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Background: Dexmedetomidine, an alpha 2 agonist, has emerged as a desirable sedative agent in the pediatric intensive care unit due to its minimal effect on respiratory status and reduction in delirium. Bradycardia and hypotension are common side effects, however there are emerging reports of more serious cardiovascular events, including sinus arrest and asystole. These case reports have been attributed to high vagal tone or underlying cardiac conduction dysfunction. Objectives: To describe the development of sinus arrest during sedation with dexmedetomidine in a patient without clinical features of high vagal tone, underlying cardiac conduction dysfunction, or intervening episodes of bradycardia. Case Presentation: An 11 month-old patient requiring sedation during mechanical ventilation for acute respiratory failure secondary to Adenovirus. To facilitate sedation, a dexmedetomidine infusion was initiated at.5 mcg/kg/hr and increased to maximum 1 mcg/kg/hr. Within 8 hours of initiating therapy, the patient had three episodes of sinus arrest. There was no intervening bradycardia between episodes and no further episodes occurred following discontinuation of dexmedetomidine. The patient did not have any clinical features associated with high vagal tone or underlying cardiac conduction dysfunction. Conclusions: As result of these findings, understanding risk factors for bradycardia, or more serious hemodynamic instability with dexmedetomidine infusions, is important to help identify high risk patients and weigh the associated risks and benefits of its administration. [ABSTRACT FROM AUTHOR]

Athletes undergo mandatory or voluntary cardiac testing, which may include 24-h ambulatory electrocardiogram monitoring. This study can on occasion disclose nocturnal pauses in otherwise asymptomatic healthy individuals. In some athletes, particularly those engaging in endurance or mixed sports, the pauses can be longer than 2–3 s and/or be caused by sinus arrest high-degree atrioventricular block not typical for physiological adaptation to exercise. The manuscript discusses the physiology and potential pathologies behind long nocturnal pauses in athletes. Several management strategies are proposed including emerging treatment techniques such as cardioneuroablation. [ABSTRACT FROM AUTHOR]

Abstract Background Diabetic ketoacidosis (DKA) is a serious, life-threatening condition known for its profound hydro electrolytic disturbances and multiple complications, including cerebral edema and circulatory collapse. While this complication is traditionally associated with patients suffering from type 1 diabetes, numerous studies have documented its non-negligible incidence in type 2 diabetics. However, conductive disorders that manifest during its course, such as sinus arrest, are poorly reported and can be life-threatening on their own when not promptly recognized and treated. The primary objective of this report is to increase awareness regarding the uncommon conduction complications associated with diabetic ketoacidosis, even in the absence of overt hyperkalemia, and to underscore the critical significance of early diagnosis and prompt intervention in managing these complications. Case presentation We present the case of a middle-aged man with past history of type 2 diabetes whose symptoms included asthenia and consciousness disorder concomitant with ketoacidosis decompensation. Electrocardiogram (ECG) revealed the presence of sinus arrest with ventricular escaping rhythm. Rapid management of the diabetic decompensation led to spontaneous restoration of normal sinus rhythm, thus obviating the necessity for permanent pacing in the patient. Conclusions Atypical complications arising during ketoacidosis decompensation, including conditions like sinus arrest, are frequently overlooked and tend to carry a guarded prognosis. Proper recognition and prompt treatment are imperative to achieve the optimal clinical outcome.

Athletes undergo mandatory or voluntary cardiac testing, which may include 24-h ambulatory electrocardiogram monitoring. This study can on occasion disclose nocturnal pauses in otherwise asymptomatic healthy individuals. In some athletes, particularly those engaging in endurance or mixed sports, the pauses can be longer than 2–3 s and/or be caused by sinus arrest high-degree atrioventricular block not typical for physiological adaptation to exercise. The manuscript discusses the physiology and potential pathologies behind long nocturnal pauses in athletes. Several management strategies are proposed including emerging treatment techniques such as cardioneuroablation.

Background and aim: Lithium is considered to be the first-line treatment for bipolar disorder, and paliperidone was approved for the treatment of schizophrenia and acute bipolar manic/mixed episodes. However, both agents have been associated with thyroid dysfunction and cardiovascular adverse effects like subclinical hypothyroidism, bradycardia, and sinus arrest, even at therapeutic doses. Case presentation: Here, we reported a case of a 17-year-old Han Chinese female who developed symptomatic hypothyroidism, sinus bradycardia, and sinus arrest while being treated with lithium and paliperidone for bipolar disorder with psychotic features including auditory hallucinations. Her workup suggested that these adverse effects might be related to the combined lithium and paliperidone treatment, although other causes could not be ruled out. After discontinuing both medications, her thyroid function and heart rhythm normalized over 20 days. Conclusion: To our knowledge, hypothyroidism, sinus bradycardia, and sinus arrest associated with the combined use of lithium and paliperidone had not been reported previously. Further research is warranted to elucidate the potential risks and benefits of this combination therapy for bipolar disorder with psychotic symptoms. [ABSTRACT FROM AUTHOR]

