Arrhythmias Occurring in Children during HEMS Intervention: A Retrospective Cohort Study

Background Arrhythmias in patients during medical transport remain a challenge for medical personnel. Helicopter emergency medical service (HEMS) crews, as the only medical rescue teams in Poland to conduct rescue flights, keep detailed documentation of monitoring vital functions over short time intervals during the flight. Aims The aim of this study was to determine the characteristics of cardiac arrhythmia in pediatric patients (up to 12 years of age) transported by HEMS operatives, considering life-threatening rhythms and those that occur during out-of-hospital cardiac arrest (OHCA). Methods The analysis of HEMS medical documentation covered 90345 missions carried out from 2011 to 2020. Among all activations, 820 cases of arrhythmias in pediatric patients up to 12 years of age were extracted. Results Missions for males accounted for 60% of all activations (n = 492), while flights for females accounted for 40% (n = 328). A statistically significant relationship between the number of HEMS flights and the season was demonstrated (p = 0.015). During the study period, pediatric patients mostly experienced cardiac arrhythmias in the form of supraventricular tachycardia (sVT) (n = 504). Asystole (n = 178) and pulseless electrical activity (PEA) (n = 52) ranked second and third in terms of occurrence, respectively. A statistically significant relationship between the type of heart rhythm disorder and age was demonstrated (p < 0.05). Conclusions Heart rhythm disorders most often affected children between 0 and 3 years of age. As the patient's age increased, the incidence of arrhythmias decreased. Among pediatric patients, supraventricular tachycardia proved to be the predominant arrhythmia during the study period.


Introduction
Heart rhythm disorders are increasingly being detected in newborns, children, and adolescents, as new and more accurate methods of diagnosing abnormalities in the electrical function of the heart in pediatric patients become available.Arrhythmias may be asymptomatic, but in some cases, they cause serious life-and health-threatening consequences [1].However, diagnostic and therapeutic options are limited in prehospital conditions, including the emergency care system.During medical rescues, the implementation of rapid treatment and the mitigation of negative consequences resulting from cardiovascular malfunctions are major challenges for medical personnel [2].
Among emergency medical teams, utilizing helicopter emergency medical services (HEMS) is the fastest option for transporting a patient to a medical facility.A HEMS crew in Poland consists of at least one professional pilot, a paramedic or nurse, and a doctor.Te main tasks carried out by HEMS include the performance of medical rescue activities at the scene of the event and air ambulance transport to and between medical facilities [3].
Additionally, only HEMS crews use the National Advisory Committee for Aeronautics (NACA) score, which is a 7-point assessment of the patient's general condition.Tere are studies confrming the score's usefulness in transport carried out by HEMS [4,5].Based on the score, the patient's condition can be classifed as severe (NACA 4), very severe (NACA 5-6), or moderate (NACA 3), and a decision can be made on which patients require immediate medical operations.Te HEMS crew assesses the patient's condition using the NACA score to see if the patient is eligible for helicopter transport and whether there are no absolute contraindications (NACA 6-OHCA and NACA 7-death).Properly carried out classifcation of the patient leads to appropriate preparation for the mission, during which the crew needs to deal with a patient in severe or even critical condition and thus reduce the possibility of unwanted situations occurring during air transport.During the intervention, medical staf tries to ensure the presence and active participation of the child's guardian in rescue activities.
Te assessment of a patient with suspected arrhythmias includes a thorough family history and history and physical examination, followed by diagnostic testing.A 12-and/or 15-lead electrocardiogram, echocardiogram, exercise test, and home or ambulatory cardiac monitoring should be performed [10].Unfortunately, in prehospital conditions, the diagnostic possibilities are signifcantly limited.
Te Independent Public Health Care Air Ambulance Institution was established in 2000.Te change in the name of the entity to "Polish Medical Air Rescue (PMAR)" occurred in 2016 as a result of the order of the Minister of Health on 9 November regarding the change of the name of the PMAR, which also granted it a statute [11,12].Te current location of bases in Poland is shown in Figure 1.PMAR is a medical entity that aims to reach a patient in an emergency more quickly and to transport the patient to a hospital with an appropriate level of care.Te role of HEMS in Poland, both in the urban agglomeration and in the countryside, has been confrmed by research [13][14][15][16][17][18].
Tere are insufcient data in the literature to characterize cardiac arrhythmias in prehospital pediatric patients.Teir identifcation could improve the classifcation of health risks depending on age and type of event.Te main objective of the authors of this study was to determine the types of cardiac arrhythmias in pediatric patients up to 12 years of age who received assistance from HEMS.

