Mecanismos electrofisiológicos y diagnóstico de la fibrilación auricular / Electrophysiological mechanisms and diagnosis of atrial fibrillation

Pese a ser la arritmia cardiaca sostenida más frecuente y que se describió hace más de 100 años, la fibrilación auricular es, junto con la fibrilación ventricular, prácticamente la única cuyo mecanismo aún se desconoce. Este desconocimiento tiene profundas implicaciones clínicas más allá de un mero interés académico. Así, el desconocimiento sobre el mecanismo hace que el diagnóstico de esta arritmia siga siendo básicamente electrocardiográfico. Esto origina que se planteen dudas diagnósticas con cierta frecuencia, tanto en el ECG de superficie como en registros electrofisiológicos intracavitarios. Además, el desconocimiento de su mecanismo limita el desarrollo de terapias farmacológicas e invasivas más dirigidas y medidas preventivas que la eviten o al menos la retrasen. En este artículo se revisan las teorías más aceptadas sobre el mecanismo de esta arritmia, como la de las múltiples reentradas funcionales coexistentes o la de los rotores madre, así como la de los factores que pueden influir en él, como el remodelado auricular, la presencia de fibrosis y cicatrices auriculares, la masa auricular, el papel de las venas pulmonares y los hechos que respaldan una relación con la reentrada. Asimismo, se revisan los criterios diagnósticos de esta arritmia, sus tipos y las exploraciones diagnósticas que se debe realizar a estos pacientes (AU)

Despite being the most common sustained cardiac arrhythmia and despite having been first described over 100 years ago, atrial fibrillation is, like ventricular fibrillation, virtually the only arrhythmia whose mechanism is still unknown. This lack of knowledge has profound clinical implications and is not just of academic interest. Firstly, lack of knowledge means that the diagnosis of atrial fibrillation is still based on ECG findings, which can often give rise to doubts about the diagnosis, with both surface ECGs and intracardiac electrophysiological studies. Moreover, lack of knowledge about the underlying mechanism also hampers the development of both better-targeted pharmacological and invasive therapies and preventive measures that can avert, or at least delay, the onset of atrial fibrillation. This article provides a review of the most widely accepted theories about the mechanism underlying this arrhythmia, such as the multiple coexisting functional re-entry circuits theory and the mother rotor theory. In addition, the article examines factors that could influence the condition, such as atrial remodeling, atrial fibrosis and scarring, and the critical atrial mass, and considers the role of the pulmonary veins and the evidence supporting a link with re-entry. Diagnostic criteria for this arrhythmia, its classification and recommended diagnostic investigations are also discussed (AU)

Current trends in the use of cardiac implantable electronic devices and interventional electrophysiological procedures in the European Society of Cardiology member countries: 2015 report from the European Heart Rhythm Association.

AIMS: The aim was to provide comprehensive information on the use of cardiac implantable electronic device (CIED) and catheter ablation therapy in the European Society of Cardiology (ESC) area. METHODS AND RESULTS: The European Heart Rhythm Association (EHRA) has collected data on use of invasive arrhythmia managements since 2008. Fifty-one of the 56 ESC member countries provided data for the EHRA White Book 2015. This analysis is based on the current and previous editions of the EHRA White Book. Up-to-date information on procedure rates for the last 5 years together with information on economic resources, reimbursement systems, and training requirements are presented for each country and the five geographical ESC regions. In 2014, the CIED implantation rates per million population were highest in the Western followed by the Southern and Northern European countries. The catheter ablation activity was largest in the Western followed by the Northern and Southern areas. Altogether the procedure rates were lowest in the Eastern European and in the non-European ESC countries. In the European ESC countries, the procedure rates were 3-10 times higher than in the non-European ESC countries. However, in some countries with a relatively low gross domestic product the procedure rates exceeded the average values indicating that utilization of arrhythmia therapies was not driven merely by the economic factors. CONCLUSION: This analysis indicates that considerable heterogeneity in the availability and utilization of arrhythmia therapies still exist across the ESC area. The data will hopefully aid in directing future activities and promote harmonization of cardiac arrhythmia care in the ESC countries.

Statistics on the use of cardiac electronic devices and electrophysiological procedures in the European Society of Cardiology countries: 2014 report from the European Heart Rhythm Association.

