Inherited (congenital)
- A gene change you are born with
- Runs in families
- Often found young
- Treated for life; relatives tested
Names & Terms You Will Hear
Plain-language meanings for the terms your care team may use.
| Term | Meaning |
|---|---|
| Long QT syndrome (LQTS) | A heart rhythm problem. The heart takes too long to recharge after each beat. This raises the risk of a dangerous fast rhythm. |
| QT interval | The time on an ECG from the start of the heartbeat to the end of the recharge phase. A long QT is the warning sign. |
| QTc (corrected QT) | The QT interval adjusted for heart rate, so it can be compared fairly. This is the number your doctor watches. |
| Torsades de pointes | French for 'twisting of the points.' A fast, twisting heart rhythm that long QT can set off. It can cause fainting or sudden death. |
| Inherited (congenital) LQTS | The type you are born with. It runs in families and comes from a gene change. Often found in children or young adults. |
| Acquired (drug-induced) LQTS | The type caused by a medicine, a low mineral level, or another illness. It often goes away once the cause is fixed. |
| Channelopathy | A disease of the tiny channels that move minerals in and out of heart cells. Long QT is one kind of channelopathy. |
| Sudden cardiac arrest (SCA) | When the heart suddenly stops pumping. Without fast CPR and a shock from an AED, it is fatal in minutes. |
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
If someone collapses: Call 911. Start CPR. Use an AED.Long QT syndrome can cause sudden cardiac arrest. If a person collapses and is not breathing normally, act fast: (1) Call 911. (2) Push hard and fast in the center of the chest - about 2 inches deep, 100 to 120 pushes a minute, to the beat of the song 'Stayin' Alive.' (3) Send someone for an AED and turn it on - it speaks every step and will not shock a normal heart. The PulsePoint app shows the nearest AED.
What Is Long QT Syndrome?
- Long QT syndrome (LQTS) is a problem with the heart's electrical recharge. After each beat, heart cells reset by moving minerals like potassium and sodium in and out. In LQTS, that reset takes too long.
- Doctors measure the recharge time on an ECG as the QT interval. Adjusted for heart rate, it is called the QTc. A QTc of 450 ms or less is normal in most people.
- A QTc of 451 to 480 ms is borderline. A QTc over 480 ms is prolonged. A QTc over 500 ms carries the highest risk of a dangerous rhythm.
- There are two main paths to a long QT. The inherited type comes from a gene change you are born with. The acquired type is caused by certain medicines, low blood minerals, or other illnesses.
- The inherited type is not rare. It affects about 1 in 2,000 people. Many never know they have it. They find out only when a relative is diagnosed, or when a fainting spell leads to testing.
- Most people with LQTS feel completely normal day to day. The danger shows up in moments - during exercise, a sudden scare, or sleep - when a long QT can trigger torsades de pointes.
How the QTc number guides your care
| QTc range | What it means | What usually happens next |
|---|---|---|
| 450 ms or less | Normal recharge time | Reassurance; recheck if symptoms or family history. |
| 451 to 480 ms | Borderline - a gray zone | More testing: repeat ECG, exercise test, sometimes gene testing. |
| 481 to 500 ms | Prolonged | Treatment is usually started; avoid QT-prolonging drugs. |
| Over 500 ms | High risk | Treatment plus close follow-up; an ICD is considered for some. |
Inherited vs acquired long QT - the two paths at a glance
Acquired (drug-induced)
- Caused by a medicine or low minerals
- Can appear at any age
- Usually reversible
- Fix the cause; the QT often normalizes
Why It Matters
- A long QT itself causes no symptoms. The risk is what it can lead to: torsades de pointes, a fast and twisting rhythm that stops the heart from pumping blood.
- When torsades strikes, the brain loses blood flow within seconds. The result is sudden fainting (syncope). Most torsades episodes stop on their own and the person wakes up.
- But some episodes do not stop. The heart starts to quiver instead of pump. This is called ventricular fibrillation, and it leads to sudden cardiac arrest. That is why LQTS can be deadly.
- For some families, the first sign of LQTS is the sudden loss of a young, healthy relative. That is why finding it early and treating it saves lives.
- The good news: LQTS is very treatable. With the right beta-blocker, trigger avoidance, and - for higher-risk patients - a defibrillator, the yearly risk of a deadly event drops dramatically.
