Randomized Trial of Ivabradine in Patients With Hyperadrenergic Postural Orthostatic Tachycardia Syndrome

Ivabradine Approved and Other Uses in Clinical Practice: A Systematic Review

ABSTRACT

Heart rate (HR) stands as a prognostic indicator of cardiovascular disease and a modifiable risk factor in heart failure (HF). Medication intolerance can curtail the application of conventional HR-lowering β-blockers to the optimum target dose. Ivabradine (IVA), a specific negative-chronotropic agent, selectively inhibits I f current in pacemaker cells of the sinoatrial node without depressing myocardial contractility or comprising hemodynamics. This review summarized ivabradine's clinical labeled and off-label uses and mechanism of action focusing on the clinical outcomes. PubMed was searched up to January 2024 using the main keywords of IVA, coronary artery disease (CAD), HF, postural tachycardia syndrome (POTS), and tachyarrhythmia. To comprehensively review IVA's clinical indications, mechanisms, and therapeutic effects, all studies investigating treatment with IVA in humans were included, comprising different types of studies such as randomized controlled trials and longitudinal prospective observational studies. After screening, 141 studies were included in our review. A large number of reviewed articles were allocated to heart failure with reduced ejection fraction and CAD, suggesting IVA as an alternative to β-blockers in case of contraindications or intolerance. The beneficial effects of IVA as premedication for coronary computed tomography angiography, HR lowering in POTS, and inappropriate sinus tachycardia constituted most studies among off-label uses. The promising results have been reported on the efficacy of IVA in controlling HR, especially in patients with inappropriate sinus tachycardia or POTS. Owing to the unique mechanism of action, IVA has the potential to be used more frequently in future clinical practice.

Physiological effects of ivabradine in heart failure and beyond

Ivabradine is a pharmacologic agent that inhibits the funny current responsible for determining heart rate in the sinoatrial node. Ivabradine's clinical potential has been investigated in the context of heart failure since it is associated with reduced myocardial oxygen demand, enhanced diastolic filling, stroke volume, and coronary perfusion time; however, it is yet to demonstrate definitive mortality benefit. Alternative effects of ivabradine include modulation of the renin-angiotensin-aldosterone system, sympathetic activation, and endothelial function. Here, we review key clinical trials informing the clinical use of ivabradine and explore opportunities for leveraging its potential pleiotropic effects in other diseases, including treatment of hyperadrenergic states and mitigating complications of COVID-19 infection.

Navigating Complexity in Postural Orthostatic Tachycardia Syndrome

Postural Orthostatic Tachycardia Syndrome (POTS) affects up to 1% of the US population, predominantly women, and is characterized by a complex, elusive etiology and heterogeneous phenotypes. This review delves into the intricate physiology and etiology of POTS, decoding the roles of the sinoatrial node, the autonomic nervous system, fluid dynamics, and the interplay between the immune and endocrine systems. It further examines key contributing factors such as dysautonomia, thoracic hypovolemia, autonomic neuropathies, sympathetic denervation, autoimmune responses, and associations with conditions such as small-fiber neuropathy and mast cell activation syndrome. Given the numerous mysteries surrounding POTS, we also cautiously bring attention to sinoatrial node and myocardial function, particularly in how the heart responds to stress despite exhibiting a normal cardiac phenotype at rest. The potential of genomic research in elucidating the underlying mechanisms of POTS is emphasized, suggesting this as a valuable approach that is likely to improve our understanding of the genetic underpinnings of POTS. The review introduces a tentative classification system for the etiological factors in POTS, which seeks to capture the condition's diverse aspects by categorizing various etiological factors and acknowledging co-occurring conditions. This classification, while aiming to enhance understanding and optimize treatment targets, is presented as a preliminary model needing further study and refinement. This review underscores the ongoing need for research to unravel the complexities of POTS and to develop targeted therapies that can improve patient outcomes.

Long-Term POTS Outcomes Survey: Diagnosis, Therapy, and Clinical Outcomes

BACKGROUND

Limited data exist on long-term outcomes in individuals with postural orthostatic tachycardia syndrome (POTS). We designed an electronic questionnaire assessing various aspects of outcomes among patients diagnosed and treated in a single-center pediatric POTS clinical program.

METHODS AND RESULTS

The LT-POTS (Long Term POTS Outcomes Survey) included questions about quality of life, symptoms, therapies, education, employment, and social impact of disease. Patients age≤18 years at POTS diagnosis who were managed in the Children's Hospital of Philadelphia POTS Program were included. A total of 227 patients with POTS responded with sufficient data for interpretation. The mean age of respondents was 21.8±3.5 years. The median age of symptom onset was 13 (interquartile range 11-14) years, with mean 9.6±3.4 years symptom duration. Multiple cardiovascular, neurologic, and gastrointestinal symptoms were reported. Symptom prevalence and severity were worse for female patients, with 99% of patients reporting ongoing symptoms. Quality of life showed moderate function and limitation, with more severe limitations in energy/fatigue and general health. Nearly three quarters of patients had diagnostic delays, and over half were told that their symptoms were "in their head." Multiple medications were used and were felt to be effective, whereas fewer nonpharmacologic interventions demonstrated efficacy. Nearly 90% of patients required continued nonpharmacologic therapy to control symptoms.

CONCLUSIONS

POTS is a chronic disorder leading to significant disability with a range of multisystem problems. Although symptoms can be modifiable, it rarely spontaneously resolves. Improved understanding of POTS presentation and therapeutic approaches may inform provider education, improve diagnostic success, and help patients self-advocate for appropriate medical management approaches.

[Research progress in the application of ivabradine in children with cardiovascular diseases]

Ivabradine, as a specific If current inhibitor, has been widely used in the treatment of chronic heart failure in adults due to its ability to reduce heart rate without affecting myocardial contractility and blood pressure. It has also shown good effects in various types of tachyarrhythmias. However, the application of ivabradine in pediatric cardiovascular diseases still faces many limitations. This article reviews the current research progress on the use of ivabradine in treating pediatric cardiovascular diseases both domestically and internationally, aiming to provide guidance for pediatric cardiologists. Citation:Chinese Journal of Contemporary Pediatrics, 2024, 26(7): 782-788.

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.

