ECGs

Question 1

Answer 1

Multi Focal PVC

• this indicates that there is more than one irritable focus, and each focus produces its

own QRS morphology (shape)

• when examining the above example, the first and last PVCs look the same, indicating

that the impulse originated from the same ventricular focus. These QRSs are positively

deflected and the T waves are negatively deflected

• the second PVC looks different because it originated from a different focus. It has a

negative QRS followed by a positive T wave

Question 2

Answer 2

Ventricular Bigeminy

• this reflects more irritability because the PVCs are occurring more frequently
• this occurs when every 2nd beat is a PVC
• when examining the ventricular bigeminy on figure 7-12 above, every 2nd beat is a

PVC

• the sinus beats have P waves, narrow QRSs and T waves that follow the narrow

QRSs

• quickly after the normal T waves, a premature ventricular beat arises. We know they

are PVCs because the QRS is wide and the T waves are attached to these QRSs and

deflect in the opposite deflection (the QRSs are positive and the T waves are negative)

Question 3

Answer 3

Paired PVCs (sometimes called couplets)

• this example shows 2 PVCs in a row (as well as a single PVC). These all look the

same because they originated from the same focus

• paired PVCs indicate that the single focus is quite irritable and generates two

consecutive premature impulses

Question 4

missing lesson 4 part c

Question 5

Answer 5

Run of PVCs

• when 3 or more PVCs occur consecutively, more irritability is obvious
• in this example, a narrow QRS is followed by three PVCs in arrow
• three consecutive PVCs are sometimes called triplets or a salvo of PVCs

Question 6

Answer 6

Run of PVCs (cont’d)

• this example shows 4 PVCs in a row, and these are mutifocal
• this rhythm indicates more irritability because not only are there 4 consecutive PVCs,

but these beats also arise from different foci

• the very first beat at the start of the strip is normal and narrow
• this narrow QRS is then followed by the 4 consecutive PVCs
• the 1st and 3rd of these PVCs have negative QRSs and attached positive T waves
• the 2nd and 4th PVCs have positive QRSs followed by attached negatively deflected T

waves

• some might refer to this as VT
• halfway through the strip, the baseline sinus rhythm resumes

Question 7

Answer 7

R on T PVC

• these PVCs are often the most serious and dangerous pattern of ventricular irritability
• it is called ‘R on T’, but technically it means ‘QRS on T’
• the PVC is so early that it strikes on the T wave of the preceding normal beat
• so this PVC occurs just as the ventricles are repolarizing
• if the ventricles do not have the opportunity to fully repolarize prior to the next

depolarization, the rhythm can deteriorate into VT

• figure 7-19 above shows 4 normal beats each with a depressed ST segment and a

small positive T wave

• the 5th beat on this strip strikes right on top of the T wave, so this impulse occurred just

as the ventricles were relaxing (the T wave represents ventricular repolarization)

• this means the ventricles cannot fully repolarize because they have just received

another impulse to depolarize

• the end result is a sinister and ominous VT

Question 8

Answer 8

SINUS ARRHYTHMIA

Question 9

Answer 9

SINUS BRADYCARDIA

Question 10

Answer 10

SINUS TACHYCARDIA

Distinguishable Features

• HR > 100 (AR and VR are the same)
• all other findings are normal

Question 11

Answer 11

SA BLOCK & SA ARREST (SINUS PAUSE)

Distinguishable Features

• entire PQRST missing amid the baseline rhythm
• all other findings are normal

Question 12

Answer 12

PREMATURE ATRIAL CONTRACTION (PAC)

Distinguishable Features

• the beat with the PAC is earlier than expected (premature)
• the PAC has a P wave that is abnormally shaped and differs from all the other P

waves that originate from the SA node (different site of origin = different looking

P wave)

• the premature P might be difficult to see
• it can be “lost” in the T wave of the beat preceding the PAC
• the prematurity of the beat shortens the patient’s normal RR interval, causing

an irregularity in the rhythm

Question 13

Answer 13

ATRIAL FLUTTER

Distinguishable Features

• VR may be fast or slow (varies on the degree of block)
• P waves no longer exist (atria are not contracting, they are fluttering)
• the Ps are replaced by flutter waves that appear saw-toothed or resemble

picket fences

• there are no P waves, therefore PR intervals cannot be calculated
• the QRSs are normal as conduction beyond the AV node is not affected

