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,
2
Q
in an adult electrical impulse occurs….
A
60-100 times/min
3
Q
conduction impulse travel sequence
A
electrical impulse travels from SA node to atria to AV node
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)
5
Q
depolarization
A
electrical stimulation
6
Q
systole
A
mechanical contraction
7
Q
repolarization
A
electrical relaxation
8
Q
diastole
A
mechanical relaxation
9
Q
HR influenced by…
A
autonomic nervous system - sympathetic and parasympathetic fibers
10
Q
sympathetic fibers (adrenergic fibers); stimulation causes:
A
- positive chronotropy
- positive dromotropy
- positive inotropy
- constricts peripheral blood vessels - increases BP
11
Q
positive chronotropy
A
increased HR
12
Q
positive and negative dromotropy
A
conduction through AV node
13
Q
positive inotropy
A
force of myocardial contraction
14
Q
parasympathetic fibers stimulation causes:
A
- negative chronotropy
- negative dromotropy
- negative inotropy
- dilation of arteries - decreases BP
15
Q
negative chronotropy
A
decreased HR
16
Q
negative inotrophy
A
force of myocardial contraction
17
Q
increased sympathetic stimulation
A
exercise, anxiety, fever, administration of catecholamines (dopamine, aminophylline, dobutamine) = increased incidence of dysrhythmias
18
Q
decreased sympathetic stimulation
A
rest, anxiety reduction, beta-adrenergic blocking agents = decreased incidence of dysrhythmias
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)
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)
21
Q
a change in the waveform can be caused by
A
a change in the electrical impulse or a change in the lead
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
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
24
Q
V1 lead placement
A
fourth intercostal space, right sternal border
25
V2 lead placement
fourth intercostal space, left sternal border
26
V3 lead placement
diagonally between V2 and V4
27
V4 lead placement
fifth intercostal space, left midclavicular line
28
V5 lead placement
same level as V4, anterior axillary line
29
V6 lead placement
same level as V4 and V5, midaxillary line
30
atrial depolarization
P wave
31
ventricular depolarization
QRS interval
32
ventricular repolarization
T wave
33
P wave normal appearance (regularity, rate, resemblance)
- 1 P wave present in front of every QRS complex
- upright + round, not flat
34
P wave description
- atrial depolarization created by SA node
35
P wave measurements
- 2.5 mm or less in height
- 011 seconds or less in duration
- no more than 3 small boxes
36
PR segment description
- delay created by AV node to give atria time to dump blood into the ventricles before they contract
37
PR segment normal appearance (regularity, rate, resemblance)
- flat line after p wave
38
PR interval description
- 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
39
PR interval measurements
- 0.12-0.20 seconds
- 3-5 small boxes
40
QRS complex normal appearance (regularity, rate, resemblance)
- 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
41
QRS complex measurements
- no more than 0.12 seconds
- 1-3 small boxes
42
ST segment description
- early ventricular repolarization
- starts at end of QRS and ends at beginning of T wave
43
ST segment normal appearance (regularity, rate, resemblance)
flat, isoelectric
44
T wave normal appearance (regularity, rate, resemblance)
- should come after the QRS complex
- round, upright
45
QT interval description
- starts at beginning of QRS complex and ends after T wave
- represents total time for ventricular depolarization and repolarization
46
QT interval measurements
- 0.32 to 0.40 seconds
- varies with HR, gender, age
47
PP interval description
- beginning of 1 P wave to beginning of next P wave
- used to determine atrial rate/rhythm
48
RR interval description
- measured from one QRS complex to next QRS complex
- used to determine ventricular rate/rhythm
49
U wave description
- not always present but may indicate hypokalemia or another abnormality
50
determining heart rate: 6 second method
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
51
determining heart rate: big box method
300 divided by the number of bug boxes between 2 R's
52
how long is 5 small boxes
0.20 seconds
- each small box is 0.04 seconds
53
determining heart rhythm: regular
if intervals are same or if the difference between the intervals is < 0.08 seconds throughout the strip
54
determining heart rhythm: irregular
if intervals are different
55
normal sinus rhythm
- electrical impulse starts at a regular rate and rhythm in the SA node and travels through the normal conduction pathway
56
normal sinus rhythm: P wave
- present + consistent shape
- one precedes every QRS
- P:QRS ratio - 1:1
57
normal sinus rhythm: PR interval
consistent interval between 0.12 and 0.20 seconds
58
normal sinus rhythm: QRS complex
usually normal; may be regularly abnormal
59
normal sinus rhythm: heart rate
60-100 bpm
60
normal sinus rhythm: rhythm
regular
61
normal sinus rhythm: interventions
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
sinus bradycardia
SA node creates an impulse at a slower-than-normal rate
63
sinus bradycardia: P wave
normal + consistent shape
- one precedes every QRS
- P:QRS ration - 1:1
64
sinus bradycardia: PR interval
consistent interval between 0.12-0.20 seconds
65
sinus bradycardia: QRS complex
usually normal, may be regularly abnormal; <0.12 seconds
66
sinus bradycardia: Heart rate
<60 !!!!
