How do I know if my fainting episode could be heart-related rather than a simple faint?

Vasovagal syncope — the common faint — has a typical pattern: prolonged standing, heat, pain, or emotional stimulus produces a warning of nausea, sweating, and light-headedness before blackout, with rapid recovery. Cardiac syncope is more abrupt with little or no warning, often during or immediately after exercise, during emotional shock or a sudden loud noise, during swimming, or from sleep. Cardiac syncope may be followed by chest pain or palpitations, and bystanders may observe seizure-like movements (due to cerebral hypoperfusion). A family history of sudden death under 50, unexplained drowning, or childhood seizures significantly raises the probability of an inherited arrhythmia syndrome.

My parent died suddenly in their 40s. Should I have a cardiac assessment?

Yes — unexplained sudden death under 50 in a first-degree relative is a strong indication for cardiac assessment of all first-degree family members. This typically includes a 12-lead ECG with QTc measurement, a detailed family pedigree going back three generations, and a specialist cardiology referral. In some cases, an exercise stress test, ambulatory ECG, or cardiac MRI is indicated. Where a genetic cause has been identified in the deceased (via molecular autopsy), targeted genetic testing of relatives can identify who carries the mutation even before symptoms develop. Cascade screening aims to find affected relatives before a life-threatening event.

What is long QT syndrome and which medications do I need to avoid?

Long QT syndrome is a genetic condition in which the heart's electrical recovery phase — measured as the QT interval on ECG — is abnormally prolonged. This can degenerate into a specific dangerous arrhythmia called torsades de pointes, which can cause cardiac arrest. The main management in general practice is avoiding QT-prolonging drugs — the CredibleMeds database (crediblemeds.org) lists hundreds of medications with varying risk. High-risk examples include macrolide antibiotics (clarithromycin, azithromycin, erythromycin), fluoroquinolones, ondansetron particularly IV, methadone, haloperidol and other antipsychotics, citalopram above 20 mg, and many antifungals. A beta-blocker — usually nadolol or propranolol — is the mainstay of medical treatment.

Can I still exercise with Brugada syndrome or ARVC?

It depends on the specific syndrome. Brugada syndrome does not preclude recreational exercise in most cases — the main triggers are fever, certain drugs, large alcohol intake, and sleep. However, competitive sport is assessed case-by-case with an electrophysiologist. ARVC is different: endurance exercise accelerates the fibrofatty progression of the condition and significantly increases arrhythmia risk. Competitive sport is firmly restricted in ARVC, and even recreational endurance exercise (running, cycling, swimming at high intensity) is individually assessed. CPVT, triggered specifically by catecholamines during exercise and emotion, also requires careful sport restriction. An electrophysiologist should make all sports and activity recommendations for inherited arrhythmia patients.

How does cascade family screening for inherited heart rhythm conditions work in Australia?

When a person is diagnosed with an inherited arrhythmia syndrome, their first-degree relatives — parents, siblings, and children — are offered screening. The process starts with genetic counselling before any testing, so family members understand the implications. If a specific genetic mutation has been identified in the proband, relatives undergo targeted genetic testing; carriers are then followed clinically even if asymptomatic. If no mutation has been found, phenotypic screening uses ECG, exercise stress test, Holter monitoring, and cardiac MRI depending on the syndrome. The Australian Genetic Heart Disease Registry coordinates this process through specialist clinics in most major cities. Cascade screening has identified life-saving diagnoses in asymptomatic relatives.

Inherited primary arrhythmia syndromes

Inherited arrhythmia syndromes: long QT, Brugada, CPVT and ARVC

By Dr HB Lo, FACRRM Reviewed 30 August 2026 11 min read

Inherited primary arrhythmia syndromes — long QT (LQTS), Brugada, CPVT, and ARVC — cause sudden cardiac death in young, otherwise well individuals. The GP role: recognise red flags — exertional or emotion-triggered syncope, syncope during swimming or sleep, family history of sudden death under 50.

