Arrhythmias Flashcards
What is sinus rhythm?
Any cardiac rhythm where depolarisation of the cardiac muscle behind at the sinus node
How is sinus rhythm characterised?
By the presence of correctly orientated P-waves on ECG
What is sinus arrest?
When the SA node transiently ceases to generate the electrical impulses responsible for cardiac contraction
What is heart block?
Abnormal heart rhythm here the heart beats too slow (bradycardia)
What is first degree AV block?
Simple prolongation of PR-interval >.22 seconds
What is Morbitz I type second degree heart block?
Wenckeback block phenomenon
Progressive PR-interval block until P-wave fails to conduct
What is Mobitz II type second degree heart block?
When a dropped QRS-complex is not proceeded by an increased PR-interval progression
What is a common feature of Mobitz type II second degree heart block?
Broad QRS-complex
What is 2:1 advanced block?
Occurs when every two or three P-waves conducts and precedes a QRS-complex
What is third degree heart block?
Complete heart block occurs when all atrial activity fails to conduct to the ventricles
What is atrial flutter?
Organised atrial rhythm with an atrial rate of approx 250-350bpm showing ECG sawtooth pattern
What proportion of the population have atrial fibrillation?
1-2% of adults (5-10% in elderly)
What are the causes of atrial fibrillation ?
Any condition resulting in raised atrial pressure ,mass, fibrosis, inflammation or infiltration
What are the most common causes of a.fib?
Hypertension and heart failure
What are the signs and symptoms for atrial fibrillation?
30% incidental finding
Rapid palpitations
Dyspnoea
Chest pain
What are the indication for implantable cardiac defibrillators?
Life threatening arrhythmias cause death in the first year in up to 40% of cases - employed as a preventative measure
What is Wolff-Parkinson-White syndrome?
One of several pre-excitation disorders effecting the electrical system of the heart
Wolff-Parkinson-White syndrome is caused by the presence of what?
An accessory conduction pathway between the atria and ventricles
Describe the electrical impulse process in Wolff-Parkinson-White syndrome?
Electrical signals travel down bundle of Kent and stimulate ventricles to contract prematurely resulting in a unique type of supraventricular tachycardia
What is the special type of tachycardia caused by Wolff-Parkinson-White syndrome?
Atrioventricular Re-entrant Tachycardia
What is the ECG telltale sign for Wolff-Parkinson-White Syndrome?
Delta waves
What is sustained ventricular tachycardia?
> 30s
What is the presentation of ventricular tachycardia?
Pre-syncope, hypotension and cardiac arrest
What is the typical pulse rate of someone experiencing ventricular tachycardia?
120-220bpm
What is the typical ECG pattern shown with ventricular tachycardia?
Torsades des pointes
What is ventricular fibrillation?
Very regular and irregular ventricular contraction with no mechanical effect
What is the clinical presentation of ventricular fibrillation?
Patient is pulseless, no respiration and rapidly unconscious
What is ventricular fibrillation usually preceeded by?
Ectopic beats
What are ectopic beats?
Random extra cardiac contractions
What does the ECG of atrial ectopic beats looks like?
Early and abnormal P-waves but usually not proceeded by a QRS-complex
What can be said about the need to treat atrial ectopic beats?
Not needed unless it precipitates a more serious arrhythmia
What classification for anti-arrhythmic drugs do we use?
Vaughan-Williams system
What do class I anti-arrhythmic drugs do?
Membrane depressants that reduce the rate of sodium entry into the myocyte
What subclasses of class I anti-arrhythmic drugs are there?
Class Ia - lengthen action potential
Class Ib -Delay action potential recovery
Class Ic - Stops spontaneous contraction
What do class II anti-arrhythmic drugs do?
Anti sympathetic drugs
What do class III anti-arrhythmic drugs do?
Prolong refraction period and increase action potential duration
What are class IV anti-arrhythmic drugs?
CCBs
What are some examples of anti-arrhythmic drugs with no classification?
Digoxin
Amiodarone
Adenosine
Atropine
How is the level of coagulation in vivo measured?
International normalised ratio
How is INR measured?
Actual thromboplastin time/ Standard thromboplastin time
What is the normal value of INR?
1
What is the therapeutic range of INR?
2.5-4
What risk factors must be considered incase of bleeding when on warfarin?
C - congestive heart failure H - hypertension A - aged >75 years old D - diabetes S - stroke (or TIA)
What electrotherapy is used to treat arrhythmias?
Radio frequency ablation
What arrhythmias can be readily ablated?
AVNRT Normal heart VT Atrial flutter Atrial tachycardia Atrial fibrillation
What is the problem with digoxin?
Is not actively removed from the kidneys therefore must be administered with digibind to avoid toxicity
What are the signs of digoxin toxicity?
Xanthopsia and reverse tick appearance of ST segment in lateral leads
What drug is used to treat Mobitz Type I heart block?
Atropine
What anti-arrhythmic drug interacts with digoxin?
Amiodarone
