What is long QT and how can it be recognized?
QT interval represents the electrical repolarisation of the heart. It is measured from an electrocardiogram (ECG). A long QT interval predisposes the heart to arrhythmias, which can sometimes be life threatening. Most cases are acquired due to abnormalities in the blood electrolytes (low potassium or magnesium) or certain drugs (psychotropic agents, certain antibiotics and antifungals). It can also be due to decreased blood supply to certain regions of the heart (coronary artery disease) or myocardial disease. The congenital variety is known as long QT syndrome and there over 7 – 10 subtypes. A medical article on long QT syndrome is available at: http://www.ipej.org/0204/vincent.htm.
Interestingly, short QT interval can also cause cardiac arrhythmias. There is a condition called congenital short QT syndrome, which is more likely to cause atrial arrhythmias. Individuals with both long QT syndrome and short QT syndrome require implantation of an ICD (implantable cardioverter defibrillator) if they have significant cardiac arrhythmia, which can lead to cardiac arrest.