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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.

Inappropriate sinus tachycardia (IST) is a clinical syndrome that generally affects young patients and is associated with distressing symptoms. Although the most common symptom is palpitations, it can be accompanied by a myriad of symptoms, including anxiety, dizziness, presyncope, and syncope. The pathogenesis of IST is not well understood and considered multifactorial, with autonomic dysfunction being the central abnormality. IST is a diagnosis of exclusion. Management presents a clinical challenge. The overall efficacy of lifestyle modifications and medical therapy may be limited. Recent advances in catheter and surgical sinus node sparing ablation techniques have led to improvement in outcomes. In addition, increased focus has led to development of multimodality team-based interventions to improve outcomes in this group of patients. In this review, we discuss the mechanistic basis of IST, review current approaches to diagnosis, and outline contemporary therapeutic approaches., Competing Interests: Funding Support and Author Disclosures Dr Lakkireddy has been a consultant for Johnson & Johnson, Abbott, Biotronik, Pfizer, and Boston Scientific. Dr Gopinathannair has been a consultant/speaker for Abbott Medical, Boston Scientific, and Biosense Webster. Dr Olshansky has been a consultant for Sanofi; Chair of DSMB REDUCE IT–Amarin; and U.S. coordinator of GLORIA AF at Boehringer Ingelheim. Dr Russo has provided research support at Boston Scientific, Kestra, Medilynx, and Medtronic; has been a consultant for Abbott, Atricure, Biosense Webster, Boston Scientific, Medtronic, and PaceMate; has received honoraria from Biotronik, Bristol Myers Squibb/Pfizer, and Medtronic; and has received royalties from Up-to-Date. Dr LaMeier has been a consultant at Atricure. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Inappropriate sinus tachycardia (IST) has been defined as a resting heart rate of >100 beats per minute and an average 24-hour heart rate >90 bpm with distressing symptoms resulting from the persistent tachycardia. IST is prevalent in 1% of the middle-aged population, mostly females. Rarely can elderly patients also present with IST. Possible mechanisms of IST include intrinsic sinus node abnormality, beta-adrenergic receptor stimulating autoantibody, beta-adrenergic receptor supersensitivity, muscarinic receptor autoantibody, or hyposensitivity, impaired baroreflex control, depressed efferent parasympathetic/vagal function, nociceptive stimulation, central autonomic overactivity, aberrant neurohumoral modulation, etc. Symptoms associated with IST are palpitations, chest pain, fatigue, shortness of breath, presyncope, and syncope. Despite these distressing symptoms, IST has not been associated with tachycardia-associated cardiomyopathy or increased major cardiovascular events. Various treatment options for patients with IST are ivabradine, beta-adrenergic blockers, calcium channel blockers, psychiatric evaluation, and exercise training. Although, endocardial radiofrequency ablation targeting the sinus node has been used as a treatment modality for otherwise treatment-refractory IST, the results have been dismal. The other modalities used for refractory IST treatment are endocardial modification of the sinus node using radiofrequency energy, combined endo and epicardial ablation of the sinus node, thoracoscopic epicardial ablation of the sinus node, sinus node sparing thoracoscopic and endocardial hybrid ablation. The goal of this review is to provide the readership with the pathophysiological basis of IST and its management options., Competing Interests: The authors declare no conflict of interest. Dr. Kanjwal is the consultant for St Jude Medical and Bio sense webster., (© 2021 The Author(s). Published by IMR Press.)

Achieving the goal management of some arrhythmic syndromes can be challenging; medical treatment for inappropriate sinus tachycardia (IST) and postural orthostatic tachycardia syndrome (POTS) may be ineffective, necessitating multidisciplinary team treatment. Implantable defibrillator devices (ICDs), along with anti-arrhythmic drugs (AADs), remain the first-line treatment for primary electrical diseases that pose a risk of sudden cardiac death (SCD). Ablation of the arrhythmogenic substrate is not always suggested in patients with these pathologies, but it may be a valuable support for reducing arrhythmic burden, improving quality of life, and treating pathologies that are resistant to pharmacological treatment; however, this option is not often considered due to the potential risks associated with an invasive approach. Minimally invasive hybrid ablation in these syndromes, such as a hybrid thoracoscopic approach and the use of non-invasive mapping systems, reduces post-surgery complications and ensures the best possible outcome for the patient., (© 2021. Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

A patient with coronary artery fistula should be considered as high risk for intraoperative hemodynamic decompensation. In this article, we report the case of a 70-year-old man affected by a complex congenital coronary artery fistula defect. The patient underwent general anesthesia for spine surgery with permissive hypotension. The development of sudden intraoperative tachyarrhythmia with hemodynamic instability required immediate resuscitation and interruption of surgery. The claim advanced is that in patients with a coronary artery fistula permissive hypotension might be considered an option only if strictly necessary and real-time cardiac monitoring including transesophageal echocardiography is available to immediately detect and treat acute cardiac impairment.

