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module 2 Flashcards

1
Q

normal electrical conduction

A

electrical impulse that stimulates/paces cardiac muscle originates in SA node: located near superior vena cava in right atriu,

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2
Q

in an adult electrical impulse occurs….

A

60-100 times/min

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3
Q

conduction impulse travel sequence

A

electrical impulse travels from SA node to atria to AV node

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4
Q

conduction

A
  • electrical stimulation of muscle cells of atria causes them to contract
  • structure of AV node slows electrical impulse - gives atria time to contract and fill the ventricles w/ blood
  • referred to as atrial kick = nearly 1/3 of the volume ejected during ventricular contractions
  • impulse travels through bundle of HIS to the right and left ventricles and the Purkinje fibers (located in the ventricular muscle)
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5
Q

depolarization

A

electrical stimulation

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6
Q

systole

A

mechanical contraction

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7
Q

repolarization

A

electrical relaxation

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8
Q

diastole

A

mechanical relaxation

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9
Q

HR influenced by…

A

autonomic nervous system - sympathetic and parasympathetic fibers

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10
Q

sympathetic fibers (adrenergic fibers); stimulation causes:

A
  • positive chronotropy
  • positive dromotropy
  • positive inotropy
  • constricts peripheral blood vessels - increases BP
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11
Q

positive chronotropy

A

increased HR

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12
Q

positive and negative dromotropy

A

conduction through AV node

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13
Q

positive inotropy

A

force of myocardial contraction

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14
Q

parasympathetic fibers stimulation causes:

A
  • negative chronotropy
  • negative dromotropy
  • negative inotropy
  • dilation of arteries - decreases BP
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15
Q

negative chronotropy

A

decreased HR

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16
Q

negative inotrophy

A

force of myocardial contraction

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17
Q

increased sympathetic stimulation

A

exercise, anxiety, fever, administration of catecholamines (dopamine, aminophylline, dobutamine) = increased incidence of dysrhythmias

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18
Q

decreased sympathetic stimulation

A

rest, anxiety reduction, beta-adrenergic blocking agents = decreased incidence of dysrhythmias

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19
Q

the electrocardiogram

A

all electrodes have an adhesive substance to secure to the skin + substance that reduces skin’s electrical impedance (facilitates transfer of ions from tissue to electrons in the electrode)

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20
Q

putting on the electrocardiogram

A
  • gently abrade skin with clean, dry gauze - exposes inner conductive layer of epidermis (reduces skin impedance)
  • do not use alcohol! - increases skin’s electrical impedance + hinders detection of cardiac electrical signal
  • clip chest hair if needed
  • poor electrode adhesion will cause significant artifact (distorted/extraneous ECG waveforms)
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21
Q

a change in the waveform can be caused by

A

a change in the electrical impulse or a change in the lead

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22
Q

electrophysiology (EP) study

A

electrodes are placed inside the heart in order to obtain an intracardiac ECG
- helps determine the most effective treatment plan

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23
Q

standard 12-lead ECG how many electrodes

A

10
- 6 on chest
- 4 on limbs
- reflects the electrical activity primarily in the left ventricle
- additional electrodes may be required to obtain more complete information

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24
Q

V1 lead placement

A

fourth intercostal space, right sternal border

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25
Q

V2 lead placement

A

fourth intercostal space, left sternal border

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26
Q

V3 lead placement

A

diagonally between V2 and V4

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27
Q

V4 lead placement

A

fifth intercostal space, left midclavicular line

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28
Q

V5 lead placement

A

same level as V4, anterior axillary line

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29
Q

V6 lead placement

A

same level as V4 and V5, midaxillary line

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30
Q

atrial depolarization

A

P wave

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31
Q

ventricular depolarization

A

QRS interval

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32
Q

ventricular repolarization

A

T wave

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33
Q

P wave normal appearance (regularity, rate, resemblance)

A
  • 1 P wave present in front of every QRS complex
  • upright + round, not flat
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34
Q

P wave description

A
  • atrial depolarization created by SA node
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35
Q

