Inappropriate Sinus Tachycardia Research Articles

Robotic-enhanced hybrid ablation for inappropriate sinus tachycardia: a world-first approach.

We describe a world-first robotic ablation for inappropriate sinus tachycardia. A 26-year-old woman with refractory inappropriate sinus tachycardia underwent robotic-enhanced hybrid ablation, combining electrophysiological mapping with superior visualization and access compared to VATS approaches. Ablations normalized the heart rate from 120 to 70bpm. One month later, she reported symptom resolution and improved quality of life. Holter monitoring confirmed no tachycardic episodes. This presents a promising alternative for patients who have exhausted conventional treatments, potentially revolutionizing IST management.

The impact of regular physical training on the function of the autonomic nervous system in patients with inappropriate sinus tachycardia

Introduction: Sympathetic overactivity plays a crucial role in the pathogenesis of inappropriate sinus tachycardia (IST). It has been shown that regular physical activity positively affects the balance between the sympathetic and parasympathetic nervous systems, which may benefit patients with IST.Objective: This study aimed to assess the impact of regular physical training on the autonomic nervous system (ANS) function in patients with IST, focusing on heart rate variability (HRV) as an indicator of autonomic balance.Methods:The study included 32 female patients diagnosed with IST, with 16 in the study group (Group A) and 16 in the control group (Group B). The women in Group A participated in a structured physical training program lasting 12 weeks. HRV was analyzed based on 24-hour Holter monitoring recordings before and after the intervention. The statistical data obtained were presented as graphs illustrating changes in selected HRV parameters in response to physical training.Results:The study results indicate a significant improvement in heart rate variability (HRV) after 12 weeks of regular physical training in the study group. Notably, there was an increase in parameters associated with parasympathetic activity, such as the HF (High Frequency) index. Additionally, the SDNN index, which measures overall heart rate variability, also improved. These observations suggest that physical training contributed to an improvement in autonomic balance. The graphs in the study clearly depict changes in individual HRV parameters, confirming the positive impact of physical activity on the function of the autonomic nervous system in patients with IST.

β-Adrenergic receptor signalling pathway mediated antiarrhythmic activity of s-limonene in the rat heart.

S-Limonene (s-Lim) is a monocyclic monoterpene found in a variety of plants and has been shown to present antioxidant and cardioprotective activity in experimental models of myocardial infarction. The aim of this study was to evaluate the potential mechanism by which s-Lim exerts its antiarrhythmic effect, focusing on the blockade of β-adrenoceptor (β-AR) and its effects on various in vivo and in vitro parameters, including electrocardiogram (ECG) measurements, left ventricular developed pressure (LVDP), the β-adrenergic pathway, sarcomeric shortening and L-type calcium current (ICa,L). In isolated hearts, 10 μM of s-Lim did not alter the ECG profile or LVPD. s-Lim increased the heart rate corrected QT interval (QTc) (10.8%) at 50 μM and reduced heart rate at the concentrations of 30 (12.4%) and 50 μM (16.6%). s-Lim (10 μM) also inhibited the adrenergic response evoked by isoproterenol (ISO) (1 μM) reducing the increased of heart rate, LVDP and ECG changes. In ventricular cardiomyocyte, s-Lim antagonized the effect of dobutamine by preventing the increase of sarcomeric shortening, demonstrating a similar effect to atenolol (blocker β1-AR). In vivo, s-Lim antagonized the effect of ISO (agonists β1-AR), presenting a similar effect to propranolol (a non-selective blocker β-AR). In ventricular cardiomyocyte, s-Lim did not alter the voltage dependence for ICa,L activation or the ICa,L density. In addition, s-Lim did not affect changes in the ECG effect mediated by 5 μM forskolin (an activator of adenylate cyclase). In an in vivo caffeine/ISO-induced arrhythmia model, s-Lim (1 mg/kg) presented antiarrhythmic action verified by a reduced arrhythmia score, heart rate, and occurrence of ventricular premature beats and inappropriate sinus tachycardia. These findings indicate that the antiarrhythmic activity of s-Lim is related to blockade of β-AR in the heart.