Postural Tachycardia Syndrome and COVID-19: Focus on Ivabradine Therapy

In this article we discuss the association of postural orthostatic tachycardia syndrome (POTS) with coronavirus-19 (COVID-19), ivabradine's unique mechanism of action, and its use in POTS patients. We highlight the pathophysiology and common etiologies of POTS, including preceding viral infections, vaccines, trauma, surgeries, and other stressors. COVID-19, a viral illness, has been associated with POTS through a variety of mechanisms that are not yet well understood. The initial management strategy for POTS is largely nonpharmacological, focusing on increasing venous return to the heart through physical therapy or other exercise activities. Ivabradine is a selective inhibitor of the funny sodium channels within the sinoatrial node. This unique mechanism of action allows for the reduction of heart rate without any effect on the heart's ionotropic activity. With an increase in the number of POTS cases, especially during the COVID pandemic, the importance of utilizing new medications and management strategies for POTS becomes imperative. Though ivabradine is currently only approved for the management of patients with coronary artery disease and heart failure by the Food and Drug Administration (FDA), it has also proven to be effective at reducing symptoms among patients with refractory POTS, and thus, should be considered for the management of patients who do not respond to initial treatment strategies.

Cardiovascular dysautonomia in postacute sequelae of SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19) has led to a worldwide pandemic that continues to transform but will not go away. Cardiovascular dysautonomia in postacute sequelae of severe acute respiratory syndrome coronavirus 2 infection has led to persistent symptoms in a large number of patients. Here, we define the condition and its associated symptoms as well as potential mechanisms responsible. We provide a careful and complete overview of the topic addressing novel studies and a generalized approach to the management of individuals with this complex and potentially debilitating problem. We also discuss future research directions and the important knowledge gaps to be addressed in ongoing and planned studies.

Dysautonomia following Lyme disease: a key component of post-treatment Lyme disease syndrome?

Dysautonomia, or dysfunction of the autonomic nervous system (ANS), may occur following an infectious insult and can result in a variety of debilitating, widespread, and often poorly recognized symptoms. Dysautonomia is now widely accepted as a complication of COVID-19 and is an important component of Post-Acute Sequelae of COVID-19 (PASC or long COVID). PASC shares many overlapping clinical features with other infection-associated chronic illnesses including Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Post-Treatment Lyme Disease Syndrome (PTLDS), suggesting that they may share common underlying mechanisms including autonomic dysfunction. Despite the recognition of this complication of Lyme disease in the care of patients with PTLD, there has been a scarcity of research in this field and dysautonomia has not yet been established as a complication of Lyme disease in the medical literature. In this review, we discuss the evidence implicating Borrelia burgdorferi as a cause of dysautonomia and the related symptoms, propose potential pathogenic mechanisms given our knowledge of Lyme disease and mechanisms of PASC and ME/CFS, and discuss the diagnostic evaluation and treatments of dysautonomia. We also outline gaps in the literature and priorities for future research.

Noninvasive Vagus Nerve Stimulation in Postural Tachycardia Syndrome: A Randomized Clinical Trial

BACKGROUND

Low-level transcutaneous stimulation of the auricular branch of the vagus nerve at the tragus is antiarrhythmic and anti-inflammatory in animals and humans. Preliminary studies show that transcutaneous vagus nerve stimulation (tVNS) is beneficial in animal models of postural tachycardia syndrome (POTS).

OBJECTIVES

In this study the authors conducted a sham-controlled, double-blind, randomized clinical trial to examine the effect of tVNS on POTS over a 2-month period relative to sham stimulation.

METHODS

tVNS (20 Hz, 1 mA below discomfort threshold) was delivered using an ear clip attached to either the tragus (active; n = 12) or the ear lobe (sham; n = 14) for 1 hour daily over a 2-month period. Postural tachycardia was assessed during the baseline and 2-month visit. Heart rate variability based on 5-minute electrocardiogram, serum cytokines, and antiautonomic autoantibodies were measured at the respective time points.

RESULTS

Mean age was 34 ± 11 years (100% female; 81% Caucasian). Adherence to daily stimulation was 83% in the active arm and 86% in the sham arm (P > 0.05). Postural tachycardia was significantly less in the active arm compared with the sham arm at 2 months (mean postural increase in heart rate 17.6 ± 9.9 beats/min vs 31.7 ± 14.4 beats/min; P = 0.01). Antiadrenergic autoantibodies and inflammatory cytokines were lower in the active arm compared with the sham arm at 2 months (P < 0.05). Heart rate variability was better in the active arm. No device-related side effects were observed.

CONCLUSIONS

Our results support the emerging paradigm of noninvasive neuromodulation to treat POTS. Mechanistically, this effect appears to be related to reduction of antiautonomic autoantibodies and inflammatory cytokines, and improvement in autonomic tone. Further studies are warranted. (Autoimmune Basis for Postural Tachycardia Syndrome; NCT05043051).

Radiofrequency venous ablation for symptomatic relief in postural orthostatic tachycardia syndrome: a case series

Background

Hypovolemic postural orthostatic tachycardia syndrome (POTS) is thought to be caused by dysregulated circulating blood volume. Management is mainly limited to symptom-targeted lifestyle changes. Radiofrequency venous ablation (RFA) represents a minimally invasive method of increasing circulating blood volume. The following case series describes a novel application of RFA to successfully target POTS symptoms in patients demonstrating venous insufficiency. The use of RFA in alleviating POTS symptoms has not previously been reported.

Case summary

We describe four patients with either a well-established historical POTS diagnosis or dysautonomia symptoms refractory to both medical management and lifestyle modifications. They all demonstrated venous reflux on lower extremity venous ultrasound testing. Upon vascular surgery referral, all underwent great and small saphenous vein RFA. They each subsequently reported subjective improvement in their dysautonomia symptoms and quality-of-life. Two with symptom recurrence years later were found to have new-onset pelvic venous congestion and are being evaluated for pelvic venous insufficiency interventions.

Discussion

Lower extremity venous pooling can exacerbate dysautonomia symptoms in POTS patients. Patients refractory to conventional treatment strategies should undergo venous insufficiency workup, and if positive, should be referred for venous pooling intervention evaluation. The success of RFA at treating refractory POTS symptoms in these four patients with lower extremity venous reflux, including no surgical intervention and no adverse effects, are compelling grounds to further explore this therapy and to quantify and standardize symptom improvement assessment in a larger patient population. Future directions include a demonstration of quality-of-life improvement in randomized clinical trials.

Autonomic Manifestations of Long-COVID Syndrome

PURPOSE OF REVIEW

Long-COVID is a novel condition emerging from the COVID-19 pandemic. Long-COVID is characterized by symptoms commonly seen in autonomic disorders including fatigue, brain fog, light-headedness, and palpitations. This article will critically evaluate recent findings and studies on Long-COVID and its physiological autonomic manifestations.

