A rare case of giant mediastinal tumor originating from lung tissue characterized by high fever and arrhythmia.

Background: Arrhythmias in patients with cancer are predominantly attributed to heart disease, anti-tumor drugs, and primary cardiac tumors. Arrhythmias directly induced by noncardiac primary tumors are rare. To date, there have been no reported cases of paroxysmal supraventricular tachycardia or sinus bradycardia caused by a posterior mediastinal tumor originating from the lung tissue. Case description: We present the case of a 65-year-old male diagnosed with a giant posterior mediastinal tumor originating from the lung tissue, A mediastinal lymph node biopsy was performed, and histopathological examination revealed a poorly differentiated adenocarcinoma of pulmonary origin. Based on the PET-CT and cranial enhancend MRI results, the posterior mediastinal tumor has a diameter exceeding 7 cm and has metastasized to the right hilar and mediastinal lymph nodes, with no distant metastasis observed. On the basis of these findings, the patient was diagnosed with stage IIIB mediastinal lung adenocarcinoma (cT4N3M0). The tumor measured 12.8 cm × 8.1 cm and could not be completely resected. Prior to immunochemotherapy, the patient experienced paroxysmal supraventricular tachycardia, followed by sinus bradycardia. After the first cycle of immunochemotherapy, the arrhythmia was corrected, and the body temperature returned to normal. However, the massive tumor led to malnutrition and various complications prior to the second cycle of treatment. Despite undergoing chemotherapy combined with immunotherapy, the patient's condition worsened, ultimately resulting in death. The overall survival period was 3 months. Conclusion: This case report highlights the fact that a giant mediastinal lung adenocarcinoma can induce arrhythmias, which may manifest as supraventricular tachycardia or sinus bradycardia. Additionally, tumor fever also can induce elevated temperatures of 39 °C. Notably, giant posterior mediastinal tumors that are unsuitable for resection have a significantly poorer prognosis.

Corticosteroid-induced bradycardia following high-dose methylprednisolone administration: a case report.

Introduction: Besides their wide use in the clinical field due to their anti-inflammatory and immune-modulating effect, corticosteroids still have a lot of adverse effects. The most common adverse effects are hyperglycemia, hypertension, osteoporosis, psychosis, immunosuppression, weight gain, and hyperlipidemia. Another important side effect is cardiac arrhythmias. Case presentation: We report a case of a 43-year-old woman with multiple sclerosis who developed symptomatic bradycardia after 3 days of treatment with a high dose of methylprednisolone. The patient received a dose of atropine and her bradycardia resolved after 36 h of stopping methylprednisolone. Discussion: While tachyarrhythmias are more common, bradyarrhythmias such as bradycardia and premature atrial or ventricular contraction are rare but crucial to be considered. Conclusion: Corticosteroid-induced bradycardia is usually in sinus rhythm and has an unknown etiology, possibly occurring at high and low doses. The majority of cases in the literature were asymptomatic and resolved spontaneously.

Comparison of Hemodynamic and Recovery Profile Between Segmental Thoracic Spinal and General Anesthesia in Upper Abdominal and Breast Surgeries: A Systematic Review and Meta-Analysis.

Segmental thoracic spinal anesthesia (STSA) has been described primarily as case reports for performing upper abdominal and thoracic surgeries in significant respiratory comorbid patients. A few comparative studies have recently evaluated the technique as an advantageous alternative to general anesthesia (GA). However, there is no systematic evaluation and comparison of the techniques. The present systematic review evaluated the hemodynamic, comfort, and satisfaction of patients undergoing abdominal and thoracic surgeries under STSA and GA. PubMed, CENTRAL, Google Scholar Advanced, and citation tracking were performed to find suitable articles that compared STSA and GA. The primary objective-related data were hypotension and bradycardia. The secondary objective-related data in the context of postoperative nausea vomiting (PONV), pain, rescue analgesics, sedation requirement, satisfaction, and comfort were assessed. Meta-analysis was performed for dichotomous data on hypotension, bradycardia, and PONV; odds ratio (OR) and 95% confidence interval (CI) were reported. Data of 394 patients from six studies were evaluated. Patients undergoing upper abdominal and breast surgeries under STSA had significantly higher odds of hypotension (Fixed-Effect Model OR 12.23, 95% CI 2.81-53.28; I2 =0%, and the Random Effects Model OR 12.01, 95% CI 2.75-52.52; I2 =0%) and bradycardia (Fixed-Effect Model OR 10.95, 95% CI 2.94-40.74, I2 =0%, and the Random Effects Model OR 9.97, 95% CI 2.61-38.08; I2 =0%) but lower odds of PONV (Fixed-Effect Model OR 0.24, 95% CI 0.13-0.43; I2 =0%, and the Random Effects Model OR 0.24, 95% CI 0.13-0.45; I2 =0%). Most of the patients undergoing STSA were given intravenous sedation to overcome anxiety and discomfort. Overall, patient satisfaction was on par with GA. However, few surgeons were unenthusiastic about the technique while performing axillary clearances due to bothering twitches from cautery. STSA led to early post-anesthesia care unit (PACU) discharge and provided better pain control, lowering the need for rescue analgesics and opioid consumption in the first 24-hour postoperative period. STSA is associated with very high odds of hypotension and bradycardia as compared to GA. On the other hand, STSA demonstrated superior pain control, reduced opioid requirements, shorter PACU stays, and significantly reduced risk of PONV. Nevertheless, STSA patients mostly require sedation to make the patient comfortable.