Role of new generation implantable loop recorders in managing undiagnosed pediatric cardiac symptoms

Pediatric cardiac symptoms such as palpitations, syncope, or seizure-like episodes pose diagnostic challenges for general pediatricians. These symptoms, though often benign, may reveal underlying arrhythmias or inherited cardiac conditions (ICCs), affecting the quality of life and limiting activity participation. The purpose of this study is to determine the effectiveness and safety of implantable loop recorders (ILRs) in diagnosing and managing arrhythmias in pediatric patients. A retrospective cohort study conducted over an 8-year period from January 2016 to December 2023 in a single pediatric cardiology center. A cohort of 155 pediatric patients (median age 11.4 years) who underwent ILR implantation were selected based on symptoms such as palpitations, chest pain, or syncope, and those with previously recorded arrhythmias or high-risk ICCs. The primary outcomes were the diagnostic yield of ILRs for arrhythmias and subsequent changes in patient management. Diagnostic yield was defined as the detection of relevant arrhythmias, such as pauses of 3 s or longer, high-degree AV block, sinus node dysfunction, supraventricular tachycardia, ventricular tachycardia, or inappropriate sinus tachycardia. The median follow-up period was 2.3 years (845 days). Diagnostic arrhythmias were recorded in 60% of patients with symptom-activated transmissions and 80% of device-activated transmissions. Sinus pauses (37.5%) and VT (30%) were the most common arrhythmias detected. In patients with syncope (n = 76), 30% had relevant arrhythmias. In the palpitations group (n = 20), 35% had relevant arrhythmias. Approximately 80% of patients with ILR-diagnosed arrhythmias underwent targeted management, including medication changes and additional procedures. No significant complications were observed; minor complications occurred in 2.5% of patients.Conclusions: New generation ILRs are effective and safe for diagnosing and managing pediatric arrhythmias, providing significant reassurance to patients and families. Further studies are needed to evaluate the impact of ILRs on quality of life and sports participation in high-risk young patients.What is Known:• Pediatric Cardiac Symptoms: Symptoms like palpitations, syncope, and seizure-like episodes in pediatric patients pose significant diagnostic challenges.• Diagnostic Tools: Traditional diagnostic tools such as ECG, Holter monitors, and external loop recorders often have low diagnostic yields due to the sporadic nature of symptoms.• Implantable Loop Recorders (ILRs): ILRs have been shown to improve the diagnostic yield for arrhythmias in adults and provide long-term rhythm monitoring.What is New:• Effectiveness in Pediatrics: This study demonstrates that new generation ILRs significantly enhance the diagnostic yield for arrhythmias in pediatric patients with undiagnosed cardiac symptoms.• Safety and Efficacy: The study confirms that ILRs are both safe and effective in the pediatric population, with minimal complications and high diagnostic accuracy.• Targeted Management: Findings show that ILR-diagnosed arrhythmias lead to targeted management changes in approximately 80% of cases, including medication adjustments and additional procedures.• Long-term Monitoring: ILRs provide continuous long-term monitoring, offering reassurance to patients and families, and potentially improving quality of life and participation in activities for high-risk young patients.

Post-procedural inappropriate sinus tachycardia after cardioneural ablation for malignant swallow syncope.

Post-procedural inappropriate sinus tachycardia after cardioneural ablation for malignant swallow syncope.

