Mahaim Fibers Research Articles

Ventricular insertion site ablation of a Mahaim atriofascicular fibre in Ebstein anomaly.

Ebstein anomaly is frequently associated with accessory pathways, including Mahaim atriofascicular fibres. We herein illustrate successful Mahaim fibre ablation in Ebstein anomaly by targeting the ventricular insertion site below the tricuspid ridge.

Clinical, electrophysiological, molecular, and genetic characteristics of patients with Wolf–Parkinson–White syndrome: literature review

The WolfParkinsonWhite (WPW) syndrome is a condition with early excitation of the heart ventricles due to the conduction of an electrical pulse along the atrioventricular pathway, such as the Kent, James bundle, and Mahaim fibers; the pulse is usually accompanied by supraventricular tachycardia, atrioventricular reciprocal tachycardia in 95% of cases, and fibrillation, atrial flutter, and other supraventricular tachycardia in other cases. WPW syndrome can be observed in patients of any age, approximately 130 per 10,000 people, with male predominance. The disease affects 0.150.25% of the population. Sudden cardiac death occurs in one patient per 1000 annually, and sometimes this is the first "business card" of the disease. This is mainly due to the lightning-fast formation of life-threatening arrhythmias, for example, with the transformation of atrial fibrillation into ventricular fibrillation. The morphological substrate is an additional atrioventricular connection. Currently, transcatheter radiofrequency ablation is the standard of the interventional treatment of WPW syndrome. WPW syndrome has a diverse etiology. Numerous studies reported that genetics play a significant role in the development of WPW syndrome. Several genetic predictors of WPW syndrome are presented in the modern literature, which may be relevant in predicting and diagnosing hidden forms of this syndrome, such as course, development of symptoms and manifestations, and reduction of the risks of sudden cardiac death.

Autopsy for Medical Diagnostics: Finding the Cause of Sudden Unexpected Death through Investigation of the Cardiac Conduction System by Serial Sections.

Sudden unexpected death (SUD) is a fatal event that occurs in an apparently healthy subject in a way that such an abrupt outcome could have not been predicted. SUD-including sudden intrauterine unexplained death (SIUD), sudden neonatal unexpected death (SNUD), sudden infant death syndrome (SIDS), sudden unexpected death of the young (SUDY), and sudden unexpected death in the adult (SUDA)-occurs as the first manifestation of an unknown underlying disease or within a few hours of the presentation of a disease. SUD is a major unsolved, shocking form of death that occurs frequently and can happen at any time without warning. For each case of SUD, a review of clinical history data and performance of a complete autopsy, particularly focused on the study of the cardiac conduction system, were carried out according to the necropsy protocol devised by the Lino Rossi Research Center, Università degli Studi di Milano, Italy. Research cases collected and selected for this study were represented by 75 SUD victims that were subdivided into 15 SIUD, 15 SNUD, 15 SUDY, and 15 SUDA victims. After a routine autopsy and clinical history analysis, death remained unexplained, and hence a diagnosis of SUD was assigned to 75 subjects, which included 45 females (60%) and 30 (40%) males ranging in age from 27 gestational weeks to 76 years. Serial sections of the cardiac conduction system disclosed frequent congenital alterations of the cardiac conduction system in fetuses and infants. An age-related significant difference in distribution among the five age-related groups was detected for the following anomalies of the conduction system: central fibrous body (CFB) islands of conduction tissue, fetal dispersion, resorptive degeneration, Mahaim fiber, CFB cartilaginous meta-hyperplasia, His bundle septation, sino-atrial node (SAN) artery fibromuscular thickening, atrio-ventricular junction hypoplasia, intramural right bundle branch, and SAN hypoplasia. The results are useful for understanding the cause of death for all SUD cases that were unexpected and would have otherwise remained unexplained, so as to motivate medical examiners and pathologists to perform more in-depth studies.

Electrophysiological characteristics of right- and left-sided Mahaim accessory pathways: A single-center experience in China.

