Short QT Syndrome Patients

Definition and prevalence of a Short QT Interval

Short QT Interval and Short QT Syndrome Schulze-Bahr E, Breithardt G.. J Cardiovasc Electrophysiol 2005;16:397-398

The authors present data from several papers showing the lower limit of normal for the QT interval, including Rautaharju’s data from 14000 healthy individuals, where the lower limit of normal for the QT interval at 60 bpm was 361 msec.

Distribution and Prognostic Significance of QT Intervals in the Lowest Half Centile in 12,012 Apparently Healthy Persons Gallagher MM, Magliano G, Yap YG, Padula M, Morgia V, Postorino C, Liberato FD, Leo R, Borzi M, Romeo F.. Am J Cardiol 2006;98:933-935

Among 12,012 healthy Italian subjects (90.7 % male) 30 +/- 10 years old the cut-off QTc for the lowest half centile (60 subjects) was 361 msec and the shortest QTc 335 msec.

36 subjects with QTc  360 ms were followed for 7.9 +/- 4.5 years and none of them died suddenly.

The QT intervals were measured manually and the end of the T wave was the point at which the T wave returned to the isoelectric line. QTc was calculated according to Bazett formula. Since Bazett formula overcorrects at slow heart rates the significantly slower heart rates in subjects with the shortest QTc is no surprise.

The absence of any QTc < 335 msec in this study confirms the impression that Short QT Syndrome is a distinct clinical entity involving QT intervals substantially shorter than those found in a normal population.

Electrocardiographic reference ranges derived from 79,743 ambulatory subjects Mason JW, Ramseth DJ, Chanter DO, Moon TE, Goodman DB, Mendzelevski B.. J Electrocardiology 2007;40:228-234

The Shortage of Short QT Intervals Reinig MG, Engel TR.. CHEST 2007;132:246-249

In a hospital based population of 106,432 patients the mean QTc (+/- SD) was 430 +/- 19 msec , not a single ECG was found to have a QTc ≤ 300msec

Prevalence and Prognostic Significance of Short QT Interval in a Middle-Aged Finnish Population Anttonen O, Junttila MJ, Rissanen H, Reunanen A, Viitasalo M, Huikuri HV.. Circulation 2007;116:714-720

QT intervals were measured from the 12-lead ECGs of 10,822 subjects (5,658 males, mean age 44 +/- 8.4 years) enrolled in a population study and followed for 29 +/- 10 years.

QTc < 360 msec was seen in 2.8 %

QTc < 340 msec was seen in 0.4 %.

QTc < 320 msec was seen in 0.1 %.

During follow up there were no sudden deaths in the 43 subjects with a QTc < 340 msec.

The higher number of subjects with a short QT interval in this study than in the study by Gallagher et al. (# 52) is likely due to the difference in defining the end of the T wave.

In the present study the end of the T wave was defined as a point at which a tangent of the descending limb of the T wave intersects the baseline, whereas Gallagher et al defined it as the point at which the T wave returned to the isoelectric line.

Another point of significance is the limitations in the use of Bazett’s correction formula. In both the study by Gallagher et al. and the present study, subjects with the shortest QT were the subjects with the lowest heart rate. Bazett’s formula is known for its tendency to over-correct the QT interval during bradycardia.

Short QT. What Does It Matter? Viswanathan MN, Page RL. Circulation 2007;116:686-688

Editorial to the previous article.

An important fact pointed out by the authors is related to the 11 patients with QTc < 320 msec who were followed for approximately 29 years. The 95 % confidence interval around an incidence of 0 out of 11 would include frequencies that might even allow for implantation of a prophylactic ICD.

The authors suggest one should consider SQTS in a patient with QTc < 340 msec and other factors suggestive of arrhythmia (such as syncope or family history of sudden death).

Two Cases of Short QT Interval. Moriya M, Seto S, Yano K, Ahahoshi M. PACE 2007;30:1522-1526

Among 19,153 subjects (7,525 men and 11,628 women) from the Hiroshima-Nakasaki Radiation Effects Research Study who had undergone biannual health examinations (including ECG recordings) since 1958, only two (0.01 %) were found to have QTc < 350 msec, but none of them a family history or symptoms suggesting SQTS.

Assessment of QT intervals and Prevalence of Short QT Syndrome in Japan**.** Funada A, Hayashi K, Ino H, Fujino N, Uchiyama K, Sakata K, Masuta E, Sakamoto Y, Tsubokawa T, Yamagishi M. Clin Cardiol 2008;31(6):270-274

ECGs were obtained from a hospital population of 12,149 and in 10,984 the RR and QT intervals were measured. The QTc values showed a near normal distribution with mean +/- SD of 408 +/- 25 msec and a range (SD +/- 2 SD) of 458-358 msec.

The minimum QTc was 290 msec and only 3 subjects had QTc < 300 msec (Which was the definition of SQTS.) and none had clinical symptoms suggesting SQTS.

Clinical and electrocardiographic characteristics of patients with short QT interval in a large hospital-based population. Miyamoto A, Hayashi H, Toshino T, Kawaguchi A, Taniguchi A, Itoh H, Sugimoto Y, Itoh M, Makiyama Y, Xue JQ, Murakami Y, Horie M. Heart Rhythm 2012;9(1):66-74

Out of a hospital-based population of 114,334, there were 427 with short QT interval defined statistically (0.15 percentile) as QTcB </= 362 ms in males and </= 369 ms in females. Out of this group 327 patients were followed a mean of 54 months, and during that period 2 patients developed life-threatening events. One patient who also had early repolarization had recurrent VF related to bradycardia and another patient with Brugada type ECG after IV Pilsicainide had recurrent syncope during sleep. Genetic testing of these two patients was negative.

“By using QTcB to define a short QT interval, patients with SQTS may have been missed”

Identifying risk of cardiac events in short QT syndrome. Kobza R. Heart rhythm 2012;9(1):75-76 Editorial to the article above

PQ Segment Depression in Short QT Syndrome Patients: A novel Marker for Diagnosing Short QT Syndrome? Erol Tulumen, Carla Giostetto,Christian Wolpert C, Philippe Maury, Olli Anttonen, Vincent Probst, Jean-Jacques Blanc, Pascal Sbragia, Chiara Scrocco, Boris Rudic, Christian Veltman, Yasun Sub, Fiorenza Gaita, Charles Antzelevitch, Martin Borggrefe, Rainer Schimpf. Heart Rhythm 2014; 11(6): 1024-1030

Novel electrocardiographic criteria for short QT syndrome in children and adolescents Hiroshi Suzuki, Minoru Horie, Junichi Ozawa, Naokata Sumitomo, Seiko Ohno, Kenji Hoshino, Eiji Ehara, Kazuhiro Takahashi, Yoshichika Maeda, Masao Yoshinaga, Shigeru Tateno, Shozaburo Doi, Satoshi Hoshina, Isamu Sato, Taisuke Ishikawa, Naomasa Makita, Masaomi Chinushi, Kohei Akazawa, Masami Nagashima. Europace 2021;23(12):2029-2038