RECENT FINDINGS

Studies have reported on the prevalence of different symptoms and autonomic disorders in Long-COVID cohorts. Autonomic nervous system function, including both the parasympathetic and sympathetic limbs, has been studied using different testing techniques in Long-COVID patients. While numerous mechanisms may contribute to Long-COVID autonomic pathophysiology, it is currently unclear which ones lead to a Long-COVID presentation. To date, studies have not tested treatment options for autonomic disorders in Long-COVID patients. Long-COVID is associated with autonomic abnormalities. There is a high prevalence of clinical autonomic disorders among Long-COVID patients, with limited knowledge of the underlying mechanisms and the effectiveness of treatment options.

Novel mechanism of the COVID-19 associated coagulopathy (CAC) and vascular thromboembolism

Previous studies from our laboratory revealed that SARS-CoV-2 spike protein (SP) administration to a genetically engineered model expressing the human angiotensin-converting enzyme 2; ACE2 receptor (i.e., hACE2 humanized mouse) mimicked the coronavirus disease-19 (COVID-19) pathology. In humans the cause of high morbidity, and mortality is due to 'cytokine-storm' led thromboembolism; however, the exact mechanisms of COVID-19 associated coagulopathy (CAC) have yet to be discovered. Current knowledge suggests that CAC is distinct from the standard coagulopathy, in that the intrinsic and extrinsic thrombin-dependent coagulation factors, and the pathway(s) that are common to coagulopathy, are not recruited by SARS-CoV-2. Findings from patients revealed that there is little change in their partial thromboplastin, or the prothrombin time coupled with a significant decline in platelets. Further, there appears to be an endothelial dysfunction during COVID-19 suggesting an interaction of the endothelia with immune cells including neutrophils. There are also reports that inflammatory NGAL is elevated during COVID-19. Furthermore, the levels of NPT are also increased indicating an increase in inflammatory M1 macrophage iNOS which sequesters BH4; an essential enzyme co-factor that acts as a potent antioxidant thus causing damage to endothelia. SARS-CoV-2 entry into the host cells is facilitated by a co-operative action between TMPRSS2 and the main ACE2 receptor. Interestingly, after infection ADAMTS13; a von Willebrand factor; VWF cleaving enzyme is found to be decreased. Based on these facts, we hypothesize that vascular thromboembolism is associated with serine and metalloproteinase, and in that context, we opine that inhibition of iNOS might help mitigate COVID-19 harmful effects. To test this hypothesis, we administered SP to the hACE2 mice that were subsequently treated with amino guanidine (AG; a potent inhibitor of glycoxidation, lipoxidation and oxidative vicious cycles). Our results revealed increase in TMPRSS2, and NGAL by SP but treatment with AG mitigated their levels. Similarly, levels of MMP-2, and -9 were increased; however, AG treatment normalized these levels. Our findings suggest that occurrence of CAC is influenced by TMPRSS2, ADAMTS13, NGAL and MMP- 2, and -9 factors, and an intervention with iNOS blocker helped mitigate the CAC condition in experimental settings.

Autonomic Dysfunction Related to Postacute SARS-CoV-2 Syndrome

Persistence of symptoms beyond the initial acute phase of coronavirus disease-2019 (COVID-19) is termed postacute SARS-CoV-2 (PASC) and includes neurologic, autonomic, pulmonary, cardiac, psychiatric, gastrointestinal, and functional impairment. PASC autonomic dysfunction can present with dizziness, tachycardia, sweating, headache, syncope, labile blood pressure, exercise intolerance, and "brain fog." A multidisciplinary team can help manage this complex syndrome with nonpharmacologic and pharmacologic interventions.

Postural Orthostatic Tachycardia Syndrome After COVID-19: A Systematic Review of Therapeutic Interventions

ABSTRACT

Postural orthostatic tachycardia syndrome (POTS) is a clinical syndrome of inappropriate increase in heart rate on standing that has been recently also associated with Coronavirus Disease 2019 (COVID-19) as part of the postacute sequelae of COVID-19 (PASC) or long-COVID. We herein aimed to systematically review reported cases of POTS after COVID-19 and determine the characteristics of the subjects, the diagnostic approach used, and the treatment strategies. We searched the literature according to the following criteria: (1) diagnosis of POTS according to standard definition; (2) timely association with a probable or definite diagnosis of COVID-19; and (3) a description of the individual subject(s). We identified 21 reports meeting criteria between March 2020 and September 2022, including 68 subjects (51 females and 17 males, 3:1 ratio) with a mean age of 34 ± 12 years, with reports deriving from the United States, Norway, Sweden, Israel, Ireland, United Kingdom, Singapore, and Japan. Most cases had mild COVID-19 symptoms. The most common POTS symptoms were palpitations, chest pain, lightheadedness, and debilitating fatigue. The diagnosis was established by means of head-up tilt table or active stand test. Nonpharmacologic treatments (fluids, sodium intake, and compression stockings) were virtually always used, but largely ineffective. Subjects received different treatments, the most common being beta-adrenergic blockers (ie, propranolol), mineral corticosteroids (ie, fludrocortisone), midodrine, and ivabradine. Symptoms tended to improve over time, but most patients remained symptomatic for several months. In conclusion, POTS after COVID-19 is a clinical condition affecting young individuals, and disproportionately young women, occurring as part of PASC-long-COVID, often debilitating, which can be easily diagnosed with a thorough clinical assessment and measuring changes in orthostatic heart rate and blood pressure. POTS after COVID-19 seems to be poorly responsive to nonpharmacological treatments but with symptoms improving with pharmacological interventions. Given the limited data available, additional research is urgently needed with respect to its epidemiology, pathophysiology, and treatments.

Predicting Therapeutic Efficacy of Pharmacological Treatments in Children with Postural Orthostatic Tachycardia Syndrome: A Mini-Review

Postural orthostatic tachycardia syndrome (POTS) is common in children, with an excessive increment in heart rate when moving from the supine to upright position. It has significant negative impacts on the daily life of pediatric patients. The pathogenesis of POTS includes peripheral vascular dysfunction, central hypovolemia, abnormal autonomic function, a high-adrenergic state, impaired skeletal-muscle pump function, the abnormal release of vasoactive factors, and autoimmune abnormalities. Therefore, the empirical use of pharmacological treatments has limited therapeutic efficacy due to the diversity of its mechanisms. A crucial aspect of managing POTS is the selection of appropriate treatment targeting the specific pathogenesis. This review summarizes the commonly used pharmacological interventions, with a focus on their predictive indicators for treatment response. Factors such as heart rate variability, plasma biomarkers, and cardiac-function parameters are discussed as potential predictors of therapeutic efficacy, enabling the implementation of individualized treatment to improve therapeutic effectiveness. This review consolidates the current knowledge on POTS, encompassing its clinical characteristics, epidemiological patterns, underlying pathogenic mechanisms, and predictive indicators for treatment response. Further research is warranted to enhance the understanding of POTS and facilitate the development of more effective therapeutic approaches for this challenging syndrome.