Methods
Tis retrospective study was carried out based on data provided by HEMS in Warsaw (Ksie ˛życowa 5, 01-934 Warsaw), taking into account medical documentation from the period 2011-2020.A group of 820 patients up to 12 years of age with cardiac arrhythmias was selected for this study from the total number of patients and the total number of missions among 90345 fights (Figure 2).Data on HEMS scene fights were analyzed.Data on the place of the event and the date were also analyzed.(1) A statement that the time of reaching the scene of an emergency medical team other than an air medical rescue team is longer than that of an HEMS (2) When the time of transport of a person in a state of emergency by air from the scene of the event to a hospital emergency department or trauma center is shorter than the time of transport by emergency medical teams other than HEMS and may bring benefts in the further treatment process (3) When, in the opinion of the dispatcher, it is necessary

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Te HEMS team's readiness time depends on the time of day and night.Te teams' response times are closely monitored by the navigation system: (a) Time ready to take of during the day: (i) Within 60 km from base: until 3 minutes (ii) Within a radius of more than 60 km to 130 km from base: until 6 minutes (iii) Within a radius of more than 130 km from base: until 15 minutes (b) Time ready to take of at night: (i) Within a radius of 60 km from base: until 15 minutes; (ii) Within a radius of more than 60 km from base: until 30 minutes.

Statistical Analysis.
Data obtained in the process of documentation analysis were subjected to statistical analysis, which was performed using the STATISTICA program version 13.2 (Tibco Software Inc., Palo Alto, CA, United States).In the description of quantitative data, the means (M) and standard deviations (SDs) were used, and in the case of qualitative data, numbers (N) and percentages (%) were used.Te Kolmogorov-Smirnov and Lilliefors tests were used to verify the normality of the distribution of quantitative variables.Te chisquared test was used to assess signifcant diferences between the analyzed qualitative variables.A nonparametric Kruskal-Wallis test was used to investigate diferences between more than two groups.Te results were considered statistically signifcant at p < 0.05.4.

Heart Rhythm Disorders.
In the study period, pediatric patients most commonly experienced cardiac arrhythmias in the form of supraventricular tachycardia (sVT) (n � 504).Te least common heart rhythm disorder in children was atrioventricular (AV) block (n � 11).A detailed analysis of cardiac arrhythmias broken down by year is presented in Table 2.
Te highest number of deaths occurred among pediatric patients under 1 year of age (n � 86 cases).However, the lowest number of deaths was recorded in the 4-6 age group (n � 16 cases).Te conducted statistical analysis revealed a signifcant diference in mortality between infants under 1 year of age and children aged 1-3 years (31.2% vs 6.4%), as well as children aged 4-6 years (31.2% vs 15.5%).Figure 6 presents a detailed analysis of the number of deaths with regard to a patient's age.Asystole was diagnosed most often in the age group below 1 year, which may be related to the mortality rate.

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During the OHCA, asystole (n � 178) and pulseless electrical activity (PEA) (n � 52) ranked frst and second in terms of number, respectively (Table 3).Te conducted statistical analysis revealed signifcant diferences in the NACA scale values depending on the presence of cardiac rhythm disturbances (p < 0.05).Higher NACA scale values

Medical Emergency Procedures.
Depending on the patient's condition, the HEMS teams implemented specifc medical rescue activities.In 271 cases, patients were sedated.
In 587 patients, airway suctioning was necessary, followed by endotracheal intubation in 351 of all patients, and mechanical ventilation in 284 cases.Muscle relaxation was used in 108 patients, chest compressions were used in 258 children, and defbrillation was used in 35 patients (Table 4).

