Cardiac arrhythmias Flashcards
What is an arrhythmia?
It is an abnormality in heart rate (where number of beats per minute can increase or decrease) and/or abnormality In the rhythm (irregular beats- they can be regularly irregular where the irregular rhythm continues all the time or irregularly irregular meaning that irregularity in the cardiac rhythm comes and goes and in-between it is normal).
- Some cardiac arrhythmias are benign and have no clinical consequences.
- Some cardiac arrhythmias are potentially fatal
What is “normal” cardiac rhythm described as?
Sinus rhythm (NSR)
What is supraventricular cardiac arrhythmia?
Arrythmias occur anywhere else other than the ventricles
- Could be above the AV node (atrial arrythmias)
- At the AV junction
- Within the AV node
Originates from the atria:
- Sinus tachycardia
- Sinus node re-entry tachycardia
- Atrial fibrillation (MAIN)
- Atrial flutter
- Atrial tachycardia
Originates from the AV junction:
- AV junction tachycardias
- Wolff-Parkinson White Syndrome
What is ventricular cardiac arrhythmia?
Occur and originate within the ventricles
Ventricular tachycardias (more problematic and potentially fatal):
- Ventricular ectopics
- Torsades de pointes
- Ventricular fibrillation (more serious - CARDIAC ARREST)
What Is bradycardia?
Slow heart rate
- Defined as being less than 60 beats per minute
What is tachycardia?
Fast heart rate
- Defined as being more than 100 beats per minute
What are the common symptoms of cardiac arrythmias?
- Dizzy/light headed
- Palpitations (they are aware and can feel the heartbeat)
- Chest pain
- Fatigue
- Occasionally patients with cardiac arrythmias can lose consciousness and is usually secondary to a sudden drop in blood pressure and a sudden drop in blood flow due to circulation issues due to the arrhythmia
- Small number of arrythmias result in a cardiac arrest
What is done for the management of cardiac arrythmias?
- To identify the underlying disease/cause of the cardiac arrhythmia.
- E.g. Thyroid diseases both hypo and hyperthyroidism can cause cardiac arrythmias, electrolyte imbalances can also cause cardiac arrythmias or cardiomyopathy/disfunction of the cardiac muscle. - Drug therapy
- Non-pharmacological
- Electrical cardio version
- Radiofrequency ablation / cryoablation
- Pacemakers
- Defibrillators
What are the 3 different types of bradycardia?
- Sinus bradycardia
- Sinus node disease
- AV node disease: ‘Heart block’
What is sinus bradycardia?
Is when the SA node fires at a slow rate.
What is sinus node disease?
When the SA node fails to generate an electrical impulse.
- Mainly idiopathic (cause unknown/spontaneous) - often cause if fibrosis of conduction tissue
- Some sinus node disease is secondary to acute myocardial infarction or cardiomyopathies (diseases of the cardiac muscle)
What is AV node disease?
Failure of AV node to conduct electrical impulse to ventricles.
- Frequently idiopathic (cause unknown/spontaneous)
- Also can be secondary to acute myocardial infarction, congenital defects, infection, surgery (valve) and drugs such as B-blockers, digoxin and verapamil.
Also known as Heart Block
What are the management options for bradycardia?
- Establish underlying cause (stop drugs, treat disease e.g. hypothyroidism)
- Acute treatment of bradycardia may involve the use of the drug atropine. Atropine increases your heart rate, just a one off dose to bring their heart rate up.
- Chronically long term, these patients are likely to need a Permanent Pacemaker (PPM).
What is a Permanent Pacemaker (PPM)?
- It is inserted in “skin-pocket” below the collar bone
- Leads from the pacemaker are passed into the heart and they sense the electrical activity within the heart.
- They are able to deliver small electrical impulses to the myocardial tissue if it detects inappropriate cardiac rhythm, hence a slow heart rate.
- Each patient has their own individual threshold for their pulse rate set within the pacemaker device itself and the pacemaker detects and monitors heart rate all the time. If the rate drops below the threshold, it will then stimulate a heartbeat.
What are the 2 types of tachycardia?
