Term
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Definition
| Pacemaker cells spontaneously initiate an electrical impulse without being stimulated from another source |
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Term
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Definition
| Cardiac cells can receive an electrical stimulus and conduct it to adjacent cardiac cell |
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Term
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Definition
| Muscle contraction in response to electrical stimulus |
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Term
| Describe excitability from extra-cardiac sources: |
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Definition
| Cardiac muscle cells can respond to outside stimulus such as defibrillation, lightning strike or electrocution |
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Term
| What are the two phases of the cardiac cycle? |
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Definition
Depolarization: (Contracting phase) Na-K pump and Ca++ channels moves Na+ and Ca++ into the cell and K+ out, making the membrane postively charged
Repolarization ("resting phase") Na-K pump moves K+ and Cl- inside and Na+ outside; now at a resting phase with RMP at negative 90
These two phases occur due to movement of ions across the myocardial cell membrane:
Primary intracellular ion is potassium
Primary extracellular ion is sodium
Each ion carries its positive or negative charges with it |
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Term
| What is the resting membrane potential? |
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Definition
At rest the membrane potential (RMP) normal is negative 90 mv
Look for a normal P wave; is the atria working correctly wave
represents BOTH atria contracting, nearly simultaneously |
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Term
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Definition
| The P wave is the depolarization/contraction of both atria |
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Term
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Definition
QRS is the depolarization/contraction of ventricles.
Measured from beginning to end of complex
All QRS’s do not have a Q, R and S!
Measured from beginning to end of complex
If the first waveform is negative it is labeled Q; if the first waveform is positive it is labeled R.
Q wave is ALWAYS negative; if the first wave is negative in a QRS complex, there was no Q wave.
Normal is 0.12 seconds or less |
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Term
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Definition
T wave is the rapid phase of ventricular repolarization
Presence of T wave is the sign that repolarization has occured
T wave is larger than the P wave because the ventricles are larger than the atrium
STMI is the ST segment above the baseline = cardiac ischemia |
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Term
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Definition
| ST wave is the plateau phase of ventricular repolarization |
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Term
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Definition
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Term
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Definition
Bipolar:
The lead that records the differences in the electrical potential between the Right arm (-) to the left arm (+) |
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Term
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Definition
Bipolar:
The lead that records the differences in the electrical potential between the Right arm (-) to left leg (+)
This is an important lead because it follows the path of depolarization. This is typically observed in normal cardiac observation |
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Term
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Definition
Bipolar:
The lead that records the differences in the electrical potential between the Left arm (+) to Left leg (+)
Used for left side cardiac patients |
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Term
| What is an augmented lead? |
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Definition
Augmented leads look at electrical potential from one perspective not two. Therefore they are called unipolar, not bipolar.
Augmented leads increase the size of the waveforms
Augmented leads can record amplified waveforms from the unipolar perspective of the right and left arms, and the left leg |
