Different Ventricular Fibrillation Types in Low-Dimensional Latent Spaces.

The causes of ventricular fibrillation (VF) are not yet elucidated, and it has been proposed that different mechanisms might exist. Moreover, conventional analysis methods do not seem to provide time or frequency domain features that allow for recognition of different VF patterns in electrode-recorded biopotentials. The present work aims to determine whether low-dimensional latent spaces could exhibit discriminative features for different mechanisms or conditions during VF episodes. For this purpose, manifold learning using autoencoder neural networks was analyzed based on surface ECG recordings. The recordings covered the onset of the VF episode as well as the next 6 min, and comprised an experimental database based on an animal model with five situations, including control, drug intervention (amiodarone, diltiazem, and flecainide), and autonomic nervous system blockade. The results show that latent spaces from unsupervised and supervised learning schemes yielded moderate though quite noticeable separability among the different types of VF according to their type or intervention. In particular, unsupervised schemes reached a multi-class classification accuracy of 66%, while supervised schemes improved the separability of the generated latent spaces, providing a classification accuracy of up to 74%. Thus, we conclude that manifold learning schemes can provide a valuable tool for studying different types of VF while working in low-dimensional latent spaces, as the machine-learning generated features exhibit separability among different VF types. This study confirms that latent variables are better VF descriptors than conventional time or domain features, making this technique useful in current VF research on elucidation of the underlying VF mechanisms.

Catheter ablation of ventricular arrhythmias in left ventricular noncompaction cardiomyopathy.

BACKGROUND: There are limited data on ventricular arrhythmias (VAs) associated with left ventricular noncompaction (LVNC) cardiomyopathy. OBJECTIVES: This study aims to analyze the clinical and electrocardiographic characteristics of VAs in a group of patients with LVNC. METHODS: Forty-two nonrelated patients with LVNC and VAs were included that were evaluated at the Inherited Cardiac Disease Unit of the University Hospital Virgen Arrixaca (Murcia-Spain) (ERN Guard-Heart Centre, European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart). RESULTS: Thirteen patients (30.9%) had isolated LVNC, 27 (64.3%) had LVNC associated with dilated cardiomyopathy, and 2 (4.8%) had LVNC associated with hypertrophic cardiomyopathy. Among isolated LVNC individuals, 9 (69.2%) had premature ventricular complexes (PVCs)/nonsustained ventricular tachycardias (VTs), and 4 (30.8%) VTs (1 VT degenerating in ventricular fibrillation). In the dilated cardiomyopathy group, 11 (40.7%) patients had PVCs, 14 (51.9%) VTs, and 2 (7.4%) ventricular fibrillation. In the hypertrophic cardiomyopathy group, one patient had PVCs and the other VTs. Endocardial mapping and ablation were performed in 19 patients (45.2%): 7 ventricular outflow tracts (4 right ventricular outflow tract, 1 left coronary cusp, and 2 right coronary cusp), 2 in the left ventricular summit, 5 related to Purkinje potentials at the mid inferoseptal area, and 5 associated with endocardial scar localized in the basal anterolateral and inferolateral segments. Epicardial ablation was performed in 3 cases. CONCLUSION: The substrate of VAs in LVNC cardiomyopathy is heterogeneous, with origin in ventricular outflow tracts, Purkinje system related, and resembling scar patterns in nonischemic cardiomyopathy.

Emergency department attendance and reasons for consultation after cryoballoon ablation for pulmonary vein isolation of atrial fibrillation.

