Arrhythmia Flashcards
(37 cards)
What do supra-ventricular arrhythmias include?
arrhythmia that arises above the AV node
- Afib
- atrial flutter
- ectopic atrial tachycardia
- sinus bradycardia/pauses
Where do ventricular arrhythmias arise from?
ventricular muscle or from the fascicles of the conducting system
- tachycardia
- fibrillation
- ventricular ectopics
- a-systole
What are the types of AV node arrhythmias?
- re-entry tachycardia
- extra connection to AV reentrant tachycardia
- AV block (first, second or third degree block).
What are the causes of arrhythmias?
- Abnormal anatomy- LVH, accessory pathways (extra connections between atria and ventricles) and congenital heart disease
- Autonomic nervous system- sympathetic stimulation (stress, exercise or hyperthyroidism), increased vagal tone (bradycardia)
- Metabolic- hypoxia (COPD or PE), ischaemic myocardium or electrolyte imbalances
- Drugs
- Inflammation
- Genetics- mutations of genes encoding cardiac ion channels
What are ectopic beats?
beats from somewhere other than the SA node, ectopic focus cause single beat or run of beats that are faster than sinus so take over e.g altered automaticity or triggered activity
What is re-entry?
additional circuit with more than one pathway with different speeds of conduction and refractory, triggered by ectopic beat
What does the danger of tachycardia depend on?
how it affects the cardiac output
What do things that affect the gradient and the threshold of action potentials affect?
automaticity
What does increasing phase 4 increase and cause?
increases HR and causes ectopics
What factors increase phase 4?
hyperthermia, hypoxia, hypercapnia, cardiac dilation and hypokalaemia
What factors decrease phase 4?
hypothermia and hyperkalaemia
What does decreasing phase 4 cause?
bradycardia
What phase is triggered activity in?
phase 3
What is triggered activity?
there are retriggers when the cells are usually inexcitable so there are more beats eg Digoxin toxicity
What is reentry due to?
- structural abnormality so scarring from MI, congenital HD, accessory pathways
- functional abnormality so self-perpetuating circuit due to differences in time for conduction
What are the causes of heart block?
age acute MI myocarditis amyloid drugs (beta blockers or calcium channel blockers), aortic valve disease genetic
What is 1st degree heart block?
P wave is longer than normal so PR interval is longer and there is no treatment
What is 2nd degree heart block?
intermittent block at the AVN so there are dropped beats
- Mobitz 1 (lengthening of PR and eventually a dropped beat)
- Mobitz 2 (pathological and every nth beat so a permanent pacemaker is needed)
What is 3rd degree heart block?
is normal P wave but ventricles are in asystole or have their own rhythm
What are the symptoms of arrhythmia?
palpitations, SOB, dizziness, syncope, presyncope, sudden cardiac death and angina
What does exercise ECG record?
ischaemia or exercise induced arrhythmia
What does ECG show in arrhythmia?
assess rhythm, signs of previous MI (Q waves) or pre-excitation (extra bridge of tissue), delta wave is where P wave is almost connected to the QRS so there is pre-excitation
What is normal sinus arrhythmia?
varying due to respiration reducing vagal tone and increasing heart rate
What is sinus bradycardia?
can be physiological, with drugs like beta-blockers, inferior STEMIs