Mahaim-type accessory pathways (MAPs) are rare accessory pathways (APs) with specific properties. They are mostly located in the right side of the heart but rarely exist on the left side. This study aims to analyze the clinical and electrophysiological (EP) characteristics of both-sided MAPs. A total of 2,249 patients with AP from our center were enrolled between 1 January 2011 and 27 March 2022. During the EP study (EPS) 17 patients were diagnosed with MAPs (right-sided: n = 13, left-sided: n = 4) according to the properties of Mahaim fibers. MAPs constitute 0.75% of all APs. Out of 1,553 patients with left-sided APs, four patients (0.26%) were diagnosed with Mahaim fiber-mediated tachycardia. Out of 696 patients with right-sided APs, 13 patients (1.9%) were diagnosed with Mahaim fiber. Most Mahaim fibers were located at the free wall of the tricuspid and mitral annuli. Seven patients of right-sided MAPs were of atriofasicular type, six patients had right-sided MAPs, and all of the patients with left-sided MAPs were of atrioventricular (AV) type. The M potential only was detected in long-length MAPs. Coexistence with other supraventricular tachycardias (SVTs) was also observed both in patients with right-sided and left-sided MAPs. All the patients underwent radiofrequency ablation successfully. Only one patient had tachycardia recurrence during a follow-up. Although MAPs are commonly located at right sides, left sites are not impossible. The M potential contributes to the improvement of the successful ablation.

P172 AN ACCESSORY PATHWAY WITHOUT REENTRANT TACHYCARDIA

Abstract A 65–year–old patient, hypertensive, dyslipidemic, strong smoker. He has heart disease with hypokinetic evolution EF 47%, mild MI. Negative Dipyridamole–stress echocardiography dated January 2008. Recently atrial fibrillation (AF) is found and anticoagulant therapy was started. Dyspnea and weight loss occurred in past two months. Detected keratinizing squamous pulmonary Ca with negative markers. This injury was judged to be inoperable, and the patient get indications for chemotherapy and radiotherapy. The patient also starts complaining of dyspnea and chest pain on exertion: Not serological modification, not ischemic ECG. Echocardiogram LVEF 47–50% highlights diffuse hypokinesia, regular valves. Ergometric test was not evaluable for ischemia. Coronary angiography shows stenosis of proximal and middle anterior interventricular coronary and non–critical lesions of circumflex and right coronary. Ecodobutamine test was positive for ischemia and arrhythmias (AF and wide QRS tachycardias in recovery phase), but negative for angor. The patient was treated with CT and IVA I – II. angioplasty Monitoring shows AF with high penetrance, wide QRS tachycardia runs and very short TVNS. ECG 1: During atrial tachycardia, show broad QRS conduction to BBSX alternating with narrow QRS with the same RR interval. ECG 2. show fusion between the wavefront conducted with narrow QRS and that with wide QRS. These are supraventricular arrhythmias that run along the atrioventricular nodal pathway (NAV) in the narrow QRS tracts and take an accessory pathway in the wide QRS run. The Mahaim fibers have decremental conductivities like the AV node, therefore high ventricular frequencies does not occur AF appeared during ecodobutamine, but some beats were conducted by an anomalous path in a discontinuous way); they are generally directed from the atrium or the NAV, towards another part of the right ventricular conduction system, with atrium wave or NAV – RB, therefore the early activation of the RB generates a widened QRS, with a LBB morphology. ECG 3 Re–entry on Mahaim pathway, ventricular activation widened through Mahaim fiber, which generate LBB morphology with retrograde atrial depolarization. In this case there is no reentry, but we have an atrial tachycardia conducted alternately on an accessory pathway and across the NAV. Given the patient‘s clinical problems and the total absence of symptoms, the patient remains asymptomatic during therapy with amiodarone and beta–blocker.

Characteristics of antegrade-only accessory pathways in children and adolescents.