- Because it can run in families, one diagnosis matters for everyone related. Testing relatives can find silent carriers and protect them before any symptom appears.
Risk Factors
Knowing your personal risks helps your care team take extra precautions.
| Risk Factor | Why It Increases Risk |
|---|---|
| A family history of LQTS | The inherited type is passed down. A parent, sibling, or child with LQTS means you should be tested too. |
| A family member who died young and suddenly | A young relative who died with no clear cause can be a sign. So can a drowning in a strong swimmer. These may point to LQTS in the family. |
| Fainting during exercise, scares, or strong emotion | Fainting with a clear trigger like these is a red flag. Ordinary fainting from standing up is usually harmless; this kind is not. |
| Certain medicines that lengthen the QT | Many common drugs can lengthen the QT. The list includes some antibiotics, anti-nausea drugs, and mood medicines. They can unmask or worsen a long QT. |
| Low potassium or magnesium | These minerals run the heart's recharge. Low levels - from vomiting, diarrhea, or water pills - lengthen the QT. |
| Female sex after puberty | Women tend to have a slightly longer QT than men and face higher risk in some inherited types, especially after childbirth. |
| Being born deaf in a rare form | A rare inherited type (Jervell and Lange-Nielsen) pairs a very long QT with deafness from birth and needs close care. |
LQT1 - the exercise type (KCNQ1 gene)
- The most common inherited type. It comes from a change in the KCNQ1 gene, which controls a key potassium channel.
- The classic trigger is exercise, and swimming is especially risky. An unexplained drowning in a strong swimmer can be a clue to LQT1 in a family.
- Beta-blockers work very well in LQT1. Nadolol is often the preferred choice.
- Activity guidance is personalized. Many patients are advised to avoid swimming alone and to be cautious with competitive sports.
LQT2 - the startle type (KCNH2 gene)
- The second most common type, from a change in the KCNH2 gene and another potassium channel.
- The classic triggers are sudden noise and emotional startle - an alarm clock, a ringing phone, or a fright. Events can also cluster after childbirth.
- Simple steps help: move alarms and loud phones out of the bedroom and reduce sudden startles where you can.
- Beta-blockers help, and keeping potassium in normal range is especially important in this type.
LQT3 - the rest-and-sleep type (SCN5A gene)
- Less common, from a change in the SCN5A gene that affects a sodium channel.
- The pattern is the opposite of LQT1: events tend to happen at rest, during sleep, or when the heart rate is slow.
- Beta-blockers help less in LQT3. A sodium-channel medicine such as mexiletine may be added when the QTc stays over 500 ms.
- An ICD is considered more readily in higher-risk LQT3 patients because the protection from medicine alone is lower.
Treatment Options
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
- Beta-blockers are the foundation of treatment for inherited LQTS. They blunt the surges of adrenaline that trigger dangerous rhythms. Nadolol and propranolol are the preferred choices because they work steadily around the clock.
- Beta-blockers must be taken every day, even when you feel fine. Skipping doses is itself a known trigger for events. Never stop suddenly without talking to your doctor.
- For acquired (drug-induced) LQTS, the main treatment is to stop the offending medicine and to correct any low potassium or magnesium. The QT usually returns to normal once the cause is removed.
- For LQT3 (the SCN5A type), a sodium-channel medicine such as mexiletine may be added when the QTc stays over 500 ms. It helps shorten the QT in this specific type.
- An implantable defibrillator (ICD) is added for the highest-risk patients. These are people who have already survived a cardiac arrest, or who faint even on a beta-blocker. The ICD watches every beat. If a deadly rhythm strikes, it gives a life-saving shock.
- A few patients keep having events even with an ICD and medicine. For them, a surgery called left cardiac sympathetic denervation (LCSD) can cut the nerves that drive the dangerous surges.
- Avoiding QT-prolonging drugs and keeping minerals normal is part of treatment for everyone with LQTS, inherited or acquired.
