8. Rhythm recognition Flashcards
ECG electrodes should be placed over BONE/ MUSCLE
bone - to minimise artefact
in normal sinus rhythm, depolarisation begins in a group of specialised pacemaker cells called the ___ ___ node, located where?
SA node
close to the entry of the SVC in the right atrium
what is the p wave?
wave of depolarisation spreading from the SA node through the atrial myocardium
transmission of electrical impulse to the ventricles
1) firstly there is slow conduction through the __ __ node
2) then rapid conduction fo the ventricular myocardium by specialised conducting tissue called ___ ___
3) the ____ ___ ___ carries these fibres from the AV node and then divides into right and left bundle branches in the respective right and left ventricles
1) AV
2) purkinje fibres
3) bundle of his
what does the QRS complex represent
depolarisation of ventricular myocardium (<0.12s)
between the P and QRS there is a small isoelectric segment which largely represents what?
the delay in transmission through the AV node
what does the T wave represent?
ventricular repolarisation
standard paper calibration in ECGs? how many squares in 1 second?
25mm/s
5 large squares in a second (25 small squares)
estimating HR from ECG?
count number of R waves in30 large squares (6s) and multiple by 10
how to tell where an ectopic beat has originated from?
narrow QRS (<0.12): atrial muscle or AV node
broad QRS: ventricular muscle or supraventricular with BBB
some ventricular ectopic beats may be accompanied by a P wave occurring shortly after the QRS complex - what causes this?
retrograde conduction form the ventricles to the atria
T/F: complete AV block is an escape rhythm
true - the cells generating the ventricular rhythm are acting as a pacemaker because no atrial impulses are transmitted to the ventricles
if the QRS complex is less than 3 small squares in width, where does the rhythm originate from?
above the bifurcation of the bundle of His - may be the SA node, atria or AV node (but not the ventricular myocardium)
what is the term for when ectopic beats occur alternately with sinus beats for a sustained period?
bigeminy
typical rate in atrial flutter?
about 300/ min (usually seen best in inferior leads)
sinus P waves are UPRIGHT/ INVERTED in leads II and aVF
upright (if inverted, suggests retrograde activate of the AV node ie junctional rhythm or ventricular in origin)
1) shockable
2) non-shockable
cardiac arrest rhythms?
1) VF, pVT
2) asystole, PEA
T/F: if the pt is conscious or has a pulse, the rhythm is not VF
true
what two rhythm abnomalities may be mistaken for VF?
polymorphic VT
pre-excited AF
T/F: there is often little variation in heart rate during a single episode of VT
true
what is a capture beat in VT?
atrial activity may continue independently of ventricular activity. Occasionally, these atrial beats may be conducted to the ventricles causing capture beats or fusion beats- a single normal looking QRS complex during monomorphic VT
what is a fusion beat in VT?
a wave of depolarisation travels down from the AV node simultaneously with a wave of deploarisation travelling up from the ventricular focus producing the arrhythmia- hybrid QRS caused by fusion of the normal and monomorphic QRS complex
in the presence of bundle branch block, an SVT will produce a NARROW/ BROAD complex tachycardia
broad
but the safest approach is to regard all broad complex tachycardias as VT until proven otherwise
torsades de pointes is a type of _____ VT, which usually arises in patients with a prolonged ___ ___
polymorphic
QT interval (inherited syndromes/ antiarrhythmic drugs/ MI)
