The majority of patients that have a LQTS may not present with any signs and symptoms. These cases are incidentally discovered during routine electrocardiogram. Patients who are symptomatic of LQTS may commonly present with the following signs and symptoms:

• Fainting: This is the most common of symptomatology associated with LQTS. Fainting spells or syncope happens when the heart temporarily beats erratically which are often times triggered by severe emotional or physical stress.
• Seizure: This is a result of the inadequate blood supply to the brain from an incompetently beating heart. 
• Sudden death: LQTS patients may progress to dysrhythmia which may succumb to sudden death if no electric defibrillation is done soon.

• Sudden Infant Death Syndrome

  […] including subarachnoid bleed Structural heart disease For syncope or sudden death in the young: Sudden infant death syndrome (SIDS) Drug-induced QT prolongation Vasovagal syncope (orthostatic hypotension) Anomalous coronary artery Familial ventricular [centogene.com]

  Abstract Prolongation of the QT interval is the cause of about 10% cases of sudden infant death syndrome (SIDS) in newborns but it is also responsible for about 5% of sudden deaths in adults. [omicsonline.org]

  Recent postmortem molecular screening surveys have shown that 10 to 12% of sudden infant death syndrome (SIDS) cases were potentially related to congenital long QT syndrome. Current SIDS etiological surveys fail to diagnose LQTS. [hal.archives-ouvertes.fr]

  Relation with sudden infant deaths Sudden infant death syndrome (SIDS) remains the leading cause of sudden death during the first year of life in the western world. [ncbi.nlm.nih.gov]

• Disability

  Please enable JS and disable any ad blocker [lequotidiendumedecin.fr]

  ADNP- Related Intellectual Disability and Autism Spectrum Disorder Anke Van Dijck, Céline Helsmoortel, Geert Vandeweyer, and Frank Kooy. Initial Posting: April 7, 2016. [ncbi.nlm.nih.gov]

• Unconsciousness

  If someone is unconscious and not breathing, call 999 and start cardiopulmonary resuscitation (CPR) until medical help takes over. If there’s someone nearby, ask them to find a public access defibrillator. [bhf.org.uk]

  She was intermittently unconscious and unable to give history. The monitor showed intermittent polymorphic ventricular tachycardia. [hqmeded-ecg.blogspot.com]

  Whether the unconsciousness was due to self-limiting arrhythmias, hypoglycemia, or other causes is unknown. Prolonged OGTT and Continuous Blood Glucose Measurements. [doi.org]

• Developmental Delay

  She is developmentally delayed without autism. She recently had her first episode of torsade de pointes associated with febrile illness and hypoglycemia. [ncbi.nlm.nih.gov]

  LQT8 is more strikingly multi-systemic, leading to congenital heart disease, syndactyly (depending on the mutation), immune deficiency, intermittent hypoglycemia, developmental delay, and autism (Timothy syndrome; TS). [nature.com]

• Agonal Respiration

  We encountered a 15-year-old female student with LQTs who had prolonged QTc and multiple episodes of syncope or agonal respiration during sleep. [ncbi.nlm.nih.gov]

• Tachycardia

  LQTS is a cardiac electrophysiologic disorder, characterized by changes in the electrocardiogram (ECG), such as QT prolongation, T-wave abnormalities, accompanied by the ventricular tachycardia torsade de pointes (TdP). [centogene.com]

  A short-lived episode of sinus tachycardia during brick standing from a supine position provides a similar diagnostic value to exercise testing in the diagnosis of LQTS. [thecardiologyadvisor.com]

  The patient received an implantable cardioverter-defibrillator due to polymorphic ventricular tachycardia under beta-blocker therapy. [ncbi.nlm.nih.gov]

  […] presenting with: general malaise Palpations Angina pectoris Syncopes Increased sweating. 6.1 Complications Ventricular tachycardias that are untreated can result in ventricular fibrillation and ultimately in cardiac arrest. 7 Diagnostics Diagnosis is [flexikon.doccheck.com]

  Torsades de pointes ventricular tachycardia is a specific type of ventricular tachycardia that occurs in people who have a particular disorder of the heart's electrical activity called long QT syndrome. [msdmanuals.com]