There is minimal data regarding antegrade-only accessory pathways in young patients. Given evolving recommendations and treatments, retrospective analysis of the clinical and electrophysiologic properties of antegrade-only pathways in patients <21 years old was performed, with subsequent comparison of electrophysiology properties to age-matched controls with bidirectional pathways. Of 522 consecutive young patients with ventricular pre-excitation referred for electrophysiology study, 33 (6.3%) had antegrade-only accessory pathways. Indications included palpitations (47%), chest pain (25%), and syncope (22%). The shortest value for either the accessory pathway effective refractory period or the pre-excited R-R interval was taken for each patient, with the median of the antegrade-only group significantly greater than shortest values for the bidirectional group (310 [280-360] ms versus 270 [240-302] ms, p < 0.001). However, the prevalence of pathways with high-risk properties (effective refractory period or shortest pre-excited R-R interval <250 ms) was similar in both study patients and controls (13% versus 21%) (p = 0.55). Sixteen patients had a single antegrade-only accessory pathway and no inducible arrhythmia. Six patients had Mahaim fibres, all right anterolateral with inducible antidromic reciprocating tachycardia. However, 11 patients with antegrade-only accessory pathways and 3 with Mahaim fibres had inducible tachycardia due to a second substrate recognised at electrophysiology study. These included concealed accessory pathways (7), bidirectional accessory pathways (5), and atrioventricular node re-entry (2). Antegrade-only accessory pathways require comprehensive electrophysiology evaluation as confounding factors such as high-risk conduction properties or inducible Supraventricular Tachycardia (SVT) due to a second substrate of tachycardia are often present.

Pre-excitation cardiac problems in children: recognition and treatment.

The prevalence of ventricular pre-excitation is 0.07-0.2% in the pediatric population. Kent bundle is the most common atrioventricular accessory pathway and Mahaim fiber is relatively rare. Approximately, 30-60% of children with ventricular pre-excitation have onset of atrioventricular reentrant tachycardia. Persistent atrioventricular reentrant tachycardia can lead to tachycardiomyopathy. The anterograde conduction of right accessory pathway might lead to ventricular systolic dyssynchrony which might result in cardiac dysfunction even in patients with no tachycardia onset. This type of dilated cardiomyopathy was named as accessory pathway-induced dilated cardiomyopathy. Antiarrhythmic drugs can be used to acutely terminate tachycardia or taken orally to decrease tachycardia recurrence in the long term. However, antiarrhythmic drugs that can be chosen for children are quite limited. Sotalol has become a new choice. With the maturation of radiofrequency catheter ablation technique, progress in three-dimensional electro-anatomic mapping, use of cryoablation, and accumulation of experience in children with small age and weight, catheter ablation has become the first choice for children with pre-excitation syndrome.Conclusion: For ventricular pre-excitation co-exists with dilated cardiomyopathy, differential diagnosis of tachycardiomyopathy or accessory pathway-induced dilated cardiomyopathy should be considered. Catheter ablation (radiofrequency and cryoablation) is a relatively safe and effective treatment option and has become the first choice to treat children with ventricular pre-excitation. What is Known: • Persistent atrioventricular reentrant tachycardia in children can lead to tachycardiomyopathy; • Antiarrhythmic drugs that can be chosen for children are quite limited. What is New: • The anterograde conduction of right accessory pathway (not related to supraventricular tachycardia) might lead to accessory pathway-induced dilated cardiomyopathy. • Catheter ablation (including radiofrequency and cryoablation) has become the first choice for children with pre-excitation syndrome.

A case of a patient with heart failure caused by hyperthyroidism promoting pre-excitation of Mahaim fibers

A case of a patient with heart failure caused by hyperthyroidism promoting pre-excitation of Mahaim fibers

Mahaim fibers: Should they be renamed?

Mahaim fibers: Should they be renamed?

Perioperative management of patients with pre-excitation syndromes.

Patients with pre-excitation abnormalities are at a high risk for life-threatening perioperative arrhythmias. In Wolff-Parkinson-White syndrome, the anaesthetics used for invasive diagnostic testing/ablation, should not affect cardiac electrophysiology; propofol, sevoflurane, fentanyl, sufentanil, alfentanil are suitable. In non-ablative surgery, propofol, sevoflurane, isoflurane, fentanyl, alfentanil, sufentanil have been used safely. Among neuromuscular blockers, cis-atracurium, rocuronium and vecuronium are good choices. Ketamine, pancuronium and pethidine should be avoided because of their sympathomimetic actions. Anticholinergic/ anticholinesterase combinations for neuromuscular block reversal should preferably be omitted, while sugammadex seems more attractive. In regional anaesthesia, addition of epinephrine and high sympathetic blocks should be avoided. Hypotension should be treated with pure alpha-adrenergic agonists. Other pre-excitation abnormalities associated with different accessory pathways are the Mahaim Fiber and Lown-Ganong-Levine syndrome. Sympathetic activation should be avoided. Total intravenous anaesthesia with propofol probably represents the safest option. A careful anaesthetic plan and close cooperation with cardiologists are mandatory for successful management.

