NEW YORK (Reuters Health) - When a measurement made on an electrocardiogram, called the QT interval, is longer than normal, it can indicate an increased risk of cardiac arrest. However, within limits, it is not likely to be dangerous if it’s seen in elite athletes, according to a report by UK investigators.
American and European guidelines recommend that athletes with a long QT interval, even in the absence of symptoms or a family history of heart problems, be disqualified from participating in sports, Dr. Sanjay Sharma told Reuters Health. However, the “significance of an isolated long QT in an asymptomatic athlete is unknown.”
Sharma, from King’s College Hospital, London, UK, and associates investigated the occurrence of prolonged QT in a large group of elite British athletes and evaluated its significance using various tests.
Seven of 2000 athletes (six males, one female) had a prolonged QT interval, the authors report, for an occurrence rate of 0.4 percent, the researchers report in the European Heart Journal. All seven athletes were symptomless and none showed irregular heart rhythms during 48 hours of monitoring.
Similarly, none of the athletes developed episodes of irregular heartbeats during exercise testing, the report indicates, but three of the seven subjects had QT values greater than 500 milliseconds (ms) — considered prolonged — during testing.
One of the five athletes who underwent genetic testing had a positive genetic diagnosis, the researchers report. His corrected QT value (QTc) at rest was greater than 500 ms.
“It is highly unlikely that all 0.4 percent of athletes had true long QT syndrome,” Sharma explained. It’s more likely that a greater heart mass brought on by exercise causes a slight prolongation of the QT interval.
“Our results suggest that athletes with a QTc of 500 ms or more can be regarded to have definite long QT syndrome and should be disqualified appropriately,” Sharma said.
“However, athletes with QTc of 440-490 ms may be able to compete,” provided they have no symptoms, have normal results on exercise testing and 24-hour ECG monitoring, and no first-degree family members with abnormalities “unless subsequent genetic testing proves otherwise.”
Sharma’s group is currently checking up annually on all athletes with a long QTc (but less than 500 ms) on an annual basis. “These athletes continue to compete and remain asymptomatic over a 3-year follow-up period,” Sharma added.
SOURCE: European Heart Journal, December 2007.