Diagnosis of Acute Aortic Syndrome in the Emergency Department (DAShED) study: an observational cohort study of people attending the emergency department with symptoms consistent with acute aortic syndrome.

BACKGROUND: The diagnosis of acute aortic syndrome (AAS) is commonly delayed or missed in the ED. We describe characteristics of ED attendances with symptoms potentially associated with AAS, diagnostic performance of clinical decision tools (CDTs) and physicians and yield of CT aorta angiogram (CTA). METHODS: This was a multicentre observational cohort study of adults attending 27 UK EDs between 26 September 2022 and 30 November 2022, with potential AAS symptoms: chest, back or abdominal pain, syncope or symptoms related to malperfusion. Patients were preferably identified prospectively, but retrospective recruitment was also permitted. Anonymised, routinely collected patient data including components of CDTs, was abstracted. Clinicians treating prospectively identified patients were asked to record their perceived likelihood of AAS, prior to any confirmatory testing. Reference standard was radiological or operative confirmation of AAS. 30-day electronic patient record follow-up evaluated whether a subsequent diagnosis of AAS had been made and mortality. RESULTS: 5548 patients presented, with a median age of 55 years (IQR 37-72; n=5539). 14 (0.3%; n=5353) had confirmed AAS. 10/1046 (1.0%) patients in whom the ED clinician thought AAS was possible had AAS. 5/147 (3.4%) patients in whom AAS was considered the most likely diagnosis had AAS. 2/3319 (0.06%) patients in whom AAS was considered not possible did have AAS. 540 (10%; n=5446) patients underwent CT, of which 407 were CTA (7%). 30-day follow-up did not reveal any missed AAS diagnoses. AUROC (area under the receiver operating characteristic) curve for ED clinician AAS likelihood rating was 0.958 (95% CI 0.933 to 0.983, n=4006) and for individual CDTs were: Aortic Dissection Detection Risk Score (ADD-RS) 0.674 (95% CI 0.508 to 0.839, n=4989), AORTAs 0.689 (95% CI 0.527 to 0.852, n=5132), Canadian 0.818 (95% CI 0.686 to 0.951, n=5180) and Sheffield 0.628 (95% CI 0.467 to 0.788, n=5092). CONCLUSION: Only 0.3% of patients presenting with potential AAS symptoms had AAS but 7% underwent CTA. CDTs incorporating clinician gestalt appear to be most promising, but further prospective work is needed, including evaluation of the role of D-dimer. TRIAL REGISTRATION NUMBER: NCT05582967; NCT05582967.

Pulmonary embolism management in the emergency department: part 2.

Pulmonary embolism (PE) can present with a range of severity. Prognostic risk stratification is important for efficacious and safe management. This second of two review articles discusses the management of high-, intermediate- and low-risk PE. We discuss strategies to identify patients suitable for urgent outpatient care in addition to identification of patients who would benefit from thrombolysis. We discuss specific subgroups of patients where optimal treatment differs from the usual approach and identify emerging management paradigms exploring new therapies and subgroups.

Clinical Diagnosis and Magnetic Resonance Imaging in Patients With Transient and Minor Neurological Symptoms: A Prospective Cohort Study.

