Skip to content
How It Works
Explore
Ask a Question Resources Pricing
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Sign Up
PubMed This is a summary of 19 peer-reviewed journal articles Updated
Cardiology

Recognizing Symptoms and Emergency Warning Signs

At a Glance

Fainting during or right after exercise, seizure-like collapse, palpitations with dizziness, and multiple ICD shocks can signal a dangerous rhythm in familial ventricular tachycardia. These events need emergency assessment, while a stable single ICD shock needs prompt device-clinic guidance.

Recognizing the difference between everyday symptoms and serious warning signs is one of the most important skills for families living with inherited arrhythmias. Because conditions like CPVT (Catecholaminergic Polymorphic Ventricular Tachycardia) and ARVC (Arrhythmogenic Right Ventricular Cardiomyopathy) are triggered by adrenaline or structural changes, the way symptoms appear is often very specific [1][2].

It is important to remember that a “normal” resting ECG (Electrocardiogram) does not rule out these conditions [3][4]. If your child has fainted during exercise, they need a specialized evaluation by a pediatric electrophysiologist, regardless of what a standard ECG shows [5][6].

Red Flags: When the Heart Signals Trouble

In these conditions, “red flags” are symptoms that suggest the heart is struggling to maintain a safe rhythm. These symptoms often occur during physical activity or intense emotion (like anger, fright, or even a temper tantrum) [1][7].

  • Exertional Syncope (Fainting during or immediately after activity): This is one of the most critical warning signs. If a person faints while running, swimming, or playing, or in the immediate recovery period, it is an immediate red flag that the heart’s rhythm has become dangerously fast [1][8]. Any unexplained fainting during or immediately after exercise requires urgent cardiac assessment [3].
  • Seizure-Like Episodes: Many children with inherited arrhythmias are initially misdiagnosed with epilepsy [9][10]. When the heart beats too fast to pump blood to the brain, the brain may react with “seizure-like” movements, such as body stiffening or brief jerking [11].
    • The Key Action: Parents cannot reliably tell the difference between a true seizure and an arrhythmic collapse at home. Any first, prolonged, recurrent, or exertion-associated seizure-like collapse requires emergency assessment. Call emergency services, start CPR if the person is unresponsive and not breathing normally, and use an AED when indicated [12][11].
  • Palpitations with Dizziness: Feeling your heart “flip-flop” or race is common, but when these palpitations (the sensation of a racing or irregular heartbeat) are accompanied by dizziness, lightheadedness, chest pain, or feeling like you might pass out, they require urgent evaluation [13][14].

What is an “Electrical Storm”?

For patients with an ICD (Implantable Cardioverter Defibrillator), an electrical storm is an absolute medical emergency. It is defined as:

  • Three or more episodes of sustained fast heart rhythms (Ventricular Tachycardia or Fibrillation) or appropriate device therapies within a 24-hour period [15].
  • These episodes usually require an intervention to stop, such as a shock from an ICD or emergency medication [15][16].

If an ICD delivers multiple shocks in one day, the heart is in a state of electrical instability that must be treated immediately in a hospital setting [16][17].

Action Guide: ER vs. Clinic

Knowing where to go can save lives and reduce unnecessary anxiety. Use the following criteria as a general guide, but obtain written, device-specific instructions from your clinic.

Go to the Emergency Room (Call 911) If:

  • The person is unresponsive and not breathing normally: Call 911, start CPR, and use an AED.
  • Any loss of consciousness (fainting) that occurs during or immediately after exercise, swimming, or intense emotional stress [1][8].
  • Any “seizure-like” event, especially if it happened during activity [9][18].
  • Multiple ICD shocks occur in a single day, or a shock is accompanied by severe symptoms or collapse [17][15].
  • Chest pain or extreme shortness of breath that does not go away with rest [19].

Contact Your Specialist Clinic Promptly If:

  • A single ICD shock occurs but the patient is otherwise stable (follow your treating center’s instructions).
  • The ICD makes an alert sound or vibration. An alert can signal a low battery, but it can also indicate a serious issue like a broken wire (lead failure) or oversensing. Promptly contact your device team [16].
  • You notice new or worsening palpitations that are not causing dizziness or fainting [14].
  • Your child is feeling more tired than usual during their normal activities [19].
Symptom Severity Immediate Action
Unresponsive / Not breathing normally Emergency Call 911, Start CPR, Use AED
Fainting during/after exercise Emergency Call 911 / Go to ER
Seizure-like movements Emergency Call 911 / Go to ER
Multiple ICD Shocks Emergency Call 911 / Go to ER
Single ICD Shock (patient stable) Urgent Contact Device Clinic Immediately
ICD Alert sound/vibration Urgent Contact Device Clinic Promptly

