ECG Flashcards
electrocardiogram
how many electrodes do you need to attach to obtain a 12-lead ECG?
10 (6 precordial and 4 limb)
where is V1 placed?
4th intercostal space, right sternal margin
where is V2 placed?
4th intercostal space, left sternal margin
where is V3 placed?
midway between V2 and V4
where is V4 placed?
5th intercostal space, mid-clavicular line
where is V5 placed?
5th intercostal sapce, anterior axillary line (at the same level as V4)
where is V6 placed?
5th intercostal space, mid-axillary line (at the same level as V4)
what colour limb lead goes on the right arm (RA)?
red
what colour limb lead goes of the left arm (LA)?
yellow
what colour limb lead goes on the left leg (LL)?
green
what colour limb lead goes on the right leg (RL)?
black
what is ventricular fibrillation (VF)?
irregular broad complex tachycardia. always a pulseless rhythm
what are the ECG features of VF?
QRS complexes are polymorphic and irregular
what is the management of VF?
emergency DC cardioversion (200 J biphasic unsynchronised shock)
what are the ECG features of ventricular tachycardia (VT)?
- tachycardia +
- absent P waves +
- monomorphic regular broad QRS complexes (>120ms)
what is the management of pulseless ventricular tachycardia (VT)?
emergency DC cardioversion (200 J biphasic unsynchronised shock)
what is the management of ventricular tachycardia with a pulse + adverse features?
adverse features = shock, syncope, MI, heart failure
synchronsed DC shock
what is the management of ventricular tachycardia with a pulse + no adverse features?
amiodarone
* 300mg IV over 20-60 mins
* then 900mg IV over 24 hours
what is torsades de pointes?
form of polymorphic ventricular tachycardia (PVT) caused by QT prolongation
need to have QT prolongation + PVT to be diagnosed
what are the ECG features of torsades de pointes (TdP)?
QRS complexes ‘twisting’ around the isoelectric line
what are the causes of torsades de pointes?
- congenital long QT syndromes
- medications
- MI
- renal/liver failure
- hypothyroidism
- AV block
- toxins
what is the management of torsades de pointes in haemodynamically unstable patients?
- emergency synchronised direct current shock
- IV amiodarone
what is the management of torsades de pointes in haemodynamically stable patients?
- IV magnesium sulphate (2g over 10mins)
list the differentials for a broad complex tachycardia
- ventricular fibrillation
- ventricular tachycardia
- polymorphic ventricular tachycardia
- torsades de pointes
what are the ECG findings in PE?
- normal or sinus tachycardia
- right-heart strain = right axis deviation and ST/T wave changes
- S1Q3T3 = deep S wave in lead I, Q waves in lead III nad inverted T waves in lead III
what is the pathophysiology of first degree heart block?
prolonged conduction of electrical activity through the AV node
what ECG finding is typical for first degree heart block?
PR interval >200ms
what are some of the causes of first degree heart block?
- high vagal tone (e.g. atheletes)
- acute inferior MI
- electrolyte abnormalities (e.g. hyperkalaemia)
- drugs - NHP-CCBs, beta-blockers, digoxin, cholinesterase inhibitors
what is the management of first degree heart block?
benign and does not need treating
what are the different types of second degree heart block?
- mobitz type I
- mobitz type II
what is mobitz type 1?
type of second degree heart block that is usually due to reversible conduction block at the AV node
what are the ECG characteristics of mobitz type I?
- irregular rhythem
- progressive PR-interval prolongation until a dropped QRS complex occurs
what are the causes of mobitz type I?
- MI (mainly inferior)
- drugs - beta/calcium channel blockers, digoxin
- professional athletes due to high vagal tone
- myocarditis
- cardiac surgery
what the management of mobitz type I?
generally asymptomatic and does not require any specific management
what is mobtiz type II?
type of second degree heart block where there are intermittent non-conducted P waves
what are the ECG characteristics of mobitz type II?
- PR interval is constant
- broad QRS complex indicating a distal block in the His-Purkinje system
- pre-exisiting left bundle branch block/bifascicular block
what are the causes of mobitz type II?
- infarction - particularly anterior MI
- surgery - mitral valve repair or septal ablation
- inflammatory/autoimmune - rheumatic heart disease, SLE, systemic sclerosis, myocarditis
- fibrosis - lenegre’s disease
- infiltration - sarcoidosis, haemochromatosis, amyloidosis
- mediacation - beta-blockers, calcium channel blockers, digoxin, amiodarone
what is the management of mobitz type II?
permanent pacemaker
what is complete/3rd degree heart block?
atrial impulses fail to be conducted to the ventricles
what are the clinical features of third degree heart block?
- syncope
- cardiac arrest
what are the ECG characteristics in third degree heart block?
- severe bradycardia
- dissociation between the P waves and the QRS complexes
what are the causes of third degree heart block?
- myocardial infarction (especially inferior)
- drugs acting at the AV node - beta-blockers, calcium channel blockers
- idiopathic fibrosis
what is the management of third degree heart block?
permanent pacemaker due to the risk of sudden death
what is bradycardia?
heart rate <60 bpm
what are the causes of acute bradycardia?
- sinus/AV nodal disease
- drug induced - beta-blockers, calcium channel blockers
- electrolyte abnormalities
- hypothyroidism
what are the clinical features of bradycardia?
- dizziness
- syncope
- tiredness
what is the medical management of acute bradycardia?
- treat any reversible causes
- atropine 500mcg IV - repeat boluses can be given up to 3mg
- no affect = alternative drugs (e.g. isoprenaline, adrenaline, aminophylline, dopamine)
how does atropine affect the heart?
blocks the vagus nerve activity on the heart, which increases the firing rate of the SA node
what are the factors which increase the risk of asystole in bradycardia?
- mobitz type II block
- complete heart block + broad QRS
- recent asystole
- ventricular pause >3 seconds
what is the management of acute bradycardia if medical management has failed?
transcutaneous pacing can be used whilst awaiting for transvenous pacing/permanent pacemaker insertion