- Supraventricular arrhythmia
- Ventricular tachycardias
What is sinus tachycardia?
There’s an increase in heart rate but normal rhythm.
- This is a normal response to exercise
- Can be sign of an underlying problem such as an infection, drop in blood pressure, anaemia, thyrotoxicosis, hypovolaemia (loss of great volume blood), shock, PE (pulmonary embolism)
It is a side effect of a number of drugs, examples include:
- Nicotine
- B2-agonists
- Levothyroxine
- Salbutamol
- Aminophylline
What is atrial flutter?
- Occurs less frequently than atrial fibrillation but has similar underlying causes and is treated the same way as atrial fibrillation.
With atrial flutter you get a re-entry circuit within the right atrium (going round and round):
- You get a rapid atrial rhythm whether the heart is beating around 300 bpm.
- Ventricles usually beat once for every 2-4 atrial flutter waves
- You get stasis of blood (blood is not able to flow properly through the tissues) in atria hence need for anticoagulation.
What is Wolff-Parkinson White Syndrome?
- You get additional pathways which conduct an electrical pulse directly from the atria to the ventricles. Normally electrically activity passes through the AV node and the AV node has a major role in slowing down the electrical pulse as it enters the ventricles.
- As you get this by-pass of the AV node, you end up with a ventricular rate of up to 600bpm
- Extremely serious and life-threatening
What is ventricular tachycardias?
- Occasional palpitations from extra ventricular beats (“ectopics”) very common
- But the problem arises when these ectopics become frequent and you get runs of ectopic beats which is more serious.
Ventricular tachycardia is defined as when there are 5 or more ventricular beats occur consecutively.
Possible causes are:
- Acute myocardial infarction
- Ischeamic heart disease
- Cardiomyopathies (cardiac muscle dysfunction)
- Myocarditis (infection or inflammation of myocardium)
- Valvular disease
What is Torsade de pointes?
It is a type of ventricular tachycardia.
- It is due to QT prolongation which will be shown in the ECG. Hence the extension between the time between the Q wave and T wave.
- QT prolongation increases the risk of ventricular arrythmias occurring.
Underlying causes include:
- Congenital causes (hereditary causes)
- Electrolyte imbalances ; Hypokalaemia / Hypomagnesaemia
- Drugs
What is ventricular fibrillation?
Ventricular fibrillation is your classic cardiac arrest.
- You get rapid and unco-ordinated contraction of the ventricular tissues
- When your ventricles are beating very rapidly, it severely compromises cardiac output because your ventricles can not effectively blood on through
- Patients will lose consciousness within 10-20 secs going into cardiac arrest
- Medical emergency and without prompt treatment which is defibrillation or they will die.
- If there is survival there is a risk of irreversible cerebral myocardial damage.
What is direct current cardio version (DCCV)?
- It is used mainly for atrial fibrillation and atrial flutter.
- The term “Cardioversion” means process of restoring hearts normal rhythm.
- The process of cardioversion can be done chemically so by drugs or can be done by the process of DC (direct current) cardio version which is the application of controlled electric shock across the chest wall.
The aim of DCCV is to:
- Override any underlying disordered conduction
- Allow the SA node to regain control of heart rate
- Unpleasant process and the patient is briefly anaesthetised
- The process of DCCV has an increased risk of thromboembolism associated with the procedure itself. So if a patients is to undergo DCCV, they need to be anti coagulated for a minimum of 3 weeks before and at least 4 week afterwards.
What is radiofrequency ablation/cryoablation?
- The patient undergoes EP (electrophysiological) studies to identify the exact location within the myocardium where the arrhythmia is being generated from.
- Once the location is identified, a catheter with an electrode at the tip is guided to the appropriate point.
- Either radio frequency energy or freezing destroys the tissue in the myocardium where the arrhythmia is being generated from and distrupts/destroys the conduction pathway
- Prevents the need for long term drug therapy
What is defibrillation?
The delivery of electric shock to the myocardium via the chest wall.
- This is when the patient goes into cardiac arrest and ideally need to be given ASAP
- Used in conjunction with CPR. CPR is there to maintain cardiac output, maintain life and reduce cerebral damage.
