ECGs Flashcards
e-lecture
What complex do you look at for BBB and how does it change?
QRS.
It becomes greater than 3 small squares 0.12s
Causes of BBB?
Normal pericarditis myocarditis congestive hf congenital heart disease
Which of the ECG leads look at which side and chamber of the heart?
Right atrium = aVR
Right ventricle; V1, V2
(thats why in a rbbb, you see positive deflection in v1 qrs)
Left atrium = aVF
Left ventricle = V3-V6
(lbbb +ve deflection in v6)
So if there is a left sided issue look at the associated leads
What 3 characteristic signs would you see on ECG for RBBB? Why?
- R prime sign on V1 & V2
Due to slow right ventricular depolarisation resulting in a 2nd R wave (RSR) - T wave flattening / inversion
- sometimes left axis deviation
How do you calculate HR with ECG?
300 / No. of large squares between R waves (R-R interval).
Which wave produces a positive deflection in all leads except in aVR?
What does this wave represent?
P wave
What are the deflections seen in the QRS complex?
Q wave - negative deflection
R wave - positive
S wave - negative
page 186
Normal duration of the PR interval?
0.12-0.2s
How would you describe the rhythm of ECGs?
The time between successive R waves
What is a regularly irregular rhythm?
What is an irregularly irregular rhythm?
And examples of conditions?
RI - irregular rhythm but with clear pattern (heart blocks)
II - irregular rhythm no pattern (atrial fibrillation)
What causes LBBB?
Ischaemic heart disease Fibrosis of conduction pathways HTN Acute MI Aortic stenosis Cardio myopathies
LBBB can NEVER be considered normal/physiological
Changes are seen in the R wave in RBBB?
Where can changed be seen in for LBBB?
ST segment and T wave
For LBBB and RBBB, M patterns on seen on which leads?
V1 - RBBB
V6 - LBBB
What is the main change in 1st degree heart block?
PR interval fixed but prolonged
What are the 2 types of 2nd degree heart block?
Type 1 / Mobitz 1
Type 2 / Mobitz 2
What is the main change in 2nd degree heart block?
Mobitz 1 - PR interval gets progrressively longer after each p wave until no conduction at all then cycle repeats.
Mobitz 2 - Each P wave is not always followed by a QRS. ratios can be 2:1 or 3:1. PR interval fixed however.
3 Characteristics of 3rd degree heart block?
- No conduction through av junction. atria and ventricles conduct independent of each other
- P waves may merge with QRS if conduction happens together
- QRS abnormally shaped
Why is 3rd degree heart block dangerous?
Can cause asystole (cardiac arrest) due to reduced cardiac output
Common causes of the 3 heart blocks?
- Anterior and Inferior Myocardial infarctions (note infarction of diff parts of the heart will cause diff heart blocks)
- Drugs; B- blockers () Calcium channel blockers (Verapamil), Cardiac glycosides (Digoxin)
- Cardiomyopathies
- CHD
Which heart block tends to have infectious causes i.e. rheumatic fever and myocarditis?
type 1 / mobitz 1
Type 3 complete block
Causes of ST elevation?
What is relevant ST elevation
Impending infarction
Pericarditis
Early repolarisation - Normal in some young males
vasospastic angina
relevant if it exceeds;
1mm in a limb lead
2mm in precordial/chest leads
make sure to read electure too!
On an ECG if a pulse is regular and p waves are visible what is the rhythm?
Sinus rhythm
Which 2 leads to look at to calculate the axis? WHY?
Lead 1 and aVF as they are perpendicular to each other
In addition to a negative aVF, what other lead must be negative for a true left axis deviation?
Lead 2
ST depression in leads II, III and aVF is consistent with which condition?
inferior ischaemia