AIMS: There has been large variations in the use of invasive electrophysiological therapies in the member countries of the European Society of Cardiology (ESC). The aim of this analysis was to provide comprehensive information on cardiac implantable electronic device (CIED) and catheter ablation therapy trends in the ESC countries over the last five years. METHODS: The European Heart Rhythm Association (EHRA) has collected data on CIED and catheter ablation therapy since 2008. Last year 49 of the 56 ESC member countries provided data for the EHRA White Book. This analysis is based on the current and previous editions of the EHRA White Book. Data on procedure rates together with information on economic aspects, local reimbursement systems and training activities are presented for each ESC country and the five geographical ESC regions. RESULTS: In 2013, the electrophysiological procedure rates per million population were highest in Western Europe followed by the Southern and Northern European countries. The CIED implantation and catheter ablation rate was lowest in the Eastern European and in the non-European ESC countries, respectively. However, in some Eastern European countries with relative low gross domestic product procedure rates exceeded those of some wealthier Western countries, suggesting that economic resources are not the only driver for utilization of arrhythmia therapies. CONCLUSION: These statistics indicate that despite significant improvements, there still is considerable heterogeneity in the availability of arrhythmia therapies across the ESC area. Hopefully, these data will help identify areas for improvement and guide future activities in cardiac arrhythmia management.

Implantation of cardioverter defibrillators with minimal fluoroscopy using a three-dimensional navigation system: a feasibility study.

AIMS: Fluoroscopy is necessary to implant cardioverter defibrillators using the conventional approach. Modern electroanatomic navigation systems allow the visualization of multiple catheters and, as they are capable of rendering precise geometrical reconstructions of cardiac chambers, have been used for fluoroscopy-free electrophysiological procedures. The aim of our study was to assess the feasibility of non-fluoroscopic implants using a three-dimensional navigation system. METHODS AND RESULTS: The NavX system was used to create the virtual anatomies of heart chambers and thoracic veins. Defibrillator leads were placed at stable positions using exclusively the electrical and anatomical information provided by the navigator. A single fluoroscopy shot confirmed final lead positions. Thirty-five consecutive patients had 30 single-chamber and 5 dual-chamber defibrillators implanted. Cardiac chambers geometries were developed in 10 ± 4.3 min. Ventricular and atrial leads were implanted, with suitable positions and electrical parameters being achieved, in 18 ± 22 and 16 ± 9 min, respectively. The final confirmatory shot was the only fluoroscopy needed in 31 (89%) cases. Two patients needed fluoroscopy-guided relocation of the ventricular lead due to high defibrillation threshold and a breakdown of the active-fixation mechanism, respectively. In one patient the ventricular lead was totally extracted and reimplanted because a loop has formed in the vena cava, and one patient required fluoroscopy-guided subclavian puncture. In five cases (16%), the position of the proximal defibrillation coil was minimally modified with fluoroscopy due to incomplete geometric reconstruction of the superior vena cava. CONCLUSION: Fluoroscopy-free defibrillators implantation is feasible using a navigation system. Suitable placement of the proximal coil is a critical stage and requires a reliable and complete reconstruction of the superior vena cava.

Innovations in heart rhythm disturbances: cardiac electrophysiology, arrhythmias, and cardiac pacing.

This article reviews the most relevant articles published in 2012 in the field of arrhythmias, on subjects that include clinical arrhythmology, ablation, cardiac pacing, and the genetics of sudden cardiac death.

Resultados e implicaciones del estudio ROCKET / Findings and implications of the ROCKET Study

La embolia sistémica y el accidente cerebrovascular están entre las complicaciones más importantes de la fibrilación auricular. La estrategia principal para prevenirlos es la anticoagulación a largo plazo, y durante los últimos 50 años los únicos anticoagulantes orales disponibles han sido los derivados de la warfarina. En el estudio ROCKET, la anticoagulación con el antagonista del factor Xa rivaroxabán demostró claras ventajas clínicas en la prevención de la embolia sistémica y las hemorragias intracraneales en comparación con la anticoagulación con warfarina, sin necesidad de realizar controles periódicos de anticoagulación. Los resultados de este estudio, junto con los de los estudios con apixabán y dabigatrán, tendrán en el futuro un impacto terapéutico y desplazarán a los dicumarínicos en la prevención de embolias en pacientes con fibrilación auricular (AU)

Systemic embolism and stroke are two of the most important complications of atrial fibrillation. The main strategy used for their prevention is long-term oral anticoagulation therapy and, during the last 50 years, the only oral anticoagulants available were derivatives of warfarin. In the ROCKET study, anticoagulation therapy with the factor-Xa antagonist rivaroxaban demonstrated clear clinical advantages over warfarin in the prevention of systemic embolism and intracranial hemorrhage. Moreover, there was no need for regular anticoagulation monitoring. The results of that study, combined with those of studies on apixaban and dabigatran, will lead to a change in treatment in the future, and these new compounds will displace coumarins in the prevention of embolism in patients with atrial fibrillation (AU)

