What are the parameters for Short QT (SQTS) syndrome?

From the Guidelines

Short QT syndrome is diagnosed when the QTc interval on an electrocardiogram (ECG) is ≤340 ms, and it should be considered in the presence of a QTc ≤360 ms with additional risk factors such as a confirmed pathogenic mutation, family history of SQTS, family history of sudden death at age < 40 years, or survival from a VT/VF episode in the absence of heart disease. The diagnosis of short QT syndrome is based on the QTc interval, which is a critical parameter in assessing the risk of sudden cardiac death 1.

Diagnostic Parameters

The diagnostic parameters for short QT syndrome include:

• QTc interval ≤340 ms 1
• QTc interval ≤360 ms with additional risk factors such as:
  • Confirmed pathogenic mutation 1
  • Family history of SQTS 1
  • Family history of sudden death at age < 40 years 1
  • Survival from a VT/VF episode in the absence of heart disease 1

Management

Management of short QT syndrome typically includes implantable cardioverter-defibrillators for high-risk patients and antiarrhythmic medications like quinidine that can prolong the QT interval 1. Quinidine therapy has been shown to reduce the number of ICD shocks and may be an alternative to ICD implantation in selected patients 1.

Risk Assessment

The risk of sudden cardiac death is increased in patients with short QT syndrome, particularly those with markedly shortened QTc values ≤300 ms 1. A clinical score including QTc duration, clinical history, family history, and genetic findings can be used to identify patients at increased risk for sudden cardiac death 1.

From the Research

Parameters for Short QT Syndrome

The parameters for short QT syndrome include:

• A short QT interval, typically less than or equal to 320 ms 2, 3
• A corrected QT interval (QTc) less than or equal to 340 ms 3
• High risk of sudden death, atrial fibrillation, and short refractory periods 2, 4, 3, 5, 6
• Tall T waves in all lead electrocardiogram (ECG), peaked T waves, and narrow-based T waves 5
• Familial or personal history of cardiac arrest 4, 6
• Symptoms such as palpitations, syncope, and cardiac arrest 4, 3, 6

Diagnostic Criteria

The diagnostic criteria for short QT syndrome include:

• A 12-lead ECG showing a short QT interval and QTc 5
• Evaluation of symptoms such as palpitations and cardiac arrest 5
• Patient's family history 5
• Exclusion of structural heart disease 3

Treatment Options

The treatment options for short QT syndrome include:

• Implantable cardioverter-defibrillator (ICD) as the first-line therapy 4, 3, 5, 6
• Quinidine as a pharmacological therapy, especially in young children who are not feasible for ICD implantation 2, 4, 5, 6
• Hydroquinidine prophylaxis to prevent ventricular arrhythmias 4, 3, 6