Author + information
- Preben Bjerregaard, MD, DMSc⁎ ()
- ↵⁎Department of Cardiology, St. Louis VA Medical Center, 915 North Grand Boulevard, St. Louis, Missouri 63106
I would like to commend Gollob et al. (1) for their attempt to generate criteria on how to diagnose short-QT syndrome (SQTS), but I would also like to point out some of the shortfalls and errors in their report.
In Table 1 of their report, at least 1 patient appears to have been included twice (Patients #23 and #49) with different ages and different QT intervals. Patient #46, published in 2008, was a 22-year-old man who “experienced unheralded syncope for the first time while driving, resulting in a motor vehicle accident” which in the current report is categorized as aborted cardiac arrest. This patient had no documented arrhythmias and no short QT interval on electrocardiography (QT interval 366 ms at 66 beats/min). The electrocardiogram appears to display early repolarization, and genetic testing discovered a novel KCNH2 mutation of undetermined significance, which was also present in the patient's mother, who also had a normal QT interval. This patient does not fit the general concept of a patient with SQTS.
Patients #59 to #61, from a letter to the editor, are also outliers and should not have been included. These patients had a C-terminal KCNH2 mutation (R1135H) shown (2) to cause both a short QT interval and a Brugada-type electrocardiographic pattern, as seen in Patient #59.
The exclusion of Patients #59 to #61 would have changed Table 2 in their report. Instead of an upper value for the range of QT intervals in patients with SQTS of 401 ms, the actual value would have been 334 ms.
Using the QT interval corrected by Bazett's formula in the proposed diagnostic criteria has important limitations. As already observed in the very first patient diagnosed with SQTS (3), the QT interval in SQTS changes very little with changes in heart rate, and correction of the QT interval is therefore barely necessary at normal heart rates. Bazett's formula will greatly overcorrect the QT interval at any heart rate >60 beats/min, and attempts should always be made to record an electrocardiogram as close to 60 beats/min as possible by obtaining data from Holter monitoring or using a beta-blocker.
There is no doubt about the potential arrhythmic risk of a short QT interval, but corrected QT intervals as low as 340 to 350 ms (considered normal by some) have been observed for years without reports of any increased risk for sudden cardiac death. So far, SQTS has been an extremely rare diagnosis, with no documentation of sudden cardiac death or aborted sudden cardiac death due to SQTS when the QT interval is >315 ms.
Therefore, it is my opinion that the proposed diagnostic criteria for SQTS are poorly founded and should be used with great caution.
- American College of Cardiology Foundation