Proposed mechanisms of relative bradycardia

Unmasking Pandemic Echoes: An In-Depth Review of Long COVID's Unabated Cardiovascular Consequences beyond 2020

At the beginning of 2020, coronavirus disease 2019 (COVID-19) emerged as a new pandemic, leading to a worldwide health crisis and overwhelming healthcare systems due to high numbers of hospital admissions, insufficient resources, and a lack of standardized therapeutic protocols. Multiple genetic variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been detected since its first public declaration in 2020, some of them being considered variants of concern (VOCs) corresponding to several pandemic waves. Nevertheless, a growing number of COVID-19 patients are continuously discharged from hospitals, remaining symptomatic even months after their first episode of COVID-19 infection. Long COVID-19 or 'post-acute COVID-19 syndrome' emerged as the new pandemic, being characterized by a high variability of clinical manifestations ranging from cardiorespiratory and neurological symptoms such as chest pain, exertional dyspnoea or cognitive disturbance to psychological disturbances, e.g., depression, anxiety or sleep disturbance with a crucial impact on patients' quality of life. Moreover, Long COVID is viewed as a new cardiovascular risk factor capable of modifying the trajectory of current and future cardiovascular diseases, altering the patients' prognosis. Therefore, in this review we address the current definitions of Long COVID and its pathophysiology, with a focus on cardiovascular manifestations. Furthermore, we aim to review the mechanisms of acute and chronic cardiac injury and the variety of cardiovascular sequelae observed in recovered COVID-19 patients, in addition to the potential role of Long COVID clinics in the medical management of this new condition. We will further address the role of future research for a better understanding of the actual impact of Long COVID and future therapeutic directions.

Typhoid fever, complicated by syncope due to relative bradycardia: A case report

In a United Nations (UN) staff member headquarters in South Sudan, we present a rare typhoid fever complicated by syncope due to relative bradycardia. A 25-year-old male presented to our hospital with a high fever, diarrhea, and no vomiting. He had no substantial medical background. He was diagnosed with an unspecified digestive disorder and received initial treatment. Two syncope episodes were recorded in the Level 1 hospital. He was referred to our hospital at the 30th hour and the third fainting occurred. Electrocardiogram showed bradycardia with a heart rate of 40 beats/min. The atropine test was negative; the initial diagnosis was sinus sickness syndrome. Microbiology tests later suggested typhoid infection. Then, the diagnosis changed to relative bradycardia caused by Salmonella typhi; and he was orally treated with the third-generation Quinolone antibiotic. He significantly improved and got discharged on the seventh day. In conclusion, typhoid remains a real and present threat to UN staff and civilians in South Sudan.

Remdesivir associated sinus bradycardia in patients with COVID-19: A prospective longitudinal study

Background: Remdesivir is effective against SARS-Cov-2 with little evidence of its adverse effect on the cardiac system. The aim of the present study is investigating the incidence of bradycardia in COVID-19 patients treated with Remdesivir. Methods: This prospective longitudinal study was conducted in a tertiary center on COVID-19 patients for Remdesivir therapy. The objectives were to investigate the incidence of sinus bradycardia, and also the association between their demographics, underlying diseases, and the disease severity with developing bradycardia in COVID-19 patients treated with Remdesivir. Results: Of 177 patients, 44% were male. The mean (±standard deviation) age of patients was 49.79 ± 15.16 years old. Also, 33% were hospitalized due to more severe symptoms. Oxygen support was required for all hospitalized subjects. A total of 40% of the patients had comorbidities, with the most common comorbidity being hypertension. The overall incidence of bradycardia (heart rate<60 bpm) in patients receiving Remdesivir was 27%, of whom 70% had extreme bradycardia (heart rate <50 bpm). There was also a statistically significant reduction in heart rate after five doses of Remdesivir compared to the baseline heart rates. In the multivariable model, none of the covariates including age above 60 years, female sex, CRP>50 mg/L, O2 saturation<90%, underlying cardiovascular disease, hypertension and diabetes mellitus, and beta-blockers were associated with Remdesivir-induced bradycardia. No association was found between the COVID-19 severity indicators and bradycardia. Conclusion: As sinus bradycardia is a prevalent adverse cardiac effect of Remdesivir, it is recommended that all COVID-19 patients receiving Remdesivir, be evaluated for heart rate based on examination; and in the case of bradyarrhythmia, cardiac monitoring should be performed during administration to prevent adverse drug reactions.