In LQTS, check every prescription against the CredibleMeds QT-prolonging drug list; macrolides, fluoroquinolones, and ondansetron are common offenders. Brugada patients need paracetamol at 38°C — fever triggers ventricular fibrillation.

All suspected cases need specialist cardiology, genetic counselling, and cascade screening of first-degree relatives.

Inherited primary arrhythmia syndromes (IPAS) are genetically determined disorders of cardiac ion channels or structural cardiac proteins that create a substrate for life-threatening ventricular arrhythmia in young, otherwise healthy individuals. They account for a substantial proportion of sudden cardiac death (SCD) under age 35 in Australia — including unwitnessed drowning episodes associated with swimming, unexpected nocturnal death, and a subset of cases classified as sudden unexplained death in infancy (SUDI).

The five major syndromes encountered in Australian general practice are: Long QT Syndrome (LQTS), where prolonged QTc leads to torsades de pointes and potential cardiac arrest; Brugada syndrome, characterised by right-precordial ST elevation and risk of ventricular fibrillation typically during fever or sleep; Catecholaminergic Polymorphic VT (CPVT), in which exercise and emotion trigger bidirectional ventricular tachycardia in a structurally normal heart; Short QT Syndrome (SQTS), a rare condition with abbreviated QTc and atrial fibrillation or VF; and Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC), involving fibrofatty replacement of right ventricular myocardium triggered and accelerated by endurance exercise.

The general practice role is not to manage these conditions independently, but to recognise the red flags, initiate appropriate investigations, refer promptly, and ensure cascade screening of family members. The Australian Genetic Heart Disease Registry coordinates specialist genetic heart disease clinics nationally.

A. Core clinical — the AU general-practice framework

History — recognising the red flags

The most important diagnostic step is a structured history. Most IPAS present with syncope, near-syncope, or a family history of sudden death — and the trigger or circumstance of syncope is the key discriminator.

Syncope triggers by syndrome:

Syndrome	Trigger / circumstances
LQT1	Exertion, especially swimming and cold-water immersion
LQT2	Emotion (fright, anger); sudden auditory stimulus — alarm clock, phone ringing; postpartum
LQT3	Sleep or rest; minimal sympathetic stimulation
Brugada	Sleep; fever; excessive alcohol; large meal; certain drugs
CPVT	Exercise; emotional stress; epinephrine
ARVC	Exercise, particularly sustained endurance activity; palpitations after exertion

Family history (3-generation pedigree): SCD under age 50; drowning while swimming; “found dead” or unexpected nocturnal death; SUDI/SIDS; childhood syncope or seizure; pacemaker or ICD implantation in a family member; postpartum sudden death.

Personal history: Characterise syncope — duration of blackout, trigger, warning symptoms, recovery rate. Enquire about previous seizure diagnoses (some LQTS is misdiagnosed as epilepsy). Review the full medication list against the CredibleMeds QT-prolonging drug register. Assess electrolyte status — hypokalaemia and hypomagnesaemia worsen QT prolongation significantly. Ask about hearing loss (Jervell–Lange-Nielsen syndrome, an autosomal recessive LQTS variant with congenital deafness). Note pregnancy and postpartum status for LQT2.

Examination

IPAS produces no specific findings on physical examination in most patients — the diagnosis is electrocardiographic and genetic. Standard cardiovascular examination is normal in channelopathies. Hearing assessment is relevant for Jervell–Lange-Nielsen syndrome. ARVC rarely produces signs of right ventricular failure in advanced cases.

Electrocardiogram

A resting 12-lead ECG with careful QTc measurement using the Bazett or Fridericia formula is the cornerstone investigation. Key findings by syndrome:

LQTS: QTc >480 ms in females or >470 ms in males is probable; >460 ms is borderline. Assessment using the Schwartz score incorporates ECG, clinical, and family criteria — a score ≥3.5 indicates high probability.
Brugada Type 1: Coved ST elevation ≥2 mm in leads V1–V3 — the spontaneous Type 1 pattern is diagnostic. Type 2 and Type 3 patterns are non-diagnostic without provocation.
CPVT: Resting ECG is typically entirely normal — the diagnosis requires provocation with exercise or adrenaline.
SQTS: QTc ≤340 ms.
ARVC: Epsilon waves, T-wave inversion in V1–V3, right bundle branch block delay, and frequent right ventricular ectopy.