Editor's note: This is the second installment in a new series on electrocardiogram (ECG) interpretation. Nurses in all settings should know the basics, as medications and physiological changes can cause cardiac arrhythmias. Each article will start with a brief case scenario and an ECG strip and then take you step by step through analyzing the heart rhythm.

Inappropriate sinus tachycardia (IST) is a common disease of the autonomic nervous system in children and adults. Diagnosis and treatment of IST in adolescents is not well defined. In this retrospective study, we tested our hypothesis regarding autonomic dysfunction in childhood by analyzing 24-h heart rate variability (HRV) in 479 children, with a mean age of 13.7 ± 2.1 years, who were referred to the outpatient clinic in the Pediatrics Department within the last 15 years. Seventy-four adolescents with a mean 24-h heart rate ≥ 95 bpm (our cut-off for an IST based upon 66 healthy controls) were deemed to have IST. We found the risk of IST to be high in adolescents with attention deficit disorder (OR = 3.5,p<0.001), pre-hypertension (OR = 2.5, p = 0.043) and hypertension (OR = 2.1,p = 0.02); insignificantly enhanced in children with short stature (OR = 1.9,p = 0.19), surgically-treated congenital heart disease (OR = 1.4,p = 0.51) and obesity without hypertension (OR = 1.4;p = 0.25); and negligible in adolescents with anorexia nervosa (OR = 0.3, p = 0.26) and constitutional thinness (OR = 0.9,p = 0.89). IST was associated with a significant decrease in global HRV and elevated blood pressures, indicating an enhanced cardiovascular risk. Methylphenidate did not increase 24-h heart rates, whereas omega-3 fatty acid supplementation significantly decreased elevated heart rates and increased HRV in adolescents with IST. In this retrospective analysis, 15.4% of adolescents suffered from IST with a 24-h heart rate ≥ 95 bpm, predominately due to attention deficit disorder and hypertension., Competing Interests: The authors have declared that no competing interests exist.

Background: Limited data are available regarding the demographics, disease associations, and long-term prognosis of patients with inappropriate sinus tachycardia (IST)., Objective: To establish epidemiologic data for patients with IST, including symptom onset, comorbid disease, and long-term outcomes., Methods: We retrospectively reviewed all patients with an IST diagnosis at the Mayo Clinic (Rochester, MN) during a 20-year period (1998-2018). We extracted demographic data and clinical outcomes compared to an age and gender-matched control group with atrioventricular nodal reentry tachycardia (AVNRT)., Results: Within the study period, a total of 305 patients with IST were identified (mean follow-up 3.5 years) with 92.1% female and mean age 33.2 ± 11.2 years. The most frequently identified circumstances triggering the condition included pregnancy (7.9%) and infectious illness (5.9%) while the most common comorbid conditions were depression (25.6%) and anxiety (24.6%). At diagnosis, the mean left ventricular ejection fraction (LVEF) was 62.3 ± 6.2%, with 77 patients having follow-up echocardiographic data. No significant difference in LVEF was seen after a mean 4.9 ± 4.3-year follow-up (baseline LVEF 59.8 ± 10.7% vs subsequent 61.4 ± 8.1%; P = .2971). Two deaths occurred within the study period, with one related to myocardial infarction and the other noncardiac; compared to an age and gender-matched AVNRT control group there was no excess mortality during the follow-up period., Conclusions: In our study cohort, IST predominately affects young females with structurally normal hearts and modest coexistent psychiatric disease. In most cases of IST, a major event occurring just before or at the time of diagnosis could not be identified, although nearly 8% of patients first noted symptoms during or shortly after pregnancy. In our cohort, there was no evidence of cardiomyopathy or mortality related to IST., (© 2019 Wiley Periodicals, Inc.)

Background: Inappropriate sinus tachycardia (IST) remains a clinical challenge because patients often are highly symptomatic and not responsive to medical therapy., Objective: To study the safety and efficacy of stellate ganglion (SG) block and cardiac sympathetic denervation (CSD) in patients with IST., Methods: Twelve consecutive patients who had drug-refractory IST (10 women) were studied. According to a prospectively initiated protocol, five patients underwent an electrophysiologic study before and after SG block (electrophysiology study group). The subsequent seven patients had ambulatory Holter monitoring before and after SG block (ambulatory group). All patients underwent SG block on the right side first, and then on the left side. Selected patients who had heart rate reduction ≥15 beats per minute (bpm) were recommended to consider CSD., Results: The mean (SD) baseline heart rate (HR) was 106 (21) bpm. The HR significantly decreased to 93 (20) bpm (P = .02) at 10 minutes after right SG block and remained significantly slower at 97(19) bpm at 60 minutes. Left SG block reduced HR from 99 (21) to 87(16) bpm (P = .02) at 60 minutes. SG block had no significant effect on blood pressure or HR response to isoproterenol or exercise (all P > .05). Five patients underwent right (n = 4) or bilateral (n = 1) CSD. The clinical outcomes were heterogeneous: one patient had complete and two had partial symptomatic relief, and two did not have improvement., Conclusion: SG blockade modestly reduces resting HR but has no significant effect on HR during exercise. Permanent CSD may have a modest role in alleviating symptoms in selected patients with IST., (© 2019 The Authors. Journal of Cardiovascular Electrophysiology published by Wiley Periodicals, Inc.)