Relative bradycardia presented as a clinical feature of Brucella melitensis infection: A case report

Brucellosis, caused by Brucella species, is an infectious disease transmitted through contact with infected animals or their secretions. The clinical disease is characterized by fever and headache. Relative bradycardia is an inappropriate response of heart rate to body temperature, in which the heart rate does not increase proportionally despite a high fever. In this report, we document one case of Brucella melitensis infection demonstrating relative bradycardia. To our knowledge, this is the first report of relative bradycardia in a patient with brucellosis.

Relative bradycardia in patients with moderate-to-severe COVID-19: a retrospective cohort study

Coronavirus-related disease (COVID-19) can result in relative bradycardia; however, there are no reports on relative bradycardia in patients with moderate-to-severe COVID-19 who require oxygen. We retrospectively investigated 45 patients with moderate-to-severe COVID-19 and examined the relationship between heart rate and body temperature at the time of initiating oxygen or mechanical ventilation. For three consecutive days after initiating oxygen therapy, body temperature (day’s highest temperature), heart rate, and other vital signs were measured simultaneously. We checked for relative bradycardia and analyzed the differences between patients with moderate COVID-19 (oxygen requirement ≤ 5 L/min) and those with severe COVID-19 (oxygen requirement ≥ 5 L/min). Of the 45 patients, 28 and 17 had moderate and severe COVID-19, respectively. The heart rate increased with increasing body temperature, and almost all patients satisfied the criteria of relative bradycardia. In Spearman’s rank correlation analysis, body temperature was significantly correlated with heart rate (ρ = 0.483, p = 0.012) in moderately ill patients but not in severely ill patients (ρ = 0.261, p = 0.297). Multiple regression analysis revealed that the severity of COVID-19 and body temperature were independent predictors of heart rate. The predicted change in heart rate was 6.0 beats/min for each 1 °C rise in body temperature. Relative bradycardia was suggested to be a characteristic finding in patients with moderate-to-severe COVID-19 who require oxygen. Additionally, severely ill patients were more likely to develop relative bradycardia than moderately ill patients. Focusing on the relationship between heart rate and body temperature might help clinicians diagnose this disease in patients with worsening respiratory failure.

COVID-19 and the heart

An outbreak of coronavirus disease 2019 (COVID-19) occurred in December 2019 due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is a strain of SARS-CoV. Patients infected with the virus present a wide spectrum of manifestations ranging from mild flu-like symptoms, cough, fever and fatigue to severe lung injury, appearing as bilateral interstitial pneumonia or acute respiratory failure. Although SARS-CoV-2 infection predominantly offends the respiratory system, it has been associated with several cardiovascular complications as well. For example, patients with COVID-19 may either develop type 2 myocardial infarction due to myocardial oxygen demand and supply imbalance or acute coronary syndrome resulting from excessive inflammatory response to the primary infection. The incidence of COVID-19 related myocarditis is estimated to be accountable for an average of 7% of all COVID-19 related fatal cases, whereas heart failure (HF) may develop due to infiltration of the heart by inflammatory cells, destructive action of pro-inflammatory cytokines, micro-thrombosis and new onset or aggravated endothelial and respiratory failure. Lastly, SARS-CoV-2 can engender arrhythmias through direct myocardial damage causing acute myocarditis or through HF decompensation or secondary, through respiratory failure or severe respiratory distress syndrome. In this comprehensive review we summarize the COVID-19 related cardiovascular complications (acute coronary syndromes, myocarditis, HF, arrhythmias) and discuss the main underlying pathophysiological mechanisms.

