People with long QT syndrome are typically told to avoid playing sports.
And beta-blocker drugs to lower the risk of suffering a sudden cardiac arrest is the standard of treatment.
A beta-blocking drug shortens the QTc. The QTc is the “corrected” QT interval, done with a mathematical formula and based on heart rate at the time of the EKG.
The QT interval is the length of time measured between the Q wave and T wave on an EKG strip.
Or, to put it another way, it’s the time it takes the heart to recharge or repolarize before the next beat.
This is measured in milliseconds, and though that seems like a really short time to make a difference, just 20 milliseconds CAN make a difference regarding risk enough for a sudden cardiac arrest during sports play.
It seemingly stands to reason that if a young fit person is on beta-blocking drugs for LQTS, he or she can participate in athletics – as long as there is a portable defibrillator nearby.
However, the typical management of this congenital disorder includes avoidance of athletic activity.
“Beta-blockers are not 100 percent effective,” says Paul Rogers, MD, PhD, Medical Director, Cardiac Rhythm Device Clinic, Ochsner Health System.
Dr. Rogers adds, “They are most effective in LQTS 1, somewhat effective in LQTS 2 and uncertain if they are effective in LQTS 3.” Beta-blockers shorten the QT interval – but not enough.
The shortening, though, indeed reduces the risk of sudden cardiac arrest.
But if the QTc is still within the range of SCA risk, then it’s still regarded as a contraindication to athletic activity.
The longer that QT prolongation is, the higher the risk of sudden cardiac arrest.
The goal is to shorten it as much as possible, but there is no drug available that reliably shortens it into a non-risk range.
If there were, patients would be given free reign to play sports and even train hard for endurance events.
Nevertheless, over recent years, guidelines for sports participation have been loosened somewhat, as more cardiologists (specifically, electrophysiologists) are treating young patients on a case-by-case basis, rather than lumping all of them into a cookie cutter management protocol.
Another point is that not all beta-blockers have the same effect on every patient.
Some work better than others for shortening the QT interval. Different beta-blockers should be tried to see which one is most effective, for that particular patient, at shortening the QT interval.
When a young person is also given an ICD (implantable cardioversion device), and is asymptomatic, this increases the chances that their physician will endorse sports participation.
Often, a diagnosis is made in a person without symptoms when a family member tests positive after suffering sudden cardiac arrest or unexplained fainting.
Dr. Rogers has clinical interests in complex heart arrhythmias and the benefits of implantable cardiac device based therapies in patients with reduced heart function.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.