Ventricular preexcitation in children and young adults: atrial myocarditis as a possible trigger of sudden death

Impact of high-resolution 3D-mapping with micro-electrodes on catheter ablation of Wolff-Parkinson-White syndrome

Background

It is currently unknown whether high-resolution 3D-mapping and micro-electrodes add meaningful benefits in catheter ablation of Wolff-Parkinson-White (WPW) syndrome and challenging, e.g. para-Hisian accessory pathways (APs).

Objectives

To compare the mapping resolution, acute success and complication rates in patients with WPW syndrome undergoing a first-time catheter ablation using only a contact force-sensing ablation catheter for mapping or a multi-electrode high-resolution mapping catheter.

Methods

Fifty consecutive 3D-mapping procedures for WPW syndrome using a 3.5-mm ablation catheter (n = 27) or a multi-electrode high-resolution catheter (n = 23) were retrospectively analyzed regarding mapping resolution defined as first 5/10 msec isochronal activation area, number of RF applications to achieve AP block, occurence of AP automaticity during RF delivery, and acute success and complication rates.

Results

Catheter ablation was successful in 48/50 patients with a median of 1 (IQR 1-2) RF applications. Compared to ablation catheter mapping, high-resolution mapping showed a significantly smaller isochronal activation area in the first 5/10 msec (1.25 ± 0.29 vs 0.15 ± 0.03 cm2; P < 0.001 and 3.41 ± 0.58 vs 0.55 ± 0.12 cm2; P < 0.0001) and significantly higher incidence of AP automaticity during RF delivery (0 vs 22 %; P < 0.05). In para-Hisian APs, micro-electrodes recorded distinct His electrograms and AP potentials without fusion and without AP bumping permitting safe and effective para-Hisian AP ablation.

Conclusions

High-resolution mapping increases the mapping accuracy of the AP and its insertion site leading to a significantly higher incidence of AP automaticity during RF delivery. Micro-electrodes provide clinically relevant advantages in para-hisian AP mapping improving efficacy and safety of para-Hisian AP ablation.

Autopsy and sudden death

Our story dates back in the late 70s, when a series of juvenile sudden death (SD) occurred in the Veneto region, north east of Italy. A successful application for a prospective study on young people dying suddenly (<35-year-old, sudden infant death syndrome excluded) was submitted to the regional health authorities, thus implementing a network of collaboration with local anatomic and forensic pathologists, to collect all such events and to gather demographic data. The project is still in progress, and since then, we studied hundreds of consecutive juvenile SD cases, allowing to identify the culprit diseases in the various organs and cardiac structures (aorta, coronary arteries, myocardium, valves, and conduction system). The long-standing Veneto region experience clearly shows that autopsy still plays a pivotal role in the study and prevention of SD and should be carried out regularly. With time, the investigation of SD moved from the classic post-mortem study to molecular autopsy, especially in cases of SD with structurally normal heart. Sudden death prevention in the young has to be faced by an interdisciplinary team, including pathologists, cardiologists, sport physicians, and geneticists, the clinicopathologic correlation method still being the polar star. The game in the fight against SD is still played in the anatomical theatre, the place where 'death enjoys to save lives'.

Broad Electrocardiogram Syndromes Spectrum: From Common Emergencies to Particular Electrical Heart Disorders

Electrocardiogram (ECG) still remains a very useful diagnostic method in modern cardiology. Its broad availability, noninvasiveness and good sensitivity explain why it plays a capital role in the very beginning of the process of diagnosis for every patient, with or without cardiac-related complaints. For the practitioner, good training in ECG interpretation is mandatory. Sometimes, the ECG trace reveals particular aspects that may cause confusion and complicate decision-making. In this article, we present several less common situations underlying the general context and ECG features. The syndromes studied have a high pathological significance and may range from acute emergencies that call for a rapid therapeutical response to chronic syndromes that require prolonged observation, monitoring and risk stratification.