Prevalence of cardiac ARRHYTHMIAs in patients recovering from COVID-19

Abstract Background The family of seven known human coronaviruses are known for their impact on the respiratory tract, not the heart. However, the most recent coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has marked tropism for the heart and can lead to myocarditis (inflammation of the heart), necrosis of its cells, mimicking of a heart attack, arrhythmias, and heart failure. These complications, which at times are the only features of coronavirus disease 2019 (COVID-19) clinical presentation, have occurred even in cases with mild symptoms and in people who did not experience any symptoms. Recent findings of heart involvement in young athletes, including sudden death, have raised concerns about the current limits of our knowledge and potentially high risk and occult prevalence of COVID-19 heart manifestations. Aim of the Work was to detect the prevalence of cardiac arrhythmias in patients recovering from COVID-19 and to find out if it is related to COVID infection. Patients and Methods This cross sectional study was to detect the prevalence of cardiac arrhythmias in patients recovered from COVID-19 and to find out its relation to COVID infection. It was carried out on one hundred patients who had been diagnosed as COVID-19 and came after recovery from one to six months Post COVID at Ain Shams University Hospitals .This study was carried out during a period of six months between November 2021 and May 2022. Results that among these 100 patients recovering from COVID-19, 17 % of them developed cardiac arrhythmias as follow; 7 (7%) were diagnosed as Inappropriate Sinus Tachycardia, 3 (3%) had PVCs arising from RVOT, 3 (3%) were diagnosed as PACs, 2 (2%) were diagnosed as Paroxysmal AF, 1 (1%) was diagnosed as SVT (AVRT) and 1 (1%) was diagnosed as 1st degree heart block. Conclusion we found that Inappropriate sinus tachycardia was the most prevalent Cardiac Arrhythmia in these patients recovering from COVID-19 (7%) while other arrhythmias had lower prevalence with RVOT PVCS found in 3 % of the studied group, PACs in 3%, Paroxysmal AF in 2%, SVT (AVRT) in 1% and 1st degree heart block in 1% of this studied population. Absolute Lymphopenia during the course of COVID-19 illness had an effect on the prevalence of Cardiac Arrhythmias in patients recovering from COVID-19. Correlation among these arrhythmias and symptoms of these patients was called Post COVID syndrome.

Intracardiac echocardiography guided anatomical ablation of the arcuate ridge for drug refractory inappropriate sinus tachycardia.

Inappropriate sinus tachycardia (IST) is a common condition with frequently not tolerated beta-blockers or ivabradine and a high rate of complication in ablation strategy; we describe an alternative anatomical approach of sinus node (SN) modulation. This retrospective study describes a case series of 6 patients from two centers diagnosed with symptomatic IST undergoing SN ablation. The mean age was 40.6 ± 13.9 years; five of the six patients were female, 100% of patients reported heart palpitations, and 66% reported dizziness, the average heart rate(HR) on a 24-h Holter was 93.2 ± 7.9 bpm. HR during the first stage of a stress test using a standard Bruce protocol was 150 ± 70 bpm, The average HR on 24-h Holter postablation was 75 ± 5.6 bpm, the sinus rate HR during stage 1 of a Bruce protocol exercise stress test was 120 ± 10 bpm. This is the first case series reporting the acute and long-term results of a novel anatomical approach for SN modulation to treat IST targeting the arcuate ridge(AR) under intracardiac echography(ICE) guidance. The novel anatomic ICE-guided catheter ablation approach aimed to identify the earliest activation at the AR with an extension of RF lesions towardits septal region seems effective and safe to modulate the SN in symptomatic patients with IST refractory to medical treatment.

Does dysautonomia contribute to inappropriate sinus tachycardia in patients with post-COVID-19 syndrome?