An 8-year-old neutered male Persian breed cat presented at the private practice for investigation of seizure-like episodes. An echocardiography revealed mild enlargement of the left atrium (La/AO: 1.73) with spontaneous echo contrast and mitral regurgitation. A left anterior fascicular block was also detected in the electrocardiogram. The cat had no response to the atropine response test. Aminophylline, pimobendan, clopidogrel, and furosemide were initially prescribed at the private clinic, and then the cat was referred to Prasu Arthon Animal Hospital, Faculty of Veterinary Science, Mahidol University, Thailand. Repeated echocardiogram and electrocardiogram demonstrated left atrium enlargement (La/AO: 1.85) and sinus arrest, respectively. The cat was diagnosed with feline nonspecific phenotype cardiomyopathy. As the cat has no improvement after aminophylline administration and the owners declined further management with pacemaker implantation, therefore, terbutaline at 0.625 mg/cat PO ql2h was given to replace aminophylline. The cat responded well to this prescription. The mean interval of each syncope episode was markedly increased. Terbutaline increased the mean syncopal episode interval from 8.4 days of aminophylline treatment to 15.5 days. In this case, terbutaline could increase the mean heart rate (MHR) to 190 bpm, which might be an advantage over aminophylline, which increased the MHR to 165 bpm. Unfortunately, the cat died 62 days after starting a new medication. The objective of this case report is to describe medical management in a cat with sinus arrest without atropine responsiveness by using oral terbutaline. [ABSTRACT FROM AUTHOR]

Abstract Background Intraoperative sinus arrest is rarely seen during zygomatic fracture treatment. The patient was diagnosed with sick sinus syndrome based on repeated postoperative sinus arrest, which could have resulted in death if diagnosed late, making this case very significant to report. Case presentation Sick sinus syndrome is an arrhythmia associated with reduced automaticity of the sinoatrial node or impaired sinoatrial node conduction. We report the case of a 67-year-old man diagnosed with the syndrome after a sinus arrest that occurred during a zygomatic fracture treatment. The patient had cheek pain and mouth opening disorder, dizziness after fainting and sustaining a facial injury. Preoperative examination determined that the syncope was due to drug-induced arrhythmia, and surgery was authorized after drug withdrawal. During the operation, sinus arrest was observed due to trigeminal vagal reflex, and heart rate was restarted by stopping the operation and chest compressions. After the surgery, the patient showed symptoms of dizziness and palpitations, and sinus arrest following atrial fibrillation and supraventricular tachycardia, which was diagnosed as sick sinus syndrome, and a pacemaker was implanted. Currently, 8 years have passed since the surgery, and there are no symptoms of mouth opening disorder, dizziness, or palpitations. Conclusions In the case of maxillofacial injuries due to syncope, cardiogenic syncope is a possibility, and repeated syncope is a risk for death due to delayed diagnosis. There are no reports of maxillofacial trauma leading to a diagnosis of sick sinus syndrome. The purpose of this case report is to disseminate the importance of diagnosing the cause of syncope as well as injury treatment.

Previously we showed the generation of a protein trap library made with the gene-break transposon (GBT) in zebrafish (Danio rerio) that could be used to facilitate novel functional genome annotation towards understanding molecular underpinnings of human diseases (Ichino et al, 2020). Here, we report a significant application of this library for discovering essential genes for heart rhythm disorders such as sick sinus syndrome (SSS). SSS is a group of heart rhythm disorders caused by malfunction of the sinus node, the heart's primary pacemaker. Partially owing to its aging-associated phenotypic manifestation and low expressivity, molecular mechanisms of SSS remain difficult to decipher. From 609 GBT lines screened, we generated a collection of 35 zebrafish insertional cardiac (ZIC) mutants in which each mutant traps a gene with cardiac expression. We further employed electrocardiographic measurements to screen these 35 ZIC lines and identified three GBT mutants with SSS-like phenotypes. More detailed functional studies on one of the arrhythmogenic mutants, GBT411, in both zebrafish and mouse models unveiled Dnajb6 as a novel SSS causative gene with a unique expression pattern within the subpopulation of sinus node pacemaker cells that partially overlaps with the expression of hyperpolarization activated cyclic nucleotide gated channel 4 (HCN4), supporting heterogeneity of the cardiac pacemaker cells.

