ECG Flashcards
P
Electrical sign that stimulate contraction of atria (atrial systole)
QRS
Electrical sign that stimulate contraction of ventricles (ventricular systole)
T
Electrical sign that signify relaxation of ventricles
Sinoatrial node
Atrial depolarisation
P wave
Atrioventricular node
Isoelectric after P wave
Bundle of His
Rapid conduction
Insulated
Bundle branches
Septal depolarisation
Q
Purkinje fibres
Ventricular depolarisation
R
Late ventricular repolarisation
S
Fully depolarised ventricles
Isoelectric ECG
Repolarisation
Ventricular repolarisation
T
Electrode placement
Lead I - right arm (-) to left arm (+)
Lead II - right arm (-) to left leg (+)
Lead III - left arm (-) to left leg (+)
12 lead ECG
Location Polarity Plane \+ve electrode -ve electrode View Artery
Sinus rhythm
Normal
Sinus bradycardia
Rate is slow
Sinus tachycardia
Rate is fast
Sinus arrhythmia
Rate is irregular
R-R interval varies with breathing cycle
Atrial fibrillation
Oscillating baseline - atria contracting asynchronously
Rhythm can be irregular and rate slow
Turbulent flow pattern increase clotting risk
Atria not essential for cardiac cycle
Atrial flutter
Sawtooth pattern in baseline (II, III, aVF)
Atrial to ventricular beats 2:1, 3:1 or higher
First degree heart block
Prolonged PR segment/interval caused by slower AV conduction
Regular rhythm
Most benign heart block but progressive disease of aging
Second degree heart block
Mobitz I
Gradual prolongation of PR until beat skipped
Most P waves followed by QRS but some not
Regularly irregular - caused by disease AV node
Also Wenckebach
Mobitz II
P wave regular but only some followed QRS
No P-R prolongation
Regularly irregular - successes to failures 2:1 or random
Can rapidly deteriorate into third degree heart block
Third degree heart block
P waves and QRS regular, but no relation
P wave may be hidden in bigger vectors
Non-sinus rhythm - back up pacemaker in action
Ventricular tachycardia
P waves hidden - dissociated atrial rhythm
Rate is regular and fast
High risk of deteriorating into fibrillation (cardiac arrest)
Shockable rhythm
Ventricular fibrillation
Heart rate irregular and 250bpm and above
Heart unable to generate output
Shockable rhythm
ST elevation
ST elevated >2mm above isoelectric
Caused by infarction (tissue death by hypoperfusion)
ST depression
ST depressed by >2mm
Caused by myocardial ischemia (coronary insufficiency)