INTRODUCTION AND OBJECTIVES: There are few data on emergency visits after cryoballoon-based pulmonary vein isolation. The aim of this study was to quantify emergency department visits during the first 3 months after the procedure and to identify the reasons for consultation, final diagnoses, and the therapeutic approach. METHODS: Observational, retrospective study of 330 consecutive patients undergoing a first cryoballoon-based ablation procedure. Patients were followed up for 90 days after the procedure. We recorded emergency visits, symptoms, electrocardiographic data, and the therapeutic approach. Final diagnoses were classified as rhythm disorder, confirmed complication, possible complication, and unrelated to the procedure or to the arrhythmic disorder. RESULTS: A total of 112 (34%) patients attended the emergency department, 50 (44.6%) for palpitations. Sustained atrial arrhythmias were documented in 44 (39.3%) patients. Among the 29 (25.9%) visits for complications potentially related to the procedure, 5 were confirmed inguinal puncture complications and 10 were classified as unconfirmed possible complications. Forty-one visits were unrelated to the procedure or to the arrhythmic disorder. A total of 21.4% of the visits were due to palpitations requiring no therapeutic action. CONCLUSIONS: A third of the patients attended the emergency department at least once, with the most frequent reason being arrhythmia-related symptoms. Late complications were rare and generally mild. Up to 20% of emergency visits could potentially be avoided by the availability of a teleconsulting system with remote electrocardiogram transmission.

Spectral Analysis and Mutual Information Estimation of Left and Right Intracardiac Electrograms during Ventricular Fibrillation.

Ventricular fibrillation (VF) signals are characterized by highly volatile and erratic electrical impulses, the analysis of which is difficult given the complex behavior of the heart rhythms in the left (LV) and right ventricles (RV), as sometimes shown in intracardiac recorded Electrograms (EGM). However, there are few studies that analyze VF in humans according to the simultaneous behavior of heart signals in the two ventricles. The objective of this work was to perform a spectral and a non-linear analysis of the recordings of 22 patients with Congestive Heart Failure (CHF) and clinical indication for a cardiac resynchronization device, simultaneously obtained in LV and RV during induced VF in patients with a Biventricular Implantable Cardioverter Defibrillator (BICD) Contak Renewal IVTM (Boston Sci.). The Fourier Transform was used to identify the spectral content of the first six seconds of signals recorded in the RV and LV simultaneously. In addition, measurements that were based on Information Theory were scrutinized, including Entropy and Mutual Information. The results showed that in most patients the spectral envelopes of the EGM sources of RV and LV were complex, different, and with several frequency peaks. In addition, the Dominant Frequency (DF) in the LV was higher than in the RV, while the Organization Index (OI) had the opposite trend. The entropy measurements were more regular in the RV than in the LV, thus supporting the spectral findings. We can conclude that basic stochastic processing techniques should be scrutinized with caution and from basic to elaborated techniques, but they can provide us with useful information on the biosignals from both ventricles during VF.

[Psychological adjustment in patients with an implantable cardioverter defibrillator: primary prevention and secondary prevention. A comparative study.] / Ajuste psicológico en pacientes portadores de un desfibrilador automático implantado: prevención primaria frente a prevención secundaria. Un estudio comparativo.

OBJECTIVE: The implantation of the Implantable Cardioverter Defibrillator (ICD) influences the psychological adjustment and the degree of subjective discomfort. The objective of this work was to analyze differences in psychological adjustment, fear of shocks and the degree of subjective discomfort derived from the illness depending on the reasons for implantation (primary vs secondary). METHODS: A sample of 82 patients with an ICD, for primary (58.5%) or secondary (41.5%) prevention indications was studied. A sociodemographic and clinical questionnaire and List of Brief Symptoms (LBS-50) was used. Descriptive univariate and bivariate analysis, t-tests on mean differences for independent samples and z-tests on proportion differences were performed. RESULTS: Regarding psychological adjustment, 43.9% of the patients reported to have sleeping disorder, regardless the type of prevention. A greater percentage of patients of primary prevention had scored higher in clinical scales. The 29.4% of patients with secondary prevention reported to be afraid of experiencing some shock. The 25% of patients whose type of prevention was primary showed severe or moderate level of subjective discomfort derived from the illness compared with the 14.7% of the secondary prevention patients (p=0.7). CONCLUSIONS: The patients with an ICD show symptoms clinically significant in Psychoactivity, Obsession-Compulsion, Anxiety, Somatization, Sleeping disorders and Psychopathology Risk Index. Both groups, regardless the type of prevention showed a similar psychological adjustment. Regarding the fear of shocks and the degree of subjective discomfort derived from the illness, no statistically significant differences between the groups were found.