COVID-19-Induced Postural Orthostatic Tachycardia Syndrome and Dysautonomia

Postural orthostatic tachycardia syndrome (POTS) is a disorder characterized by orthostatic intolerance and, by definition, includes clinical symptoms of lightheadedness, palpitations, and tremulousness among others. It is considered a relatively rare condition that affects approximately 0.2% of the general population, and it is estimated that between 500,000 to 1,000,000 individuals in the United States have the condition and recently has been linked to post-infectious (viral) etiologies. We present a case of a 53-year-old woman who was diagnosed with POTS following extensive autoimmune workup, who was also status post-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The post-coronavirus disease 2019 (COVID-19) cardiovascular autonomic dysfunction can affect global circulatory control, which describes increased heart rate even at resting states, and local circulatory disorders, such as coronary microvascular disease leading to vasospasm, as described by the patient's chest pain, and venous retention leading to pooling and reduced venous return after standing. Along with tachycardia with orthostatic intolerance, other symptoms can also accompany the syndrome. In the majority of patients, intravascular volume is reduced, leading to decreased venous return to the heart and causing reflex tachycardia and orthostatic intolerance. Management varies from lifestyle modifications to pharmacologic therapy, to which patients generally show a good response. POTS should be a differential on the cards, especially in patients post-COVID-19 infection, as these symptoms can be misdiagnosed as having psychological etiologies.

Sympathetic Modulation in Cardiac Arrhythmias: Where We Stand and Where We Go

The nuance of autonomic cardiac control has been studied for more than 400 years, yet little is understood. This review aimed to provide a comprehensive overview of the current understanding, clinical implications, and ongoing studies of cardiac sympathetic modulation and its anti-ventricular arrhythmias' therapeutic potential. Molecular-level studies and clinical studies were reviewed to elucidate the gaps in knowledge and the possible future directions for these strategies to be translated into the clinical setting. Imbalanced sympathoexcitation and parasympathetic withdrawal destabilize cardiac electrophysiology and confer the development of ventricular arrhythmias. Therefore, the current strategy for rebalancing the autonomic system includes attenuating sympathoexcitation and increasing vagal tone. Multilevel targets of the cardiac neuraxis exist, and some have emerged as promising antiarrhythmic strategies. These interventions include pharmacological blockade, permanent cardiac sympathetic denervation, temporal cardiac sympathetic denervation, etc. The gold standard approach, however, has not been known. Although neuromodulatory strategies have been shown to be highly effective in several acute animal studies with very promising results, the individual and interspecies variation between human autonomic systems limits the progress in this young field. There is, however, still much room to refine the current neuromodulation therapy to meet the unmet need for life-threatening ventricular arrhythmias.

Choices and Challenges With Drug Therapy in Postural Orthostatic Tachycardia Syndrome: A Systematic Review

The literature on pharmacologic treatments for postural orthostatic tachycardia syndrome (POTS) is inconsistent and unstandardized. Therefore, we aimed to evaluate choices in pharmacologic treatment options for POTS and the challenges encountered in the studies. We searched numerous databases like PubMed, Scopus, Embase, Web of Science, and Google Scholar for literature published before April 8, 2023. The search was done to retrieve potential peer-reviewed articles that explored drug therapy in POTS. Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines were used to conduct the systematic review. Of the 421 potential articles assessed, 17 met the inclusion criteria. Results demonstrated that pharmacologic treatment options for POTS were effective in reducing symptoms of POTS, but most of the studies were underpowered. Several were terminated due to various reasons. Midodrine ivabradine, bisoprolol, fludrocortisone, droxidopa, desmopressin, propranolol, modafinil, methylphenidate, and melatonin have been studied with positive impact but sample sizes that were low in the range of 10-50 subjects. Therefore, we concluded the treatment options effectively improve symptoms of POTS and increase orthostatic tolerance, but more evidence is needed as most studies had a low sample size and thus are underpowered.

A Review of Neurological Symptoms in Long COVID and Clinical Management

Long COVID is a clinical diagnosis generally referring to the persistence or development of new symptoms, affecting multiple organ systems after SARS-CoV-2 COVID-19 infection. Long COVID is thought to affect ∼20% of people after infection, including all age ranges and severity of infection. Fatigue, postexertional malaise, and respiratory and cardiac symptoms are commonly described. Neurological symptoms such as cognitive changes, sensory disturbances, headaches, and dysautonomia are common as well. The underlying pathophysiology remains unclear but immune dysregulation, autoimmunity, persistent viral reservoirs, and microvascular dysfunction have been implicated. As there are no tests at this time to diagnose long COVID, work-up should be focused on assessing reversible or treatable causes of symptoms. Furthermore, no treatments for long COVID currently exist, and management remains focused on a multimodal approach and symptom management, with many people showing improvement in symptoms over time.

Phenotyping autonomic neuropathy using principal component analysis

To identify autonomic neuropathy (AN) phenotypes, we used principal component analysis on data from participants (N = 209) who underwent standardized autonomic testing including quantitative sudomotor axon reflex testing, and heart rate and blood pressure at rest and during tilt, Valsalva, and standardized deep breathing. The analysis identified seven clusters: 1) normal, 2) hyperadrenergic features without AN, 3) mild AN with hyperadrenergic features, 4) moderate AN, 5) mild AN with hypoadrenergic features, 6) borderline AN with hypoadrenergic features, 7) mild balanced deficits across parasympathetic, sympathetic and sudomotor domains. These findings demonstrate a complex relationship between adrenergic and other aspects of autonomic function.

