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Nursing Science 3 > WEEK 2 - Rhythm Strip Analysis > Flashcards

WEEK 2 - Rhythm Strip Analysis Flashcards

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1
Q

Explain the steps in normal cardiac conduction

A
  1. sinus node fires and electrical impulse spreads across atria = atrial contraction (P wave).
  2. impulse is delayed at AV junction, allowing atria time to fully contract & eject blood into ventricles = isoelectric line between end of P wave & beginning of QRS complex.
  3. PR interval represents atrial depolarisation & the impulse delay in the AV junction prior to ventricular depolarisation.
  4. impulse is conducted down to the ventricles through the bundle of His, R) & L) bundle branches & Punkinje fibres causing ventricular depolarisation = QRS complex.
  5. ventricles repolarise = T wave.
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2
Q

Why is it important to monitor Lead 2 on an ECG?

A

Provides a good visualisation of the P waves.
Useful for analysing atrial & junctional arrhythmias & AV blocks.
Modified chest lead V1 enables differentiation between ventricular & supraventricular arrhythmias & identification of bundle branch blocks.

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3
Q

What does the P wave indicate?

A

That the atria have become depolarised by an impulse originating from the SA node, and the atria are about to contract.
Usually upright in all leads except for aVR and V1.

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4
Q

What does the PR interval indicate?

A

The time required for the impulse to travel from the SA node through the atria to the AV node.
Measured from start of the P wave to start of the R wave.
i.e. 3-5 small squares duration.

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5
Q

What does the QRS complex indicate?

A

Represents depolarisation of the ventricles.
Indicates normal progression of conduction from the AV junction to the Purkinje fibres.
Q = depolarisation of the interventricular septum
R = first positive deflection
S = negative deflection after the R wave

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6
Q

What does the QRS normally look like on an ECG?

A 
Follows PR interval.
2-3 small squares duration.
Should be narrow.
2-3 small squares tall but is different for each lead.
Is positive in leads 1, 2, 3, avF.
Is negative in aVR.
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7
Q

What does the ST segment indicate?

A

Represents the end of depolarisation to the beginning of ventricular repolarisation.
Alteration in the ST indicates disturbance in the electrical function of the ventricles.

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8
Q

What does the ST segment normally look like?

A

Extends from the S wave to the beginning of the T wave.

Should be on the isoelectric line.

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9
Q

What does the T wave indicate?

A

Represents ventricular repolarisation.

It occurs in two phases: the absolute & relative refractory periods.

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10
Q

What does the T wave typically look like on an ECG?

A

Follows S wave
Typically round and smooth
Usually upright in leads 1, 2, V3 & V6.
Inverted in aVR.
Variable in other leads.
The height should be no more than 1/2 the size of the preceding QRS complex.

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11
Q

What are the steps of rhythm analysis?

A
  1. determine the heart rate (i.e. no. of QRS complexes in 30 large squares = 6 secs. Multiply by 10 for HR/min).
  2. determine the ventricular rhythm (regular or irregular).
  3. check the P wave (5 Q’s).
  4. check the PR interval (3 Q’s).
  5. check the QRS interval (3 Q’s).
  6. check the ST segment (2 Q’s).
  7. is the T wave normally deflected in the same direction as the QRS?
  8. determine the site of the arrhythmia (atria, junctional or ventricular).
  9. identify the arrhythmia.
  10. evaluate the significance & nursing interventions required.
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12
Q

What is normal sinus rhythm?

A

Normal cardiac rhythm in which the SA node depolarises at a rate of 60-100 bpm.
Atrial & ventricular rhythms are regular.
P waves are upright in lead 2 but inverted in aVR.

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13
Q

What is sinus bradycardia?

A

Normal cardiac rhythm in which the SA node depolarises at a rate less < 60 bpm.
P waves are upright in lead 2.

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14
Q

What is sinus tachycardia?

