Short QT syndrome electrocardiogram
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]
Overview
The electrocardiographic manifestations of short QT syndrome vary depending upon the underlying genetic abnormality, but generally include a QTc < 360 mseconds, lack of variability in the QTc with heart rate, either a tall peaked T wave or Brugada pattern in V1 and V2, early repolarization and paroxysmal atrial fibrillation as a rhythm.
Duration of the QT Interval
Shown below is an example of short QT interval.
While the QT interval is generally short, the QT interval alone cannot be used to distinguish the patient with short QT syndrome from a normal patient (similar to long QT syndrome).[1] In general though, if the QTc is < 330 msec in a male, and <340 msec in a female, then short QT syndrome can be diagnosed even in the absence of symptoms as these QT intervals are much shorter than in the rest of the population. On the other hand, if the QTc is moderately shortened to < 360 msec in a male or < 370 msec in a female, the short QT syndrome should only be diagnosed in the presence of symptoms or a family history given the overlap of these QT intervals with that of the healthy population.
SQTS 1,2,3
The QTc is < 300-320 msec.[2][3][4]
SQTS 4,5
The QTc is just under 360 msec [5]
Variability of the QT Interval with Heart Rate
The short QT interval does not vary significantly with the heart rate. Normally the QT will become longer at slow heart rates and this does not occur among patients with short QT syndrome. The Bazett formula may overcorrect (i.e. shorten) the QT interval in the patient with bradycardia, and it is therefore important to use treadmill testing to increase the heart rate and confirm the absence of QT interval variation.[6]
Morphology of the T Wave
SQT1
Tall, narrow, peaked, symmetric T waves in the right precordial leads.
SQT3
Asymmetric peaked T waves due to more rapid repolarization at the end of the T wave.
SQT4 and 5
There is Brugada syndrome-like ST segment elevation in leads V1 and V2.
Morphology of the ST Segment
The ST segment is short or even missing. The T wave begins right after the S wave.
Early Repolarization
In a very limited number of patients it has been observed that early repolarization (which is present in 65% of patients with SQTS) and a longer T wave peak to T wave end period is associated with the occurrence of arrhythmic events[7].
Rhythm
70% of patients with short QT have a history of either paroxysmal atrial fibrillation or permanent atrial fibrillation, and atrial fibrillation is the first sign of short QT syndrome in 50% of patients. In young patients with lone atrial fibrillation, the patient should be screened for short QT syndrome.
References
- ↑ Viskin S. The QT interval: Too long, too short or just right. Heart Rhythm 2009; 6: 711–715.
- ↑ Brugada R, Hong K, Dumaine R, Cordeiro J, Gaita F, Borggrefe M, Menendez TM, Brugada J, Pollevick GD, Wolpert C, Burashnikov E, Matsuo K, Wu YS, Guerchicoff A, Bianchi F, Giustetto C, Schimpf R, Brugada P, Antzelevitch C (2004). "Sudden death associated with short-QT syndrome linked to mutations in HERG". Circulation. 109 (1): 30–5. doi:10.1161/01.CIR.0000109482.92774.3A. PMID 14676148. Retrieved 2012-09-03. Unknown parameter
|month=ignored (help) - ↑ Bellocq C, van Ginneken AC, Bezzina CR, Alders M, Escande D, Mannens MM, Baró I, Wilde AA (2004). "Mutation in the KCNQ1 gene leading to the short QT-interval syndrome". Circulation. 109 (20): 2394–7. doi:10.1161/01.CIR.0000130409.72142.FE. PMID 15159330. Retrieved 2012-09-03. Unknown parameter
|month=ignored (help) - ↑ Priori SG, Pandit SV, Rivolta I, Berenfeld O, Ronchetti E, Dhamoon A, Napolitano C, Anumonwo J, di Barletta MR, Gudapakkam S, Bosi G, Stramba-Badiale M, Jalife J (2005). "A novel form of short QT syndrome (SQT3) is caused by a mutation in the KCNJ2 gene". Circulation Research. 96 (7): 800–7. doi:10.1161/01.RES.0000162101.76263.8c. PMID 15761194. Retrieved 2012-09-03. Unknown parameter
|month=ignored (help) - ↑ Antzelevitch C, Pollevick GD, Cordeiro JM et al. Loss-of-function mutations in the cardiac calcium channel underlie a new clinical entity characterized by ST- segment elevation, short QT intervals, and sudden cardiac death. Circulation 2007: 115: 442-449.
- ↑ Moreno-Reviriego S, Merino JL.Short QT Syndrome. An article from the E-Journal of the ESC Council for Cardiology Practice. Vol9 N°2, 17 Sep 2010 [1]
- ↑ Watanabe H, Makiyama T, Koyama T, Kannankeril PJ, Seto S, Okamura K, Oda H, Itoh H, Okada M, Tanabe N, Yagihara N, Kamakura S, Horie M, Aizawa Y, Shimizu W (2010). "High prevalence of early repolarization in short QT syndrome". Heart Rhythm : the Official Journal of the Heart Rhythm Society. 7 (5): 647–52. doi:10.1016/j.hrthm.2010.01.012. PMID 20206319. Retrieved 2012-09-03. Unknown parameter
|month=ignored (help)