Comparison of the Accuracy of Three Algorithms in Predicting Accessory Pathways among Adult Wolff-Parkinson-White (WPW) Syndrome Patients in our Population

Background: after the introduction of catheter ablation of atrioventricular accessory pathways (APs) in Wolff-Parkinson-White (WPW) syndrome, to facilitate planned ablation and minimize catheter-related injury, predicting the AP was required. Localization of APs can be anywhere around the atrioventricular (AV) annuli, left- or right-sided, or within the septum or a rare possibility of Mahaim fibers. Objective: to compare between three algorithms in their accuracy in predicting the exact site of accessory pathway. Patients and Methods: one hundred patients with manifest pre-excitation who underwent electrophysiological study (EPS) and successful ablation of accessory pathway who were subjected to history taking, complete physical examination stressing on 12-lead of pre-excited electrocardiogram (ECG). Results: the distributions of the accessory pathway with left lateral accessory pathway being the most prevalent (27%) while the postero-lateral being the least prevalent one (2%) and that Right-sided accessory pathway was most frequently predicted by Arruda algorithm in 31% of patients and least frequently predicted by D’Avila in 17% of patients while its actually present in 23% of patients according to the EP study, Left-sided accessory pathway was most frequently predicted by D’Avila (61%) and least frequently predicted by Arruda (49%) whereas it was truly present in 51% of patients according to EP study. Mid and antero-septal accessory pathways were most frequently predicted by Chiang and least frequently predicted by Arruda while it was present in 26% of cases proved by EP study. In all algorithms, 72 % of predictions were correct for Chiang, 81 % for D’Avila, and 71 % for Arruda and the percentage of predictive accuracy of all algorithms did not differ between the algorithms (p=1.000; p=0.076; p=0.064, respectively) The best algorithm for prediction of right-sided and left-sided accessory pathways was D’Avila (p<0.001). The best algorithm that is particularly useful in predicting antero-septal and mid-septal accessory pathways was Chiang (p<0.001). Conclusion: prior knowledge of the AP location allows better planning, faster and safer procedure, as well as decreased exposure to ionizing radiation and unnecessary punctures. In all algorithms, 72% of predictions were correct for Chiang, 81% for D'Avila, and 71% for Arruda and the percentage of predictive accuracy of all algorithms did not differ between the algorithms (p=1.000; p=0.076; p=0.064, respectively). The best algorithm for prediction of right-sided and left-sided accessory pathways was D'Avila (p<0.001). The best algorithm that is particularly useful in predicting anteroseptal and mid-septal accessory pathways was Chiang (p<0.001).

Comparison of the Accuracy of Three Algorithms in Predicting Accessory Pathways among Adult Wolff-Parkinson-White (WPW) Syndrome Patients in our Population

Background: after the introduction of catheter ablation of atrioventricular accessory pathways (APs) in Wolff-Parkinson-White (WPW) syndrome, to facilitate planned ablation and minimize catheter-related injury, predicting the AP was required. Localization of APs can be anywhere around the atrioventricular (AV) annuli, left- or right-sided, or within the septum or a rare possibility of Mahaim fibers. Objective: to compare between three algorithms in their accuracy in predicting the exact site of accessory pathway. Patients and Methods: one hundred patients with manifest pre-excitation who underwent electrophysiological study (EPS) and successful ablation of accessory pathway who were subjected to history taking, complete physical examination stressing on 12-lead of pre-excited electrocardiogram (ECG). Results: the distributions of the accessory pathway with left lateral accessory pathway being the most prevalent (27%) while the postero-lateral being the least prevalent one (2%) and that Right-sided accessory pathway was most frequently predicted by Arruda algorithm in 31% of patients and least frequently predicted by D’Avila in 17% of patients while its actually present in 23% of patients according to the EP study, Left-sided accessory pathway was most frequently predicted by D’Avila (61%) and least frequently predicted by Arruda (49%) whereas it was truly present in 51% of patients according to EP study. Mid and antero-septal accessory pathways were most frequently predicted by Chiang and least frequently predicted by Arruda while it was present in 26% of cases proved by EP study. In all algorithms, 72 % of predictions were correct for Chiang, 81 % for D’Avila, and 71 % for Arruda and the percentage of predictive accuracy of all algorithms did not differ between the algorithms (p=1.000; p=0.076; p=0.064, respectively) The best algorithm for prediction of right-sided and left-sided accessory pathways was D’Avila (p<0.001). The best algorithm that is particularly useful in predicting antero-septal and mid-septal accessory pathways was Chiang (p<0.001). Conclusion: prior knowledge of the AP location allows better planning, faster and safer procedure, as well as decreased exposure to ionizing radiation and unnecessary punctures. In all algorithms, 72% of predictions were correct for Chiang, 81% for D'Avila, and 71% for Arruda and the percentage of predictive accuracy of all algorithms did not differ between the algorithms (p=1.000; p=0.076; p=0.064, respectively). The best algorithm for prediction of right-sided and left-sided accessory pathways was D'Avila (p<0.001). The best algorithm that is particularly useful in predicting anteroseptal and mid-septal accessory pathways was Chiang (p<0.001).

