ECG and arrhythmias Flashcards
How many seconds is 1 small square, 1 large square and 5 large squares?
0.04 secs, 0.2 secs and 1 second respectively
A P wave is normally less than ? squares wide and less than ? squares tall
3 small and 2 small respectively
QT interval is meant to be ______ than RR interval
half or less
Leads for Inferior aspect of the heart
leads 2, 3, aVF
Leads for lateral aspect of the heart
Lead 1, avL and V5, V6
Leads for anterior aspect of heart?
V1, V2, V3
Leads for septal aspect of the heart?
V3, V4
To calculate the rate
look at Lead 2 on rhythm strip, count QRS and times by 6
Which leads are the transition leads? What is the significance of the transition wave moving to V5, V6?
Normally the transition wave is in leads V 3, 4. When the transition wave appears in V5, V6 it indicates right ventricle enlargement–> rotation in a clockwise direction. this is characteristic of Chronic Lung Disease
What does a Prolonged P-R interval indicate? What is normal for PR interval?
1st degree heart block. A normal PR interval is less than 5 small squares (so less than 0.2 seconds)
Where do the coronary arteries arise?
Aortic sinuses of Ascending Aorta. Right coronary artery from the right sinus, left from the left
What does the right coronary artery supply?
The right coronary artery supplies the right atrium and right ventricle, the sinu-atrial and atrioventricular nodes, the interatrial septum, a portion of the left atrium, the posteroinferior one third of the interventricular septum, and a portion of the posterior part of the left ventricle.
Usually SA node (but not always)
Right marginal branch–>
Posterior interventricular branch–>
What does the left coronary artery supply?
The distribution pattern of the left coronary artery enables it to supply most of the left atrium and left ventricle, and most of the interventricular septum, including the atrioventricular bundle and its branches.
Left anterior descending artery
left circumflex artery–> left marginal artery
What is the difference between Type 1 and Type 2 2nd degree heart block?
Type 1: Wenckebach= PR interval progressively gets longer and longer before there is a skipped QRS segment. Cycle starts again
Type 2: Mobitz= PR interval remains constant and sometimes the QRS segment is skipped.
2:1 and 3:1 is when there are 2 or 3 P waves per QRS segment consistently
What does global ST elevation indicate?
PERICARDITIS
QRS segments in ventricular problems?
WIDE QRS segment
Escape rhythms
Bradycardia–> 50bpm if SA node x; 30bpm if AV node x
slow and protective, if SA or AV node depolarisation is ineffective
Atrial flutter? What do we see on the ECG
Sawtooth waves lead 2 and 3. When p waves occur > 250/min
What does fibrillation mean? What does AF look like on an ECG? What about VF?
Fibrillation occurs when individual muscle fibres contract independently.
AF- no p waves, irregular lines. Some QRS segments. Small ‘f’ waves for fibrillation
VF- no QRS segments, disorganised ECG. patient falls unconsious. often fatal.
What does a peaked P wave indicate?
What do we see in LV hypertrophy?
Hypertrophy of right ventricle
QRS of greater than 25 mm in V5, V6 and inverted T waves in V5, V6, lead 2, lead avL
How can digoxin affect ECG?
Causes T wave inversion
Sequence of changes on ECG for STEMI/ myocardial infarction
Sites of infarction?
- raised ST segments
- Q waves appear
- normalised ST segments
- inverted T waves appear (irreversible)
Anterior- changes in V3, V4
Inferior- changes in 3 and aVF
Lateral- changes in V1, VL, V5, V6
What might we see in hyperkalemia?
Prolonged PR interval, peaked T waves, flat P waves
What are some causes of ST elevation?
Myocardial infarction, pericarditis, Prinzmetal angina (vasospasming of the coronary artery)
What might we see in hypokalemia?
peaked p waves, prolonged PR interval, ST depression, inverted T waves
what is the normal scaling for ECGs? what is the normal voltage scale?
25mm/sec; 10mm/mV
300/ what can give us the rhythm?
300/ no. of large squares
which leads do you see p waves the best
Lead 2 and V1
Normal QT interval?
440ms for men, 460ms for women
what are the 2 types of bradycardia?
sinus bradycardia or AV block (look for hidden p waves)