Long QT syndrome is a problem with the repolarization of the heart. Repolarization is the time the heart needs to rest and recharge. The T wave denotes the repolarization of the ventricles. The QRS complex on an ECG signifies the contraction/depolarization of the ventricles. The danger is that when a contraction starts during repolarization or on the T wave, then arrhythmia's can occur such as ventricular tachycardia or torsades de pointe (twisting of the points) and sudden cardiac death. The long QT syndrome is characterized by the time interval from beginning of ventricular contraction to repolarization of the ventricles or the QT interval. Anything longer than .44 secs for men and .46 for women is classified as the long QT syndrome. There are two forms of the syndrome congenital and acquired.
In our bodies we have genes, I'm sure you have heard about them, not the jeans you wear but the genes that make us. These genes define who we are and what we will look like and how long we live. Humans have evolved over 10,000 years and we will continue to evolve. The reason we evolve is through an accidental process known as gene mutation. Sometimes the mutations help us survive like a large brain or opposable thumbs. Other mutations aren't helpful at all like muscular dystrophy and of course long QT syndrome.
It is a mutation on our genes namely LQT 1 through 7. There are 2 types of congenital LQTS, Romano-Ward syndrome and Jervell and Lange-Nielsen syndrome. Congenital LQTS accounts for 3000 to 4000 annual sudden cardiac deaths in childhood in the United States. The estimated occurrence of the congenital LQTS is 1:2,500 to 1:10,000. LQTS can be very difficult to diagnose. Patients can be without any signs and symptoms for the disorder and most people seek medical attention because a relative had genetic testing done or an abnormal ECG/EKG was done for some other reason.
The onset of ventricular arrhythmia may be triggered by external events. Though people may exhibit different triggers or combination of events. The most common triggers are exercise, noise, emotion, sudden waking by an alarm clock, telephone, thunder and swimming or diving.
Syncope (passing out), presyncope (feeling like going to pass out but actually don't), palpitations, seizures and sudden cardiac arrest.
These symptoms are vague in nature and can have other benign causes for example syncope because to got up too fast or presyncope because you had too hot of a shower or palpitations because you drank too much coffee. A detailed history from your doctor can help narrow down the causes. Just because you have the symptoms doesn't necessarily mean you have the disorder. It just means it warrants further investigation. Also if you have these symptoms it doesn't mean you can ignore it either. Get medical attention.
Drug therapy, hypokalemia and hypomagnesemia are common causes of acquired long QT syndrome. Finding the drug culprit in acquired can be tricky. It is a work in progress. To better know which drug affects the QT interval it is best to list in drug classes rather than individual drugs:
Antiarrhythmic drugs ( Sotalol, amiodarone)
Some non sedating antihistamines
Macrolide antibiotics (erythromycin)
Some psychotropic drugs (Haldol, methadone)
Some gastric motility agents (cisapride)
These classes have been known to illicit the syndrome sometimes but does not include everybody all the time. Which makes determining the culprit difficult as I have already said. According to the world health organization (WHO) of the 761 cases reported between 1983 and 1999 the most common drugs were sotalol and cisapride. In a review of the 92 cases in the United States Antiarrhythmic drugs were responsible in 71 cases.
High drug doses or rapid infusion of QT prolonging drug. Using more than one QT prolonging drug. Drinking grapefruit juice, Taking "water pills" or diuretics with the QT prolonging drugs, Female gender, Underlying heart disease (heart failure) and cardiomyopathy, Recent conversion from atrial fibrillation and Advanced age
These are not absolutes, they are risk factors, but it is worth a discussion with your doctor if you have one or more risk factors. Talk to your doctor if you have risk factors and experiencing syncope (passing out).