BACKGROUND: The utility of magnetic resonance imaging (MRI) brain in patients with transient or minor neurological symptoms is uncertain. We sought to determine the proportion of participants with transient or minor neurological symptoms who had MRI evidence of acute ischemia at different clinical probabilities of transient ischemic attack (TIA) or minor stroke. METHODS: Cohort of participants with transient or minor neurological symptoms from emergency and outpatient settings. Clinicians at different levels of training gave each participant a diagnostic probability (probable when TIA/stroke was the most likely differential diagnosis; possible when TIA/stroke was not the most likely differential diagnosis; or uncertain when diagnostic probability could not be given) before 1.5 or 3T brain MRI ≤5 days from onset. Post hoc, each clinical syndrome was defined blind to MRI findings as National Institute of Neurological Disorders and Stroke criteria TIA/stroke; International Headache Society criteria migraine aura; non-TIA focal symptoms; or nonfocal symptoms. MRI evidence of acute ischemia was defined by 2 reads of MRI. Stroke was ascertained for at least 90 days and up to 18 months after recruitment. RESULTS: Two hundred seventy-two participated (47% female, mean age 60, SD 14), 58% with MRI ≤2 days of onset. Most (92%) reported focal symptoms. MR evidence of acute ischemia was found, for stroke/TIA clinical probabilities of probable 23 out of 75 (31% [95% CI, 21%-42%]); possible 26 out of 151 (17% [12%-24%]); and uncertain 9 out of 43, (20% [10%-36%]). MRI evidence of acute ischemia was found in National Institute of Neurological Disorders and Stroke criteria TIA/stroke 40 out of 95 (42% [32%-53%]); migraine aura 4 out of 38 (11% [3%-25%]); non-TIA focal symptoms 16 out of 99 (16% [10%-25%]); and no focal features 1 out of 29 (3% [0%-18%]). After MRI, a further 14 (5% [95% CI, 3-8]) would be treated with an antiplatelet drug compared with treatment plan before MRI. By 18 months, a new ischemic stroke occurred in 9 out of 61 (18%) patients with MRI evidence of acute ischemia and 2 out of 211 (1%) without (age-adjusted hazard ratio, 13 [95% CI, 3-62]; P<0.0001). CONCLUSIONS: MRI evidence of acute brain ischemia was found in about 1 in 6 transient or minor neurological symptoms patients with a nonstroke/TIA initial diagnosis or uncertain diagnosis. Methods to determine the clinical and cost-effectiveness of MRI are needed in this population.

Establishing a Smartphone Ambulatory ECG Service for Patients Presenting to the Emergency Department with Pre-Syncope and Palpitations.

Background and Objectives: The Investigation of Palpitations in the ED (IPED) study showed that a smartphone-based event recorder increased the number of patients in whom an electrocardiogram (ECG) was captured during symptoms over five-fold to more than 55% at 90 days compared to standard care and concluded that this safe, non-invasive and easy-to-use device should be considered part of on-going care to all patients presenting acutely with unexplained palpitations or pre-syncope. This study reports the process of establishing a smartphone palpitation and pre-syncope ambulatory care Clinic (SPACC) service. Materials and Methods: A clinical standard operating procedure (SOP) was devised, and funding was secured through a business case for the purchase of 40 AliveCor devices in the first instance. The clinic was launched on 22 July 2019. Results: Between 22 July 2019 and 31 October 2019, 68 patients seen in the emergency departments (EDs) with palpitations or pre-syncope were referred to SPACC. Of those, 30 were male and 38 were female, and the mean age was 45.8 years old (SD 15.1) with a range from 18 years old to 80 years old. A total of 50 (74%) patients underwent full investigation. On the first assessment, seven (10%) patients were deemed to have non-cardiac palpitations and were not fitted with the device. All patients who underwent full investigation achieved symptomatic rhythm correlation most with sinus rhythm, ventricular ectopics, or bigeminy. A symptomatic cardiac dysrhythmia was detected in six (8.8%) patients. Three patients had supraventricular tachycardia (4%), two had atrial fibrillation (3%), and one had atrial flutter (2%). Qualitative feedback from the SPACC team suggested several areas where improvement to the clinic could be made. Conclusion: We believe a smartphone palpitation service based on ambulatory care is simple to implement and is effective at detecting cardiac dysrhythmia in ED palpitation patients.

Syncope Time Frames for Adverse Events after Emergency Department Presentation: An Individual Patient Data Meta-Analysis.