Further investigations in general practice

Once IPAS is suspected, refer to specialist cardiology. Further investigations include: exercise stress test (LQT1 paradoxical QTc prolongation during exercise; CPVT — bidirectional or polymorphic VT; ARVC — exercise-induced ventricular ectopy); ambulatory ECG (Holter or extended monitor); echocardiogram to exclude structural disease; cardiac MRI for ARVC (the gold standard for fibrofatty change and RV function); and genetic testing of the proband with subsequent cascade testing of first-degree relatives. Sodium-channel-blocker challenge (ajmaline or flecainide) can unmask Brugada Type 1 in suspected non-spontaneous cases — this is performed in a monitored specialist setting only.

MBS item 73297 funds genetic testing for IPAS probands meeting clinical criteria, and for first-degree relatives once a proband mutation has been identified.

B. Long QT syndrome, Brugada, and CPVT — evidence and management

Long QT syndrome

ESC 2022 guidelines (Zeppenfeld et al.) and HRS/EHRA/APHRS 2013 consensus (Priori et al.) together provide the evidence framework.

Seventeen LQTS genes have been identified. The three most important in general practice are: LQT1 (KCNQ1, ~30%), triggered by exercise — especially swimming; LQT2 (KCNH2, ~25%), triggered by sudden noise and emotion, with a particular postpartum risk window; and LQT3 (SCN5A, ~10%), which causes events during sleep and rest.

Beta-blockers are first-line: Nadolol and propranolol are preferred — registry evidence demonstrates 60–80% reduction in cardiac events for LQT1 and LQT2. Selective beta-1 blockers (atenolol, metoprolol, bisoprolol) have shown inferior efficacy in LQTS registries and are not preferred. Mexiletine, a sodium-channel blocker, is specifically effective for LQT3.

Drug avoidance is the most actionable GP responsibility: The CredibleMeds register categorises QT risk. Avoid in LQTS patients:

Antibiotics: Macrolides (clarithromycin, erythromycin, azithromycin), fluoroquinolones (ciprofloxacin, moxifloxacin, levofloxacin)
Antifungals: Fluconazole, voriconazole
Antiemetics: Ondansetron (particularly IV), domperidone, droperidol
Antipsychotics: Haloperidol (especially IV), ziprasidone, thioridazine, chlorpromazine
Antidepressants: Citalopram above 20–40 mg, escitalopram, tricyclics
Antimalarials: Chloroquine, hydroxychloroquine, mefloquine

At every prescription encounter, check the patient’s current medication list against CredibleMeds before issuing a new script.

Maintain normal electrolytes: Hypokalaemia and hypomagnesaemia shorten the effective refractory period and compound QT prolongation. Supplement as needed; consider spironolactone to maintain potassium above 4.0 mmol/L.

Left cardiac sympathetic denervation (LCSD) — surgical denervation of T1–T5 sympathetic ganglia — reduces arrhythmic events by 80–90% in patients with LQTS or CPVT refractory to beta-blockers. Available at AU expert centres. ICD implantation is reserved for cardiac arrest survivors, syncope despite optimal beta-blocker therapy, and high-risk genetic phenotype combinations.

Brugada syndrome

eTG and ESC 2022 guidelines converge on the key Brugada management principles. The spontaneous Type 1 coved ECG pattern — ST elevation ≥2 mm in V1–V3 — combined with a history of syncope, VF, or sustained VT is the primary indication for ICD. Asymptomatic patients with a non-spontaneous Type 1 pattern are risk-stratified individually by an electrophysiologist.

Fever management is critical: Fever can unmask Brugada Type 1 and trigger ventricular fibrillation. Patients with known Brugada should take paracetamol promptly when temperature reaches 38°C, without waiting to see if fever develops further. This requires patient education and a clear written action plan. Advise attendance at an emergency department if paracetamol does not control fever or if the patient feels unwell.

