chapter 11 - peri-arrest arrhythmias Flashcards
what are some features of peri-arrest arrhythmias that are indicative of likely deterioration?
shock syncope heart failure myocardial ischaemia extremes of heart rate
why are extreme tachycardias bad?
reduce cardiac output as diastole is very short so the heart has very little time to fill, and reduces coronary blood flow as this occurs mostly during diastole, therefore leading to myocardial ischaemia
describe the adult tachycardia algorithm?
1) assess with abcde approach (give O2, obtain IV access, monitor with ECG, BP etc, identify and treat reversible causes)
2) life threatening features? (shock, syncope, MI, severe heart failure?)
3) if YES -> give synchronised DC shock up to 3 attempts (give sedation if conscious) -> if unsuccessful give amiodarone 300mg IV over 10-20 mins, repeat DC shock
4) if NO -> is the QRS narrow?
5) if QRS is BROAD -> regular or irregular?
5. 5) if irregular -> likely AF with BBB-> treat as narrow irregular OR likely tosades des pointes -> give IV Mg 2g over 10 mins
6) if regular -> if VT give amiodarone (300mg over 10-60mins), if previous certain Dx of SVT with BBB/abberant conduction -> treat as regular narrow complex tachycardia -> if ALL ineffective -> 3x DC shocks
7) if QRS is NARROW -> regular or irregular?
7. 5) if regular -> vagal manouveres -> if ineffective give adenosine 6mg IV bolus, if unsuccessful give 12mg, if unsuccessful give 18mg. -> if ineffective give verapamil or BB -> if ALL ineffective 3x DC shocks
8) if irregular -> probable AF -> control rate with BB, consider digoxin or amiodarone if evidence of HF, anticoagulant if duration >48h
what kind of DC is given in tachyarrhythmias?
synchronised DC -> synchronised shock to the R wave of the QRS (most defibrillators automatically do this)
what would happen if an unsynchronised shock is given in tachycardias?
the shock would likely coincide with the T wave and cause VF
how should you treat regular broad QRS tachycardias?
amiodarone 300mg IV 10-60 mins followed by 900mg maintenance in 24hrs
if it persists despite the initial 300mg then discuss with cardiology consultant on call as DC cardioversion may be needed but with expert advice
what is regular broad QRS tachycardia most likely to be?
VT or SVT - if unsure but definitely regular broad QRS tachycardia then treat as VT
what is irregular broad QRS tachycardia most likely to be?
AF with BBB or polymorphic VT (i.e. torsades)
how should you treat irregular broad QRS tachycardia?
if AF with BB -> treat as narrow irregular tachycardia i.e. rate control with BB, consider digoxin or amiodarone if evidence of HF, anticoagulant if more than 48hrs
if torsades -> stop all medications that prolong QT, correct electrolyte abnormalities, give Mg 2g IV 10 mins, + obtain expert help
what is regular narrow complex tachycardia most likely to be?
1) sinus tachycardia
2) paroxysmal SVT
3) atrial flutter with regular AV conduction (2:1)
Management of regular narrow complex tachycardia?
1) vasovagal manouveres
2) adenosine 6mg, if persists -> 12mg -> 18mg
3) if fails -> verapamil 2n5-5mg IV over 2 mins or BB such as metoprolol
4) if fails -> consider DC cardioversion
if adenosine + vasovagal movers fail then likely to be atrial source and to be AF/atrial flutter -> if recognised on monitor as AF/atrial flutter then treat
what is irregular narrow complex tachycardia most likely to be?
AF with rapid ventricular response (2:1)
Management of irregular narrow complex tachycardia?
rate control - BB
consider digoxin or amiodarone if evidence of HF
anticoagulant if >48hrs
rhythm control with DC cardioversion
what’s the criteria for DC cardioversion of patient who has been in AF for > 48hrs?
Should be anti coagulated for 3 weeks prior to DC cardioversion
IF needed urgently -> LMWH therapeutic dose to be given or heparin infusion
what can be used in management of irregular narrow complex tachycardia if BB contraindicated?
diltiazem
what drugs should be avoided in pre-excited AF?
adenosine diltiazem verapamil digoxin as they block the AV node and may increase the pre-excitation
what are the features of shock?
tachycardic hypotensive sweating pallor cold extremities reduced GCS
what are vasovagal manoeuvres?
carotid sinus massage
valsalva manœuvre
what is the MOA of adenosine?
