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Flashcards in Week 6 Deck (18):
1

Myocardial infarction

Myocardial infarction arises when a region of the myocardium becomes irreversibly necrosed. It is usually due to thromboembolic occlusion of the coronary artery supplying that area of heart muscle

2

Assessing chest pain

P – precipitating factors
Q – quality
R – radiation
S – severity
T – time of onset

3

Symptoms of MI

Pain:
Chest
Left arm
Right arm
Both arms
Neck
Jaw
back

Skin:
Pale
Sweaty
Clammy
cyanosed

Respiratory:
Tachypnoea
Dyspnoeic
Pulmonary oedema

Physical signs:
Nausea
Vomiting

Psychological:
Anxiety
confusion

4

Diagnosis of MI

Patient History
Symptoms
ECG
Bloods:
Troponin I/T
Cardiac Enzymes

5

MI observations/monitoring

Reassure patient – rest
Baseline observations
? Need for cardiac monitoring
12 lead ECG
IV access
Troponin (T & I) levels and cardiac enzymes (CK – creatine kinase)
Contact Dr

6

Treatment for MI

Thrombolysis - secondary treatment
PCI (Percutaneous coronary intervention) - primary treatment

7

Types of thrombolytic agents

Streptokinase: Most widely used, and cheapest. A bacterial protein. Patients develop antibodies, and can only be given once.

Recombinant tissue-type plasminogen activator (tPA):A naturally occurring human protease that is fibrin specific and this works predominantly on the clot, with less risk of systemic bleeding

Retaplase: A new generation, appears to be as effective as streptokinase. However can be given as a bolus and is non-antigenic

8

PCI

Invasive procedure
Access through femoral artery
Catheter inserted into coronary artery
Balloon inflated in CA to open stenosed area
Stenting carried out at same time if required
Risk of cardiac arrhythmias/cardiac arrest

9

Electrical system of the heart

The conduction system of the heart consists of the sinoatrial (SA) node, the atrio-ventricular node (AV) node, the bundle of HIS & the left & right Bundle branches then divide into the Purkinje fibres..
Pacemaker cells are situated all along the system but the SA node is usually the “pacemaker” due to it’s high rate of firing (60 -100 bpm) (the AV node 40-60bpm & bundles 30-40bpm)

10

ECG

P wave = SA node firing and atrial depolarisation
(contraction = atrial systole)
PR interval = impulse travel time
QRS complex = depolarisation from the AV node through the ventricles (contraction = ventricular systole)
ST segment = start of repolarisation
T wave = ventricular repolarisation
(refill = ventricular diastole)
QT interval = total time for ventricular
depolarisation & repolarisation
U wave = (if present) part of latter
phase of ventricular repolarisation

11

Basic analysis of a rhythm strip

Step 1 – Determine rhythm
Step 2 – Determine rate
Step 3 – Analyse the P waves for (almost) identical size, shape & position
Step 4 – Measure the PR interval (count the number of small squares – 0.04 secs each)
Step 5 – Measure the QRS complex (count the number of small squares – 0.04 secs each)

12

Sinus arrhythmia

Irregular – can be “normal” usually not treated

13

Atrial fibrillation

Uncoordinated atrial firing. Ventricular rate depends on AV node conduction. Many different types.
Causes – structural/valvular heart disease/age/many varied causes.
Treatment – amiodarone/calcium channel blocker/betablockers/cardioversion

14

Ventricular tachycardia

Rate over 100 bpm. Initiated by ventricle no atrial firing (no P wave) - Often following cardiac ischaemia. An emergency - may develop into ventricular fibrillation
Treatment – amiodarone/procainamide/cardioversion/pacemaker

15

Ventricular fibrillation

Basically just a quivering of the ventricles – no discernable cardiac output - Cardiac arrest – CPR required + defibrillation (+ drugs)

16

Asystole

Basically flat line, absent QRS complex – can have occasional P wave. No cardiac output, Death is imminent without treatment.
CPR required + adrenaline/atropine. Defibrillation useless.

17

Management of arrhythmias

Treat cause
Medication
Defibrillation/cardioversion - depending on the rhythm
Pacemaker
Cardiac conduction surgery

18

Complications of arrhythmias

Weakness/fatigue
Heart failure
Thromboembolic event - depending on the rhythm
Cardiac Arrest
Death