Recommendations for participation in leisure-time physical activity and competitive sports in patients with arrhythmias and potentially arrhythmogenic conditions: Part 1: Supraventricular arrhythmias. A position statement of the Section of Sports Cardiology and Exercise from the European Association of Preventive Cardiology (EAPC) and the European Heart Rhythm Association (EHRA), both associations of the European Society of Cardiology

Symptoms attributable to arrhythmias are frequently encountered in clinical practice. Cardiologists and sport physicians are required to identify high-risk individuals harbouring such conditions and provide appropriate advice regarding participation in regular exercise programmes and competitive sport. The three aspects that need to be considered are: (a) the risk of life-threatening arrhythmias by participating in sports; (b) control of symptoms due to arrhythmias that are not life-threatening but may hamper performance and/or reduce the quality of life; and (c) the impact of sports on the natural progression of the underlying arrhythmogenic condition. In many cases, there is no unequivocal answer to each aspect and therefore an open discussion with the athlete is necessary, in order to reach a balanced decision. In 2006 the Sports Cardiology and Exercise Section of the European Association of Preventive Cardiology published recommendations for participation in leisure-time physical activity and competitive sport in individuals with arrhythmias and potentially arrhythmogenic conditions. More than a decade on, these recommendations are partly obsolete given the evolving knowledge of the diagnosis, management and treatment of these conditions. The present document presents a combined effort by the Sports Cardiology and Exercise Section of the European Association of Preventive Cardiology and the European Heart Rhythm Association to offer a comprehensive overview of the most updated recommendations for practising cardiologists and sport physicians managing athletes with supraventricular arrhythmias, and provides pragmatic advice for safe participation in recreational physical activities, as well as competitive sport at amateur and professional level. A companion text on recommendations in athletes with ventricular arrhythmias, inherited arrhythmogenic conditions, pacemakers and implantable defibrillators is published as Part 2 in Europace.

Atrial fibrillation after orthotopic heart transplantatation: Pathophysiology and clinical impact

BACKGROUND

Atrial fibrillation (AF) is a well-established post-cardiac surgery complication. Orthotopic heart transplantation (OHT) represents a peculiar condition where surgical thoracic veins isolation and autonomic denervation occur. This study aims at investigating AF incidence in OHT in order to define its risk factors and to evaluate its prognostic impact.

METHODS

278 patients affected by OHT were recruited in our Cardiac Surgery Unit and retrospectively analyzed, using clinical, surgical and instrumental data.

RESULTS

The patients cohort showed 45 post-operative (16.5%) and 20 late AF cases (7.2%). Only paroxysmal AF episodes were observed. Elderly donors and acute rejection resulted as risk factors in patients with post-operative AF episodes, who presented higher all-cause mortality at 11 years post-OHT (p < 0.001, Kaplan Meier analysis). The majority of late AF episodes occurred during hospitalization, due to renal failure or infections and more frequently in male patients; no significant correlation was observed with acute or chronic rejection or other characteristics.

CONCLUSION

Pulmonary vein isolation and vagal denervation lead to low AF incidence in OHT recipients. Acute rejection and graft status are the main risk factors for post-operative AF episodes, while other systemic conditions act as late AF triggers. The occurrence of AF episodes is associated with poor outcome and AF should be considered as a marker of clinical frailty.

Anatomy of the Atrioventricular Junction, Atrioventricular Grooves, and Accessory Pathways

Accessory pathways that bypass all or part of the normal atrioventricular conduction system traverse the atrioventricular junction. The atrioventricular junction comprises of a limited septal component and much more extensive right and left parietal components. Its composition forms a plane of insulation between atrial and ventricular myocardium, preventing direct continuity between them. Typical accessory atrioventricular pathways located anywhere along the atrioventricular junction are muscle bundles or may involve muscle around the walls of coronary sinus aneurysms or coronary veins. Increasingly, variants or unusual accessory pathways, some involving an accessory node, are reported in clinical studies.

