ECG and arrhythmias Flashcards by Olivia Ooi

How many seconds is 1 small square, 1 large square and 5 large squares?

0.04 secs, 0.2 secs and 1 second respectively

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A P wave is normally less than ? squares wide and less than ? squares tall

3 small and 2 small respectively

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QT interval is meant to be ______ than RR interval

half or less

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Leads for Inferior aspect of the heart

leads 2, 3, aVF

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Leads for lateral aspect of the heart

Lead 1, avL and V5, V6

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Leads for anterior aspect of heart?

V1, V2, V3

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Leads for septal aspect of the heart?

V3, V4

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To calculate the rate

look at Lead 2 on rhythm strip, count QRS and times by 6

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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

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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)

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Where do the coronary arteries arise?

Aortic sinuses of Ascending Aorta. Right coronary artery from the right sinus, left from the left

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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–>

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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

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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

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What does global ST elevation indicate?

PERICARDITIS

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QRS segments in ventricular problems?

WIDE QRS segment

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Escape rhythms

Bradycardia–> 50bpm if SA node x; 30bpm if AV node x

slow and protective, if SA or AV node depolarisation is ineffective

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Atrial flutter? What do we see on the ECG

Sawtooth waves lead 2 and 3. When p waves occur > 250/min

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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.

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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

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How can digoxin affect ECG?

Causes T wave inversion

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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

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What might we see in hyperkalemia?

Prolonged PR interval, peaked T waves, flat P waves

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What are some causes of ST elevation?

Myocardial infarction, pericarditis, Prinzmetal angina (vasospasming of the coronary artery)

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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)

ectopic beats? what are its other names?

extra beats, premature beats

escape beat?

beat comes in late

How long is the PR interval normally?

\<200 ms

What is the definition of sinus rhythm?

a p wave before every QRS segment, positive p waves in Leads 1,2,3 and inverted in AVF= sinus rhythm

What are Q waves? When do we think they are pathological on the ECG?

Q waves are negative deflections that can either be pathological or physiological. Pathological Q waves are when the Q wave is more than 1/3 the height or depth of the following R wave.

When do we see wide QRS segments?

VT, RBBB (if +ve in V1); LBBB (if -ve in V1)

What can a depressed PR interval mean?

A depressed PR interval= pericarditiis

What does the c stand for in QTc interval?

C stands for corrected QT interval for the RR interval. During physical exertion the RR interval decreases and hence the QT interval must also decrease.

how many leads do we put on a person for a 12 lead ECG?

Note that lead 1 goes to the middle of both legs, and lead 3 also goes to the middle of both legs. Hence we need TEN leads all up to do an ECG. 4 leads- one on each limb; and 6 leads V1-V6 on chest wall

what does p mitrale indicate?

LA hypertrophy Lead 2 Lead V6

what does p pulmonale indicate?

tall p wave= RA hypertrophy

what can cause far axis deviation?

What do we see on the ECG for RBBB?

MARROW pattern. V1- M; V6- W

what do we see on ECG for LBBB?

WILLIAM pattern; V1= W; V6=M

what is bigeminy?

normal beat ectopic normal beat ectopic pattern.

what controls the rate in AF?

AV node refractory period

what drugs can slow down the AV node?

digoxin, beta blocker, verapamil, diltiazam, amiodarone, sotalol

What can cause a wide QRS?

Ventricular beat; bundle branch block; pacemaker, altered pathway

junctional nodal escape rhythm

dissociation between QRS and P waves

what happens in BBB?

normal conduction to the unblocked side then slow cel; to cell conduction to the blocked side. The late wave represents the actvation of the ventricle going to the side of the blocked bundle

Where do you see the late waves in the RBBB and LBBB?

RBBB late wave is positive in V1 and negative in V6 LBBB late wave is negative in V1 and positive in V6

what does it mean when the AV node conduction slows?

increased refractory period of the AV node

what do you think when you see AF on the ECG and there is a regular rhythm of wide QRS segments?

AF with heart block. Wide QRS segments= ventricular escape rhythm

what leads do we see atrial flutter best?

Lead 2, 3, aVF

what causes Aflutter?

Re-entrant circuit around the tricuspid annulus. Intermittently hits the AV node and ventricular depolarisation occurs (irregular QRS). When the impulse goes up and down- this causes the sawtooth appearance on the ECG

AVR is normally...

negative

How can you tell RBBB?

lead 1 negative, lead 3 positive

How can you tell the LBBB?

**Lead 1 positive, 2,3 negative**

describe bifasicular bock

RBBB and left axis deviation. This can be due to a blocking of the left anterior or left posterior fasicle coming off the left bundle branch

how can you tell the difference between a defibrillator and a pacemaker in a Xray?

defibrillator coil/wire appears thicker than the pacemaker

what artery corresponds with the lateral leads?

left circumflex artery

Anterior-inferior leads represent which artery?

LAD

Sequence of events that show acute MI on ECG?

1. ST elevation first few hrs 2. pathological Q waves 3. T wave inversion (24 hrs later)

what artery correspond to the inferior leads?

right coronary artery

what causes ST elevation on the ECG- describe what happens to the action potential

due to a change between the AP in epicardium and endocardium during ischaemia causes a current coming towards the lead leading to ST elevation

what causes a Q wave electrophysiologically?

Usually AP goes from endocardium to epicardium. When infarction occurs, there is an 'electrical hole' leading to a negative deflection Q wave

what is the main cause of infarction?

atherosclerotic plaque rupture, thrombosis and subsequent infarction. Not atheroemboli

why can't we rely on a troponin rise from a blood test rather than the ST elevation on ECG for suspected MI?

It takes approx 6 hours for troponin levels to come back and by then it is too late. With and ECG- ST elevation is an acute change indicative of infarction. Patient is then immediately thrombolysed (rural setting no access to angioplasty) or brought to cath lab.

what do we give to a patient who comes in with SVT?

adenosine, then after it reverted do an ECG to look for WPW syndrome

what are the 3 conditions on ECG that indicate WPW?

Delta + wide QRS + short PR= WPW syndrome

how can WPW present on the ECG?

1. Retrograde WPW--\> SVT (narrow complex QRS) 2. WPW can also cause a wide QRS tachycardia that looks like VT. 3. Sometimes, when there is AF and WPW- it can present as narrow and wide QRS! This is one situation where you DON’T want to block the AV node as it reverts the impulse down the accessory bundle and cause VT.

what might you think if you saw a random strange QRS and T wave?

ventricular ectopic beat

what is a quick way of telling Left vs R axis deviation?

L axis deviation= negative in Lead 2 R axis deviation= negative in lead 1

what do you think if you see Q waves on the ECG?

previous infarct

what would see if you see crazy waves in only one lead?

muscle artifact

what is this? what condition do we see this in?

electrical alternans in pericardial effusion