Common medicines that can lengthen the QT - always have new drugs checked
| Drug group | Examples you may know | Why it matters |
|---|---|---|
| Some antibiotics | Azithromycin, erythromycin, levofloxacin | Common for infections; can add to a long QT. Safer options usually exist. |
| Anti-nausea drugs | Ondansetron (Zofran), promethazine | Often given for stomach bugs - the same illness can also drop your minerals. |
| Some antidepressants | Citalopram, escitalopram, amitriptyline | Widely used; dose and combination matter. Do not stop on your own - ask first. |
| Some heart-rhythm drugs | Sotalol, dofetilide, amiodarone | Used for other rhythm problems; need careful QT monitoring in LQTS. |
| Water pills (diuretics) | Furosemide, hydrochlorothiazide | Lower potassium and magnesium, which lengthens the QT indirectly. |
Before any new medicine, check it. Many common drugs lengthen the QT. Before filling a new prescription - or buying an over-the-counter medicine - look it up at CredibleMeds.org or call our office. Tell every doctor, dentist, and pharmacist that you have long QT syndrome.
Comfort Measures at Home (No Medication Needed)
These simple steps support healing and ease symptoms. Use them alongside any medication your doctor prescribes.
- Carry an up-to-date list of your medicines and your LQTS diagnosis. Show it at every pharmacy and before any new prescription, dental visit, or surgery.
- Check every new medicine - prescription or over-the-counter - against the QT-drug list at CredibleMeds.org before you take it.
- Keep potassium and magnesium in normal range. Stay hydrated, and call your office promptly if you have a stomach bug with vomiting or diarrhea.
- Follow your activity plan. Many patients with LQT1 are advised to avoid swimming alone and competitive sports; your doctor will personalize this for your type.
- For LQT2, lower sudden startles where you can - move alarm clocks and loud phones out of the bedroom, since abrupt noise is a known trigger.
- Make sure family and close friends know your diagnosis and how to start Hands-Only CPR and use an AED. Their quick action is your strongest backup.
- Treat fevers promptly and avoid known triggers, because fever and some illnesses can lengthen the QT further.
Risks, Benefits, and Alternatives
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
Every choice has trade-offs. Use this table to start the shared decision conversation with your care team.
| Option | Risks | Benefits | Alternatives |
|---|---|---|---|
| Beta-blocker (nadolol or propranolol) | Tiredness, slow heart rate, cold hands, or wheezing in some people. Must be taken daily; missed doses raise risk. | Greatly lowers the chance of fainting and sudden death, especially in LQT1 and LQT2. First-line for almost everyone. | A different beta-blocker, adding mexiletine in LQT3, or an ICD for higher-risk patients. |
| Implantable defibrillator (ICD) | Surgery and lead risks; possible infection; rare unnecessary shocks. Does not stop the abnormal rhythm from starting. | Delivers a life-saving shock within seconds if a deadly rhythm occurs. The strongest protection for the highest-risk patients. | Beta-blocker alone for lower-risk patients; left cardiac sympathetic denervation surgery. |
| Left cardiac sympathetic denervation (LCSD) | A surgery with usual surgical risks; can cause a drooping eyelid or dry hand on one side. Does not replace an ICD in highest-risk cases. | Cuts the nerve surge that triggers events. Useful when medicines and an ICD are not enough, or beta-blockers are not tolerated. | Higher-dose or different beta-blocker; ICD; strict trigger avoidance. |
| Avoid QT-prolonging drugs and fix low minerals | Requires constant attention; some needed medicines must be swapped for safer ones with your doctor's help. | Removes a major, preventable trigger. The core treatment for acquired LQTS and a must for everyone with LQTS. | None - this is a baseline step for all patients, used alongside other treatments. |
Common Misconceptions
| Myth | Reality |
|---|---|
| Long QT only matters if I have symptoms. | Many people with LQTS feel perfectly well right up until a dangerous event. A normal-feeling day does not mean low risk. Treatment is about prevention. |
| A normal ECG once means I am in the clear. | The QT can vary from day to day and can look normal at times. Doctors may repeat the ECG, use exercise testing, or check genes to be sure. |
| If it is inherited, nothing can be done. | Inherited LQTS is highly treatable. Beta-blockers, trigger avoidance, and - when needed - an ICD lower the risk of sudden death dramatically. |
| Only heart medicines can lengthen the QT. | Many everyday drugs can lengthen the QT. The list includes some antibiotics, anti-nausea drugs, and mood medicines. Always have a new medicine checked first. |
| Fainting is harmless - everyone faints sometimes. | Ordinary fainting from standing up is usually harmless. But fainting during exercise, a scare, or strong emotion can be a sign of a deadly rhythm and must be checked. |
| My relatives are fine, so they do not need testing. | LQTS can be silent. A relative can carry the same gene change with a normal-looking ECG. Family testing finds hidden carriers and protects them. |
Possible Complications
Knowing what can go wrong helps you spot problems early. Most complications are uncommon, especially with treatment.