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Term
| What is a precodial lead? |
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Definition
Over the heart
Measures activity over six areas of the heart |
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Term
| What are the six points to systematic interpretation of an EKG? |
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Definition
1. Rhythm (regular vs. irregular)
2. Rate
3. P waves
4. PR interval
5. QRS width
6. Interpretation of the rhythm |
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Term
| How can you interpret rhythm? |
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Definition
1. Is there a P-wave before every QRS complex?
2. Is the ventricular rhythm regular (distance between QRS complexes equal)?
3. Is the PR interval normal and consistent? (.20 seconds or less)
4. Is the QRS duration normal and consistent? (.12 seconds or less) |
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Term
| What can cause an irregular rhythm? |
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Definition
Usually caused by firing of other pacemakers or rogue cardiac cells that causes irregular atrial and/or ventricular activity
Atrial fibrillation is most common, baseline looks quivery
Premature Ventricular Contractions (PVCs) have a wider QRS (check the R-R interval), caused by stress, fatigue, stimulants |
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Term
| How do you calculate rate? |
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Definition
Based on time
Rate can be determined in three ways:
1. Digital (done by the cardiac monitor)
2. Rule of 1500 for regular rhythms (manual method done by the nurse; count small boxes between R's, divide into 1500)
3. Rule of 10 for approximate rate and irregular rates (manual method; count QRS complexes in a 6 second strip, multiply by 10) |
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Term
| How do you calculate atrial and ventricular rates? |
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Definition
Atrial: count P waves in 6 second strip, multiply by 10
Ventricular: count QRS complexes in 6 second strip, multiply by 10 |
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Term
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Definition
Indicates AV conduction; allowing ventricles to fill
Measured from beginning of the P wave to beginning of QRS
Normal: Less than 0.20 seconds, more than 0.12 |
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Term
| WHat is normal sinus rhythm? |
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Definition
Rhythm: Regular
Rate: 60-100
P Wave: Normal
PR Interval: 0.20 seconds or less
QRS: 0.12 seconds or less |
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Term
| What is sinus bradycardia? |
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Definition
Rhythm: Regular
Rate: Less than 60
P Wave: Normal
PR Interval: 0.20 seconds or less
QRS: 0.12 seconds or less
Is this rhythm clinically significant? Expect fatigue, dizzy, blood pressure is low, lightheaded, unsteady, exercise intolerance)
Put it in context! |
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Term
| WHat is Sinus Tachycardia? |
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Definition
Rhythm: Regular
Rate: 101-160
P Wave: Normal
PR Interval: 0.20 seconds or less
QRS: 0.12 seconds or less |
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Term
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Definition
Originates from singular or multiple sites outside the SA Node
Unifocal – arising from one place, all the waveforms appear similar (can be easily treated with cath lab)
Multi-focal –arising from many different places, waveforms appear different from one another |
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Term
| Where do atrial ectopic beats/rhythms originate? |
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Definition
PACs
Wandering Atrial Pacemaker
Atrial Flutter
Atrial Fibrillation |
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Term
| What are the causes of atrial ectopic beats and rhythms? |
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Definition
Stress
Alcohol
Age
Hypoxia
Abuse of stimulants
Heart valve disease
Cardiomyopathy
Heart failure |
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Term
| Describe the criteria for PACs (premature atrial contractions): |
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Definition
Rate: Usually normal
Rhythm: Premature beats, PACs upset the underlying rhythm
P Wave: Premature
PR Interval: Varies
QRS: Usually normal |
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Term
| WHat is a noncompensatory pause in PACs? |
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Definition
Non-compensatory = Unable to compensate
The sinus node, and the site firing off PACs both reside in the atria
When a PAC fires off near the sinus node, the tissue of the sinus node is depolarized
Therefore, the sinus node must repolarize before its next depolarization
This produces a pause on the EKG |
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Term
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Definition
Sometimes an ectopic atrial beat depolarizes when the heart is in a refractory state
Refractory means unable to respond
When this occurs, the PAC is blocked. You will see the premature, abnormal P wave of the PAC but there will be no QRS following it. |
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Term
| What is the criteria for Atrial Tachycardia? |
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Definition
Rate: Rapid, usually between 160-220
Rhythm: Usually regular
P Wave: Does not look like the normal P wave
PR Interval: Shortened, fast, outside the normal channel, not forced to go down the normal channel of SA node, AV node, bundles, etc.
QRS: Usually 0.12 or less, in some cases may be greater than 0.12 |
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Term
| What is the criteria for Atrial Flutter? |
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Definition
Rate: (Atrial) 220-350
Rhythm: (Atrial) Regular
P Wave: None (Saw-toothed)
PR Interval: Not measureable
QRS: Usually normal |
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Term
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Definition
Atrial flutter is diagnosed in part because of the distinctive flutter waves, also called F waves
Flutter waves are often described as “sawtooth” in appearance
Not all F waves are allowed to enter the ventricle. The AV node will block some of the F waves if the rate is too fast
The more flutter waves, the more the AV node is stopping the conduction. You want enough of a ventricular beat for functionality |
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Term
| What is the criteria for Atrial Fibrillation? |
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Definition
Atrial Rate: Cannot determine an atrial rate.
Ventricular Rate: rate can range from slow to rapid.