P wave measurements

A
  • 2.5 mm or less in height
  • 011 seconds or less in duration
  • no more than 3 small boxes
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36
Q

PR segment description

A
  • delay created by AV node to give atria time to dump blood into the ventricles before they contract
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37
Q

PR segment normal appearance (regularity, rate, resemblance)

A
  • flat line after p wave
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38
Q

PR interval description

A
  • starts at beginning of P wave + extends to beginning of QRS complex
  • amount of time needed for sinus node stimulation, atrial depolarization, and conduction through the AV node before ventricular depolarization
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39
Q

PR interval measurements

A
  • 0.12-0.20 seconds
  • 3-5 small boxes
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40
Q

QRS complex normal appearance (regularity, rate, resemblance)

A
  • Q = 1st negative deflection after P wave
  • R = 1st positive deflection after P wave
  • S = 1st negative deflection after R wave
  • should not be wide or narrow
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41
Q

QRS complex measurements

A
  • no more than 0.12 seconds
  • 1-3 small boxes
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42
Q

ST segment description

A
  • early ventricular repolarization
  • starts at end of QRS and ends at beginning of T wave
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43
Q

ST segment normal appearance (regularity, rate, resemblance)

A

flat, isoelectric

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44
Q

T wave normal appearance (regularity, rate, resemblance)

A
  • should come after the QRS complex
  • round, upright
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45
Q

QT interval description

A
  • starts at beginning of QRS complex and ends after T wave
  • represents total time for ventricular depolarization and repolarization
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46
Q

QT interval measurements

A
  • 0.32 to 0.40 seconds
  • varies with HR, gender, age
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47
Q

PP interval description

A
  • beginning of 1 P wave to beginning of next P wave
  • used to determine atrial rate/rhythm
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48
Q

RR interval description

A
  • measured from one QRS complex to next QRS complex
  • used to determine ventricular rate/rhythm
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49
Q

U wave description

A
  • not always present but may indicate hypokalemia or another abnormality
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50
Q

determining heart rate: 6 second method

A

count the number of R’s in between the 6 second strips & multiply by 10
- ex = 6 R’s x 10 = 60 beats per minute

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51
Q

determining heart rate: big box method

A

300 divided by the number of bug boxes between 2 R’s

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52
Q

how long is 5 small boxes

A

0.20 seconds
- each small box is 0.04 seconds

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53
Q

determining heart rhythm: regular

A

if intervals are same or if the difference between the intervals is < 0.08 seconds throughout the strip

54
Q

determining heart rhythm: irregular

A

if intervals are different

55
Q

normal sinus rhythm

A
  • electrical impulse starts at a regular rate and rhythm in the SA node and travels through the normal conduction pathway
56
Q

normal sinus rhythm: P wave

A
  • present + consistent shape
  • one precedes every QRS
  • P:QRS ratio - 1:1
57
Q

normal sinus rhythm: PR interval

A

consistent interval between 0.12 and 0.20 seconds

58
Q

normal sinus rhythm: QRS complex

A

usually normal; may be regularly abnormal

59
Q

normal sinus rhythm: heart rate

A

60-100 bpm

60
Q

normal sinus rhythm: rhythm

A

regular

61
Q

normal sinus rhythm: interventions

A

although normal sinus rhythm is generally indicative of good cardiovascular health, pts with an average resting HR that exceeds 90 bpm over a 24-hr period should receive a full medical workup fro potential underlying causes

62
Q

sinus bradycardia

A

SA node creates an impulse at a slower-than-normal rate

63
Q

sinus bradycardia: P wave

A

normal + consistent shape
- one precedes every QRS
- P:QRS ration - 1:1

64
Q

sinus bradycardia: PR interval

A

consistent interval between 0.12-0.20 seconds

65
Q

sinus bradycardia: QRS complex

A

usually normal, may be regularly abnormal; <0.12 seconds

66
Q

sinus bradycardia: Heart rate

A

<60 !!!!