Wide QRS complex supraventricular tachycardia with negative precordial concordance: Electrocardiographic clues for Mahaim pathway with Ebstein anomaly

Ebstein's anomaly is often accompanied by either Wolff-Parkinson-White syndrome or atriofascicular Mahaim. These bypass tracts give rise to antidromic atrioventricular (AV) re-entrant tachycardias, in which the bypass tract serves as the anterograde limb of the circuit and the AV node as the retrograde limb of the reentrant circuit. Since the antidromic AV reentrant tachycardia over a Mahaim fibre has a typically left bundle braunch block (LBBB) morphology, it is easy to make a misdiagnosis of supraventricular tachycardia with functional LBBB or even of ventricular tachycardia particularly in the presence of negative concordance. Some electrocardiographic clues might prevent misdiagnosis of ventricular tachycardia and inadvertent ICD implantation.

The double adenosine test: A simple and non-invasive tip to unmask unapparent pre-excitations at the emergency department

We describe a simple method to unmask unapparent pre-excitations at the emergency room. This method allows a non-invasive and definite diagnosis of accessory pathways capable of anterograde conduction. In patients presenting with paroxysmal SVT, close inspection of the electrocardiogram during sinus rhythm should look for a pre-excitation. Unfortunately, a pre-excitation can be completely unapparent during sinus rhythm despite the presence of an antegradely conducting accessory pathway. This is typically the case in the so-called Mahaim fibers. These bypass tracts give rise to antidromic atrioventricular reentrant tachycardias, in which the bypass tract serves as the anterograde limb of the circuit and the atrioventricular node as the retrograde limb of the reentrant circuit. In these patients, it is easy to make a misdiagnosis of supraventricular tachycardia with functional left bundle branch block. Indeed, due to the slow and decremental conduction properties of these bypass tracts, the baseline ECG is either normal or shows only subtle pre-excitation. Herein, we describe a simple tip, consisting of two successive administrations of adenosine (during ongoing tachycardia [upper panel] and during sinus rhythm [lower panel]), to make a non-invasive and definite diagnosis of this condition at the emergency department. By blocking the anterograde conduction over the atrioventricular node, adenosine infusion during sinus rhythm will indeed result in ventricular activation occurring exclusively over the accessory pathway. Importantly, the use of this simple method to unmask accessory pathways capable of anterograde conduction is not limited to the diagnosis of Mahaim fibers. Indeed, it can be used more generally in patients presenting with paroxysmal SVT whenever the ECG following tachycardia termination does not definitely rule out the presence of an accessory pathway ( Fig. 1 ).

Atriofascicular Mahaim with Ebstein anomaly: A case report

We report a case of a 7-year-old girl with atriofascicular Mahaim (AFM) pathway concomitant with Ebstein's anomaly. The QRS wave showed left bundle branch block pattern on electrocardiogram. Holter electrocardiogram showed prolongation of the PR interval and QRS morphological change during sinus tachycardia. An electrophysiological study demonstrated that the distal His potential appeared earlier than the proximal His potential, which suggested retrograde His conduction toward the atrioventricular node. Conduction from the Mahaim fiber to the His bundle was faster than that from the atrioventricular node towards the His bundle. The findings of this important case allowed a differential diagnosis between AFM and Wolff-Parkinson-White (WPW) syndrome.