Inappropriate sinus tachycardia (IST) is a clinical syndrome, oftentimes debilitating, defined by fast sinus rates (>100 b.p.m. at rest or >90 b.p.m. on average over 24 h and not due to underlying causes) associated with symptoms that may include palpitations, as described in some guidelines and consensus documents. While heart rates may vary by patient, especially based upon gender and age, some individuals experience sinus tachycardia or persistent fast sinus rates with no symptoms; these individuals would not necessarily be considered to have the syndrome of IST. Various explanations for IST have been considered but a definitive common mechanism is not yet known; the true aetiology may be multifactorial. A thorough evaluation of secondary causes of tachycardia is required in the work-up of all cases and if found, must be treated before a diagnosis of IST can be made. Finally, effective treatments vary but can include ivabradine, beta-blockers, or calcium channel antagonists; ablation is seldom advised.

Sinus tachycardia may have a definite aetiology, but in the remaining cases inappropriate sinus tachycardia (IST) may be considered. IST is primarily treated in order to improve symptoms. During pregnancy, tachycardia-induced cardiomyopathy is rare; however, it needs urgent attention and treatment due to the risk of fast progression. In Denmark, performing an electrocardiogram is recommended in any pregnant woman, who has palpitations or a persisting heart rate > 100 beats per minute.

Purpose: The purpose of this report was to review the basic mechanisms underlying cardiac automaticity. Second, we describe our clinical observations related to the anatomical and functional characteristics of sinus automaticity., Methods: We first reviewed the main discoveries regarding the mechanisms responsible for cardiac automaticity. We then analyzed our clinical experience regarding the location of sinus automaticity in two unique populations: those with inappropriate sinus tachycardia and those with a dominant pacemaker located outside the crista terminalis region., Results: We studied 26 patients with inappropriate sinus tachycardia (age 34 ± 8 years; 21 females). Non-contact endocardial mapping (Ensite 3000, Endocardial Solutions) was performed in 19 patients and high-density contact mapping (Carto-3, Biosense Webster with PentaRay catheter) in 7 patients. The site of earliest atrial activation shifted after each RF application within and outside the crista terminalis region, indicating a wide distribution of atrial pacemaker sites. We also analyzed 11 patients with dominant pacemakers located outside the crista terminalis (age 27 ± 7 years; five females). In all patients, the rhythm was the dominant pacemaker both at rest and during exercise and located in the right atrial appendage in 6 patients, in the left atrial appendage in 4 patients, and in the mitral annulus in 1 patient. Following ablation, earliest atrial activation shifted to the region of the crista terminalis at a slower rate., Conclusions: Membrane and sub-membrane mechanisms interact to generate cardiac automaticity. The present observations in patients with inappropriate sinus tachycardia and dominant pacemakers are consistent with a wide distribution of pacemaker sites within and outside the boundaries of the crista terminalis.

Background: Inappropriate Sinus Tachycardia (IST) is a clinical syndrome characterized by a sinus heart rate inexplicably higher than one hundred beats per minute at rest that is associated with symptoms like palpitations, dyspnea or dizziness in the absence of primary causes of tachycardia. The diagnosis requires exclusion of other causes of tachycardia including medications/substances (such as anti-cholinergic, beta-blocker withdrawal, caffeine, and alcohol) or medical conditions (such as panic attacks, pulmonary embolism, fever, hyperthyroidism, hypovolemia, anemia, and pain)., Methods: Work up should include an EKG to differentiate other causes of tachycardia, 24 hour- Holter monitor if indicated, serum thyroid levels, hemoglobin levels and toxicology screen. Electrophysiological studies are not routinely recommended, but should be considered in certain patients in whom concurrent supraventricular tachycardia is suspected., Conclusion: The underlying pathology in IST is yet to be completely understood. However, it is thought that the causes of IST can be broadly classified into two groups; either as an intrinsic increase in sinus node automaticity or an extrinsic cause. Among extrinsic causes, there is evolving evidence that IgG anti-β receptor antibodies are found in IST causing tachycardia. Managing patients with IST includes lifestyle modification, non-pharmacological and pharmacological interventions. Ivabradine has recently emerged as an effective treatment of IST and was shown to be superior to beta-blockers., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)

