15 - LQT Syndromes Flashcards
What are top 7 causes of sudden cardiac death in young people?
- Hypertrophic Cardiomyopathy (#1 in NA)
- RV Dysplasia (ARVC) (#1 in italy) (arrhythmogenic Right Ventricular Cardiomyopathy)
- Brugada Syndrome (#1 in Southeast asia)
- CPVT (catecholaminergic polymorphic ventricular tachycardia)
- Coronary Anomalies/Premature CAD (coronary artery disease)
- Long QT syndromes
- Short QT syndromes
Label the heart:
A) SA Node
B) Atria
C) AV Node
D) Purkinje
E) Ventricle
Where is the action potential seen in the image?
Label 0-4
Atria
0 - upstroke
1 - initial repolarization
2 - plateau
3 - Late repolarization
4 - rest (diastole)
The action potential in the image is seen in which area of the heart?
Label 0, 3, 4
What is important about phase 4?
SA Node
0 - Upstroke
3 - late repolarization
4 - depolarization in SA nodal cells
Phase 4 depolarization in SA nodal cells = pacemaker activity
SA node >> Atrial > Ventricle
Which area of the heart would create the action potential in the image?
Label 0-4
What is the arrow representing?
Ventricle
0 - upstroke
1 - Initial repolarization
2 - plateau
3 - late repolarization
4 - rest (diastole)
Arrow - transient outward K+ current through Ito channels = repolarizing - contributes to initial repolarization phase 1
Which ion channels contribute to depolarization?
- Ca++
- Na+
- Move into the cell
Nernst potential of:
- Ca++
- Na+
- Cl-
- K+
Nernst potential of:
- Ca++
- +150mV
- Na+
- +70mV
- Cl-
- -30 to -65mV
- K+
- -98mV (Resting Em)
Movement of ____ out of the cell causes ______
Movement of K+ out of the cell causes repolarization
There is constant recycling of ___ channels with every heart beat
There is constant recycling of Ca++ channels with every heart beat
Why does hyperkalemia cause QRS widening and asystole (eg lethal KCl injection)?
As serum potassium levels increase to greater than 6.5mM, the rate of phase 0 (upstroke/depolarization) of the action potential decreases leading to a longer action potential and, in turn, a widened QRS complex and prolonged PR interval
- delayed intraventricular and atrioventricular conduction
PR interval of ECG is related to ______ (ion moving)
PR interval of ECG is related to Na+ moving into cell - depolarization
The QRS interval of the ECG is related to which phase of the AP
ion moving in/out
The QRS interval of the ECG is related to action potential depolarization
The T wave of the ECG is associated with ________
ion moving in/out
The T wave of the ECG is associated with ventricular repolarization
K+ moving out of cell
What does the QT interval represent?
The time for both ventricular depolarization and repolarization to occur - estimates the duration of an average ventricular AP
Complete the table
K+ currents move _____ and cause _____. They are present in which phases of the ventricular AP?
K+ currents move outward and cause repolarization. They are present in which phases of the ventricular AP?
- Phase 1 - Ito
- Phase 2/phase 3 - IKr , hERG
- Phase 3 - IKs
- Phase 4 - IK1
Ito - transient outward K+ current
IKr , hERG - Rapidly activating delayed rectifying K+ current
IKs - Slowly activating delayed rectifying K+ current
IK1 - Inward rectifying K+ channels
What are the following channels and when are they active during ventricular AP?
- Ito
- IKr , hERG
- IKs
- IK1
Ito - transient outward K+ current
IKr , hERG - Rapidly activating delayed rectifying K+ current
IKs - Slowly activating delayed rectifying K+ current
IK1 - Inward rectifying K+ channels
- Phase 1 - Ito
- Phase 2/phase 3 - IKr , hERG
- Phase 3 - IKs
- Phase 4 - IK1
Na+ currents move _____ and cause _____. They are present in which phases of the ventricular AP?
Na+ currents move inward and cause depolarization. They are present in which phases of the ventricular AP?
Phase 0
Ca++ currents move _____ and cause _____. They are present in which phases of the ventricular AP?
Ca++ currents move inward and cause depolarization. They are present in which phases of the ventricular AP?
Phase 2 (phase 1 according to slide 11) (plateau phase)
L-type Ca++ channel (ICa,L)
Na+ current is a ______ current (phase _\_ of AP) Cardiac Sodium current is important for: (2)
Na+ current is a depolarizing current (phase 0 of AP) Cardiac Sodium current is important for: (2)
- AP duration (and QTc interval)
- Rapid Conduction eg. Purkinje fibres
Ca2+ current is a _____ current (phase __ of AP)
Cardiac Calcium current is important for: (2)
Ca2+ current is a depolarizing current (phase 1 of AP) (also phase 2 - plateau phase - very important for excitation contraction-coupling)
Cardiac Calcium current is important for:
- AP duration (and QTc interval)
- Triggers excitation-contraction coupling
K+ current is a _____ current (phase ___ of AP) Cardiac Potassium current is important for: (2)
K+ current is a repolarizing current (phase 2/3 of AP) Cardiac Potassium current is important for: (2)
- AP duration (and QTc interval)
- Repolarization
In 1957, Jervell and Lange-Nielsen reported a syndrome of congenital sensory deafness with a prolonged QT interval in four children: ______________
In 1957, Jervell and Lange-Nielsen reported a syndrome of congenital sensory deafness with a prolonged QT interval in four children: autosomal recessive…..LQT1 (and 5)
Romano–Ward syndrome is an ________ form of the long-QT syndrome NOT associated with deafness …higher incidence than JLN (jervell and Lange-Nielsen) syndrome, but affected persons generally have milder symptoms…….due to _______
Romano–Ward syndrome is an autosomal dominant form of the long-QT syndrome NOT associated with deafness …higher incidence than JLN (jervell and Lange-Nielsen) syndrome, but affected persons generally have milder symptoms…….due to LQT2, LQT3 and LQT4
