Module 1 Basics Flashcards
Indications to Order an ECG (5 criteria)
1) unexplained syncope, near syncope, or episodic dizziness without obvious cause
2) Unexplained recurrent palpitation
3) Episodic SOB, angina or fatigue that is not otherwise explained
4) Neurologic events when transient atrial fibrillation or flutter is suspected (looking for strokes)
5) explained syncope, near syncope, episodic dizziness or palpitation in whom probable cause other than an arrhythmia has been identified but in whom symptoms persist despite treatment of this other cause
Depolarization - Define
At rest, the interior of the myocardium is negatively charged
Stimulation of the myocardium by the electrical conduction system
“Wave” of depolarization stimulates the heart’s myocytes causing them to become positive and contract
DEPOLARIZATION = POSITIVE
Repolarization - Define
Myocytes return to the negative resting state
REPOLARIZATION = NEGATIVE
Underlying physiology of the ECG Electrodes (hint: what do the waves mean on the ECG in relation to the electrodes)
As a wave of depolarization (POSITIVE CHARGE) moves within the cardiac myocytes, there is a positive (upward) deflection on the ECG
Sinoatrial (SA) Node (function and location)
Known as the “pacemaker” which sets the tone for the electrical impulses of the heart
Located in the right atrium
Automatically generates a positive wave of depolarization within the right atrium
Normal Sinus Rhythm
Pacing activity; pacemaker in charge (SA Node)
P wave is present; rate is 60-100BPM
Define P wave and what does it represent in relation to the physical activity by the heart
Represents the wave of depolarization from the SA node through both atria
Represents ATRIAL DEPOLARIZATION and ATRIAL CONTRACTION
Atrioventricular (AV) Node (function and what is it known as)
“Gatekeeper” in the electrical conduction pathway between the ATRIA and VENTRICLES
Electrical depolarization SLOWS down here
Electrical delay allows for blood to flow from the atria into the ventricles (heart wants the blood to fill up in the ventricles from the atria).
Describe the ventricular Conduction System Pathway in a normal functioning heart
SA Node -> AV node -> Bundle of His -> left and right bundle branch (Purkinje Fibers)-> left and right ventricle contract
Downward deflection on ECG represents what?
Electrical activity happening away from the leads (NEGATIVE)
What does the QRS Complex represent?
Ventricular Depolarization and Ventricular Contraction
What does the T Wave represent?
Ventricular repolarization
Difference between segments and intervals
Segments do not include waves - they are isoelectric
Intervals include waves
PR Interval
time between the beginning of atrial contraction until immediately before the ventricles contract
time the electrical conduction begins at the SA node until the impulse is sent to the AV node
PR Segment
Time from the END of atrial contraction to the BEGINNING of ventricular contraction
PR Interval - P wave included
PR Segment - NO wave included
ST Segment
Horizontal segment following the QRS complex and before the T wave
ST segment represents a portion of Ventricular Repolarization
QT Interval
Included the QRS complex, ST segment and T Wave
Represents the ENTIRE DURATION of VENTRICULAR CONTRACTION
1x1 and 5x5 boxes on ECG (What are the mV and seconds for both types of boxes)
X-Axis is TIME (seconds)
Y-Axis is VOLTAGE (mV)
Small boxes: 0.1 mV and 0.04s
Big boxes: 0.5 mV and 0.2s
Measuring Height (aka Amplitude)
Measured from the baseline in millivolts and is a measure of electrical voltage
Height is known as AMPLITUDE of the wave
Normal range for QRS Complex. If it is greater than these values, what is it called?
Normal QRS Complex:
1 to <3 small boxes or 0.04-0.11
If it is greater, it is called “widened QRS complex” (3 small boxes or 0.12 or greater)
T wave Height (normally)
Height is usually less than 2/3 the height of the preceding R wave
Normal Range for PR Interval
Between 3-5 small boxes or 0.12-0.2s
Normal range for QT interval (should not be on test since he never had us do these on the homework assignments)
Less than 1/2 the R-R distance
A standard ECG is composed of how many leads? What is the overall purpose?
4 LIMB electrodes and 6 CHEST electrodes for a total of 10 electrodes place
Overall purpose of these 10 electrodes is to gather different viewpoints of the same cardiac activity even (12 leads generated on machine)
Placement of the 4 limb electrodes
LA, LL, RA, RL
V1 Chest Lead
Right of sternum, 4th ICS
V2 Chest Lead
Left of sternum, 4th ICS
V3 Chest Lead
Midway between V2 and V4
V4 Chest Lead
5th ICS Mid Clavicular Line (MCL)
V5 Chest Lead
5th ICS along the AAL (anterior axillary line)
V6 Chest Lead
5th ICS MAL (mid-axillary line)
Systemic Approach to ECG Interpretation ( 7 Steps)
Look at in order:
1) Rate
2) Rhythm
3) Axis
4) Waves, Intervals, Segments
5) Clinical Correlation
6) Compare to prior ECGs
7) Watch out for bad data
What is the normal range for the rate of the SA node pace of the heart?
60-100 BPM
Interpret/define “Normal Sinus Rhythm” when describing an ECG
“Sinus” means the heartbeat is originating from the SA Node
A normal sinus rhythm has a P wave preceding every QRS complex
Rate is 60-100BPM
Sinus Bradycardia (what is the rate?)
SA node paces the heart at a rate slower than 60 BPM
P waves are present
Sinus Tachycardia
SA node is pacing the heart at a rate greater than 100 BPM
P waves are present
What are the two methods for determining the RATE?
Counting Method
6 Second Method
Counting Method
Find an R wave that peaks on a heavy black line (start line)
Count off each thick line after the start line
Where the next R wave falls determines the rate
What are the BPM intervals for the counting method when determining rate?
300 150 100 75 60 50
What is the 6 Second Method helpful for? What about the counting method?
6 Second Method is helpful when the rate is Bradycardic or Irregular
Counting method for regular rhythms
Honestly, you can use both, you just need the ticks on the strip for the 6 second method
6 Second Method
Find two consecutive 3 second intervals to give you a 6 second strip. The tick marks at the top of the ECG paper indicate a 3 second interval
Count the number of QRS complexes in this second strip
Multiply the number of QRS complexes in the 6 second strip by 10 to give you the rate
