Arrhythmias Flashcards
What is the role of the SA node
Generates a normal heart rhythm.
How does the SA node fire
Spontaneous
What is the ocation of the SA node
The interface between the superior vena cava and the right atrium
What is the nature of the cells in the SA node
Specialised conducting tissue.
What is the AV node
The electrical connection between the atria and the ventricles.
What is represented by the QRS complex
Depolarisation and contraction of the ventricles.
what are the indications of the size of the QRS complex
Length of time taken for the ventricles to contract.
what are the indications of a long QRS complex
An enlarged heart.
What is represented by the gap between the P wave and the QRS complex
Time delay introduced by the AV node activation.
What is represented by the T wave
Ventricular diastole - where the ventricles are relaxing/repolarising after one cardiac cycle.
What is represented by the PR interval
The start of atrial activation to the start of ventricular activation
What is the indication of a long PR interval
An issue with the AV node
What is the indication of a short PR interval
An accessory pathway is active which conducts faster than the AV node
What is represented by the QT interval
The start of ventricular activation to the start of repolarisation.
What is long QT syndrome
A problem with ventricular repolarisation (diastole).
What is the impact of long QT syndrome
Lethal rhythms.
What are the names of the four heart valves
Tricuspid, mitral, pulmonary and aortic.
What is the role of the fibrous rings surrounding the valves
Electrical insulation.
What is the role of the AV node
To slowly conduct the impulse from the atria to the ventricles to introduce a time delay so the ventricles contract after the atria.
what is the role of the perkinje fibres
To spread the impulse quickly through both ventricles.
What are the branches of the bundle of his
Right bundle branch and left bundle branch.
What is one second represented by on an ECG graph
5 large squares (25mm)
How do you work out heart rate from an ECG trace
Count the number of large squares between successive heart beats and divide 300 by this number.
What is a normal PR interval
3 to 5 small squares
What is the impact of breathing on heart rate.
When you breath in you draw blood from your vena cavae into the heart and increase pressure in the chest to reduce heart rate.
What modulates the heart rate
The parasympathetic nervous system through vagus nerve activation.
What is a sinus arrhythmia
The sinus node fires at a variable rate. It speeds up during inspiration and slows down during expiration.
What is tachycardia
Heart rate of 100bpm or more,
What is bradycardia
Heart rate of 60bpm or less.
What is sinus tachycardia
Tachycardia coming from the SA node.
What ate the normal causes of sinus tachycardia
Exercise or stress
What are the pathological causes of sinus tachycardia
Fever, anaemia, hyperthyroidism, heart failure and others.
What is atrial fibrillation
Loss of co-ordination of contraction.
What is the main cause of atrial fibrillation
Age
What are the complications of atrial fibrillation
Increased risk of clotting and subsequently stroke.
What drugs are used in atrial fibrillation to decrease the risk of stroke
Anticoagulants
What is sino-atrial disease
Mixture of sinus-tachycardia, bradycardia and atrial “ectopic” beats (atrial fibrillation)
What is the treatment for sino-atrial disease
A permanent pacemaker to prevent slow rhythms or antiarrhythmic drugs to prevent rapid rhythms.
What are two examples of anti-arrhythmic drugs
Digoxin, amiodarone.
what are the normal causes of sinus bradycardia
Sleep, athletic training.
What are the pathological causes of sinus bradycardia
Hypothyroidism, hypothermia, sinus node disease, raised inter-cranial pressure.
what is a possible cause of a blackout
Rhythm problems - the SA node may stop firing for a short time.
What is type 1 AV block
A problem with the AV node causing a long delay (long PR interval) however, the signal still reaches the ventricles.
What is second degree AV block
The AV node becomes more fatigued with every heart beat and the signal does not reach the ventricles every time.
What is complete AV block
There are no P waves conducting to the ventricles.
What is the back-up mechanism for complete AV block
The ventricles can conduct themselves. It is abnormal activation but enough to allow blood to be distributed around the body for a short while.
What is the treatment for complete AV block
Permanent pacemaker.
What are some possible causes of damage to the AV node
Disease of the aortic valve which is close by, coronary heart disease, damage during heart surgery, sino-atrial disease, drugs (beta-blockers, digoxin, calcium channel blockers).
What us used for the treatment of AV nodal block
Removal of any triggers such as drugs, fitting of a permanent pacemaker, atropine or isoprenaline.
What is the action of atropine in the treatment of AV nodal block
Blocks the inhibition which vagus nerves give the heart rhythm (through the parasympathetic nervous system)
What is the action of isoprenaline in the treatment of AV nodal block
Stimulates the sympathetic nervous system.
What is the indication of a saw tooth wave which shows a flutter
A short circuit in the right atrium - atrial fibrillation.
What are the causes of atrial fibrillation
Sino-atrial disease, coronary heart disease, valve disease (especially mitral valve), hypertension, cardiomyopathy, hyperthyroidism, pneumonia.
What is used in the treatment of atrial fibrillation
A drug to block the AV node and limit heart rate (such as digoxin or a beta-blocker), electrical cardioversion.
what are the indications of a fast rhythm with no clear P wave
Ventricular tachycardia
what are the indications of a fast rhythm with a clear P wave
Sinus tachycardia
What is the impact of ventricular tachycardia
Life threatening - not compatible with consciousness.
What is the emergency treatment for ventricular tachycardia
Immediate defibrillation.
