Long QT syndrome (LQTS) is a hereditary or acquired disorder characterized by abnormal prolongation of the corrected QT (QTc) interval on the electrocardiogram. This abnormality reflects a disturbance in the processes of repolarization of the ventricles of the heart and can lead to potentially life-threatening arrhythmias, including polymorphic ventricular tachycardia of the "pirouette" type and sudden cardiac death. The pathophysiological basis of the disease is an imbalance of potassium, sodium and calcium ion currents through cardiac membranes, which disrupts the normal ratio of myocardial depolarization and repolarization.
History of the disease and interesting historical facts
The first descriptions of long QT syndrome appeared in 1957, thanks to the work of Anders Silva and Axel Frederickson, who described a familial case of sudden death in children with characteristic changes in the ECG. Interestingly, the term “romantic death” was coined to describe cases of sudden death of young people during emotional excitement or physical activity. In the 1990s, the first genes associated with LQTS were identified, opening a new era in understanding the molecular mechanisms of the disease. “The discovery of mutations in genes encoding ion channels was a revolutionary step in understanding arrhythmogenesis,” note researchers from the Mayo Clinic.
Epidemiology
According to large population studies, the prevalence of congenital LQTS syndrome is approximately 1:2000-1:2500 newborns. It is important to note the following statistics:
- Up to 10-15% cases of sudden cardiac death in young adults may be associated with LQTS
- Approximately 20-30% patients remain without a confirmed genetic diagnosis even after comprehensive testing
- About 50% cases represent sporadic mutations
Genetic predisposition to this disease
Currently, more than 17 genes associated with LQTS are known, among which the most significant are:
- KCNQ1 (LQT1) - responsible for 30-35% cases
- KCNH2 (LQT2) - accounts for 25-30% cases
- SCN5A (LQT3) - occurs in 5-10% cases
Mutations in these genes lead to disruption of the functioning of potential-dependent ion channels. “Each type of mutation has its own characteristics of clinical manifestation and arrhythmia triggers,” emphasize experts from the European Heart Rhythm Association.
Risk factors for the development of this disease
The main risk factors include:
- Taking certain medications (antiarrhythmic drugs, antibiotics, antipsychotics)
- Electrolyte disturbances (hypokalemia, hypomagnesemia)
- Bradycardia and pause arrhythmias
- Emotional stress and physical tension
The combination of genetic predisposition with the influence of provoking factors is considered especially dangerous.
Diagnosis of this disease
The main diagnostic criteria include:
- Prolongation of QTc interval >460 ms in men and >470 ms in women
- Presence of characteristic changes in T-wave
- Family history of sudden cardiac death
Laboratory tests include genetic analysis, determination of blood electrolytes. Differential diagnosis is performed with other causes of QT prolongation, such as hypothyroidism or intracranial pathology.
Treatment
The therapeutic approach includes:
- Lifestyle modification (limiting stressful situations)
- Pharmacological therapy
- Surgical treatment (implantation of a cardioverter-defibrillator)
- Denervation procedures
The choice of treatment method depends on the form of the disease and the degree of risk of developing life-threatening arrhythmias.
List of drugs used to treat this disease
Main groups of drugs:
- Beta-blockers (propranolol, metoprolol)
- Calcium antagonists (verapamil)
- Potassium and magnesium preparations
- Mexiletine (for LQT3)
It is important to note that the choice of drug depends on the patient's genotype.
Disease monitoring
Regular monitoring includes:
- ECG monitoring every 3-6 months
- Monitoring electrolyte levels
- Evaluation of the effectiveness of therapy
The prognosis improves significantly with adequate treatment, but the risk of sudden death remains at 0.5-1% per year.
Age-related features of the disease
In newborns, the disease may manifest itself as bradycardia and pauses, in adolescents - syncope, especially during physical exertion. In adults, arrhythmia is more often observed in stressful situations. With age, the risk of complications increases, especially in women after 40 years.
Questions and Answers
- How often should an ECG be done for LQTS? Annual ECG monitoring is recommended, and if symptoms change, immediate examination is recommended.
- Is it possible to play sports with this disease? Intensive sports are contraindicated; only moderate physical activity is allowed.
- How dangerous is pregnancy with LQTS? Pregnancy requires special monitoring, as the risk of arrhythmia increases.
Advice from Dr. Oleg Korzhikov
Patients often ask how to live with this diagnosis. I recommend:
- Always carry a card with your diagnosis and information about the medications you are taking
- Avoid extreme temperatures and stressful situations
- Visit your cardiologist regularly and follow all instructions.
- Discuss safe physical activity options with your doctor
“The main thing is a conscious attitude towards your health and following your doctor’s recommendations,” emphasizes Dr. Korzhikov.
