Pt 1 Care of Patients w/Dysrhythmias

Question 1

Properties of Cardiac Cells

• Automaticity
• Excitability

Answer 1

• Conductivity
• Contractility

Question 2

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Is the ability to respond mechanically to an impulse

Answer 2

Contractility

Question 3

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Is the ability to initiate an impulse spontaneously & continuously

Answer 3

Automaticity

Question 4

?

Is the ability to be electrically stimulated

Answer 4

Excitability

Question 5

?

Is the ability to transmit an impulse along a membrane in an orderly manner

Answer 5

Conductivity

Question 6

Conduction System of the Heart

Question 7

A normal cardiac impulse begins in the __ __ in the upper right atrium.

It spreads over the atrial myocardium via interatrial pathways & internodal pathways, causing atrial contraction.

Answer 7

sinoatrial node (SA)

Question 8

The impulse then travels to the __ __, through the bundle of His, and down the left and right bundle branches.

It ends in the __ __, which transmit the impulse to the ventricles.

Answer 8

atrioventricular node (AV)

Purkinje fibers

Question 9

Electrolytes & Dysrhythmias

• Na, K, Ca, Mg

Question 10

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Imbalances of this electrolyte are the most common electrolyte-associated cardiac arrhythmias

Answer 10

Potassium

Question 11

Potassium

• Plays a role in both nerve conduction & the heart’s ability to send an electrical impulse
• Low lvls can cause relatively stable arrhythmias, while high lvls can quickly lead to lethal arrhythmias

Answer 11

• Na, Mg, & Ca imbalances also place heart @ risk for arrhythmias

AHA

→ Arrhythmias caused by these electrolytes only occur when electrolyte lvls are extremely high or low - lvls that are typically incompatible w/human functioning, leading to death

Question 12

Cardiac Conduction System

Question 13

Atrial activity is represented by the __ __

Answer 13

P wave

Question 14

Ventricular activity is represented by the __ __

Answer 14

QRS complex

Question 15

Sinoatrial node

> Electrical impulses __-__ beats/min
__ __ on ECG

Answer 15

60-100
P wave

Question 16

Atrioventricular junction

> __ __ on ECG
Contraction known as “atrial kick”
__-__ bpm

Answer 16

PR interval

40-60

Question 17

Bundle of His

> Right & left bundle branch system
__-__ bpm

Answer 17

20-40

Question 18

ECG Monitoring

Question 19

• P wave represents atrial activity
• PR interval is measured from the beginning of the P wave to the beginning of the QRS complex

Answer 19

• Represents the time taken for the impulse to spread through the atria, AV node, bundle of His, bundle branches, & Purkinje fibers to a point immediately preceding ventricular contraction

Question 20

QRS represents __ __?

Answer 20

ventricular activity

Question 21

QRS complex has 3 distinct waves

Q wave is the first negative (downward) deflection after P wave, short & narrow, & not present in several leads

Answer 21

R wave is first positive (upward) deflection in the QRS complex

S wave is the first negative (downward) deflection after the R wave

Question 22

QRS interval is measured from the beginning to end of QRS complex

• Represents time taken for depolarization (contraction) of both ventricles (___)

Answer 22

systole

Question 23

ST segment is measured from the S wave of the QRS complex to the beginning of T wave

Represents time between ventricular depolarization & repolarization (___)

Answer 23

diastole

Question 24

**Should be isoelectric (flat)

ST segments should be flat, and when they begin to rise that’s how the EKG tracing represents an ST elevation MI (STEMI)**

Question 25

**T wave** represents time for ventricular ___ **It can represent potassium levels & oxygenation problems**

Answer 25

repolarization

Question 26

Q-T interval is measured from the beginning of the QRS complex to the end of the T wave Represents the time taken for entire electrical depolarization & repolarization of ventricles

Answer 26

**Can be important to assess as a side effect of rx's (prolonged QT intervals) [i.e., Haldol]**

Question 27

**Normal time for PR interval: -**

Answer 27

**0.12 - 0.20**

Question 28

**Normal QRS: -**

Answer 28

**0.04 - 0.10 ! If these times exceed these measurements that means there's a delay in conduction**

Question 29

Electrocardiographic Waveforms

Question 30

Assessment of Cardiac Rhythm * Interpret the rhythm AND evaluate the clinical status of the pt * Is the patient hemodynamically stable?

Answer 30

* Determine the cause of dysrhythmia * Treat the patient, not the monitor!

Question 31

When Things Go Wrong = Dysrhythmias * Disorder of impulse formation, conduction of impulses, or both * SA node = normal pacemaker of heart (60-100 bpm)

Answer 31

* Secondary pacemakers = AV node (40-60 bpm) * His-Purkinje fibers (20-40 bpm)

Question 32

If the SA node fires more slowly than a 2° PM, the electrical signals from 2° PM may "escape" 2° PM will then fire automatically @ its intrinsic rate

Answer 32

These 2° PM's may start from the AV node @ a rate of 40-60x/min or the His-Purkinje system @ at a rate of 20-40x/min

Question 33

Another way that 2° PM's can start is when they fire more rapidly than the normal PM of the SA node *Triggered beats* (early or late) may come from an __ __ or *accessory pathway* (area outside the normal conduction pathway) in the atria, AV node, or ventricles Results in a dysrhythmia, which replaces the normal sinus rhythm

Answer 33

**ectopic focus**

Question 34

Impulse started by SA node or an ectopic focus must be conducted to the entire heart Property of myocardial tissue that allows it to be depolarized by a stimulus is ___

Answer 34

excitability

Question 35

This is an important part of the transmission of the impulse from one cell to another

Answer 35

Lvl of excitability is determined by the length of time after depolarization that the tissues can be re-stimulated

Question 36

Recovery period >stimulation is the __ __ or period

Answer 36

refractory phase

Question 37

**When the normal impulse is changed, blocked, excited, or depressed, irregular heart rhythms (dysrhythmias) occur**

Answer 37

**When dysrhythmias occur, cardiac output and therefore perfusion may suffer**

Question 38

**Normal** * Rate 60-100 * Rhythm: regular * P waves present, consistent & have ratio of 1 P wave to 1 QRS * PR interval 0.12 - 0.20 * QRS duration 0.04 - 0.10

Answer 38

**Abnormal** * Rate <60 or >100 * Rhythm: irregular * P waves absent, inconsistent, or have ratio > 1:1 w/QRS * PR interval <0.12 or >0.20 * QRS duration <0.04 or >0.10