Sudden Cardiac Death in Patients with Ventricular Preexcitation

Patients with the Wolff-Parkinson-White syndrome may experience benign and malignant arrhythmias, the most common being atrioventricular reentrant tachycardias. This arrhythmia may degenerate into atrial fibrillation, which can be conducted over an accessory pathway capable of exceptionally fast conduction to the ventricles and degenerate into ventricular fibrillation, leading to sudden cardiac death. These life-threatening events generally affect symptomatic patients in their third or fourth decade. Although rare, ventricular fibrillation may be the first clinical manifestation in subjects who are asymptomatic or unaware of their conditions. Electrophysiologic study may be useful to identify subjects at high risk of sudden cardiac death.

Syncope and Palpitations: A Review

Syncope and palpitations are common complaints for patients presenting to their primary care provider. They represent symptoms that most often have a benign etiology but rarely can be the first warning sign of a serious condition, such as arrhythmias, structural heart disease, or noncardiac disease. The history, physical examination, and noninvasive testing can, in most cases, distinguish benign from pathologic causes. This article introduces syncope and palpitations, with emphasis on the differential diagnoses, initial presentation, diagnostic strategy, and various management strategies.

Autopsy in adults with congenital heart disease (ACHD)

The adult congenital heart diseases (ACHD) population is exceeding the pediatric congenital heart diseases (CHD) population and is progressively expanding each year, representing more than 90% of patients with CHD. Of these, about 75% have undergone surgical and/or percutaneous intervention for palliation or correction. Autopsy can be a very challenging procedure in ACHD patients. The approach and protocol to be used may vary depending on whether the pathologists are facing native disease without surgical or percutaneous interventions, but with various degrees of cardiac remodeling, or previously palliated or corrected CHD. Moreover, interventions for the same condition have evolved over the last decades, as has perioperative myocardial preservations and postoperative care, with different long-term sequelae depending on the era in which patients were operated on. Careful clinicopathological correlation is, thus, required to assist the pathologist in performing the autopsy and reaching a diagnosis regarding the cause of death. Due to the heterogeneity of the structural abnormalities, and the wide variety of surgical and interventional procedures, there are no standard methods for dissecting the heart at autopsy. In this paper, we describe the most common types of CHDs that a pathologist could encounter at autopsy, including the various types of surgical and percutaneous procedures and major pathological manifestations. We also propose a practical systematic approach to the autopsy of ACHD patients.

Myocarditis in the Athlete: Arrhythmogenic Substrates, Clinical Manifestations, Management, and Eligibility Decisions

Myocarditis is as an important cause of sudden cardiac death (SCD) among athletes. The incidence of SCD ascribed to myocarditis did not change after the introduction of pre-participation screening in Italy, due to the transient nature of the disease and problems in the differential diagnosis with the athlete's heart. The arrhythmic burden and the underlying mechanisms differ between the acute and chronic setting, depending on the relative impact of acute inflammation versus post-inflammatory myocardial fibrosis. In the acute phase, ventricular arrhythmias vary from isolated ventricular ectopic beats to complex tachycardias that can lead to SCD. Atrioventricular blocks are typical of specific forms of myocarditis, and supraventricular arrhythmias may be observed in case of atrial inflammation. Athletes with acute myocarditis should be temporarily restricted from physical exercise, until complete recovery. However, ventricular tachycardia may also occur in the chronic phase in the context of post-inflammatory myocardial scar.