Anatomopathological changes of the cardiac conduction system in sudden cardiac death, particularly in infants: advances over the last 25 years.

Sudden cardiac death (SCD) is defined as the unexpected death without an obvious noncardiac cause that occurs within 1 h of witnessed symptom onset (established SCD) or within 24 h of unwitnessed symptom onset (probable SCD). In the United States, its incidence is 69/100,000 per year. Dysfunctions of the cardiac conduction and autonomic nervous systems are known to contribute to SCD pathogenesis, even if most clinicians and cardiovascular pathologists lack experience with detailed examination of the cardiac conduction system and fail to recognize lesions that are crucial to explain the SCD itself. In this review, we sought to describe the advances over the last 25 years in the study of the anatomopathological changes of the conducting tissue, in SCD, in mature hearts and particularly in sudden infant death syndrome (SIDS) and sudden intrauterine unexpected death syndrome (SIUDS), through the articles published in our journal Cardiovascular Pathology (CVP). We carried out an extensive Medline search to retrieve and review all articles published in CVP in which the sudden unexpected death of one or more subjects believed healthy was reported, especially if associated with lesions of the conducting tissue in settings that revealed no other explained causes of death, particularly in infants and fetuses. The cardiac conduction findings of resorptive degeneration, His bundle dispersion, Mahaim fibers, cartilaginous meta-hyperplasia, persistent fetal dispersion, left-sided His bundle, septation of the bifurcation, atrioventricular node dispersion, sinus node hypoplasia, Zahn node, His bundle hypoplasia, atrioventricular node, and His bundle dualism were similarly detected in SIDS and SIUDS victims.

Congenital heart defects in adulthood : Supraventricular tachycardia

Supraventricular tachycardia (SVT) based on congenital substrates, such as accessory pathways or dual atrioventricular nodal properties, occur with an increased probability linked to specific congenital heart defects (CHDs). In the literature, the association of Ebstein's anomaly with accessory pathways and with Mahaim fibers is most prominent. Compared with patients with otherwise normal hearts, the clinical relevance of SVT is typically more severe and therefore antiarrhythmia treatment is anecessity in many cases. Diagnostics, pharmaceutical treatment, and interventional therapy of SVT in patients with CHD are often demanding owing to anatomical, hemodynamic, and electro-anatomical peculiarities. The use of antiarrhythmic medication is often limited because of intolerable side effects and a lack of reliability in suppressing arrhythmia relapses in the long term. Within the last 15-20years catheter ablation has thus become established as the first-choice treatment for SVT, even in patients with CHD. However, rates of success, recurrence, and risks are still inferior to those observed in patients with a normally functioning heart owing to the co-existence of vascular and cardiac anomalies, surgically created alterations, an unusual electro-anatomy, and lower tolerance to hemodynamic changes. Successful treatment in patients with CHDs and SVT requires adeep understanding and knowledge of all the disciplines discussed above and should only be practiced in dedicated centers, as patient numbers are small and therefore experience is limited.

Electrophysiological recognition of an atrio-ventricular mahaim fibre pathway

Mahaim fibres are cardiac accessory bundles which can cause dangerous tachyarrhythmias. Despite their first description being many y ears ago, their recognition and diagnosis still proves difficult. The electrocardiographic features of Mahaim pathways are subtle and shared with other accessory pathways; as such, an electrophysiology study must be used to diagnose this pathway. Even then, it is often a process of elimination which leads to the eventual diagnosis. Here, I will present the case of a young woman with a peculiar history who was ultimately diagnosed with a Mahaim fibre pathway. Using this case, I will describe the key electrophysiological features and the treatment of the Mahaim fibre pathway.

Electrophysiological recognition of an atrio-ventricular mahaim fibre pathway

Mahaim fibres are cardiac accessory bundles which can cause dangerous tachyarrhythmias. Despite their first description being many years ago, their recognition and diagnosis still proves difficult. The electrocardiographic features of Mahaim pathways are subtle and shared with other accessory pathways; as such, an electrophysiology study must be used to diagnose this pathway. Even then, it is often a process of elimination which leads to the eventual diagnosis. Here, I will present the case of a young woman with a peculiar history who was ultimately diagnosed with a Mahaim fibre pathway. Using this case, I will describe the key electrophysiological features and the treatment of the Mahaim fibre pathway.

Location.

Location.