Drug avoidance: Check BrugadaDrugs.org for the current list. Drugs to avoid include Class IA and IC antiarrhythmics (procainamide, flecainide, propafenone when used chronically — note flecainide is used diagnostically in a monitored setting), tricyclic antidepressants, and large doses of propofol. Excess alcohol, particularly combined with a large meal, increases vagal tone and can unmask the pattern.

Catecholaminergic polymorphic VT (CPVT)

CPVT presents with exercise- or emotion-triggered polymorphic or bidirectional ventricular tachycardia in a structurally and electrically normal heart at rest. The resting ECG is normal. The primary gene is RyR2 (autosomal dominant, ~50–60%).

Nadolol is the preferred beta-blocker at maximum tolerated dose. Flecainide is added if symptoms persist — it reduces calcium leak through the RyR2 channel and significantly decreases residual events. LCSD is used for refractory cases. ICD is reserved for high-risk patients with the caveat that shocks themselves can trigger further VT through a catecholaminergic surge (pro-arrhythmic); programming to minimise inappropriate shocks is critical.

Competitive sport is generally restricted. All catecholaminergic stimulants — cocaine, amphetamines, ephedrine — are contraindicated.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) — also termed arrhythmogenic cardiomyopathy (ACM) when left ventricular-dominant variants are included — is diagnosed using the Padua criteria 2020 (Corrado et al.), which incorporate ECG features, imaging (cardiac MRI), histology, and genetics into major and minor categories.

The primary pathological genes are desmosomal: PKP2 (~50%), DSG2, DSC2, DSP, JUP, and DES. Desmosomal dysfunction leads to progressive fibrofatty replacement of RV myocardium, creating a scar-mediated substrate for re-entrant ventricular tachycardia. Exercise — particularly sustained endurance exercise — accelerates this fibrofatty process and is the most important modifiable risk factor. ARVC is a leading cause of sudden cardiac death in young athletes internationally.

Exercise restriction is the cornerstone of management and should be implemented as soon as the diagnosis is suspected, even before formal confirmation. Competitive sport is firmly restricted. Recreational exercise is individually assessed by an electrophysiologist — moderate-intensity activity may be permissible in some patients on optimal therapy; endurance training is generally not.

Medical management: Beta-blocker first-line; sotalol or amiodarone for symptomatic ventricular arrhythmias. ICD implantation for cardiac arrest survivors, sustained VT, or severe RV or LV dysfunction. Catheter ablation for recurrent VT. Heart failure management when RV or LV dysfunction develops; cardiac transplantation for end-stage disease.

Cascade screening of first-degree relatives includes ECG, Holter monitoring, and cardiac MRI. Even asymptomatic gene-positive relatives require regular monitoring — typically annual ECG and Holter, with periodic cardiac MRI — because phenotype penetrance is incomplete and progressive.

D. Australian operations

Australian Genetic Heart Disease Clinics — integrated services combining cardiologist, electrophysiologist, clinical geneticist, and genetic counsellor — operate at Royal Prince Alfred Hospital (Sydney), Royal Melbourne Hospital, St Vincent’s Hospital (Sydney), Royal Brisbane and Women’s Hospital, Sir Charles Gairdner Hospital (Perth), and Royal Adelaide Hospital. Referral from a GP is appropriate for any suspected IPAS.

The Australian Genetic Heart Disease Registry maintains a national clinical and research registry and coordinates molecular autopsy for unexplained sudden death under 50 through state coronial services. The coronial referral pathway for unexpected SCD under 50 should always include a request for molecular autopsy where available — it identifies a genetic cause in 30–40% of unexplained cases and enables family screening.

MBS items: Item 11700 or 11701 for in-clinic 12-lead ECG; items 11600/11602 for Holter monitoring; item 11722 for exercise stress test; item 55135 for echocardiogram; items 63335/63336 for cardiac MRI; item 73297 for IPAS genetic testing (Medicare-funded for eligible probands and first-degree relatives of a confirmed mutation carrier).

