Carol Jacobson RN, MN www.cardionursing.com 1 Relax and Learn at the Farm 2013 Sudden Cardiac Death Channelopathies Abnormalities in ion channels that control entry of ions into or out of the cardiac cell – especially Na + and K + Genetic channelopathies Long QT Syndrome Short QT Syndrome Brugada Syndrome Catecholaminergic Polymorphic VT Arrhythmogenic Right Ventricular Cardiomyopathy
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Carol Jacobson RN, MN www.cardionursing.com 1
Relax and Learn at the Farm
2013
Sudden Cardiac Death
Channelopathies
Abnormalities in ion channels that control entry of ions into
or out of the cardiac cell – especially Na+ and K+
Genetic channelopathies
Long QT Syndrome
Short QT Syndrome
Brugada Syndrome
Catecholaminergic Polymorphic VT
Arrhythmogenic Right Ventricular Cardiomyopathy
Carol Jacobson RN, MN www.cardionursing.com 2
Na+
Ca++
K+ Na+ entering cell
is responsible for
depolarization
K+ leaving cell is
responsible for
repolarization
3 Na+ out
2 K+ in
Na+
Ca++
K+
Cardiac Action Potential
Carol Jacobson RN, MN www.cardionursing.com 3
SO . . . .
Anything that causes the cell to remain positive
inside longer than normal delays its repolarization
back to the resting state and prolongs repolarization
and the QT interval
Drugs that block potassium channels: some
antiarrhythmics, antidepressants, many others
Genetic abnormalities of the potassium channel
Genetic abnormalities of the sodium channel
Channelopathies
Linked to sudden infant death syndrome and SCD in
young people
Suspect and rule out in children or teenagers with
unexplained syncope or cardiac arrest
Primary presenting symptom in most people is syncope –
which can resolve or result in SCD
SCD is often the first symptom of Brugada syndrome and
hypertrophic cardiomyopathy
Carol Jacobson RN, MN www.cardionursing.com 4
Congenital Long QT Syndromes
Hereditary gene mutations that affect sodium or
potassium ion channels on cardiac cell membranes
Associated with increased risk of SCD due to
ventricular arrhythmias (TdP)
13 different genes identified so far – labeled LQT1
through LQT13
Congenital LQTS
LQT1 and LQT2 account for about 90% of
congenital cases
Affect potassium channels and cause reduction in
repolarizing potassium current
LQT3 accounts for about 5% - 8%
Affects sodium channels and causes an increase in sodium
current entering cell
Other types are very rare
Carol Jacobson RN, MN www.cardionursing.com 5
QT interval prolongation is a critical part of diagnosis
LQT1: wide, broad-based T waves
LQT2: low amplitude, often notched T waves
LQT3: long ST segment and tall, peaked T waves
Triggers for Torsades in Congenital LQTS
LQT1
Exercise: exaggerated QT prolongation during exercise
Swimming or diving: initiates diving reflex and slows HR
LQT2
Emotions
Sudden noise (alarm clock, phone)
Pause dependent TdP common with LQT2 but not others
LQT3
On awakening
During sleep
Carol Jacobson RN, MN www.cardionursing.com 6
2 week old QTc during 1:1 conduction = 414 ms
Same 2 week old during 2:1 block
QTc = 550ms
Carol Jacobson RN, MN www.cardionursing.com 7
2 year old with 2:1 block
QTc = 695 ms
13 year old girl arrested at a slumber party
Rhythm strips from AED after medics arrived
Carol Jacobson RN, MN www.cardionursing.com 8
13 year old girl arrested at a slumber party
QTc = 576 ms
Management of Congenital LQTS
Preventive Measures
Avoid loud noises and activities that trigger adrenergic
surges
Remove or blunt alarm clocks, phones, other loud devices
Avoid places where sudden noise or stress could occur: roller
coasters, loud music
No competitive sports
Avoid QT prolonging drugs
Prevent electrolyte depletion
Carol Jacobson RN, MN www.cardionursing.com 9
Management of Congenital LQTS
Beta blockers (antiadrenergic effects)
Mainstay of therapy for congenital LQTS
Especially effective in LQT1 patients, least effective in LQT3
Dual chamber pacing at a rate to shorten QT
ICD
Patients who have survived cardiac arrest
Patients who continue to have cardiac events (VT, syncope,
aborted SCD) on beta blockers
High-risk LQT2 and LQT3 patients benefit most
Clinical Implications of a
Short QT Interval
First described in 2000
Inherited channelopathy involving gene mutations
that affect potassium channels
5 types identified so far
Characterized by:
Constantly short QT interval <320 ms
Associated with atrial fibrillation
Syncopal episodes
SCD
Carol Jacobson RN, MN www.cardionursing.com 10
Other potential causes of a short QT interval should
be ruled out:
Hyperkalemia, hypercalcemia
Hyperthermia
Acidosis
Digitalis use also shortens the QT
Determination of QT interval in SQTS:
HR should be < 100
Bazett formula not recommended: it provides a longer
QTc than is really present
SQTS
ECG characteristics
QT <320 ms
Tall, peaked T waves in precordial leads
No or very short ST segment
Presentation ranges from asymptomatic to syncope
to SCD
30% incidence of atrial fib, occurs at all ages
Management is ICD implantation
Carol Jacobson RN, MN www.cardionursing.com 11