A case report of fludarabine associated ectopic atrial bradycardia and literature review of fludarabine induced bradycardia.

BACKGROUND: Fludarabine is a chemotherapeutic agent with lymphodepleting effects that is increasingly used as part of a conditioning regimen prior to allogeneic stem cell transplantation. Fludarabine is generally considered a relatively safe medication with only rare cases of cardiotoxic side effects. CASE PRESENTATION: Here, we present a case of a 30-year-old woman who was undergoing conditioning for a haploidentical cell transplantation for treatment of Fanconi anemia with a 5-day course of daily fludarabine infusion. After her second fludarabine infusion, she was noted to have ectopic atrial bradycardia that resolved with supportive therapy and completion of fludarabine infusion. CONCLUSION: We report the first case of ectopic atrial bradycardia associated with fludarabine. Although rare and transient, clinicians should recognize this rare cardiotoxic side effect of fludarabine.

Fetal bradycardia and acidosis during maternal parenteral iron: Case reports and literature review.

Iron deficiency anemia is an important problem among pregnant women, and intravenous (IV) iron infusions have been increasingly used. Whether fetal monitoring is required during infusion has been debated, with a recent guideline by Hematologists recommending against such. We report two cases of fetal bradycardia after iron isomaltoside (IIM), in women with otherwise good maternal and fetal health. Both developed dyspnea with desaturation minutes from infusion, followed by persistent fetal bradycardia. Both underwent category 1 CS, with cord arterial pH of 7.08 and 6.94 respectively. Upon literature review, only three case reports on fetal bradycardia in IV iron were identified. For older IV iron formulations, a case was reported after IV dextran test dose, while two cases after ferric gluconate were reported. For the new formulation IIM, only one case was reported so far, but in a woman with Crohn's disease and intrauterine growth restriction. IV iron in pregnancy carries risk of anaphylactic or hypersensitivity reactions, even with the newest formulations and in women with good maternal and fetal health. While rarely reported so far, fetal bradycardia is a possible consequence, commonly preceded by respiratory symptoms. Fetal monitoring should therefore be considered during infusion.

Anti-N-Methyl-D-Aspartate Receptor Encephalitis and Life-Threatening Sinus Node Dysfunction: A Case Report, Literature Review, and Analysis of 23 Cases.

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is the most common form of autoimmune encephalitis, presenting with various psychiatric manifestations, including behavioral and cognitive impairments, movement disorders, decreased consciousness, dysphasia, seizures, and autonomic dysfunction. Autonomic dysfunction may involve hyperthermia, apnea, hypotension, tachycardia, and life-threatening manifestations of sinus node dysfunction (SND), such as bradycardia, sinus pause or arrest, and asystole. The severity and significance of SND are critical, as it is not uncommon for these patients to progress into asystolic cardiac arrest, potentially contributing to morbidity and mortality. Accordingly, we present the case of an 18-year-old female with anti-NMDAR encephalitis who experienced multiple episodes of sinus pause/arrest and asystolic cardiac arrest, achieving a return of spontaneous circulation after successful CPR in all instances, ultimately requiring permanent pacemaker implantation. Additionally, we performed a literature review and analyzed 23 similar anti-NMDAR encephalitis cases with SND manifestations, including sinus pause/arrest or asystolic cardiac arrest, to identify common risk factors and describe management strategies and outcomes. Moreover, we investigated the potential association between teratoma and permanent pacemaker use in SND.