Bradycardia and Heart Rate Fluctuation Are Associated with a Prolonged Intensive Care Unit Stay in Patients with Severe COVID-19

Background and Objective: Bradycardia has been observed among patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is suspected to be associated with poorer outcomes. Heart rate (HR) fluctuation has been found to be correlated with a greater mortality rate in critically ill patients. The association of bradycardia and HR fluctuation with the outcome of severe coronavirus disease 2019 (COVID-19) patients has not been clarified. Therefore, we aimed to examine whether bradycardia and HR fluctuation correlated with poor outcomes in patients with severe COVID-19. Materials and Methods: We conducted a secondary analysis from a prospective data collection of patients admitted to the intensive care unit, between April and June 2021, at Chiang Mai University Hospital. Results: The results showed that 62 of 86 patients (72.1%) had bradycardia, defined by HR < 60 beats per minute (bpm). The number of patients with high HR fluctuation, defined as the difference in HR during admission ≥ 40 bpm, was greater among the bradycardia group than in the non-bradycardia group (70.9% vs. 14.7%, p = 0.015, respectively). The patients with bradycardia had greater levels of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). In addition, a greater proportion of patients with bradycardia received interleukin-6 inhibitors and hemoperfusion as a rescue therapy than those with non-bradycardia. After adjusting for age, gender, body mass index, CRP, and mechanical ventilator; bradycardia and the high HR fluctuation were significantly associated with a longer length of stay in the intensive care unit (ICU-LOS), with adjusted risk ratios of 2.67, 95% CI; 1.02, 6.94, p = 0.045 and 2.88, 95% CI; 1.22, 6.78, p = 0.016, respectively. Conclusion: We found that bradycardia and a high heart rate fluctuation were associated with a poorer ICU outcome in terms of longer ICU-LOS among the patients with severe COVID-19.

Meta-analysis and systematic literature review of COVID-19 associated bradycardia as a predictor of mortality

Background

Cardiac arrhythmias have been identified as independent predictors of mortality in Coronavirus disease 2019 (COVID-19) patients. While some studies have reported poor prognosis with bradycardia in COVID-19 patients, others have not found any association between bradycardia and mortality in COVID-19 patients. This study aims to assess the relationship between bradycardia and mortality in COVID-19 patients by reviewing existing literature.

Main body

Articles were obtained by systematically searching the PubMed and Google scholar databases. Qualitative and quantitative analyses of the studies on bradycardia and mortality in COVID-19 were done. A pooled estimate, with a sample size of 1320 patients, comparing the effect of patients that were bradycardic during their admission with those that were not on mortality showed that bradycardia did not lead to increased mortality in COVID-19 patients (OR 1.25, 95% CI 0.41–3.84, p = 0.7).

Conclusions

This meta-analysis showed that bradycardia was not significantly associated with mortality in COVID-19 patients. However, this study is limited by the few studies on bradycardia and mortality in COVID-19 patients. Therefore, future studies should investigate this relationship so that clinicians can prognostically triage and treat COVID-19 patients appropriately.

Relative bradycardia in patients with COVID-19

Introduction

Relative bradycardia(RB) is a relatively low heart rate response to rise in body temperature that occurs in several infectious diseases and can be an important clinical sign. In previous case reports, RB was presented in some patients with Coronavirus disease 2019 (COVID-19) COVID-19.

Objective and Methods

To investigate the correlation between temperature and heart rate, we retrospectively reviewed 249 febrile patients with documented COVID-19 patients. RB was defined as a rise in the heart rate from a basal heart rate of less than 10 beats/minute/°C rise in temperature.

Results

In this study, the prevalence of RB in patients with COVID-19 was 60.6%. When the HR at peak temperatures for patients with COVID-19 were compared with reference valve (general temperature-heart rate response in infectious disease), our findings demonstrate a relatively lower heart rate at all peak temperatures recorded. Despite differences in heart rate response, there were not significant differences in clinical outcomes (pulmonary manifestation, intensive care unit admission, Death).

