Electrocardiogram and Arrhythmias Flashcards
What waves are present on the normal ECG?
P wave
QRS complex
T wave
What does the P wave represent?
Atrial depolarisation
What does the QRS complex represent?
Ventricular depolarisation
What does the T wave represent?
Ventricular repolarisation
What does the PR interval represent?
Atrial to ventricular conduction
What is a normal PR interval?
120-200ms
What is the normal QRS length?
<120ms
What is the normal heart rate?
60-100
- bradycardic <60
- tachycardic >100
What is the cardiac cycle?
Systole + Diastole
Filling + contraction
Describe the electrical activity of the heart
Pacemaker SA node - down atria - AV node - bundle of His - purkinje fibres
Describe the mechanical activity of the heart
Relaxed chambers - atrial systole - isovolumic ventricular contraction - ventricular ejection - isovolumic ventricular relaxation - diastole
What is the EDV?
End-diastolic volume
-maximum amount of blood in ventricles
What is the ESV?
End-systolic volume
-minimum amount of blood in ventricles
What are the ECG changes in 1st degree heart block?
P-waves present
P-waves followed by QRS
Prolonged PR interval (reg)
What are the ECG changes in 2nd degree heart block? (Mobitz 1, Wenckebach)
P-waves present
P-waves not always followed by QRS
PR interval gradually lengthens until P wave dropped
What are the ECG changes in 2nd degree heart block? (Mobitz 2)
P-waves present
P-waves not always followed by QRS
PR interval constant, P wave not always conducted
What are the ECG changes in 3rd degree heart block?
P-waves present (unless AF)
No relation between P and R waves
What are indications for pacemaker implantation?
High degree heart block
Distal heart block
Presence of symptoms
Describe the ECG features of atrial fibrillation
Irregularly irregular rhythm
QRS <120ms
No P-waves
Chaotic ECG baseline
Describe the ECG features of atrial flutter
Regular rhythm QRS <120ms No P-waves Presence of flutter waves -300bpm -2:1
Describe the ECG features of re-entrant tachycardia
P-waves often hidden in QRS
Pseudo R-waves (V1)
Pseudo S-waves (II, III, aVF)
Describe the ECG features of ventricular tachycardia
Regular rhythm
QRS >120ms
P-waves may be present, no relationship w/ QRS
Describe the ECG features of ventricular fibrillation
Irregular rhythm
QRS >120ms
P-waves absent
Describe the ECG features of left ventricular hypertrophy
R-wave (V6) >25mm
Sum of S-wave (V1) and R-wave (V6) >35mm
Describe the ECG features of right ventricular hypertrophy
Dominant R-wave (V1)
T-wave inversion (V1-V4)
Deep S wave (V6, RAD)
Describe the ECG changes in LBBB
L-axis deviation Lead I +ve Lead II neutral/neg Lead III -ve WILLIAM
Describe the ECG changes in RBBB
R-axis deviation Lead I -ve Lead II neutral/pos Lead III +ve MARROW
Describe the initial ECG features of STEMI
Hyperacute T-waves
ST elevation <1hr
How does the ECG of a STEMI patient develop?
Development of pathological Q wave
Loss of R wave
ST elevation reduces
Inversion of T wave (late)
What ECG changes of a STEMI persist?
Abnormal Q waves
Reduced R waves