• Heart Disease

  An additional 16 carriers were identified, including 2 with structural heart disease: one with cardiomyopathy resulting in sudden death and the other with congenital heart disease. For all carriers of this variant, the average QTc was 475 ms (±40). [ncbi.nlm.nih.gov]

  Patreon Help with Search Health Conditions and Diseases Cardiovascular Disorders Heart Disease Arrhythmia Long QT Syndrome 0 Long QT syndrome is a cardiac ion channel disease that predisposes its carriers to lethal ventricular arrhythmias. [curlie.org]

  Major clinical findings in LQTS-affected patients include the following: Abnormal QT values on ECG Prolonging of QT segments by specific drugs Hypokalemia Certain neurologic conditions including subarachnoid bleeding Structural heart disease Determination [centogene.com]

  Treatments include: We treat a full range of hereditary heart and blood vessel diseases: Clinical trials for inherited heart disease often test new medications. [familyheart.stanford.edu]

• Palpitations

  These episodes may lead to palpitations, fainting, and sudden death due to ventricular fibrillation. Episodes may be provoked by various stimuli, depending on the subtype of the condition. [ncbi.nlm.nih.gov]

  How can I find out exactly what is causing my palpitations? Consult your doctor. [crediblemeds.org]

  These episodes lasted for a few minutes and were proceeded by palpitations and chest pain. The patient’s past medical history was unremarkable except for well-controlled hypertension with amlodipine. [innovationsincrm.com]

• Suggestibility

  Homology modeling suggested that secondary structure was altered in the mutant SF compared with the wild-type (WT) SF. [ncbi.nlm.nih.gov]

• Anger

  The most common types are: LQTS 1: Exercise (especially swimming) or emotional stress LQTS 2: Extreme emotions including fright, anger, pain, or surprise LQTS 3: Arrhythmias triggered by a slow heart rate while asleep Acquired LQTS is much less common [medstarwashington.org]

  Event triggers of long QT syndrome An event can be triggered by: exercise being startled by a loud noise, such as a horn, ringing telephone or alarm clock exams, tests or other stressful situations anger or crying. [betterhealth.vic.gov.au]

  People with LQTS often show a prolonged Q-T interval during exercise, intense emotion (such as fright, anger, or pain), or as a reaction to a loud or startling noise. [texasheart.org]

  Possible symptoms of long QT syndrome include: fainting, which can be triggered by exercise (especially swimming) and emotions (such as surprise from a loud noise, excitement, anger or fear); making loud gasping noises during sleep or when waking from [mydr.com.au]

• Irritability

  This list includes drugs that can stimulate and irritate the heart by causing adrenaline-like effects. You must always check with your GP or cardiologist before taking any new medication, as this list will change with time. [sads.org.uk]

  The patient subgroup reported symptoms like extreme cravings for sweets, irritability, weakness, dizziness, shakiness, depression, or mood swings and anxiety or nervousness as well as night awakening and severe night sweats correlating to the exact time [doi.org]

The following test and diagnostic modalities are implored among patients with high suspicion of Long QT syndrome:

• Electrocardiogram (ECG): This test may be taken at rest or during a treadmill stress test. ECG may be taken while standing to increase sympathetic tone where QT interval prolongation is usually observable [5]. A positive standing test may continually show a prolonged QT after resting and even when the heart returns to normal rate [6]. 
• Ambulatory ECG monitoring: This test is also called Holter monitoring which is a portable device attached to the patient to monitor heart rhythm within an extended period of up to 24 hours. Prolonged QT intervals may then be spotted by the attending cardiologist during the whole day stretch of cardiac monitoring.
• Event ECG monitoring: This is similar to the Holter monitor which may be used in a period of days and weeks. An access button may be provided for the patient to activate in case of any cardiac event to record the actual rhythm real-time for analysis. 
• A diagnostic criteria for the identification of risk for LQTS was developed which includes parameters like QT interval, presence of torsade de pointe and familial history of LQTS [7].

