Arrhythmias Flashcards
What is an arrhythmia?
An abnormal heart rhythm
What is a first degree heart block (ECG)?
When the PR interval is greater than 0.2s
What is a first degree heart block potentially a sign of?
CAD, digoxin toxicity or acute rheumatic carditis
What is a second degree heart block (ECG)?
Intermittent absence of QRS complexes
What, physiologically, is happening when there is a second degree heart block?
Indicates that there is a blockage between the AVN and the ventricles
What are the two types of second degree heart block?
Mobitz type 1 & 2
What is a mobitz type 2 arrhythmia?
Regular rhythm and fairly constant PR, but every now and again there is an absent QRS complex
What is a mobitz type 1 arrhythmia?
Progressive lengthening of PR interval followed by an absent QRS complex
What are the causes of a second degree heart block?
Acute MI, CHD
What is a third degree heard block (ECG)?
More P waves than QRS complexes - (90 waves and 36 QRS per min)
Variable PR intervals
No relationship between P and QRS
Regular rate
What, physiologically, is happening when there’s a third degree heart block?
No beats are conducted to the ventricles - however they are still excited by their own ectopic pacemaker system
What causes a third degree heart block?
MI, fibrosis around bundle of His, Always indicative of underlying disease (more often fibrosis than ischaemia)
Treatment of third degree heart block?
Pacemaker
What is a bundle branch block?
Normal PR interval but lengthened QRS complex
What, physiologically, is happening when there’s a bundle branch block?
Time take for depolarisation to spread through ventricles is altered - thus duration of QRS is increased
What happens in a right bundle branch block?
Right ventricle contracts after the left - creates a second R wave
What is a right bundle branch block?
There’s a distinctive pattern on ECG:
- V1 - M shaped QRS (AKA RSR pattern)
- V6 - W shaped QRS
- QRS complexes are also lengthened
What is a right bundle branch block caused by?
Atrial septal defect
What is a left bundle branch block?
Same as with a right bundle branch block however there is an M at V6 and a W at V1
What are the causes of a left bundle branch block?
Ischaemic disease (if chest pain present, MI is indicated - consider thrombolysis Aortic stenosis
What is a sinus rhythm?
The rhythm of the heart is being controlled by the SAN. There is one P wave per QRS and a constant PR interval
What is sinus tachycardia associated with?
Exercise, fear, pain, haemorrhage, thyrotoxicosis
What is sinus bradycardia associated with?
Athletic training, syncope, hypothermia, myxoedema, seen immediately after MI
What is supraventricular tachycardia?
Regular heartbeat however fast
Narrow QRS complexes
Inverted P waves are sometimes seen
What is physiologically happening in supraventricular tachycardia?
Heartbeat isn’t controlled by the AVN
Source of impulse is somewhere above the ventricles (hence supraventricular)
What is AF?
Irregularly irregular heart beat
Tachycardic
No P waves
What does supraventricular mean with regards to arrhythmias?
Arises above the AV node - anywhere above the ventricles - non-specific
What’s the order of conduction within the heart?
SA node -> AVN -> Bundle of His -> Left and right bundle branches -> Purkinje fibres
What is an ectopic beat?
Doesn’t originate in SAN
Can an ectopic beat be dangerous?
Yes, it depends on how it affects the cardiac output
Name 3 types of SVT
AF, Atrial flutter, Ectopic atrial tachycardia
Name 2 types of bradycardia
Sinus bradycardia and sinus pauses
What type of arrhythmia is wolf-parkinson-white syndrome?
AVN (accessory pathway)
Name 4 ventricular arrhythmias
Premature Ventricular Complex (PVC), VT, VFib, Asystole
Name 6 clinical causes of arrhytmias
Abnormal anatomy (L ventricular hypertrophy, congenital HD)
Autonomic (hyperthyroidism, heart block)
Metabolic (IHD, electrolyte imbalances, hypoxic myocardium)
Inflammation
Drugs
Genetic
If the QRS complex is wide, where is the problem?
The ventricles
What are the symptoms of AF?
Palpitations, dyspnoea and/or chest pain
What are the class I antiarrhythmic drugs?
Sodium channel blockers. Slow conduction.
Class Ia drugs lengthen the AP (quinidine, disopyramide).
Class Ib drugs shorten the AP (lidocaine)
Class Ic drugs do not affect the length on the AP (flecainide and propafenone)
Reserved for patients who do not have significant coronary arrtery disease, left ventricular dysfunctiokn or other forms of structural heart disease
AF is treated with quinidine
What are the class II antiarrhythmic drugs?
Prevent effects of catecholamines on the AP
Most are cardioselective beta blockers (metoprolol, bisoprolol, atenolol and acebutolol)
Use these in patients with symptomatic tachyarrhythmias, particularly in patients with coronary artery disease
What are the class III antiarrhythmic drugs?
Prolong AP - don’t affect sodium transport
Amiodarone and sotalol
What are the class IV antiarrhythmic drugs?
Non-dihydropyridine calcium channel blockers - verapimil and diltiazem - can prevent attacks of junctional tachycardia and may prevent other SVT (eg AF)
What are the unclassed antiarrhythmic drugs?
Adenosine and digoxin