Conclusions

Most patients with COVID-19 are associated with relative bradycardia, not related to clinical outcomes. RB in COVID-19 can be considered as the clinical features for differential diagnosis from other febrile conditions.

Clinical outcomes in acute pancreatitis with relative bradycardia at fever onset

While some acute pancreatitis (AP) patents with fever do not exhibit a corresponding increase in heart rate, the clinical significance of this phenomenon has not been studied. We investigated the clinical relevance of relative bradycardia (RB) in febrile AP.A retrospective electronic chart review was conducted on consecutive patients admitted for AP at a tertiary referral center in Japan from January 1, 2010, to May 31, 2018. Presence of RB was determined at the first instance of fever, based on formulas used in previous studies.Fever at or during admission was observed in 115 patients, of which 33% had RB. Fever was observed at presentation in 48% and within 48 hours in 94% of cases. Etiologies were alcoholic in 48% and gallstones in 17% of cases. RB patients were older (median age: 62 vs 51 years, P = .028) but had shorter median postfever lengths of stay (8 vs 12 days, P = .003), lower median Ranson scores (1 vs 2, P < .001), and were less likely to develop delirium (11% vs 38%, P = .002). Nineteen of 21 severe AP cases based on the Ranson score were nonbradycardia (P = .011). RB was also associated with lower white blood cell count, C-reactive protein, and lactate levels. On computed tomography, necrosis (P = .028) and moderate or severe pancreatitis (P = .041) were less frequently observed in patients with RB. There was a significant inverse correlation between RB and the Ranson score (-.305, P = .001). While RB was an independent predictors of postfever length of stay (LOS) in multiple regression analysis when the Ranson score was excluded (P = .010), it ceased to be significant when the Ranson score was included (P = .141).AP patients with RB at fever onset had milder disease and shorter LOS compared to those with higher heart rates at fever onset. RB may be useful as a simple, early predictor of shorter LOS before the Ranson score can be calculated.

COVID-19 induced bradyarrhythmia and relative bradycardia: An overview

Novel coronavirus 2019 (COVID-19) has been the focus of the medical community since its emergence in December 2019 and has already infected more than 100 million patients globally. Primarily described to cause a respiratory illness, COVID-19 has been found to affect almost every organ system. Bradycardia is a newly recognized ramification of COVID-19 that still has unknown prognostic value. Studies have shown an increase in the incidence of arrhythmias, cardiomyopathies, myocarditis, acute coronary syndromes, and coagulopathies in infected patients as well as an increased risk of mortality in patients with preexisting cardiovascular disease. While the pathogenesis of bradycardia in COVID-19 may be multifactorial, clinicians should be aware of the mechanism by which COVID-19 affects the cardiovascular system and the medication side effects which are used in the treatment algorithm of this deadly virus. There has yet to be a comprehensive review analyzing bradyarrhythmia and relative bradycardia in COVID-19 infected patients. We aim to provide a literature review including the epidemiology, pathogenesis, and management of COVID-19 induced bradyarrhythmia.

Multiple Sinus Pauses in a Patient With COVID-19

Cardiovascular complications in coronavirus disease 2019 (COVID-19) patients have been associated with poor prognosis. Myocarditis, acute coronary syndrome, heart failure, and arrhythmia have been reported. 

We present a case of a 55-year-old female patient with no significant past medical history who was admitted due to COVID-19 induced acute hypoxemic respiratory failure. She developed multiple asymptomatic episodes of long sinus pauses as her oxygen requirements increased. These resolved without atropine and pacing as her respiratory status improved.

Hypoxemia, cytokine storm, dysautonomia, direct viral infiltration, and surrounding myocardial inflammation are thought to be responsible for bradyarrhythmias associated with COVID-19. Both symptomatic and asymptomatic cases have been reported. Hospitalized COVID-19 patients should be monitored closely on telemetry in order to promptly recognize any arrhythmia; hence preventing an unexplained rapid decline in cardiopulmonary status by intensifying care and managing the arrhythmia in a timely manner. Follow-up studies would be needed to determine the long-term outcomes of COVID-19 patients who developed bradyarrhythmias.