OBJETIVO: La implantación del Desfibrilador Automático Implantado (DAI) influye en el ajuste psicológico y en el grado de malestar de los pacientes. El objetivo de este trabajo fue analizar las diferencias en el ajuste psicológico, el miedo a las descargas y el grado de malestar subjetivo derivado de la enfermedad en función del motivo de implantación (primaria frente a secundaria). METODOS: La muestra fue de 82 pacientes portadores de un DAI, tanto por prevención primaria (58,5%) como secundaria (41,5%). Se utilizó un cuestionario sociodemográfico y clínico, así como el Listado de Síntomas Breves (LSB­50). Se realizaron análisis descriptivos univariados y bivariados, pruebas t de diferencias entre medias y pruebas z de diferencias entre proporciones. RESULTADOS: Respecto al ajuste psicológico, el 43,9% de los pacientes refirió tener alteraciones del sueño, independientemente del tipo de prevención. Un mayor porcentaje de pacientes de prevención primaria mostraron puntuaciones altas en escalas clínicas. El 29,4% de los pacientes de prevención secundaria mostró miedo a sufrir alguna descarga. El 25% de los pacientes cuyo motivo de implantación fue primario indicó un nivel moderado o intenso en cuanto al malestar subjetivo derivado de la enfermedad, comparado con el 14,7% de los pacientes de prevención secundaria (p=0,7). CONCLUSIONES: Los pacientes con DAI presentan síntomas clínicamente relevantes en Psicoreactividad, Obsesión-compulsión, Ansiedad, Somatización, Alteraciones del sueño y el Índice de riesgo psicopatológico. Independientemente del tipo de prevención ambos grupos muestran un ajuste psicológico similar. No se encuentran diferencias entre los grupos ni en el miedo a las descargas ni en el grado de malestar subjetivo.

Medium- and long-term outcome after a single second-generation cryoballoon ablation in patients with paroxysmal and persistent atrial fibrillation.

INTRODUCTION AND OBJECTIVES: To report medium- and long-term results following a single second-generation cryoballoon (CB2)-based ablation procedure in patients with paroxysmal (PAF) and persistent (PeAF) atrial fibrillation. METHODS: A retrospective study was performed of consecutive patients undergoing a first CB2-based ablation procedure in a tertiary center. Cryoenergy was applied for 3 min if a time to effect <60 s was documented or 4 min otherwise, with a bonus application in cases of late isolation or suboptimal temperature. Follow-up was obtained from the regional health electronic records system and by telephone or personal interviews. Recurrence was defined as any atrial arrhythmia >30 s beyond a three-month blanking period. The clinical impact of recurrences was classified using a severity score. RESULTS: A total of 172 patients (134 PAF and 38 PeAF) were included, of whom 25 (14.5%) had structural heart disease and 120 (69.7%) had a normal or mildly dilated left atrium. Acute success was achieved in 167 (97.1%). After a median follow-up of 27 (14-41) months, 100 patients (58.1%) remained free of atrial arrhythmias (64.2% for PAF and 36.8% for PeAF, p=0.006). Left atrial size (p=0.05) and clinical presentation as PeAF (p=0.006) were predictors of recurrence. Of patients with recurrences, 11.1% did not require further therapies and an additional 16.7% had good control with antiarrhythmic drugs. CONCLUSIONS: A single CB2 procedure resulted in 58.1% of patients remaining free of atrial arrhythmias at 27-month follow-up. Conservative management was useful in 27.8% of patients with recurrences.

Force Trends and Pulsatility for Catheter Contact Identification in Intracardiac Electrograms during Arrhythmia Ablation.