Discussion
Cardiac arrhythmias may occur in both adults and children.
Te correct heart rate depends on a person's age.For example, in newborns, the heart rate should be in the range of 120-160/minute, while in children aged 2 to 10, the norm is 60-110/minute, and in children over 10 years of age and adults, the norm is considered to be 60-100/minute.Te pulse depends on the state of stimulation of a person; during sleep, it is lower, while during wakefulness, it is the highest [19].
Bradycardia means a slow heart rate, that is, a heart rate below normal with regard to the normal value depending on age.Te main symptoms of bradycardia are apathy, dizziness, fainting, and drowsiness.Treatment of a child with a diagnosis of bradycardia most often involves pharmacotherapy or implantation of a pacemaker [20].Tachycardia, on the other hand, concerns an excessively rapid heart rate.Te main symptoms of tachycardia are palpitations, dizziness, and rapid breathing.Treatment of tachycardia depends on the clinical condition of the child and the type of tachyarrhythmia.Te following fve elements should be noted in the ERCsuggested pediatric cardiovascular screening regimen: (1) Heart rate (2) Blood pressure (3) Pulse amplitude (4) Peripheral perfusion (capillary refll, skin color and temperature, and peripheral pulse defcit) (5) Preload (jugular veins, liver, and lungs).
Heart rate is a very important part of evaluating a baby.Terefore, it should be monitored continuously and reliably.Te measurement of saturation alone with a pulse oximeter may be insufcient; frst, because pulse oximetry is a method whose measurement can be quite easily disturbed, and second, the measurement result, averaged over a period of several seconds, reacts with a relatively large inertia.Terefore, children should always be monitored with both ECG and SpO 2 .In young children, mainly neonates and infants, refex  6 Emergency Medicine International bradycardia occurs in response to hypoxia.In such a situation, the frst action to be taken is to quickly oxygenate the child.Te increase in oxygen saturation usually restores normal heart function quickly and does not require medication.On the other hand, a delay in improving ventilation caused, for example, by the preparation and administration of drugs, may lead to cardiac arrest.It should be remembered that in children, HR < 60/min, without signs of circulation, is treated as SCA.When helping a child, if possible, it is necessary to obtain as much information as possible at the scene of the incident, which may be helpful in the further treatment process.A checklist can help you to collect all data efciently and comprehensively.Sometimes arrhythmias in children are asymptomatic and are detected accidentally, e.g., during a check-up [21].Risk factors for arrhythmia include conditions such as fever, dehydration, infections, and infammation [22].
For the purposes of this study, an attempt was made to analyze cardiac arrhythmias in pediatric patients up to 12 years of age who were HEMS patients.An increase in the number of interventions in the studied category of patients over the years (2011 � 38 vs. 2019 � 125) was observed.Tis may be due to the decision to create more bases where HEMS crew duty is 24 hours a day, as well as to an increase in the overall number of calls over the years.Te number of fights operated by HEMS depended on the season.Many more fights were made in the summer than in the winter (summer � 322 vs. winter � 131).Tis may be due to the diference in weather conditions, the lack of a safe landing site, and the earlier nightfall in winter.
Te number of patients qualifed for transport by HEMS crews accounted for 619 people (75.5%).However, 201 patients did not qualify for transport.Tis may be due to the lack of indications for urgent air transport or failure to meet requirements (e.g., a patient currently experiencing cardiac arrest or with low chances of survival of air transport).Te most common arrhythmia in pediatric patients was supraventricular tachycardia (n � 504), while children with AV block were the least reported (n � 11).Te obtained results are confrmed by the study by Sacchetti et al. and the description of Jan KR et al., where the causes of ER sVT most commonly include tissue hypoxia, hypovolemia, fever, metabolic stress, trauma, pain, anxiety, toxins, anemia, and   [23,24].Te presence of tachycardia is sometimes adaptive to changing conditions inside or outside the body and is not always a consequence of heart disease (i.e., it may be a result of shock with diferent etiologies).Te obtained results show a signifcant diference in the frequency of adenosine use compared to atropine (n � 4 vs. n � 80).It should be assumed that bradycardia in children is interpreted by HEMS doctors as an arrhythmia that poses a greater threat than accelerated heart rate.Tachycardia may manifest with regular or irregular heartbeat.Te occurrence of tachyarrhythmia leads to a deterioration of hemodynamic performance and hypoxia of organs and tissues.sVT in some patients may present only with palpitations, while in others, there may be severe symptoms of tachycardia requiring rapid and intensive treatment and hospitalization.sVT is usually characterized in the ECG by a sudden onset and equally rapid end, a constant R-R interval, and abnormal P waves.When interviewing the legal guardians or parents of a child, it is often impossible to detect the cause, except for a previously experienced episode of sVT [25].Te next arrhythmias in terms of frequency of occurrence were asystole (n = 178) and PEA (n = 52).In pediatric patients, cardiac arrest occurs much more frequently when presenting asystole or PEA than when presenting VF/pVT.Tis was confrmed by the results of the work by Nordseth et al., which was carried out over 2006-2013 in a pediatric hospital in Philadelphia [26].Te study group consisted of 74 pediatric patients diagnosed with cardiac arrest.Te study showed that 38.0% of patients had cardiac arrest presenting PEA and 16.0% presented asystole.Rhythms appropriate for defbrillation were observed only in 24.0% of the total cases.Such a low percentage of rhythms for defbrillation during resuscitation may result from the fact that in most children, cardiac arrest occurs in the respiratory mechanism or due to generalized body failure.On the other hand, cardiac arrest resulting from circulatory failure in children without congenital heart defects or cardiovascular diseases is rare.Te most frequent cardiac arrhythmias were observed in children less than 1 year of age (n = 164; 28.4% of total arrhythmias in children).Te incidence of arrhythmias decreased with the age of the child.Sholokhova et al.showed that 60.0% of traumatic events among children occur among males [27].Te authors point out the dependence shown in the description of the patient's profle.Te study group consisted of exactly 60.0% of male pediatric patients.In turn, the most common reason for HEMS calls were injuries (n = 249; 30.4%).Terefore, more frequent arrhythmias in males could be related to injuries sufered by children.Tis aspect requires further research.
Te highest number of deaths occurred among pediatric patients younger than 1 year of age (n � 86).Such a high percentage of deaths may result from poorly developed organs and systems.Risk factors for early death include respiratory distress and respiratory failure, as the respiratory process of newborns and infants occurs only through the nose.Terefore, even a runny nose or a child being placed in an incorrect position to sleep can lead to respiratory arrest [28,29].