COVID-19 Induced Postural Orthostatic Tachycardia Syndrome (POTS): A Review

POTS (Postural Orthostatic Tachycardia Syndrome) is a multisystem disorder characterized by the abnormal autonomic response to an upright posture, causing orthostatic intolerance and excessive tachycardia without hypotension. Recent reports suggest that a significant percentage of COVID-19 survivors develop POTS within 6 to 8 months of infection. Prominent symptoms of POTS include fatigue, orthostatic intolerance, tachycardia, and cognitive impairment. The exact mechanisms of post-COVID-19 POTS are unclear. Still, different hypotheses have been given, including autoantibody production against autonomic nerve fibers, direct toxic effects of SARS-CoV-2, or sympathetic nervous system stimulation secondary to infection. Physicians should have a high suspicion of POTS in COVID-19 survival when presented with symptoms of autonomic dysfunction and should conduct diagnostic tests like the Tilt table and others to confirm it. The management of COVID-19-related POTS requires a comprehensive approach. Most patients respond to initial non-pharmacological options, but when the symptoms become more severe and they do not respond to the non-pharmacological approach, pharmacological options are considered. We have limited understanding and knowledge of post-COVID-19 POTS, and further research is warranted to improve our understanding and formulate a better management plan.

Postural orthostatic tachycardia syndrome: New concepts in pathophysiology and management

Postural orthostatic tachycardia syndrome (POTS) is a common and therapeutically challenging condition affecting numerous people worldwide. Recent studies have begun to shed light on the pathophysiology of this disorder. At the same time, both non-pharmacologic and pharmacologic therapies have emerged that offer additional treatment options for those afflicted with this condition. This paper reviews new concepts in both the pathophysiology and management of POTS.

Self-reported symptom burden in postural orthostatic tachycardia syndrome (POTS): A narrative review of observational and interventional studies

BACKGROUND AND OBJECTIVE

Postural Orthostatic Tachycardia Syndrome (POTS) is a chronic health condition affecting mostly women of childbearing age, and significantly impacting their health and quality of life. It is currently poorly understood with no approved licensed treatments. The aim of this systematic review was to contextualize the symptom burden of POTS, and review factors associated with this burden that may guide future treatments. The specific questions were (1) How does symptom burden in POTS compare to the burden in other long term conditions (LTCs), (2) Which factors are associated with POTS symptom burden, and (3) Which interventions show promise in reducing symptom burden in POTS.

DATABASES AND DATA TREATMENT

Electronic databases (CENTRAL, MEDLINE, EMBASE, CINAHL, PsycINFO, Web of Science, APA PsycArticles, OpenGrey) were searched from inception to January 2022 for observational studies reporting on the association between any biological, psychological or social factors and symptom burden, and randomized controlled trials reporting on interventions for symptom burden in adults with POTS. Two reviewers independently conducted eligibility screening, data extraction and quality assessment. A narrative synthesis was undertaken.

RESULTS/CONCLUSION

5159 entries were screened for eligibility. Twenty-nine studies were included (1372 participants with POTS of a total sample size of 2314, 17 High-, 12 Medium-quality), seventeen were observational and twelve were randomized controlled experimental and intervention trials. Overall methodological quality of the evidence was medium-high but heterogeneity was high and sample sizes modest, allowing moderately robust conclusions. Orthostatic symptom burden was higher in POTS than other LTCs. Serum activity against adrenergic α1 receptors, physical functioning, depression, catastrophizing, prolonged cognitive stress testing and anxiety were significantly associated with symptom burden in medium-high quality studies. Preliminary medium-high quality evidence from predominantly proof-of-concept (n = 11) studies and one 3-month 2 × 2 factorial design trial suggest that compression garments, propranolol, pyridostigmine, desmopressin, and bisoprolol may hold promise in reducing symptom burden. Directions for future research include investigating associated factors over time, the development of complex interventions which address both biological and psychosocial factors associated with symptom burden, and effectiveness trials of these interventions.

SIGNIFICANCE

POTS symptom burden is high, particularly in relation to orthostatic intolerance when compared to other long-term conditions (LTCs). Despite this burden, there are no effectiveness randomized controlled trials of treatment to reduce symptoms in POTS. This review provides a starting point to understanding researched biological and psychosocial factors associated with this burden. There was however inconsistency in the measurement of symptom burden, lowering the confidence of cross-study inferences. A coherent definition of POTS symptom range, severity and impact along with a validated and reliable POTS-specific instrument is currently lacking. A standardized questionnaire to assess POTS symptom burden as a core outcome measure will help clarify future research and clinical practice.

Noteworthy sequelae after COVID-19 pneumonia in a patient with heart failure due to cardiomyopathy

Coronavirus disease 2019 (COVID-19) is endemic worldwide. Cardiovascular disease, particularly myocarditis, is one of the most common comorbidities in patients with COVID-19. However, heart failure due to COVID-19-triggered cardiomyopathy is not well understood. Additionally, "pseudo" heart failure symptoms have been reported in patients with a compensated condition, in which the heart works well enough that symptoms are unnoticeable or very easy to manage. Here, we report a case of heart failure due to cardiomyopathy in a patient with COVID-19 and postural orthostatic tachycardia syndrome after heart failure treatment. Learning objective. Postural orthostatic tachycardia syndrome (POTS) symptoms after coronavirus disease 2019 may be mistaken for heart failure symptoms; thus, it is essential to suspect POTS when symptoms such as shortness of breath and palpitations are noted upon standing, along with the relevant physical findings.

Postural orthostatic tachycardia syndrome as a sequela of COVID-19

Postural orthostatic tachycardia syndrome (POTS) is a complex multisystem disorder characterized by orthostatic intolerance and tachycardia and may be triggered by viral infection. Recent reports indicate that 2%-14% of coronavirus disease 2019 (COVID-19) survivors develop POTS and 9%-61% experience POTS-like symptoms, such as tachycardia, orthostatic intolerance, fatigue, and cognitive impairment within 6-8 months of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Pathophysiological mechanisms of post-COVID-19 POTS are not well understood. Current hypotheses include autoimmunity related to SARS-CoV-2 infection, autonomic dysfunction, direct toxic injury by SARS-CoV-2 to the autonomic nervous system, and invasion of the central nervous system by SARS-CoV-2. Practitioners should actively assess POTS in patients with post-acute COVID-19 syndrome symptoms. Given that the symptoms of post-COVID-19 POTS are predominantly chronic orthostatic tachycardia, lifestyle modifications in combination with the use of heart rate-lowering medications along with other pharmacotherapies should be considered. For example, ivabradine or β-blockers in combination with compression stockings and increasing salt and fluid intake has shown potential. Treatment teams should be multidisciplinary, including physicians of various specialties, nurses, psychologists, and physiotherapists. Additionally, more resources to adequately care for this patient population are urgently needed given the increased demand for autonomic specialists and clinics since the start of the COVID-19 pandemic. Considering our limited understanding of post-COVID-19 POTS, further research on topics such as its natural history, pathophysiological mechanisms, and ideal treatment is warranted. This review evaluates the current literature available on the associations between COVID-19 and POTS, possible mechanisms, patient assessment, treatments, and future directions to improving our understanding of post-COVID-19 POTS.

