暂无摘要。

In patients with a reduced left ventricular (LV) systolic function (ejection fraction < 35%) and a left bundle branch block with a QRS duration > 130 ms, cardiac resynchronization therapy (CRT) can contribute to an improvement in the quality of life and a reduction in mortality. The resynchronization is mostly achieved by pacing via an epicardial LV lead in the coronary sinus; however, this approach is often limited by the patient\'s venous anatomy and an increase in the stimulation threshold over time. In addition, up to 30% of patients do not respond to the intervention. New treatment approaches involve direct stimulation of the conduction system by pacing of the bundle of His or left bundle branch. This enables a more physiological propagation of the stimulus. Pacing of the left bundle branch is achieved by advancing the lead into the right ventricle and screwing it deep into the interventricular septum. Due to the relatively large target area of the left bundle branch the success rate is very high (currently > 90%). Observational studies have shown a greater reduction in the QRS duration, a more pronounced improvement in systolic function and a lower hospitalization rate for heart failure associated with conduction system pacing compared to CRT using a coronary sinus lead. These findings have been confirmed in small randomized trials. Therefore, the use of left bundle branch pacing should be considered not only as a bail out in the case of failed resynchronization using coronary sinus lead placement but increasingly also as an initial pacing strategy. The results of the first large randomized trials are expected to be released in late 2024.
UNASSIGNED: Bei Patienten mit einer reduzierten systolischen linksventrikulären (LV-)Funktion (Ejektionsfraktion < 35 %) und einem Linksschenkelblock (Breite des QRS-Komplexes > 130 ms) kann eine kardiale Resynchronisationstherapie (CRT) zur Verbesserung der Leistungsfähigkeit und zur Senkung der Mortalität beitragen. Die Resynchronisation wird zumeist durch Stimulation über eine epikardiale LV-Sonde im Koronarsinus erreicht. Diese Therapie ist jedoch häufig durch Variationen des Venensystems des Patienten und durch einen Anstieg der Reizschwelle im Laufe der Zeit limitiert. Zudem sprechen bis zu 30 % der Patienten nicht auf die Intervention an. Neue Therapieansätze beinhalten die direkte Stimulation des Erregungsleitungssystems durch His-Bündel- oder Linksschenkelstimulation. Hierdurch kann eine physiologischere Erregungsausbreitung erzielt werden. Die Linksschenkelstimulation wird durch das Einschrauben einer Sonde in das interventrikuläre Septum vom rechten Ventrikel aus erreicht. Durch das relativ große Zielgebiet des linken Tawara-Schenkels ist die Erfolgsrate sehr hoch (aktuell > 90 %). Beobachtungsstudien zeigen eine im Vergleich zur Resynchronisation mithilfe einer Koronarsinussonde stärkere Reduktion der QRS-Komplex-Breite, eine ausgeprägtere Verbesserung der systolischen Funktion und eine geringere Hospitalisierungsrate der Patienten mit einer Herzinsuffizienz. Ähnliche Ergebnisse finden sich in kleinen randomisierten Studien. Insbesondere die Anwendung der Linksschenkelstimulation wird nicht nur als Ersatz nach dem Scheitern der Resynchronisation mithilfe der Koronarsinussonde, sondern zunehmend auch als initiale Strategie unterstützt. Die Ergebnisse der ersten größeren randomisierten Studien sind ab Ende 2024 zu erwarten.

The electrical impulses that coordinate the sequential, rhythmic contractions of the atria and ventricles are initiated and tightly regulated by the specialized tissues of the cardiac conduction system. In the mature heart, these impulses are generated by the pacemaker cardiomyocytes of the sinoatrial node, propagated through the atria to the atrioventricular node where they are delayed and then rapidly propagated to the atrioventricular bundle, right and left bundle branches, and finally, the peripheral ventricular conduction system. Each of these specialized components arise by complex patterning events during embryonic development. This chapter addresses the origins and transcriptional networks and signaling pathways that drive the development and maintain the function of the cardiac conduction system.

The major events of cardiac development, including early heart formation, chamber morphogenesis and septation, and conduction system and coronary artery development, are briefly reviewed together with a short introduction to the animal species commonly used to study heart development and model congenital heart defects (CHDs).

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The heart is the first organ to form during embryonic development, establishing the circulatory infrastructure necessary to sustain life and enable downstream organogenesis. Critical to the heart\'s function is its ability to initiate and propagate electrical impulses that allow for the coordinated contraction and relaxation of its chambers, and thus, the movement of blood and nutrients. Several specialized structures within the heart, collectively known as the cardiac conduction system (CCS), are responsible for this phenomenon. In this review, we discuss the discovery and scientific history of the mammalian cardiac conduction system as well as the key genes and transcription factors implicated in the formation of its major structures. We also describe known human diseases related to CCS development and explore existing challenges in the clinical context.

Left ventricular noncompaction (LVNC), involving mainly the right ventricle, is a rare form of congenital heart disorder characterized by a developmental arrest in myocardial compaction, resulting in a spongy appearance of the myocardium, mainly of the right ventricle, rarely detected in fetuses. We report the case of a female fetus with a gestational age of 41+4 weeks who came to our attention for intrapartum sudden unexpected death, resulting in stillbirth. The ventricular walls, particularly the right ventricular wall, appeared thick, hypertrabeculated and spongy, leading to the diagnosis of LVNC involving mainly the right ventricle. The atrioventricular node and His bundle presented areas of fetal dispersion and resorptive degeneration; islands of conduction tissue were detected in the central fibrous body. Arcuate nucleus of the brainstem showed bilateral severe hypoplasia. The right bundle branch was hypoplastic. The final cause of death was an electrical conduction disfunction in an LVNC involving mainly the right ventricle. To the best of our knowledge, the herein described case is the first reported observation of sudden intrapartum death from LVNC involving mainly the right ventricle well documented post-mortem with cardiac conduction and brainstem studies. Our findings confirm the need of an accurate post-mortem examination including the study of the cardiac conduction system on serial section in every case of sudden unexpected fetal death, although there are no universally recognized guidelines.