BackgroundPathogenic/Likely pathogenic variants in DSP-encoded desmoplakin are strongly associated with arrhythmogenic cardiomyopathy (ACM). However, their contribution towards sinus node dysfunction has not been well-delineated.Case summaryA 74-year-old man with a pathogenic variant of DSP-encoded desmoplakin (c.478C >T; p.Arg160X) but no evidence of ACM presented with one episode of syncope in the setting of a gastrointestinal illness. Workup including echocardiography, cardiac magnetic resonance imaging, and Holter monitor did not show evidence of ACM or significant arrhythmias. One month later, he experienced several closely-spaced episodes of syncope associated with long sinus pauses and sinus arrest documented on telemetry. He underwent urgent dual chamber pacemaker implantation, during which a ventricular programmed stimulation study was performed and was negative for sustained ventricular arrhythmias. His syncopal episodes resolved and he had no recurrent events on three-month follow-up.DiscussionAs highlighted here, DSP-encoded desmoplakin pathogenic/Likely pathogenic variants may contribute to isolated sinus node dysfunction. This clinical link should be further explored in larger studies involving patients with DSP variants.

BackgroundCardioneuroablation (CNA) is recognized as a promising therapeutic option for adults with severe symptomatic bradycardia caused by excessive vagal tone. However, no pediatric cases have been reported to date. Therefore, the aim of this study is to evaluate the feasibility and efficacy of CNA in children.MethodsA 12-year-old male patient was hospitalized with symptoms of fatigue, palpitations, and syncope for more than 2 months, and was definitively diagnosed with functional sinoatrial node dysfunction by using a 12-lead electrocardiogram, 24-h Holter monitoring, loading dose of atropine test (0.04 mg/kg), and treadmill exercise test. Simultaneously, whole-exome sequencing was performed on the child and his core family members. After completing the preoperative examination and signing the informed consent form, the child underwent CNA therapy.ResultsFirst, the electroanatomic structures of both atria were mapped out by using the Carto 3 system, according to the protocol of purely anatomy-guided and local fractionated intracardiac electrogram–guided CNA methods. Then, the local fractionated intracardiac electrograms of each cardiac ganglionated plexus (GP), including the GP between the aortic root and the medial wall of the superior vena cava, the GP between the posterior wall of the coronary sinus ostium and the left atrium, the GP between the anterior antrum of the right superior pulmonary vein and the superior vena cava, the GP in the superolateral area around the root of the left superior pulmonary vein, the GP around the root of the right inferior pulmonary vein, and the GP around the root of the left inferior pulmonary vein, were used as targets for ablation at a power of 30 W with an ablation index of 350–400. At a 6-month follow-up, the child's heart rhythm saw a complete restoration to sinus rhythm and clinical symptoms disappeared.ConclusionThe first application of CNA in a child with symptomatic sinus bradycardia was achieved with better clinical outcomes. CNA can be carried out cautiously in children under suitable indications.

Paragangliomas are neural-crest-derived nonepithelial neuroendocrine tumors distributed along the parasympathetic and sympathetic nerves. To our knowledge, no studies were reported regarding sinus arrest on day 4 after paraganglioma resection. A 66-year-old female patient with a history of pulmonary vein isolation visited our department for sigmoid colon cancer treatment. Enhanced computed tomography revealed an enhanced small nodule-like lymph node near the root of the inferior mesenteric artery. The patient underwent laparoscopic colectomy with regional lymph node dissection. Postoperatively, paroxysmal atrial fibrillation attacks developed, and the patient resumed oral medication. Additionally, sinus arrest after tachycardia developed. Changing the oral medication could maintain her circulatory dynamics. Pathological examination revealed that differentiated tubular adenocarcinoma infiltrated the submucosa. Immunohistochemically, the excised nodule as a lymph node was considered a functional paraganglioma. Our case indicates that paraganglioma resection and oral medication resumption may contribute to sinus arrest. When arrhythmias affecting the circulation occur perioperatively, the presence of a catecholamine-producing tumor should be considered in addition to cardiac disease. [ABSTRACT FROM AUTHOR]

Mitochondrial Ca2 + uptake influences energy production, cell survival, and Ca2 + signaling. The mitochondrial calcium uniporter, MCU, is the primary route for uptake of Ca2 + into the mitochondrial matrix. We have generated a zebrafish MCU mutant that survives to adulthood and exhibits dramatic cardiac phenotypes resembling cardiomyopathy and sinus arrest. MCU hearts contract weakly and have a smaller ventricle with a thin compact layer and reduced trabecular density. Damaged myofibrils and swollen mitochondria were present in the ventricles of MCU mutants, along with gene expression changes indicative of cell stress and altered cardiac structure and function. Using electrocardiography, we found that MCU hearts display conduction system defects and abnormal rhythm, with extended pauses resembling episodes of sinus arrest. Together, our findings suggest that proper mitochondrial Ca2 + homeostasis is crucial for maintaining a healthy adult heart, and establish the MCU mutant as a useful model for understanding the role of mitochondrial Ca2 + handling in adult cardiac biology.

