Week Seven - Case One Flashcards
what are arrhythmias
abnormal heart rhythms
what are the shockable cardiac arrest rhythms
ventricular tachycardia
ventricular fibrillation
what are the non shockable cardiac arrest rhythms
pulseless electrical activity (all electrical activity except VF/VT, including sinus rhythm without a pulse)
asystole (no significant electrical activity)
what does narrow complex tachycardia refer to
a fast heart rate with a QRS complex duration of less than 0.12 seconds
on a normal 25mm/sec ECG, 0.12 seconds equals how many small squares?
3 small squares
therefore the QRS complex will fit within 3 small squares in narrow complex tachycardia
what are the four main differentials of a narrow complex tachycardia
Sinus tachycardia (treatment focuses on the underlying cause)
Supraventricular tachycardia (treated with vagal manoeuvres and adenosine)
Atrial fibrillation (treated with rate control or rhythm control)
Atrial flutter (treated with rate control or rhythm control, similar to atrial fibrillation)
what are patients with syncope, heart muscle ischaemia (chest pain), shock or severe heart failure treated with
synchronised DC cardioversion under sedation or general anaesthesia
what is added if initial DC shocks are unsuccessful
intravenous amiodarone
what does broad complex tachycardia refer to
a fast heart rate with a QRS. complex duration of more than 0.12 seconds or 3 small squares on a ECG
what are the broad complex tachycardias
Ventricular tachycardia or unclear cause (treated with IV amiodarone)
Polymorphic ventricular tachycardia, such as torsades de pointes (treated with IV magnesium)
Atrial fibrillation with bundle branch block (treated as AF)
Supraventricular tachycardia with bundle branch block (treated as SVT)
what is atrial fuller caused by
a re-entrant rhythm in either atrium
how does the electrical signal re-circulate in atrial flutter
in a self-perpetuating loop due to an extra electrical pathway in the atriaw
what is the usual atrial rate in atrial flutter
300 beats per minute
why does the signal not usually enter the ventricles on every lap
due to the long refractory period of the AV node
what does this result In, in terms of ratio of atrial and ventricular contractions
this often results in two atrial contractions for every one ventricular contraction (2:1 conduction), giving a ventricular rate of 150 beats per minute
there may be a 3:1 or a 4:1 variable conduction ratio
what is the appearance of atrial flutter on an ECG
sawtooth appearance on the ECG with repeated P wave occurring at around 300 per minute, with a narrow complex tachycardia
what is the treatment for atrial flutter
similar to AF, including anticoagulation based on the CHA2DS2-VASc score
radiofrequency ablation of the re-entrant rhythm can be a permanent solution
what is the QT interval
from the start of the QRS complex to the end of the. T wave
what does the QTc estimate the QT internal is if the heart rate was 60BPM
prolonged at:
More than 440 milliseconds in men
More than 460 milliseconds in women
what does a prolonged QT interval represent
represented prolonged repolarisation of the heart muscle cells (myocytes) after a contraction
what is depolarisation
the electrical process that leads to heart contraction
what is repolarisation
is a recovery period before the muscle cells are ready to depolarise again
what can waiting a long time for repolarisation result in
spontaneous depolarisation in some muscle cells
what are these abnormal spontaneous depolarisations before repolarisation known as
afterdepolarisations
what do these afterdepolarisations do
spread throughout the ventricles, causing a contraction before proper repolarisation.