Sinus Tachycardia: a Multidisciplinary Expert Focused Review

Sinus tachycardia (ST) is ubiquitous, but its presence outside of normal physiological triggers in otherwise healthy individuals remains a commonly encountered phenomenon in medical practice. In many cases, ST can be readily explained by a current medical condition that precipitates an increase in the sinus rate, but ST at rest without physiological triggers may also represent a spectrum of normal. In other cases, ST may not have an easily explainable cause but may represent serious underlying pathology and can be associated with intolerable symptoms. The classification of ST, consideration of possible etiologies, as well as the decisions of when and how to intervene can be difficult. ST can be classified as secondary to a specific, usually treatable, medical condition (eg, pulmonary embolism, anemia, infection, or hyperthyroidism) or be related to several incompletely defined conditions (eg, inappropriate ST, postural tachycardia syndrome, mast cell disorder, or post-COVID syndrome). While cardiologists and cardiac electrophysiologists often evaluate patients with symptoms associated with persistent or paroxysmal ST, an optimal approach remains uncertain. Due to the many possible conditions associated with ST, and an overlap in medical specialists who see these patients, the inclusion of experts in different fields is essential for a more comprehensive understanding. This article is unique in that it was composed by international experts in Neurology, Psychology, Autonomic Medicine, Allergy and Immunology, Exercise Physiology, Pulmonology and Critical Care Medicine, Endocrinology, Cardiology, and Cardiac Electrophysiology in the hope that it will facilitate a more complete understanding and thereby result in the better care of patients with ST.

Pediatric Postural Orthostatic Tachycardia Syndrome: Where We Stand

Postural orthostatic tachycardia syndrome (POTS), first described in 1992, remains an enigmatic, yet severely and variably debilitating, disorder. The pathophysiology of this syndrome is still not understood, and there remains no biomarker indicating the presence of POTS. Although research interest has increased in recent years, there are relatively fewer clinical and research studies addressing POTS in children and adolescents compared with adults. Yet, adolescence is when a large number of cases of POTS begin, even among adult patients who are subsequently studied. This article summarizes reported research in POTS, specifically in pediatric patients, including discussion of aspects of diagnostic criteria, risk factors and outcomes, neurohormonal and hemodynamic abnormalities, clinical assessment, and treatment. The goals of this review are increased recognition and acknowledgment of POTS among pediatric and adolescent providers, as well as to provide an understanding of reported abnormalities of homeostasis, such that symptomatic patients will be able to be recognized and appropriately managed, enabling them to return to their activities of daily living.

Postural Orthostatic Tachycardia Syndrome as a Manifestation of Post-COVID-19 Syndrome

The pandemic of coronavirus infection, the complex and insufficiently studied mechanisms of which cause disorders in the functions of many organs and systems of the body, has led to the emergence of new problems that are far from being resolved. Researchers note the difficulty in predicting the course of the disease and outcome due to the detection of many symptoms that arose at the height of the disease and persisted for 3-6 months after recovery. The term "post-COVID-19syndrome" has appeared, reflecting the condition of a patient who has undergone COVID-19, with a negative PCR test, and with symptoms lasting more than 12 weeks from the onset of the disease, which cannot be explained by an alternative diagnosis. Postural orthostatic tachycardia as a manifestation of the post-COVID-19syndrome has been described in young women who have undergone coronavirus infection of varying severity. In the case of the development of the syndrome of postural orthostatic tachycardia, the quality of life deteriorates, and the ability to work of patients is limited. There is no evidence base for drug therapy of postural tachycardia syndrome, in most cases empirical drug and non-drug methods of treatment are used.

A Scoping Review of Pharmacological Management of Postacute Sequelae of Severe Acute Respiratory Syndrome Coronavirus 2 Infection in 2021

BACKGROUND

Postacute sequelae of severe acute respiratory syndrome coronavirus 2 infection (PASC), or long-COVID, are signs and symptoms that persist after the acute phase of Coronavirus disease 2019 infection has passed. PASC is newly recognized, and research is ongoing to answer questions about pathology, symptoms, diagnosis, and optimal treatment.

AREAS OF UNCERTAINTY

Use of pharmacologic treatment for symptoms of PASC is currently evolving. This scoping review aims to assess medical literature for any evidence supporting or refuting use of any medications to specifically treat PASC.

DATA SOURCES

PubMed, EMBASE, Web of Science, and gray literature sources were searched for any study of medication use for PASC. Studies were included if they described medication use in patients with PASC. There were no exclusion criteria based on study type or if results were reported. Studies were divided into completed works and ongoing research.

RESULTS

Fifty-two records were included in final analysis from an initial 3524 records found, including 2 randomized controlled trials, 7 prospective, open-label or observational studies, 14 case reports or case series, 1 survey, 1 correspondence, 1 retrospective analysis, and 26 studies in progress. Seven of the 26 completed works investigate ivabradine or beta-blockers, whereas 7 investigate local or systemic corticosteroids. Three investigate multi-ingredient nutritional supplements. The other 9 completed works as well as the 26 studies in progress investigate a wide variety of other treatments including drugs in development, drugs used for other conditions, herbals, supplements, and vitamins.

CONCLUSIONS

There is limited, but evolving, literature on medication treatment for PASC. Providers who opt to use pharmacologic therapy for PASC need to be vigilant in their knowledge of these evolving data.

May-Thurner syndrome in patients with postural orthostatic tachycardia syndrome and Ehlers-Danlos syndrome: a case series

Background

Postural orthostatic tachycardia syndrome (POTS), Ehlers-Danlos syndrome (EDS), and May-Thurner syndrome (MTS) are three syndromes that are often misdiagnosed or underdiagnosed. The true prevalence of these syndromes may be higher than currently reported. The following case series is the first to report a three-way association between POTS, EDS, and MTS.