The intracardiac electrical activation maps are commonly used as a guide in the ablation of cardiac arrhythmias. The use of catheters with force sensors has been proposed in order to know if the electrode is in contact with the tissue during the registration of intracardiac electrograms (EGM). Although threshold criteria on force signals are often used to determine the catheter contact, this may be a limited criterion due to the complexity of the heart dynamics and cardiac vorticity. The present paper is devoted to determining the criteria and force signal profiles that guarantee the contact of the electrode with the tissue. In this study, we analyzed 1391 force signals and their associated EGM recorded during 2 and 8 s, respectively, in 17 patients (82 ± 60 points per patient). We aimed to establish a contact pattern by first visually examining and classifying the signals, according to their likely-contact joint profile and following the suggestions from experts in the doubtful cases. First, we used Principal Component Analysis to scrutinize the force signal dynamics by analyzing the main eigen-directions, first globally and then grouped according to the certainty of their tissue-catheter contact. Second, we used two different linear classifiers (Fisher discriminant and support vector machines) to identify the most relevant components of the previous signal models. We obtained three main types of eigenvectors, namely, pulsatile relevant, non-pulsatile relevant, and irrelevant components. The classifiers reached a moderate to sufficient discrimination capacity (areas under the curve between 0.84 and 0.95 depending on the contact certainty and on the classifier), which allowed us to analyze the relevant properties in the force signals. We conclude that the catheter-tissue contact profiles in force recordings are complex and do not depend only on the signal intensity being above a threshold at a single time instant, but also on time pulsatility and trends. These findings pave the way towards a subsystem which can be included in current intracardiac navigation systems assisted by force contact sensors, and it can provide the clinician with an estimate of the reliability on the tissue-catheter contact in the point-by-point EGM acquisition procedure.

Genetics of myocarditis in arrhythmogenic right ventricular dysplasia.

BACKGROUND: Myocarditis occasionally is related to arrhythmogenic right ventricular dysplasia (ARVD) and sometimes overlaps during the early stages, which may lead to misdiagnosis. Acute myocarditis may reflect an active phase of ARVD. OBJECTIVE: The purpose of this study was to evaluate the genetic basis of myocarditis in ARVD and to investigate the association with a poorer prognosis and a higher risk of ventricular arrhythmias. METHODS: Two groups were analyzed: group A, which consisted of 131 affected patients-84 with ARVD (62% male, age 45 years [range 33-55 years]) and 47 with left-sided forms (arrhythmogenic left ventricular dysplasia [ALVD]) (47% male, age 45 years [range 25-61 years]); and group B, which consisted of 64 nonaffected mutation-carrying relatives (36% male, age 42 years [range 22-56 years]; 23 from classic ARVD families and 41 from ALVD families). RESULTS: Seven patients (3.5%) presented with a clinical diagnosis of acute myocarditis over median follow-up of 34 months. Myocarditis was the first clinical presentation in 6 of 7 cases. In 2 patients, acute myocarditis preceded worsening of left ventricular systolic function. In 1 case, myocarditis was associated with an increased gadolinium pattern in cardiac magnetic resonance. Two patients presented with ECG changes weeks after myocarditis resolution. Myocarditis preceded the development of ventricular tachycardia in 2 other patients. Myocarditis clustered in families bearing DSP Q447* and LDB3 c.1051A>G. CONCLUSION: Acute myocarditis reflects an active phase of ARVD that leads to changes in phenotype and abrupt progression of the disease. An active phase should be suspected in a patient with myocarditis associated with a family history of ARVD. Certain mutations may increase the susceptibility to superimposed myocarditis in ARVD.

Desmoplakin truncations and arrhythmogenic left ventricular cardiomyopathy: characterizing a phenotype.

AIMS: Risk stratification for sudden death in arrhythmogenic right ventricular cardiomyopathy (ARVC) is challenging in clinical practice. We lack recommendations for the risk stratification of exclusive left-sided phenotypes. The aim of this study was to investigate genotype-phenotype correlations in patients carrying a novel DSP c.1339C>T, and to review the literature on the clinical expression and the outcomes in patients with DSP truncating mutations. METHODS AND RESULTS: Genetic screening of the DSP gene was performed in 47 consecutive patients with a phenotype of either an ARVC (n = 24) or an idiopathic dilated cardiomyopathy (DCM), who presented with ventricular arrhythmias or a family history of sudden death (n = 23) (aged 40 ± 19 years, 62% males). Three unrelated probands with DCM were found to be carriers of a novel mutation (c.1339C>T). Cascade family screening led to the identification of 15 relatives who are carriers. Penetrance in c.1339C>T carriers was 83%. Sustained ventricular tachycardia was the first clinical manifestation in six patients and nine patients were diagnosed with left ventricular impairment (two had overt severe disease and seven had a mild dysfunction). Cardiac magnetic resonance revealed left ventricular involvement in nine cases and biventricular disease in three patients. Extensive fibrotic patterns in six and non-compaction phenotype in five patients were the hallmark in imaging. CONCLUSION: DSP c.1339C>T is associated with an aggressive clinical phenotype of left-dominant arrhythmogenic cardiomyopathy and left ventricular non-compaction. Truncating mutations in desmoplakin are consistently associated with aggressive phenotypes and must be considered as a risk factor of sudden death. Since ventricular tachycardia occurs even in the absence of severe systolic dysfunction, an implantable cardioverter-defibrillator should be indicated promptly.

