QTc Definition - Age and Sex Specific Criteria (Table)

QTc Definition - Age & Sex Specific Criteria (Table):

Reference: Ali A Sovari et al. (2010) Long QT Syndrome. (eMedicine Article)

Tags: Age - Definition - Long QT Syndrome - LQTS - QTc - Sex - Table

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Long QT Syndrome (LQTS) Diagnostic Criteria (1993) Table

Long QT Syndrome (LQTS) Diagnostic Criteria (1993) Table:

Legend:

* - In the absence of medications or disorders known to affect these electrocardiographic features.

† - QTc calculated by Bazett's formula where QTc=QT/RR(square root).

‡ - Mutually exclusive

§ - Resting heart rate below the second percentile for the age.

|| - Mutually exclusive

¶ - The same family member cannot be counted in A and B.

# - Definite LQTS is defined by an LQTS score of more than 3 (≥ 4).

Diagnostic Scoring:

• less than or equal to 1 point - low probability of LOTS.
• 2 to 3 points - intermediate probability of LOTS.
• > 4 points - high probability of LOTS.

Reference:

PJ Schwartz, AJ Moss, GM Vincent and RS Crampton. Diagnostic criteria for the long QT syndrome. An update. Circulation 1993;88;782-784

Tags: Bazett's formula - Congenital Deafness - Long QT Syndrome - LQTS - QTc - QT Interval - Stress - Sudden Cardiac Death - Sudden Death - Syncope - Torsade de Pointes - T-wave Alternans - Ventricular Tachyarrhythmias

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Romano-Ward Syndrome (LQT1 to LQT6)

Romano-Ward Syndrome Features:

• Major variant of long QT syndrome (abnormality on ECG - see opposite).
• Can lead to ventricular tachyarrhythmias.
• May lead to seizures, fainting, or sudden cardiac death.

Romano-Ward Syndrome Genetics:

• Inherited in an autosomal dominant pattern.
• Most common form of inherited long QT syndrome.
• Estimated to affect ~ 1 in 5,000 people, though may be more common than this because of non-symptomatic patients.
• 6 main forms noted (LQT1, LQT2, LQT3, LQT4, LQT5, LQT6).
• Associated with mutations in the ANK2, KCNE1, KCNE2, KCNH2, KCNQ1, and SCN5A genes.
• The proteins made by these genes lead to the proper formation of channels that transport positively-charged ions, such as potassium & sodium, in and out of cells.
• The ANK2 gene product has a function to ensure that proteins, particularly ion channels, are inserted into the cell membrane properly & appropriately.

Romano-Ward Syndrome Treatment:

• There is evidence that an imbalance between the right and left sides of the sympathetic nervous system may have a function in producing this symptomatic syndrome.
• A left stellate ganglion block, which shorten the QT interval, may redress this balance.
• In patients who respond to the stellate ganglion block may obtain lasting improvement with a surgical ganglionectomy.
• Drugs which prolong the QT interval should be avoided.
• Drugs which reduce serum potassium or magnesium should be avoided.
• Placement of an implantable cardioverter-defibrillator (ICD) is another treatment option in high risk patients.
• Competitive sport participation should be avoided for patients with the diagnosis established by means of genetic testing only.
• Beta-blocker therapy - ie propranolol or nadolol, reduce the risk or lethality of cardiac events.

Reference:

Ali A Sovari et al. (2010) Long QT Syndrome. eMedicine Article

Image: from Genotype and Severity of Long QT Syndrome. Jeffrey A. Towbin, Zhiqing Wang & Hua Li. © Drug Metabolism and Disposition (April 2001)

Tags: ANK2 - Beta-blocker - Ganglionectomy - ICD - KCNE1 - KCNE2 - KCNH2 - KCNQ1 - Long QT Syndrome - QT Interval - Romano-Ward Syndrome - SCN5A - Stellate Ganglion - Sympathetic Nervous System - Ventricular Tachyarrhythmias

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