Deciphering the sinus tachycardias

Cardiac Arrest After Adenosine Administration in Compensatory Tachycardia: A Case Report

Compensatory tachycardia, an increased heart rate responding to stressors, requires careful consideration in treatment. This case report outlines a scenario where emergency medical services (EMS) misinterpreted a patient's electrocardiogram (EKG) as paroxysmal supraventricular tachycardia (PSVT) and administered adenosine, resulting in sudden cardiac arrest. Despite the rarity of deaths post-adenosine, this case highlights the potential risks of its use in inappropriate clinical scenarios. The patient, later diagnosed with a pulmonary embolism, had a compensatory heart rate that was disrupted after adenosine administration. While adenosine remains a safe and effective treatment for PSVT, this case report serves as a warning to EMS systems about the risks associated with its increased misuse, especially given the trends of prehospital EKG misinterpretation.

Low-voltage electrical injuries and the electrocardiogram: is a 'normal' electrocardiogram sufficient for safe discharge from care? A systematic review

Introduction

The current Joint Royal Colleges Ambulance Liaison Committee guidelines in the United Kingdom provide clear national guidance for low-voltage electrical injury patients. While patients can be considered safe to discharge with an apparently 'normal' initial electrocardiogram (ECG), some evidence questions the safety profile of these patients with a risk of a 'delayed arrhythmia'. This review aims to examine this as well as identifying the frequency and common arrhythmias that require patients to be conveyed to hospital for further monitoring post electrical injury. It will also aim to improve the understanding of potentially clinically significant arrhythmias that may require clinical intervention or even admission within an in-hospital environment.

Methods

A systematic review using three electronic databases (CINAHL, MEDLINE, AMED) was conducted in January 2022. A preferred reporting items for systematic reviews and meta-analyses (PRISMA) approach was used to identify relevant studies with a suitable quality to support a critical review of the topic. A modified Critical Appraisal Skills Programme quality assessment checklist was used across suitable studies and a descriptive statistics approach was adopted to present the findings.

Results

Seven studies, largely retrospective reviews, met the inclusion criteria. The findings showed 26% of patients had an arrhythmia on initial presentation (n = 364/1234) with incidences of sinus tachycardia, sinus bradycardia and premature ventricular contractions. However, making definitive statements is challenging due to the lack of access to individual patients' past ECGs. Within these arrhythmias' ST segment changes, atrial fibrillation and long QT syndrome could be considered potentially significant, however associated prognosis with these and electrical injuries is unknown. Only six (0.5%) patients required treatment by drug therapy, and a further three died from associated complications. Most patients with a normal ECG were discharged immediately with only a limited follow-up. No presentation of a 'delayed arrhythmia' was identified throughout the studies.

Conclusion

The data for low-voltage electrical injuries are limited, but the potential arrhythmias for this patient group seldom require intervention. The entity of the 'delayed arrhythmia' may not be a reason to admit or monitor patients for prolonged periods. Further studies should consider the safety profile of discharging a patient with a normal ECG.

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Inappropriate sinus tachycardia: an examination of existing definitions

Aims

Inappropriate sinus tachycardia (IST) is a syndrome characterized by an elevated sinus rate unassociated with known physiological, pathological, or pharmacological causes. Despite published consensus documents, IST definitions appear to vary in the literature. In this study, we reviewed IST publications to evaluate IST definition variability and ascertain the degree to which consensus definitions are being adopted.

Methods and results

English-language articles in PubMed, Ovid MEDLINE, Ovid Embase, and Google Scholar published from 1 January 1970 to 1 June 2021 with the title terms ‘inappropriate sinus tachycardia,’ ‘non-paroxysmal sinus tachycardia,’ or ‘permanent sinus tachycardia’ were searched. In each, the IST definition used, qualifying characteristics, and publications cited to support each definition were recorded. We identified 138 publications meeting the search criteria. Inappropriate sinus tachycardia definitions were provided in 114 of 138 articles (83%). A majority of definitions (92/114, 81%) used distinct heart rate (HR) thresholds. Among these, the most common threshold was ≥100 beats per minute (BPM) (75/92, 82%), mainly measured at rest (54/92, 59%). Most definitions (47/92, 51%) included a second criterion to qualify for IST; these were most often an HR threshold of 90 BPM measured over 24 h by ambulatory electrocardiogram (37/47, 79%). Diagnosis of exclusion was a common criterion (75/92, 82%) but symptom status was not (41/92, 45%). The 2015 Heart Rhythm Society IST consensus was commonly cited but adopted in only 37% of definitions published after 2015.

Conclusions

Inappropriate sinus tachycardia definitions in current literature are inconsistent, and professional society consensus IST definitions have, to date, had limited impact.

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Metered-dose inhalers versus nebulization for the delivery of albuterol for acute exacerbations of wheezing or asthma in children: A systematic review with meta-analysis

OBJECTIVES

The benefits of metered-dose inhalers with a spacer (MDI+S) have increasingly been recognized as an alternative method of albuterol administration for treating pediatric asthma exacerbations. The aim of this systematic review was to compare the response to albuterol delivered through nebulization (NEB) with albuterol delivered through MDI+S in pediatric patients with asthma exacerbations.