Uterine sacrifice in obstetric emergencies case series: Complex cases of fetal distress, labor challenges, and life-saving interventions.

This study highlights the complexities and challenges in managing obstetric emergencies, detailing critical interventions and outcomes in various high-risk cases. A retrospective analysis was conducted on four high-risk obstetric cases, each characterized by distinct complications necessitating immediate medical interventions. The study specifically examined cases involving: Fetal Distress cases where fetal health was compromised, necessitating interventions such as emergency cesarean sections. Complex Labor Dynamics detailed examinations of labor complications such as obstructed labor, precipitate labor, or labor complicated by malpresentation. Early pregnancy complications analysis focused on emergencies arising in the first trimester or early second trimester, including ectopic pregnancies and complications in pregnancies with a history of multiple cesarean sections. Severe postpartum hemorrhage investigations into cases of significant blood loss post-delivery, which required interventions ranging from pharmacological management to surgical procedures like hysterectomy. The first case concerned a 28-year-old primigravida with fetal bradycardia and thick meconium, requiring an emergency cesarean section. Postoperative complications included gestational thrombocytopenia and anemia, necessitating a total abdominal hysterectomy for severe sepsis. The newborn showed good recovery, indicated by Apgar scores. In Case 2, the need for a hysterectomy following complications during the third stage of labor was likely due to the presence of Placenta Accreta Spectrum, specifically placenta accreta or increta. While a retained placenta typically can be managed with less invasive methods, the situation escalates when the placenta is abnormally adherent to, or deeply invasive into, the uterine muscle. This can lead to uncontrollable bleeding, making a hysterectomy necessary and justified as a life-saving measure to control the severe hemorrhage while the histology confirms the diagnosis for the placenta accreta. In the third case, the decision to perform a dilation and curettage over manual vacuum aspiration was influenced by several factors. Given the severity of the patient's hemorrhage and the presence of a suspicious echogenic structure, a dilation and curettage provided a more controlled environment for thorough evacuation and immediate bleeding control. This approach was also supported by the combination technique using both Karman aspiration and a curette, allowing for effective management of complicated cases, particularly in patients with a history of multiple cesareans and potential scar tissue. The fourth case involved a 37-year-old multipara with severe postpartum hemorrhage from uterine atony, treated with surgery and managed for diabetic ketoacidosis, leading to discharge on the fourth day. This underscores the urgency and complexity of managing obstetric emergencies effectively.

Neuromodulation for Vasovagal Syncope and Bradyarrhythmias.

Catheter-based neuromodulation of intrinsic cardiac autonomic nervous system is increasingly being used to improve outcomes in patients with vasovagal syncope and bradyarrhythmias caused by vagal overactivity. However, there is still no consensus for patient selection, technical steps, and procedural end points. This review takes the reader on a practical exploration of neuromodulation for bradyarrhythmias, concentrating on the critical aspects of proper patient selection, evidence-based insights, and anatomic intricacies within the intrinsic cardiac autonomic nervous system. Also discussed are different mapping techniques and outcome measures. Future directions to optimize the utilization of this technique in clinical practice are highlighted.

Neuronavigation assisted percutaneous balloon compression of the gasserian ganglion for trigeminal neuralgia. How I do it.

BACKGROUND: Surgical treatment for trigeminal neuralgia includes percutaneous techniques, including balloon compression, first described in 1983 by Mullan and Lichtor (J Neurosurg 59(6):1007-1012, 6). METHOD: Here we present a safe and simple navigation-assisted percutaneous technique for balloon compression, which can also be used for glycerol injection. CONCLUSION: The navigation-assisted percutaneous technique for balloon compression for trigeminal neuralgia is a quick and safe treatment for patients not candidates for microvascular decompression.

Cardioneuroablation for the treatment of reflex syncope and functional bradyarrhythmias: A Scientific Statement of the European Heart Rhythm Association (EHRA) of the ESC, the Heart Rhythm Society (HRS), the Asia Pacific Heart Rhythm Society (APHRS) and the Latin American Heart Rhythm Society (LAHRS).

Cardioneuroablation has emerged as a potential alternative to cardiac pacing in selected cases with vasovagal reflex syncope, extrinsic vagally induced sinus bradycardia-arrest or atrioventricular block. The technique was first introduced decades ago, and its use has risen over the past decade. However, as with any intervention, proper patient selection and technique are a prerequisite for a safe and effective use of cardioneuroablation therapy. This document aims to review and interpret available scientific evidence and provide a summary position on the topic.