Cardiac arrest at rest and during sport activity: causes and prevention

In the Western Countries, cardiovascular diseases are still the most frequent cause of death, which is often sudden. Sudden death (SD) in the young population occurs at a rate of 1/100 000/year and carries a profound social impact both for the young age of the victims and the unanticipated occurrence. Physical effort is a triggering risk factor, in fact SD occurs three times more frequently in athletes than in non-athletes. The screening for sport activity fitness can identify apparently healthy subjects carrying a silent abnormality able to trigger sudden cardiac death during sport activity, thus the fitness screening could be lifesaving. The spectrum of cardiovascular conditions identified at post-mortem examination is quite extensive, and include: coronary, myocardial, valvular diseases, as well as conduction system abnormalities. In 20% of the cases, the heart is normal, and sudden cardiac death is ascribed to ionic channel disease. The diagnosis of cardiomyopathy is possible with the integration of electrocardiogram and echography, thus decreasing significantly the occurrence of SD of athletes in Italy, but early diagnosis of coronary artery disease still remains challenging. The best strategy to further decrease sudden cardiac death during sport activities consists in combining early diagnosis with widespread availability of defibrillators on site.

Transcriptional regulation of the cardiac conduction system

The rate and rhythm of heart muscle contractions are coordinated by the cardiac conduction system (CCS), a generic term for a collection of different specialized muscular tissues within the heart. The CCS components initiate the electrical impulse at the sinoatrial node, propagate it from atria to ventricles via the atrioventricular node and bundle branches, and distribute it to the ventricular muscle mass via the Purkinje fibre network. The CCS thereby controls the rate and rhythm of alternating contractions of the atria and ventricles. CCS function is well conserved across vertebrates from fish to mammals, although particular specialized aspects of CCS function are found only in endotherms (mammals and birds). The development and homeostasis of the CCS involves transcriptional and regulatory networks that act in an embryonic-stage-dependent, tissue-dependent, and dose-dependent manner. This Review describes emerging data from animal studies, stem cell models, and genome-wide association studies that have provided novel insights into the transcriptional networks underlying CCS formation and function. How these insights can be applied to develop disease models and therapies is also discussed.

The Value of Baseline and Arrhythmic ECG in the Interpretation of Arrhythmic Mechanisms

Owing to the rapid development of new electrophysiologic techniques, our understanding of arrhythmias and their underlying mechanisms has reached unprecedented levels. In some cases, baseline ECG alterations can be identified before arrhythmia development; early recognition of these alterations is of utmost importance to start appropriate preventive therapies and stratify the risk according to patients' outcomes. Hereby, we report a systematic revision of main baseline ECG abnormalities and their implications on clinical outcomes.

A Case of Lown-Ganong-Levine Syndrome: Due to an Accessory Pathway of James Fibers or Enhanced Atrioventricular Nodal Conduction (EAVNC)?

Patient: Male, 17

Final Diagnosis: Lown-Ganong-Levine syndrome

Symptoms: Tachycardia

Medication: —

Clinical Procedure: Catheter ablation

Specialty: Cardiology

Supraventricular tachycardia during the first year of life: is subclinical inflammation the trigger?

BACKGROUND

Neutrophil/lymphocyte ratio (NLR) and red cell distribution width (RDW) may be associated with the onset of arrhythmias in adults, thus underlining a possible inflammatory etiology. Paroxysmal supraventricular tachycardia (SVT) is the most frequent pathological tachycardia in childhood.

AIM

To verify NLR and RDW levels in a group of children (<1 year) affected by SVT with a structurally normal heart and without fever or inflammatory diseases; to compare NLR and RDW before and after SVT resolution, to verify whether the latter was related with the reduction in inflammatory state; to identify - in SVT subtypes caused by a reentry mechanism - an NLR and RDW cutoff point beyond which adenosine was ineffective in preventing SVT recurrence.

METHODS

Eighteen SVT patients were recruited (mean age 18.9 ± 3.2 days; 50% males) and compared with 18 healthy peers.

RESULTS

NLR was higher in SVT group than in controls (p < 0.03). A significant difference was revealed between NLR values obtained on admission and at discharge (p < 0.05). On the contrary, no significant differences were found for RDW. It was not possible to identify NLR or RDW cutoffs capable of predicting SVT recurrence. However, all patients featuring SVT recurrence following adenosine injection presented with a lymphocyte count >6000/mm³.