Background and Objectives: Knowledge of the incidence and time frames of the adverse events of patients presenting syncope at the ED is essential for developing effective management strategies. The aim of the present study was to perform a meta-analysis of the incidence and time frames of adverse events of syncope patients. Materials and Methods: We combined individual patients' data from prospective observational studies including adult patients who presented syncope at the ED. We assessed the pooled rate of adverse events at 24 h, 72 h, 7-10 days, 1 month and 1 year after ED evaluation. Results: We included nine studies that enrolled 12,269 patients. The mean age varied between 53 and 73 years, with 42% to 57% females. The pooled rate of adverse events was 5.1% (95% CI 3.4% to 7.7%) at 24 h, 7.0% (95% CI 4.9% to 9.9%) at 72 h, 8.4% (95% CI 6.2% to 11.3%) at 7-10 days, 10.3% (95% CI 7.8% to 13.3%) at 1 month and 21.3% (95% CI 15.8% to 28.0%) at 1 year. The pooled death rate was 0.2% (95% CI 0.1% to 0.5%) at 24 h, 0.3% (95% CI 0.1% to 0.7%) at 72 h, 0.5% (95% CI 0.3% to 0.9%) at 7-10 days, 1% (95% CI 0.6% to 1.7%) at 1 month and 5.9% (95% CI 4.5% to 7.7%) at 1 year. The most common adverse event was arrhythmia, for which its rate was 3.1% (95% CI 2.0% to 4.9%) at 24 h, 4.8% (95% CI 3.5% to 6.7%) at 72 h, 5.8% (95% CI 4.2% to 7.9%) at 7-10 days, 6.9% (95% CI 5.3% to 9.1%) at 1 month and 9.9% (95% CI 5.5% to 17) at 1 year. Ventricular arrhythmia was rare. Conclusions: The risk of death or life-threatening adverse event is rare in patients presenting syncope at the ED. The most common adverse events are brady and supraventricular arrhythmias, which occur during the first 3 days. Prolonged ECG monitoring in the ED in a short stay unit with ECG monitoring facilities may, therefore, be beneficial.

Early fibrinogen concentrate therapy for major haemorrhage in trauma (E-FIT 1): results from a UK multi-centre, randomised, double blind, placebo-controlled pilot trial.

BACKGROUND: There is increasing interest in the timely administration of concentrated sources of fibrinogen to patients with major traumatic bleeding. Following evaluation of early cryoprecipitate in the CRYOSTAT 1 trial, we explored the use of fibrinogen concentrate, which may have advantages of more rapid administration in acute haemorrhage. The aims of this pragmatic study were to assess the feasibility of fibrinogen concentrate administration within 45 minutes of hospital admission and to quantify efficacy in maintaining fibrinogen levels ≥ 2 g/L during active haemorrhage. METHODS: We conducted a blinded, randomised, placebo-controlled trial at five UK major trauma centres with adult trauma patients with active bleeding who required activation of the major haemorrhage protocol. Participants were randomised to standard major haemorrhage therapy plus 6 g of fibrinogen concentrate or placebo. RESULTS: Twenty-seven of 39 participants (69%; 95% CI, 52-83%) across both arms received the study intervention within 45 minutes of admission. There was some evidence of a difference in the proportion of participants with fibrinogen levels ≥ 2 g/L between arms (p = 0.10). Fibrinogen levels in the fibrinogen concentrate (FgC) arm rose by a mean of 0.9 g/L (SD, 0.5) compared with a reduction of 0.2 g/L (SD, 0.5) in the placebo arm and were significantly higher in the FgC arm (p < 0.0001) at 2 hours. Fibrinogen levels were not different at day 7. Transfusion use and thromboembolic events were similar between arms. All-cause mortality at 28 days was 35.5% (95% CI, 23.8-50.8%) overall, with no difference between arms. CONCLUSIONS: In this trial, early delivery of fibrinogen concentrate within 45 minutes of admission was not feasible. Although evidence points to a key role for fibrinogen in the treatment of major bleeding, researchers need to recognise the challenges of timely delivery in the emergency setting. Future studies must explore barriers to rapid fibrinogen therapy, focusing on methods to reduce time to randomisation, using 'off-the-shelf' fibrinogen therapies (such as extended shelf-life cryoprecipitate held in the emergency department or fibrinogen concentrates with very rapid reconstitution times) and limiting the need for coagulation test-based transfusion triggers. TRIAL REGISTRATION: ISRCTN67540073 . Registered on 5 August 2015.