Objective: The treatment of syncope depends largely on its possible etiology. Therefore, identifying the cause of syncope is very important in treatment planning. Herein, we report an etiology of syncope caused by pulmonary hypertension (PH) associated with canine filariasis, followed by syncope due to bradyarrhythmia 1 year later. Materials and Methods: An 8-year-old male English Cocker Spaniel was referred to our hospital for a second opinion regarding syncope that the dog had started experiencing approximately 2 months prior. Based on the examination findings, we diagnosed that the fainting was due to heartworm disease and associated PH. After increasing the dose of pimobendan (0.50 mg/kg, q12h), the syncope subsided. However, syncope recurred on the 215th day of the first episode. Results: The findings that differed from those during the initial examination were that car¬diac arrest was observed for approximately 5 sec during auscultation, along with sinus arrest. Therefore, to further investigate for syncope, a Holter electrocardiograph was obtained for 3 days. Consequently, sinus arrest was identified as the etiology of the recurrent syncope, and the patient was diagnosed with sick sinus syndrome, Rubenstein classification type II. Following cilostazol (10 mg/kg, q12h) administration, the syncope subsided. Conclusion: This case reports syncope in a dog, which typically occurs due to different etiologies. When a dog has PH, it may be important to think about the possibility of arrhythmias caused by a bigger right heart. [J Adv Vet Anim Res 2022; 9(3.000): 440-446]

BACKGROUND: Primary hypokalemic periodic paralysis (HypoPP), a rare skeletal muscle channelopathy resulting in episodic muscle weakness or paralysis under hypokalemic conditions, is caused by autosomal-dominant genetic mutations. HypoPP limits physical activity, and cardiac arrhythmias during paralytic attacks have been reported. We describe a rare familial HypoPP case complicated by sinus arrest and syncope requiring urgent temporary pacemaker implantation. CASE REPORT: A 27-year-old Vietnamese man with a family history of periodic paralysis presented with his third attack of muscle weakness triggered by intense football training the previous day. Clinical and laboratory features justified a HypoPP diagnosis. During intravenous potassium replacement, the patient experienced syncopal sinus arrest requiring urgent temporary pacemaker implantation. The patient gradually improved, responding favorably to oral potassium supplements. Genetic testing revealed an Arg1132Gln mutation in the sodium ion channel (SCN4A, chromosome 17: 63947091). At discharge, the patient received expert consultation regarding nonpharmacological preventive strategies, including avoidance of vigorous exercise and carbohydrate-rich diet. CONCLUSIONS: No evidence has established a relationship between hypokalemia and sinus arrest, and no specific treatment exists for familial HypoPP due to SCN4A mutation. Clinician awareness of this rare condition will promote appropriate diagnostic approaches and management strategies for acute paralytic attacks. Treatment should be tailored according to HypoPP phenotypes and genotypes. [ABSTRACT FROM AUTHOR]

The brown bear Ursus arctos undergoes exceptional physiological adaptions during annual hibernation that minimize energy consumption, including profound decrease in heart rate, cardiac output, and respiratory rate. These changes are completely reversible after the bears reenter into the active state in spring. In this case report, we show episodes of sinus arrest in a hibernating Scandinavian brown bear and in humans, recorded by implantable loop recorders and discuss the possible underlying mechanisms. Lessons learned from cardiac adaptations in hibernating bears might prove useful in the treatment of patients with sinus node dysfunction. [ABSTRACT FROM AUTHOR]

Abstract The brown bear Ursus arctos undergoes exceptional physiological adaptions during annual hibernation that minimize energy consumption, including profound decrease in heart rate, cardiac output, and respiratory rate. These changes are completely reversible after the bears reenter into the active state in spring. In this case report, we show episodes of sinus arrest in a hibernating Scandinavian brown bear and in humans, recorded by implantable loop recorders and discuss the possible underlying mechanisms. Lessons learned from cardiac adaptations in hibernating bears might prove useful in the treatment of patients with sinus node dysfunction.

Rapid eye movement sleep-related bradyarrhythmia syndrome is a rare condition marked by abnormal sinus arrest or atrioventricular conduction disturbance blocks during REM sleep unassociated with sleep disordered breathing. We present a case of a young man without a cardiovascular history exhibiting pauses of up to 9.7 seconds during polysomnography (PSG). Initially referred for suspected obstructive sleep apnea due to nocturnal awakenings with shortness of breath, confusion, and dizziness. PSG results were unremarkable apart from electrocardiogram findings revealing prolonged sinus pauses related to REM sleep. Evaluation via extended 14-day patch monitor revealed an overall normal sinus rhythm with the lowest heart rate recorded at 14 beats per minute and 412 pauses exceeding 2 seconds, with the longest pause lasting 12.5 seconds during nocturnal hours. A permanent pacemaker was considered, but after shared decision making with the patient, the decision was to continue monitoring without any intervention., (© 2024 American Academy of Sleep Medicine.)