METHODS

We conducted an electronic search in MEDLINE/PubMed, EMBASE, Ovid, and ClinicalTrials. To be included in the review, a study had to a randomized clinical trial comparing albuterol delivered via NEB versus MDI+S; and had to report the rate of hospital admission (primary outcome), or any of the following secondary outcomes: oxygen arterial saturation, heart rate (HR), respiratory rate (RR), the pulmonary index score (PIS), adverse effects, and need for additional treatment.

RESULTS

Fifteen studies (n = 2057) met inclusion criteria. No significant differences were found between the two albuterol delivery methods in terms of hospital admission (relative risk, 0.89; 95% confidence interval [CI], 0.55-1.46; I²  = 32%; p = .65). There was a significant reduction in the PIS score (mean difference [MD], -0.63; 95% CI, -0.91 to -0.35; I²  = 0%; p < .00001), and a significantly smaller increase in HR (better; MD -6.47; 95% CI, -11.69 to -1.25; I²  = 0%; p = .02) when albuterol was delivered through MDI+S than when it was delivered through NEB.

CONCLUSIONS

This review, an update of a previously-published meta-analysis, showed a significant reduction in the PIS and a significantly smaller increase in HR when albuterol was delivered through MDI+S than when it was delivered through NEB.

Retrospective study of prognosis and relating factors of cardiac complications associated with electrical injuries at a single centre in Korea

OBJECTIVES

To date, no research has investigated the association between cardiac complication and electrical injury; hence, we aimed to assess the consequences and relating factors of cardiac complications from electrical injuries in South Korea.

DESIGN

Retrospective single-centre study.

PARTICIPANTS

721 patients who had electrical injury-related admission during 2007-2017. An electronic medical record system was used to extract records of patients admitted for electrical injury treatment.

RESULTS

Cardiac complications included abnormal parameters of myocardial damage, abnormal regional wall motion detected via echocardiogram, dysrhythmia (eg, bradycardia, atrial flutter/fibrillation) and ventricular tachycardia or fibrillation. Overall, 107 patients (14.8%) experienced cardiac complications. The average admission duration and intensive care unit stay duration were significantly longer in patients with cardiac complications than in those without them (75.0±45.3 vs 56.6±48.0 days and 19.3±24.1 vs 10.4±15.5 days, respectively, p<0.01 for both). Of the total cardiac cases, 72.9% had Troponin I elevation, 3.7% had regional wall motion abnormality, and 5.6% had atrial flutter/fibrillation. Overall, seven patients from the cardiac complication group and three patients from the control group died (p=0.01). All deaths occurred within 32 days, and the most common cause of death was septic shock. Total body surface area (TBSA) was only positively related factor to cardiac complications.

CONCLUSION

This study is the first in South Korea to reveal that electrical accident patients with cardiac complications experience poorer in-hospital prognosis, and TBSA was the only risk factor of cardiac complications. And initial treatment for infection and inflammations could be important in electrical injury.

Simulation of Cardiac Arrhythmias Using a 2D Heterogeneous Whole Heart Model

Simulation studies of cardiac arrhythmias at the whole heart level with electrocardiogram (ECG) gives an understanding of how the underlying cell and tissue level changes manifest as rhythm disturbances in the ECG. We present a 2D whole heart model (WHM2D) which can accommodate variations at the cellular level and can generate the ECG waveform. It is shown that, by varying cellular-level parameters like the gap junction conductance (GJC), excitability, action potential duration (APD) and frequency of oscillations of the auto-rhythmic cell in WHM2D a large variety of cardiac arrhythmias can be generated including sinus tachycardia, sinus bradycardia, sinus arrhythmia, sinus pause, junctional rhythm, Wolf Parkinson White syndrome and all types of AV conduction blocks. WHM2D includes key components of the electrical conduction system of the heart like the SA (Sino atrial) node cells, fast conducting intranodal pathways, slow conducting atriovenctricular (AV) node, bundle of His cells, Purkinje network, atrial, and ventricular myocardial cells. SA nodal cells, AV nodal cells, bundle of His cells, and Purkinje cells are represented by the Fitzhugh-Nagumo (FN) model which is a reduced model of the Hodgkin-Huxley neuron model. The atrial and ventricular myocardial cells are modeled by the Aliev-Panfilov (AP) two-variable model proposed for cardiac excitation. WHM2D can prove to be a valuable clinical tool for understanding cardiac arrhythmias.

Autonomic nervous system interaction with the cardiovascular system during exercise

There is considerable recent evidence that parameters thought to reflect the complex interaction between the autonomic nervous system and the cardiovascular system during exercise testing can provide significant prognostic information. Specific variables of great importance include heart rate (HR) response to exercise (reserve), HR recovery after exercise, and multiple components of HR variability both at rest and with exercise. Poor HR response to exercise has been strongly associated with sudden cardiac death and HR recovery from a standard exercise test has been shown to be predictive of mortality. In addition, there are limited studies evaluating the components of HR variability at rest and during exercise and their prognostic significance. Research continues seeking to refine these exercise measurements and further define their prognostic value. Future findings should augment the power of the exercise test in risk-stratifying cardiovascular patients.