Long QT syndrome 2 (LQT2) is a hereditary disorder characterized by abnormal prolongation of the QT interval on the electrocardiogram and an increased risk of life-threatening ventricular arrhythmias, such as torsades de pointes. This condition is caused by impaired repolarization of the ventricular myocardium, which leads to an increase in the duration of the action potential of cardiomyocytes. The development of the syndrome at a young age is especially dangerous, when the first manifestation of the disease may be sudden cardiac death.
History of the disease and interesting historical facts
The initial description of long QT syndrome was made in 1957 by Danish researchers Anton Jernel and Peter Lang-Nielsen while studying a family case of sudden infant death. An important historical moment was the description of a clinical case of the Romanov family, where it was suggested that Tsarevich Alexei may have suffered from this disease, which would explain his unexplained attacks. According to research published in the journal Circulation: “The genetic basis of LQT2 was only established in the 1990s, with the discovery of mutations in the KCNH2 gene.”
Epidemiology
According to international registration studies, the prevalence of LQT2 syndrome is approximately 1 case per 2000-2500 newborns. Statistics show that women make up about 65% patients diagnosed with LQT2, which is confirmed by the data of a study published in the European Heart Journal: "Female gender is an independent risk factor for arrhythmic complications in patients with LQT2." The age of first clinical manifestation is usually adolescence.
Genetic predisposition to this disease
LQT2 is caused by mutations in the KCNH2 gene (HERG), located on chromosome 7q35-36, which encodes the α-subunit of the IKr potassium channel. The main types of mutations include:
- Missense mutations (80% cases)
- Nonsense mutations (10%)
- Splicing mutations (5%)
- Deletions/insertions (5%)
"More than 900 different mutations in the KCNH2 gene have been identified," notes the work, published in the journal Heart Rhythm.
Risk factors for the development of this disease
In addition to genetic predisposition, there are additional factors:
- Emotional stress and sudden auditory stimuli
- Hypokalemia and hypomagnesemia
- Taking certain medications (eg, class IA and III antiarrhythmics)
- Physical overexertion
- Hormonal changes, especially in women
Diagnosis of this disease
The main diagnostic methods include:
- Electrocardiography (the main diagnostic criterion is the corrected QT interval >450 ms in men and >460 ms in women)
- Genetic testing to detect mutations in the KCNH2 gene
- Holter ECG monitoring
- Treadmill test
- Load test
Differential diagnosis is carried out with other forms of long QT syndrome, as well as with acquired forms of prolongation of the QT interval.
Treatment
The therapeutic strategy includes:
- Beta-blockers (propranolol, nadolol)
- Implantation of a cardioverter-defibrillator in high-risk patients
- Sympathectomy in difficult cases
- Correction of electrolyte disturbances
- Avoiding trigger factors
List of drugs used to treat this disease
Main groups of drugs:
- Nadolol (D-Nadolol)
- Propranolol
- Atenolol (Tenormin)
- Metoprolol (Betaloc)
- Potassium and magnesium preparations (Panangin, Asparkam)
Disease monitoring
Regular monitoring includes:
- Annual ECG monitoring
- Monitoring electrolyte levels
- Evaluation of the effectiveness of beta-blocker therapy
- Registration of arrhythmic episodes
The prognosis improves significantly with adequate therapy, but the risk of sudden death remains even with proper treatment.
Age-related features of the disease
In young children, the disease is more often manifested by paroxysmal tachycardia, while in adolescents, fainting spells predominate. In adult patients, the influence of hormonal factors is more pronounced, especially in women during pregnancy and menopause. "Aging of the body can modify the manifestations of the syndrome," the American Journal of Cardiology study notes.
Questions and Answers
- How often should an ECG be done for LQT2? An annual ECG check is recommended, and as needed if the condition changes.
- Is it possible to play sports with this disease? Intense physical activity is contraindicated; only light forms of physical activity are allowed under the supervision of a physician.
- What foods should be excluded? It is necessary to limit the consumption of caffeine and alcohol, which can provoke arrhythmia.
- What to do in case of an attack of arrhythmia? Call an ambulance immediately and assume a lying position, providing access to fresh air.
- How safe is pregnancy with LQT2? Pregnancy requires special monitoring, as hormonal changes can increase the risk of arrhythmia.
Advice from Dr. Oleg Korzhikov
As an experienced cardiologist, I often encounter questions from patients about LQT2. Here are the main recommendations:
- "The most important thing is to take your prescribed beta blockers regularly."
- "Avoid loud sounds, use vibration instead of alarm ringing"
- "Be sure to inform all doctors of your diagnosis before any medical procedures."
- "Wear a medical bracelet with information about the diagnosis"
- “Don’t ignore even minor changes in your health – consult your doctor immediately”