Previously we showed the generation of a protein trap library made with the gene-break transposon (GBT) in zebrafish (Danio rerio) that could be used to facilitate novel functional genome annotation towards understanding molecular underpinnings of human diseases (Ichino et al, 2020). Here, we report a significant application of this library for discovering essential genes for heart rhythm disorders such as sick sinus syndrome (SSS). SSS is a group of heart rhythm disorders caused by malfunction of the sinus node, the heart’s primary pacemaker. Partially owing to its aging-associated phenotypic manifestation and low expressivity, molecular mechanisms of SSS remain difficult to decipher. From 609 GBT lines screened, we generated a collection of 35 zebrafish insertional cardiac (ZIC) mutants in which each mutant traps a gene with cardiac expression. We further employed electrocardiographic measurements to screen these 35 ZIC lines and identified three GBT mutants with SSS-like phenotypes. More detailed functional studies on one of the arrhythmogenic mutants, GBT411, in both zebrafish and mouse models unveiled Dnajb6 as a novel SSS causative gene with a unique expression pattern within the subpopulation of sinus node pacemaker cells that partially overlaps with the expression of hyperpolarization activated cyclic nucleotide gated channel 4 (HCN4), supporting heterogeneity of the cardiac pacemaker cells.

A 65‐year‐old man presented with an acute ischaemic stroke due to right posterior cerebral artery occlusion, complicated by episodes of sinus arrest in the absence of intrinsic cardiac disease. His neurological deficits and sinus node dysfunction resolved following mechanical thrombectomy. We believe this to be a novel case where thrombectomy resulted in successful treatment of cerebral ischaemia mediated cardiac autonomic dysfunction. [ABSTRACT FROM AUTHOR]

Vasovagal syncope (VVS) or reflex is usually caused by physical and mental stress-related factors, like pain, anxiety, and fear, and it is one of the most frequent complications during dental treatment. Two patients, both with histories of dental phobia and of VVS during vaccination, venipuncture, and dental treatment with local anesthetics, were scheduled for dental treatment under intravenous (IV) sedation. However, both experienced episodes of VVS that occurred during venipuncture using a 24-gauge indwelling needle. We determined that pain was the main trigger of VVS for these patients and attempted to reduce venipuncture-associated pain using 60% lidocaine tape applied 3 hours before venipuncture at their next dental visits, respectively. Use of the lidocaine tape was successful and permitted comfortable placement of the IV catheter without any onset of VVS. [ABSTRACT FROM AUTHOR]

Background: The association of obstructive sleep apnea (OSA) with bradycardia is not well-characterized, which may confer significant morbidity and mortality if left untreated. We sought to clarify the prevalence of comorbid OSA and bradycardia, and the effect of continuous positive airway pressure (CPAP) therapy on bradycardia outcomes.Methods: We systematically searched four electronic databases (PubMed, Embase, Cochrane Library, Scopus) for randomized or observational studies reporting the co-prevalence of sleep apnea and bradycardia or evaluated the use of CPAP on the incidence of bradycardias. We used random-effects models in all meta-analyses and evaluated heterogeneity using I2.Results: We included 34 articles from 7204 records, comprising 4852 patients. Among patients with OSA, the pooled prevalence of daytime and nocturnal bradycardia were 25% (95% CI: 18.6 to 32.7) and 69.8% (95% CI: 41.7 to 88.2) respectively. Among patients with bradycardia, the pooled prevalence of OSA was 56.8% (95% CI: 21.5 to 86.3). CPAP treatment, compared to those without, did not significantly reduce the risk of daytime (two randomized trials; RR: 0.50; 95% CI: 0.11 to 2.21) or nocturnal bradycardia (one randomized-controlled trial and one cohort study; RR: 0.76; 95% CI: 0.48 to 1.20).Conclusions: This meta-analysis demonstrates a high comorbid disease burden between OSA and bradycardia. Future research should explore the treatment effect of CPAP on bradycardia incidence, as compared to placebo. [ABSTRACT FROM AUTHOR]

A 74-year-old Asian female with a history of hypertension and chronic obstructive pulmonary disease was admitted to hospital for coughing, shortness of breath and fatigue; her nasopharyngeal swab was positive for COVID-19. Lopinavir/ritonavir 800mg/200 mg, daily was started. On the third day of antiviral therapy, the patient complained of dizziness, nausea, she was disorientated, and electrocardiogram showed sinus arrest, junctional escape rhythm 36 beats per min. Patient was successfully treated by temporary pacemaker, normal sinus rhythm was reverted on a 3rd day after stopping the lopinavir/ritonavir treatment. She was discharged home in stable condition. Bradyarrhythmia in form of sinus arrest can develop during treatment with lopinavir/ritonavir. The temporal nature of the observed changes and the ECG finding suggests the use of L/R contributed to the changes. This case highlights off-label prescribing lopinavir/ritonavir outside of a clinical trial setting should be avoided until the data have proven that treatment benefit over placebo.

