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.
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]
Adenosine-induced, sudden bradycardia and subsequent tachycardia have also been investigated to identify QT changes of diagnostic value in patients with LQTS. [doi.org]
Polymorphic ventricular extrasystolies and episodes of polymorphic non‐sustained ventricular tachycardia were confirmed by Holter ECG monitoring. [oadoi.org]
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]
As inherited congenital heart disease may be a risk factor for sudden unexpected death in epilepsy (SUDEP), attention to all specific genetic markers in a young patient with QT prolongation and a first seizure could guide the use of anti-seizure medication [ncbi.nlm.nih.gov]
disease MANAGEMENT beta-blockade avoidance of increased sympathetic tone cardiac pacing treat cause ICD About Dr Chris Nickson An oslerphile emergency physician and intensivist suffering from a bad case of knowledge dipsosis. [lifeinthefastlane.com]
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]
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 . A positive standing test may continually show a prolonged QT after resting and even when the heart returns to normal rate .
- 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 .
QT, RR, ST Intervals
Prolonged QT Interval
[…] is characterized by episodes of fainting (syncope) and varying degree of ventricular arrhythmia as indicated by the prolonged qt interval. [icd9data.com]
Here we present genetic and phenotypic data for 4 family members across 2 generations who all have evidence of prolonged QT interval and left ventricular noncompaction in association with a pathogenic mutation in KCNQ1, and discuss the potential mechanisms [ncbi.nlm.nih.gov]
(ECG): To confirm prolonged QT intervals Stress test with ECG: To provide better resolution of prolonged QT intervals during strenuous exercise Treatment of Long QT Syndrome LQTS Treatments for LQTS include: Lifestyle changes, such as reducing exercise [utswmedicine.org]
Incomplete Right Bundle Branch Block
In one study, the cardiac event rate per year was 7.7% in patients with aborted SCD, 1.9% in patients with syncope, and 0.5% in asymptomatic patients. 36 The type 1 Brugada ECG pattern is characterized by a complete or incomplete right bundle-branch block [doi.org]
Torsades De Pointes
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]
Examples of T-wave alternans from a 2-year-old long-QT syndrome patient with multiple episodes of cardiac arrest. Tracings are from a 24-hour Holter recording. [circep.ahajournals.org]
Another indicative finding is T-wave alternans (alternating polarity and amplitude), which may be present at rest for brief moments but most commonly appears during emotional or physical stress. [aafp.org]
Biphasic T Wave
Potassium administration led to resolution of notched T waves in five of six patients (see, for example, Fig 3 ), and the biphasic T waves in the seventh subject became monophasic. [doi.org]
The main treatment options in LQTS are beta-blockers, permanent pacing, stellectomy, implantable cardioverter-defibrillator (ICD), or a combination . The use of anti-arrhythmic drugs like beta-blockers  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.
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.
- 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 . 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 . Functional studies have demonstrated that late sodium channel dysfunction associated with LQTS is implicated in sudden infant death syndrome (SIDS) among infants . However, a gain in sodium channel conduction is demonstrated in LQTS associated with a genetic missense mutation with the alpha 1 synthropin gene .
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 .
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.
LQTS is either inherited (genetics) or acquired.
Electrocardiography, Holter monitoring, and event ECG monitoring may be necessary to diagnose LQTS.
Treatment and follow-up
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