Rhythm: WILL ALWAYS BE Irregular
P Wave: No normal P wave, instead low voltage, erratic and constantly changing, wavy baseline
PR Interval: Not measureable
QRS: Usually normal |
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Term
| Describe Atrial Fibrillation; what is it? What are causes of a fib? WHat are possible complications? |
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Definition
Most common dysrhythmia in US
Causes: Aging, Hypoxemia, MI, heart failure, cardiomyopathy, valvular disease
Multiple, rapid impulses from many atrial foci; Atrial depolarization disorganized and chaotic
No atrial contraction, instead atria quivers
Can lead to formation of multiple thrombi in cardiac chambers and thus is associated with high risk of stroke, PE and MI |
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Term
| What are the symptoms of Atrial fibrillation? |
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Definition
Can be asymptomatic
Irregular pulse
Palpitations
Chest discomfort
SOB
Fatigue
Weakness
Anxiety
Syncope
Distended neck veins from blood back |
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Term
| What interventions are there for Atrial fibrillation? |
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Definition
Interventions:
1. If new onset (< 48 hrs): the treatment is to ↓ ventricular response & convert rhythm back to normal sinus (NSR)
-Drugs
-Cardioversion – synchronized
2. If prolonged (> 48 hrs)
-Anticoagulant therapy
-IV or SQ
-Long-term anticoagulation (PO) |
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Term
| What are the criteria for a wandering atrial pacemaker? |
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Definition
Rate: Usually between 60-100, sometimes slower
Rhythm: May be irregular
P Wave: P wave shape varies, need to see at least three different P waves diagnose (WAP)
PR Interval: Varies
QRS: Usually normal |
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Term
| What is the importance of the SA node? |
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Definition
| b. SA node: pacemaker of the heart, sits high in the right atrium, conduction fans out toward AV node |
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Term
| WHat is the importance of the AV node? |
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Definition
c. AV node: controls when impulse moves into the ventricles, important for adequate ventricular filling; if there is not enough time to fill ventricle, the cardiac output is decreased
i. Right side is faster to be depolarized because the mass and workload are smaller, so AV node sends impulse to left side bundle FIRST to give it a headstart |
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Term
| WHat can a larger P wave indicate? |
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Definition
| Indicative of hypertrophy, and right side workload increasing. |
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Term
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Definition
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Term
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Definition
| Every other beat is a PAC (premature atrial contraction) clue that the ectopic beat is about to take over the SA node, if the heart rate increases, can lead to atrial tachycardia |
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Term
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Definition
Atrial Fibrillation
Rhythm: Irregular
Rate: Very fast (> 350 bpm) for Atrial, but ventricular rate may be slow, normal or fast
P Wave: Absent. Erratic waves are present
PR Interval: Absent
QRS: Normal but may be widened if there are conduction delays
Notes |
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Term
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Definition
Rhythm: Regular or irregular
Rate: Fast (250-350 bpm) for Atrial, but ventricular rate is often slower
P Wave: Not observable, but saw-toothed flutter waves are present
PR Interval: Not measureable
QRS: Normal (0.06-0.10 sec) |
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Term
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Definition
Sinus Bradycardia
Rhythm Regular
Rate Slow (< 60 bpm)
P Wave Normal
PR Interval Normal (0.12-0.20 sec)
QRS Normal (0.06-0.10 sec)
Notes |
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Term
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Definition
Normal Sinus Rhythm
Rhythm Regular
Rate Normal (60-100 bpm)
P Wave Normal (positive & precedes each QRS)
PR Interval Normal (0.12-0.20 sec)
QRS Normal (0.06-0.10 sec) |
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Term
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Definition
Premature Atrial Complex
Rhythm Irregular
Rate Usually normal but depends on underlying rhythm
P Wave Premature, positive and shape is abnormal
PR Interval Normal or longer
QRS 0.10 sec or less |
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Term
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Definition
Sinus Tachycardia
Rhythm Regular
Rate Fast (> 100 bpm)
P Wave Normal, may merge with T wave at very fast rates
PR Interval Normal (0.12-0.20 sec)
QRS Normal (0.06-0.10 sec)
Notes QT interval shortens with increasing heart rate |
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Term
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Definition
Sinus Arrhythmia
Rhythm Irregular, varying with respiration
Rate Normal (60-100 bpm) and rate may increase during inspiration
P Wave Normal
PR Interval Normal (0.12-0.20 sec)
QRS Normal (0.06-0.10 sec)
Notes Heart rate frequently increases with inspiration, decreasing with expiration |
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Term
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Definition
Wandering Atrial Pacemaker
Rhythm May be irregular
Rate Normal (60-100 bpm)
P Wave Changing shape and size from beat to beat (at least three diffferent forms)
PR Interval Variable
QRS Normal (0.06-0.10 sec)
Notes T wave normal. If heart rate exceeds 100 bpm, then rhythm may be multifocal atrial tachycardia (MAP) |
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