Long QT Syndrome: Causes, Symptoms, Diagnosis, Treatment, and Prevention

Heart rhythm abnormalities known as arrhythmias, or rapid, erratic heartbeats, can be brought on by Long QT syndrome (LQTS). Sudden fainting, convulsions, or even death may result from these irregular heartbeats. Long QT syndrome can be acquired later in life as a result of certain drugs, infections, or other disorders, or it can be inherited from the parents. A genetic test or an electrocardiogram (ECG) can be used to identify long QT syndrome. To stop harmful arrhythmias, treatment options include medication, surgery, or lifestyle modifications.

Causes

The etiology of long QT syndrome is an issue with the heart's electrical circuitry. The heart pumps blood throughout the body by coordinating the contraction and relaxation of its four chambers. Electrical impulses that pass via the heart regulate this activity. The five waves that make up an ECG are denoted P, Q, R, S, and T, and their timing and length may be measured using an ECG. The duration between the beginning of the Q wave to the conclusion of the T wave is known as the QT interval. It stands for the amount of time the heart takes to beat and pump blood. The QT interval typically lasts for less than half of a pulse. On the other hand, the QT interval is longer than usual in those who have long QT syndrome. This implies that the heart is more prone to irregular heartbeats and requires more time to recharge.

Long QT syndrome is classified as either congenital or acquired. Caused by a mutation in one of the genes that control the electrical activity of the heart, congenital long QT syndrome manifests itself at birth. Congenital long QT syndrome has several subgroups, each with a unique genetic etiology and arrhythmia risk. Congenital long QT syndrome is associated with several genes, including GDF6, GDF3, and MEOX. Later in life, acquired long QT syndrome occurs and is brought on by several causes that impact the electrical system of the heart, including:

• Certain medications, such as antibiotics, antihistamines, antidepressants, antipsychotics, or diuretics

• Low levels of potassium, calcium, or magnesium in the blood

• Viral or bacterial infections that affect the heart

• Heart diseases, such as coronary artery disease, heart failure, or cardiomyopathy

• Other medical conditions, such as diabetes, thyroid disorders, or anorexia nervosa

Symptoms

Some people with long QT syndrome do not have any symptoms and may not know they have the condition until they have a cardiac event. Others may experience one or more of the following symptoms:

• Sudden fainting (syncope), which is the most common symptom of long QT syndrome. Fainting may occur with little or no warning, especially during physical or emotional stress, exercise, or loud noises

• Seizures, which may be mistaken for epilepsy. Seizures may occur due to lack of oxygen to the brain during an arrhythmia

• Palpitations, which are sensations of the heart beating fast, hard, or irregularly

• Dizziness or lightheadedness, which may precede fainting or seizures

• Sudden cardiac arrest, which is a medical emergency that occurs when the heart stops beating. This can cause death within minutes if not treated with cardiopulmonary resuscitation (CPR) or a defibrillator

Diagnosis

A physician will inquire about the patient's symptoms, medicines, and medical and family history in order to identify long QT syndrome. Along with a physical examination, the doctor will use a stethoscope to listen to the heart. The primary diagnostic tool for long QT syndrome is an electrocardiogram (ECG), which captures the heart's electrical impulses. In order to determine the typical range for the patient's age, sex, and heart rate, the doctor will evaluate the QT interval. Long QT syndrome may be indicated by a prolonged QT interval. A normal ECG can not, however, rule out the illness because the QT interval might change based on the circumstances. As a result, the physician could prescribe more testing to validate the diagnosis or look for other arrhythmia reasons, such as:

• Portable devices known as Holter monitors or event monitors record cardiac activity for extended periods of time, often up to 24 hours. When symptoms arise, the patient wears the gadget at home and hits a button. Any aberrant heartbeats that would go undetected on a typical ECG can be recorded by the gadget.

• Exercise stress testing includes stationary cycling or treadmill walking while an ECG is being used to monitor the heart. This test can show how the heart reacts to exercise and whether it causes arrhythmias.

• Genetic test, which entails drawing blood and examining it to see whether any mutations in the genes linked to long QT syndrome are present. This test can determine the congenital long QT syndrome subtype and confirm the diagnosis. Additionally, it can assist in screening family members who could be susceptible to acquiring the illness.

Treatment

Treatment for long QT syndrome aims to prevent or halt arrhythmias and mitigate the risk of fainting, seizures, or sudden cardiac arrest. The approach to treatment varies based on factors like the syndrome's type, cause, and severity, as well as the patient's age, health status, and preferences. Treatment options encompass:

• Medications, such as beta blockers, antiarrhythmic drugs, or potassium supplements, which can regulate heart rate, shorten the QT interval, or address electrolyte imbalances. These drugs are effective in reducing the frequency and severity of arrhythmias and associated symptoms.

• Surgical interventions, including implantable cardioverter-defibrillator (ICD) placement or left cardiac sympathetic denervation. An ICD, implanted under the skin near the chest, monitors heart rhythm and delivers an electric shock to restore normal heartbeat in case of an arrhythmia. Left cardiac sympathetic denervation involves cutting or removing some nerves controlling heart electrical activity, thereby lowering the risk of arrhythmias and sudden cardiac arrest in certain individuals with long QT syndrome.

• Lifestyle modifications, like avoiding or limiting substances or activities known to trigger or exacerbate arrhythmias. These may include alcohol, caffeine, nicotine, illegal drugs, specific herbal supplements, and intense physical exertion. Adequate hydration, balanced nutrition, and stress management are also vital. Individuals with long QT syndrome should wear a medical alert bracelet or necklace and keep healthcare providers informed about their condition.

Prevention

While some instances of long QT syndrome are unavoidable, stemming from genetic inheritance or unidentified causes, preventive measures can mitigate or forestall acquired cases. Strategies to consider include:

• Steering clear of medications known to prolong the QT interval, like certain antibiotics, antihistamines, antidepressants, antipsychotics, or diuretics. Prioritize consulting a physician before starting any new medication and adhere closely to prescribed instructions and dosages.

• Limiting exposure to substances that could harm the heart, such as alcohol, caffeine, nicotine, illegal drugs, or specific herbal supplements. Always scrutinize product labels and ingredients, and seek medical guidance before incorporating new substances.

• Sustaining healthy levels of potassium, calcium, and magnesium in the bloodstream, vital for optimal heart electrical activity. Incorporate foods rich in these minerals, such as bananas, potatoes, spinach, yogurt, or nuts, while avoiding high-salt, high-sugar, or high-fat foods that can impact blood pressure and cholesterol levels. If necessary, adhere to supplementation under medical supervision.

• Addressing or preventing infections or illnesses that may impact heart health, such as viral or bacterial infections, diabetes, thyroid disorders, or anorexia nervosa. Promptly seek medical intervention upon noticing any signs or symptoms of such conditions, and diligently follow prescribed treatment protocols.

• Undergoing regular heart rhythm and function assessments through routine check-ups and tests. If diagnosed with long QT syndrome, adhere to medical advice regarding medications, surgical interventions, or lifestyle adjustments. Additionally, communicate with family members about the condition and the potential for genetic testing.