Inappropriate Sinus Tachycardia (IST) is a chronic medical condition with a wide variety of clinical presentations making it, sometimes, very insidious at the time of the diagnosis. Several therapeutic options, including, pharmacotherapy, cardiac rehabilitation, and modification or ablation of the sinus node, have been proposed for the management of IST, but because of the complexity and lack of understanding of pathophysiology, it can be difficult to manage, despite the numerous treatment options currently available. The purpose of this review is to analyze the treatment for IST, focusing on the role of newer therapy and the potential benefits in the management of this cardiac rhythm disturbance.

Objectives: The aim of this study was to share our experience in the diagnosis and treatment of patients who presented at our clinic with syncope, pre-syncope, dizziness, and palpitations., Study Design: Patients who were treated at pediatric cardiology clinic for complaints of syncope, dizziness, and palpitations between 2014 and 2016 were enrolled in the study. Detailed history of the patients, physical examination findings, laboratory and electrocardiogram results were recorded. Tilt table test, 24-hour Holter rhythm monitoring, and exercise test were performed, as required. Patients were diagnosed as vasovagal syncope, postural orthostatic tachycardia syndrome (POTS), or inappropriate sinus tachycardia based on these findings. Treatment of the patients was evaluated., Results: Thirty patients were diagnosed as vasovagal syncope, 7 patients as POTS, and 2 as inappropriate sinus tachycardia. POTS accompanied Raynaud's phenomenon in 1 patient, hypertrophic cardiomyopathy in 1 patient, and homocystinuria in another patient. Complaints of patients with vasovagal syncope improved with non-medical therapy. Medical treatment was administered to the patients with diagnosis of POTS and inappropriate sinus tachycardia., Conclusion: In patients with complaints of syncope, pre-syncope, dizziness, and palpitations without structural heart disease or non-rhythm problems, cardiovascular autonomic disorders, such as POTS and inappropriate sinus tachycardia should be kept in mind, as well as vasovagal syncope.

Objectives: The goal of this study was to describe short- and long-term outcomes in all patients referred for inappropriate sinus tachycardia ablation, along with the potential complications of the intervention., Background: Sinus node (SN) ablation/modification has been proposed for patients refractory to pharmacological therapy. However, available data derive from limited series., Methods: The electronic databases MEDLINE, Embase, CINAHL, Cochrane, and Scopus were systematically searched (January 1, 1995-December 31, 2015). Studies were screened according to predefined inclusion and exclusion criteria., Results: A total of 153 patients were included. Their mean age was 35.18 ± 10.02 years, and 139 (90.8%) were female. All patients had failed to respond to maximum tolerated doses of pharmacological therapy (3.5 ± 2.4 drugs). Mean baseline heart rates averaged 101.3 ± 16.4 beats/min according to electrocardiography and 104.5 ± 13.5 beats/min according to 24-h Holter monitoring. Two electrophysiological strategies were used, SN ablation and SN modification, with the latter being used more. Procedural acute success (using variably defined pre-determined endpoints) was 88.9%. Consistently, all groups reported high-output pacing from the ablation catheter to confirm absence of phrenic nerve stimulation before radiofrequency delivery. Need of pericardial access varied between 0% and 76.9%. Thirteen patients (8.5%) experienced severe procedural complications, and 15 patients (9.8%) required implantation of a pacemaker. At a mean follow-up interval of 28.1 ± 12.6 months, 86.4% of patients demonstrated successful outcomes. The symptomatic recurrence rate was 19.6%, and 29.8% of patients continued to receive antiarrhythmic drug therapy after procedural intervention., Conclusions: Inappropriate sinus tachycardia ablation/modification achieves acute success in the vast majority of patients. Complications are fairly common and diverse. However, symptomatic relief decreases substantially over longer follow-up periods, with a corresponding high recurrence rate., (Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Hyperactivity of the cardiac sympathetic nervous system may underlie the pathogenesis of inappropriate sinus tachycardia (IST). Studies have proven that cervical vagal stimulation could inhibit stellate ganglion neural activity., Subjects: To investigate whether noninvasive vagal nerve stimulation (NVNS) could inhibit sympathetically induced sinus node acceleration by reducing right stellate ganglion (RSG) neural activity., Methods: Sixteen anesthetized dogs were randomly divided into NVNS group (with NVNS, n = 8) and control group (with sham NVNS, n = 8). NVNS was delivered to the vagus nerve innervating at the right tragus with a voltage of 80% below the threshold, the minimal voltage to slow the sinus rate or atrioventricular conduction. The maximal sinus rate accelerations induced by high-frequency stimulation (HFS) of RSG and RSG neural activity were measured at baseline and 3 hours after NVNS. At the end, SK2, c-fos, and NGF protein expression in RSG were examined in both groups., Results: Compared to baseline, the maximal sinus node acceleration induced by RSG stimulation and the RSG neural activity were both significantly attenuated after 3 hours of NVNS (P < 0.05 for both). However, these indices did not change significantly in the control group (P > 0.05). SK2 expression in RSG was significantly higher and c-fos and NGF expressions were significantly lower in the NVNS group than those in the control group (P < 0.05)., Conclusion: Noninvasive vagal nerve stimulation may suppress RSG activity possibly by modulating SK2, c-fos, and NGF expressions in RSG, thus inhibiting sympathetically induced sinus node acceleration., (© 2015 Wiley Periodicals, Inc.)

