A friend of mine that lives in Florida recently found out that she has Long QT Syndrome, a fact she discovered due to a physical after passing out while exercising. She has not yet been to the Cardiologist so she doesn’t know what type she has yet. How bad is this? I read a little about it on wikipedia, but it didn’t say much about by how much, or whether it does have a large impact on lifespan and the like.
The basics are that the corrected QT interval on an EKG is greater than 450 msec (in a male). The QT interval is the time during a heart beat where the heart is considered “vulnerable” while the ventricles are relaxing from the previous beat. If the atria fire off (giving a P wave) prematurely during the QT interval or especially on the T wave (P-on-T wave), it can precipitate a polymorphic ventricular tachycardia (Torsdaes de Pointes). Longer QT intervals mean more of a chance for a premature P or even a regular P to fire off in the QT interval.
Long QT intervals are mostly caused by drugs. There are several congenital types, though, IIRC. The more common one, Romano-Ward, IIRC can be associated with congenital deafness. P-on-T waves or P waves during the QT can also be caused by many things, including getting thumped in the chest or exercise or stress or they can happen sporadically.
Obviously the first line is to make sure the long QT isn’t being caused by a treatable underlying disease or a med. Next, there are a number of treatment options, including drugs, minor surgical procedures that IIRC are done through a catheter, or implantation of an automatic internal cardiac defibrillator (AICD) that will detect ventricular tachycardia or ventricular fibrillation and give a shock to reset the heart rhythm.
The simple answer is that your friend’s heart is taking longer than normal to repolarize after beating. As edwino said, this can be caused by a variety of factors, including certain medications and congenital causes. This prolonged repolarization puts the heart at risk for polymorphic V-tach which can occur when a ventricular depolarization occurs during repolarization this would be an R-on-T (not P-on-T).
Here is an excellent site on Long QT syndrome
In many of the medical type threads on this board, I sometimes chuckle at the ingenuous advice to “get thee to a doctor”. Well, if I or a someone I care about had passed out while exercising and was also known to have a long QT interval, I would not tolerate any but the slightest delay in obtaining expert consultation.
I want to emphasize that although the long QT syndrome is associated with an increased risk of sudden death in otherwise healthy young adults, the fugures that populate the literature are for ‘all comers’ with the condition. But, your friend has already passed out during exercise. That identifies her as being at particular risk.
“Get thee to a specialist, pronto!”
This is the Mayo Clinic site about it.
My husband had a drug induced variation when he had pertussis. The doctor is still trying to determine if he has the familial form underlying or worse yet the aquired form from CAD (coronary artery disease.)
St. Urho is correct. It can be hard to detect, because the prolongation can be very slightly above normal. Since it prolongs with increased heart rate, the chances for an “event” increase with exercise. It’s sometimes missed on a routine ECG, because the machine measurement isn’t always acurate. Also, since the measurement varies with heart rate, the raw Q-T interval has to be corrected. Using the formula sq root of the R-R ÷QT=QT[sup]c[/sup].
The type of event is different than an ordinary “R on T”, in that it causes a particular type of ventricular tachycardia called Torsades de pointes which can be harder to convert to normal.
This may be misleading to some. The QT interval shortens with exercise because the heart rate increases. However, when one corrects the QT interval for heart rate, the corrected interval will be prolonged (compared to rest) so long as the rate at which the correction is being made is greater than 60.
See Table 1. here.
Sorry for being unclear. I should have gone into more detail.