Limitations of Tis Study.
Te authors see the need to conduct further studies on a larger group of children.Te medical documentation analyzed retrospectively came only from the air ambulance base in Poland.Tere are no known outcomes for hospitalized patients or results of studies that could indicate the causes of cardiac arrhythmias.Te authors performed a cross-sectional analysis of pathological ECG records of various etiologies, including rhythms associated with sudden cardiac arrest.Te characteristics of prehospital emergency procedures do not allow for the indication of the causes of arrhythmias each time.Te years 2021 and 2022 were not included in the study due to the confounding factor caused by the COVID-19 pandemic [28,30].Te study does not include other medical procedures due to space limitations and the main topic of the study.Te HEMS doctor's documentation is completed manually and then transcribed into a digital database.Tis may result in incomplete or illegible data in cards that are difcult for the administrator to read.

Conclusions
Te number of diagnosed cardiac arrhythmias in pediatric patients (up to 12 years of age) shows an upward trend in the last 10 years.Te highest risk of death was found among children less than 1 year of age.Among patients with sudden cardiac arrest, the dominant ECG record was asystole, which potentially determines a worse prognosis.Only 12 patients (5.0%) of SCA-related rhythms presented with ventricular disturbances that were an indication for external defbrillation.Te authors confrmed that nonshockable rhythms are statistically signifcantly more frequent during SCA in children.
Taking into account arrhythmias that may potentially require intervention in prehospital conditions (ventricular tachycardia, atrial fbrillation/atrial futter, and AV block), their number is not signifcant (n � 35).Supraventricular tachycardia and bradycardia disorders may be secondary to the primary cause in pediatric patients (e.g., hypoxia and hypovolemia).
(i) Characterization of the HEMS mission to pediatric patients (ii) Determination of cardiac arrhythmias in children, including cases of sudden cardiac arrest (iii) Analysis of pharmacological treatment in HEMS conditions

Figure 2 :
Figure 2: Selection of the study group according to PRISMA fow diagram.

Figure 3 :
Figure 3: HEMS missions to pediatric patients with signifcant cardiac arrhythmias by year.

Figure 4 :Figure 5 :
Figure 4: Division of patients according to age and sex.

Figure 6 :
Figure 6: Number of deaths recorded in each age group.

Figure 7 :
Figure 7: Correlation of the NACA score with cardiac arrhythmias.
[17]lation of the Minister of Health) of August 19, 2019, on framework procedures for handling emergency notifcations and notifcations about events by a medical dispatcher is as follows[17]: g., based on the PAT triangle (Pediatric Assessment Triangle 2020 American Heart Association).HEMS in Poland bases its procedures on the guidelines of the European Resuscitation Council.Children are a group of patients who require special attention due to anatomical, physiological, procedural, and legal specifcities.Examination and necessary therapeutic interventions should be performed in accordance with the current recommendations of the European Resuscitation Council (ERC) in the feld of PALS.Legal basis for disposing of air medical rescue teams (

Table 1 :
Division of fights considering the time of year and the place of the event.
Bold value indicates its statistical signifcance.

Table 2 :
Type of heart rhythm disorder broken down by the age of patient (excluding OHCA).

Table 4 :
Medical emergency procedures implemented by age of patient.