The HAWAI registry evaluated the role of heart rate variability in predicting the occurrence of ventricular tachycardia and fibrillation (VT/VF) and sinus tachycardia in patients with an implantable cardioverter-defibrillator (45 patients with 155 RR recordings). A significant decrease of the mean value of all RR intervals (MeanNN) was observed in the period starting 20 and 40 min prior to VT/VF and sinus tachycardia, respectively. The standard deviation of RR intervals (SDNN) and the power at low frequency (LF) were the only parameters with significant changes prior to VT/VF. For sinus tachycardia, the root mean square of successive differences of all successive RR intervals (r-MSSD) and the power at low and high frequency (HF) decreased, whereas SDNN and the power at very low frequency increased. Comparison of RR recordings preceding VT/VF and sinus tachycardia revealed significant differences of the MeanNN, SDNN, r-MSSD, LF and HF. Based on a classification and regression tree analysis, MeanNN, SDNN and r-MSSD showed a sensitivity of 94.4% and a specificity of 50.6% as predictors of VT/VF. Our results suggest that the temporal changes in heart rate before an arrhythmic event can be used to predict the occurrence of VT/VF. These parameters may be used to optimize pacing therapies designed to prevent VT/VF recurrences as well as for improving device-based discriminators for VT/VF and sinus tachycardia.

Inappropriate sinus tachycardia is characterized by an unexplained increase of the resting sinus rate (> 100 bpm) with excess increase in response to moderate activity (mean heart rate > 90 bpm/24 h). Affected patients may suffer from heart race, palpitations, fatigue, weakness and dizziness. The mechanisms underlying inappropriate sinus tachycardia and its long term prognosis are poorly understood. Thus, diagnosis and treatment are empiric and require the initial exclusion of potential causes of secondary sinus tachycardia. Therapeutic approaches include physical training, beta blockers or ivabradine. Radiofrequency catheter ablation should be restricted to patients with refractory and longstanding symptoms., (© Georg Thieme Verlag KG Stuttgart · New York.)

Patients with episodic sinus tachycardia and associated orthostatic intolerance present a diagnostic and management dilemma to the clinician. We define this group of disorders to include sinus node reentrant tachycardia (SNRT), inappropriate sinus tachycardia (IAST), and postural orthostatic tachycardia syndrome (POTS). After a brief review of the current understanding of the pathophysiology and epidemiology of this group of disorders, we focus on the diagnosis and management of IAST and POTS. Our approach attempts to recognize the considerable overlap in pathophysiology and clinical presentation between these two heterogeneous conditions. Thus, we focus on a mechanism-based workup and therapeutic approach. Sinus tachycardia related to identifiable causes should first be ruled out in these patients. Next, a basic cardiovascular and autonomic workup is suggested to exclude structural heart disease, identify a putative diagnosis, and guide therapy. We review both nonpharmacologic and pharmacologic therapy, with a focus on recent advances. Larger randomized control trials and further mechanistic studies will help refine management in the future.

Inappropriate sinus tachycardia (IST) is a syndrome in which the sinus heart rate is inexplicably faster than expected and associated symptoms are present. The heart rate at rest, even in a supine position, can exceed 100 beats/min; minimal activity accelerates the rate rapidly and substantially. Patients with IST may require restriction from physical activity. Mechanisms responsible for IST are understood incompletely. It is important to distinguish IST from so-called appropriate sinus tachycardia and from postural orthostatic tachycardia syndrome, with which overlap may occur. Because the long-term outcome seems to be benign, treatment may be unnecessary or may be as simple as physical training. However, for patients with intolerable symptoms, therapeutic measures are warranted. Even at high doses, β-adrenergic blockers, the first-line therapy, often are ineffective; the same is true for most other medical therapies. In rare instances, catheter- or surgically- based right atrial or sinus node modification may be helpful, but even this is fraught with limited efficacy and potential complications. Overtreatment, in an attempt to reduce symptoms, can be difficult to avoid, but is discouraged., (Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