Case summary

We describe three patients with concomitant POTS, EDS, and MTS. Although abdominopelvic vasculature evaluation can be difficult via conventional imaging techniques, we present the use of novel dynamic contrast-enhanced magnetic resonance angiography with Differential Subsampling with Cartesian Ordering (DISCO) and four-dimensional flow magnetic resonance imaging to aid vasculature evaluation and the diagnosis of MTS. Two patients underwent left common iliac vein stenting to treat MTS, experiencing significant improvement in their POTS symptoms and quality of life.

Discussion

Ehlers-Danlos syndrome, POTS, and MTS may interact synergistically to exacerbate symptoms. Patients with EDS should be evaluated for possible POTS and pelvic venous complications. Left common iliac vein stenting for MTS can mitigate POTS symptoms by decreasing lower extremity venous pooling and should be considered in this patient population. Further research is needed to understand the exact mechanism and intricacies of this syndrome triad.

Ivabradine in the management of COVID-19-related cardiovascular complications: A perspective

Abstract:

Besides acute respiratory distress syndrome, acute cardiac injury is a major complication in severe coronavirus disease 2019 (COVID-19) and associates with a poor clinical outcome. Acute cardiac injury with COVID-19 can be of various etiologies, including myocardial ischemia or infarction and myocarditis, and may compromise cardiac function, resulting in acute heart failure or cardiogenic shock. Systemic inflammatory response increases heart rate (HR), which disrupts the myocardial oxygen supply/demand balance and worsens cardiac energy efficiency, thus further deteriorating the cardiac performance of the injured myocardium. In fact, the combination of elevated resting HR and markers of inflammation synergistically predicts adverse cardiovascular prognosis. Thus, targeted HR reduction may potentially be of benefit in cardiovascular pathologies associated with COVID-19. Ivabradine is a drug that selectively reduces HR via If current inhibition in the sinoatrial node without a negative effect on inotropy. Besides selective HR reduction, ivabradine was found to exert various beneficial pleiotropic effects, either HR-dependent or HR-independent, including anti-inflammatory, anti-atherosclerotic, anti-oxidant and antiproliferative actions and the attenuation of endothelial dysfunction and neurohumoral activation. Cardioprotection by ivabradine has already been indicated in cardiovascular pathologies that are prevalent with COVID-19, including myocarditis, acute coronary syndrome, cardiogenic shock or cardiac dysautonomia. Here, we suggest that ivabradine may be beneficial in the management of COVID-19-related cardiovascular complications.

Editor-in-Chief's Top Picks From 2021

Each week, I record audio summaries for every paper in JACC, as well as an issue summary. This process has become a true labor of love due to the time they require, but I am motivated by the sheer number of listeners (16M+), and it has allowed me to familiarize myself with every paper that we publish. Thus, I have selected the top 100 papers (both Original Investigations and Review Articles) from distinct specialties each year. In addition to my personal choices, I have included papers that have been the most accessed or downloaded on our websites, as well as those selected by the JACC Editorial Board members. In order to present the full breadth of this important research in a consumable fashion, we will present these abstracts in this issue of JACC, as well as their Central Illustrations and podcasts. The highlights comprise the following sections: Artificial Intelligence & Machine Learning (NEW section), Basic & Translational Research, Biomarkers (NEW section), Cardiac Failure & Myocarditis, Cardiomyopathies & Genetics, Cardio-Oncology, Cardiovascular Disease in Women, Coronary Disease & Interventions, Congenital Heart Disease, Coronavirus, Hypertension, Imaging, Metabolic & Lipid Disorders, Neurovascular Disease & Dementia, Promoting Health & Prevention, Rhythm Disorders & Thromboembolism, Vascular Medicine, and Valvular Heart Disease.^1-100.

Observational case series of postural tachycardia syndrome (PoTS) in post-COVID-19 patients

There is emerging evidence that a proportion of patients who develop long (post)-COVID-19 have abnormalities in the regulation of their autonomic nervous system manifesting as postural tachycardia syndrome (PoTS). We report a series of 14 patients who developed symptoms and signs compatible with PoTS following clinically diagnosed COVID-19 infection. Their symptoms and clinical findings were consistent with those of patients with non-COVID-related PoTS. The authors recommend an active stand test for patients who present after COVID-19 infection with cardiovascular symptoms including chest pain, palpitations, lightheadedness and breathlessness that are worse with the upright posture. They further recommend training of clinicians and investment in health services to provide for the anticipated significant increase in patients presenting with PoTS and other forms of autonomic dysfunction due to the COVID-19 pandemic.

Post-COVID-19 Tachycardia Syndrome: A Distinct Phenotype of Post-Acute COVID-19 Syndrome

In this paper we highlight the presence of tachycardia in post-acute COVID-19 syndrome by introducing a new label for this phenomenon-post-COVID-19 tachycardia syndrome-and argue that this constitutes a phenotype or sub-syndrome in post-acute COVID-19 syndrome. We also discuss epidemiology, putative mechanisms, treatment options, and future research directions in this novel clinical syndrome.

Atrial Tachycardia Masquerading As Inappropriate Sinus Tachycardia (IST) After COVID-19 Infection: A Matter of Concern?

COVID-19 Infection has wrecked havoc all over the world; the spectrum of this disease ranges from asymptomatic mild cases to severe cases such as acute respiratory distress syndrome (ARDS). Not only the acute infection but post COVID sequelae are also a cause of concern. Post-COVID states or Long COVID are the sequences of complications following the active infection. As post COVID sequelae are unpredictable it is absolutely the need of the hour to educate physicians and make them aware of all possibilities. We report one such case of a post COVID recovered young lady, who presented with drug-refractory recurrent palpitations. She was initially suspected to have inappropriate sinus tachycardia. But electrophysiological study confirmed the diagnosis of atrial tachycardia which was successfully ablated. The patient now has completed six months of follow-up and is off any medication.

Improvement of hyperadrenergic postural orthostatic tachycardia syndrome (POTS) with methylated B vitamins in the setting of a heterozygous COMT Val158Met polymorphism

A middle-aged woman was diagnosed with postural orthostatic tachycardia syndrome based on her clinical symptoms, elevated norepinephrine levels and positive tilt-table test. The patient was refractory to conventional treatment and improved only after she was treated with methylated B vitamins for her heterozygous catechol-O-methyltransferase Val158Met polymorphism.

