Arrhythmias A simple guide to all things electrical

Bradycardias

What’s Normal

• Heart rate

Normal at rest 60 – 100 / min

Bradycardia < 60 / min

Tachycardia >100 / min

expected ‘normal’ at peak exercise (220 – age)

Normal Electrics

Normal Pattern

Normal 12 lead ECG

P atrial

contraction

QRS

ventricular

contraction

Why are the leads different

Spine

LA

LV

RV

RA

V1 V2 V3

V4

V5

V6

R Arm L Arm

L Leg R Leg

AVf / II / III

AVr

AVL / I

Bradycardias

• Heart rate < 60 / min

Pacemaker cells SA node 60> // AV node 40 > // ventricles 20-30 / min

First degree Block

P P P

R R R

PR interval – 200ms > (5 small squares >)

Second Degree Block

Mobitz Type 1

Wenkebach

PR P R P R P

//

PR

Second Degree Block

Mobitz Type 2

In this example transient 3:1 block

PR P R P P

//

PR

//

Third Degree Block

P P P P P

R R

AV Dissociation

R - R interval

P - P interval

AV dissociation occurs when the R-R interval > P-P interval

i.e. a faster escape rate exists – can be normal finding

Pacemaker Indications

Types of pacemaker

Paced

Sensed

Action

Rate

AAIR A A I R

VVIR V V I R

DDDR D V I/T R

Cardiac Re-synchronisation

Therapy (CRT)

Treatment options with ICD or CRT for people with heart

failure who have left ventricular dysfunction

(LVEF < 35%)

NYHA class

QRS interval I II III IV

<120

milliseconds

ICD if high risk of sudden cardiac death ICD and CRT

not clinically

indicated

120–149

milliseconds

without LBBB

ICD ICD ICD CRT-P

120–149

milliseconds

with LBBB

ICD CRT-D CRT-P or

CRT-D

CRT-P

≥150

milliseconds

with or without

LBBB

CRT-D CRT-D CRT-P or

CRT-D

CRT-P

CXR appearances

Developing technologies

Leadless

pacemaker Sub-cutaneous

defibrillator

ILR Implant

Arrhythmias A simple guide to all things electrical

Tachycardia

Tachycardias

• Heart rate >100 / min Supra-ventricular

tachycardia (SVT)

= narrow-complex

tachycardia

Ventricular

tachycardia (VT)

= usually broad

complex

How to read a rhythm strip

1. Is there any electrical activity?

2. What is the ventricular (QRS) rate?

3. Is the QRS rhythm regular or irregular?

4. Is the QRS width normal or broad?

5. Is atrial activity present? (If so - P waves? Other atrial activity?)

6. How is atrial activity related to ventricular activity?

Mechanisms

• Automaticity

• Re-entrant circuits

• Accessory pathways (nodal and free wall)

• Ionic channelopathies

Pro-arrhythmia

SCAR

Narrow Complex Tachycardia

AVNRT AVRT

Orthodromic Antidromic

Patient Assessment

Adverse Signs

Reduced conscious level / syncope

Hypotension (SBP <90mmHg)

Chest Pain

Heart Failure

History

Description – rate / character

Frequency

Precipitants

Associated features

History of CHD / structural heart abnormality

Family history of SCD

Narrow Complex Tachycardia

AVNRT

Narrow complex tachycardia

• Terminate arrhythmia

– Adenosine

• Think about mechanism

• Future prophylaxis

• Definitive cure

Wolff-Parkinson-White Syndrome

WPW – orthodromic

WPW – antidromic AVRT

WPW – pre-excited AF

Atrial flutter

• Typical Flutter Ablation

• Increasing numbers

• Success rates >90%

– 5% recurrence, 25% AF

• First line or early second line prophylaxis

Drugs to cardiovert – Beta-blockers, amiodarone

Rate control – above + Digoxin, Verapamil

Electrical cardioversion / Ablation therapies

Atrial Fibrillation

AF: Which treatment?

• Electrical cardioversion

• Chemical cardioversion

• Pill in pocket

• Digoxin

• Amiodarone

• Sotalol

• Diltiazem

• Verapamil

• Flecainide

• Beta-blockade

• DDDRP pacing

• His bundle ablation

• Pulmonary vein isolation

• Wide area circumferential ablation

Intermediate risk?

•Rate 100-150 beats min-1

•Breathlessness

Low risk?

•Rate < 100 beats min-1

•Mild or no symptoms

•Good perfusion

High risk?

