Cardiac syncope and sudden death

History:

• sudden collapse
• no prodrome
• rapid recovery
• may have seizure activity
• pre-existing cardiac history
• malignant sounding family history
• black out with swimming/exercise/startle reflex: may be long QT syndrome
• blackout with stress/pain/adrenaline in children/teens: may be catecholinergic polymorphic VT

Examination:

• signs of heart failure/LV dysfunction
• carotid sinus hypersensitivity (elderly)

Investigations:

• ECG
• heart monitors: Holter ECG (1-7 days), ECG patch (14 days single lead), memo (self-applied), implantable loop recorder
• echo
• electrophysiological studies
• genetic testing

General:

• Q waves
• 1st, 2nd or 3rd degree heart block
• bifascicular or trifascicular block
• delta waves (especially children and young adults)
• epsilon waves

Specific:

• long QT syndrome (normal = 9-11 small squares)
• Brugada syndrome: ST elevation in V1-3
• short QT syndrome
• catecholenergic polymorphic VT: normal resting ECG, life-threatening VT/VF during times of emotional/physical stress

Channelopathy causing prolonged QT interval on ECG. Usually affects potassium channels but can affect sodium channels.

Sudden collapse, often caused by strenuous exercise (especially swimming) and 'startle reflex'.

Ix: ECG, may need an exercise ECG, may do genetic testing

Rx: ICD/pacemaker fitted, occasionally increased dietary potassium

Rare inherited channelopathy which disrupts flow of sodium/potassium ions INTO cardiomyocytes. 

Sx: light-headedness/dizziness, blackouts, palpitations. Sx may be brought on/exacerbated by fever, XS alcohol or dehydration. May present in arrest.

Ix: ECG, may require provocation test, genetic testing for patient and family members, electrophysiological tests (can decide if Rx is required if patient has no Sx)

Rx: ICD

Channelopathy causing short QT interval, short atrial and ventricular refractory periods and predisposition to atrial and ventricular fibrillation.

Mostly autosomal dominant

Often presents with arrest, other Sx include palpitations and syncope. Consider this in young patients with isolated AF.

Dx based on ECG, Sx and FH of arrest/syncope/AF at a young age. Exclude secondary causes of short QT (hyperthermia, hyperkalaemia, hypercalcaemia, acidosis, alterations of autonomic tone)

Rx: ICD

Blackouts/palpitations/dizziness in children and teens in response to stress/pain/adrenaline.

ECG: normal resting ECG, life-threatening VT or VF in times of emotional/physical stress (exercise test), bidirectional and polymorphic tachycardias

80% develop Sx by age 40 with mortality of up to 50%

Autosomal dominant: ryanodine receptor 2 mutations

Autosomal recessive: calcequestrian mutations

Autosomal dominant (most common genetic cardiac disease)

Most common cause of sudden cardiac death in young people and athletes

Characterised by LV hypertrophy, impaired diastolic filling and mitral valve abnormalities

LVH occurs due to disorganised cardiomyocytes from mutations in genes encoding sarcomeric proteins

Can cause impaired diastolic function, dynamic obstruction of LV outflow tract, myocardial ischaemia, increased risk of VT and SVT

Sx: SOB, palpitations, chest pain, syncope, forceful apex beat, AF

Weakened connecting proteins between cells leads to deposition of fat and fibrous tissue in between cells in response to stretch damage. Occurs mostly in the right ventricle and worsens with exercise.

Tends to cause a mixture of monomorphic VT and VF. 

Echo: increased RV dimensions, RV regional wall motion abnormalities, RV dysfunction. 

RV angiography considered gold standard but MRI has better sensitivity and specificity.

Beta blockers used for asymptomatic patients. ICD used if high risk

Chamber dilates and scars form- can be idiopathic in DCM or can occur due to actual scar in a post-infarct heart with super-added damage from neurohormonal response to chronic HF (aldosterone, adrenaline, ACE)

Mostly presents as congestive heart failure.

Important to ascertain family history to check for affected family members (for clinical and genetic testing)