Arrhythmias and Heart Failure Flashcards
What are the two basic causes of arrythmias?
Two basic causes of arrythmias:
* Malfunction of the conduction system (more common):
* Abnormal impulse generation (abnormal automaticity):
Which is the more common cause of arrythmias,
a.Malfunction of the conduction system
OR
b.Abnormal impulse generation
Malfunction of the conduction system is the most common cause of arrhythmias
What are the two types of the malfunction of the conduction system?
Two types of malfunction of the conduction system:
1. Re-entry: re-excitation around a conducting loop, which produces tachycardia
2. Heart block
What is an arrythmia?
An arrhythmia is an abnormal heart rhythm.
Abnormal eletrical activity of the heart.
What is tachycardia?
Tachycardia is a heart rate over 100 beats per minute at rest.
What is the ST segment clinically important for?
The ST segment is clinically important for ischaemia and myocardial infarction.
What can the T wave indicate?
The T wave could indicate high potassium levels.
What is a normal heart beat?
A normal heart beat is 60-100 beats per minute.
What is bradycardia?
Bradycardia is a heart rate less than 60 beats per minute at rest.
What are the 3 stages of a heart beat?
The 3 stages of a heart beat are:
1. Atrial depolarisation
2. Ventricular depolarisation
3. Atrial and ventricular repolarisation
What does the P wave represent?
P wave represents atrial depolarisation
What does the QRS complex represent?
The QRS complex represnts ventricular depolarisation
What does the T wave represent?
The T wave represents ventricular repolarisation.
The heart is ?% electrical cells and ?% muscle cells?
The heart is 1% electrical cells and 99% muscle cells?
Normal heart rate/rhythm starts and ends where?
Normal heart rate/rhythm starts and ends in the SA node.
What does the PR interval allow for?
The PR interval allows for the ventricles to fill up.
How long shouldn’t the P-R interval be?
The P-R interval shouldn’t begreater than 0.2 seconds it could indicate issues
The term used for the release (discharge) of an electrical stimulus is “?”, and the term for recharging is “?
The term used for the release (discharge) of an electrical stimulus is “depolarisation”, and the term for recharging is “repolarisation
The SA node ? whilst the atria are refilling, and the AV node recharges when the ventricles are ?
The SA node recharges whilst the atria are refilling, and the AV node recharges when the ventricles are refilling
Any part of the heart can do what?
Any part of the heart can excite.
What can malfunction of the conduction system be caused by?
Malfunction of the conduction system can be caused by:
* unidirectional conduction block
* establishment of new loop of excitation
* conduction that outlasts the refractory period
What is the refractory period?
The refractory period is a period of time during which a cell is incapable of repeating an action potential
Describe normal conduction
Normal conduction:
SA node to atria to AV node to apex to bundle of HIS to purkinje fibres
What are autorhythmic cells?
Authorhythmic cells:
* Specialised muscle cells
* Spontaneously generate action potentials
What are the two types of autorhythmic cells?
Two types of auto rhythmic cells:
* Pacemaker cells
* Conducting fibres
What does the pulmonary artery do?
The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs
What does ventricular depolarisation allow for?
Ventricular depolarisation allows for contraction.
What should the S-T segment b? What does it represent?
The S-T segment should be iso-electric
It represents the ventricles before repolarisation
The PR interval is the time from onset of ? activation to onset of ? activation
The PR interval is the time from onset of atrial activation to onset of ventricular activation
The QT interval is the duration of ? activation and recovery
The QT interval is the duration of ventricular activation and recovery
What should the QT interval not be?
The QT interval shouldn’t be too wide or too narrow.
What can more than one P wave for each QRS-T complex indicate?
More than one P wave for each QRS-T complex could indicate heart block
What is heart block? What may it result in?
Heart block:
* Partial damage to AV node may lead to intermittent heart block
* Resulting in more than one P wave for each QRS-T complex
What are extra-systoles?
Extra-systole= extra contraction
What is abnormal impulse generation?
Abnormal impulse generation (abnormal automaticity):
* Beat originates from a part it shouldn’t (should be from SA node)
* Ectopic beats may originate in atria or ventricle in the absence of any nodal damage and initiate extra-systoles
What might show on an ECG with atrial fibrillation?
Atrial fibrillation ECG:
* QRS complex may still be evident but superimposed on an irregular baseline
* No clear P wave
What can the heart do if it has issues?
If the heart has issues, it can generate a beat from any area.
Name the 4 types of arrhythmia
4 types of arrhythmia:
* Tachycardia: increased rate
* Bradycardia: decreased rate
* Fibrillation: disorganised contractile activity
* Flutter: very rapid but regular contractions
What can ventriular fibrillation lead to?