• Hypoglycemia

  However, syncope could also be a sign of hypoglycemia, and our study suggests that the KCNQ1 LQTS patients also have symptoms related to hypoglycemia. [doi.org]

  […] may explain some cases of "essential" reactive hypoglycemia. [ncbi.nlm.nih.gov]

• Prolonged QT Interval

  An electrocardiogram (ECG) reveals a QTc (QT) interval of 480 ms. How should this hospitalized patient’s prolonged QT interval be managed? Overview Patients with a prolonged QT interval on routine ECG present an interesting dilemma for clinicians. [the-hospitalist.org]

  Definition A heart disorder characterized by a prolonged QT interval on the ECG and polymorphic ventricular arrhythmias. [uniprot.org]

  […] is characterized by episodes of fainting (syncope) and varying degree of ventricular arrhythmia as indicated by the prolonged qt interval. [icd9data.com]

  Diagnosis The EKG finding of an inherited LQTS is typically a prolonged QT-interval on the 12-lead electrocardiogram. [washingtonhra.com]

  Romano-Ward syndrome: Romano-Ward syndrome is the most common form of congenital long QT syndrome, which purely affects cardiac ion channels to produce prolonged QT interval. [c-r-y.org.uk]

• ST Elevation

  "Spiked helmet" is a type of ST elevation, which is generally observed in critically ill patients and associated with very poor prognosis. [ncbi.nlm.nih.gov]

  Seizure Cardiac arrest and death : secondary to ventricular fibrillation Differential Diagnosis Vasovagal syncope Hypertrophic Cardiomyopathy Brugada syndrome: autosomal dominant disorder characterized by RBBB and ST elevation on anterior leads of EKG [pedclerk.bsd.uchicago.edu]

  The type 2 ST-segment elevation has a saddleback appearance with a high takeoff ST-segment elevation of >2 mm, a trough displaying >1-mm ST-elevation followed by a positive or biphasic T. [doi.org]

• Short QT Interval

  […] peaked T waves Failure of the QT interval to increase as the heart rate slows Very short QT (< 300ms) with peaked T waves in two patients with SQTS Digoxin Short QT interval due to digoxin (QT 260 ms, QTc 320ms approx) Digoxin produces a relative shortening [lifeinthefastlane.com]

  Two cases of short QT interval. Pacing Clin Electrophysiol. 2007; 30(12): 1522–1526. pmid:18070308. View Article PubMed/NCBI Google Scholar 14. Holbrook M, Malik M, Shah RR, Valentin JP. [journals.plos.org]

• 2:1 Atrioventricular Block

  Permanent pacemaker insertion for long QT syndrome is discouraged apart from younger patients exhibiting 2:1 atrioventricular block. [ncbi.nlm.nih.gov]

  B: atrioventricular block 2:1. C: self-limited torsade de pointes. [revespcardiol.org]

  Timothy syndrome may include a functional 2/1 atrioventricular block, due to an exceedingly long QT interval5,19,48. [romanianjournalcardiology.ro]

• Torsades De Pointes

  It is important to note that symptoms usually occur without warning and are caused by a very fast heart rhythm called torsade de pointes. [ucsfbenioffchildrens.org]

  KEYWORDS: Digenic mutation; Epinephrine test; Long QT syndrome; Torsade de pointes [ncbi.nlm.nih.gov]

  The prolongation of the q-t interval combined with torsades de pointes manifests as several different forms; some may be acquired or congenital; some may lead to serious arrhythmia and sudden cardiac death Prolongation of q-t interval combined with torsades [icd9data.com]

  Torsade de pointes In LQTS, QT prolongation can lead to polymorphic ventricular tachycardia, or torsade de pointes, which itself may lead to ventricular fibrillation and sudden cardiac death. [emedicine.com]

• T Wave Alternans

  We report a case with type 3 congenital long QT syndrome, who exhibited a sudden paradoxical QT-interval prolongation during a progressive increase in heart rate, which exacerbated T-wave alternans. © 2014 Wiley Periodicals, Inc. [ncbi.nlm.nih.gov]

  The morphology of the T wave is often useful for the diagnosis, and the precordial leads are especially informative when they reveal biphasic or notched T waves. 30 T-wave alternans in polarity or amplitude ( Figure 1 ), when observed, is diagnostic as [ahajournals.org]

  Other risk factors in LQTS include syncope (or “seizure activity”), a QTc interval >500ms, functional 2:1 AV block due to prolonged ventricular repolarization, notched T waves, macroscopic T-wave alternans, postpubertal females, and LQT2 or LQT3 genotype [thecardiologyadvisor.com]

The main treatment options in LQTS are beta-blockers, permanent pacing, stellectomy, implantable cardioverter-defibrillator (ICD), or a combination [8]. The use of anti-arrhythmic drugs like beta-blockers [9] in combination with mexiletine slows down heart rate and reduces the risk of cardiac dysrhythmias. Patients who presents with recurrent syncope in the face of an LQTS may benefit from theophylline and hydralazine medications that may improve these signs of bradycardia.