67
Q

sinus bradycardia: rhythm

A

regular

68
Q

sinus bradycardia: causes

A
  • lower metabolic needs (sleep, athletic training, hypothyroidism) - normal finding
  • vagal stimulation (vomiting, suctioning, severe pain)
  • meds: Calcium channel blockers, amiodarone, beta blockers
  • idiopathic sinus node dysfunction (sick sinus syndrome) [risk factors = increased age, white, obese, hypertension, lower HR, hx of cardio events
  • increased ICP
  • coronary artery disease (MI of the inferior wall)
  • hypoxemia (unstable + symptomatic type)
  • altered mental status
  • acute decompensated heart failure
69
Q

sinus bradycardia: manifestations

A
  • slow pulse
  • shortness of breath
  • alteration in mental status
  • angina
  • hypotension
  • ST segment changes or PVCs
70
Q

sinus bradycardia: interventions if symptomatic w/ symptoms of clinical instability

A
  • 0.5 mg atropine via IV bolus
  • increases HR
  • repeat every 3-5 minutes until max dosage is reached (3 mg)
71
Q

sinus bradycardia: interventions if unresponsive to atropine

A
  • emergency transcutaneous pacing
  • pace heart to offer adequate number of beats to pump blood to major organs
  • catecholamines (dopamine or epinephrine)
72
Q

sinus tachycardia

A
  • sinus node creates an impulse at a faster-than-normal-rate
  • as HR increases, diastolic fill time decreases - reduced cardiac output
73
Q

sinus tachycardia: P wave

A
  • normal + consistent shape
  • one precedes every QRS, but may be buried in the preceding T wave
  • P:QRS ratio - 1:1
74
Q

sinus tachycardia: PR interval

A

consistent interval between 0.12 to 0.20 seconds

75
Q

sinus tachycardia: QRS complex

A

usually normal, but may be regularly abnormal; <0.12 seconds

76
Q

sinus tachycardia: heart rate

A

> 100 bpm

77
Q

sinus tachycardia: causes

A
  • physiologic/psychological stress: acute blood loss, anemia, shock, hypervolemia, hypovolemia, heart failure, pain, hypermetabolic states, fever exercise, anxiety
  • medications that stimulate the sympathetic response (catecholamines, aminophylline, atropine), stimulants (caffeine, nicotine), and illicit drugs (amphetamines, cocaine, ecstasy)
  • enhanced automaticity of the SA node and/or excessive sympathetic tone with reduced parasympathetic tone that is out of proportion to physiologic demands = inappropriate sinus tachycardia
  • autonomic dysfunction: postural orthostatic tachycardia syndrome (POTS); characterized by tachycardia w/o hypotension when moving to a standing position, or w/ frequent symptoms )palpitations, light-headedness, weakness, and blurred vision that occur with standing)
78
Q

sinus tachycardia: manifestations

A
  • rapid pulse
  • syncope
  • low BP
  • if heart cannot compensate for decreased ventricular filing = acute pulmonary edema
79
Q

sinus tachycardia: interventions

A
  • persistent + causing hemodynamic instability = synchronized cardioversion
  • vagal maneuvers: carotid sinus massage, gagging, bearing down against a closed glottis (as if having a bowel movement), forceful/sustained coughing, applying a cold stimulus to the face (face in ice water)
  • adenosine (vasodilator) to interrupt tachycardia
  • increased parasympathetic stimulation = slower conduction through AV node + blocking reentry of rerouted impulse
80
Q

sinus tachycardia; intervention for narrow QRS tachycardia

A

beta blockers + calcium channel blockers

81
Q

sinus tachycardia: intervention for wide QRS tachycardia

A

procainamide, aminodarone, stalol

82
Q

sinus tachycardia: intervention for persistent inappropriate sinus tachycardia unresponsive to other treatments

A

catheter ablation

83
Q

sinus tachycardia: intervention for POTS

A

increase fluid + sodium intake

84
Q

sinus arrhythmia

A
  • sinus node creates an impulse at an irregular rhythm
  • rate usually increases with inspiration and decreases with expiration
85
Q

sinus arrhythmia: P wave

A

normal + consistent shape
- one precedes every QRS
- P:QRS ratio 1:1

86
Q

sinus arrhythmia: PR interval

A

consistent interval between 0.12-0.20 seconds

87
Q

sinus arrhythmia: QRS complex

A

usually normal, but may be regularly abnormal

88
Q

sinus arrhythmia: heart rate

A

60-100 bpm

89
Q

sinus arrhythmia: heart rhythm

A

irregular

90
Q

sinus arrhythmia: causes

A
  • heart disease
  • valvular disease
91
Q

premature atrial complex (PAC)

