Lecture 19 - Heart 1 Flashcards
What does atrial excitation lead to?
Contraction
Define sinus rhythm
Regular HR driven by SAN with rate 60-100bpm
What should the R-R interval be between?
3-5 squares
What does the p wave represent?
Depolarisation of the atria
What does the QRS complex represent?
Depolarisation of the ventricles
What does the T-wave represent?
Depolarisation of the ventricles
Where is the pacemaker AP located?
In SAV and AVN
Where is the cardiac AP located?
In atrial and ventricular myocytes, bundles of His and in Purkinje fibres
Define abolsute or effective refractory period
When generation of the 2nd AP is not possible even at the strongest consecutive stimulus
Define relative refractory period
Generation of the 2nd AP is possible, but requires a stronger stimulus
Define Sick Sinus Syndrome
A group of heart rhythm disorders due to malfunction of the SA node that may present on the ECG as:
= Sinus pause
= Sinus arrest
= Bradycardia
What is the treatment of sick sinus syndrome?
Implantable transcutaneous pacemaker (TCP) - control and generate normal HR
What are the physiological causes of sinus bradycardia?
Increased vagal tone
Reduced HR
What are the extrinsic causes (non-cardiac) of sinus bradycardia?
Endocrine disorders
An electrolyte imbalance
Drugs - anti-arrhythmic and anti-hypertensive
Hypothermia
Define dysrhythmia
Abnormal rhythm