21 year old woman with cardiac arrest
Defibrillated and brought to ED
Lab work normal
Causes of short QT ruled out
Went in to VF again, resuscitation was unsuccessful
QT = 240 ms
Brugada Syndrome
Inherited channelopathy involving mutations of the SCN5A
gene that participates in regulation of cardiac sodium channels
Usually no structural heart disease
Seen worldwide but is most prevalent in southeast Asia (very
common in Thailand)
Occurs most often in men (8:1 male to female ratio)
Usually manifests in 3rd or 4th decade of life but can be seen in
children
Associated with high incidence of SCD due to lethal
ventricular arrhythmias
Responsible for at least 4% of all sudden deaths and at least 20% of
sudden deaths in patients with structurally normal hearts
Carol Jacobson RN, MN www.cardionursing.com 12
Brugada Syndrome
ECG Criteria
RBBB pattern in V1 to V2/V3
Often no S waves in lateral leads as with RBBB
J point elevation in V1 to V2/V3
ST elevation in V1 to V2/V3
QT interval sometimes mildly prolonged
ECG can be transiently normal
Brugada Syndrome
Clinical Presentation
Dizzy spells, lightheadedness
Seizures
Syncope or near syncope
Palpitations
Sudden Cardiac Death – often the first “symptom”
Symptoms usually occur during rest and at night, but 15%
of patients have symptoms during exercise
Fever can trigger the ECG changes and arrhythmia episodes
(cardiac arrest)
Cocaine abuse and other drugs can bring out ECG changes
All related to life
threatening ventricular
arrhythmias
Carol Jacobson RN, MN www.cardionursing.com 13
3 ECG Patterns of Brugada
Type 1: “Coved type” - elevated ST segment (≥2 mm) descends with an upward
convexity to an inverted T wave.
Type 2: “Saddle-back type”- high takeoff ST elevation > 2 mm followed by ST
elevation > 1 mm and a positive or biphasic T wave.
Type 3: ST elevation < 1 mm with coved or saddle-back pattern
Diagnostic Criteria for Brugada Syndrome
Type 1 ECG pattern in more than one right chest lead (V1-V3)
and at least one of the following:
Documented VF or polymorphic VT
Family history of sudden cardiac death at <45 years
Type 1 ST segment elevation in family members
EPS inducibility of VT/VF
Unexplained syncope suggestive of a tachyarrhythmia
Nocturnal agonal respiration
Type 2 or 3 pattern that converts to Type 1 with sodium
channel blocking drugs plus one of above criteria
Carol Jacobson RN, MN www.cardionursing.com 14
Brugada Syndrome
19 year old male with history of dizzy spells. Type 3 ECG pattern
Young man with history of “seizures”
Type 1 ECG pattern
Brugada Syndrome
Carol Jacobson RN, MN www.cardionursing.com 15
Treatment of Brugada
ICD
Class I recommendation for SCD survivors
Class IIa recommendation for BS patients with syncope or
documented VT
No proven pharmacologic treatments for preventing
SCD
Quinidine has been effective
No consensus on how to treat asymptomatic patients
Catecholaminergic Polymorphic VT
Occurs in absence of structural heart disease and
typically begins in adolescence or childhood
Mutations in two genes have been identified
Patients typically present with life-threatening VT or
ventricular fibrillation (VF) occurring during emotional
or physical stress
Syncope is often the first manifestation
Carol Jacobson RN, MN www.cardionursing.com 16
CPVT
ECG in sinus rhythm is usually normal (no long QT)
Two types of polymorphic VTs have been described: "Typical" polymorphic VT with continuously varying QRS
morphology (similar to ischemia related PVT in patients with normal QT interval)
Bidirectional ventricular tachycardia with alternans of the QRS complexes
Management: Cardioversion if sustained and unstable
IV beta blockers
Amiodarone as long as QT is not prolonged
ICD
Catecholaminergic VT
Carol Jacobson RN, MN www.cardionursing.com 17
Arrhythmogenic Right Ventricular
Cardiomyopathy (ARVC)
An inherited heart-muscle disease that is a major cause
of sudden death in young people and athletes.
Estimated to occur in 1:2000 to 1:5000 people
Affects men more often than women (3:1 ratio)
Characterized by
Replacement of myocardium in the RV by fibro-fatty tissue
Ventricular arrhythmias
The left ventricle can also be involved.
Carol Jacobson RN, MN www.cardionursing.com 18
Presentation of ARVC
• Adolescents or young people with
palpitations, syncope, or aborted
sudden death.
• ECG changes:
– T wave inversion in V1–V3
– Epsilon waves at end of QRS in V1-V3
– PVCs of left bundle branch block
morphology (>500/24h)
• VT of left bundle branch block
morphology
VT with LBBB pattern, often occurs with exercise
Carol Jacobson RN, MN www.cardionursing.com 19
Treatment
There is no cure – can progress to heart failure
Main Goal: Prevention of SCD ICD therapy is indicated for secondary prevention after prior
cardiac arrest and in patients with hemodynamically unstable VT
Antiarrhythmic drugs Not equivalent to ICD
Adjunctive therapy with amiodarone or sotalol for frequent VT and ICD shocks
Beta blockers may be helpful
Activity Restriction No competitive sports (VT often occurs with exercise)