Adenosine decreases heart rate and reduces conduction velocity, especially at the AV node, which can produce atrioventricular block.
what is adenosine used for?
chemical cardioversion in narrow complex regular tachycardias
what are the contraindications for adenosine ?
atrial fibrillation AF BBB heart transplant recent MI heart failure asthma
would should be said to the patient before you give adenosine?
warn the patient they will feel unwell and likely have chest pain
how should adenosine be given
through a large bore cannula into a large vein such as antecubital vein
what should you do if a patient has life threatening features and has narrow complex regular tachycardia?
attempt vasovagal manoeuvres whilst preparations are being made for DC cardioversion
when should rhythm control be considered in AF?
under 48h duration
what are rhythm controlling medications?
flecanide
What are the steps to deliver a synchronised DC shock?
1) ensure synchronised is selected
2) ensure correct voltage is selected:
broad complex tachycardia 120-150 J biphasic shock initially and then increase with each shock, for AF start with the maximum, for atrial flutter or narrow complex tachycardia start with lower 70-120J
3) ensure all staff members are away from bedside and oxygen is 1m away
4) deliver shock
where should the pads be positioned in DC shock in atrial fibrillation or atrial flutter?
anteroposterior position - right front and left back
what is the normal PR interval?
0.12-0.2ms i.e. 3-5 small squares
what is the definition of first degree heart block?
PR interval is > 0.2s/5 small squares
what is second degree heart block?
Second-degree AV block is present when some, but not all, P waves are conducted to the ventricles, resulting in absence of a QRS complex after some P waves. There are two types: mobitz type I and mobitz type II
what is mobitz type I?
The PR interval shows progressive prolongation after each successive P wave until a P wave occurs without a resulting QRS complex. (Whencebach) Often the cycle is then repeated.
The need for treatment is dictated by the effect of the arrhythmia on the patient and the risk of developing more severe AV block or asystole.
what is mobitz type II?
There is a constant PR interval in the conducted beats but some of the P waves are not conducted (i.e. followed by QRS complexes), in this case producing 2:1 AV block. This may occur randomly, without any consistent pattern. People with Mobitz II AV block have an increased risk of progression to complete AV block and asystole.
2:1 AV block describes the situation in which only alternate P waves are followed by a QRS complex. 2:1 AV block may be due to Mobitz I or Mobitz II AV block and it may be difficult to distinguish which it is from the ECG appearance. If bundle branch block is present (broad QRS complexes) as well as 2:1 block, this is likely to be Mobitz II block.
what is third degree heart block?
In third-degree (complete) AV block, there is no relationship between P waves and QRS complexes; atrial and ventricular depolarisation arises independently from separate ‘pacemakers’. The site of the ‘pacemaker’ stimulating the ventricles will determine the ventricular rate and QRS width.
A pacemaker site in the AV node or proximal bundle of His may have an intrinsic rate of 40-50 min-1 or sometimes higher and will have a narrow QRS complex unless additional bundle branch block is present.
A pacemaker site in the distal His-Purkinje fibres or ventricular myocardium will produce broad QRS complexes, often have a rate of 30-40 min-1 or less, and is more likely to stop abruptly, resulting in asystole.
what are agonal rhythms?
Agonal rhythm occurs in dying patients.
It is characterised by the presence of slow, irregular, wide ventricular complexes, often of varying morphology. These are unlikely to produce a pulse.
what is an escape rhythm?
If the normal cardiac pacemaker (SA node) fails, or operates abnormally slowly, cardiac depolarisation may be initiated from a ‘subsidiary’ pacemaker in atrial myocardium, AV node, conducting fibres or ventricular myocardium.
what is the adult bradycardia treatment algorithm?
1) Assess with AE approach
2) evidence of life threatening signs? (shock, syncope, MI, HF)
3) if YES-> give atropine 500mcg IV
3. 5) if good response then assess for risk of systole -> if no risk of asystole observe, if risk of systole then commence interim measures whilst getting expert help
3. 75) if no good response then commence interim measure: atropine 500mcg IV repeat to max 3mg, isoprenaline 5mcg IV, adrenaline 2-10mcg min IV OR transcutaneous pacing
4) if NO-> assess for risk of asystole and follow as above
what are the high risk factors of bradycardia following atropine that commence interim measure?
recent asystole
mobitz II AV block
complete heart block with broad QRS
ventricular pauses > 3s
what is percussion pacing?
To perform percussion pacing:
With the side of a closed fist deliver repeated firm thumps to the praecordium just lateral to the lower left sternal edge.
Raise the hand about 20 cm above the chest for each thump.
If initial thumps do not produce a QRS complex try using slightly harder thumps and try moving the point of contact around the praecordium until a site is found that produces repeated ventricular stimulation.
If attempted percussion pacing does not achieve a cardiac output within a few seconds, start CPR.