Abstract Funding Acknowledgements None. Introduction Post-COVID-19 syndrome (PCS) refers to a wide spectrum of health issues experienced by individuals who have previously had COVID-19, starting three months after acute COVID-19 and enduring for a minimum of two months. Approximately 20% of PCS patients encounter inappropriate sinus tachycardia (IST), defined as the mean 24-hour heart rate greater than 90 bpm. IST is often accompanied by symptoms including palpitations and breathlessness that hinder patients in their daily tasks. Previous research has suggested that dysautonomia, a dysfunction in the autonomic nervous system, might underlie most PCS symptoms. Yet, its role in the development of IST within the context of PCS has not been fully investigated. Purpose This retrospective study examines IST prevalence and cardiovascular symptoms in PCS patients. It also assesses cardiac autonomic function through analysing the time and frequency fluctuations between successive heart rates, termed heart rate variability, to investigate the role of dysautonomia in the development of IST in PCS. Methods Patients who continued to experience PCS symptoms 12 weeks after their initial SARS-CoV-2 infection were referred to a multidisciplinary PCS unit at our hospital. Using our electronic patient record system, we identified 685 eligible patients who underwent 24-hour Holter monitoring between March 2020 and February 2023. After excluding patients with various conditions that could affect heart rate, we performed a comparative sub-analysis on 524 patients, dividing them into two age- and gender-matched groups of IST (n=100) and non-IST (n=424). The ECG data extracted from the 24-hour Holter records of these patients were entered into the KUBIOS software for HRV analysis and assessment of sympathetic and parasympathetic activity which could indicate cardiac dysautonomia. Demographic data was analysed using basic descriptive statistics and a chi-square test between the two groups. The normality of each parameter was tested using the Shapiro-Wilk test. Using Mann-Whitney and unpaired t-tests, we statistically analysed the differences between the IST and non-IST groups on the GraphPad Prism software. Results The LF/HF ratio was significantly higher in the IST group (2.78 ± 1.89) compared to the non-IST group (2.15 ± 1.93, p<0.001). The sympathetic nervous system (SNS) index was significantly higher in the IST group (1.50 ± 0.77 versus -0.13 ±0.70, p<0.001), whilst the parasympathetic nervous system (PNS) index was significantly lower in the IST group (-1.75 ± 0.65 versus -0.16 ± 1.61, p<0.001). Conclusions In PCS patients with IST, cardiac dysautonomia leads to a shift in the cardiac sympathovagal balance towards PNS and subsequently increased SNS activity, with a more pronounced effect on the parasympathetic side. Addressing dysautonomia and promoting parasympathetic activity could thereby improve PCS diagnostic and treatment strategies to restore a balanced autonomic regulation of the heart.

A novel sinus node-sparing hybrid ablation approach for inappropriate sinus tachycardia

A novel sinus node-sparing hybrid ablation approach for inappropriate sinus tachycardia

Triglicerydes/high-density lipoprotein ratio as a risk factor of post-Covid-19 sinus tachycardia: A retrospective study.

Inappropriate sinus tachycardia (IST) is one of the manifestations of the post-COVID-19 syndrome (PCS), which pathogenesis remains largely unknown. This study aimed to identify potential risk factors for IST in individuals with PCS. The 1349 patients with PCS were included into the study. Clinical examination, 24H Holter ECG, 24H ambulatory blood pressure monitoring and biochemical tests were performed 12-16 weeks after the COVID-19 in all participants. IST was found in 69 (3.5%) individuals. In the clinical assessment IST patients were characterized by a higher age (p < 0.001) and lower prevalence of the diagnosed hypertension (p = 0.012), compared to remaining patients. Biochemical testing showed higher serum triglycerides (1.66 vs. 1.31 pmol/L, p = 0.007) and higher prevalence of a low high-density lipoprotein (HDL) cholesterol (24.6% vs. 15.2%, p = 0.035) in the IST group. Subsequently, the triglicerydes (TG)/HDL ratio, an indicator of insulin resistance, was significantly higher in the IST individuals (3.2 vs. 2.4, p = 0.005). 24H monitoring revealed a significantly higher minimum diastolic, maximum systolic and mean arterial blood pressure values in the IST group (p < 0.001 for all), suggesting a high prevalence of undiagnosed hypertension. A multivariate analysis confirmed the predictive value TG/HDL ratio >3 (OR 2.67, p < 0.001) as predictors of IST development. A receiver operating characteristic curve analysis of the relationship between the TG/HDL ratio and the IST risk showed that the predictive cut-off point for this parameter was 2.46 (area under the ROC curve = 0.600, p = 0.004). Based on these findings, one can conclude that insulin resistance seems to be a risk factor of IST, a common component of PCS.

How to establish a successful and sustainable surgical atrial fibrillation program: key considerations on the arrhythmia, training and treatment strategies.