A healthy diet rich in potassium and omega 3 fatty acids (fish oil) may stabilize abnormal cardiac rhythms in high risk individuals. Strenuous exercise should be avoided. 

The prognosis of LQTS with current treatment with the anti-arrhythmic medications like beta blockers is good. Episodes associated with torsade de pointes are usually self-limiting in patients with LQTS where only 4-5% may conclude with a fatal cardiac event.

Patients with recurrent bouts or episodes of aborted cardiac arrest and other cardiac events despite medications have a very high risk for sudden cardiac death. The total deaths in the US caused by LQTS reaches 4000 in number per year. The presence of neurologic deficits in aborted cardiac arrest after a successful resuscitation may further complicate the prognosis of long QT syndrome in patients.

Complications

Patients suffering from long QT intervals may progress to life threatening complications after an emotional induction. The more common LQTS complications are identified as follows:

• Torsades de pointes: Otherwise referred to as the “twisting of the points”. This type of arrhythmia is caused by the rapid depolarization of the ventricles causing the electrocardiogram readings to appear twisted. The uncontrolled rapid contraction of the heart makes it an inefficient pump to supply the brain with adequate blood supply that may cause sudden fainting. 
• Ventricular fibrillation: This condition can virtually complicate from torsade de pointes characterized as a rapid ventricular contraction that later leads to quivering of the heart muscles and is unable to pump out any blood. When ventricular fibrillation is not defibrillated soon enough, this may lead to brain death or eventual death if left unchecked. 

The long QT syndrome is either inherited or acquired. There are at least two forms of inherited that has been identified so far:

• Romano-Ward syndrome: This LQTS form is the more common genetic variant that occurs in people who inherit a single genomic variant from one of his parent.
• Jervell and Lange-Nielsen syndrome: This LQTS is more severe and rare than the other variant. This variant is inherited from both parents and are usually eminent in children who are born deaf.

Majority of acquired LQTS is induced by the intake of certain medications that tend to prolong the QT intervals among patients. These medications include certain antibiotics, antidepressants, cholesterol-lowering agents, diuretics, antipsychotics, antifungal medications, antihistamine, oral hypoglycemic and some heart medications. Researchers have identified that people who suffer from drug induced LQTS are genetically predisposed or at risk of LQTS when exposed to certain drugs.

In the United States, the incidence of long QT syndrome is estimated to reach a ratio of 1 case in 10,000 population. This incidence ratio and prevalence rate for LQTS are similar internationally. Female patients are more predisposed with a more than 2:1 ratio compared to the male counterpart. Although young men carries a higher mortality rate than women for LQTS.

Women during menopause are more predisposed to LQTS with cardiac events in up to 2 to 8 folds increase compared to female counterparts that are still in their reproductive years [1]. The more common cardiac events associated with LQTS in adolescents and adults includes syncope, aborted cardiac arrest, and sudden cardiac deaths.

In patients with LQTS that is inherited, primary defects in the cardiac sodium, potassium and calcium channel are the common pathophysiologic defect seen. Ion channels may inherently be obstructed or may cause an opening delay causing an imbalance in the ionic gradients of the heart.

Channel protein defects in the caveolae have been recognized in the increased sodium flux type of LQTS found in LQTS3 genetic phenotype [2]. Functional studies have demonstrated that late sodium channel dysfunction associated with LQTS is implicated in sudden infant death syndrome (SIDS) among infants [3]. However, a gain in sodium channel conduction is demonstrated in LQTS associated with a genetic missense mutation with the alpha 1 synthropin gene [4].

