Flashcards in Arrhythmias Pathophysiology, Presentation and Investigation Deck (52)
What is sinus rhythm?
Sinus rhythm is a normal heart beat, with respect to both the heart rate and rhythm
Normal heart rate is between 60 and 100 beats per minute
What is atrioventricular block influenced by?
What are the features of first degree atrioventricular block?
AV conduction is delayed, so PR interval is prolonged (> 20 secs)
What are the features of second degree atrioventricular block?
Dropped beats occur because some impulses from the atria fail to conduct to the ventricles
What are the features of Mobitz type I second degree AV block?
Progressive lengthening of successive PR intervals culminating in a dropped beat
What are the features of Mobitz type II second degree AV block?
PR interval remains constant but some P waves are not conducted
What are the features of third degree (complete) atrioventricular block?
AV conduction fails completely resulting in the atria and ventricles beating independently
Ventricular activity is maintained by an escape rhythm arising in the AV node or Bundle of His (narrow QRS complexes) or the distal Purkinje tissues (broad QRS complexes)
What is the pulse and SV in third degree AV block?
Slow pulse, 25-50bpm, large volume, that does not vary with exercise
Increased stroke volume
What murmurs can be heart in third degree AV block?
Systolic flow murmurs
What is the management of second and third degree atrioventricular block?
Second degree or complete may respond to atropine or temporary pacemaker
What is the management of second degree or complete heart block which is complicating an acute MI?
Requires a temporary pacemaker
What is the management of atrioventricular block with systole?
IV atropine or isoprenaline to maintain circulation until pacemaker is inserted
What is the management of chronic atrioventricular block?
What is atrial flutter characterised by?
Large re-entry circuit within the right atrium, usually encircling the tricuspid annulus
What is the atrial rate in atrial flutter?
What is atrial flutter usually associated with?
When should atrial flutter be suspected?
Where there is a narrow complex tachycardia of 150/min
How might carotid sinus massage or IV adenosine help establish a diagnosis of atrial flutter?
By temporarily increasing the degree of AV block and revealing the flutter waves
What is the most common sustained cardiac arrhythmia?
What is atrial fibrillation characterised by?
The presence of multiple, interacting re-entry circuits looping around the atria
What are episodes of atrial fibrillation initiated by?
Salvoes of ectopic beats that can arise from conducting tissue in the pulmonary veins or from diseased atrial tissue
What is the pulse in atrial fibrillation?
What is the ECG like in atrial fibrillation?
Irregular QRS complexes with no P waves
What are the types of atrial fibrillation?
When is atrial fibrillation more likely to become sustained?
In enlarged atria with slow conduction
What is the presentation of atrial fibrillation?
May precipitate or aggravate cardiac failure
Light-headedness if hypotension
Chest pain if underlying coronary disease
Often asymptomatic and detected accidentally
What is the management of atrial fibrillation?
Full history and examination
12 lead ECG - document arrhythmia
Exercise tolerance test
Treat any underlying primary disorder e.g. if complicating an acute illness
CCBs for rate control
Anticoagulation if stroke/emboli risk
What is supraventricular tachycardia?
Supraventricular tachycardia is used to describe a range of regular tachycardias that have a similar appearance on an ECG
These tachycardias are usually associated with a narrow QRS complex and are characterised by a re-entry circuit or automatic focus involving the atria
What are the features of AV nodal re-entrant tachycardia?
Narrow QRS complex