| Where / What | What Can Happen |
|---|---|
| Heart rhythm | Torsades de pointes, a fast twisting rhythm that can cause sudden fainting. |
| Heart rhythm | Ventricular fibrillation, a quivering rhythm that stops blood flow and causes cardiac arrest. |
| Brain | Fainting (syncope) and, if blood flow is cut off long enough, seizures or brain injury. |
| Whole body | Sudden cardiac arrest and death if a deadly rhythm is not stopped by CPR and an AED in minutes. |
| Daily life | Anxiety and activity limits; some sports and jobs may need to be adjusted for safety. |
| Newborns and children | In a rare severe inherited form, very long QT can appear in infancy with deafness and needs early specialist care. |
Points to Know
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
If you remember nothing else, remember these key points.
- The QT interval is the heart's recharge time. A long QTc - especially over 500 ms - raises the risk of a dangerous rhythm.
- LQTS can be inherited (a gene change you are born with) or acquired (from medicines or low minerals). Both are treatable.
- The danger is torsades de pointes, which can cause fainting or sudden cardiac arrest. Treatment is about preventing it.
- Beta-blockers like nadolol or propranolol are first-line. Take them every day; missing doses is itself a trigger.
- Avoid QT-prolonging drugs and keep potassium and magnesium normal. Check every new medicine before you take it.
- Higher-risk patients may need an implantable defibrillator (ICD) for an extra layer of protection.
- Because it runs in families, your relatives should be tested - even if they feel completely well.
- Learn Hands-Only CPR and how to use an AED, and make sure your family does too.
When to Call Us — and When to Call 911
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
If you are not sure, call. We would rather hear from you twice than miss a real problem.
- Call 911 now if someone collapses, is not breathing normally, or has no pulse. Start Hands-Only CPR and send for an AED.
- Call 911 for fainting that happens during exercise, a sudden scare, or strong emotion - this can signal a dangerous rhythm.
- Call our office promptly if you faint, nearly faint, or feel your heart racing or fluttering.
- Call before starting any new medicine - including over-the-counter drugs - so we can check it against the QT-drug list.
- Call if you have a stomach illness with vomiting or diarrhea, since low potassium or magnesium can lengthen your QT.
- Call if you cannot tolerate your beta-blocker or have missed several doses, so we can adjust your plan safely.
- Tell us if a young relative has fainted unexplained or died suddenly, so we can arrange family testing.
Office: (727) 943-5200
Trusted Resources
Independent, evidence-based pages we recommend for deeper reading.
- Cleveland Clinic - Long QT Syndrome — Plain-language overview of QT prolongation, triggers, and treatment.
- Mayo Clinic - Long QT Syndrome — Inherited vs acquired LQTS, symptoms, and beta-blocker therapy.
- MedlinePlus Genetics - Long QT Syndrome — NIH/NLM explainer of the genetic basis (LQT1/2/3) and inheritance.
- CredibleMeds - QT Drug Lists — The trusted list of medicines that lengthen the QT - check every new drug here.
- SADS Foundation — Patient and family support for inherited arrhythmias, including LQTS and family screening.
- AHA Hands-Only CPR — A 60-second video on how to save a life with chest compressions.
- PulsePoint Respond app — Find the nearest AED and get alerted to nearby cardiac arrests.
- Our Sudden Cardiac Arrest guide — Companion guide on recognizing arrest and acting fast with CPR and an AED.
- Our Fainting (Syncope) guide — When fainting is harmless and when it is a warning sign.
- Our Pacemakers and ICDs guide — How an implantable defibrillator watches your heart and delivers a life-saving shock.
Sources Used to Build This Guide
- Cleveland Clinic — Long QT Syndrome [clinical] — Patient overview of QT prolongation, fainting/torsades risk, triggers, and treatment.
- Mayo Clinic — Long QT Syndrome [clinical] — Patient overview of inherited vs acquired LQTS, symptoms, and beta-blocker therapy.
- 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and Prevention of SCD [guideline] — Guideline source for channelopathy management, beta-blockers, ICD, and activity counseling.
- MedlinePlus Genetics — Long QT Syndrome [clinical] — NIH/NLM patient explainer of the genetic basis (LQT1/2/3) and inheritance.
