arrhythmias

Question 1

what basic algorithm can be used to look at a normal ECG?

Answer 1

RATE
each ECG strip = 10 seconds.
Count number QRS X 6 = HR per min.

RHYTHM

AXIS
AVL most positive left axis deviation, lead 3 most positive then right axis deviation

INTERVALS
PR = 120-200
QRS = up to 120ms, if tall consider LV hypertrophy
QTc = 400-440mms

ST/T WAVE CHANGES
look for elevation, depression or inversion

Question 2

what BPM denotes tachy and bradycardia?

Answer 2

Brady <60 bpm

tachy >100 bpm

Question 3

what is a delta wave?

Answer 3

wave in a PR interval

suggests wolf Parkinson white syndrome

Question 4

what is the difference between absolute and relative bradycardia?

Answer 4

absolute (< 40 bpm)

relative when the heart rate is inappropriately slow for the haemodynamic state of the patient.

Question 5

what pacemakers can cause bradycardia?

Answer 5

Sinus node

AV node

Question 6

what is sinus node dysfunction?

Answer 6

dysfunction of the pacemaker

can be sinus bradycardia, sick sinus syndrome (tachy-Brady), sinus arrest or part of vasovagal syncope.

not always symptomatic

Question 7

what are the causes of sinus bradycardia, and when is a pacemaker indicated?

Answer 7

sinus bradycardia may be due to medications as well. Hypothyroidism, hypothermia and sleep apnoea should be considered.

Less commonly sinus bradycardia can be the result of rheumatic fever, viral myocarditis, amyloidosis, haemochromatosis and pericarditis.

In patients with symptomatic sinus node disease a pacemaker is indicated.

Question 8

what is a first degree AV block?

Answer 8

Characterised by a PR interval > 0·2 seconds, no specific treatment is indicated.

For patients on digoxin, check for toxicity. Care with other rate limiting drugs. If there are symptoms of dizziness or syncope cardiac monitoring should be considered to identify higher degrees of block.

Question 9

what is a second degree AV block (Mobitz type 1?)

Answer 9

This is characterised by progressive lengthening of the PR interval, followed by failure of the atrial impulse to conduct to the ventricles = skip a QRS complex, then the process starts again.

It can occur in young fit patients with high vagal tone so can be seen during the night if monitored.

It can occur quite frequently following inferior MI and rarely proceeds to complete heart block.

No specific therapy is indicated. Higher degrees of AV block should be looked for if patients present with syncope or dizziness.

Question 10

what is a second degree AV block (mobitz type 2)?

Answer 10

Characterised by a constant PR interval followed by sudden failure of a P wave to be conducted to the ventricles, this is less common, but indicates more serious involvement of the conduction system.

each QRS has 2 p waves.

In the absence of a recent acute coronary event, permanent pacing should be arranged (if drugs have been excluded).

Question 11

what is a complete (third degree) AV block?

Answer 11

characterised by no conduction from the atria to the ventricles and therefore AV dissociation.

There is no relationship between the P waves and QRS complexes.

This block can occur above the AV node at the His region (narrow complex escape and usually well tolerated such as congenital complete heart block) or beneath the AV node with broad complex escape (not well tolerated).

In can also be intermittent therefore look for ECGs with trifascicular or bifascicular block (RBBB, left axis deviation with or without prolonged PR interval) and alternating LBBB and RBBB.

Question 12

what are the causes of a complete third degree AV block?

Answer 12

various anti-arrhythmic drugs but more notably digoxin toxicity.

can occur following inferior STEMI and in this context can resolve in hours to days.

It is a more ominous finding following anterior MI (infranodal).

Another important cause is severe hyperkalaemia (can be treated with IV calcium chloride - 10 ml of 10% solution over 3-5 minutes).

Question 13

how can a third degree AV block be managed?

Answer 13

severe hyperkalaemia (can be treated with IV calcium chloride - 10 ml of 10% solution over 3-5 minutes).

In the haemodynamically unstable patient, atropine can be administered (600 μg to a maximum of 3 mg). I

Isoprenaline administered at a rate of 5 μg/min can be tried.

Urgent permanent pacing is indicated, and should be considered within 24 hours, in all patients except those with a reasonable likelihood of recovery of conduction - such as in patients with a recent coronary event.

Question 14

what are the complications of AF?

Answer 14

cardioembolic stroke

cardiac instability

higher risk of death

haemodynamic instability due to tachyarrhythmia or bradyarrhythmia

congestive cardiac failure

Question 15

how is AF diagnosed and assessed?