In recent years, intravenous lipid emulsion (ILE) therapy has emerged as a new rescue antidote for treatment of certain toxicities, including cyclic antidepressants, and as the primary treatment of toxic manifestations after local anesthetic exposure. We present a case of a 13-year-old girl who developed delayed seizures and cardiac arrest after amitriptyline ingestion. As part of the treatment, she was treated with ILE therapy. The patient's laboratories were not interpretable for several hours after the lipid emulsion. The patient developed pancreatitis after the ILE therapy. This case is unique; not only is it one of the first reported cases of lipid emulsion being used in a pediatric patient, but in that the patient developed delayed toxicity and iatrogenic harm from the ILE.

Scombroid syndrome is a fish poisoning characterised by the onset of symptoms compatible with a pseudoallergic reaction; it is rarely also responsible of signs and symptoms of acute coronary syndromes, as demonstrated in this case report.

Inappropriate sinus tachycardia (IST) is an uncommon form of arrhythmia characterized by an increased heart rate that is out of proportion to a normal physiologic demand. The etiology of IST remains ill-defined and controversial. Clinical presentation of IST is highly variable, from isolated to sustained palpitations, and can cause deterioration in one's quality of life. IST is usually a diagnosis of exclusion and it is important to rule out other causes of sinus tachycardia before reaching a final diagnosis. Evaluation of cardiac autonomic reflex function is essential to support the diagnosis of IST. The treatment of IST aims to target the multiple mechanisms involved in this disease, and multidisciplinary management, including cardiac rehabilitation, pharmacotherapy, and occasionally radiofrequency modification of the sinus node, should be considered. The prognosis is usually benign, although regular follow-up is required to optimize therapy and prevent the onset of tachycardiomyopathy.

Objective: Few data are available on sinus tachycardia among medical intensive care unit (ICU) patients. We investigated new critical illnesses related to new-onset prolonged sinus tachycardia (NOPST) and the relationship of NOPST with ICU mortality., Methods: The heart rate (HR) of all enrolled patients was monitored hourly over a 12-month period, and NOPST was defined as sinus tachycardia (>100 beats/min) with an increase in HR of more than 20% from the baseline value lasting longer than 6 hours., Results: Among the 522 patients enrolled, the average mean HR was 96.1 ± 18.4 beats/min. Fifty-two (10.0%) patients met the criteria for NOPST; pneumonia, delirium, septic shock, acute respiratory distress syndrome, catheter-related infections, and mechanical ventilator-related problems were related to the occurrence of NOPST. The ICU mortality rate in patients with a NOPST duration of more than 72 hours was higher compared with other patients with NOPST (60.0% vs 18.5%; P = .002). A high daily mean HR rather than NOPST was a significant predictor of ICU mortality (odds ratio, 1.415; 95% confidence interval, 1.177-1.700)., Conclusions: Although NOPST was not associated with ICU mortality, it indicates the presence of new critical events in the medical ICU setting., (Copyright © 2011 Elsevier Inc. All rights reserved.)

History: A 3-year-old, 400 kg, gelding Quarter Horse was presented for investigation of epistaxis., Physical Examination: The horse was bright, alert and responsive with rectal temperature, heart rate and respiration rate within normal limits., Management: During a second general anaesthetic for surgical treatment of guttural pouch mycosis by balloon-tipped catheter occlusion of the right major palatine artery and ligation of the right external carotid artery, signs consistent with hyperkalaemic periodic paralysis (HYPP) were exhibited. These included concurrent hyperkalaemia, hypercapnoea, sinus tachycardia, and muscle fasciculations in the presence of normothermia. Stress associated with an acute haemorrhage pre-operatively, and intra-operative hypercapnoea may have precipitated the episode. There were no signs of HYPP during a general anaesthetic, 1 week earlier, when an initial attempt at surgical treatment of guttural pouch mycosis was performed. Treatment consisted of fluid therapy and administration of calcium gluconate (0.1-0.2 mg kg(-1) minute(-1)), dextrose 5% (5 mL kg(-1) hour(-1)) and insulin (0.05 IU kg(-1)). Treatment resulted in the resolution of clinical signs and an uneventful recovery., Follow-Up: The diagnosis of HYPP was confirmed by DNA analysis post-operatively., Conclusions: Clinical cases of intra-operative HYPP can present despite a previous history of uneventful general anaesthesia. Rapid diagnosis and treatment can result in the successful management of HYPP. This report documents an unusual presentation of HYPP, a disease that remains present in the Quarter Horse population., (© 2011 The Authors. Veterinary Anaesthesia and Analgesia © 2011 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.)