Introduction Although preoperative bradycardia has been reported in several pheochromocytoma cases, postoperative bradycardia has not. This is the first case report of complete atrioventricular dissociation and sinus arrest occurring after pheochromocytoma resection. Case presentation A 38‐year‐old woman was referred for a left adrenal incidentaloma. Twenty‐four hour urinary collection showed elevated noradrenaline. Iodine‐123‐meta‐iodobenzylguanidine scintigraphy showed high tracer uptake in the left adrenal region. Open left adrenalectomy was performed, and histopathological examination confirmed the diagnosis of pheochromocytoma. Thirty minutes following surgery, complete atrioventricular dissociation and sinus arrest developed. Vagal reflex attenuation due to decreased noradrenaline after tumor removal and perioperative pain and fear were believed to be the causes. A temporary pacemaker was implanted to prevent sudden death due to vagal overstimulation. Conclusion Vagal reflex attenuation after pheochromocytoma resection can result in complete atrioventricular dissociation and sinus arrest. Adequate preoperative preparation and close monitoring during and after surgery are imperative.

Abstract High dose melphalan is commonly used as a conditioning regimen for autologous stem cell transplantation in multiple myeloma. There are reports of adverse cardiac events with melphalan manifested by supraventricular tachycardia and atrial fibrillation. Here, we report a rare case of a 58 year old female with multiple myeloma, who developed sinus arrest after autologous stem cell transplantation using high dose melphalan as a conditioning regimen. It was severe and rare, therefore, monitoring for cardiac toxicity in patients receiving high-dose melphalan is mandatory.

Sinus arrest and inappropriate sinus bradycardia are sinus node dysfunction (SND), which cause loss of consciousness. Cardiac pacing is recommended in patients with symptoms, such as syncope or dizziness. Several conditions can induce these arrhythmias; however, whether or not intracranial infectious diseases, such as herpes simplex encephalitis (HSE), can cause secondary SND is unclear. We encountered a patient with sinus arrest and transient sinus bradycardia associated with HSE. Since cardiac pause was never monitored and the bradycardia improved after HSE treatment, HSE was suspected to be the cause of SND. Although the underlying mechanisms have not yet been completely elucidated, HSE may cause secondary SND.

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is the most common form of autoimmune encephalitis, presenting with various psychiatric manifestations, including behavioral and cognitive impairments, movement disorders, decreased consciousness, dysphasia, seizures, and autonomic dysfunction. Autonomic dysfunction may involve hyperthermia, apnea, hypotension, tachycardia, and life-threatening manifestations of sinus node dysfunction (SND), such as bradycardia, sinus pause or arrest, and asystole. The severity and significance of SND are critical, as it is not uncommon for these patients to progress into asystolic cardiac arrest, potentially contributing to morbidity and mortality. Accordingly, we present the case of an 18-year-old female with anti-NMDAR encephalitis who experienced multiple episodes of sinus pause/arrest and asystolic cardiac arrest, achieving a return of spontaneous circulation after successful CPR in all instances, ultimately requiring permanent pacemaker implantation. Additionally, we performed a literature review and analyzed 23 similar anti-NMDAR encephalitis cases with SND manifestations, including sinus pause/arrest or asystolic cardiac arrest, to identify common risk factors and describe management strategies and outcomes. Moreover, we investigated the potential association between teratoma and permanent pacemaker use in SND., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Khachatryan et al.)

Ticagrelor is a potent reversible P2Y12 inhibitor with proven superiority over clopidogrel. Ticagrelor increases the tissue concentration of adenosine, thereby leading to bradyarrhythmia. This complication is reported to occur very early after initiating the drug. A randomized controlled trial reported that ticagrelor-induced pauses have an early onset without much clinical impact. However, our patient developed ticagrelor-induced hemodynamically significant sinus arrest 10 months after coronary artery stenting, which improved after stopping the drug. Ticagrelor should be considered as one of the uncommon reasons for late-onset sinus pause or bradyarrhythmia. [ABSTRACT FROM AUTHOR]

While the indication for a pacemaker therapy in patients with high-degree AV block or symptomatic bradycardias is straightforward in most cases, intermittent oligo- and asymptomatic sinus bradycardias and pauses turn out to be more challenging. In this case report potential causes, diagnostic steps and possible therapies will be discussed. [ABSTRACT FROM AUTHOR]

Sinus arrest caused by sinus node (SN) artery occlusion during coronary intervention can take place, but it is usually transient and seldom influences hemodynamic instability. We encounter cases requiring revascularization of the SN artery because of cardiogenic shock, although it is very rare. Acute occlusion of SN artery during PCI should be noted, especially if hemodynamics is unstable.

Abstract Swallowing syncope is a rare medical condition. Even though it has been known as a neurally mediated syncope, the definitive mechanism of this condition remains unclear. We show in this study an additional case of swallowing syncope and review the 122 reported cases from the literature. A 47‐year‐old Japanese man had been suffering from recurrent syncopal attacks, when he fainted immediately after swallowing. Holter electrocardiogram monitoring demonstrated a sinus pause (maximum R‐R interval of 3.8 seconds) after he swallowed a noodle quickly. A permanent pacemaker was implanted because the frequency of syncope increased.

