Week 6 Flashcards
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
Assessing chest pain
P – precipitating factors Q – quality R – radiation S – severity T – time of onset
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
Diagnosis of MI
Patient History Symptoms ECG Bloods: Troponin I/T Cardiac Enzymes
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
Treatment for MI
Thrombolysis - secondary treatment
PCI (Percutaneous coronary intervention) - primary treatment
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
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
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)
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
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)
Sinus arrhythmia
Irregular – can be “normal” usually not treated
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
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
Ventricular fibrillation
Basically just a quivering of the ventricles – no discernable cardiac output - Cardiac arrest – CPR required + defibrillation (+ drugs)