PBS access: Beta-blockers including propranolol are on the General Schedule; nadolol is available via TGA Special Access Scheme (SAS Category A) for IPAS indications, as it is not commercially available in Australia but is importable from New Zealand and the United Kingdom. Flecainide is available on Authority Required for CPVT. Amiodarone and sotalol are on the General Schedule for ventricular arrhythmia indications.

Driving restrictions: Austroads “Assessing Fitness to Drive” mandates driving restrictions for patients with prior arrhythmic events. Private licence holders are generally off driving for 6 months after cardiac arrest or sustained VT; ICD recipients may return after 4 weeks in the absence of further events. Commercial licence holders face stricter — often permanent — restrictions after major arrhythmic events. Advise patients and document the conversation.

Insurance implications: Under the Financial Services Council’s 2019 moratorium, patients may undergo genetic testing below specified coverage thresholds without mandatory disclosure to life insurers. This should be explained to patients before genetic testing proceeds, with referral to the genetic counsellor for detailed advice.

E. Special populations

Pregnancy and postpartum. LQT2 carries a particular risk in the first nine months postpartum — oestrogen withdrawal, sleep deprivation, and auditory triggers (infant crying) create a high-risk window. Beta-blocker therapy should be continued throughout pregnancy and the postpartum period after specialist review; most beta-blockers are compatible with breastfeeding. Sudden loud noise — an infant’s cry at night — is a recognised LQT2 trigger. Practical measures include keeping the phone on vibrate, placing the baby’s cot at a distance, and having a partner manage nighttime feeds. All postpartum women with known LQTS should have a close cardiology review within the first month postpartum.

Children and adolescents. Paediatric IPAS can present as unexplained seizures (misdiagnosed as epilepsy), childhood drowning, or fainting during sport. Jervell–Lange-Nielsen syndrome — autosomal recessive LQTS with congenital sensorineural deafness — should be considered in any deaf child with a history of syncope. The Paediatric & Congenital Cardiology department at major children’s hospitals manages IPAS in children.

Athletes. Athletic training can produce ECG changes that mimic Brugada (transient right precordial ST changes) or ARVC (T-wave inversions, RV ectopy) — differentiation from true IPAS requires specialist assessment using the international athlete ECG criteria (Seattle criteria and their updates). Conversely, ARVC is a leading cause of sudden death in competitive athletes and must not be dismissed as an athletic heart variant.

Aboriginal and Torres Strait Islander populations. Limited data exist on IPAS prevalence in Indigenous Australian populations. Cardiomyopathy secondary to rheumatic heart disease and other acquired conditions contributes substantially to cardiovascular mortality. Screening should be informed by the individual’s clinical and family history rather than population-wide assumptions.

When to escalate

Refer to specialist cardiology or attend emergency immediately when:

Syncope during swimming, exercise, emotional shock, or an auditory startle — particularly if abrupt with no prodrome
Syncope in a first-degree relative of a known IPAS patient
QTc >500 ms on resting ECG — even without symptoms
Spontaneous Brugada Type 1 coved pattern on ECG — elective cardiology referral; emergency if concurrent fever or haemodynamically unstable
Exercise-induced syncope or witnessed cardiac arrest in a young person — emergency
Unexplained syncope with a family history of sudden death under 50 — urgent cardiology referral
Resuscitated cardiac arrest — emergency department and immediate specialist review
Sustained palpitations with ECG documentation of VT — emergency
Known IPAS patient with fever not responding promptly to paracetamol (Brugada) — emergency department
Any decision regarding sport restriction, ICD implantation, or LCSD — specialist electrophysiology

What this article is and is not

This is general health information drawn from current clinical resources — the ESC 2022 ventricular arrhythmia guidelines, HRS/EHRA/APHRS 2013 consensus, CSANZ Genetic Heart Disease Position Statement, Therapeutic Guidelines, and the Australian Genetic Heart Disease Registry. It is not personal medical advice and does not create a doctor–patient relationship. Decisions about specific management — including drug choices, ICD implantation, sport restriction, and genetic testing — are made with your own GP, cardiologist, and genetic counsellor.

