Symposium 2 - Sudden cardiac death

Question 1

List 3 features of a death that can be defined as sudden death

Answer 1

• Natural
• Rapid (either < 1 hour or < 24 hours)
• Unexpected

Question 2

List four causes of sudden death

Answer 2

–Heart and/or its vessels

–Noncardiac vessels (e.g. stroke or aneurysm)

–Pulmonary system (pulmonary embolism)

–Central nervous system (CNS) (rare seizures in epilepsy)

Question 3

What is cardiac arrest?

Answer 3

•Definition: a sudden stop in effective blood circulation due to the failure of the heart to contract effectively or at all

•

•NOT the same as a acute myocardial infarct

–Although it can result from AMI sometimes

–AMI = when blood flow to some heart muscle is impaired

•Usually during AMI heart continues pumping, but less effectively

•

•NOT the same as heart failure

–HF = when the circulation is substandard, but the heart is still pumping sufficient blood to sustain life

Question 4

List three broad categories of arrhythmia causes or risks for arrhythmia?

Answer 4

• Electrical / primary
• Structural
• Iscahemic

Question 5

List three broad categories of primary arrhythmia?

Answer 5

Channelopathies & ion channel pathologies

Accessory conduction pathways

Unstable myocardium

Question 6

What is a cardiomyopathy?

Answer 6

• “myocardial disorder in which the heart muscle is structurally abnormal and functions abnormally”
• Pathology when heart size, shape or thickness is abnormal *E
• This excludes heart disease due to coronary artery disease, hypertension, abnormalities of the heart valves, and heart disease present at the time of birth

Question 7

List four subclasses of cardiomyopathy.

Answer 7

Hypertrophic

Dilated

ARVC - Arrhythmogenic Right Ventricular Cardiomyopathy

Question 8

Name the most common cyanotic developmental heart defect

Answer 8

Tetralogy of Fallot

Question 9

List two clinical consequences of Tetralogy of Fallot for the patient.

Answer 9

–Cyanosis, hypoxaemia, low blood O2 sats

–Risk of arrhythmia

–ventricular septal defect

•A hole between the ventricles

–Pulmonary valve stenosis

–Right ventricular hypertrophy

–overriding aorta

•aorta that is misplaced or moved

Question 10

Explain the concept of substrate vs trigger, and for each list an example?

Answer 10

•Trigger = brief event required to initiate a period of arrhythmia

–Extrasystole

–R on T

–

•Substrate = ongoing, underlying tissue instability that increases triggers OR allows for maintenance and amplification or dysrhythmia

–Electrical or structural defect eg fibrosis, inflammation, ischamia

Question 11

What is R on T?

Answer 11

Premature electrical activity in a cardiac myocyte

• On the ECG, when a premature QRS complex occurs during the previous T wave
• The T wave is a “vulnerable period”

–During repolarisation of ventricular AP

–Refractory period is ending

Question 12

What is a PVC (or VPB)?

Answer 12

• Premature ventricular contraction
• Ventricular premature beat
• An event on the ECG where a very and strangely shaped beat occurs in isolation

Question 13

In terms of activity, what would be the main difference between a pacemaker and an ICD?

Answer 13

• ICDs are triggered for only one beat, when the heart enters a pathological rhythms
• Pacemakers are triggered for every beat

Question 14

In terms of indication, what would be the main difference between a pacemaker and an ICD?

Answer 14

• ICDs are for pathologically fast rhythms
• Pacemakers are for pathologically slow or stopping rhythms

Question 15

List two drugs used as antiarrhythmic drugs?

Answer 15

• Beta blockers
• Amiodarone
• Calcium channel blockers
• K+ channel blockers
• There are many others, eg quinidine, mexilitene, adenosine

Question 16

What are the indications for implanting an ICD?

Answer 16

•cardiac arrest due to ventricular fibrillation

•

•symptomatic heart failure with low LVEF

–Low output heart failure after MI (40 days later)

•

•cardiomyopathies

–Eg Dilated cardiomyopathy

•

•congenital

–Eg Tetralogy of Fallot

•

•Channelopathies

–Eg long QT syndrome

Question 17

What is a supraventricular arrhythmia?

Answer 17

An arrhythmia whose source is not the ventricular myocardium. Examples are all atrial arrhythmias, arhythmias arising in the AV node or in the bundle of His

Question 18

What is reperfusion injury?

Answer 18

tissue damage caused when blood supply returns to the tissue after a period of ischemia or hypoxia.

Tissue damage and/or hypoxia lead to electrical irregularities & risk

Contexts *E

Myocardium after PCI

Brain tissue after ischaemic stroke

Cause: the restoration of circulation results in inflammation and oxidative damage

Question 19

List two broad causes of black outs?

Answer 19

Syncope

Seizures

Question 20

List two ways that you might attempt to differentiate syncope vs seizures.

Answer 20

Diagnostic tests such as EEG, brain scanning and 24 hour Holter monitoring

Patient history: Seizures tend to be associated with stiffness and unusual postures/ movements

Syncope patients “crumple”, seizure patients “tip over”

However, there are “convulsive syncope” which also features those

Question 21

In pharmacoeconomics, what is NNT?

Answer 21

Number needed to treat

Average number of patients who need to be treated to prevent one additional bad outcome

Question 22

What does this ECG show (or what disease is it)?

Answer 22

• Very high voltage (tall)QRS complexes (in V4 and V5)
• This shows a left ventricular hypertrophy, such as hypertrophic cardiomyopathy

Question 23

What does this CXR show?

Answer 23

• Cardiomegaly.
• The heart has hypertrophied

Question 24

What is arrhythmogenic re-entry?

Answer 24

• A conduction mechanism that leads to triggering arrhythmia
• The final outcome of re-entry is that there is a circle of conduction

–The circle results in a myocyte being restimulated out of sequence before the true stimulus from the SA node arrives

•Almost invariably, re-entry is caused by a local area of ischaemia that leads to a local delay of conduction and one-way conduction