EKG Basics Flashcards
On an EKG strip, what does the vertical axis represent?
Time
On an EKG strip, what does the horizontal axis represent?
Voltage (mV)
What does 1 small box represent?
0.04s and 0.1mV
What do 5 small boxes represent?
1 big box = 0.2s, 0.5mV
What is used to ensure the ECG machine is properly calibrated?
Calibration mark
(standard = 1.0mV = 2 large boxes = 10 vertical squares)
What is defined as a flat line in which there is no electrical activity or impulses are too weak to be detected?
Isoelectric line
What is used as a baseline to ID changes in electrical movement?
Isoelectric line
What is defined as markings that are not products of heart’s electrical activity (ex. pt movement)?
Artifact
What can artifacts mimic?
Life threatening dysrhythmias (therefore must r/o)
The P wave represents depolarization of the RA and LA and is typically of what duration and what amplitude?
Duration- 0.06- 0.10s
Amplitude- 0.5- 2.5mm
Where is the PR interval measured and what is the typicaly duration?
Start of P wave to beginning of QRS complex
Normal = 0.12- 0.20s
The PR segment represents depolarization of the heart from the SA node through the atria, AV node, and His-purkinj system and is measured where?
Flat/ isoelectric line between end of P wave and start of QRS complex
The QRS complex represents depolarization of the ventricles, is typically upright and narrow and is of what duration?
0.06- 0.12s
(will always be named QRS regardless if missing a wave)
What is the Q wave on an EKG strip?
1st negative deflection
What is the R wave on an EKG strip?
Any positive deflection following Q wave or PR segment
What is the S wave on an EKG strip?
Any negative deflection below baseline following R wave
Where is the ST segment measured on an EKG strip?
Flat line following QRS complex
Where is the T wave on an EKG segment?
Larger, slightly, asymmetrical (vs P wave) waveform that follows ST segment (ventricular repolarization)
What is the J point on an EKG strip?
Where QRS complex meets ST segment
Where is the QT interval measured and what is a normal duration?
Beginning of QRS complex to end of T wave
Normal = 0.36- 0.44ms
The QT segment will increase as what parameter slows?
HR
With regular rhythm, how does the QT segment compare to R waves?
QT segment should be < 1/2 the distance between consecutive R waves
What provide an electrical “view” of the heart to help distinguish a focal problem?
Leads
What are the anterior leads?
V1-4
What are the lateral leads?
I, aVL, V5-6
What are the inferior leads?
II, III, aVF
Bipolar leads record difference in electrical potential between what?
Positive and negative electrode with 3rd electrode as a ground
What is postitive and negative with lead I?
RA neg, LA pos
What is postitive and negative with lead II?
RA neg, LL pos
What is postitive and negative with lead III?
LA neg, LL pos
What is the reference point for unipolar leads?
Center of the heart (as calculated by ECG machine)
What type of leads are enhanced by the ECG because waveforms produced by these leads are normally small?
Augmented limb leads
Augmented limb leads use the same electrodes as limb leads but only 1 is positive and the other two…?
Have no charge and serve as common ground
What electrode is positive with aVR and what view of the heart does it provide?
RA pos, views base of heart (atria and great vessels)
What electrode is positive with aVL and what view of the heart does it provide?
LA pos, views lateral wall of LV
What electrode is positive with aVF and what view of the heart does it provide?
LL pos, views inferior wall of LV
What leads are all positive electrodes and provide anterior and lateral views of the heart in a horizontal plane?
Precordial leads (V1-6)
Where is V1 placed?
4th ICS, right of sternum
Where is V2 placed?
4th ICS, left of sternum
Where is V3 placed?
Halfway between V2 and V4
Where is V4 placed?
5th ICS in MCL
Where is V5 placed?
Anterior axillary line, same horizontal plane as V4
Where is V6 placed?
Midaxillary lines, same horizontal plane as V4
Which leads are used for patient monitoring in the ED, telemetry, and ICU?
Modified chest leads
What do MCL1 and MCL6 provide and where are they placed?
Provide continuous cardiac monitoring, positive electrode placed in same position as precordial leads V1 or V6
What is normal sinus rhythm (NSR)?
Regular rhythm, rate 60-100 bpm
How do you determine regularity?
- Distance between consecutive P waves and consecutive QRS complexes should be the same (up to 1 square difference)
- R-R and P-P intervals are the same (if differ, then rhythm= irregular = abnormal)
What are the 3 methods for calculating regularity?
Caliper method, pen and paper method, counting small squares method (irregular if # is different)
How do you define “occasionally irregular”?
Mostly irregular but occasional areas of irregularity
How do you define “very irregular”?
Has many areas of irregularity
A wandering atrial pacemaker is defined how?
Slightly irregular
(pacemaker changes location from site to site and produces a slightly irregular rhythm)
(should look at appearance of P wave)
Paroxysmal tachycardia is defined as what with respect to regularity?
Sudden HR acceleration
(normal rate that suddenly accelerates to a rapid rate producing an irregular rhythm)
How do you define patterened irregularity?
Irregularity repeats in a cyclical fashion
Sinus dysrhythmia and 2nd degree AV block type 1 are examples of what?
Patterned irregularity
(sinus dysrhythmia = with inspiration increases, decreases with expiration)
Atrial fibrillation is an example of what type of regularity?