A
  • electrical impulse starts in the atrium before the next normal impulse of the sinus node
  • often seen with sinus tachycardia and common in normal hearts
92
Q

premature atrial complex (PAC): P wave

A
  • an early and different P wave may be seen or may be hidden in the T wave
  • other P waves in the strip are consistent
  • P:QRS ratio - usually 1:1
93
Q

premature atrial complex (PAC): PR interval

A
  • early P wave has a shorter than normal PR interval, but still between 0.12-0.20 seconds
94
Q

premature atrial complex (PAC): QRS complex

A
  • usually normal but may be abnormal (aberrantly conducted PAC); may be absent (blocked PAC)
95
Q

premature atrial complex (PAC): heart rate

A

depends on underlying rhythm

96
Q

premature atrial complex (PAC): heart rhythm

A

irregular due to early P waves; sometimes followed by a non-compensatory pause

97
Q

premature atrial complex (PAC): causes

A
  • caffeine
  • alcohol
  • nicotine
  • stretched atrial myocardium (hypervolemia)
  • anxiety
  • hypokalemia
  • hypermetabolic states (pregnancy)
  • atrial ischemia, injury, infarction
98
Q

premature atrial complex (PAC): manifestations

A
  • pt feels like their heart “skipped a beat”
  • pulse deficit - difference between apical + radial pulse
99
Q

premature atrial complex (PAC): interventions

A
  • infrequent PAC = no treatment
  • frequent (more than 6 per minute) = indicates worsening disease state - treat underlying cause
100
Q

atrial fibrillation

A
  • causes electrophysiologic changes in the atrial myocardium (remodeling of the atrial electrical circuit) and structural remodeling (fibrosis) - rapid, disorganized, uncoordinated twitching of the atrial musculature
  • hyperactive autonomic ganglia in the CANS are thought
101
Q

atrial fibrillation: paroxysmal

A

sudden onset w/ termination that occurs spontaneously or after intervention; last </= days; may recur

102
Q

atrial fibrillation: persistent

A

continuous, lasting > 7 days

103
Q

atrial fibrillation: long-standing persistent

A

continuous, lasting >12 months

104
Q

atrial fibrillation: permanent

A

persistent, but decision has been made not to restore or maintain sinus rhythm

105
Q

atrial fibrillation: nonvalvular

A

absence of mitral stenosis, valve replacement or repair
- origin of embolisms resulting in stroke for pts w/ nonvalvular atrial fibrillation is more often the left atrial appendage

106
Q

atrial fibrillation: pt is at increased risk of…

A

HF, myocardial ischemia, + embolic events (esp thrombi in left atrium)

107
Q

loss in AV synchrony

A
  • the atria and ventricles contract at different times
  • atrial kick is loss
  • the last part of diastole and ventricular filling, which accounts for 25-30% of CO
108
Q

atrial fibrillation: diagnostics

A
  • history + physical exam (frequency of symptoms, precipitating factors, response to medications
  • 12 lead ECG to verify rhythm
  • transthoracic echocardiogram (TEE) = identifies presence of valvular heart disease, provide information about left ventricular (LV) and right ventricular (RV) size/function, RV pressure (to identify pulmonary hypertension), LV hypertrophy and presence of left atrial thrombi
  • blood test to screen for diseases that are known risks
  • chest x-ray to evaluate pulmonary vasculature in pt suspected of having pulmonary hypertension
  • exercise stress test: to exclude myocardial ischemia or reproduce exercise-induced atrial fibrillation
  • holter or event monitoring
109
Q

atrial fibrillation: P wave

A

no discernible P waves; irregular undulating waves that vary in amplitude/shape (fibrillatory/f waves)
- P:QRS ratio = many:1