CONCLUSIONS

Elevated NLR is associated with an increased risk of SVT during the first year of life, while its decline looks like to lead the SVT resolution. A subclinical inflammatory status, as assessed by lymphocytes count, influences SVT recurrence. These results provide further support for an inflammatory etiology of SVT in babies.

Genome editing with CRISPR/Cas9 in postnatal mice corrects PRKAG2 cardiac syndrome

PRKAG2 cardiac syndrome is an autosomal dominant inherited disease resulted from mutations in the PRKAG2 gene that encodes γ2 regulatory subunit of AMP-activated protein kinase. Affected patients usually develop ventricular tachyarrhythmia and experience progressive heart failure that is refractory to medical treatment and requires cardiac transplantation. In this study, we identify a H530R mutation in PRKAG2 from patients with familial Wolff-Parkinson-White syndrome. By generating H530R PRKAG2 transgenic and knock-in mice, we show that both models recapitulate human symptoms including cardiac hypertrophy and glycogen storage, confirming that the H530R mutation is causally related to PRKAG2 cardiac syndrome. We further combine adeno-associated virus-9 (AAV9) and the CRISPR/Cas9 gene-editing system to disrupt the mutant PRKAG2 allele encoding H530R while leaving the wild-type allele intact. A single systemic injection of AAV9-Cas9/sgRNA at postnatal day 4 or day 42 substantially restores the morphology and function of the heart in H530R PRKAG2 transgenic and knock-in mice. Together, our work suggests that in vivo CRISPR/Cas9 genome editing is an effective tool in the treatment of PRKAG2 cardiac syndrome and other dominant inherited cardiac diseases by selectively disrupting disease-causing mutations.

Supernormal Conduction in the Anomalous Bundles of the Wolff-Parkinson-White Syndrome: An Overlooked Electrophysiologic Property With Potential Clinical Implications

The anterograde refractory period (RP) of the accessory pathway (AP) is the main determinant factor of ventricular rate during atrial fibrillation in the Wolff-Parkinson-White (WPW) syndrome. We describe 3 examples of anterograde supernormal conduction (SNC) and 1 of retrograde SNC in APs. The paradoxical early recovery of propagation due to SNC, well inside a prolonged anterograde RP in the AP, may play a relevant role to determine the rate of ventricular response during atrial fibrillation, eventually leading to extremely fast ventricular rates, syncope, and even ventricular fibrillation in patients with WPW syndrome supposed a priori to be exposed to a low risk of sudden cardiac death. This may require very precise conditions, including an enhanced adrenergic influence on the heart. Retrograde SNC in APs may also participate in the mechanism of paroxysmal supraventricular tachycardias that are not easily induced by programmed cardiac stimulation.

Ventricular myocarditis coincides with atrial myocarditis in patients

INTRODUCTION

Atrial fibrillation (AF) is a common complication in myocarditis. Atrial inflammation has been suggested to play an important role in the pathophysiology of AF. However, little is known about the occurrence of atrial inflammation in myocarditis patients. Here, we analyzed inflammatory cell numbers in the atria of myocarditis patients without symptomatic AF.

METHODS

Cardiac tissue was obtained postmortem from lymphocytic myocarditis patients (n=6), catecholamine-induced myocarditis patients (n=5), and control patients without pathological evidence of heart disease (n=5). Tissue sections of left and right ventricle and left and right atrium were stained for myeloperoxidase (neutrophilic granulocytes), CD45 (lymphocytes), and CD68 (macrophages). These cells were subsequently quantified in atrial and ventricular myocardium and atrial adipose tissue.

RESULTS

In lymphocytic myocarditis patients, a significant increase was observed for lymphocytes in the left atrial adipose tissue. In catecholamine-induced myocarditis patients, significant increases were found in the atria for all three inflammatory cell types. Infiltrating inflammatory cell numbers in the atrial myocardium correlated positively with those in the ventricles, especially in catecholamine-induced myocarditis patients.

