Presentation: Adult with short QT syndrome

A 30-year-old man presents to the emergency department with breathlessness, palpitations and a persistent feeling of impending doom. His admission electrocardiogram (ECG) shows atrial fibrillation with a ventricular rate of 163bpm. This is cardioverted using IV metoprolol. Later, he has multiple episodes of sustained ventricular tachycardia which require direct current cardioversion treatment. The resting ECG demonstrates sinus rhythm at 75bpm with a short QT interval (QTc = 328 ms).

Genomic testing should be considered in the following scenarios.

• A firm clinical diagnosis of short QT syndrome (SQTS), as indicated by:
  • a QTc ≤330 ms; or
  • a QTc <360 ms and one or more of the following:
    • a family history of SQTS;
    • a family history of sudden death at ≤40 years of age; and/or
    • patient has survived a ventricular tachycardia or ventricular fibrillation episode in the absence of heart disease.
• Genomic testing should be carried out in parallel with expert phenotypic assessment – for example, in an inherited cardiac conditions (ICC) clinic – and with support from clinical genetics. Note that testing may occasionally be appropriate outside these criteria following discussion in an ICC multidisciplinary team meeting.
• Referrals for genomic testing will be triaged by the genomic laboratory. Testing should be targeted at those in whom a genetic or genomic diagnosis will guide management of the proband and/or their family.
• Testing should also be considered in first-degree relatives of a patient with confirmed SQTS whose condition is associated with an identified familial variant.
• If the patient fulfils diagnostic criteria as detailed in published guidelines that differ from the eligibility criteria in the National Genomic Test Directory, it is appropriate to refer the case to an ICC clinic for further assessment.

• Consult the National Genomic Test Directory. From here you can access the rare and inherited disease eligibility criteria for information about individual tests and their associated eligibility criteria. You can also access a spreadsheet containing details of all available tests.
• To find out which genes are included on different gene panels, see the NHS Genomic Medicine Service (GMS) Signed Off Panels Resource.
• The relevant clinical indication for adults with suspected SQTS is:
  • R130 Short QT syndrome: This indication comprises small gene panel sequencing and multiplex ligation-dependent probe amplification (MLPA) or equivalent.
• For tests that do not include whole genome sequencing, you will need to:
  • complete a test order form and consent (record of discussion) form, available from your local Genomic Laboratory Hub; and
  • include details of the phenotype in the test order form (refer to human phenotype ontology (HPO) terms or the clinical summary) as well as the appropriate panel name(s) with associated R number.
• The tests outlined above are DNA based, and an EDTA sample (purple-topped tube) is required.
• Information about patient eligibility and test indications was correct at the time of writing. When requesting a test, please refer to the National Genomic Test Directory to confirm the right test for your patient.

For clinicians

• European Society of Cardiology: Short QT syndrome
• NHS England: National Genomic Test Directory

For patients

• British Heart Foundation: Life with sudden arrhythmic death syndrome
• Cardiac Risk in the Young
• myheart: Short QT syndrome
• SADS Foundation: Short QT syndrome
• Short QT Syndrome