A recent article published in EMS WORLD cautions that long QT syndrome (LQTS), a potentially lethal disease in young people, often remains undiscovered. An ECG can detect the disease, which can cause sudden cardiac death, but thus far screening for LQTS has not been mandatory.
LQTS can be described as the malfunctioning of the electrical phase of the myocardium’s reloading process.
LQTS, a genetic disorder, is caused by an electrical malfunction in the reloading of the myocardium (the middle muscular layer of the heart wall) returning after its contraction.
Functional Changes Associated with LQTS
Electrical activity in the myocardium occurs through the movement of ion channels and produces myocardial contractions.
Ions such as sodium, calcium, chloride, and potassium cross over cell membranes by way of the ion channels thereby creating electrical energy in the myocardium.
Abnormal ion channels in the myocardium cause electrical disruption and are characteristic of LQTS.
When the two most abundant ions, potassium, and sodium, are impacted by LQTS, patients are put at risk for irregular heartbeat (arrhythmias).
The change, which produces contractions in the myocardia, can be detected with an ECG.
About the QT Interval
The QT interval is a measurement assessed on an ECG. It approximates the amount of time that the cardiac ventricles contract to when they conclude relaxation. An unusually long or short QT interval is accompanied by an increase in the risk of abnormal heart rhythms and sudden cardiac death.
QT interval abnormalities may be caused by long QT syndrome, medications, disruptions in amounts of salts within the blood, or hormonal imbalances.
QT syndrome produces symptoms such as loss of consciousness (syncope), palpitations, and seizures. These symptoms generally occur in connection with certain activities or loud sounds. A thorough history is critical when a doctor is considering new medication. Certain medications can prolong the QT interval, such as antidepressants.
Patients may have been prescribed beta-blockers to prevent LQTS. Families must ensure that these children are taking their medication daily. Missing a dose or discontinuing medication is a major cause of cardiac events.
Pacemakers and defibrillators are long term solutions that control the child’s heart rhythm. These devices may need to be replaced as the child grows.
The three most common types of LQTS:
Type 1: The heart’s electrical energy is disturbed by the malfunctioning of its potassium ion channels. This can be caused by physical exertion, emotional stress, or sudden loud noises.
Torsades de pointes (translation: twisting of points) is an uncommon ventricular tachycardia (rapid heartbeat) mostly found in patients with LQTS1.
Type 2: a low level of potassium ion disturbs the heart’s electrical functioning leading to arrhythmia. Causes are the same as listed in type 1.
Type 3: in this case, a low level of sodium transported through the ion channels of the heart can trigger arrhythmias.
A point to remember is that although LQTS can be found through ECG tests, it is often left undetected.
If a child has been diagnosed with LQTS previously, a complete history and understanding of the disease are warranted.