Multiple interatrial electrical connection after heart transplantation.

A 62-year-old woman who underwent heart transplantation 6 years later presented a regular atrial tachycardia. Electrophysiologic evaluation showed an atrial arrhythmia in the recipient atrium with 2:1 conduction to the donor atrium, with a confusing electroanatomical map. With the suspect of alternant conduction through two different breakthroughs, the map was split in two concordant maps, corresponding to two connections that were successfully ablated. Later on, a third connection was detected and therefore ablated.

Ablation of Premature Ventricular Complexes Triggering Ventricular Fibrillation in a Patient with Long QT Syndrome.

We describe the case of a patient with long QT syndrome and recurrent ventricular fibrillation, triggered by premature ventricular complexes (PVCs) with a left bundle branch block pattern and inferior axis of the QRS. Activation mapping demonstrated the origin of the PVCs to be in the right ventricular outflow tract. Ventricular fibrillation (VF) was successfully treated by catheter ablation of the triggering PVCs and there has been no recurrence of VF during a follow-up period of 14 months.

Premature ventricular complexes as a trigger for ventricular fibrillation.

INTRODUCTION AND OBJECTIVES: The mechanisms that trigger ventricular fibrillation (VF) are poorly understood. The aim of this study was to analyze the initiation of VF in electrograms stored in implantable cardioverter-defibrillators (ICDs). METHODS: We analyzed ICD electrograms from patients who had suffered at least one episode of VF. RESULTS: Of 250 patients with ICDs, 13 (10 male and 3 female, age 49+/-22 years) had at least one episode of VF. The diagnoses were Brugada syndrome (n=4), ischemic heart disease (n=3), dilated cardiomyopathy (n=2), hypertrophic cardiomyopathy (n=1), short-coupled variant of torsades de pointes (n=1), endocardial fibroelastosis (n=1) and idiopathic VF (n=1). In 7 patients, VF was the reason for ICD implantation. Overall, 31 episodes of VF were recorded, including three episodes of arrhythmic storm. In the 7 patients who had more than one episode of VF (within minutes or up to 3 years apart), all episodes started with premature ventricular complexes (PVCs) that had the same morphology and similar coupling intervals. A short-long-short cycle was observed in 2 patients. In 21 episodes, PVCs that did not trigger VF were observed during sinus rhythm. There was no significant difference between them and PVCs that did trigger VF in terms of morphology, coupling interval (409+/-121 ms vs. 411+/-123 ms) or the preceding sinus rhythm RR interval (801+/-233 ms vs. 793+/-230 ms). CONCLUSIONS: Spontaneous VF in the form of an arrhythmic storm or an isolated episode were triggered by PVCs. On occasions, PVCs preceded VF without triggering it.

Fundamental frequency and regularity of cardiac electrograms with Fourier organization analysis.

Dominant frequency analysis (DFA) and organization analysis (OA) of cardiac electrograms (EGMs) aims to establish clinical targets for cardiac arrhythmia ablation. However, these previous spectral descriptions of the EGM have often discarded relevant information in the spectrum, such as the harmonic structure or the spectral envelope. We propose a fully automated algorithm for estimating the spectral features in EGM recordings. This approach, called Fourier OA (FOA), accounts jointly for the organization and periodicity in the EGM, in terms of the fundamental frequency instead of dominant frequency. In order to compare the performance of FOA and DFA-OA approaches, we analyzed simulated EGM, obtained in a computer model, as well as two databases of implantable defibrillator-stored EGM. FOA parameters improved the organization measurements with respect to OA, and averaged cycle length and regularity indexes were more accurate when related to the fundamental (instead of dominant) frequency, as estimated by the algorithm (p < 0.05 comparing f(0) estimated by DFA and by FOA). FOA yields a more detailed and robust spectral description of EGM compared to DFA and OA parameters.

