| Literature DB >> 27480102 |
Andrew T Gomez1, Jordan M Prutkin2, Ashwin L Rao3.
Abstract
CONTEXT: The congenital long QT syndrome (LQTS) is an inherited channelopathy known for its electrocardiographic manifestations of QT prolongation and its hallmark arrhythmia, torsades de pointes (TdP). TdP can lead to syncope or sudden death and is often precipitated by triggers such as physical exertion or emotional stress. Given that athletes may be at particular risk for adverse outcomes, those suspected of having LQTS should be evaluated, risk stratified, treated, and receive appropriate counseling by providers with sufficient expertise according to the latest guidelines. EVIDENCE ACQUISITION: The following keywords were used to query MEDLINE and PubMed through 2016: LQTS, LQT1, LQT2, LQT3, long QT, long QTc, prolonged QT, prolonged QTc, QT interval, QTc interval, channelopathy, channelopathies, athletes, torsades de pointes, and sudden cardiac death. Selected articles within this primary search, in addition to relevant references from those articles, were reviewed for relevant information and data. Articles with pertinent information regarding pathophysiology, evaluation, diagnosis, genetic testing, treatment, and guidelines for athletes were included, particularly those published in the prior 2 decades. STUDYEntities:
Keywords: arrhythmia; athletic participation; long QT syndrome; sudden cardiac death
Mesh:
Year: 2016 PMID: 27480102 PMCID: PMC5089354 DOI: 10.1177/1941738116660294
Source DB: PubMed Journal: Sports Health ISSN: 1941-0921 Impact factor: 3.843
Figure 1.Action potential, currents, and electrocardiogram (ECG) findings. The figure outlines, conceptually, the connection between action potential prolongation, ECG findings, and the associated currents in LQT1-3.
Figure 2.Torsades de pointes (TdP): A rapid polymorphic ventricular tachycardia characterized by varying amplitudes that seem to twist around a central axis. TdP may degenerate into ventricular fibrillation.
Figure 3.Using Bazett’s correction with the above QT (490 ms) and RR (0.91 s), the patient’s QTc is 514 ms.
Figure 4.The “Teach-the-Tangent” method or “Avoid-the-Tail” method of measuring the QT interval in the presence of a U-wave.
Formulas to calculate the QTc[ ]
| Name | Formula |
|---|---|
| Bazett | QTc = QT / √RR |
| Fredericia | QTc = QT / 3√RR |
| Framingham | QTc = 0.154 (1000 − RR) |
| Hodges | QTc = QT + 105 (1 / RR − 1) |
Formulas published by Luo et al.[15]
Figure 5.Various T-wave configurations in the most common long QT syndromes (LQTSs). (a) LQT1 is associated with broad-based T-waves. (b) LQT2 is often associated with bifid or notched T-waves. LQT3 is associated with (c) biphasic or (d) asymmetrical and peaked T-waves.
Figure 6.T-wave alternans, a finding associated with electrical instability often preceding torsades de pointes.
1993-2011 LQTS diagnostic criteria[ ]
| Points | |
|---|---|
|
| |
| QTc[ | 321 |
| QTc[ | 1 |
| Torsades de pointes[ | 2 |
| T-wave alternans | 1 |
| Notched T-wave in 3 leads | 1 |
| Low heart rate for age[ | 0.5 |
|
| |
| Syncope[ | 21 |
| Congenital deafness | 0.5 |
|
| |
| Family members with definite LQTS[ | 1 |
| Unexplained sudden cardiac death below age 30 years among immediate family members[ | 0.5 |
LQTS, long QT syndrome.
Table adapted from Schwartz and Crotti.[26] Score: ≤1 point, low probability of LQTS; 1.5 to 3 points, intermediate probability of LQTS; ≥3 points, high probability of LQTS.
QTc calculated using Bazett’s formula.
Mutually exclusive.
Resting heart rate below the 2nd percentile for age.
The same family member cannot be counted in either row 1 or 2 of this category.