Clinical and Laboratory Improvement in Hyperadrenergic Postural Orthostatic Tachycardia Syndrome (POTS) after COVID-19 Infection

A 32-year-old woman with a history of symptomatic supraventricular tachycardia, inappropriate sinus tachycardia, and hyperadrenergic POTS was treated with ivabradine and metoprolol. She then presented with bradycardia and Mobitz II second-degree AV block on event monitoring six weeks after COVID-19 infection. Her post-viral workup revealed normalization of catecholamine levels and significant symptomatic improvement in heart rate. To the authors' knowledge, this is the first reported case of improvement in POTS after COVID-19 infection. As our understanding of COVID-19 continues to improve, it will be vital to better understand the impact of COVID-19 dysautonomia on cardiac patients.

Long covid-mechanisms, risk factors, and management

Since its emergence in Wuhan, China, covid-19 has spread and had a profound effect on the lives and health of people around the globe. As of 4 July 2021, more than 183 million confirmed cases of covid-19 had been recorded worldwide, and 3.97 million deaths. Recent evidence has shown that a range of persistent symptoms can remain long after the acute SARS-CoV-2 infection, and this condition is now coined long covid by recognized research institutes. Studies have shown that long covid can affect the whole spectrum of people with covid-19, from those with very mild acute disease to the most severe forms. Like acute covid-19, long covid can involve multiple organs and can affect many systems including, but not limited to, the respiratory, cardiovascular, neurological, gastrointestinal, and musculoskeletal systems. The symptoms of long covid include fatigue, dyspnea, cardiac abnormalities, cognitive impairment, sleep disturbances, symptoms of post-traumatic stress disorder, muscle pain, concentration problems, and headache. This review summarizes studies of the long term effects of covid-19 in hospitalized and non-hospitalized patients and describes the persistent symptoms they endure. Risk factors for acute covid-19 and long covid and possible therapeutic options are also discussed.

COVID-19-induced postural orthostatic tachycardia syndrome treated with ivabradine

A 22-year-old woman was referred with exertional dyspnoea and chest tightness 3 weeks following a diagnosis of COVID-19. Evaluation revealed a resting sinus tachycardia and criteria for postural orthostatic tachycardia syndrome were met. After non-pharmacological interventions failed to yield symptomatic improvement, ivabradine was commenced. This intervention was followed by a substantial improvement in the patient’s exercise tolerance and energy levels and an objective reduction in supine and standing heart rate.

A practical approach to peripheral autonomic neuropathies

PURPOSE OF THE REVIEW

The review focuses on the practical evaluation and management of patients with autonomic neuropathies.

RECENT FINDINGS

Autonomic neuropathies are complex disorders and result in diverse clinical manifestations that affect the cardiovascular, gastrointestinal, urogenital, and sudomotor systems. The autonomic medical history is key when seeing a patient with suspected autonomic neuropathy. The history guides the clinical evaluation, laboratory testing, and autonomic testing in patients with autonomic neuropathies. The treatment of autonomic neuropathies is based on the combination of disease-modifying therapies, symptomatic pharmacologic therapies, and nonpharmacological management. Response to treatment can be assessed with quantitative autonomic biomarkers.

SUMMARY

Treatment of autonomic neuropathies should be individualized, guided by disease state, medications' mechanism of action and adverse event profile as well as cost. Genetic discoveries and pathologic understanding lead to the development of disease-modifying therapies as seen in familial amyloid polyneuropathy.

Post-COVID Syndrome and Tachycardia: Theoretical Base and Treatment Experience

The coronavirus pandemic showed not only an increase in levels of excess morbidity and mortality in the acute phase, but also persisting symptoms 4 weeks after the onset of the disease. A review of international studies on the prevalence and diversity of the manifestations of postcoid syndrome is presented. The data on such a manifestation of post-COVID syndrome as postural orthostatic tachycardia syndrome (POTS) are accumulating. Pathogenetic mechanisms, modern diagnostic criteria and research data on the prevalence of this syndrome are presented in the article. The Canadian Cardiovascular Society has proposed medications as a treatment for POTS, including the sinus node If channel inhibitor ivabradine. Data from several studies showing the effectiveness of this drug for POTS, including after suffering COVID-19, are presented in the article. Clinical data on the prevalence of tachycardia among patients admitted to the Sechenov University hospital are presented. About 18% of patients with hypertension and 21% of patients with normal blood pressure had a high heart rate. A clinical example of the use of ivabradine in a patient after a coronavirus infection is presented. Drug interactions and individual tolerance of ivabradine in patients after coronavirus infection are being discussed. The authors put forward the hypothesis about the further prospect of using ivabradine in the treatment of clinical manifestations of postcoid syndrome on the basis of literature data and their own experience.

Long-Term Effects of Ivabradine on Cardiac Vagal Parasympathetic Function in Normal Rats

Background: The complex interactions that exist between the pacemaker current, I _f, and the parasympathetic nervous system could significantly influence the course of patients undergoing chronic therapy with the I _f blocker ivabradine. We thus aimed to assess the effects of chronic ivabradine therapy on autonomic modulation and on the cardiovascular response to in situ and in vitro parasympathetic stimulation. The right atrial expression of HCN genes, encoding proteins for I _f, was also evaluated. Methods: Sympathetic and parasympathetic heart rate variability parameters and right atrial HCN(1-4) RNA levels were analyzed in 6 Control and 10 ivabradine-treated male Wistar rats (IVA; 3 weeks, 10 mg/kg/day). The heart rate (HR) and systolic blood pressure (SBP) responses to in situ electrical stimulation of the vagus nerve (2-20 Hz) were assessed in 6 additional Control and 10 IVA rats. The spontaneous sinus node discharge rate (SNDR) response to in vitro cholinergic receptors stimulation using carbamylcholine (10^-9-10^-6 mol/L) was also assessed in these later rats. Results: Ivabradine significantly increased vagal modulation and shifted the sympatho-vagal balance toward vagal dominance. In Control, in situ vagus nerve stimulation induced progressive decrease in both the SBP (p = 0.0001) and the HR (p< 0.0001). Meanwhile, in IVA, vagal stimulation had no effect on the HR (p = 0.16) and induced a significantly lower drop in SBP (p< 0.05). IVA also displayed a significantly lower SNDR drop in response to carbamylcholine (p< 0.01) and significantly higher right atrial HCN4 expression (p = 0.02). Conclusion: Chronic ivabradine administration enhanced vagal modulation in healthy rats. In addition, ivabradine reduced the HR response to direct muscarinic receptors stimulation, canceled the cardioinhibitory response and blunted the hemodynamic response to in situ vagal stimulation. These data bring new insights into the mechanisms of ivabradine-related atrial proarrhythmia and suggest that long-term I _f blockade may protect against excessive bradycardia induced by acute vagal activation.