Flashcards in Module 6: Cardiovascular Deck (237)
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CARDIAC CYCLE: PHASES
1. Period of Atrial Systole/Pre-systole
2. Isovolumic contraction period
3. Rapid/Maximum Ejection
4. Reduced Ejection
5. Protodiastole
6. Isovolumic Relaxation
7. Rapid Filling
8. Reduced filling/Diastasis
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TIMING (Events on the 2 sides of the heart are similar
but somewhat asynchronous.)
- Right atrial systole precedes left atrial systole
- Contraction of right ventricle starts after that of left ventricle
- Right ventricle ejection begins before the left. Because pulmonary pressure is lower than aortic pressure.
- During inspiration, aortic valve closes slightly before the pulmonary valve. Due to the lower impedance and distensibility of the pulmonary vascular bed
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- Normally between 0-4 mmHg
- PEAKS
A Wave - A TRIAL CONTRACTION
C Wave - C ONRACTION OF VENTRICLES – OVERBULGING OF AV VALVES
V Wave – V ENOUS BLOOD GOING TO THE ATRIUM
ATRIAL PRESSURE PULSE
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We plot this curve at 80 mm Hg level because aortic pressure is always high. Remember that:
1. Blood Vessels are always in a condition or state of being slightly filled with blood
2. Aorta made up of elastic tissues therefore can be stretched within limits
3. If remove stretch --- recoils
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The rise and fall of Aortic Pressure Pulse reflects the balance between:
1. The volume of blood entering the aorta from the heart
2. The volume of blood leaving the aorta and draining into the periphery, called ‘PERIPHERAL RUN-OFF”
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- When ejection exceeds run-off, Aortic Pressure increases
- When run-off exceeds ejection, Aortic Pressure __
goes down or decreases
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- Occurs during the distal third of diastole
- Preceded by p-wave in the ECG
- Slight increase in atrial pressure, ventricular pressure and ventricular volume
- NOT essential for ventricular filling
Atrial Contraction
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- Preceded by QRS complex in the ECG
- First Heart Sound (S1) is heard
- Increase in ventricular pressure BUT ventricular volume remains the same
- Ventricular Pressure
Isovolumic Contraction
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- Ventricular Pressure > Aortic Pressure
**Semilunar valves open
- Rapid Increase in Ventricular Pressure, Decrease in Ventricular Volume
Rapid Ventricular Ejection
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- T-wave occurs in the ECG
- Decrease in ventricular pressure, decrease in ventricular volume
Reduced Ventricular Ejection
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- Ventricular Pressure Atrial Pressure
**AV valves are still closed
- Decrease in ventricular pressure BUT ventricular volume remains the same
- Second Heart Sound Heard (S2)
Isovolumic Relaxation
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- Ventricular Pressure
Rapid Ventricular Filling
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- Reduced increase in ventricular volume
- Middle 1/3 of diastole
Reduced Ventricular Filling
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- are vibrations caused by turbulent flow of blood and contraction of ventricular muscle, which are transmitted through the supporting tissues and to the chest wall
HEART SOUNDS
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- associated with the closure of the AV valves at the onset of systole and isovolumetric ventricular contraction
- Soft closure
- slightly prolonged, soft, low-pitched
- duration of 0.15 seconds
- splitting when mitral valve closes before tricuspid valve
- heard best at MITRAL AND TRICUSPID AREA
FIRST HEART SOUND (S1)– “LUB”
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- occurs at the end of systole as the pulmonary and aortic valves closed
- Snapping closure
- shorter, louder, high-pitched
- duration of 0.12 secs
- inspiration causes splitting of 2nd HS because aortic valve closes slightly before pulmonary valve
- heard best at PULMONIC AND AORTIC AREA
SECOND HEART SOUND (S2)–“DUP”
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- associated with the rapid in rush of blood during rapid ventricular filling
- soft, low-pitched, duration of 0.1 sec
- recordable in from 26 to 85% of normal person
- maybe present 0.04 to 0.12 seconds after the onset of the second sound
- is most common in the presence of mitral stenosis
- normal in children
THIRD HEART SOUND (S3)
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- associated with the atrial systole / contraction of the atrium – filling of ventricle
- recorded in 25% of normal person
- sometimes heard immediately before 1st heart sound
- not audible in normal adults
- audible in persons with left ventricular hypertrophy associated with hypertension
- present also when atrial pressure is high
FOURTH HEART SOUND (S4)
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- are abnormal heart sounds which can be produced by:
1. blood flowing rapidly in the usual direction through an abnormally narrowed valve (STENOSIS)
2. blood flowing backward through a damaged, leaky valve (INSUFFICIENCY)
3. blood flowing between the 2 atria or 2 ventricles through a small hole in the wall separating them.
MURMURS
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A murmur heard throughout systole suggest __
stenotic semilunar valve or insufficient AV valve
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A murmur heard during diastole suggests __
stenotic AV valve or an insufficient semilunar valve
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Occasionally, a 3rd heart sound is heard which give rise to a triple beat that resembles the hoof beats of a galloping horse, called __. Most frequently associated with congestive heart failure.
GALLOP RHYTHM
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The function of the ventricles is described by three parameters
1. Stroke volume
2. Ejection Fraction
3. Cardiac output
CARDIODYNAMICS
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- The volume of blood ejected on one ventricular contraction or the volume ejected on one beat (ml/beat)
- The difference between the volume of blood in the ventricle before each ejection and the volume remaining in the ventricle after each ejection
- SV = EDV – ESV
STROKE VOLUME
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- The fraction (percent) of the EDV that is ejected in each stroke volume
- The ratio of SV to EDV and normally 60% to 65%
- Expressed by the ff equation:
EF = SV/EDV
- A valuable index of ventricular function (contractility)
- Increases in EF reflects an increase in contractility
- Decreases in EF reflects a decrease in contractility
EJECTION FRACTION
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When strength of contraction increases without an increase in fiber length, more blood in the ventricle is expelled, thus, __
EF increases and ESV decreases
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- The total volume of blood ejected per minute
- CO (ml/min) = SV (ml/beat) x HR (beats/min)
- Direct proportionality true within limits
- If HR remains constant, CO increases in proportion to Stroke Volume (SV). Thus factors that increases SV can increase CO
- If SV remains constant, CO increase in proportion to HR up to about 180 beats/min
*HR and SV do not always change in the same direction
Cardiac Output
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Cardiac Output
CO = Stroke Volume (EDV-ESV) x Heart Rate
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Factors that affect cardiac output: Heart Rate (100 beats/min) – 70 beats/min
- respiration
- body temp.
- electrolyte concentration
- exercise
- emotions
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