Keywords: Sinus arrest; Cardiac pacemaker; Diabetic ketoacidosis EN Sinus arrest Cardiac pacemaker Diabetic ketoacidosis 657 660 4 04/28/21 20210501 NES 210501 Introduction It is well known in clinical practice that metabolic acidosis sometimes leads to life-threatening conditions. The patient with partial loss of consciousness was diagnosed with DKA, and she experienced sick sinus syndrome leading to sinus arrest in the presence of regular pulsation maintained by the cardiac pacemaker. Taken together, it is likely that DKA was closely associated with sick sinus syndrome and that the intracellular electrolyte imbalance and metabolic acidosis led to the electrocardiogram abnormality which finally caused the reduction in heart rate and profound hypotension in this subject. [Extracted from the article]

COVID-19 infection is a new disease mainly affecting the respiratory system but is also accompanied by many extra-pulmonary manifestations. A case of a 47-year old male with unique myocardial fibrosis after COVID-19 infection involving the left ventricular wall, intraventricular septum and almost complete damage of interatrial septum, in combination with asymptomatic severe sinus arrest episodes related to mild obstructive sleep apnea syndrome is described here.

Mitochondrial Ca2 + uptake influences energy production, cell survival, and Ca2 + signaling. The mitochondrial calcium uniporter, MCU, is the primary route for uptake of Ca2 + into the mitochondrial matrix. We have generated a zebrafish MCU mutant that survives to adulthood and exhibits dramatic cardiac phenotypes resembling cardiomyopathy and sinus arrest. MCU hearts contract weakly and have a smaller ventricle with a thin compact layer and reduced trabecular density. Damaged myofibrils and swollen mitochondria were present in the ventricles of MCU mutants, along with gene expression changes indicative of cell stress and altered cardiac structure and function. Using electrocardiography, we found that MCU hearts display conduction system defects and abnormal rhythm, with extended pauses resembling episodes of sinus arrest. Together, our findings suggest that proper mitochondrial Ca2 + homeostasis is crucial for maintaining a healthy adult heart, and establish the MCU mutant as a useful model for understanding the role of mitochondrial Ca2 + handling in adult cardiac biology.

Percutaneous coronary artery intervention (PCI) carries the risk of occlusion of the sinus node branch (SNB) which can lead to sinus arrest (SA). Generally, PCI-related SA recovers spontaneously, with a favorable clinical course. Herein, we describe a case of SNB occlusion after PCI for the right coronary artery which resulted in SA, subsequent left atrial appendage thrombus, and cardiogenic cerebral embolism (CE). Ultimately, the patient died due to cardiogenic CE. We report on the mechanism of intracardiac thrombus formation and discuss CE prevention strategies after PCI. Based on our experience, the possibility of adverse events due to PCI-induced SA must be considered, although PCI-induced SA is generally expected to resolve. < Learning objective: Percutaneous coronary artery intervention (PCI) carries the risk of occlusion of the side branches, including the sinus node branch (SNB). The occlusion of the SNB can lead to sinus arrest (SA). Generally, PCI-related SA recovers spontaneously. However, it should be noted that persistent SA can result in thrombus formation and cerebral embolism.> [ABSTRACT FROM AUTHOR]

We present the case of a 93-year-old woman with dementia, with no pertinent cardiac history except for hyperlipidemia, who presented to the emergency department with six months of progressive dysphagia, weakness, and falls. While she had no seemingly cardiac symptoms and or remarkable cardiovascular examination features, the patient's initial electrocardiogram (ECG) showed occasional brief pauses with no atrial or ventricular activity. Computer interpretation of the rhythm was "sinus pause," but upon closer investigation, the true diagnosis was different, but with potential to be equally ominous if not accurately recognized and appropriately managed. [ABSTRACT FROM AUTHOR]

A 74-year-old woman presented to our hospital with syncope after a coronavirus disease 2019 (COVID-19) infection. Upon admission, she passed out, and an 8 second sinus arrest was detected during telemetry monitoring. During the next syncope episode, telemetry monitoring showed that her heart rate decreased from 80 to 36 bpm, accompanied by a 2.4 second pause. A permanent pacemaker was implanted; however, the patient still experienced syncope. The head-up tilt test revealed a vasodepressor reflex syncope. The need for permanent pacemakers in patients with syncope following COVID-19 therefore remains controversial.