Diagnostic yield of an ambulatory patch monitor in patients with unexplained syncope after initial evaluation in the emergency department: the PATCH-ED study.

OBJECTIVES: Diagnosing underlying arrhythmia in ED syncope patients remains problematic. This study investigates diagnostic yield, event prevalence, patient satisfaction and compliance, and influence on resource utilisation of an ambulatory patch monitor in unexplained ED syncope patients. METHODS: Prospective pilot study conducted in a single tertiary ED in Scotland between 17 November 2015 and 16 June 2017 with a historical unmatched comparator group. Patients 16 years or over presenting within 6 hours of unexplained syncope were fitted in the ED with an ambulatory patch ECG recorder (Zio XT monitor), which continuously records a single-lead ECG for up to 14 days. Patients with an obvious underlying cause were excluded. An unmatched historical group of 603 syncope patients with no obvious diagnosis in ED, recruited to a prior cohort study (2007-2008), were used as a comparator. Primary endpoint was symptomatic significant arrhythmia at 90-day follow-up. RESULTS: During the prospective study period, 86 patients were recruited. 90-day diagnostic yield for symptomatic significant arrhythmia was 10.5% (95% CI 4.0 to 16.9; 9 of 86) versus 2.0% (95% CI 0.9 to 3.1; 12 of 603) in the comparator group. 24 patients (27.9%) had a significant arrhythmia (five serious); 26 patients (30.2%) had serious outcomes (major adverse cardiac event and/or death). Blinded patch report review suggested the patch would significantly reduce requirement for standard outpatient ambulatory ECG monitoring. 56 of 76 returned patches had a diagnostic finding within±45 s of a triggered/diary event (73.7% diagnostic utility; 95% CI 63.7 to 83.6); 34 of 56 (61%) for sinus rhythm or ectopic beats only. CONCLUSIONS: Routine, early ambulatory ECG monitoring in ED patients with unexplained syncope is probably warranted. A large-scale trial comparing this approach to standard care with cost-effectiveness and safety analysis is now required. TRIAL REGISTRATION: NCT02683174.

Neural networks as a tool to predict syncope risk in the Emergency Department.

AIMS: There is no universally accepted tool for the risk stratification of syncope patients in the Emergency Department. The aim of this study was to investigate the short-term predictive accuracy of an artificial neural network (ANN) in stratifying the risk in this patient group. METHODS AND RESULTS: We analysed individual level data from three prospective studies, with a cumulative sample size of 1844 subjects. Each dataset was reanalysed to reduce the heterogeneity among studies defining abnormal electrocardiogram (ECG) and serious outcomes according to a previous consensus. Ten variables from patient history, ECG, and the circumstances of syncope were used to train and test the neural network. Given the exploratory nature of this work, we adopted two approaches to train and validate the tool. One approach used 4/5 of the data for the training set and 1/5 for the validation set, and the other approach used 9/10 for the training set and 1/10 for the validation set. The sensitivity, specificity, and area under the receiver operating characteristic curve of ANNs in identifying short-term adverse events after syncope were 95% [95% confidence interval (CI) 80-98%], 67% (95% CI 62-72%), 0.69 with the 1/5 approach and 100% (95% CI 84-100%), 79% (95% CI 72-85%), 0.78 with the 1/10 approach. CONCLUSION: The results of our study suggest that ANNs are effective in predicting the short-term risk of patients with syncope. Prospective studies are needed in order to compare ANNs' predictive capability with existing rules and clinical judgment.

Discontinuation of dual antiplatelet therapy over 12 months after acute coronary syndromes increases risk for adverse events in patients treated with percutaneous coronary intervention: systematic review and meta-analysis.