Common questions in this guide

Can a normal resting ECG rule out an inherited ventricular arrhythmia?
No. Conditions such as CPVT may have a normal resting ECG, so fainting during or right after exercise or intense emotion still needs prompt evaluation by a pediatric electrophysiologist or cardiology team.
When is fainting during exercise an emergency?
Any unexplained fainting during or immediately after exercise, swimming, or intense emotional stress is a serious warning sign that needs emergency assessment. Call 911, especially if the person is unresponsive or not breathing normally.
Could a seizure-like episode be caused by a heart rhythm problem?
Yes. An excessively fast heart rhythm can reduce blood flow to the brain and cause stiffening or brief jerking that resembles a seizure. A caregiver cannot reliably tell the causes apart at home, so call emergency services for a first, prolonged, recurrent, or activity-related event; start CPR and use an AED if the person is unresponsive and not breathing normally.
What does an electrical storm mean for someone with an ICD?
Electrical storm means three or more episodes of sustained ventricular tachycardia or ventricular fibrillation, or appropriate ICD therapies, within 24 hours. It is a medical emergency requiring immediate hospital care; call 911 for multiple shocks or severe symptoms or collapse.
What should I do after one ICD shock if the patient seems stable?
Contact the device clinic immediately and follow the treating center’s instructions, even if the patient feels well. Call 911 instead if there are multiple shocks, collapse, severe symptoms, or the person is unresponsive or not breathing normally.
When do palpitations need urgent evaluation?
Racing or irregular heartbeat sensations need urgent evaluation when they occur with dizziness, lightheadedness, chest pain, or feeling close to fainting. New or worsening palpitations without those symptoms should still be reported promptly to the specialist clinic.

Questions For You

Answer a question to get research tailored to you. Your answers are private.

Get notified when new evidence is published on Familial ventricular tachycardia.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.My child had an episode that looked like a seizure during physical activity; should we be prioritising a pediatric electrophysiology evaluation over neurology?
  2. 2.What is the specific emergency protocol for my child if they experience a fainting spell during exertion or intense emotion?
  3. 3.How can we differentiate between benign palpitations and 'red flag' heart racing in our specific case?
  4. 4.If our ICD (if applicable) delivers a shock, under what circumstances should we call 911 immediately versus contacting your office?
  5. 5.Can you provide us with a written, device-specific emergency action plan?

References

References (19)
  1. 1

    Pediatric Catecholaminergic Polymorphic Ventricular Tachycardia: A Translational Perspective for the Clinician-Scientist.

    Kallas D, Lamba A, Roston TM, et al.

    International journal of molecular sciences 2021; (22(17)) doi:10.3390/ijms22179293.

    PMID: 34502196
  2. 2

    Catecholaminergic Polymorphic Ventricular Tachycardia: An Unusual Case of Fright-Induced Prehospital Cardiac Arrest in a Healthy 6-Year-Old Child.

    Wilson M, Schwartz S, Verbeek PR

    Prehospital emergency care 2020; (24(1)):94-99 doi:10.1080/10903127.2019.1612972.

    PMID: 31038375
  3. 3

    Catecholaminergic polymorphic ventricular tachycardia managed as orthostatic dysregulation and epilepsy in 11- and 15-year-old sisters.

    Fujita S, Nishida K, Irabu H, et al.

    Pediatrics international : official journal of the Japan Pediatric Society 2018; (60(11)):998-1001 doi:10.1111/ped.13688.

    PMID: 30157307
  4. 4

    Catecholaminergic Polymorphic Ventricular Tachycardia: Clinical Characteristics, Diagnostic Evaluation and Therapeutic Strategies.

    Aggarwal A, Stolear A, Alam MM, et al.

    Journal of clinical medicine 2024; (13(6)) doi:10.3390/jcm13061781.

    PMID: 38542006
  5. 5

    Clinical and genetic profile of catecholaminergic polymorphic ventricular tachycardia in Hong Kong Chinese children.

    Yu TC, Liu AP, Lun KS, et al.

    Hong Kong medical journal = Xianggang yi xue za zhi 2016; (22(4)):314-9 doi:10.12809/hkmj154653.

    PMID: 27256466
  6. 6

    Exercise testing oversights underlie missed and delayed diagnosis of catecholaminergic polymorphic ventricular tachycardia in young sudden cardiac arrest survivors.

    Giudicessi JR, Ackerman MJ

    Heart rhythm 2019; (16(8)):1232-1239 doi:10.1016/j.hrthm.2019.02.012.