Answer 15

Manual pulse checks for irregularity due to atrial fibrillation are recommended in the presence of symptoms of AF, including:

• breathlessness
• palpitations
• syncope/dizziness
• chest discomfort
• stroke/TIA

An ECG is indicated to confirm if an irregular pulse is due to AF. Try do same day to identify cause. You must consider obese patients and those with obstructive sleep apnoea in whom there is an increasing prevalence too.

Question 16

what is the natural history of AF?

Answer 16

initially manifests as brief paroxysms of increasing duration (paroxysmal), going on to persistent and permanent AF

Question 17

when is cardiac monitoring recommended?

Answer 17

if paroxysmal (intermittent) AF is suspected

short term monitoring with 24hr cardiac monitor is first line, however symptoms would have to be very frequent to capture arrhythmia

AliveCor app/cardiac monitor can show repeated snap shots of rhythm over time and increases diagnostic yield.

Suspicion remains high = also anticoagulate if AF was diagnosed or unexplained syncope.

Prolonged cardiac monitoring should be considered by referring to cardiology. May used Holter monitor or the implantable loop recorder.

Question 18

when should an echocardiography be considered?

Answer 18

1. Perform if suspected structural heart disease (on the basis of symptoms or examination finding of a murmur or signs of heart failure).
2. Where a rhythm control strategy (cardioversion) is being considered
3. Baseline echocardiogram required to inform long term management

don’t delay anticoagulation while waiting for an echo (if appropriate)

DOAC is also not contraindicated while awaiting echo, unless a specific mitral stenosis murmur is heard

Question 19

how is AF managed?

Answer 19

1. Anticoagulation to prevent stroke
2. Rate control
3. Rhythm control

Once the atrial fibrillation is documented proceed to use CHA2DS2VaSc score, which is recommended to quantify risk of stroke or systemic embolism

Question 20

what is a CHADVASC score?

Answer 20

The score is based on medical diagnoses and risk can only increase over time with acquisition of new medical conditions. The score estimate an adjusted stroke rate per year

Question 21

what do the scores in a CHADVASC scoring system suggest?

Answer 21

A score of 2 or more is associated with significant risk, where risk of embolic stroke is considered high enough to offer anticoagulation.

A score of 1 in men is considered intermediate risk, where anticoagulation should be considered, and a careful decision has to be made keeping in mind the bleeding risk.

A score of 0 indicates a truly low risk of stroke and anticoagulation is not offered.

A score of 1 in women (due to gender) and a score of 0 are considered low risk, with anticoagulation not advised.

Question 22

what risks are used in the CHADSVASC scoring system?

Answer 22

• CHF or LVEF <1 = 1
• Hypertension = 1
• age >75 =2
• diabetes = 1
• stroke/TIA/thromboembolism = 2
• vascular disease = 1
• age 65-74 =1
• female = 1

Question 23

how is bleeding risk assesed?

Answer 23

HAS-BLED is used to asses risk of major bleeding.

It estimates the rate of major bleeds per 100 patient years, which can be compared to the CHA2DS2VaSc estimated risk of stroke.

The score is not intended to withhold anticoagulation, but to inform discussions and enable identification and optimisation of reversible risk factors for bleeding, including:

1) Uncontrolled hypertension (SBP>160mmHg)
2) Poor INR control
3) Concurrent medication (aspirin, NSAIDs)

4) Harmful alcohol consumption (>14 units per week)
The score can go up and down if reversible factors are addressed.

Question 24

what clinical characteristics are used in the HAS-BLED scoring system?

Answer 24

• hypertension (SBP>160mmHg)
• abnormal liver function
• abnormal renal function
• stroke
• bleeding
• labile INRs
• elderly (age>65)
• drugs
• alcohol (>14 units a week)

Question 25

what is the mechanism of action of DOAC’s?

Answer 25

They inhibit factor Xa (apixiban, rivaroxaban and edoxaban) or direct thrombin inhibitor (dabigatran) to reduced thromboembolic events.

Question 26

why are DOAC’s considered better than warfarin for treatment of AF?

Answer 26

They do not require regular testing of levels compared to the INR monitoring of warfarin.

There are no restrictions on food or alcohol.

They are excreted by the kidney, so renal function is monitored yearly.

They have lower rates of bleeding to warfarin (brain and GI tract) and slightly better reduction in strokes.

Question 27

when is electric cardio version considered for rhythm control in AF?

Answer 27

urgent = electric cardioversion. Can also be elective.

can also rhythm control with medications

Cardioversion is not the same as defibrillation. Both use shocks to reset the heart. But defibrillation uses a stronger shock to stop very severe rhythms that can cause sudden death.

usually done for AF for SAN reset to normal sinus rhythm, patient under general anaesthetic

Question 28

how can rate control be done to treat AF?

