Clin Phys Week 7 E Flashcards
What is the function of the heart
Deliver nutrients to the cells
Deliver waste to the excretory organs
What are the chordae tendineae?
A cord which the AV valves to papillary muscles on the ventricular floor.
Describe semilunar valve function
As the ventricles contact and inter ventricular pressure rises, blood is pushed up against the semilunar valves, forcing them to open. As the ventricles relax and inter ventricular pressure drops, blood flows back from the arteries, filling the cusps of the semilunar valves and forcing them to close to prevent further back flow.
What is systole?
Contraction / ejection of blood
What is diastole?
Relaxation / filling
What is typical end diastolic volume?
approx 130 mls
What is typical stroke volume?
approx 70 mls
What is end systolic volume?
The amount left in heart after ventricular contraction.
What are the heart valves made of?
Doubled over endocardium
What is the systolic and end diastolic range of the left ventricle?
Systolic: 90-140mm Hg
End diastolic: 4-12mm Hg
What is the systolic and end diastolic range of the right ventricle?
Systolic: 15-28mm Hg
End diastolic: 0-8mm Hg
What is the systolic range for the aorta?
96-140mm Hg
What is the diastolic range for the aorta?
60-90mm Hg
What does the heart sound S1 represent?
It indicates the beginning of systole and is heard as a “LUBB” sound. Best heart at the apex and is generally the loudest heart sound.
What does the heart sound S2 represent?
It represents the end of systole and is heard as a “DUBB” sound.
How many heart sound contribute to the S2? if more than one, what are they?
2 = A2 and P2
A2 = aortic valve closing
P2 = pulmonary valve closing.
Under what circumstances is the P2 sound occurring later than the A2 sound?
During inspiration (the venous return from the lungs is reduced as there is more space in the lung cavity so the pressure on the pulmonary semilunar valve is slightly less than the aorta, so it closes slightly later)
What does the heart sound S3 represent? Is it easy to hear?
The distention of the ventricular wall (early diastole where blood is rushing into the ventricles from the atria). Very difficult to hear, usually can only be hear with an ultrasound.
What does the heart sound S4 represent?
Atrial contraction, vibration of ventricular walls, valves and papillae.
List one physiological and one pathological reason you may hear an S3 sound?
Physiological: Children and adults over 40. Due to very rapid early diastolic filling.
Pathological: Due to exaggerated early diastolic filling into a ventricle. This may occur where there is heart failure or valvular regurgitation.
Is an S4 sound always pathological?
Yes
What is a pathological reason for an S4 sound?
Due to rapid flow during atrial contraction into a ventricle with reduced compliance e.g. ventricular hypertrophy, myocardial ischaemia
What is a heart murmur?
An extra heart sound made by turbulent blood flow.
What causes heart murmurs?
A valve is thickened and fails to open properly.A valve fails to shut and leaks.There is an abnormal communication between the heart chambers due to a congenital abnormality (atrial septal defect) or acquired abnormality (post infarct ventricular septal defect)
What is an innocent murmur?
A systolic flow murmur typically heard in the pulmonary area of children and young adults. It is possibly caused by vigorous ventricular contraction.
What are the 5 characterisations of heart murmurs?
- Timing and duration - systolic/diastolic
- Intensity - Graded 1-6 (6 heard without stethoscope)
- Where is it heard best - location? e.g. apex
- Where does it radiate - neck, back axilla?
- What does it sound like - high pitched, raspy etc
What is the rate of atrial systole?
0.1 seconds
What is the rate of ventricular systole?
0.3 seconds
What long is the quiescent period of heart contraction?
0.4 seconds
What is the total time for one heart contraction?
0.8 seconds
What is cardiac output?
The amount ejected by each ventricle in 1 minute
How is cardiac output calculated?
Heart rate x stroke volume
What is the average cardiac output at rest?
4-6L/min
What is the maximum cardiac output during exercise of both normal people and world class athletes?
Normal people - 21L/min
Athletes - 35L/min
What is the cardiac reserve?
The difference between maximum and resting cardiac output
What factors of cardiac performance is stroke volume governed by?
Preload
Afterload
Contractility
What is preload? How does it affect stroke volume?
Left ventricular left diastolic volume i.e. amount of stretch of left ventricle = volume overload
Therefore: increased preload = increased stroke volume
What is afterload? How does it affect stroke volume?
Total peripheral resistance = pressure overload
Therefore: increased afterload = decreased stroke volume
What is contractility? How does it affect stroke volume?
Capacity of myocardium to respond to preload and afterload.
Therefore: increased contractility = increased stroke volume
What is the frank starling mechanism?
An intrinsic regulatory mechanism that relates to the cardiac length contractility curve. It is determined by venous return and states that the greater the myocardiocyte stretch the greater the strength of contraction.
Factors that increase contractility are _______ agents. Give 3 examples.
Positive inotropic agents. eg. hypercalcemia, catecholamines, glucagon
Factors that decrease contractility are ______ agents. Give 3 examples.
Negative inotropic agents.eg. Hyperkalemia, hypocalcemia, hypoxia