External stimuli like loud noises, exercise, emotion and swimming may trigger an adrenergic response and elicit a long QT period in high risk patients.

Drug-induced LQTS are basically in direct relation to cardiac ion channels especially potassium that may be blocked by the therapeutic drug. Further genetic mutations may predispose patients to prolonged exposure to the drug due to its inherent poor metabolism and excretion.

Patients who inherit LQTS from either parent should take extra precaution in taking medications that may trigger LQTS like common antibiotics like erythromycin. Illicit drug use with amphetamine and cocaine may increase the risk of LQTS and sudden cardiac deaths for those who have concurrent risk factors.

Medical conditions like vomiting and diarrhea that may potentially lower the serum levels of potassium should be averted to prevent the occurrence of LQTS in hypokalemic states. Patients with concurrent illness like hypertension may be prescribed with diuretics that can potentially lower potassium levels.

Genetic testing may predict the risk among the offspring of the defective gene carriers; thus genetic counselling is an effective modality in the prevention of LQTS [10].

Long QT syndrome or LQTS is a dysrhythmic heart disorder associated with fast and chaotic heartbeats. The intermittent occurrence of these dysrhythmias may cause syncope and seizure attacks in afflicted patients. An increased duration in the dysrhythmia can result to sudden death in some patients.

Long QT syndrome is treatable and preventable, the intake of certain anti-arrhythmic drugs may avert its dysrhythmic complications. LQTS may also be treated with cardiac surgery and may be controlled with the use of implantable devices.

Definition

Long QT syndrome (LQTS) is a dysrhythmic heart disorder associated with fast and chaotic heartbeats that may potentially cause sudden death.

Cause

LQTS is either inherited (genetics) or acquired. 

Symptoms

Symptoms inculde fainting, seizure or sudden death.

Diagnosis

Electrocardiography, Holter monitoring, and event ECG monitoring may be necessary to diagnose LQTS.

Treatment and follow-up

Pacemaker implantation, defibrillation, beta-blockers, vitamin D and omega 3 fatty acids are used to treat the disorder.

1. Buber J, Mathew J, Moss AJ, et al. Risk of Recurrent Cardiac Events After Onset of Menopause in Women With Congenital Long-QT Syndrome Types 1 and 2. Circulation. Jun 21 2011; 123(24):2784-91.
2. Vatta M, Ackerman MJ, Ye B, Makielski JC, Ughanze EE, Taylor EW, et al. Mutant caveolin-3 induces persistent late sodium current and is associated with long-QT syndrome. Circulation. Nov 14 2006; 114(20):2104-12.
3. Border WL, Benson DW. Sudden infant death syndrome and long QT syndrome: the zealots versus the naysayers. Heart Rhythm. Feb 2007; 4(2):167-9.
4. Wu G, Ai T, Kim JJ, et al. Alpha-1-Syntrophin Mutation and the Long QT Syndrome: a disease of sodium channel disruption. Circulation. May 28, 2008.
5. Viskin S, Postema PG, Bhuiyan ZA, Rosso R, Kalman JM, Vohra JK, et al. The Response of the QT Interval to the Brief Tachycardia Provoked by Standing A Bedside Test for Diagnosing Long QT Syndrome. J Am Coll Cardiol. Jan 22 2010.
6. Adler A, van der Werf C, Postema PG, Rosso R, Bhuiyan ZA, Kalman JM, et al. The phenomenon of "QT stunning": The abnormal QT prolongation provoked by standing persists even as the heart rate returns to normal in patients with long QT syndrome. Heart Rhythm. Jun 2012; 9(6):901-8.
7. Schwartz PJ, Moss AJ, Vincent GM. Diagnostic criteria for the long QT syndrome: an update. Circulation. 1993; 88:782-4.
8. Zipes DP, Camm AJ, Borggrefe M, et al. ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: a report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (writing committee to develop Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Circulation. Sep 5 2006; 114(10):e385-484.
9. Roden DM. Long QT Syndrome. N Engl J Med. Jan 2008; 358(2):169-76.
10. Ching CK, Tan EC. Congenital long QT syndromes: clinical features, molecular genetics and genetic testing.Expert Rev Mol Diagn. May 2006; 6(3):365-74.