Ecgs 3: Rhythm And P

Front 1

What out our three questions?

Back 1

What is the:

1) Rhythm - Ir/regular

2) Rate:

Regular = 300, 150, 100, 75, 60, 50, slow

Irregular = 10 sec strip: QRS X 6, 6 sec strip: QRS X 10

3) Width:

<120ms = Supraventricular in origin

>120 ms = Ventricular origin or conduction block

Front 2

What is the Rhythm framework?

Back 2

1) Regular?: One point of origin, R-R intervals are the same

2) Pattern/Group Beating: Predictable

3) Irregular: Multifocal origin or unpredictable interruption of conduction, R-R intervals unpredicatble

Front 3

What does the width of the QRS complex tell you?

Back 3

Narrow = origin above AV junction

Wide = Origin below AV junction or origin above AV junction but conduction slowed past AV node (rate not affected)

Front 4

What do you need to review when analysing the P wave?

Back 4

Relation to QRS: No Pwave, 3rd degree block, Blocksaffecting PR interval

Shape

RegularSlow Ventricular Reponses: Aflutter, AT, AVNRT

IrregularSVRs: Afib orMAT

Size: LAH and RAH

Abnormalities

Front 5

What should we check on shape of P wave?

Back 5

Uniform size and contour beat to beat.

Lead II upright (sees R-atrium, tiny notch acceptable), in V1 biphasic (seesL-atrium), in AVR negative.

Front 6

What should we check on P wave size?

Back 6

<0.12s wide (3 blocks), <2.5 squares high, V1 Components equal

Front 7

What abnormalities can be found by looking at the P wave?

Back 7

3rd degree block

Sick sinus

Extra/early P

RAH

LAH

SVTs

Multifocal

Retrograde conduction

Front 8

What is abnormal about the P wave in 3rd degree block?

Back 8

Variable relationship

Front 9

What is abnormal about the P wave in Sick sinus?

Back 9

Missing P waves

Front 10

What is abnormal about the heart wave in extra/early P waves

Back 10

Premature atrial beat, tend to reset SA node

Front 11

What is abnormal about the P wave in RAH

Back 11

Larger, spiky P in II

Called P-pulmonale

Front 12

What is abnormal about the P wave in LAH

Back 12

Larger neg in V1, bifid in II

Called P-mitrale

Front 13

What is abnormal about the P wave in SVTs

Back 13

Afl: Sawtooth, check ratio

AT: spiky

SVT: Not seen

Always check rate

Front 14

What is abnormal about the P wave in Multifocal?

Back 14

MAT: every P has QRS

AFib: Squiggly baseline with QRS

Front 15

What is abnormal about the P wave in Retrograde conduction

Back 15

E.g. junctional pacemaker

Neg P in II

Front 16

So... is sinus arrythmia normal?

Back 16

Yes, it is similarto normal sinus rhythm except that PP and RR intervals are irregular becausethe SA node discharges at a variable frequency.

In children and youngadults the irregularity is cyclic or related to respiration with the rateincreasing during inspiration and decreasing during expiration.

A cyclicsinus arrhythmia disappears upon exercise or breath holding and is accentuatedby deep breathing.

Front 17

What is an idiojunctional rhythm?

Back 17

TheSA pacemaker is suppressed or its impulses are blocked and the heart iscontrolled by impulses originating at the AV junction.

Such impulsesspread to the ventricles and also to the atria (in retrograde fashion).

Therefore, Pwaves are negative in II and positive AVR and occur regularly at a rate40-60.

Front 18

What can happen to the P wave in an idiojunctional rhythm

Back 18

Depending upon whether retrograde conduction to the atria is faster, slower or similar to antegrade conduction to the ventricles, P waves either precede QRS complexes, the PR interval is less than 0.12 sec or follow QRS complexes by no more than 0.20 sec or are buried in the QRS complexes

Front 19

Please explain what 3rd degree block is?

Back 19

BlockImpulses originate in the SA node or inan atrial pacemaker but none of them is conducted through the AV junction tothe ventricles.

P waves are positive in II and occur regularly at a rate60-100; rarely atrial activity is represented by inverted (ectopic) P waves.

Since all P waves are blocked, the ventricles are activated by impulses arising(through escape mechanism) in pacemaker cells below the bifurcation of thecommon bundle.

