introducing human bias for large data sets.
PDF