This case report aims to highlight an atypical presentation of deceleration-dependent aberrancy (DDA) following the induction of general anesthesia in a patient with no known cardiac history. It emphasizes the critical role of intraoperative monitoring and the potential effects of anesthetic agents on the cardiac conduction system. A 46-year-old Hispanic male with no significant past medical or surgical history presented for surgical repair of a comminuted radial fracture. Following anesthesia induction with propofol, midazolam, and fentanyl, he developed a transient left bundle branch block (LBBB) exhibiting deceleration-dependent characteristics. Despite stable hemodynamics, the LBBB pattern appeared at heart rates below 60 beats per minute and resolved with heart rates above 90 beats per minute. This was managed intraoperatively with glycopyrrolate. Postoperative evaluations, including a 12-lead ECG, echocardiogram, and nuclear stress test, indicated normal biventricular function with a small to moderate reversible perfusion defect. The patient did not report cardiac symptoms postoperatively and did not prefer to undergo a coronary angiogram. This report underscores the importance of recognizing rate-dependent LBBB as a potential intraoperative complication, even in patients without pre-existing cardiac conditions. The transient nature of DDA, influenced by anesthetic agents and managed through careful monitoring and pharmacological intervention, highlights the necessity for vigilance in perioperative settings. This case contributes to a growing body of evidence suggesting that anesthetic management may require tailored approaches for patients experiencing or at risk for conduction abnormalities. This case illustrates the complexities of cardiac conduction disturbances such as DDA in the context of general anesthesia, serving as a reminder of the importance of thorough monitoring and the judicious use of rate-modifying drugs. It fosters a deeper understanding of the interaction between anesthesia and cardiac electrophysiology. Further research is needed to explore the mechanisms and management strategies for anesthetic-related cardiac conduction abnormalities.

BACKGROUND: Myocardial development is still transitioning by the time of birth making the cardiomyocyte vulnerable to maternal and perinatal factors. We aimed at investigating the impact of maternal and perinatal factors on the neonatal electrocardiogram.
METHODS: In a prospective cohort study, neonates underwent cardiac evaluation with electrocardiograms and echocardiograms (age 0-30 days). Associations between medical and demographic data, pregnancy, and birth-related factors, and electrocardiographic parameters were assessed.
RESULTS: A total of 15,928 singletons with normal echocardiograms were included (52% boys). Neonates were divided into groups by accumulated number of maternal/perinatal factors: 0, 1, 2, 3, 4, and ≥5, and between-group differences in electrocardiographic parameters were analysed. We observed an additive effect with a leftward shift of the QRS axis and QT prolongation (all p < 0.01). Comparing extreme groups (0 vs. ≥5 maternal/perinatal factors), we found a 4.3% more left-shifted QRS axis (117 vs. 112°, p < 0.001) and a 0.8% prolonged QTcFridericia (QTcF; 363 vs. 366 ms, p < 0.001); the effect on QTcF was most pronounced in neonates examined in the first week of life (360 vs. 368 ms, p < 0.0001).
CONCLUSIONS: We observed a cumulative effect of maternal and perinatal factors on neonatal electrocardiographic parameters, including a more left-shifted QRS axis and increased QT duration, although the variation was within normal reference ranges. Our findings add to the knowledge on the neonatal cardiac transition and the cardiac effect of maternal/perinatal factors.

UNASSIGNED: The 1.5 Tesla (T) Magnetic Resonance Linear Accelerator (MRL) provides an innovative modality for improved cardiac imaging when planning radiation treatment. No MRL based cardiac atlases currently exist, thus, we sought to comprehensively characterize cardiac substructures, including the conduction system, from cardiac images acquired using a 1.5 T MRL and provide contouring guidelines.
UNASSIGNED: Five volunteers were enrolled in a prospective protocol (NCT03500081) and were imaged on the 1.5 T MRL with Half Fourier Single-Shot Turbo Spin-Echo (HASTE) and 3D Balanced Steady-State Free Precession (bSSFP) sequences in axial, short axis, and vertical long axis. Cardiac anatomy was contoured by (AS) and confirmed by a board certified cardiologist (JR) with expertise in cardiac MR imaging.
UNASSIGNED: A total of five volunteers had images acquired with the HASTE sequence, with 21 contours created on each image. One of these volunteers had additional images obtained with 3D bSSFP sequences in the axial plane and additional images obtained with HASTE sequences in the key cardiac planes. Contouring guidelines were created and outlined. 15-16 contours were made for the short axis and vertical long axis. The cardiac conduction system was demonstrated with eleven representative contours. There was reasonable variation of contour volume across volunteers, with structures more clearly delineated on the 3D bSSFP sequence.
UNASSIGNED: We present a comprehensive cardiac atlas using novel images acquired prospectively on a 1.5 T MRL. This cardiac atlas provides a novel resource for radiation oncologists in delineating cardiac structures for treatment with radiotherapy, with special focus on the cardiac conduction system.