Short QT on ECG

Assuming normal paper speed and voltage 

Sinus rhythm with upright p in lead II

PR interval is 110msec , could be normal for age, minimal delta wave could b appreciated in V5 , V6 , not prominent, narrow QRs

Qt is 240msec, Corrected for HR of 79, its 275 msec

T waves are spiked as well

QRS nothching in avF

Calcium, potassium levels to look

Short QT Syndrome (SQTS)

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Definition

Short QT Syndrome (SQTS) is a rare inherited cardiac channelopathy characterized by abnormally short QT interval on ECG, increased risk of atrial and ventricular arrhythmias, and sudden cardiac death in structurally normal hearts.

It results from mutations affecting cardiac ion channels leading to accelerated cardiac repolarization.

QTc is typically ≤330 ms, although QTc <360 ms with clinical features may also suggest the diagnosis.

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Epidemiology

• Very rare condition

• First described in 2000

• Affects both genders but slightly more common in males

• Often presents in young individuals or children

• Strong association with family history of sudden cardiac death

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Pathophysiology

Short QT syndrome results from gain-of-function mutations in potassium channels or loss-of-function mutations in calcium channels, leading to:

• Increased outward potassium currents

• Decreased inward calcium currents

This causes:

• Shortened action potential duration

• Reduced refractory period

• Increased susceptibility to re-entrant arrhythmias

Common genes involved include:

• KCNH2 (SQTS1)

• KCNQ1 (SQTS2)

• KCNJ2 (SQTS3)

• CACNA1C, CACNB2, CACNA2D1 (calcium channel related)

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ECG Features

Characteristic ECG findings include:

• QTc ≤330 ms (highly suggestive)

• QTc <360 ms with symptoms or family history

• Tall, narrow, peaked T waves

• Short or absent ST segment

• Rapid QT interval adaptation failure with heart rate changes

Other findings:

• Early onset atrial fibrillation

• Ventricular tachycardia or ventricular fibrillation

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Clinical Presentation

Patients may present with:

• Palpitations

• Syncope

• Atrial fibrillation at young age

• Ventricular tachyarrhythmias

• Sudden cardiac arrest

In some cases, sudden cardiac death may be the first manifestation.

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Diagnostic Criteria

Diagnosis is based on ECG findings plus clinical context.

Suggested criteria include:

QTc Based Criteria

• QTc ≤330 ms → Diagnostic

• QTc 331–360 ms → Consider SQTS if any of the following present:

– Pathogenic mutation

– Family history of SQTS

– Family history of sudden cardiac death before age 40

– History of ventricular arrhythmia

Exclusion of Secondary Causes

Short QT interval can also occur in:

• Hypercalcemia

• Hyperkalemia

• Acidosis

• Hyperthermia

• Digoxin effect

• Increased vagal tone

These must be excluded before diagnosing SQTS.

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Risk Stratification

High-risk features include:

• Prior cardiac arrest

• Documented ventricular fibrillation

• Family history of sudden cardiac death

• Extremely short QTc (<300–320 ms)

However, risk prediction remains challenging.

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Management

Implantable Cardioverter-Defibrillator (ICD)

ICD implantation is first-line therapy for secondary prevention.

Indications:

• Survivors of cardiac arrest

• Documented sustained ventricular arrhythmia

Challenges:

• T-wave oversensing due to tall T waves

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Pharmacological Therapy

Drug therapy is used when:

• ICD not feasible

• As adjunct therapy

• In asymptomatic high-risk patients

Most effective medication:

Quinidine

Effects:

• Prolongs QT interval

• Increases ventricular refractory period

• Suppresses ventricular fibrillation

Other drugs studied:

• Disopyramide

• Sotalol (limited effectiveness depending on genotype)

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Atrial Fibrillation Management

Patients often develop early-onset AF.

Treatment options include:

• Quinidine

• Standard AF management strategies

• Catheter ablation in selected patients

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Screening and Family Evaluation

Because SQTS is genetic:

• First-degree relatives should undergo ECG screening

• Genetic testing may be considered if mutation identified in proband

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Prognosis

Short QT syndrome carries a significant risk of malignant ventricular arrhythmias and sudden cardiac death, especially in untreated patients.

Early diagnosis and appropriate therapy, particularly ICD implantation in high-risk individuals, significantly improves outcomes.

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Key Points

• Rare inherited channelopathy causing abnormally short QT interval

• Associated with atrial fibrillation, ventricular arrhythmias, and sudden death

• QTc ≤330 ms strongly suggests diagnosis

• ICD is the mainstay of treatment for high-risk patients

• Quinidine is the most effective pharmacologic therapy