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