A

Normal cardiac rhythm in which the SA node depolarises at a rate > 100 bpm.
P waves upright in lead 2 but inverted in aVR.

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15
Q

What are the 4 most common atrial arrhythmias?

A

Atrial flutter.
Atrial fibrillation.
Atrial tachycardia.
Premature Atrial Complexes (PAC’s).

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16
Q

What rhythms originate in the SA node?

A 
Normal sinus rhythm (60-100 bpm).
Sinus bradycardia (< 60 bpm).
Sinus tachycardia (> 100 bpm).
Sinus arrest (60-100 bpm).
Sinus pause.
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17
Q

Define atrial fibrillation.

A

Several atrial ectopic foci rapidly firing, resulting in a disorganised atrial activation.

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18
Q

What are characteristic features of atrial fibrillation?

A

Grossly irregular or irregularly irregular rhythm.
HR varies b/w 60-100 bpm.
P waves are absent but there may be fibrillatory lines.
PR interval is absent.
QRS complexes are narrow.

19
Q

What is atrial tachycardia?

A

Impulses are generated by an ectopic focus somewhere within the atrial myocardium rather than the sinus atrial node.

20
Q

What are characteristic features of atrial tachycardia?

A

HR b/w 150-250 bpm.
P waves hidden in T waves.
PR interval not visible.

21
Q

What is atrial flutter?

A

Saw tooth.

May result from an ectopic atrial focus or result from depolarisation circling the R) atrium.

22
Q

What are characteristic features of atrial flutter?

A

Atrial rate 250-350 bpm = saw tooth pattern = flutter waves/F waves.
AV node cannot keep up with such a high atrial rate & AV block occurs.
AV blocks - 2:1, 3:1, 4:1 (i.e. for every QRS complex there is either 2, 3, or 4 P waves).

23
Q

What is premature atrial contraction (PAC)?

A

PAC is not an a rhythm, it is an ectopic beat that originates from an irritable spot in the atria.
A compensatory pause may follow the PAC, prior to resumption of the underlying rhythm.

24
Q

What are junctional escape rhythms?

A

When the AV junction takes over as the heart’s pacemaker when the primary heart’s pacemake (i.e. SA node) slows down or fails to fire.

25
Q

What are characteristics of junctional escape rhythms?

A

Regular rhythm 40-60 bpm.
P wave may be inverted in leads 2, 3, aVF.
P wave can occur before, after or hidden within QRS complex.
PR interval is < 3 small squares.

26
Q

What is a ventricular arrhythmia?

A

Originate in the ventricles below the bundle of His.

Occurs when electrical impulses depolarise the myocardium via a different pathway.

27
Q

What are types of ventricular arrhythmias?

A 
Premature Ventricular Contractions 
Idioventricular rhythms
Ventricular Tachycardia
Torsades De Points 
Ventricular Flutter 
Ventricular Fibrillation 
Asystole
28
Q

What are premature ventricular contractions?

A

Caused by electrical irritability in the ventricular conduction.
May occur singular, in clusters of 2 or 3, or in repeated patterns & will occur before the expected sinus conducted beat.
May cause a reduction in CO due to decreased ventricular filling & loss of arterial kick.
May lead to VT or VF with the risk increasing in the presence of ischaemia or damaged myocardium.

29
Q

When does idioventricular rhythm occur?

A

When all the heart’s potential pacemakers fail to function or when supraventricular impulses cannot reach the ventricles due to a block in the conduction system.
Cells in the His-Purkinje system take over & act as the heart’s pacemaker to generate an impulse which acts as a safety mechanism to protect the heart from ventricular standstill (therefore should never be suppressed).

30
Q

What are characteristics of an idioventricular rhythm?

A

Rate 20-40 bpm or can be higher.
Absence of P wave & PR interval.
QRS complexes are wide & bizarre.

31
Q

What is ventricular tachycardia?

