I understand there is more than one type of long QT. Can you explain the different types?

There are several types of long QT syndromes, seven to be precise. The one thing that all the long QT syndromes have in common is that they are associated with abnormal ion channels within heart muscle cells. Ion channels are small holes that allow sodium and potassium to pass through them every time the heart generates an electrical impulse. In general, long QT syndrome may be caused by an abnormal potassium ion channel or an abnormal sodium ion channel. I’m going to focus on long QT syndromes 1, 2 and 3 only because they make up 95% of all the long QT syndromes that we are aware of. All three are usually inherited as an autosomal dominant trait, by that I mean if a parent has one of these conditions, there’s a 50% chance they will pass them on to their offspring. Long QT syndrome 1 is due to an abnormal potassium ion channel. Most individuals with long QT syndrome 1 do not have any symptoms but a small proportion experience palpitation, dizziness or blackouts that are often precipitated by exercise. It’s usually the adrenaline that one produces during exercise that predisposes the heart to go into a very bizarre rhythm to cause these symptoms. Sometimes the rhythm disturbance can cause sudden death. Long QT syndrome type 1 is very, very sensitive to beta blocker therapy and if we can hide the heart from adrenaline using a beta blocker then we can prevent most deaths from long QT syndrome 1. Individuals with long QT syndrome 1 who continue to have symptoms on a beta blocker such as blackouts should be implanted with an internal cardioverter defibrillator. Long QT syndrome 2 is also due to an abnormal potassium ion channel disorder. Like long QT syndrome 1, most symptoms occur during surges of adrenaline in the body. In long QT syndrome 2 interestingly, these surges of adrenaline are initiated by intense emotion or auditory stimuli. The story we normally get is an individual got given bad news and dropped dead or the individual was laughing and very, very excited and dropped dead or an individual went to sleep one night, set the telephone alarm, the alarm went off, they wake up with a startle and drop dead on the spot. So it’s usually auditory stimuli or intense emotion that causes death. Once again, long QT syndrome type 2 is amenable to treatment with beta blockers, those individuals who continue to have blackouts on beta blockers should be treated with a defibrillator. Long QT syndrome type 3 is due to an abnormal sodium ion channel disorder. In my mind, this is the most worrying type of long QT syndrome to have because these deaths don’t occur during exertion or during intense emotion or with auditory stimuli, they usually occur at rest. The most common scenario is someone goes to sleep one night and never wakes up in the morning. There is growing evidence that drugs like beta blockers aren’t very effective in long QT syndrome type 3. Indeed there’s only one effective treatment and that is the implantation of an internal cardioverter defibrillator. Now that I’ve told you all of this, not everybody with long QT syndromes die. The sort of people that are most at risk of dying are those that have got a long QT interval of more than 500 milliseconds: those that have got recurrent blackouts; and those with long QT syndrome type 3.