INTRODUCTION: Duration of dual antiplatelet therapy (DAPT) following acute coronary syndrome (ACS) hospitalization remains to be defined, both for patients treated medically and for those undergoing percutaneous transluminal coronary angioplasty (PTCA). METHODS: PubMed, Cochrane, and Google Scholar were systematically searched for studies including patients presenting with ACS, and treated either with DAPT longer than or shorter than 12 months. Multivariable-adjusted risk estimates for death and recurrent ACS with stopping DAPT after 12 months (odds ratios [OR] 95% confidence intervals [CI]) were pooled after logarithmic transformation according to random-effect models with inverse-variance weighting. RESULTS: Five studies with 49,586 patients were included. Median age was 66 (64-67) years, with 67% (65-75) males. Myocardial infarction (MI) represented the admission diagnosis for 88% (60-100) of the patients, and 66% (50-74) were treated with stenting. After a follow-up of 2.1 years (1.5-2.7), 40% (35-46) still on DAPT after 12 months and the rates of death or recurrent ACS were 16.6 (14.5-17.0). Risk of adverse events for patients stopping DAPT after 1 year was significantly increased (OR = 1.19 [1.07-1.32]) for those receiving stents, but not for patients managed medically (OR = 1.13 [0.95-1.35]). The increased risk did not vary according to age, gender, myocardial infarction as admission diagnosis, and kind of stent. CONCLUSIONS: Interruption of DAPT over 12 months after ACS increases the risk of adverse events for patients treated with PTCA, but not for those managed conservatively, independently from baseline features and admission diagnosis. This hypothesis-generating finding should be tested in randomized controlled trials.

Diagnosis and management of acute aortic dissection in the emergency department.

Acute aortic dissection is often misdiagnosed as a result of its atypical presentations. It affects 4000 patients a year in the UK of all ages, not just older patients, with increasing numbers of cases expected in the future because of the ageing population. Dissection of the aortic wall leads to sudden, severe pain, and commonly end-organ symptoms which must be recognised. Acute aortic dissection can be challenging to diagnose in the emergency department because of the multitude of possible presentations and the need for selective testing with Computed Tomography Angiography (CTA). Clinicians often miss acute aortic dissection because it is not considered in the differential diagnosis, and the challenge lies in identifying acute aortic dissection in a sea of complaints of chest, back and abdominal pain. There are several ways to improve diagnosis, including awareness campaigns, better education about patients in which to consider acute aortic dissection, and improved detection strategies including which patients should receive CTA. Clinical decision tools and biomarkers could help, but further research is required and is a research focus in emergency medicine. Once diagnosed, blood pressure control, analgesia and urgent surgery or transfer to enable this to occur with minimal delay is required.

The syncope core management process in the emergency department: a consensus statement of the EUSEM syncope group.

The European Society of Cardiology issued updated syncope guidelines in 2018 which included recommendations for managing syncope in the emergency department (ED) setting. However, these guidelines lack detailed process-oriented instructions regarding the fact that ED syncope patients initially present with a transient loss of consciousness (TLOC), which can have a broad spectrum of causes. This study aims to establish a European consensus on the general process of the workup and care for patients with suspected syncope and provides rules for sufficient and systematic management of the broad group of syncope (initially presenting as TLOC) patients in the ED. A variety of European diagnostic and therapeutic standards for syncope patients were reviewed and summarized in three rounds of a modified Delphi process by the European Society for Emergency Medicine syncope group. Based on a consensus statement, a detailed process pathway is created. The primary outcome of this work is the presentation of a universal process pathway for the structured management of syncope patients in European EDs. The here presented extended event process chain (eEPC) summarizes and homogenizes the process management of European ED syncope patients. Additionally, an exemplary translation of the eEPC into a practice-based flowchart algorithm, which can be used as an example for practical use in the ED, is provided in this work. Syncope patients, initially presenting with TLOC, are common and pose challenges in the ED. Despite variations in process management across Europe, the development of a universally applicable syncope eEPC in the ED was successfully achieved. Key features of the consensus and eEPC include ruling out life-threatening causes, distinguishing syncope from nonsyncopal TLOCs, employing syncope risk stratification categories and based on this, making informed decisions regarding admission or discharge.

Management of syncope in the Emergency Department: a European prospective cohort study (SEED).