Non-Surgical Bleeding and Transurethral Resection of the Prostate (TURP) Syndrome after TURP Surgery: A Case Report and Literature Review.

Patients undergoing transurethral resection of the prostate (TURP) surgery can develop TURP syndrome and post-TURP bleeding. Post-TURP bleeding can be surgical, from arteries or venous sinuses, or non-surgical, due to coagulopathy preventing clot formation. Non-surgical post-TURP bleeding may be due to high concentrations of urokinase and tissue plasminogen activator (tPA) in the urine that cause fibrinolytic changes and increase bleeding risk. Urine urokinase and tPA may have both local and systemic fibrinolytic effects that may prevent blood clot formation locally at the site of surgery, and cause fibrinolytic changes systemically through leaking into the blood stream. Another post-TURP complication that may happen is TURP syndrome, due to absorption of hypotonic glycine fluid through the prostatic venous plexus. TURP syndrome may present with hyponatremia, bradycardia, and hypotension, which may be preceded by hypertension. In this case report, we had a patient with benign prostatic hyperplasia (BPH) who developed both TURP syndrome and non-surgical post-TURP bleeding. These complications were transient for one day after surgery. The local effect of urine urokinase and tPA explains the non-surgical bleeding after TURP by preventing clot formation and inducing bleeding. Coagulation studies showed fibrinolytic changes that may be explained by urokinase and tPA leakage into the blood stream. In conclusion, non-surgical bleeding after TURP can be explained by the presence of fibrinolytic agents in the urine, including urokinase and tPA. There is a deficiency in existing studies explaining the pathophysiology of the fibrinolytic changes and risk of bleeding after TURP. Herein, we discuss the possible pathophysiology of developing fibrinolytic changes after TURP. More research effort should be directed to explore this area to investigate the appropriate medications to treat and prevent post-TURP bleeding. We suggest monitoring patients' coagulation profiles and electrolytes after TURP because of the risk of developing severe acute hyponatremia, TURP syndrome, fibrinolytic changes, and non-surgical bleeding. In our review of the literature, we discuss current clinical trials testing the use of an antifibrinolytic agent, Tranexamic acid, locally in the irrigation fluid or systemically to prevent post-TURP bleeding by antagonizing the fibrinolytic activity of urine urokinase and tPA.

The effectiveness of dexmedetomidine for preventing acute kidney injury after surgery: a systematic review and meta-analysis.

Background: Postoperative acute kidney injury (AKI) is a serious and distressing complication connected to various adverse outcomes following the surgical operation. Controversy remains regarding the dexmedetomidine's preventive impact on postoperative AKI. Therefore, this investigation aims to explore the efficiency and safety of dexmedetomidine in preventing AKI after surgical operation. Methods: We systematically searched electronic databases such as PubMed, Embase, Web of Science, and the Cochrane Library to detect eligible randomized controlled studies that used dexmedetomidine for the prevention of AKI following operation up to April 30, 2023. The main outcome evaluated was AKI incidence. The evidence quality was assessed employing the Grading of Recommendations Assessment, Development, and Evaluation. Results: The meta-analysis included 25 trials, including 3,997 individuals. Of these, 2,028 were in the dexmedetomidine group, and 1,969 were in the control group. The result showed that patients administered dexmedetomidine significantly decreased the AKI incidence following surgical operation in contrast to the control group (risk ratio, 0.60; 95% confidence intervals, 0.45-0.78; p < 0.05; I 2 = 46%). In addition, dexmedetomidine decreased the period of hospitalization in both the intensive care unit (ICU) and the hospital while also reducing postoperative delirium (POD) occurrence. However, dexmedetomidine elevated the incidence of bradycardia but did not have a significant impact on other indicators. Conclusion: Our meta-analysis indicates that the dexmedetomidine treatment reduces the postoperative AKI and POD risk while also shortening the time of hospitalization in the ICU and hospital. However, it is connected to an increased bradycardia risk.

Oculocardiac Reflex in a Patient With Maxillofacial Trauma: A Case Study and Literature Review.

Oculocardiac reflex (OCR), presenting as bradycardia and asystole, is a potential intraoperative complication that may occur during maxillofacial trauma surgery. Bradycardia is the most common symptom of this phenomenon. Surgeons should be aware of its long-term effects, such as arrhythmias and even cardiac arrest. We report the case of a 40-year-old male patient with a fracture of the floor of the orbit. During a surgical exploration of the orbital floor, the patient exhibited sudden symptoms of OCR. It was managed by withholding the surgery and administering atropine. The article also highlights the mechanism, types, incidence, and management of OCR in patients with maxillofacial trauma.