Background: The head-up tilt test (HUT) and other evidence suggest that the vagal effect on the heart decreases with age., Objectives: The main aim of the study was to assess whether this age effect also affects the rate of asystole in spontaneous reflex syncope (RS)., Method: We performed an analysis of pooled individual data from 4 studies that recruited patients ≥40 years of age affected by certain or suspected RS who received an implantable loop recorder (ILR) and reported follow-up data on syncope recurrence. We assessed the presence of asystolic syncope of >3 seconds or nonsyncopal asystole of >6 seconds recorded by ILR and compared the findings to tilt test results on the same patients., Results: A total of 1,046 patients received ILR because of unexplained syncope. Of these, 201 (19.2%) had a documentation of an asystolic event of 10-second (Q1-Q3: 6- to 15-second) duration. They were subdivided in 3 age tertiles: ≤60 years (n = 64), 61 to 72 years (n = 72), and ≥73 years (n = 65). The rate of asystolic events was similar in the 3 subgroups (50.1%, 50.1%, and 49.2%, respectively; P = 0.99). Conversely, the rate of asystolic syncope induced during HUT (performed in 169 of 201) was greatly age dependent (31.0%, 12.1%, and 11.1% in increasing age tertiles, respectively; P = 0.009)., Conclusions: The rate of the spontaneous asystolic form of RS documented by ILR is constant at any age >40 years. Conversely, the rate of asystolic syncope induced by HUT is higher in younger patients and decreases with age. The contrasting results between spontaneous and tilt-induced events cast doubt on the concept that asystole in RS is less common in older patients., Competing Interests: Funding Support and Author Disclosures This research was partially funded by the Italian Ministry of Health. Dr Fedorowski has received consultancy and lecture fees from Medtronic Inc and Finapres Medical Systems for syncope investigation. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Mitochondrial Ca2 + uptake influences energy production, cell survival, and Ca2 + signaling. The mitochondrial calcium uniporter, MCU, is the primary route for uptake of Ca2 + into the mitochondrial matrix. We have generated a zebrafish MCU mutant that survives to adulthood and exhibits dramatic cardiac phenotypes resembling cardiomyopathy and sinus arrest. MCU hearts contract weakly and have a smaller ventricle with a thin compact layer and reduced trabecular density. Damaged myofibrils and swollen mitochondria were present in the ventricles of MCU mutants, along with gene expression changes indicative of cell stress and altered cardiac structure and function. Using electrocardiography, we found that MCU hearts display conduction system defects and abnormal rhythm, with extended pauses resembling episodes of sinus arrest. Together, our findings suggest that proper mitochondrial Ca2 + homeostasis is crucial for maintaining a healthy adult heart, and establish the MCU mutant as a useful model for understanding the role of mitochondrial Ca2 + handling in adult cardiac biology. [ABSTRACT FROM AUTHOR]

Background: The discussion about the feasibility of empiric pacemaker implantation in patients with preexisting atrioventricular (AV) conduction disorders continues. The aim of the study was to determine the etiology of syncope and the need for pacemaker insertion in patients with AV conduction impairment using implantable loop recorder (ILR). Methods: ILR was implanted after negative diagnostic workup in 37 patients with syncope (24 men, 13 women, age 72 ± 10 years) and preexisting impairment of AV conduction. First‐degree AV block (AVB I) was present in 26 patients, and bundle branch block (BBB) in 17 patients. Results: ILR‐based diagnosis was made in 28 patients (75%)—sinus arrest in 13 patients, complete AVB in 10 patients, and vasodepressor syncope in five patients. In patients with preexisting BBB, sinus arrest occurred during ILR monitoring significantly more frequently than in patients without BBB (53% vs 20%, P =.03). Complete AVB was significantly less common in patients with preexisting BBB than in patients without BBB (12% vs 40%, P =.04). On multivariate regression analysis, the only independent predictor of AVB occurrence during ILR monitoring was preexisting AVB I (P =.03). The only independent predictor of sinus arrest during ILR monitoring was preexisting BBB (P =.03). Conclusions: In patients with preexisting AV conduction disorders, prevailing syncopal mechanism during ILR monitoring was asystole. However, sinus arrest occurred more often than complete AVB and was predicted by preexisting BBB. Preexisting AVB was a predictor of complete AVB during ILR monitoring. [ABSTRACT FROM AUTHOR]

Background: Sleep apnea syndrome (SAS) and subarachnoid hemorrhage (SAH) are both considered possible causes of secondary arrhythmias. However, there are limited reports on the increased risk of bradyarrhythmia for arrhythmia-free SAS patients with SAH. Case Description: A 31-year-old woman with SAS developed low-grade SAH and underwent coil embolization on postbleed day 1. Following a coiling procedure, she experienced worsening episodes of sinus arrest lasting up to 12 s and required a temporary pacemaker. Frequent episodes of sinus arrest were detected for the next 4 days. Thereafter, all types of arrhythmias gradually decreased, and she eventually recovered to be arrhythmia free. Conclusion: Acceleration of sympathetic nervous activity caused by acute SAH may predispose patients to bradyarrhythmia with SAS and elicit asystole. The coexistence of SAS and SAH should be recognized as a cause of life-threatening sinus arrest, even if the severity of SAH is low grade. [ABSTRACT FROM AUTHOR]