CONCLUSIONS

To a varying extent, atrial myocarditis occurs concurrently with ventricular myocarditis in patients diagnosed with myocarditis of different etiology. This provides a substrate that potentially predisposes myocarditis patients to the development of AF and subsequent complications such as sudden cardiac death and heart failure.

Optimizing outcomes of catheter ablation in infants and toddlers

Since the introduction of transcatheter ablation in the late 1980s, there has been significant technical development. With a very high success rate and low complication rate, ablation has now become the standard of care in children and adults. However, long-term data remain insufficient and the application of ablation therapy in small children is debatable. In this review, current treatment strategies and results in toddlers and infants will be discussed. There has been improvement in success rate and complication rate for ablation in small children. Technological advancements in non-fluoroscopic electroanatomical mapping systems (3D systems) have led to the reduction of radiation and have facilitated ablations in complex cases. However, long-term effects of ablation lesions in small children remain a potential concern.

Sudden cardiac death and cardiovascular pathology: from anatomic theater to double helix

The experience as a cardiovascular pathologist on sudden cardiac death (SCD) in the young and the impact that the findings had on in vivo diagnosis, treatment, and prevention are herein reported. The story dates back in the late 70s, when a series of juvenile sudden deaths occurred in the Veneto Region, North East of Italy. A successful application for a prospective study on young people dying suddenly (<35 years old, sudden infant death syndrome excluded) was submitted to the regional health authorities, thus implementing a network of collaboration with anatomic and forensic pathologists, to collect all such events and to gather epidemiological data. The project is still in progress, and since then we studied >650 hundreds consecutive juvenile SCD cases, allowing to identify the culprit diseases with abnormalities in the various cardiac structures (aorta, coronary arteries, myocardium, valves, and conduction system). The long standing Veneto Region experience clearly shows that autopsy still plays a pivotal role in the study and prevention of SCD and should be carried out regularly in the young. With time, the investigation of SCD necessarily moved from the classic postmortem study to molecular autopsy. In conclusion, SCD prevention in the young has to be faced by an interdisciplinary team, including pathologists, cardiologists, sport physicians, and geneticists, with a translational approach; the clinicopathologic correlation method still being the polar-star. In other words, the game in the fight against SCD is still played in the anatomical theater, the place where "death enjoys to save lives."

SUDDEN CARDIAC DEATH AND WOLFF-PARKINSON-WHITE ELECTROCARDIOGRAPHIC PATTERN: A REVIEW

The causes of sudden cardiac death in patients with Wolff-Parkinson-White syndrome are considered; necessity of endocardial electrophysiological study and radiofrequency catheter ablation is discussed, including asymptomatic patients with accessory pathways.

Radiofrequency ablation for pre-excitation syndromes and AV nodal re-entrant tachycardia

Radiofrequency catheter ablation for supraventricular tachycardia was introduced in 1990. Since then it has become the standard for definitive treatment of pre-excitation syndromes and atrioventricular re-entrant tachycardia. In general, catheter ablation of supraventricular tachycardia results in improved outcomes compared to pharmacologic treatment. Over 95% of patients will be successfully treated with catheter ablation with less than a 5% chance of recurrence and <1% risk of major complications.

Origin and development of the atrioventricular myocardial lineage: insight into the development of accessory pathways

Defects originating from the atrioventricular canal region are part of a wide spectrum of congenital cardiovascular malformations that frequently affect newborns. These defects include partial or complete atrioventricular septal defects, atrioventricular valve defects, and arrhythmias, such as atrioventricular re-entry tachycardia, atrioventricular nodal block, and ventricular preexcitation. Insight into the cellular origin of the atrioventricular canal myocardium and the molecular mechanisms that control its development will aid in the understanding of the etiology of the atrioventricular defects. This review discusses current knowledge concerning the origin and fate of the atrioventricular canal myocardium, the molecular mechanisms that determine its specification and differentiation, and its role in the development of certain malformations such as those that underlie ventricular preexcitation.

