chapter 11 - peri-arrest arrhythmias

Question 1

what are some features of peri-arrest arrhythmias that are indicative of likely deterioration?

Answer 1

shock
syncope
heart failure
myocardial ischaemia 
extremes of heart rate

Question 2

why are extreme tachycardias bad?

Answer 2

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

Question 3

describe the adult tachycardia algorithm?

Answer 3

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

Question 4

what kind of DC is given in tachyarrhythmias?

Answer 4

synchronised DC -> synchronised shock to the R wave of the QRS (most defibrillators automatically do this)

Question 5

what would happen if an unsynchronised shock is given in tachycardias?

Answer 5

the shock would likely coincide with the T wave and cause VF

Question 6

how should you treat regular broad QRS tachycardias?

Answer 6

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

Question 7

what is regular broad QRS tachycardia most likely to be?

Answer 7

VT or SVT - if unsure but definitely regular broad QRS tachycardia then treat as VT

Question 8

what is irregular broad QRS tachycardia most likely to be?

Answer 8

AF with BBB or polymorphic VT (i.e. torsades)

Question 9

how should you treat irregular broad QRS tachycardia?

Answer 9

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

Question 10

what is regular narrow complex tachycardia most likely to be?

Answer 10

1) sinus tachycardia
2) paroxysmal SVT
3) atrial flutter with regular AV conduction (2:1)

Question 11

Management of regular narrow complex tachycardia?

Answer 11

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

Question 12

what is irregular narrow complex tachycardia most likely to be?

Answer 12

AF with rapid ventricular response (2:1)

Question 13

Management of irregular narrow complex tachycardia?

Answer 13

rate control - BB
consider digoxin or amiodarone if evidence of HF
anticoagulant if >48hrs
rhythm control with DC cardioversion

Question 14

what’s the criteria for DC cardioversion of patient who has been in AF for > 48hrs?

Answer 14

Should be anti coagulated for 3 weeks prior to DC cardioversion
IF needed urgently -> LMWH therapeutic dose to be given or heparin infusion

Question 15

what can be used in management of irregular narrow complex tachycardia if BB contraindicated?

Answer 15

diltiazem

Question 16

what drugs should be avoided in pre-excited AF?

Answer 16

adenosine 
diltiazem 
verapamil 
digoxin 
as they block the AV node and may increase the pre-excitation

Question 17

what are the features of shock?

Answer 17

tachycardic
hypotensive 
sweating
pallor
cold extremities
reduced GCS

Question 18

what are vasovagal manoeuvres?

Answer 18

carotid sinus massage

valsalva manœuvre

Question 19

what is the MOA of adenosine?

Answer 19

Adenosine decreases heart rate and reduces conduction velocity, especially at the AV node, which can produce atrioventricular block.

Question 20

what is adenosine used for?

Answer 20

chemical cardioversion in narrow complex regular tachycardias

Question 21

what are the contraindications for adenosine ?

Answer 21

atrial fibrillation
AF
BBB
heart transplant
recent MI
heart failure
asthma

Question 22

would should be said to the patient before you give adenosine?

Answer 22

warn the patient they will feel unwell and likely have chest pain

Question 23

how should adenosine be given

Answer 23

through a large bore cannula into a large vein such as antecubital vein

Question 24

what should you do if a patient has life threatening features and has narrow complex regular tachycardia?

Answer 24

attempt vasovagal manoeuvres whilst preparations are being made for DC cardioversion

Question 25

when should rhythm control be considered in AF?

Answer 25

under 48h duration

Question 26

what are rhythm controlling medications?

Answer 26

flecanide

Question 27

What are the steps to deliver a synchronised DC shock?

Answer 27

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

Question 28

where should the pads be positioned in DC shock in atrial fibrillation or atrial flutter?

Answer 28

anteroposterior position - right front and left back

Question 29

what is the normal PR interval?

Answer 29

0.12-0.2ms i.e. 3-5 small squares

Question 30

what is the definition of first degree heart block?

Answer 30

PR interval is > 0.2s/5 small squares

Question 31

what is second degree heart block?

Answer 31

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

Question 32

what is mobitz type I?

Answer 32

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.

Question 33

what is mobitz type II?

Answer 33

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.

Question 34

what is third degree heart block?

Answer 34

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.

Question 35

what are agonal rhythms?

Answer 35

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.

Question 36

what is an escape rhythm?

Answer 36

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.

Question 37

what is the adult bradycardia treatment algorithm?

Answer 37

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

Question 38

what are the high risk factors of bradycardia following atropine that commence interim measure?

Answer 38

recent asystole mobitz II AV block complete heart block with broad QRS ventricular pauses > 3s

Question 39

what is percussion pacing?

Answer 39

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.