Síndrome de QT largo congénito y bradicardia fetal: la importancia del diagnóstico / Congenital long QT syndrome and fetal bradycardia: the importance of the diagnosis

Antecedentes: El síndrome de QT largo es una canalopatía que afecta a la repolarización ventricular y aumenta el riesgo de sufrir arritmias ventriculares graves. Puede ser congénito o adquirido, y es una causa conocida de muerte súbita. Caso clínico: Gestante primigesta, de 28 años, sin antecedentes de interés. En ecografías prenatales se objetivó en el feto bradicardia sinusal mantenida desde la semana 28, sin repercusión hemodinámica, que persistió hasta la finalización de la gestación (semana 37+3). Al nacimiento se realizaron electrocardiogramas seriados que mostraron alteraciones en la repolarización con alargamiento del intervalo QT corregido. Se realizó estudio genético que confirmó síndrome de QT largo tipo 1 y se inició tratamiento oral con beta-bloqueantes, con buena respuesta. Conclusiones: El síndrome de QT largo suele diagnosticarse posnatalmente. Es importante conocer sus características clínicas prenatales para poder establecer un diagnóstico precoz y minimizar así el riesgo de muerte súbita de estos pacientes.

Background: Long QT syndrome is a channelopathy that affects ventricular repolarization and increases the risk of severe ventricular arrhythmias. It can be congenital or acquired, and is a known cause of sudden cardiac death. Case report: A 28-year-old primigravida with no significant medical history. Prenatal ultrasounds revealed sustained fetal sinus bradycardia from week 28, without hemodynamic repercussion, which persisted until the end of gestation (at 37+3 weeks). Serial electrocardiograms were performed after birth, showing repolarization abnormalities with prolonged corrected QT interval. A genetic study confirmed long QT syndrome type 1, and oral treatment with beta-blockers was initiated, showing a positive response. Conclusions: Long QT syndrome is often diagnosed postnatally. It is important to be aware of his prenatal clinical features in order to establish an early diagnosis and minimize the risk of sudden death in these patients.

The Prevalence of Bradycardia 12 Years After Roux-en-Y Gastric Bypass for Severe Obesity.

PURPOSE: The aim was to describe the frequency of bradycardia 12 years after Roux-en-Y gastric bypass (RYGB), relations to weight loss, patient characteristics, and the clinical impact. MATERIALS AND METHODS: The BAROPS study is a prospective observational study of patients who had follow-up > 10 years after RYGB. Patients with heart rate (HR) ≤ 50 bpm were compared to patients with HR > 50 bpm. RESULTS: After a mean observation period of 12 years, 32 of 546 patients (6%) had a HR ≤ 50 with a mean HR of 47.0 (2.8) bpm. The comparator group (192 patients) had a mean HR of 66.4 (10.2) bpm (p < 0.001). A higher proportion of the bradycardic vs. non-bradycardic patients (18.8% vs. 7.8% at baseline (p = 0.05) and 18.8% vs. 5.2% at end of study (p = 0.006)) used beta-blockers. Both groups had a significant reduction in heart rate from pre-surgery to end of observation. Percent total weight loss from baseline was negatively related to heart rate (p < 0.001), and smoking was positively related to heart rate (p = 0.014). Change in BMI from pre-surgery (p < 0.001) and hypertension at pre-surgery (p = 0.006) were significant predictors of change in heart rate. The only predictor of HR ≤ 50 was the use of beta-blockers (p = 0.010). There were no difference in bradycardia-related symptoms. CONCLUSION: Six percent of patients had HR ≤ 50 bpm 12 years after RYGB, but there was no increased bradycardia-related symptoms in these patients. RYGB induced a significant reduction in HR, and heart rate and changes in heart rate 12 years after RYGB were related to the amount of weight loss.

Sinus bradycardia as a rare adverse event in patients receiving cyclosporine A after allogeneic hematopoietic stem cell transplantation.

