Arrhythimias Flashcards
What are the electrical properites of cardiac cells?
- Automaticity. 2. Excitability. 3 Conductivity. 4. Refractoriness
Define chronotropic, inotropic, dromotropic and bathmotropic
C - frequency of the heartbeat
I - force of contraction of the heart
D - conduction of impulse through heart
B - excitability of cardiac muscle
Describe in detail the action potential of the heart
Upstroke. Then there is rapid depolarization, which means an opening of calcium channels. Then rapid repolarization, seen by the notch. Potassium moves out and calcium moves in. The plateau signifies the muscle still being depolarized. Calcium channels close. Final repolarization takes place and potassium channels close. The cell is slowly depolarized.
What do the diffrent points on the ECG represent?
P wave: atrial depolarization
QRS complex: ventricular depolarization
T wave: ventricular repolarization
PR interval: AV conduction
QT interval: ventricular action potential
ST interval: plateau portion of ventricular action potential
What is the function of the SA node?
The SA node is the pacemaker in the heart, governed by the autonomic nervous system
What are the 3 criteria for excitation?
Atrial excitation and contraction should be complete before the onset of ventricular contraction
Excitation of cardiac muscle fibres should be coordinated to ensure that each heart chamber contracts as a unit.
Both the atria and ventricles should contract simultaneously
What is delayed after depolarizations?
Elevated Ca, which can delay repolarization. This results in QT interval prolongation and can cause ventricular arrythmia
What are supraventricular arrythmias and give 3 examples?
All arrythmias that originate above the bundle of His. Examples are sinus bradycardia, sinus tachycardia, atrial flutter and atrial fibrillation
What is a sinoatrial block?
Its the failure of an inpulse being transmitted from the SA node to the AV node
What is an atrial flutter?
Charaterised by rapid ineffective atrial contractions where the rate is about 250 to 350 beats per minute
Why is ventricular fibrillation so dangerous?
This is a dangerous form of arrythmia because the ventricles cannot pump blood effectively and can lead to death
What is Torsades de Pointes?
It is a polymorphic ventricular tachycardia which is associated wtih twisting of QRE complexes and prolonged QT interval
What is the classification of antiarrhythmic drugs
Type 1 - target your sodium ions and your potassium ions
Type 2 - Calcium ions
Type 3 - Potassium ions
Type 4 - Calcium ions
List the main actions of AADs
Supress abnormal impulse formation and conduction. Drugs that block Na/Ca channels can reduce abnormal automaticity and slow conduction of cardiac muscle. Drugs that block K channels can prolong repolarization and the AP duration.
What is the mechanism of action of Class Ia drugs?
Block fast Na channels and delayed potassium channels. Slow phase 0 depolarization and phase 3 repolarization in ventricular tissue