Same morphology of ventricular premature complexes triggering repeated ventricular fibrillation.

BACKGROUND: Episodes ventricular fibrillation (VF) initiated by ventricular premature complexes (VPCs) of a single morphology have been reported. However, the characteristics of the VPCs over long periods of time are unknown. OBJECTIVES: To compare the morphologies and coupling intervals of VPCs that initiate episodes of VF that occur at different time periods. METHODS: The database of the follow-up of the International Classification of Diseases (ICD) unit was reviewed and patients having at least two spontaneous VF episodes with available recorded EGMs in unipolar and bipolar configuration were included in the study. The coupling interval and morphology of the initiating beat were analyzed. RESULTS: Nine out of 300 patients with ICD had two or more spontaneous VF episodes. The time interval between episodes ranged from seconds (arrhythmic storm) to 3 years. The fibrillatory VPCs presented the same morphology in both recordings in all episodes of each patient. The coupling intervals of VPCs initiating VF were close for the episodes that occurred during a single arrhythmic storm and were more variable when the time intervals between episodes of VF were longer. CONCLUSION: VPCs triggering VF that occur at different times in the same patient have similar morphologies suggesting similar sites of origin for the initial VPC of VF in each patient.

ICD proarrhythmia as a consequence of an interaction with an algorithm to prevent atrial arrhythmias.

An episode of device-related proarrhythmia is reported. Ventricular tachycardia was induced by ventricular pacing in a dual-chamber implantable cardioverter-defibrillator due to an inappropriate interaction of programmed device settings with the atrial preference pacing, an automatic algorithm designed to prevent atrial tachyarrhythmias.

Spectral analysis of sustained and non-sustained ventricular fibrillation in patients with an implantable cardioverter-defibrillator.

The mechanisms responsible for the maintenance and termination of ventricular fibrillation (VF) are poorly understood. The aim of this study was to compare the spectral characteristics of the electrical signal during sustained and non-sustained VF in patients with an implantable cardioverter-defibrillator. The study included 51 patients who had had at least one episode of sustained VF (i.e., duration >5 s and requiring shock administration) and non-sustained VF (i.e., duration >3 s and spontaneously terminated) that were recorded by the device set in a unipolar configuration. Spectral analysis of the first 3 s of each episode was performed. The dominant frequency was higher in sustained VF (4.6+/-0.7 Hz) than in non-sustained VF (4.3+/-0.6 Hz; P=.01), while the other parameters were similar. Although the spectral characteristics of sustained and non-sustained VF were similar, differences were observed during the first 3 s that could be used in algorithms for the early detection of non-sustained VF.

Spectral analysis of intracardiac electrograms during induced and spontaneous ventricular fibrillation in humans.

AIMS: Very limited data are available on the differences between spontaneous and induced episodes of ventricular fibrillation (VF) in humans. The aim of the study was to compare the spectral characteristics of the electrical signal recorded by an implantable cardioverter defibrillator (ICD) during both types of episodes. METHODS AND RESULTS: Thirteen ICD patients with at least one spontaneous and one induced VF recorded by the device were included in the study. A spectral representation was obtained for the first 3 s of the intracardiac unipolar electrogram during VF. The dominant frequency (f(d)), the peak power at f(d), an organization index (OI), a bandwidth measurement, and an estimate of the correlation with a sinusoidal wave (leakage) were estimated for each episode. The f(d) was higher in induced episodes (4.75 +/- 0.57 vs. 3.95 +/- 0.59 Hz for the spontaneous episodes, P = 0.002), as well as the degree of organization assessed by the OI, bandwidth, and leakage parameters. CONCLUSION: Clinical and induced VF episodes in humans have different spectral characteristics. Changes in the electrophysiological substrate or in the location of the arrhythmia wavefront at onset could play a role to explain the observed differences.