For Australian consumer resources: HealthDirect — Sudden cardiac death, Heart Foundation Australia, Australian Genetic Heart Disease Registry.

For cardiac emergency: call 000.

Sources cited

Frequently asked questions

How do I know if my fainting episode could be heart-related rather than a simple faint?

Vasovagal syncope — the common faint — has a typical pattern: prolonged standing, heat, pain, or emotional stimulus produces a warning of nausea, sweating, and light-headedness before blackout, with rapid recovery. Cardiac syncope is more abrupt with little or no warning, often during or immediately after exercise, during emotional shock or a sudden loud noise, during swimming, or from sleep. Cardiac syncope may be followed by chest pain or palpitations, and bystanders may observe seizure-like movements (due to cerebral hypoperfusion). A family history of sudden death under 50, unexplained drowning, or childhood seizures significantly raises the probability of an inherited arrhythmia syndrome.
My parent died suddenly in their 40s. Should I have a cardiac assessment?

Yes — unexplained sudden death under 50 in a first-degree relative is a strong indication for cardiac assessment of all first-degree family members. This typically includes a 12-lead ECG with QTc measurement, a detailed family pedigree going back three generations, and a specialist cardiology referral. In some cases, an exercise stress test, ambulatory ECG, or cardiac MRI is indicated. Where a genetic cause has been identified in the deceased (via molecular autopsy), targeted genetic testing of relatives can identify who carries the mutation even before symptoms develop. Cascade screening aims to find affected relatives before a life-threatening event.
What is long QT syndrome and which medications do I need to avoid?

Long QT syndrome is a genetic condition in which the heart's electrical recovery phase — measured as the QT interval on ECG — is abnormally prolonged. This can degenerate into a specific dangerous arrhythmia called torsades de pointes, which can cause cardiac arrest. The main management in general practice is avoiding QT-prolonging drugs — the CredibleMeds database (crediblemeds.org) lists hundreds of medications with varying risk. High-risk examples include macrolide antibiotics (clarithromycin, azithromycin, erythromycin), fluoroquinolones, ondansetron particularly IV, methadone, haloperidol and other antipsychotics, citalopram above 20 mg, and many antifungals. A beta-blocker — usually nadolol or propranolol — is the mainstay of medical treatment.
Can I still exercise with Brugada syndrome or ARVC?

It depends on the specific syndrome. Brugada syndrome does not preclude recreational exercise in most cases — the main triggers are fever, certain drugs, large alcohol intake, and sleep. However, competitive sport is assessed case-by-case with an electrophysiologist. ARVC is different: endurance exercise accelerates the fibrofatty progression of the condition and significantly increases arrhythmia risk. Competitive sport is firmly restricted in ARVC, and even recreational endurance exercise (running, cycling, swimming at high intensity) is individually assessed. CPVT, triggered specifically by catecholamines during exercise and emotion, also requires careful sport restriction. An electrophysiologist should make all sports and activity recommendations for inherited arrhythmia patients.
How does cascade family screening for inherited heart rhythm conditions work in Australia?

When a person is diagnosed with an inherited arrhythmia syndrome, their first-degree relatives — parents, siblings, and children — are offered screening. The process starts with genetic counselling before any testing, so family members understand the implications. If a specific genetic mutation has been identified in the proband, relatives undergo targeted genetic testing; carriers are then followed clinically even if asymptomatic. If no mutation has been found, phenotypic screening uses ECG, exercise stress test, Holter monitoring, and cardiac MRI depending on the syndrome. The Australian Genetic Heart Disease Registry coordinates this process through specialist clinics in most major cities. Cascade screening has identified life-saving diagnoses in asymptomatic relatives.

Source quality

Sources grouped by evidence tier. AU primary tier first; international where AU is silent or lagging; named-author reconstruction where guidelines have not yet caught up. How tiers work.