Establishing a successful and sustaining atrial fibrillation (AF) program should be current standard of care in cardiac surgery by providing not only sinus rhythm restoration but improving survival significantly. Recognition of AF as a serious cardiac disease impacting a considerable number of patients in terms of stroke, heart failure development and mortality is key when implementing a protocol to identify patients suitable for surgical ablation and a treatment standard according to the underlying pathology. The ablation strategy resulting in the best potential rhythm outcome should be chosen, and the applied access should follow this decision in a way that the optimal lesion set can be executed completely. A thorough follow-up is required to confirm results or make necessary adjustments to the implemented treatment protocol. This should be done in close collaboration with other treatment specialists such as cardiologists, electrophysiologists, primary care physicians, or neurologists. This collaboration might also facilitate an expansion of the program towards stand-alone ablation, ventricular tachycardia ablation, and inappropriate sinus tachycardia ablation.

Extended Use of Ivabradine in Heart Failure with Preserved Ejection Fraction and Inappropriate Sinus Tachycardia

Ivabradine has been used for over a decade in managing chronic coronary syndromes and heart failure (HF) with reducedejection fraction (HFrEF). HF with preserved ejection fraction (HFpEF) accounts for 50% of the total HF cases carrying equalmortality and morbidity risk as HFrEF. Increased heart rate (HR) in such cases has been shown to be associated with poorclinical outcomes. Clinical conditions like inappropriate sinus tachycardia (IST) manifest with elevated HR without anyspecific triggers. Beta-blockers have been the preferred treatment of choice for both HFpEF and IST but are often ineffective orpresent with side effects due to their negative ionotropic effects. Ivabradine, through its inhibitory action on funny current(Ifc), reduces HR without altering the inotropic mechanism. Few case reports and small case series have documented itsextended use and efficacy in reducing HR in these cardiac conditions. In this article, we present two cases who needed HRcontrol, one with HFpEF and another case of IST syndrome. Ivabradine was successfully used in both these cases to controlthe elevated HR.

The Impact of Long COVID-19 on the Cardiovascular System.

Long coronavirus disease (COVID) is the development or persistence of symptoms after an acute SARS-CoV-2 (COVID-19) infection. Fewer patients are developing acute COVID-19 infections, but patients with long COVID continue to have alarming long-term sequelae. Many cardiac magnetic resonance imaging studies show significant changes in cardiac structure after a COVID-19 infection, suggestive of an increased burden of many cardiovascular diseases, notably myocarditis. The pathophysiology of COVID-19 requires viral binding to angiotensin-converting enzyme 2 protein receptors throughout the body, which are upregulated by inflammation. Consequently, the numerous preexisting conditions that worsen or prolong inflammation enhance this binding and have differing effects on patients based on their unique immune systems. These pathophysiological changes drive long COVID cardiac sequelae such as inappropriate sinus tachycardia, postural orthostatic tachycardia, and other types of orthostatic intolerance. Increased screening for long COVID and low-risk interventions such as exercise regimens could alleviate the suffering endured by patients with long COVID. Many studies such as the Researching COVID to Enhance Recovery Initiative (RECOVER) trials at the National Institutes of Health are exploring potential treatments for long COVID patients.

Surgery for Cardiac Arrhythmias: Past, Present, Future.

There is a rich history of surgery for cardiac arrhythmias, spanning from atrial fibrillation and Wolff-Parkinson-White syndrome to inappropriate sinus tachycardia and ventricular tachycardia. This review describes the history of these operations, their evolution over time, and the current state of practice. We devote considerable time to the discussion of atrial fibrillation, the most common cardiac arrhythmia addressed by surgeons. We discuss ablation of atrial fibrillation as a stand-alone operation and as a concomitant operation performed at the time of cardiac surgery. We also discuss the emergence of newer procedures to address atrial fibrillation in the past decade, such as the convergent procedure and totally thoracoscopic ablation, and their outcomes relative to historic approaches such as the Cox maze procedure.