    PMID: 30763784
  7. 7

    Unexpected Pediatric Cardiac Arrest in a Toddler: A Case of Catecholaminergic Polymorphic Ventricular Tachycardia Presenting as Ventricular Fibrillation.

    Disla Cuevas A, Tran C, Daya M, Chung S

    Pediatric emergency care 2026; (42(9)):e128-e133 doi:10.1097/PEC.0000000000003603.

    PMID: 41968876
  8. 8

    BASIC AND CLINICAL INSIGHTS IN CATECHOLAMINERGIC (FAMILIAL) POLYMORPHIC VENTRICULAR TACHYCARDIA.

    Márquez MF, Totomoch-Serra A, Rueda A, et al.

    Revista de investigacion clinica; organo del Hospital de Enfermedades de la Nutricion 2019; (71(4)):226-236 doi:10.24875/RIC.19002939.

    PMID: 31448784
  9. 9

    Catecholaminergic Polymorphic Ventricular Tachycardia Type 2 Presenting as Seizure in a Child: Diagnostic Pitfalls.

    Rahimpour F, Moghaddam ES, Fallahi NA

    JACC. Case reports 2026; (31(36)):109233 doi:10.1016/j.jaccas.2026.109233.

    PMID: 42435031
  10. 10

    Prognostic impact of misdiagnosis of cardiac channelopathies as epilepsy.

    Ramos-Maqueda J, Bermúdez-Jiménez F, Ruiz RM, et al.

    PloS one 2020; (15(4)):e0231442 doi:10.1371/journal.pone.0231442.

    PMID: 32298319
  11. 11

    A Rare Presentation of Sick Sinus Syndrome: Generalized Seizures.

    Elkattawy S, Younes I, Alyacoub R, et al.

    Cureus 2022; (14(3)):e23631 doi:10.7759/cureus.23631.

    PMID: 35495008
  12. 12

    Seizure Triggered by Sick Sinus Syndrome.

    Patel N, Majeed F, Sule AA

    BMJ case reports 2017; (2017()) doi:10.1136/bcr-2017-222011.

    PMID: 29103011
  13. 13

    Catecholaminergic Polymorphic Ventricular Tachycardia.

    Kim CW, Aronow WS, Dutta T, et al.

    Cardiology in review 2020; (28(6)):325-331 doi:10.1097/CRD.0000000000000302.

    PMID: 31934898
  14. 14

    Clinical features and arrhythmic complications of patients with pediatric-onset arrhythmogenic right ventricular dysplasia.

    Sevinç Şengül F, Tunca Şahin G, Özgür S, et al.

    Anatolian journal of cardiology 2019; (22(2)):60-67 doi:10.14744/AnatolJCardiol.2019.56985.

    PMID: 31375646
  15. 15

    Management of patients with an electrical storm or clustered ventricular arrhythmias: a clinical consensus statement of the European Heart Rhythm Association of the ESC-endorsed by the Asia-Pacific Heart Rhythm Society, Heart Rhythm Society, and Latin-American Heart Rhythm Society.

    Lenarczyk R, Zeppenfeld K, Tfelt-Hansen J, et al.

    Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology 2024; (26(4)) doi:10.1093/europace/euae049.

    PMID: 38584423
  16. 16

    Management of ventricular electrical storm: a contemporary appraisal.

    Kowlgi GN, Cha YM

    Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology 2020; (22(12)):1768-1780 doi:10.1093/europace/euaa232.

    PMID: 32984880
  17. 17

    Implantable cardioverter-defibrillator use in catecholaminergic polymorphic ventricular tachycardia: A systematic review.

    Roston TM, Jones K, Hawkins NM, et al.

    Heart rhythm 2018; (15(12)):1791-1799 doi:10.1016/j.hrthm.2018.06.046.

    PMID: 30063211
  18. 18

    Differentiating motor phenomena in tilt-induced syncope and convulsive seizures.

    Shmuely S, Bauer PR, van Zwet EW, et al.

    Neurology 2018; (90(15)):e1339-e1346 doi:10.1212/WNL.0000000000005301.

    PMID: 29549227
  19. 19

    Implantable Cardioverter Defibrillator for Primary Prevention in Children With Arrhythmogenic Right Ventricular Cardiomyopathy: A Case Series.

    Nagashima-Otsuki A, Ishii T, Yamaguchi Y, et al.

    Cureus 2025; (17(1)):e77253 doi:10.7759/cureus.77253.

    PMID: 39931627

This page is for informational purposes only and does not constitute medical advice. Warning signs, ICD responses, and emergency steps can vary, so follow the written plan from your cardiology or device team and call emergency services for a life-threatening event.