Arrhythmias in children can be classified according to their effect on central pulse: Fast pulse rate - tachyarrhythmia; Slow pulse rate - bradyarrhythmia; and Absent pulse is pulseless arrest (cardiac arrest). Tachyarrythmia may be narrow complex tachycardia (QRS duration ≤ 0.08 s): sinus tachycardia (ST), supraventricular tachycardia (SVT), atrial flutter or Wide-complex tachycardia (QRS duration >0.08 s): ventricular tachycardia (VT), SVT with aberrant intraventricular conduction. The choice of therapy depends on the patient's degree of hemodynamic instability. Attempt vagal stimulation, if patient is stable and if it does not unduly delay chemical or electrical cardioversion. Bradyarrhythmias include: sinus bradycardia, sinus node arrest with atrial, junctional and idioventricular escape rhythms and AV block. The emergency treatment of bradycardia depends on its hemodynamic consequences. If heart rate is <60 beats per minute with poor perfusion despite effective ventilation with oxygen, it may be treated with chest compressions, epinephrine through IV or endotracheal tube. If bradycardia persists or responds only transiently, consider a continuous infusion of epinephrine or isoproterenol and plan for emergency transcutaneous pacing. If bradycardia is due to vagal stimulation or primary A-V block, giving atropine may be beneficial.

Inappropriate sinus tachycardia (IST) is characterised by an exaggerated increase of heart rate in response to normal physiologic demands. Therapeutic options including medical and radiofrequency ablation interventions are still under debate. Ivabradine inhibits spontaneous pacemaker activity of the sinus node by selectively blocking If channels of pacemaker cells. Here we present a case of a patient with IST, who was successfully treated with ivabradine after various ineffective therapeutic approaches.

We report the case of an 18-year-old man with Danon disease, a genetic disorder inclunding a severe hypertrophic cardiomyopathy with very broad QRS, who had an implantable cardioverter defibrillator for primary prevention. Nine months after implantation, he received two inappropriate shocks due to R-wave double counting during sinus tachycardia. We discuss how to avoid such inappropriate therapy.

The present case describes a patient who received inappropriate, but potentially life-saving, therapy from her implantable cardioverter defibrillator (ICD) in the setting of acute hyperkalemia (plasma potassium concentration = 8 mM). Hyperkalemia was associated with the development of a slow sinusoidal ventricular tachycardia, at a rate of 100 beats/min to 125 beats/min (610 ms to 480 ms) in a patient who is pacemaker-dependent. There was associated fractionation of the ICD electrogram and T wave oversensing, leading to ventricular oversensing with resultant detection in the ventricular fibrillation rate zone. This was followed by shock therapy, even though the ventricular tachycardia rate was below the programmed detection rate of the ICD. The subsequent emergency treatment of the hyperkalemia normalized the electrogram, corrected the ventricular oversensing and arrhythmia, and restored rate-adaptive single-chamber ventricular pacing.

Inappropriate sinus tachycardia (IST) is an uncommon form of arrhythmia which is characterized by an exaggerated increase in heart rate that is out of proportion to normal physiologic demands. Usually, IST is triggered by orthostasis, minimal exertion, and psychological stress. The etiology of IST remains ill-defined. However, proposed mechanisms include: enhanced sinus node automaticity, alterations in autonomic function associated with increased sympathetic activity or reduced parasympathetic activity, and impaired baroreflex control. Recently, increased levels of autoantibodies to beta-adrenergic receptors have been observed in patients with IST. The clinical presentation of IST is highly varied and ranges from short episodes of palpitations associated with dyspnea, atypical precordial pain, cephalalgia, fatigue, and occasional syncope and presyncope to incapacitating incessant tachycardia. In general, IST is a diagnosis of exclusion. It is important that other causes of sinus tachycardia are excluded before making a diagnosis. Evaluation of autonomic function is essential for a diagnosis of IST. Treatment of IST is based on autonomic function findings and involves multidisciplinary management, including cardiac rehabilitation. Control and restitution of normal autonomic function is essential. The prognosis is benign though regular follow-up is required to optimize therapy.

Amatoxins are one of the most potent toxins that cause hepatic and renal failure. However, this is the first report demonstrating an elevation of cardiac enzymes in a patient with Amanita phalloides poisoning. A 56-year-old male was admitted to the emergency department (ED) 42 h after an unknown type of mushroom ingestion. Hepatic, renal function tests, amylase and cardiac enzymes (troponin I, creatine kinase (CK), CK-MB isoenzyme and myoglobin) were found elevated in his blood chemistry. The electrocardiogram disclosed sinus tachycardia. Aggressive treatment with fluids, activated charcoal, penicillin G and silibinin were started. The patient was sent to hemodialysis because of anuria. During follow-up, biochemical parameters and clinical findings improved. The patient was discharged from the hospital following the arrangement of hemodialysis schedule because of the chronic renal failure. False elevations of cardiac markers may confuse the clinicians in differential diagnosis of myocardial infarction in ED. In our patient, amatoxins that have bound the actin filaments within myocardiocytes or renal cells and/or its effects as circulating anti-troponin antibodies might result in elevation of cardiac markers. Elevated cardiac enzyme levels without any acute coronary syndrome are probable in mushroom poisoning cases involving amatoxin ingestion.