Pericarditis prophylactic therapy after sinus node–sparing hybrid ablation for inappropriate sinus tachycardia/postural orthostatic sinus tachycardia

Pericarditis is the most common complication following hybrid sinus node-sparing ablation for inappropriate sinus tachycardia (IST)/postural orthostatic tachycardia syndrome (POTS). The study sought to evaluate the association of prophylaxis therapy on the risk of symptomatic pericarditis following hybrid IST/POTS ablation. All consecutive patients undergoing to hybrid ablation of symptomatic IST/POTS refractory or intolerant to drugs were retrospectively analyzed. Pharmacological prophylaxis therapy was based on acetylsalicylic acid and colchicine started on the day of the ablation and continued for at least 3 months. The primary endpoint was occurrence of symptomatic pericarditis. The secondary endpoint was occurrence of pericarditis-related complications, including the following: duration of pericarditis >3 months, hospitalization for pericarditis, postpericardiectomy pleuro-pericarditis, and pericardiectomy. A total of 220 patients undergone to hybrid IST/POTS ablation were included and 44 (20%) underwent prophylaxis therapy. Pericarditis occurred in 101 (45.9%) patients, with 97 (96%) in the first 5 days. At survival analysis, prophylaxis was associated with higher rate of freedom from pericarditis (81.9% vs 47.2%, log-rank P < .001). Pericarditis-related complications were low, occurring in 7 (3.2%) patients. There was no difference in pericarditis-related complications between the patients who underwent prophylaxis therapy and patients who did not. At Cox multivariate analysis, predictors of pericarditis were IST (vs POTS) (hazard ratio 0.61, 95% confidence interval0.39-0.99, P = .04) and prophylaxis therapy (hazard ratio 0.27, 95% confidence interval 0.13-0.55, P < .001). In a large cohort of patients undergoing hybrid ablation for IST/POTS, a prophylaxis therapy with acetylsalicylic acid and colchicine was associated with a lower rate of symptomatic pericarditis.

Cardiovascular autonomic dysfunction in post-COVID-19 syndrome: a major health-care burden.

Cardiovascular autonomic dysfunction (CVAD) is a malfunction of the cardiovascular system caused by deranged autonomic control of circulatory homeostasis. CVAD is an important component of post-COVID-19 syndrome, also termed long COVID, and might affect one-third of highly symptomatic patients with COVID-19. The effects of CVAD can be seen at both the whole-body level, with impairment of heart rate and blood pressure control, and in specific body regions, typically manifesting as microvascular dysfunction. Many severely affected patients with long COVID meet the diagnostic criteria for two common presentations of CVAD: postural orthostatic tachycardia syndrome and inappropriate sinus tachycardia. CVAD can also manifest as disorders associated with hypotension, such as orthostatic or postprandial hypotension, and recurrent reflex syncope. Advances in research, accelerated by the COVID-19 pandemic, have identified new potential pathophysiological mechanisms, diagnostic methods and therapeutic targets in CVAD. For clinicians who daily see patients with CVAD, knowledge of its symptomatology, detection and appropriate management is more important than ever. In this Review, we define CVAD and its major forms that are encountered in post-COVID-19 syndrome, describe possible CVAD aetiologies, and discuss how CVAD, as a component of post-COVID-19 syndrome, can be diagnosed and managed. Moreover, we outline directions for future research to discover more efficient ways to cope with this prevalent and long-lasting condition.

Autoimmunity and Biological Therapies in Cardiac Arrhythmias

Autoimmune (AI) diseases have a notable rise globally, affecting up to 9.4% of the global population. Cardiac involvement is not unusual in AI diseases, leading to arrhythmias through many pathophysiological mechanisms like myocardial inflammation, fibrosis, and autoantibodies targeting critical cardiac structures, leading to cardiac rhythm disorders. This review focuses on the role of autoantibodies in arrhythmias in diseases like sarcoidosis, lupus, rheumatoid arthritis, scleroderma, and others, highlighting new findings about autoantibodies against critical structural myocardial components. On the other hand, the review describes the AI association with conditions such as sinus bradycardia, atrioventricular blocks, inappropriate sinus tachycardia, atrial fibrillation, ventricular tachycardia, and sudden cardiac death, describing those processes. Emerging biomarkers indicative of inflammation, fibrosis, and autoimmunity that can predict arrhythmia risk are examined. The review also explores the field of managing cardiac arrhythmias with alternative cell therapy approaches that target gene substrate as a promising way to transfer, silence, and edit cellular disorders associated with arrhythmia generation that may help treat these conditions in the future.