BACKGROUND AND IMPORTANCE: In 2018, the European Society of Cardiology (ESC) produced syncope guidelines that for the first-time incorporated Emergency Department (ED) management. However, very little is known about the characteristics and management of this patient group across Europe. OBJECTIVES: To examine the prevalence, clinical presentation, assessment, investigation (ECG and laboratory testing), management and ESC and Canadian Syncope Risk Score (CSRS) categories of adult European ED patients presenting with transient loss of consciousness (TLOC, undifferentiated or suspected syncope). DESIGN: Prospective, multicentre, observational cohort study. SETTINGS AND PARTICIPANTS: Adults (≥18 years) presenting to European EDs with TLOC, either undifferentiated or thought to be of syncopal origin. MAIN RESULTS: Between 00:01 Monday, September 12th to 23:59 Sunday 25 September 2022, 952 patients presenting to 41 EDs in 14 European countries were enrolled from 98 301 ED presentations (n = 40 sites). Mean age (SD) was 60.7 (21.7) years and 487 participants were male (51.2%). In total, 379 (39.8%) were admitted to hospital and 573 (60.2%) were discharged. 271 (28.5%) were admitted to an observation unit first with 143 (52.8%) of these being admitted from this. 717 (75.3%) participants were high-risk according to ESC guidelines (and not suitable for discharge from ED) and 235 (24.7%) were low risk. Admission rate increased with increasing ESC high-risk factors; 1 ESC high-risk factor; n = 259 (27.2%, admission rate=34.7%), 2; 189 (19.9%; 38.6%), 3; 106 (11.1%, 54.7%, 4; 62 (6.5%, 60.4%), 5; 48 (5.0%, 67.9%, 6+; 53 (5.6%, 67.9%). Furthermore, 660 (69.3%), 250 (26.3%), 34 (3.5%) and 8 (0.8%) participants had a low, medium, high, and very high CSRS respectively with respective admission rates of 31.4%, 56.0%, 76.5% and 75.0%. Admission rates (19.3-88.9%), use of an observation/decision unit (0-100%), and percentage high-risk (64.8-88.9%) varies widely between countries. CONCLUSION: This European prospective cohort study reported a 1% prevalence of syncope in the ED. 4 in 10 patients are admitted to hospital although there is wide variation between country in syncope management. Three-quarters of patients have ESC high-risk characteristics with admission percentage rising with increasing ESC high-risk factors.

A review of blood component usage in a large UK emergency department after implementation of simple measures.

OBJECTIVES: To review clinical indications and demographics of transfusion and the patterns of blood component ordering, transfusion, wastage and traceability, before (2007) and after (2011) implementation of simple improvement strategies. METHODS: Retrospective case note review of all patients presenting to the Royal Infirmary of Edinburgh (RIE) Emergency Department (ED) for whom a blood component was requested and historic comparison. Improvement measures implemented between 2007 and 2011 included (1) formal staff education, (2) use of e-learning Module One Safe Transfusion Practice (traceability update, Medicines and Healthcare products Regulatory Agency (MHRA) traceability regulations and importance of returning completed blood component tags), (3) an ED resuscitation room blood fridge, (4) introduction of a dedicated ED transfusion consultant and ED transfusion link nurse and (5) the presence of an ED consultant on the Hospital Transfusion Group. RESULTS: Between 1st January and 31st December 2011, blood components were requested for 255 patient episodes, totalling 1034 individual units. 687 units (66.4%) of blood component were transfused, 248 components (24.0%) were recycled, 90 components (8.7%) were discarded and nine units (0.9%) were unaccounted for. There was a 64% reduction in blood component ordering (3209 vs 1034 units), a 39% reduction in blood component transfusion (1131 vs 687 units) and a 96% reduction in unaccounted units (214 vs 9 units) between 2007 and 2011. There was a rise in the median age of the patient for whom a transfusion request was made from 63.9 years in 2007 to 67.0 years in 2011. CONCLUSIONS: Blood component ordering, usage and traceability within the ED have improved significantly since 2007 following implementation of simple strategies. The age of ED transfusion recipients is increasing.

