Elsevier

Journal of Electrocardiology

Volume 43, Issue 5, September–October 2010, Pages 390-395
Journal of Electrocardiology

Short QT interval in clinical practice

https://doi.org/10.1016/j.jelectrocard.2010.06.004Get rights and content

Abstract

The last ten years have seen a growing interest in clinical scenarios, where a short QT interval may play a role, especially because of an increased risk of sudden cardiac death in some situations. One such entity is Short QT Syndrome, which has emerged as a rare, but very malignant disease, in particular when the QT interval is very short. A short QT interval has also been noticed in some patients with other arrhythmic syndromes such as Idiopathic Ventricular Fibrillation, Brugade Syndrome and Early Repolarization Syndrome, but the role of a short QT interval in these settings is so far not known. Hypercalcemia often leads to shortening of the QT interval, but there are no data in humans to suggest an increased risk of sudden cardiac death in this setting. In addition, a shorter-than-usual QT interval has been reported in patients with Chronic Fatigue Syndrome and in response to atropine, catecholamine and Hyperthermia.

When a short QT interval is encountered in daily clinical practice, these various scenarios needs to be considered, but it is still not possible to come up with clear guidelines for how to work up and risk stratify such individuals. Genetic testing is only useful in very few and the value of an electrophysiologic study, Holter monitoring or stress testing to assess QT adaptation to heart rate and T wave morphology analysis may all be helpful, but not well-established, tests in this setting.

Section snippets

Lower limit of normal for the QT interval

How to define universally accepted normal limits for the QT interval in an electrocardiogram (ECG) has been very difficult mainly because of methodological issues and the unpredictable variability of the QT interval with changes in heart rate and influences from the autonomic nervous system. Also, factors like age and sex, temperature, and electrolytes play a role, and so does the decision whether to measure the end of the QT interval at the end of the T wave or where a tangent to the down

Short QT interval and SQTS

Short QT syndrome is a rare form of hereditary channelopathy with an abnormally short QT interval and a high propensity to atrial and ventricular fibrillation (VF). Since it was discovered in 2000, only 53 members from 14 families and 10 sporadic cases of the disease have been published. The grave nature of the disease was underscored by the fact that 9 of the probands from the 14 families presented with cardiac arrest, and so did 5 of 10 sporadic cases.11 Initially, a diagnosis of SQTS was

Arrhythmogenesis and short QT interval

Before the discovery of SQTS, there was neither in isolation nor in connection with other electrocardiographic abnormalities any indication that a short QT interval was a risk factor for tachyarrhythmias and sudden cardiac death, but in the first family with SQTS, all members had atrial fibrillation at one time or another while the clinical presentation in other families primarily was ventricular tachyarrhythmias and often sudden cardiac death.

However, SQTS was found to be a genetically

Short QT interval and idiopathic VF

The notion that there might be patients with SQTS who have QT intervals longer than hitherto published with that syndrome stems primarily from observations by Viskin et al.23 They compared the ECGs of 28 patients with idiopathic VF (17 men and 11 women; age, 31 ± 17 years) with those of 270 age- and sex-matched healthy control subjects. The QTc of men with idiopathic VF was shorter than the QTc of healthy men (371 ± 22 vs 385 ± 19 milliseconds; P = .034), and 35% of the male patients had a QTc

Short QT interval and Brugada syndrome

Brugada syndrome is generally associated with either normal or a slightly prolonged QT interval particularly in the right precordial leads, but in 2007, Antzelevitch et al24 described a new syndrome consisting of familial sudden cardiac death syndrome in which a Brugada syndrome phenotype is combined with a short QT interval. By screening 82 consecutive probands with Brugada syndrome for ion channel gene mutations, they found 3 probands displaying ST-segment elevation in V1 through V3 and QTc

Short QT interval and early repolarization

Early repolarization is electrocardiographically characterized by an increase of 0.1 mV or higher of the QRS-ST junction (J-point) with slurring or notching of the end of the QRS complex with or without a J wave or J deflection and with or without ST-segment elevation. The changes are most commonly seen in mid-to-lateral precordial leads or inferior leads (II, III, and aVF). It is seen in 1% to 6% of the general population and usually regarded as a normal variant. Several reports within the

Short QT interval and hypercalcemia

Hypercalcemia (mild, when serum calcium is <12.5 mg/dL; moderate, 12.5-13.9 mg/dL; and severe, when serum calcium is ≥14.0 mg/dL) is most commonly seen in malignancies with osteolytic bone metastases, hyperparathyroidism, renal disease, and from medications such as thiazide diuretics, lithium, and vitamin D and is probably the best known reason for secondary short QT interval in clinical practice, described as early as 1922 by Carter and Andrus.29

The basis for the shortening of the QT interval

Short QT interval in other clinical situations

In addition, a shorter-than-usual QT interval has been reported in patients with chronic fatigue syndrome43 and in response to atropine,44 catecholamine,45 and hyperthermia.46

Paradoxical (deceleration-dependent) shortening of the QT interval

A few sporadic observations from the literature have confirmed the existence of situations where slowing of the heart rate is accompanied by shortening of the QT interval and not the normal response of prolongation of the QT interval. Thus, in 1999, we presented a 4-year-old African American girl with shortening of the QT interval during bradycardia.47 She was hospitalized with complications related to her premature birth, including developmental delay and several episodes of cardiac arrest. An

Suggested clinical implications

By definition, a short QT interval (QTc < 360 milliseconds in males and <370 milliseconds in females) is rare and is therefore a finding that should always lead to a search for a potential etiology. In daily clinical practice, most episodes of a short QT interval are a normally variant, with hypercalcemia and early repolarization next on the list. The most significant feature of a short QT interval is the occasional connection to an increased risk of sudden cardiac death. Because of the limited

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