when this leads to recurrent contractions without normal repolarisation, what is this called
torsades de pointes
what is tornadoes de pointes a type of
polymorphic ventricular tachycardia
what does torsades de pointes look like on an ECG
it looks like standard ventricular tachycardia but with the appearance that the QRS complex is twisting around the baseline. the height of the QRS complex gets progressively smaller, then larger, then smaller and so on
how does torsades de pointes terminate and what does the lead to
terminates spontaneously and will revert to sinus rhythm or progress to ventricular tachycardia
what can this ventricular tachycardia lead to
cardiac arrest
what are the causes of prolonged QT
Long QT syndrome (an inherited condition)
Medications,
Electrolyte imbalances, such as hypokalaemia, hypomagnesaemia and hypocalcaemia
what medications can cause a prolonged QT
such as antipsychotics, citalopram, flecainide, sotalol, amiodarone and macrolide antibiotics
what is the management of a prolonged QT internal include
stopping and avoiding medications that prolong the QT interval
correcting electrolyte disturbances
beta blockers
pacemakers or implantable cardioverter defibrillations
what beta blocker is not used in the management of a prolonged QT internal
sotalol
what is the acute management of torsades de pointes
correcting the underlying cause
magnesium infusion (even if they have a normal serum magnesium)
defibrillation if ventricular tachycardia occurs
what are ventricular ecoptics
premature ventricular beats caused by random electrical discharges outside the atria
how do ventricular ectopics appear on an ECG
as isolated, random, abnormal, broad QRS complexes on an otherwise normal ECG
what does bigeminy refer to
when every other beat is a ventricular ectopic.
what would the ECG show in bigeminy
a normal beat, followed immediately by an ectopic beat, then a normal beat, then an ectopic and so on
what is the management of bigeminy
Reassurance and no treatment in otherwise healthy people with infrequent ectopics
Seeking specialist advice in patients with underlying heart disease, frequent or concerning symptoms (e.g., chest pain or syncope), or a family history of heart disease or sudden death
what medication is sometimes used to manage symptoms of bigeminy
beta blockers
when does first degree heart block occur
where there is delayed conduction through the AV node.
what does first degree heart block look like on an ECG
despite the delated conduction, every atrial impulse leads to a ventricular contraction, meaning every P wave is followed by a QRS complex.
on an ECG , first degree heart block present as a PR interval greater than 0.2 seconds
what is second degree heart block
is where some atrial impulses do not make it through the AV node to the ventricles
what else are there instances of in second degree heart block
where P waves are not followed by QRS complexes.
what are the two types of second degree heart block
Mobitz type 1 (Wenckebach phenomenon)
Morbitz type 2
what is Mobitz type One
when the conduction through the AV node takes progressively longer until it finally fails, after which it resets and the cycle restarts
what is shown on an ECG in Mobitz type One
there is an increasing PR interval until a P wave is not followed by a QRS complex.
the PR interval then returns to normal, and the cycle repeats itself
what is Mobitz type 2
where there is intermittent failure of conduction through the AV node, with an absence of QRS complexes following P was vested
usually, what is there with Mobitz type two
usually a set ratio of P waves to QRS complexes
for example, three P waves for each QRS complex
the PR interval remains normal
what is there a risk of in Mobitz type two
asystole
what is a 2:1 block
is where there are two P waves for each QRS complex
every other P wave does not stimulate. a QRS complex.
what is third degree heart block also called
complete heart block
what sort of relationship between the P waves and QRS complexes is seen in third degree heart block
no observable relationship
what is there a significant risk of in third degree heart block
significant risk of asystole
what does bradycardia refer to
a slow heart rate, typically less than 60 beats per minute
what are the three main causes of bradycardia
medications
heart block
sick sinus syndrome
what medications can cause bradycardia
beta blockers
what does sick sinus syndrome encompass
many conditions that cause dysfunction in the SA node
what is sick sinus syndrome often caused by
idiopathic degenerative fibrosis of the SA node
what can sick sinus syndrome result in
sinus bradycardia, sinus arrhythmias, and prolonged pauses
what does asystole refer to
the absence of electrical activity in the heart - resulting in cardiac arrest
there is a risk of asystole in what conditions
Mobitz type 2
Third-degree heart block (complete heart block)
Previous asystole
Ventricular pauses longer than 3 seconds
what is the management of unstable patients and those at risk of asystole
Intravenous atropine (first line)
Inotropes (e.g., isoprenaline or adrenaline)
Temporary cardiac pacing
Permanent implantable pacemaker, when available
what are the two options for temporary cardiac pacing
Transcutaneous pacing, using pads on the patient’s chest
Transvenous pacing, using a catheter, fed through the venous system to stimulate the heart directly
what is atropine
an antimuscarinic medication