Multicentre open label randomised controlled trial of immediate enhanced ambulatory ECG monitoring versus standard monitoring in acute unexplained syncope patients: the ASPIRED study.

INTRODUCTION: Diagnosing underlying arrhythmia in emergency department (ED) syncope patients is difficult. There is a evidence that diagnostic yield for detecting underlying arrhythmia is highest when cardiac monitoring devices are applied early, ideally at the index visit. This strategy has the potential to change current syncope management from low diagnostic yield Holter to higher yield ambulatory monitoring, reduce episodes of syncope, reduce risk of recurrence and its potential serious consequences, reduce hospital admissions, reduce overall health costs and increase quality of life by allowing earlier diagnosis, treatment and exclusion of clinically important arrhythmias. METHODS AND ANALYSES: This is a UK open prospective parallel group multicentre randomised controlled trial of an immediate 14-day ambulatory patch heart monitor vs standard care in 2234 patients presenting acutely with unexplained syncope. Our patient focused primary endpoint will be number of episodes of syncope at 1 year. Health economic evaluation will estimate the incremental cost per syncope episode avoided and quality-adjusted life year gained. ETHICS AND DISSEMINATION: Informed consent for participation will be sought. The ASPIRED trial received a favourable ethical opinion from South East Scotland Research Ethics Committee 01 (21/SS/0073). Results will be disseminated via scientific publication, lay summary and visual abstract. TRIAL REGISTRATION NUMBER: ISRCTN 10278811.

A Digital Health Intervention for Concussion: Development and Clinical Feasibility Study.

BACKGROUND: Concussion is a common condition that can lead to a constellation of symptoms that affect quality of life, social integration, and return to work. There are several evidence-based behavioral and psychological interventions that have been found to improve postconcussion symptom burden. However, these are not routinely delivered, and individuals receive limited support during their concussion recovery. OBJECTIVE: This study aimed to develop and test the feasibility of a digital health intervention using a systematic evidence-, theory-, and person-based approach. METHODS: This was a mixed methodology study involving a scoping review (n=21), behavioral analysis, and logic model to inform the intervention design and content. During development, the intervention was optimized with feedback from individuals who had experienced concussions (n=12) and health care professionals (n=11). The intervention was then offered to patients presenting to the emergency department with a concussion (n=50). Participants used the intervention freely and input symptom data as part of the program. A number of outcome measures were obtained, including participant engagement with the intervention, postconcussion symptom burden, and attitudes toward the intervention. A selection of participants (n=15) took part in in-depth qualitative interviews to understand their attitudes toward the intervention and how to improve it. RESULTS: Engagement with the intervention functionality was 90% (45/50) for the symptom diary, 62% (31/50) for sleep time setting, 56% (28/50) for the alcohol tracker, 48% (24/50) for exercise day setting, 34% (17/50) for the thought diary, and 32% (16/50) for the goal setter. Metrics indicated high levels of early engagement that trailed off throughout the course of the intervention, with an average daily completion rate of the symptom diary of 28.23% (494/1750). A quarter of the study participants (13/50, 26%) were classified as high engagers who interacted with all the functionalities within the intervention. Quantitative and qualitative feedback indicated a high level of usability and positive perception of the intervention. Daily symptom diaries (n=494) demonstrated a wide variation in individual participant symptom burden but a decline in average burden over time. For participants with Rivermead scores on completion of HeadOn, there was a strong positive correlation (r=0.86; P<.001) between their average daily HeadOn symptom diary score and their end-of-program Rivermead score. Insights from the interviews were then fed back into development to optimize the intervention and facilitate engagement. CONCLUSIONS: Using this systematic approach, we developed a digital health intervention for individuals who have experienced a concussion that is designed to facilitate positive behavior change. Symptom data input as part of the intervention provided insights into postconcussion symptom burden and recovery trajectories. TRIAL REGISTRATION: ClinicalTrials.gov NCT05069948; https://clinicaltrials.gov/ct2/show/NCT05069948.