CR: PBL 1 (ECG and Atrial Fibrillation) Flashcards
Define cardioversion
Use of electric shock to convert dangerous, rapid fluttering of heart beat to its normal rhythm
Define atrial fibrillation
Irregularity of heart beat caused by involuntary contractions of small areas of heart muscle walls
Describe the ECG of someone in atrial fibrillation
No P wave, no identifiable PR interval, normal QRS complex
What are heart palpitations?
Sensation where a person is aware of an irregular, hard or rapid heart beat
What is cardiovascular disease?
Any disease of the heart or blood vessels e.g. Atherosclerosis, CHD and peripheral vascular disease
What is systolic blood pressure?
Blood pressure during contraction of the ventricles
What is diastolic blood pressure?
Minimum level of blood pressure measured between heart contractions
What is rivaroxaban?
An oral anticoagulant
What does a P wave represent?
Atrial depolarisation
What does a QRS complex represent?
Ventricular depolarisation
What does a T wave represent?
Ventricular repolarisation
What does the PR interval represent?
Activation of AVN, bundle of His and Purkinje fibres
How can you calculate ventricular rate from ECG?
Duration between R waves (RR interval)
How can you calculate atrial rate from an ECG?
Duration between P waves (PP interval)
How do atrial and ventricular rates differ in atrial fibrillation?
Atrial rate >360bpm whereas ventricular rate 60-150bpm
Why are blood tests used in the diagnosis of atrial fibrillation?
To check for factors which may have led to AF such as hyperthyroidism or electrolyte imbalance
How can hyperthyroidism lead to greater risk of atrial fibrillation?
Thyroid hormone contributes to arrhythmogenic activity by altering electro physiological characteristics of atrial myocytes by shortening the duration of atrial depolarisation
How can blood tests diagnosis cardiac failure?
Pro-brain natriuretic peptide is released in higher than normal levels (PNP)
Where is the SAN located?
Lateral to the junction where the superior vena cava enters the atrium
What is the function of the AVN?
Initiate wave of excitation in the ventricles following atrial contraction as the septum blocks the AVN impulse from being transmitted directly to ventricles
Define ‘automaticity’
Ability to depolarise spontaneously
What percentage of ventricular filling is done by atrial contraction at rest and during exercise?
Rest = 10% Exercise = 40%
Why would atrial fibrillation limit exercise capacity?
Because atrial systole effectively doesn’t occur and therefore there is poor ventricular filling leading to poor stroke volume which is insufficient to supply the active muscles and therefore this will lead to quick fatigue and lactic acid build up (cramp)
Why are patients with atrial fibrillation placed on anticoagulants?
AF increases chance of stroke due to slow blood flow (pooling) which increases the likelihood of clots forming and therefore anti coagulants are used to prevent clot formation and reduce stroke likelihood, or may be used prior to cardioversion (also increases risk of stroke)