Cyclosporine A (CSA) is a commonly used immunosuppressive agent for the prophylaxis of graft-versus-host disease following allogeneic hematopoietic stem cell transplantation (alloHSCT). While tachycardia is a known adverse effect of CSA, bradycardia remains a phenomenon rarely described in the literature. We conducted a retrospective evaluation of the incidence of bradycardia in patients after alloHSCT treated with CSA between January 2020 and February 2023 at our center. Out of 206 patients, sinus bradycardia following the administration of CSA was observed in 6 (2.9%), comprising 3 women and 3 men, with the median age of 55 years (range: 20-65). The underlying diseases were myeloid malignancies in 4 and aggressive lymphoma in 2 patients. The patients received grafts from a matched unrelated (n=5) or a haploidentical family donor (n=1) following various conditioning regimens. Coexisting cardiovascular disorders were found in 5 of the 6 patients. All patients experienced symptomatic bradycardia within 1-4 days (median 2 days) after CSA introduction, which persisted until CSA withdrawal. One patient required treatment with atropine. All patients continued their immunosuppressive therapy with tacrolimus, which was well-tolerated Our study indicates CSA as a causative factor of sinus bradycardia in a small percentage of alloHSCT patients receiving CSA as graft-versus host disease (GvHD) prophylaxis. Importantly, these patients did not experience any cardiac complications when switched to tacrolimus. Although further research on the effects of CSA on heart automatation is needed, our single-center experience can help prompt diagnosis and therapeutic intervention in daily clinical practice.

First-in-man clinical implantation and acute pacing performance of a novel subxiphoidal pacemaker system.

BACKGROUND: Intravascular cardiac pacemakers are an established therapy for bradycardic indications. Recently, a new class of leadless pacemakers have mitigated some of the complications related to pacemaker leads. In this study, we evaluate the implantation and performance of a novel extravascular technology that delivers epicardial pacing through a subxiphoidal approach. METHODS: Fifteen patients undergoing non-emergent open-heart surgery were enrolled. A midline incision was made just below the xiphoid process, and substernal tunneling was used to create a pocket for the device and to access the anterior pericardium over the right ventricle. The test device (Calyan Technologies, Oakdale, MN) was temporarily inserted underneath the ribcage and clipped to the xiphoid process. The sensing and pacing electrode (FlexArm) was positioned on the anterior pericardium. Ventricular sensing and pacing capture thresholds were measured. RESULTS: The test device was successfully implanted in all 15 patients. There were no device or procedure-related adverse events. The first five implanted patients had no pacing capture at maximum stimulation intensity. Design changes were made to the device, including different electrode size and shape, and successful ventricular capture was achieved in 9 of the subsequent 10 patients. In these patients, pacing threshold was 3.8 ± 1.6 mA with a pulse width of 0.5 ms. All devices were successfully explanted at the end of the procedure. CONCLUSIONS: In a first-in-human experience with a novel extravascular pacemaker, this study demonstrated the feasibility of pericardial ventricular pacing via a subxiphoidal approach. Further chronic studies are required to evaluate the safety and performance of this novel pacing technology.

Reference ranges for ambulatory heart rate measurements in a middle-aged population.

BACKGROUND: Elevated heart rate (HR) predicts cardiovascular disease and mortality, but there are no established normal limits for ambulatory HR. We used data from the Swedish CArdioPulmonary Imaging Study to determine reference ranges for ambulatory HR in a middle-aged population. We also studied clinical correlates of ambulatory HR. METHODS: A 24-hour ECG was registered in 5809 atrial fibrillation-free individuals, aged 50-65 years. A healthy subset (n=3942) was used to establish reference values (excluding persons with beta-blockers, cardiovascular disease, hypertension, heart failure, anaemia, diabetes, sleep apnoea or chronic obstructive pulmonary disease).Minimum HR was defined as the lowest 1-minute HR. Reference ranges are reported as means±SDs and 2.5th-97.5th percentiles. Clinical correlates of ambulatory HR were analysed with multivariable linear regression. RESULTS: The average mean and minimum HRs were 73±9 and 48±7 beats per minute (bpm) in men and 76±8 and 51±7 bpm in women; the reference range for mean ambulatory HR was 57-90 bpm in men and 61-92 bpm in women. Average daytime and night-time HRs are also reported. Clinical correlates, including age, sex, height, body mass index, physical activity, smoking, alcohol intake, diabetes, hypertension, haemoglobin level, use of beta-blockers, estimated glomerular filtration rate, per cent of predicted forced expiratory volume in 1 s and coronary artery calcium score, explained <15% of the interindividual differences in HR. CONCLUSION: Ambulatory HR varies widely in healthy middle-aged individuals, a finding with relevance for the management of patients with a perception of tachycardia. Differences in ambulatory HR between individuals are largely independent of common clinical correlates.