A

When 3 or more premature ventricular contractions occur in a row & the rate is greater than 120 bpm.
May be sustained or paroxysmal (self-terminating) or can degenerate into ventricular fibrillation.
Can be unpredictable & can have potentially cause sudden cardiac death.

32
Q

What are characteristics of ventricular tachycardia?

A

Atrial rate & rhythm cannot be determined.
P wave is absent or obscured by the QRS, retrograde conduction from the ventricle to the atria may occur.
QRS are bizarre, duration longer than 2-3 small squares, increased amplitude with the T wave occurring in the opposite direction.
Ventricular rhythm may be irregular.

33
Q

What is torsades de points?

A

“Twisting of the points.”

Is a polymorphic ventricular tachyarrhythmia regarded as intermediate between ventricular tachycardia and ventricular fibrillation.

34
Q

What are characteristics of torsades de points?

A

Rate is 150-250 bpm, irregular with wide QRS complexes deflecting downwards for several beats & upwards for several beats.
P wave usually absent.
May start & stop suddenly with resumption of sinus rhythm or may degenerate into ventricular fibrillation.

35
Q

What is ventricular fibrillation?

A

A chaotic pattern of electrical activity in the ventricles in which electrical impulses arise from many different foci.
Produces no effective cardiac muscular contraction & no CO if untreated ventricular fibrillation causes sudden cardiac death.

36
Q

What are characteristic features of ventricular fibrillation?

A

Atrial rhythm/rate cannot be determined.
Regular or irregular ventricular rhythm & rate of 100-200 bpm.
P wave absent.
PR interval unmeasureable.
QRS fat and tall, longer than 3 small squares.
T wave opposite direction of QRS complex.

37
Q

What is asystole?

A

Implies there is no spontaneous electrical cardiac activity, thus the ECG is NEARLY a flat line.

38
Q

When does pulseless electrical activity (PEA) or electromechanical dissociation (EMD) occur?

A

When the heart continue to work electrically but the heart muscle loses it’s ability to contract.
On ECG, there will be evidence of organised electrical activity but NO palpable pulse or measurement of blood pressure.
PEA/EMD is almost always secondary to another underlying condition.

39
Q

What is an atrioventricular (AV) heart block?

A

Results from an interruption in the conduction of impulses between the atria & the ventricles.
The block may occur at the AV node, bundle of His or the bundle branches.
AV blocks are classified by their severity which is measured according to how well the node conducts impulses & is divided by degrees (1st, 2nd, 3rd).

40
Q

What is 1st degree heart block?

A

Indicates a conduction problem which can progress to a more severe block so the patient should be monitored.
Most pts with 1st degrees AV block may not show any symptoms bcoz CO is not significantly affected.

41
Q

What are characteristics of 1st degree heart block?

A

Impulse takes longer to travel through the AV node.

Prolonged PR interval (greater than 5 small squares).

42
Q

What are characteristics of 2nd degree heart block type 1?

A

Progressive lengthening of the PR intervals until a P wave fails to be conducted & fail to produce QRS complex.
PR interval resets to normal & the cycle repeats.
QRS is narrow.
Ventricular rhythm is irregular.

43
Q

What are characteristics of 2nd degree heart block type 2?

A

P wave may or may not be conducted, depending on where in the pathway the block is occurring.
QRS complex may or may not follow a P wave.
QRS complex is arrow.
There must be 2 consecutive constant PR intervals to diagnose Type 2 AV block.

44
Q

What are characteristics of 2nd degree heart block type 3?

AKA. Complete heart block.

A

The rate can vary from 20 - 60 bpm depending where the block is i.e. the lower the block, the slower the rate.
P waves bear no relationship to the ventricular QRS complexes.
PR interval is completely variable.
There is AV dissociation with the atria depolarising at one rate and the ventricles at another.
QRS is widened and there is no correlation between the P waves and QRS complexes.
The slow ventricular rate presents a potentially life threatening situation because cardiac output can drop dramatically.

Nursing Science 3 (21 decks)

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