Cardiac Cycle Flashcards
Cardiac cycle
• Sequence of events that occur when the heart beats
• 1 cardiac cycle = ____
1 diastole and 1 systole
Sino-atrial (SA) node- “ Natural/anatomical pacemaker”
- Location- upper part of the wall of RA
- Function- Makes the ____ contract
- Controls the ____
atria
heart beat
Atrioventricular (AV) nodes
• Location: lower part of the atrium between Atrium and ventricle
• Function:
• ____ down impulses entering the ventricles and segments (will explain later)
• ensure proper emptying of the atrium before ventricular contractio
- you can see this on ____
slows
ECG/EKG
Electrocardiogram (EKG/ECG)
- Electrocardiogram is a tool that measures and records electrical activity of heart by placing ____ on the skin
- standard is ____ limb leads system, which is made of ____ electrodes
◦ Pre-caudal limbs - placed on the chest (6 of them)
‣ V1 - ____ intercostal space, ____ side of the sternum
‣ V2 - ____ intercostal space, ____ side of the sternum
‣ V4 - ____ intercostal space, ____ line
‣ V3 - in between ____
‣ V5 - ____ intercostal space, in the ____ line
‣ V6 - in the ____ line
‣ V4, V5, and V6 are placed on the same ____
◦ Limb leads - placed on ____ (right, left hands and feet) of the body
electrodes
12
10
4th right 4th left 5th mid-clavicular line V2 and V4 5th anterior axillary mix-axillary horizontal plane extremities
Heart sounds
S1
occurs during: ____
associated with: closure of ____ valves
S2
occurs during: ____
associated with: closure of ____ valves
S3
occurs during: ____
associated with: normal in ____ ; in adults, associated with ventircular ____ (i.e. ventircular systolic failure)
S4
occurs during: ____
associated with: stiff, ____ compliant ventricle (i.e. ventricular ____ ; ishcemic ventricle)
isovolumetric contraction
mitral/tricuspid
isovolumetric relaxation
aortic/pulmonic
early ventricular filling
children
dilation
atrial contraction
low
hypertrophy
- Waves
- Deflection (+/-) from baseline
- Indicator of electrical event
• P wave = ____. End of Diastole
• QRS complex = ____ Systole phase
• Interval between P and Q = AV node causes delay such that you have a complete
emptying of the atrium and you don’t have contraction of ventricle
• T wave = ____
• Every time you have a deflection (a wave) from the baseline it’s showing electrical
activities
atrial contraction/depolarization
ventricular contraction
ventricular repolarization
Segment
• A line that connects 2 ____ together without including the ____.
• Difference between segment and interval
◦ Segment connects two waves without including waves
◦ (She does not what interval is but I am assuming interval
includes waves)
waves
waves
ECG
- ST segment:
- Represents the beginning of ____
- Usually ____ (isoelectric). May have up to ____mm variation
- Mild ST elevations may be noted in ____ individuals
- Mild normal ST segment depression can be noted following physical exertion
- ____,
• Huge deflection in ST segment can mean ____
ventircular repolarization flat 0.5 healthy myocardial ischemia myocardial infarction
Interval
• The time between 2 ____ events
• Includes a ____ and 1 or 2 waves
• RR interval ( determines heart rate). Is constant in ____.
• Only difference between segment and interval
◦ Segment is between two waves not including the wave
◦ Interval is time between two electrical events but including the ____ also
◦ Why is this important?
‣ Reading EKG involves intervals. For you to be able to calculate heart beat (what we have to get used to when we start clinics)
• We talked about heart rate and pulse last year
◦ Where do I take my pulse from when I am in the dental clinic
‣ ____ pulse from your wrist
◦ You take the radial pulse. How do I know if it’s regular or irregular?