Ventricular fibrillation can lead to cardiac arrest or death.
Ectopic beat?
Ectopic beat: a part of the heart (not the SA node) generating a rhythm
What is fibrillation?
Fibrillation:
* The heart generates multiple etopic beats
* multiple ectopic foci develop and discharge asynchronously
* there is no coordination
Is atrial fibrillation or ventricular fibrillation more common?
Atrial fibrillation is more common than ventricular fibrillation.
Which drugs are available for arrhythmias?
Arrhythmia drug treatment:
* Class I: Sodium channel blockers (e.g. lignocaine)
* Class II: Beta blockers (e.g. propranolol)
* Class IIi: Drugs that delay repolarization/slow heart rate (Amiodarone)
* Class IV: Calcium channel blockers (e.g. verapamil and nifedipine)
* Class V: “Atypical” (e.g. adenosine, digoxin and anticoagulants).
Which symptoms are associated with arrythmia?
Symptoms associated with arrhythmia:
* Palpitations
* Dizziness
* Chest pain
* Dyspnea (breathing issues)
* Fainting
* Sudden cardiac death
If heart rate is low what is the PR interval likely to be?
If heart rate is low, the PR interval is likely to be longer.
If heart rate is high what is the RR interval likely to be?
If heart rate is high, the RR interval is likely to be closer.
Which sites can be involved in arrhythmia?
Sites involved in arrhythmia:
* Ventricular
* AV node
* Atrial
* Sinus
* Supraventricular (atrial myocardium or AV node)
What does a 3rd degree block have on an ECG?
On a ECG a 3rd degree block has many P waves
What does an elevated ST segment indicate?
An elevated ST segment may indicate acute myocardium damage from myocardial ischaemia
What does a depressed ST segment indicate?
A depresed ST segment may indicate myocardium damage and ischaemia.
What does an ECG do?
ECG:
Show heart behaviour
Accurate & detailed detection of cardiac abnormalities which may be related to myocardium damage or issues with conduction
What might a ventricular fibrillation ECG show?
Ventricular fibrillation ECG:
* Might not have any QRS-T waves (they won’t be completely flat)
What does a delay at the AV node lasting for more than 0.2s result in?
A delay at the AV node lasting for more than 0.2s leads to a heart block.
What is heart failure?
Heart failure:
- the heart’s inability to meet the metabolic requirements of the body
- heart could be pumping but not meeting metabolic demand/rate
- Disease of heart: associated with poor contracility of heart muscles, occurs when heart is unable to mainatin sufficient cardiac output to meet the demands of the body
Chronic heart failure
Chronic heart failure
* Gradual inability of the heart to maintain blood supply
Acute left ventricular failure
Acute left ventricular failure
Usually results from sudden inability of the heart to maintain blood
supply
Left-sided heart failure
Left-sided heart failure
* an inability of the left ventricle to pump out enough blood and as a result,
* * blood backs up into the lungs,
* causes pulmonary oedema
Right-sided heart failure
Right-sided heart failure
* Right ventricle fails to pump out enough blood,
* fluid backs up into the veins and capillaries
* causes systemic oedema particularly in the legs
Heart failure causes
Causes of heart failure
Coronary artery disease
Diseases of the heart muscle
Abnormal heart rhythms
Leaky heart valves
High Blood Pressure
Infections: viral or bacterial
Some chemotherapy drugs
Toxins such as alcohol
Birth defects- congenital heart disease
Heart failure treatments
Heart failure treatments
* Cardiac glycosides: e.g digoxin: inhibit na/K exchange, increase Na> decreased na/Ca exchange: increased Ca> increased contraction
* Angiotensin II blockers
* Beta-receptor agonists (Acute HD)
eg Dobutamine:Activate Beta 1-receptor in the heart and thus increase force of contraction
* Vasodilators: reduce afterload and peripheral vascular resistance
* Diuretics: fluid retention increases pre load.
* Diet
* Exercise
* Stop smoking
* Reduce alcohol intake
* Heart transplant
Why are selective beta1 antagonists used in heart failure?
Selective beta1 antagonists are used in heart failure:
* To not increase the afterload which will happen if peripheral alpha receptors are stimulated> cause blood vessel constriction
* Increased afterload will increase heart workload and impair cardiac output more
Angiotensin II mechanism of action
Angiotensin II mechanism of action
* Constrict Efferent arterioles
* Acts on CNS to increase ADH production Sympathetic tone
* Stimulate aldosterone secretion
* Na+ retention
* Increase fluid retention
* Vasoconstrict venous reservoir
* Increase blood volume
What does blocking angiotensin II do?
Blocking angiotensin II: reduces workload on the heart by preventing: aldosterone secretion, fluid retention and blood volume increase
