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:
The following test and diagnostic modalities are implored among patients with high suspicion of Long QT syndrome:
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.
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.
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:
The long QT syndrome is either inherited or acquired. There are at least two forms of inherited that has been identified so far:
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 .
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 .
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.
Long QT syndrome (LQTS) is a dysrhythmic heart disorder associated with fast and chaotic heartbeats that may potentially cause sudden death.
LQTS is either inherited (genetics) or acquired.
Symptoms inculde fainting, seizure or sudden death.
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.