‣ You look at strength (is it full bounding pulse or shallow?). Is it regular. So You time it right. Does it have specific rhythm to it or does it not
◦ So in the same way, you have your heart rate using your radial pulse, which is basically an estimate, you are able to see that on the EKG or ECG
• You can tell your heart rate by looking at ECG report
electrical events segment sinus rhythm waves radial
Interval (contd) • PR interval: • \_\_\_\_ (p wave) • propagation of electrical impulses through AV node (physiological delay) • Normal range- \_\_\_\_ s • Prolonged in \_\_\_\_ nerve block
• When you see EKG, how do I know what is normal and what is not
• Two needs I need to pay attention when looking at EKG
◦ Do I have P wave, atrial depolarization, ____ each complex (sometimes P wave is missing or look abnormal)
◦ Is P wave ____. Sometime you see p wave going downwards ( ) or going too high
◦ You want to compare your P wave to ____. Do I have smaller deflection on my P wave or is it
higher than T wave
atrial depolarization 0.12-0.20 1st degree preceding upright T wave
PR interval • Shortened in pre-excitation syndromes: - wolff parkinson white syndrome -- PR interval is \_\_\_\_ -- \_\_\_\_ is wide
- lown ganong levine syndrome
- PR interval is ____
shortened
QRS complex
shortened
QT interval
• From the beginning of ____ (QRS complex) to end of ____ ( T wave)
- Prolonged:
- multiple ____
- electrolye abnormalities ____, hypomagnesemia and ____)
- certain disease states (i.e. ____).
ventricular depolarization ventricular repolarization medications hypocalcemia hypokalemia intracranical hemorrhage
How to read an ECG
• Each EKGs is read using graph sheet
◦ For the graph sheets, you have to pay attention to how many seconds. ‘
‣ Is it 10 second strip, 6 second strip or 3 second strip
◦ How do I know what’s the timing of the strip
• Each small square, ____ seconds
• Each large square (made up of 5 small boxes), ____ seconds
◦ Ex) If I have 3 seconds strip, 15 large boxes make up ____ seconds (things you need to pay attention)
• Don’t assume that all strips are the same. Especially when you don’t have regular RR interval
◦ To measure RR interval, nurses get a caliper and place it on the tip of first RR interval and place it as you go along to see if you have same interval in between
‣ If it has same interval in between RR intervals, there are different ways to calculate your heart rate from it
‣ If, however, your RR intervals aren’t the same, there is another way to calculate RR interval
‣ (She is going to explain both ways)
0.04
2
4
How to read an ECG:
Heart rate:
• Count the number of ____ between each R-R interval. (accurate when R-R interval is regular) or 60/# of seconds)
• 60/0.2 sec ( 1 large box)= 300 beats
• She does not know what constant represents. There if constant is it’s 60. Maybe it represents 60 seconds, if you have regular interval (in the next slide, she says 60 represents 60 seconds)
• But there is constant of 60, that you use to divide number of boxes (number of seconds) that gives you what heart rate is
• When you have regular RR interval, 60/number of seconds (number of ____) gives you heart rate
◦ Ex) you have 4 boxes in between regular RR interval, you divide 60 by 0.8 seconds (0.2 seconds x 4 boxes = 0.8 seconds), 75 is the heart rate
• When you have regular interval, you divide constant 60 by boxes
boxes
large boxes
How to read an ECG
Using a 10 second strip (50 large boxes =10/0.2 sec),
• Count the number of ____
• Multiply # QRS complexes by 6 (10s) X 6 = 60 seconds.
• Accurate for irregular R-R intervals (e.g. ____)
• Using a 6 sec strip (30 large boxes), count # of ____ X 10.
Other way to calculate heart rate is very easy but with that, you have to know what kind of strip you
have.
Do I have 6 sec strip or 10 sec strip. Very important
◦ Ex) if you have 10 sec strip, you multiply number of QRS complexes by ____ to get to 60 seconds ◦ Ex) if you have 6 sec strip, you multiply number of QRS complexes by ____
QRS complex
A fib
QRS complex
6
10