67
sinus bradycardia: rhythm
regular
68
sinus bradycardia: causes
- 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
sinus bradycardia: manifestations
- slow pulse
- shortness of breath
- alteration in mental status
- angina
- hypotension
- ST segment changes or PVCs
70
sinus bradycardia: interventions if symptomatic w/ symptoms of clinical instability
- 0.5 mg atropine via IV bolus
- increases HR
- repeat every 3-5 minutes until max dosage is reached (3 mg)
71
sinus bradycardia: interventions if unresponsive to atropine
- emergency transcutaneous pacing
- pace heart to offer adequate number of beats to pump blood to major organs
- catecholamines (dopamine or epinephrine)
72
sinus tachycardia
- sinus node creates an impulse at a faster-than-normal-rate
- as HR increases, diastolic fill time decreases - reduced cardiac output
73
sinus tachycardia: P wave
- normal + consistent shape
- one precedes every QRS, but may be buried in the preceding T wave
- P:QRS ratio - 1:1
74
sinus tachycardia: PR interval
consistent interval between 0.12 to 0.20 seconds
75
sinus tachycardia: QRS complex
usually normal, but may be regularly abnormal; <0.12 seconds
76
sinus tachycardia: heart rate
>100 bpm
77
sinus tachycardia: causes
- 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
sinus tachycardia: manifestations
- rapid pulse
- syncope
- low BP
- if heart cannot compensate for decreased ventricular filing = acute pulmonary edema
79
sinus tachycardia: interventions
- 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
sinus tachycardia; intervention for narrow QRS tachycardia
beta blockers + calcium channel blockers
81
sinus tachycardia: intervention for wide QRS tachycardia
procainamide, aminodarone, stalol
82
sinus tachycardia: intervention for persistent inappropriate sinus tachycardia unresponsive to other treatments
catheter ablation
83
sinus tachycardia: intervention for POTS
increase fluid + sodium intake
84
sinus arrhythmia
- sinus node creates an impulse at an irregular rhythm
- rate usually increases with inspiration and decreases with expiration
85
sinus arrhythmia: P wave
normal + consistent shape
- one precedes every QRS
- P:QRS ratio 1:1
86
sinus arrhythmia: PR interval
consistent interval between 0.12-0.20 seconds
87
sinus arrhythmia: QRS complex
usually normal, but may be regularly abnormal
88
sinus arrhythmia: heart rate
60-100 bpm
89
sinus arrhythmia: heart rhythm
irregular
90
sinus arrhythmia: causes
- heart disease
- valvular disease
91
premature atrial complex (PAC)
- 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
premature atrial complex (PAC): P wave
- 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
premature atrial complex (PAC): PR interval
- early P wave has a shorter than normal PR interval, but still between 0.12-0.20 seconds
94
premature atrial complex (PAC): QRS complex
- usually normal but may be abnormal (aberrantly conducted PAC); may be absent (blocked PAC)
95
premature atrial complex (PAC): heart rate
depends on underlying rhythm
96
premature atrial complex (PAC): heart rhythm
irregular due to early P waves; sometimes followed by a non-compensatory pause
97
premature atrial complex (PAC): causes
- caffeine
- alcohol
- nicotine
- stretched atrial myocardium (hypervolemia)
- anxiety
- hypokalemia
- hypermetabolic states (pregnancy)
- atrial ischemia, injury, infarction
98
premature atrial complex (PAC): manifestations
- pt feels like their heart "skipped a beat"
- pulse deficit - difference between apical + radial pulse
99
premature atrial complex (PAC): interventions
- infrequent PAC = no treatment
- frequent (more than 6 per minute) = indicates worsening disease state - treat underlying cause
100
atrial fibrillation
- 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
atrial fibrillation: paroxysmal
sudden onset w/ termination that occurs spontaneously or after intervention; last
102
atrial fibrillation: persistent
continuous, lasting > 7 days
103
atrial fibrillation: long-standing persistent
continuous, lasting >12 months
104
atrial fibrillation: permanent
persistent, but decision has been made not to restore or maintain sinus rhythm
105
atrial fibrillation: nonvalvular
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
atrial fibrillation: pt is at increased risk of...
HF, myocardial ischemia, + embolic events (esp thrombi in left atrium)
107
loss in AV synchrony
- 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
atrial fibrillation: diagnostics
- 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
atrial fibrillation: P wave
no discernible P waves; irregular undulating waves that vary in amplitude/shape (fibrillatory/f waves)
- P:QRS ratio = many:1
110
atrial fibrillation: PR interval
cannot be measured
111
atrial fibrillation: QRS complex
usually normal, but may be abnormal
112
atrial fibrillation: heart rate
atrial = 300-600 bpm
ventricular = 120-200 bpm
113
atrial fibrillation: heart rhythm
highly irregular
114
atrial fibrillation: causes/risk factors
- 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
atrial fibrillation manifestations
- 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
atrial fibrillation interventions: prevent embolic events w/...
- 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
CHA2DS2-VASC scoring: low risk
- 0
- no antithrombotic therapy or aspirin therapy 75-325 mg daily
118
CHA2DS2-VASC scoring: moderate risk
- 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
points for C in CHA2DS2-VASC
- congestive heart failure (left ventricular systolic dysfunction)
- 1 point
120
points for H in CHA2DS2-VASC
-hypertension (BP/140/90 mmHg)
- 1 point
121
points for A2 in CHA2DS2-VASC
- age >/= 75 yrs
- 2 points
122
points for D in CHA2DS2-VASC
diabetes
- 1 point
123
points for S2 in CHA2DS2-VASC
- prior stroke or TIA
- 2 points
124
points for V in CHA2DS2-VASC
- vascular disease
- 1 point
125
points for A in CHA2DS2-VASC
age 65-74 years
- 1 point
126
points for SC in CHA2DS2-VASC
sex category (female gender)
- 1 point
127
atrial fibrillation interventions: control the ventricular rate of response so that resting HR < 80 bpm w/....
anti-arrhythmic agents
128
atrial fibrillation interventions: control HR
beta blocker (class II anti-arrhythmic or non-dihydropyridine calcium channel blocker (class IV anti-arrhythmic)
129
atrial fibrillation interventions: control heart rhythm
- 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
atrial fibrillation interventions: prevent atrial fibrillation
- 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
