week 6 Flashcards
The hearts conduction system:
Te conduction system of the heart consists of the sino-artrial (SA) node, the atrioventricular node, the bundle of HIS & right bundle of branches, then divides into the Purkinje fibres
How does the first impulse start?
POLARISED:
The cardiac cell normally has a high concentration of Potassium (K +) inside the cell, and a high concentration of Sodium (Na+) outside.
DEPOLARISED:
Na+ and K+ swap places (depolarise) this ‘sparks’ an electrical impulse.
Path of conduction.
The initial electrical impulse occurs in the S.A. node. The impulse spreads through the atria, they then contract. The impulse can only pass to the ventricles through the A.V. node.
Conduction to the ventricles:
Having reached the A.V. node the impulse travels down the bundle of His. The impulse then travels to the ventricles via the bundle branches to the Purkinje fibres. The ventricles then contract.
Repolarisation.
- the Sodium and Potassium must return to their normal concentrations inside and outside the cell.
- This causes an electrical impulse which can be seen on the ECG.
Limb leads and chest leads:
For example in lead II, the machine ‘looks up’ from the bottom left of the patient to the top right.
The E.C.G./ Rhythm strip:
Any impulse that travels TOWARD that lead will appear as an UPWARD (positive) deflection on the monitor / rhythm strip.
Any impulse that travels AWAY will appear as a DOWNWARD (negative) deflection.
This is seen most commonly as the impulse travels from the A.V. node down the bundle of His, an is the positive ‘r’ wave in the QRS
Myocardial Infarction (MI)
‘ 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…..
Assess 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
Treatment MI:
Thrombolysis
PCI (Percutaneous coronary intervention) Previously called Angioplasty
Thrombolysis :
The development of thrombolysis is the single most important advance in the care of coronary patients since defibrillation
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