Relative Bradycardia in Patients with Mild-to-Moderate Coronavirus Disease, Japan

Coronavirus disease is reported to affect the cardiovascular system. We showed that relative bradycardia was a common characteristic for 54 patients with PCR-confirmed mild-to-moderate coronavirus disease in Japan. This clinical sign could help clinicians to diagnose this disease.

Bradycardia in Patients With COVID-19: A Calm Before the Storm?

Cardiac manifestations of coronavirus disease 19 (COVID-19), including arrhythmia, have been described in the literature. However, to our knowledge, association of COVID-19 with bradycardia has not been reported. This case study describes sinus bradycardia as a potential manifestation of COVID-19.

This is a retrospective case series of four patients with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, admitted to St. Luke’s University Health Network ICU between 24 March 2020 and 5 April 2020. Medical records of these patients were reviewed using the EPIC electronic health record system. Demographic, clinical, laboratory, and treatment data were reviewed against periods of bradycardia in each patient.

The patient group comprised two males and two females. Two patients had pre-existing cardiovascular (CV) comorbidities but no history of arrythmias. Heart rates ranged between 66 and 88 beats/min on admission. The lowest rates during bradycardia were between 42 and 49 beats/min. The onset of sinus bradycardia in patients 1, 2, and 3 were day nine, 15, and five of illness, respectively. Patient 4 had three episodes of bradycardia, starting on day 10 of illness. Patients’ bradycardia episodes lasted one to 14 days. During bradycardia, maximum body temperatures ranged between 99.9 and 100.2 degree Fahrenheit. Patients 2, 3, and 4 required vasopressors to maintain mean arterial pressure > 65 mmHg during episodes. All four patients were on propofol at some point during bradycardia with patients 1, 2, and 3 also receiving dexmedetomidine. There was no consistent correlation of these medications with bradycardia. Electrocardiogram (ECG) findings included sinus bradycardia. Prolonged QTc interval observed in patient 2 on admission improved during bradycardia.

Transient sinus bradycardia is a possible manifestation of COVID-19 and is important for close CV surveillance. Etiology can be multifactorial, but severe hypoxia, inflammatory damage of cardiac pacemaker cells, and exaggerated response to medications are possible triggers. High levels of pro-inflammatory cytokines may act directly on the sinoatrial (SA) node contributing to the development of bradycardia. This may be a warning sign of the onset of a serious cytokine storm. An increased awareness of possible exaggerated bradycardia response is important to consider with the use of empiric medications which have arrhythmogenic effects.

A new theory based on possible existence of timing control by intracellular photons in tonically active neurons

Time perception in living organisms, especially mammals, and understanding the timing of their internal organs, have always been the topic of interest in neuroscience. In this study, our theory considers the photonic behavior on time control by some particular or some block of neurons. Photon emission by mitochondria has regular timing in intercellular process. In other words, due to the main mitochondrial function of cellular respiration as well as the source of photon emission, it is possible to deduce photon at a specific rate in TANs (Tonically Active Neurons). If photoreceptors exist in the neurons of the nervous system, photons can be received at a regulated time. Thereby, neurons can produce a constant-frequency signal for subsequent stimuli. Our studies conducted in the CNS (Central Nervous System) and TANs, and it seems that photoreceptors are present in TANs. Photons are interpreted by a series of neurons and produce an oscillating rhythm. These rhythms can be the basis of the body's chronological activity in different areas of the CNS. If this hypothesis is true, it can be deduced that an independent factor, excluding circadian activities, exists for living activities. Different neuronal structures will also be responsible for understanding the time. Although this hypothesis is far from a complete evaluation, it can compensate for some of the other problems. For instance, a series of inconsistencies that occur in some neurological diseases, such as Parkinson diseases can be well justified by this hypothesis.