Answer 28

slow the heart response to AF by slowing conduction at the Av node to reduce ventricular conduction and therefore heart rate.

if LVEF <40%

• beta blocker
• digoxin

if LVEF >40%

• diltiazem/verapamil
• beta blocker
• digoxin

can do combination therapy if required

target initial resting HR <110 bpm

Question 29

true or false: Most of the patients who present with paroxysmal supraventricular tachycardia have AVNRT (AV nodal re-entry tachycardia, 60% of SVT) or AVRT (Atrio-Ventricular re-entry tachycardia, 30% of SVT).

Answer 29

true

Most of the patients who present with paroxysmal supraventricular tachycardia have AVNRT (AV nodal re-entry tachycardia, 60% of SVT) or AVRT (Atrio-Ventricular re-entry tachycardia, 30% of SVT).

these arrhythmias depend on AV nodal conductn and therefore can be terminated by transiently blocking AV nodal conduction

Question 30

what is the first line treatment in patients with supraventricular tachycardia who are haemodynamically stable?

Answer 30

Vagal manoeuvres are the first-line treatment in haemodynamically stable patients.

Vagal manoeuvres, such as breath-holding and the Valsalva manoeuvre (i.e. having the patient bear down as though having a bowel movement or blowing hard into a syringe to move the plunger), all slow conduction in the AV node and can potentially interrupt the re-entrant circuit.

Question 31

what is a carotid massage?

Answer 31

Carotid massage is another vagal manoeuvre that can slow AV nodal conduction and help treat supra ventricular tachycardia.

Massage the carotid sinus for several seconds on the non-dominant cerebral hemisphere side. This manoeuvre is usually reserved for young patients.

Due to the risk of stroke from emboli, auscultate for bruits before attempting this manoeuvre.

Do not perform carotid massage on both sides simultaneously. Wait at least 10 seconds before trying the other side.

Question 32

when vagal manoveuvres fail at terminating SVT, what short term management can be done?

Answer 32

adenosine or calcium channel blockers. e.g. verapamil

Question 33

what is adenosine?

Answer 33

Adenosine is a short-acting drug that blocks AV node conduction; it terminates 90% of tachycardias due to AVNRT or AVRT.

Given as a rapid IV bolus followed by a saline flush, best administered via a three-way stopcock (6 mg stat followed by 12 mg if unsuccessful and then a further 12 mg if still unsuccessful), in the antecubital fossa followed by a long flush with 0·9% sodium chloride.

It has a very short half-life.

May produce chest discomfort (warn patient), transient hypotension and flushing.

Avoid in patients with significant reversible airways disease. The crash trolley should be next to the patient when administering this drug in the unlikely event of significant bradyarrhythmia or more rarely tachyarrhythmia.

Question 34

if vagal manoeuvres and short term therapies don’t work to treat tachycardia, what can be considered?

Answer 34

If the tachycardia continues despite successful induction of at least some degree of AV blockade, the rhythm is almost certainly atrial tachycardia or flutter; AVRT is excluded, and AVNRT is very unlikely

Question 35

what can be used in unstable patients with tachycardia?

Answer 35

Synchronised cardioversion following sedation starting at 150J can be used immediately in patients who are hypotensive, have pulmonary oedema, have chest pain with ischaemia, or are otherwise unstable.

Question 36

what is verapamil?

Answer 36

CCB
can be used for AV node blockage to treat tachycardia and arrythmias

contraindicated in patients already on β-blockers or in patients with known significant LV dysfunction.

If adenosine and verapamil are ineffective or contraindicated (particularly if the patient is symptomatic and hypotensive), electrical cardioversion under general anaesthetic or sedation should be performed.

Question 37

when should flecanide be avoided?

Answer 37

in patients with MI past or present

Question 38

what should be done for patients with frequent attacks of paroxysmal SVT or drug side effects?

Answer 38

All patients with frequent attacks or drug side effects should be referred to an electrophysiologist for consideration of an electrophysiology study with a view to RF ablation to provide a cure and remove the need for antiarrhythmics.

Many individuals with AVNRT respond to β-blockers, diltiazem or verapamil (although verapamil and digoxin must not be used for WPW / AVRT). Second line drugs to prevent SVT are flecainide, sotalol or amiodarone.

Question 39

when can ventricular tachycardia be seen, and how can it be treated?

Answer 39

Rapid broad complex tachycardia shortly after STEMI is nearly always VT.

In patients with sustained VT who are haemodynamically compromised cardioversion is indicated

Suppression can be achieved with β-blockers but care is needed if hypotensive or LV function is significantly impaired.

Amiodarone can be tried. An alternative is lidocaine