Atrial Fibrillation in the Wolff-Parkinson-White Syndrome

Since the advent of catheter ablation for atrial fibrillation (AF) aiming the pulmonary veins a few years ago, there has been an overwhelming interest and a dramatic increase in AF investigation. AF has a different dimension in the context of the Wolff-Parkinson-White (WPW) syndrome. Indeed, AF may be a nightmare in a young person that has an accessory pathway (AP) with fast anterograde conduction. It may be life-threatening if an extremely rapid ventricular response develops degenerating into ventricular fibrillation. Therefore, it is very important to know the mechanisms involved in the development of AF in the WPW syndrome. There are several possible mechanisms that may be involved in the development of AF in the WPW syndrome, namely, spontaneous degeneration of atrioventricular reciprocating tachycardia into AF, the electrophysiological properties of the AP, the effects of AP on atrial architecture, and intrinsic atrial muscle vulnerability. Focal activity, multiple reentrant wavelets, and macroreentry have all been implicated in AF, perhaps under the further influence of the autonomic nervous system. AF can also be initiated by ectopic beats originating from the pulmonary veins, and elsewhere. Several studies demonstrated a decrease incidence of AF after successful elimination of the AP, suggesting that the AP itself may play an important role in the initiation of AF. However, since AF still occurs in some patients with the WPW syndrome even after successful ablation of the AP, there should be other mechanisms responsible for the development of AF in the WPW syndrome. There is a clear evidence of an underlying atrial muscle disease in patients with the WPW syndrome. Atrial myocardial vulnerability has been studied performing an atrial endocardial catheter mapping during sinus rhythm, and analizing the recorded abnormal atrial electrograms. This review analizes the available data on this singular setting since AF has a reserved prognostic significance in patients with the WPW syndrome, and has an unusually high incidence in the absence of any clinical evidence of organic heart disease.

Defective Tbx2-dependent patterning of the atrioventricular canal myocardium causes accessory pathway formation in mice

Ventricular preexcitation, a feature of Wolff-Parkinson-White syndrome, is caused by accessory myocardial pathways that bypass the annulus fibrosus. This condition increases the risk of atrioventricular tachycardia and, in the presence of atrial fibrillation, sudden death. The developmental mechanisms underlying accessory pathway formation are poorly understood but are thought to primarily involve malformation of the annulus fibrosus. Before birth, slowly conducting atrioventricular myocardium causes a functional atrioventricular activation delay in the absence of the annulus fibrosus. This myocardium remains present after birth, suggesting that the disturbed development of the atrioventricular canal myocardium may mediate the formation of rapidly conducting accessory pathways. Here we show that myocardium-specific inactivation of T-box 2 (Tbx2), a transcription factor essential for atrioventricular canal patterning, leads to the formation of fast-conducting accessory pathways, malformation of the annulus fibrosus, and ventricular preexcitation in mice. The accessory pathways ectopically express proteins required for fast conduction (connexin-40 [Cx40], Cx43, and sodium channel, voltage-gated, type V, α [Scn5a]). Additional inactivation of Cx30.2, a subunit for gap junctions with low conductance expressed in the atrioventricular canal and unaffected by the loss of Tbx2, did not affect the functionality of the accessory pathways. Our results suggest that malformation of the annulus fibrosus and preexcitation arise from the disturbed development of the atrioventricular myocardium.

Adding an electrocardiogram to the pre-participation examination in competitive athletes: a systematic review

No matter how rare, the death of young athletes is a tragedy. Can it be prevented? The European experience suggests that adding the electrocardiogram (ECG) to the standard medical and family history and physical examination can decrease cardiac deaths by 90%. However, there has not been a randomized trial to demonstrate such a reduction. While there are obvious differences between the European and American experiences with athletes including very differing causes of athletic deaths, some would highlight the European emphasis on public welfare vs the protection of personal rights in the USA. Even the authors of this systematic review have differing interpretation of the data: some of us view screening as a hopeless battle against Bayes, while others feel that the ECG can save lives. What we all agree on is that the USA should implement the American Heart Association 12-point screening recommendations and that, before ECG screening is mandated, we need to gather more data and optimize ECG criteria for screening young athletes.