Question 14

Answer 14

ATRIAL FIBRILLATION

Distinguishable Features

• the HR varies (depending on whether it is controlled or uncontrolled)
• the ventricular rhythm is always irregular
• the P waves are absent (the atria are quivering, not contracting)
• because of chaotic atrial activity, only a fibrillatory line is seen where Ps would

normally exist

• no P waves, therefore no PR intervals can be measured

Question 15

Answer 15

PAROXYSMAL ATRIAL TACHYCARDIA (PAT)

Distinguishable Features

• HR is 150-250
• the rhythm is always regular (impulses are initiated with a regular rhythm)
• the P waves may not be visible if the HR is too fast
• if Ps are not visible, the PR intervals cannot be measured
• QRS complexes are usually normal (narrow) as conduction below the AV node

and within the ventricles is not usually affected

Question 16

Answer 16

PREMATURE JUNCTIONAL CONTRACTION (PJC)

• P is either inverted (with shortened PR), buried, or follows the QRS

Question 17

Answer 17

JUNCTIONAL ESCAPE RHYTHM

• HR is 40-60 (the junction initiates 40-60 impulses / minute
• the rhythm is regular (the junctional pacemaker fires at a regular rate)
• P waves are either inverted, after the QRS or absent/buried in the QRS
• PR intervals <0.12 seconds (if P waves occur prior to the QRSs)

Question 18

Answer 18

ACCELERATED JUNCTIONAL RHYTHM

• HR is 60-100
• the rhythm is regular (the junction fires impulses with a regular pattern)
• P waves are either inverted, buried or follow the QRS complex
• the PR interval is < 0.12 seconds (if a P wave precedes the QRS)
• QRS is narrow, due to normal conduction beyond the AV junction

Question 19

Answer 19

JUNCTIONAL TACHYCARDIA

• HR is 100-200
• the rhythm is regular (junctional rhythms are regular)
• P waves are either inverted, buried or follow the QRS complex
• the PR interval is < 0.12 seconds (if a P wave precedes the QRS)
• QRS is narrow, due to normal conduction beyond the AV junction

Question 20

Answer 20

FIRST DEGREE HEART BLOCK

• the rhythm is regular
• P waves are normal and there is a P wave preceding each QRS complex
• PR intervals are constant (always the same length), but prolonged (> 0.20 sec)

because impulses are delayed by the AV node

• QRS complexes are narrow (there is no disturbance beyond the AV junction)

Question 21

Answer 21

SECOND DEGREE BLOCK, TYPE I (WENCKEBACH)

• the AR is that of the SA node
• the VR is slower than the AR (because some Ps don’t reach the ventricles)
• the rhythm is always irregular
• the P waves are normal in configuration, but there are more P waves than QRS complexes

because some impulses are blocked at the AV node and do not reach the ventricles, so

the ventricles do not contract

• the PR interval is variable
• the PR interval progressively lengthens until an impulse is completely blocked at the AV

node and does not reach the ventricles, which produces a missing QRS complex

• then, a new PR interval sequence of lengthening begins again
• QRS complexes are narrow if conduction within the ventricles is normal

Question 22

Answer 22

SECOND DEGREE HEART BLOCK, TYPE II (MOBITZ II)

• the AR is that of the SA node
• the VR is 2, 3, 4 times slower than the AR
• the rhythm is regular because the block occurs at regular intervals
• the P waves are normal, but there are 2, 3 or 4 more P waves than QRSs
• the PR intervals are constant (always the same length)
• PR interval may be normal in length or can be prolonged, but it’s constant
• PR intervals only exist with every 2nd, 3rd, 4th ventricular beat (where Ps exist)
• the QRS complexes are usually narrow, but can be slightly widened
• the width of the QRS basically determines the location of the block
• if the QRS complex is narrow, the block is at the AV nodal area
• if the QRS complex is widened, the block is sub-junctional, and can more easily

advance to 3rd degree block

• therefore, the wider the QRS complex, the more serious the block

Question 23

Answer 23

THIRD DEGREE HEART BLOCK or COMPLETE HEART BLOCK (CHB)

• the AR is that of the SA node (60-100) and the VR is 20-40
• both atrial and ventricular rhythms are regular, but independent of each other
• the P waves are normal and occur regularly, but there are more P waves than

QRS complexes (some Ps may be hidden in QRS complexes)

• the PR interval is variable and totally erratic
• because the atria and ventricles have independent pacemakers, there is no relationship

between the Ps and the QRSs, and therefore a variable PR interval is present

• QRS complexes are usually wide and distorted, but can be relatively narrow if the

ventricular impulses originate nearer to the AV node