Totally irregular (no discernable pattern to irregularity)
Irregularity can also be seen in dysrhythmias with a varying ratio of what?
Atrial to ventricular conduction ratio
(P wave to QRS ratio)
What HR is bradycardia?
< 60
What HR is tachycardia?
> 100
If rhythm is found to be irregular, you should look at what? OR describe the irregular rhythm with what?
Look at most regular portion of ECG to determine underlying rate
OR
Describe irregular rhythms with HR range
How do you use the 6-second interval x 10 method to determine HR?
of QRS complexes in 6 seconds x 10 (not very accurate)
How do you use the large box estimate (300, 150, 100, 75, 60) to determine HR?
Find R wave located on/near bold line and count down along each subsequent bold line until next R wave → closest bold line = rate
When using the large-box method to determine HR, if 2nd R is not on a bold line, what should you do?
Determine what two #s it falls between and record HR as range
The large-box method for determining HR is less accurate for what type of rhythms?
Irregular rhythms
How can the large-box method for determining HR be made more precise?
Divide difference of 2 bold lines by 5 to determine how many “beats” each small box represents and subtract that from last bold line
What is the most accurate method for estimating HR but cannot be used with irregular rhythms?
1500 method
(count # of small squares b/w two consecutive R waves and divide 1500 by that #)
What method for measuring HR do you position the “start mark” on an R wave, then find the next consecutive R wave and where it lines up is the approximate HR?
Rate calculator
When evaluating P waves, an amplitude of > 2.5 suggests what?
Right atrial enlargement (RAE) = P pulmonale
When evaluating P waves, a width of > 0.10s suggests what?
Left atrial enlargement (LAE) = P mitrale
When might wide, notched or biphasic P waves be seen?
Increased left atrial pressure and left atrial dilation
In what lead are biphasic P waves normal?
V1
Variations in P waves are typically due to impulses arising from the atria but NOT where?
SA node
What is a premature atrial complex (PAC)?
Early beat
What will continually change in appearance in a wandering atrial pacemaker?
P wave
If the P wave appears “buried” in the T wave of the preceding beat (short P-P interval) and the T wave is peaked, noted or larger than normal, what pathology should you suspect?
Atrial tachycardia
When evaluating P waves, a “saw tooth pattern” is indicative of what?
Flutter waves (when atria fire @ rate 250-250 bpm)
When evaluating an EKG strip you note absence of discernable P waves and instead note a chaotic looking baseline that preceeds the QRS complex. What are you suspicious for?
Fibrillatory waves (when atria fired from many sites @ rate > 350 bpm)
Inverted P waves produced by retrograde depolarization of atria (lower RA near AV node, LA, AV junction), can precede, occur during or follow a QRS complex. What is this pattern associated with?
Dysrhythmias that originate from AV junction
If the P wave > QRS complex, what does this indicate?
Impulse was initiated in SA node/atria but was blocked and didn’t reach the ventricles
(P wave to QRS ratio should be 1:1)
When evaluating the QRS complex, there can only be 1 what? But more than 1 what?
Only 1 Q wave but more than 1 R or S wave
(R’ or S’ = R-prime or S-prime)
When should a lowercase r or s be used when evaluating the QRS complex?
If R or S wave is small
How is the QRS complex measured?
- Starting point = where 1st wave moves away from baseline
- Ending point where last wave flattens (joint point)
- Should include entire S but shouldn’t overlap into ST segment/T wave
Abnormal QRS complexes are typically produced by what?
Abnormal depolarization of ventricles
(SA node, atopic pacemakers in atria, AV junction, BB, purkinje network, ventricular myocardium)
What are the possible causes of a tall QRS?
Hypertrophy of one or both ventricles, ABN pacemaker, aberrantly conducted beat
What will the appearance of the QRS complex be with obesity, pericardial effusion, or hypothyroidism?
Low voltage QRS
What is often the result of an intraventricular conduction defect (typically a result of LBBB)?
Wide-bizarre QRS (of supraventricular origin)
What is defined as the following?
Electrical impulses reach the BB while it is still refractory after conducting a previous electrical impulse
(impulse travels down the unaffected BB first, follow by the other = wider QRS complex)
Aberrant conduction
When is a PR interval considered abnormal?
Shorter, longer, absent or varied
How will the PR interval appear when the impulse originates in atria close to or in AV junction or when impulses arise from SV site but travel through ABN accessory pathway to ventricles (faster pathway)?
Shorter (<0.12 s)
The following leads to what?
Impulses arise from SV site but travel through ABN accessory pathway to ventricles (faster pathway)
Pre-excitation (premature ventricular depolarization)
Travel of an impulse through an what abnormal accessory pathway may lead to a shorter PR interval?
Bundle of Kent (Delta wave)
Delay in impulse conduction through AV node (ex. 1st degree AV block) will result in what change in the PR interval?
Longer
The following will produce what PR interval?
Wandering atrial pacemaker (pacemaker site moves from beat to beat)
Varying
The following will produce what PR interval?
2nd degree AV block, type 1
Varying
(PR intervals are progressively longer until QRS complex is dropped and then cycle repeats)
The following will produce what PR interval?
3rd degree AV heart block (atria and ventricles are beating independently of eachother)
Varying
The following will produce what PR interval?
Atrial flutter, atrial fibrillation and ventricular dysrhythmias
Absent
