Lecture 7 - Channelopathies Flashcards
What causes long QT syndrome?
Mutations in genes which encode potassium (and sodium) ion channels
Potassium ion channels are very important in phase 3 (repolarisation), so mutations can lead to repolarisation abnormalities causing VT
What does a long QT ECG look like?
Measurement of QT lands outside the normal range
What can long QT syndrome cause?
‘torsades de points’ which is a variety of VT
What is VT?
Ventricular tachycardia - very fast rhythm, not compatible with effective output, doesn’t give the heart chance to fill
Does genetic abnormality = cardiac abnormality?
No, just because someone has genetic abnormality, it doesn’t mean they will suffer the cardiac abnormality
What is an EAD?
Early after depolarisation
What causes an EAD?
Abnormal potassium ion channels, so there is loss of function and repolarisation is impaired, so increased repolarisation leads to a longer QT phase, an EAD is where the cell undergoes an ap at the point of repolarisation
What causes Brugada syndrome?
Sodium ion channel abnormality in right ventricular (RV) epicardium
What does Brugada syndrome cause and in who?
Sudden cardiac death
Mean age of sudden death 41 +/- 15 years
Predominantly males (~75%)
What does Brugada syndrome look like on an ECG?
Weird ST segment, seen in the front chest lead reading on the ECG
What is CPVT?
Catecholaminergic Polymorphic Ventricular Tachycardia
How is CPVT similar to LQT?
Exercise-induced syncope (loss of consciousness), seizures or sudden death
How is CPVT different to LQT?
ECG at rest is typically normal
Why is it critical to distinguish between CPVT and LQT?
CPVT is more arrhythmic than LQT, higher estimated fatality in CPVT
What is a DAD?
Delayed after depolarisation
What happens in a DAD?
The cell recovers back to RMP, then during rest phase a DAD occurs instead of waiting for the next ap
What causes a DAD?
Seems to be a problem with calcium overload
Sarcoplasmic reticulum has a problem and spontaneously released calcium into the cell, an issue with ryanodine receptors
So, have spontaneous release of calcium so calcium exchanger is activated, so sodium gets brought into the cell which can build up and trigger a DAD
What are the treatments of LQT?
LQT1 - Beta blockers Avoidance of triggers LQT1 - swimming LQT2 - shock LQT3 - sleep
What are treatments of CPVT?
Beta blockers
Left cardiac sympathetic denervation - cut the sympathetic nervous supply to the heart
ICD - Implanted cardioverter defibrillator - sense abnormal heart rhythm and sends a short to restore normal rhythm
What are treatments of Brugada syndrome?
ICD - Implanted cardioverter defibrillator - sense abnormal heart rhythm and sends a short to restore normal rhythm
What is electrophysiology?
A wire that’s been put inside an individual’s heart, from the wire, the cardiologist is making measurements of electrical activity (basically an ECG from inside the heart)
Then can use a computer software to map the electrical activity and identify areas abnormal heart rhythm
If identify areas of abnormal activity they will destroy the area using ablation (killing defective cells), by either heating up the tissue or freezing it
This deals with the abnormal cells however it leaves scar tissue in the heart, which is another risk factor for abnormal rhythm