The resulting QRS complexes are wide, slurred, frequentlyof RBBB configuration and occur regularly at a rate 20-40 (the so-called idioventricular rhythm).

P waves occurring at afaster rate are completely unrelated to QRS complexes (AV dissociation)

Front 20

What are the characteristics of a sinus tachycardia

Back 20

NB: T and P waves move closer together until they eventually merge

Impulsesoriginate in the SA node. Rate= 100-160/min in adults

P upright in II and negative in AVR with identical orslightly different size and contour from beat to beat.

P:QRS ratio1:1.

Usually appears and subsides gradually. Vagalstimulation produces gradual slowing which reverses when pressure isreleased. Exercise further increases the rate.

Front 21

What are the characteristics of supraventricular tachycardia?

Back 21

Impulsesoriginate in a supraventricular pacemaker at a rate 150-250.

P waves cannot be identified: either they merge with preceding T waves or are buried inQRS complexes.

QRS complexes are narrow but occasionally QRS are wide and have RBBB configuration due to aberrancy (the intermittent abnormal intraventricular conduction of a supraventricular impulse.)

Front 22

When do you get physiological or pathological bradycardia?

Back 22

Physiological bradycardia: in healthy individuals (usually athletes) with increased vagal tone. Exercise or atropine always increase the rate to normal.

Pathological bradycardia: MI or other heart disease involving the SA node, drugs such as digitalis or beta blockers and in elderly subjects. Exercise or atropine often fail to increase the rate to normal.

Front 23

What happens to the ECG in Wolff-Parkinson-White pattern?

Back 23

This is when you have AVRT.

ECG show sinus rhythm with a short PR interval and a wide QRS complex due todelay in the upstroke of the R wave. This slurred upstroke is referred to as adelta wave.

NB in the inferior leads the delta wave polarity is negativeand this often leads to inappropriate diagnosis of inferior myocardialinfarction. This pseudo-inferior infarct pattern is typical of a manifest posteroseptal accessory pathway.

Front 24

Tell me about 1st degree AV block

Back 24

Rhythmicimpulses originating in the SA node are conducted abnormally slow through theAV junction to the ventricles.

PR interval is prolonged beyond 0.20 sec inadults.

Frequently associated with vagotonia

Front 25

What happens to ECG in 2nd Degree Type I block? (Wenkebach)

Back 25

Rhythmicimpulses originating in the SA node are conducted through the AV junction atprogressively slower speed.

P waves are positive in II and negative in AVR and occur regularly at a rate 60-100.

A blocked Pwave occurs after 2-5 conducted P waves and this so-called Wenckebachcycle or period is repeated. The P:QRS ratio of 3:2, 4:3, 5:4 may beconstant in all cycles or may vary from cycle to cycle.

The PR intervalimmediately following a dropped QRS complex is the shortest and may be normalor prolonged; with each successive beat the PR interval becomes progressivelylonger until a P wave is blocked. QRS complexes may be normal or wide andbizarre if BBB is present

Front 26

What happens to ECG in 2nd Degree Type II block? (Mobitz)

Back 26

Rhythmicimpulses originating in the SA node are intermittently blocked at the AVjunction.

P waves are positive in II and occur regularly. Only unblocked P waves are followed by a QRS complexresulting in the P:QRS ratio 2:1, 3:1, 4:1, etc. and therefore a slowventricular rate.

It may be regular or mayvary in the same tracing. The PR interval of the conducted beats isnormal or prolonged and usually constant.

QRS complexes are frequentlywide and have RBBB configuration if the lesion extends below the AV junction

Front 27

What is a bifascicular block?

Back 27

Thismeans two (2) of the three (3) fascicles (in diagram) are blocked.

Front 28

What are the most important type of bifascicular blocks and why?

Back 28

Right bundle branch block

Left anterior fascicular block.

Only one fascicle is left for conduction, and if that fascicle is intermittently blocked, the dangerous Mobitz 2 is set up!

Front 29

What is the clue to fascicular blocks in you ddx?

Back 29

Remember that axis deviation is the clue.

In your differential, consider posterior fascicular blocks with right axis deviation and consider anterior fascicular blocks with left axis deviation.

Fascicular blocks cause axis deviations, like infarcts and hypertrophy.

If you see a left or right axis deviation, first look for infarct or hypertrophy. If neither are present, the remaining diagnosis of fascicular block is usually correct.