110
Q

atrial fibrillation: PR interval

A

cannot be measured

111
Q

atrial fibrillation: QRS complex

A

usually normal, but may be abnormal

112
Q

atrial fibrillation: heart rate

A

atrial = 300-600 bpm
ventricular = 120-200 bpm

113
Q

atrial fibrillation: heart rhythm

A

highly irregular

114
Q

atrial fibrillation: causes/risk factors

A
  • increasing age
  • hypertension
  • diabetes
  • obesity
  • valvular heart disease
  • heart failure
  • obstructive sleep apnea
  • alcohol consumption - moderate (1-3 drinks/day and high (>3 drinks/day)
  • hyperthyroidism
  • cardiac ischemia
  • cardiac inflammatory disease (pericarditis, myocarditis, amyloidosis)
  • myocardial hypertrophy, fibrosis, or dilation
  • atrial remodeling
  • postoperative cardiac surgery
115
Q

atrial fibrillation manifestations

A
  • palpitations
  • shortness of breath
  • hypotension
  • dyspnea
    on exertion
  • fatigue
  • pulse deficit
  • may not have symptoms - increases the risk of stroke, HF, or other complication to go unnoticed
116
Q

atrial fibrillation interventions: prevent embolic events w/…

A
  • antithrombotic drugs (anticoagulants, antiplatelets)
  • oral therapy recommended for most pts w/ nonvalvular atrial fibrillation
  • use CHA2DS2-VASC scoring system to assist in assessment of stroke risk + selection of therapy
117
Q

CHA2DS2-VASC scoring: low risk

A
  • 0
  • no antithrombotic therapy or aspirin therapy 75-325 mg daily
118
Q

CHA2DS2-VASC scoring: moderate risk

A
  • 1 or higher
  • warfarin or direct-actong oral anticoagulant or factor Xa inhibitor (apixaban)
  • warfarin = weekly INR testing (therapeutic level for INR = 2.0-3.0)
  • direct-acting oral anticoagulants + Factor Xa inhibitors require baseline assessment of hemoglobin, hematocrit, liver/renal function, INR
119
Q

points for C in CHA2DS2-VASC

A
  • congestive heart failure (left ventricular systolic dysfunction)
  • 1 point
120
Q

points for H in CHA2DS2-VASC

A

-hypertension (BP/140/90 mmHg)
- 1 point

121
Q

points for A2 in CHA2DS2-VASC

A
  • age >/= 75 yrs
  • 2 points
122
Q

points for D in CHA2DS2-VASC

A

diabetes
- 1 point

123
Q

points for S2 in CHA2DS2-VASC

A
  • prior stroke or TIA
  • 2 points
124
Q

points for V in CHA2DS2-VASC

A
  • vascular disease
  • 1 point
125
Q

points for A in CHA2DS2-VASC

A

age 65-74 years
- 1 point

126
Q

points for SC in CHA2DS2-VASC

A

sex category (female gender)
- 1 point

127
Q

atrial fibrillation interventions: control the ventricular rate of response so that resting HR < 80 bpm w/….

A

anti-arrhythmic agents

128
Q

atrial fibrillation interventions: control HR

A

beta blocker (class II anti-arrhythmic or non-dihydropyridine calcium channel blocker (class IV anti-arrhythmic)

129
Q

atrial fibrillation interventions: control heart rhythm

A
  • Afib lasting > 48 hrs : anticoagulation prior to attempts to restore sinus rhythm
  • in absence of therapeutic anticoagulation, TEE performed prior to cardioversion to identify left atrial thrombus formation
    pharmacologic cardioversion - flecainide (recurrent afib use at home), dofetilide (preferred), propafenone, amiodarone, + IV ibutilide (most effective if given within 7 days on onset of afib
130
Q

atrial fibrillation interventions: prevent atrial fibrillation

A
  • beta blocker at least 24 hours prior to cardiac surgery
  • cholesterol-lowering drugs (HMG-CoA reductase inhibitors): prevention of new onset afib
  • ACE inhibitors + ARBs decrease incidence of afib for pts w/ concomitant hypertension

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