Fall ECG Flashcards
Describe the little block method of calculating heart rate.
Count the little blocks between consecutive qRS complexes, then divide 1500 by that number. e.g. 15 little blocks =
1500/15=100bpm
Explain the “memory” method of calculating heart rate
Count the number of big blocks between QRS complexes then apply to memorized chart:
1: 300
2: 150
3: 100
4: 75
5: 60
6: 50
7: 43
8: 37
9: 33
10: 30
Describe the 6second strip method of calculating heart rate.
Count the # of QRS complexes in a 6 sec strip then multiply by 10
Describe the Bi-polar leads
3 Bi-polar leads (limb leads)(positive and negative pole make up lead)
Lead I: right arm (-) to left arm (+)
Lead II: right arm (-) to left leg (+)
Lead III: left arm (-) to left leg (+)
Explain and list augmented (unipolar) leads
Augmented leads are made up of a single (+) electrode, and are augmented (amplified) as the signal is rather weak.
aVR: right arm (+)
aVL: left arm (+)
aVF: left foot (+)
Describe and define percordial leads
Commonly known as “chest leads” they are 6 additional electrodes which give 6 additional leads (pictures) of the heart on a horizontal plane. They are named numerically: V1 through V6
What is the most common lead for continuous monitoring? Why?
Lead II. It is best positioned (below the heart looking up at it) to measure the electrical activity of the heart in the direction it is traveling.
How much time does 1 small box represent on ECG paper?
0.04 seconds
How much time does 1 large box represent on ECG paper?
0.2 seconds
How many large boxes, on ECG graph paper, represent 1 second?
5
The mostly flat line which runs through an ECG strip is called?
The isoelectric line
What is the PR interval (PRI)
What is the normal length of a PRI?
Beginning of the P wave to the beginning of QRS.
0.12-0.2 seconds (3-5 small boxes)
Represents beginning of the atrial depolarization through the pause at the av node
What is the PR segment?
End of the P wave to the beginning of the QRS complex.
What does the QRS complex represent?
Ventricular depolarization
What is the normal time (length) of the Qrs complex?
Less than or equal to: 0.12 seconds
Less than or equal to: 3 small boxes
What does the QT interval represent?
Beginning of the QRS complex to the end of the T-wave
What is the ST segment? J-point?
The time from the end of the QRS complex to the beginning of the T-wave.
J-point is the end of the QRS complex (sometimes difficult to pinpoint)
What is the refractory period?
The state of un responsiveness following depolarization.
What are the 5 steps of analyzing a rhythm strip?
- Rhythm (regularity): R-R & P-P
- Rate
- P-waves (Present? Upright? Look alike? Preceding each QRS?
QRS following every Pwave? - PR intervals: 3-5 boxes
- QRS: less than .12 (3 small boxes)
List the 3 criteria that must be met to determine a rhythm originates in the sinus node.
- Upright matching Pwaves in Lead II followed by a QRS
- PR intervals constant
- Heart rate less than or equal to 160 at rest
What are the 3 tissue layers of the heart?
endocardium
myocardium
epicardium (visceral pericardium)
what is cardiac tamponade
A condition in which an accumulation of fluid in the pericardial cavity prevents proper filling of the ventricles.
Name 4 causes of stiff pericardium
Infection
Trauma
Radiation
Idiopathic
What is the cardiac cycle
Time from the end of one cardiac contraction to the next
What is diastole
period of time when heart is relaxed and filling and coronary perfusion occurs
What is systole
Period of time when heart is contracting
What is the atrial kick
Amount of blood added to ventricular end diastolic volume with atrial contraction
What is preload
Pressure within ventricles at the end of diastole, commonly called end diastolic volume.
Starlings law of the heart
The more the myocardium is stretched, the more forceful the subsequent contraction will be (up to a certain point)
What is after load
The resistance against which the heart must pump
What is stroke volume?
The amount of blood ejected by one ventricle in a single contraction
What is cardiac output?
The amount of blood pumped by the heart in one minute
What is ejection fraction
Stroke volume over end diastolic volume
Inotropy
Pertaining to cardiac contractile force
Chronotropy
Pertaining to heart rate
Dromotropy
Pertaining to the speed of nervous impulse conduction
Sympathetic neurotransmitter
Norepinephrine
Parasympathetic neurotransmitter
Acetylcholine
Sympathetic primary receptors
Alpha & Beta
Location of alpha 1 & beta 1 receptors
Alpha 1: peripheral blood vessels - promotes constriction
Beta 1: heart - increases rate, contractility, impulse conduction
Location of beta 2 receptors?
Located mostly in lungs - promotes bronchodilation
Parasympathetic principal receptors
Cholinergic
Two types of cholinergic receptors and location
Muscarinic: smooth muscle and cardiac muscle
Nicotinic: neuromuscular junctions and autonomic ganglia
Name the 4 qualities all cardiac cells have in common
Excitability
Conductivity
Automaticity
Contractility
What is syncytium?
Group of cardiac cells that physiologically act as a unit.
What are the 2 syncytial within the heart?
Atria
Ventricles
Name the 3 intrinsic pacemakers and their rate
SA = 60-100
AV = 40-60
Purkinje system = less than 40
What are 2 examples of pathological q waves
Equal to or greater than .03 sec.
and/or
Equal to or greater than 1/3 the height of the r wave
Name 10 etiology of sinus tachy
Exercise Pain Hypoxia Shock Drugs Agitation Caffeine Nicotine Fever Hypovolemia
List 4 etiology for bradycardia
Damage to sa node
Hypoxemia
Increased parasympathetic tone
Conditioned athletes
What are the 2 types of sinus arrhythmia
Respiratory (regularly irregular)
Non-respiratory (irregular random pattern)
