Cardiac Channelopathies Flashcards
What are the symptoms of long QT syndrome?
Fainting, dizziness, heart palpitations, congenital deafness
How does a long QT action potential differ from a normal ventricular action potential?
A long QT action potential is an action potential that is 0.45s or greater whereas a normal ventricular AP is roughly 0.36s
What are the origins of the symptoms of long QT syndrome?
Triggered activity occurs which leads to ectopic beats, resulting is ventricular tachycardia and ventricular fibrillation
Re-enterant excitation leads to spatial and temporal dispersion which leads to ventricular tachycardia and ventricular fibrillation
What are some of the K+ channel mutations that lead to long QT syndrome?
LQT1 - KCNQ1 encodes for Kv7.1a channel, loss of function mutation affects the Iks channel *30-35% of long QT due to this mutation
LQT2 - KCNH2 encodes Kv11.1a, loss of function mutation affects Ikr channel *25-30% of LQTS
LQT4 - ANK2 encodes Ankyrin B, loss of function mutation affects Ik channel *1-2% of LQTS
LQT5 - KCNE1 encodes for MinK, loss of function of regulator of Iks, *1% of LQTS
What are some of the Na+ channel mutations that lead to long QT syndrome?
LQT3 - SCN5A encodes Nav1.5a channel, gain of function mutation *5% of LQTS - deletion of three amino acids in the linker region
LQT4 - ANK2 encodes Ankyrin B, loss of function mutation affects Ina channel *1-2% of LQTS
What are the treatments for long QT syndrome?
Beta blockers such as atenolol that are B1 selective antagonists
What are the symptoms of short QT syndrome?
Arrhythmias, palpitations, syncope
How does a short QT action potential differ from a normal ventricular action potential?
Short QT action potentials are 0.34s or less compared to approximately 0.36s of a normal ventricular action potential
What are the causes of short QT syndrome?
SQT1 - KCNH2 gain of function mutation in Kv11.1a channels, Ikr
SQT2 - KCNQ1 gain of function in Kv7.1a channels, Iks
SQT3 - KCNJ2 gain of function in Kir2.1a, Ik1
SQT4 - CACNA1C loss of function in Cav1.2a, Ica
SQT5 - CACNB2 loss of function in Cav1.2b2, Ica
What are the treatments for short QT syndrome?
Defibrillator Quinidine (K+ channel blocker)