Successful Three-Dimensional Mapping-Guided Sinus Node Modification for Drug-Refractory Inappropriate Sinus Tachycardia after Circumferential Pulmonary Vein Isolation.

Successful Three-Dimensional Mapping-Guided Sinus Node Modification for Drug-Refractory Inappropriate Sinus Tachycardia after Circumferential Pulmonary Vein Isolation.

A gain-of-function HCN4 mutant in the HCN domain is responsible for inappropriate sinus tachycardia in a Spanish family.

In a family with inappropriate sinus tachycardia (IST), we identified a mutation (p.V240M) of the hyperpolarization-activated cyclic nucleotide-gated type 4 (HCN4) channel, which contributes to the pacemaker current (If) in human sinoatrial node cells. Here, we clinically study fifteen family members and functionally analyze the p.V240M variant. Macroscopic (IHCN4) and single-channel currents were recorded using patch-clamp in cells expressing human native (WT) and/or p.V240M HCN4 channels. All p.V240M mutation carriers exhibited IST that was accompanied by cardiomyopathy in adults. IHCN4 generated by p.V240M channels either alone or in combination with WT was significantly greater than that generated by WT channels alone. The variant, which lies in the N-terminal HCN domain, increased the single-channel conductance and opening frequency and probability of HCN4 channels. Conversely, it did not modify the channel sensitivity for cAMP and ivabradine or the level of expression at the membrane. Treatment with ivabradine based on functional data reversed the IST and the cardiomyopathy of the carriers. In computer simulations, the p.V240M gain-of-function variant increases If and beating rate and thus explains the IST of the carriers. The results demonstrate the importance of the unique HCN domain in HCN4, which stabilizes the channels in the closed state.

Cardioneuroablation for reflex asystolic syncope: Mid-term safety, efficacy, and patient’s acceptance

BackgroundCardioneuroablation (CNA) is a promising therapy for reflex asystolic syncope; however, convincing data on the mid-term safety and efficacy of this procedure are lacking. ObjectiveThe purpose of this study was to assess the mid-term safety, efficacy, and patient acceptance of CNA. MethodsThis prospective observational single-center study included 115 consecutive patients (mean age 39 ± 13 years; 58% female) treated between 2016 and 2022 who completed at least 1-year follow-up. ResultsNo significant procedure-related acute complications occurred. During median follow-up of 28 months (range 12–75), 95 (83%) remained free from syncope. Of the 20 patients (17%) with syncope recurrence, syncope burden decreased from a mean 17 (median 6.5) to 3.75 (median 2.5) episodes (P = .015). In 9 of 10 patients, pacing system removal was possible. Repeated CNA was needed in 3 patients (3%), whereas pacemaker implantation was performed in 5 (4%). The most frequent mid-term complication of CNA was sinus rhythm acceleration (from 60 ± 14 bpm to 90 ± 16 bpm; P <.0001), which was symptomatic in 31 patients (27%); 8 patients (7%) required chronic beta-blocker and/or ivabradine. Sinus node modification was necessary in 1 patient. Other complaints included dyspnea, chronic chest pain, and decreased exercise capacity, which were mild and reported by 16 patients (14%). Patient acceptance of CNA was very high: 96% stated that it was worth undergoing the procedure. ConclusionsMid-term efficacy of CNA exceeds 80%, and acute complications are absent. The most frequent mid-term chronic complication is inappropriate sinus tachycardia, which in 7% required chronic treatment. The procedure is well accepted by patients.