ECG Made Easy - Chapter 4 - Abnormalities of P waves, QRS complexes and T waves

benryan95's version from 2015-09-15 20:01

Section 1

Question Answer
What is seen in right atrial hypertrophy?P wave becomes bigger
What is seen in left atrial hypertrophy?Broad and bifid P wave
How big is a normal R wave in a left ventricular lead?less than 25mm
How long is a normal QRS complex?120ms
What size are normal Q waves?less than 1mm across, less than 2mm deep
What can cause abnormally wide QRS complexes?Bundle Branch Block, depolarisation starting in ventricular muscle
What can cause an abnormally tall QRS complex?Increase in muscle mass of either ventricle
What is expected in Right Ventricular Hypertrophy?QRS complex in V1 (right ventricular leads) becomes upright, deep S wave in lead V6, right axis deviation, inversion of T waves in leads V1-V4 (perhaps peaked P wave due to right atrial hypertrophy)
What may a pulmonary embolus look like on ECG?Like a right ventricular hypertrophy (likely to just see sinus tachycardia)
What is expected in Left Ventricular Hypertrophy?Tall R waves in leads V5/V6, deep S wave in lead V1/V2, inverted T waves in leads I, VL, V5-V6, left axis deviation

Section 2

Question Answer
Which leads are normal to see Q waves in?V4-V6 (perhaps I and VL also?)
What does a large Q wave indicate?A myocardial infarction
How does the presence of a large Q wave help show where an infarction may have occurred?leads in which Q wave appear often look at where the infarction was/is
Where would you expect a large Q wave in an infarction of the anterior wall of LV?V2-V5 (leads looking from the front)
Where would you expect a large Q wave in infarction of both anterior and lateral surfaces of the heart?V3-V6, I, VL
Where would you expect a large Q wave in infarction of the inferior surface of the heart?III and VF
Does presence of a Q wave indicate the age of the infarction?no, once it is developed it is usually permanent

Section 3

Question Answer
Where is the ST segment?Between the end of QRS complex and the start of T wave
What baseline should the ST segment be at?Same as the TP segment
What does elevation of the ST segment indicate?Acute myocardial injury (pericarditis or recent infarction)
Where does ST elevation occur in anterior damage?V1-V6 leads
Where does ST elevation occur in inferior damage?III, VF
Where does ST elevation occur in pericarditis?Most leads
What does horizontal depression of the ST segment and upright T wave indicate?Ischaemia (not infarction - may appear during exercise)
What is the cause of downsloping ST segments, for example in a patient with atrial fibrillation?Due to digoxin treatment

Section 4

Question Answer
What can cause T wave inversion?Normality, Ischaemia, Ventricular Hypertrophy, Bundle Branch Block, Digoxin
What can leads adjacent to those showing inverted T waves sometimes show?Biphasic T waves, initially upright and then inverted
Which leads can the T wave be inverted in normality?VR and V1 (perhaps V2-V3)
What is the first abnormality seen after an MI?Elevation of the ST segment
How long can it take before ST segment returns to baseline after an MI?24-48 hours
What happens on an ECG if an infarction is not full thickness?T wave inversion, but no Q waves
In which leads does left ventricular hypertrophy cause T wave inversion?V5, V6, II and VL
In which leads does right ventricular hypertrophy cause inverted T waves?V2, V3 (inversion in V1 can be normal)
Which drug can cause T wave inversion?Digoxin

Section 5

Question Answer
Name 3 electrolytes which can affect the ECGPotassium, Calcium, Magnesium (not Sodium)
Where on the ECG do electrolytes alter?T wave and QT interval
What is the QT interval?From start of QRS complex to end of T wave
How long is the normal QT interval? (at 60bmp)350-440 milliseconds
What effect does low potassium have on ECG?T wave flattening, hump on end of T wave (U wave)
What effect does high potassium have on ECG?Peaked T waves, disappearance of ST segment (perhaps wide QRS complex)
What electrolyte has similar effects as potassium on ECG?Magnesium
What effect does low plasma calcium have on ECG?Prolongation of the QT interval
What effect does high plasma calcium have on ECG?Shortening of the QT interval

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