Background: Inappropriate sinus tachycardia (IST) is characterized by heart rate (HR) increase out of proportion to stress level. Radiofrequency (RF) modification of the sinus node (SN) is an accepted treatment modality for medically refractory IST. We describe a new technique using noncontact mapping and a saline irrigated catheter for SN modification., Methods: Seven consecutive patients with medically refractory IST were referred for ablation. Intrinsic heart rate (IHR) was calculated with complete autonomic blockade by atropine and propranolol. Isoproterenol (ISO) 1 mcg/min was initiated and increased to 10 mcg/min. Site of earliest activation was tagged at each dose of ISO once stable HR was achieved. RF ablation to target site of earliest activation at peak HR on ISO 10 mcg/min was performed. With any change in P-wave morphology, activation was reassessed and the new site of earliest activation targeted. Endpoint was a decrease in HR and change in P-wave morphology in lead III and aVF., Results: Five of seven patients had abnormal IHR. Mean number of RF lesions was 25 (10-52). All patients had either flattening of the P wave or development of negative P waves in leads III and aVF post RF associated with a decrease in HR of > or = 25% from baseline off ISO. A caudal shift of the site of early activation compared with baseline was observed. One patient who had a prior SN modification developed symptomatic intermittent junctional bradycardia and required an atrial pacemaker 2 weeks later. The other 6 patients in follow-up from 6 to 24 months had no further IST., Conclusions: Noncontact mapping using the described technique in conjunction with the saline-cooled ablation catheter for SN modification in the treatment of IST may provide effective HR control.

Myocardial injury is known to occur in victims of both thermal and electrical burns. A variety of mechanisms have been ascribed to the pathogenesis of cardiac damage during burn shock. However, limited evidence exists that coronary artery thrombosis plays a frequent role. Distinguishing between acute coronary syndrome (impending myocardial infarction from coronary artery occlusion) vs global cardiac injury is essential; the care diverges drastically. The following case describes a patient who was angiographically proven to have acute coronary thrombosis amidst burn shock ftera 50% TBSA electrical flash burn. Managing the patient's burn shock, myocardial injury, and multiple surgical procedures while considering antiplatelet medications for a newly placed coronary artery stent presented a number of challenges not previously reported.

Organ procurement coordinators must treat various cardiac dysrhythmias (arrhythmias), including rhythm disturbances that may cause or follow a cardiac arrest, in about 15% to 50% of donors. Treatment decisions should be based on the particular dysrhythmia and its effect on donor blood pressure. Medications selected should be effective but short acting. In this article, data available in publications located through a PubMed search are reviewed and specific dysrhythmias that are likely to occur during donor care are described. Treatment recommendations are based on guidelines from the American Heart Association.

Background: Inappropriate sinus tachycardia (IAST) and postural orthostatic tachycardia syndrome (POTS) are syndrome complexes with some distinctive features, overlapping clinical manifestations, and potential common mechanisms. Pathogenesis of these overlapping syndromes is poorly understood. Diagnostic and therapeutic approaches have not been standardized., Purpose: This article provides an overview of the definition, clinical presentation, and proposed mechanisms of IAST and other overlapping syndromes. A stepwise diagnostic approach is suggested. A multidisciplinary management scheme is outlined., Methods: A MEDLINE search for English-language articles on IAST, POTS, and chronic orthostatic intolerance published up to 2005 was performed. Published data incorporated with our clinical experience were synthesized and presented in this review., Results: The population of IAST is heterogeneous and underlying mechanisms are complex and likely multifactorial. Evidence suggests that both cardiac and extracardiac causes are plausible. Regional and limited autonomic neuropathies, at least in part, can provide a mechanism-based explanation of the cardiovascular indices and clinical symptoms in a significant number of patients with IAST. The regional abnormalities can be detected by autonomic testing. Among patients with IAST and evidence of autonomic dysregulation, an integrated autonomic, cardiovascular, and psychiatric management approach appears to be logical and rational when appropriate. Sinus node ablation could be considered in patients with persistent IAST in the absence of autonomic neuropathy and multisystem symptoms. Data from long-term outcomes are lacking., Conclusion: The current understanding of IAST mechanisms is incomplete and management approach is not adequate. Significant effort needed in clinical research to improve therapeutic outcome.