Risk factors for atrioventricular tachycardia degenerating to atrial flutter/fibrillation in the young with Wolff-Parkinson-White

BACKGROUND

Atrioventricular reciprocating tachycardia (AVRT) is common in patients (pts) with Wolff-Parkinson-White (WPW) syndrome but atrial flutter/fibrillation (AF) with rapid ventricular response (RVR) is rare. Although AF occurs in 18% of adult WPW pts, its incidence in children is unknown. We sought to determine risk factors for AVRT spontaneously degenerating to AF during electrophysiologic studies (EPS) in children with WPW.

METHODS

This was a retrospective study of children with WPW referred for accessory pathway (AP) ablation without clinical AF. Standard electrophysiologic protocols were performed to induce AVRT. To determine if AF degeneration was associated with patient characteristics, 2-sample t-tests, Chi-square, and Fisher's exact were used.

RESULTS

There were 53 (31 males) WPW pts studied. During EPS, AVRT degenerated to AF in 27/53 (51%). RVR was seen in 18/27 (67%) patients. The ventricular cycle length (CL) during AF was shorter with RVR (211 + 24 ms) than without (313 + 65 ms) (P = 0.01). AF occurred more commonly among patients with right anterior AP (P = 0.05). Patient gender, age, height, weight, body surface area, persistence of preexcitation on exercise testing, baseline CL, AVRT conduction, and AP number were not significant AF determinants. The AVRT CL was significantly shorter in patients with (265.2 + 41.5 ms) versus those without (308 + 59 ms) AF (P = 0.01). Preliminary data suggest that AP location may be related to patient ethnicity.

CONCLUSION

AF with RVR occurred following AVRT induction during EPS in 34% of our WPW patients, typically associated with right-sided AP locations. Time intervals for RVR to degenerate into ventricular fibrillation and lead to SCD are yet to be determined.

Upstream Therapy for Atrial Fibrillation

There are multiple factors for the etiology of atrial fibrillation (AF), including stretch, autonomic imbalance, hyperthyroidism, and inflammation. Of these factors for AF, stretch and inflammation increase the angiotensin II level, thereby inducing calcium over load, and inducing ectopic focal activities that initiate AF. Angiotensin II activates the Erk cascade through the AT(1)R and induces interstitial fibrosis of the atria, which compromises intra-atrial conduction. Short atrial refractoriness and slow conduction form multiple re-entry, before maintaining AF. Anti-arrhythmic drugs used for downstream therapy can suppress the focal activities and re-entry, but cannot prevent the development of a structural substrate. In contrast, angiotensin-converting enzyme, angiotensin II type 1 receptor blocker and statins might constitute upstream therapy through the prevention of structural remodeling that promotes AF.

Statin Use before By-Pass Surgery Decreases the Incidence and Shortens the Duration of Postoperative Atrial Fibrillation

BACKGROUND

The aim of the present observational study is to search the incidence of postoperative atrial fibrillation (AF) in patients with or without preoperative statin treatment.

METHODS AND RESULTS

The population consisted of 362 consecutive patients (267 on and 95 not on statin). Diabetes mellitus was more frequent in statin group (p = 0.03). Other demographic and procedural variables were similar in the both groups (All p > 0.05). Postoperative AF was less frequent and its duration was shorter in statin group compared to non-statin group (p = 0.03 and 0.0001, respectively). The Kaplan-Meier analysis showed the protective effect of statins against the risk of developing AF (p = 0.01).

CONCLUSION

Statin treatment before the by-pass surgery decreases the incidence and shortens the duration of postoperative AF.