•Rate > 150 beats min-1

•Chest pain

•Critical perfusion

YES

NO

Seek expert help

YES

Seek expert help

Immediate heparin and

synchronised DC shock 100J, 200J:360J

or equivalent biphasic energy

Amiodarone 300mg over 1

hour, may be repeated once if

necessary

Onset known to

be within 24 hours?NO YES

YES

YES

•Heparin

•Synchronised DC shock

100J, 200J, 360J or biphasic equivalentInitial rate control:

•Amiodarone 300mg over 1hour,

may be repeated once if necessary

AND Anticoagulation:

•Heparin

•Warfarin

•Later synchronised DC shock if indicated

Anticoagulate with:

•Heparin

•Warfarin

For later synchronised

DC shock if indicated

•Heparin

•Amiodarone: 300mg over 1 hr

•repeated once if necessary

OR

•Flecainide 100-150 mg

i.v. over 30 mins

and/or DC shock if indicated

Rate control with:

•Beta blockers, or

•Verapamil, or

•Diltiazem, or

•Digoxin, or

Anticoagulate with:

•Heparin

•Warfarin, then

Later DC shock

if indicated

Poor perfusion

and/or known structural heart disease?

Onset known to be within 24 hours?

Amiodarone 300mg over 1hour,

may be repeated once if necessary

NO

Onset known to be within 24 hours?

Attempt cardioversion

•Heparin

•Flecainide 100-150 mg i.v., or

•Amiodarone 300 mg i.v. over 1 h

Synchronised DC shock

if indicated

NO

YES

YES

Intermediate risk?

•Rate 100-150 beats min-1

•Breathlessness

Low risk?

•Rate < 100 beats min-1

•Mild or no symptoms

•Good perfusion

High risk?

•Rate > 150 beats min-1

•Chest pain

•Critical perfusion

YES

NO

Seek expert help

YES

Seek expert help

Immediate heparin and

synchronised DC shock 100J, 200J:360J

or equivalent biphasic energy

Amiodarone 300mg over 1

hour, may be repeated once if

necessary

Onset known to

be within 24 hours?NO YES

YES

YES

•Heparin

•Synchronised DC shock

100J, 200J, 360J or biphasic equivalentInitial rate control:

•Amiodarone 300mg over 1hour,

may be repeated once if necessary

AND Anticoagulation:

•Heparin

•Warfarin

•Later synchronised DC shock if indicated

Anticoagulate with:

•Heparin

•Warfarin

For later synchronised

DC shock if indicated

•Heparin

•Amiodarone: 300mg over 1 hr

•repeated once if necessary

OR

•Flecainide 100-150 mg

i.v. over 30 mins

and/or DC shock if indicated

Rate control with:

•Beta blockers, or

•Verapamil, or

•Diltiazem, or

•Digoxin, or

Anticoagulate with:

•Heparin

•Warfarin, then

Later DC shock

if indicated

Poor perfusion

and/or known structural heart disease?

Onset known to be within 24 hours?

Amiodarone 300mg over 1hour,

may be repeated once if necessary

NO

Onset known to be within 24 hours?

Attempt cardioversion

•Heparin

•Flecainide 100-150 mg i.v., or

•Amiodarone 300 mg i.v. over 1 h

Synchronised DC shock

if indicated

NO

YES

YES

Broad Complex Tachycardia

• ECG BCT

BCT - VT Discriminators

Ventricular Arrhythmias

Cardiac arrest is dangerous!

Total arrests

4888

Died before

admission

4173

Admitted

715

Discharged

303

WYMAS: 1987-1997

6%

Assessment Post Cardiac Arrest

• Cause of arrest apparent

(4H’s) Hypoxia / Hypovolaemia / Hyperkalaemia / Hypothermia

(4T’s) Toxins / Tension / Tamponade / Thrombo-embolic

• Has there been an acute ischaemic event ?

Troponins / ECG / Angiogram / MRI scarring pattern

• Any structural heart abnormaility ?

Echo / cardiac MRI / Signal averaged ECG / ETT

• Family history or genetic pattern to suggest inherited cardiac

condition (ICC) – Brugada (Ajmaline test) / Long & short QT’s / CPVT

SCD – Apical HCM

SCD - HCM

SCD - ARVD

Epsilon wave (most specific finding, seen in 30% of patients)

T wave inversions in V1-3 (85% of patients)

Prolonged S-wave upstroke of 55ms in V1-3 (95% of patients)

Localised QRS widening of 110ms in V1-3

Episodes of VT with LBBB morphology (i.e. right ventricular VT).

SCD – Long QT

• ECG polymorphic VT

SCD - Brugada

Antiarrhythmic Drugs

Arrhythmia Modifying Drugs

Radiofrequency Ablation

Resistive heating

Conductive heating

Ablation catheter

Indifferent electrode

Thermistor

Internal Cardiac Defibrillators

1) Survived a cardiac arrest caused by either VT or VF

2) Spontaneous sustained VT causing syncope or significant haemodynamic

compromise

3) Sustained VT without syncope or cardiac arrest, and also have LVEF <=35%

and symptoms are no worse than NHYA class III

4) Familial cardiac condition with a high risk of sudden death - long QT

syndrome, HCM, Brugada syndrome or ARVD or have undergone surgical repair

of congenital heart disease.

ICDs

ICD Therapies

Antitachycardia pacing

Defibrillation

Conclusion

• Arrhythmia management has changed

• Devices and ablation are growing

• Drugs (esp class I) are declining

• Significant challenges await us

– Cost effectiveness of ICDs

– Epidemic of atrial fibrillation