Nuevos tratamientos anticoagulantes para la prevención del ictus y la embolia sistémica en la fibrilación auricular no valvular / New anticoagulants for the prevention of stroke and systemic embolism in nonvalvular atrial fibrillation

Durante 50 años, los inhibidores de la vitamina K han sido los únicos anticoagulantes orales disponibles para el tratamiento crónico en la prevención de embolias en pacientes con fibrilación auricular. Recientemente, se han completado y publicado tres estudios con fármacos antitrombóticos con un mecanismo de acción diferente: el dabigatrán (un inhibidor de la trombina), el rivaroxabán y el apixabán (inhibidores del factor Xa). En esta revisión se analizan las características y los resultados de los tres estudios. En todos se ha demostrado algún beneficio clínico sobre la warfarina y en su conjunto ofrecen una alternativa superior a los antagonistas de la vitamina K en la prevención de ictus y embolias sistémicas en una gran proporción de pacientes con fibrilación auricular no valvular. La utilización de estos nuevos fármacos anticoagulantes debería iniciarse ya, sin olvidar que, al ser fármacos anticoagulantes, siempre existe el riesgo de hemorragia, por lo que la selección y la educación de los enfermos son obligatorias (AU)

For 50 years, vitamin K inhibitors have been the only oral anticoagulants available for long-term use in the prevention of embolism in patients with atrial fibrillation. Recently, three studies of antithrombotic drugs with different mechanisms of action have been completed and reported: one involved the thrombin inhibitor dabigatran and two involved the factor-Xa inhibitors rivaroxaban and apixaban. This review describes the designs and results of the three studies. All demonstrated that the new drugs had some clinical advantage over warfarin and, taken together, they offer a better alternative to the use of vitamin K antagonists for preventing stroke and systematic embolism in a large proportion of patients with nonvalvular atrial fibrillation. These new anticoagulant drugs should already be in clinical use. However, it should be remembered that, as with all anticoagulants, there is always a risk of bleeding. Accordingly, it is essential that patients are carefully selected and provided with adequate information (AU)

Comparative effects of dietary supplementation with red grape juice and vitamin E on production of superoxide by circulating neutrophil NADPH oxidase in hemodialysis patients.

BACKGROUND: Atherosclerotic cardiovascular disease is the most common cause of death among hemodialysis patients; it has been attributed to increased oxidative stress, dyslipidemia, malnutrition, and chronic inflammation. Activation of neutrophils is a well-recognized feature in dialysis patients, and superoxide-anion production by neutrophil NADPH oxidase may contribute significantly to oxidative stress. OBJECTIVE: The aim of the study was to compare the effects of dietary supplementation with concentrated red grape juice (RGJ), a source of polyphenols, and vitamin E on neutrophil NADPH oxidase activity and other cardiovascular risk factors in hemodialysis patients. DESIGN: Thirty-two patients undergoing hemodialysis were recruited and randomly assigned to groups to receive dietary supplementation with RGJ, vitamin E, or both or a control condition without supplementation or placebo. Blood was obtained at baseline and on days 7 and 14 of treatment. RESULTS: RGJ consumption but not vitamin E consumption reduced plasma concentrations of total cholesterol and apolipoprotein B and increased those of HDL cholesterol. Both RGJ and vitamin E reduced plasma concentrations of oxidized LDL and ex vivo neutrophil NADPH oxidase activity. These effects were intensified when the supplements were used in combination; in that case, reductions in the inflammatory biomarkers intercellular adhesion molecule 1 and monocyte chemoattractant protein 1 also were observed. CONCLUSIONS: Regular ingestion of concentrated RGJ by hemodialysis patients reduces neutrophil NADPH-oxidase activity and plasma concentrations of oxidized LDL and inflammatory biomarkers to a greater extent than does that of vitamin E. This effect of RGJ consumption may favor a reduction in cardiovascular risk.

Atrial fibrillation triggered by postinfarction ventricular premature beats in a patient with Wolff-Parkinson-White syndrome.

The mechanism by which atrial fibrillation is initiated in patients with accessory pathways is not fully understood. Retrograde conduction of ventricular premature beats to the atrium, causing the arrhythmia, is a very rare cause. We report a patient with Wolff-Parkinson-White syndrome (WPW), without previous tachycardias, who presented multiple episodes of paroxysmal atrial fibrillation after having a myocardial infarction. During the electrophysiological (EP) study the patient presented two spontaneous episodes of atrial fibrillation initiated by ventricular premature beats conducted to the atria through the accessory pathway. After successful catheter ablation of the accessory pathway the patient did not present arrhythmia recurrences.