Lecture 7 Flashcards
Define stroke and kinetic work
Stroke work:
- Contracting and pumping blood into aorta (and pulmonary artery)
- Area represented by pressure volume loop
Kinetic Work:
-Accelerating the blood through the valves into aorta (and pulmonary arteries)
Calculate stroke work
Mean arterial Pressure x Stroke volume
(MAP= 1/3(SBP-DBP)+DBP)
MAP = (2xDBP)+SBP/3
How is preload changed in the body?
-Altering end diastolic volume (Direct relationship w preload)
(Venoconstriction/venodilation or altering blood volume –> Alters VR –> Alters EDV)
(Vasoconstriction = direct = increase VR = Inc EDV, vasodilation = inverse = decrease VR = dec EDV)
How is afterload changed in the body?
-Altering aortic pressure of changing total peripheral resistance
How is contractility changed in the body?
-Altering sympathetic activity, or by giving drugs which alter inotropic state
Whats the relationship between preload and stroke volume?
Direct Relationship
Increasing preload increasing stroke volume
What’s the relationship between contractility and stroke volume?
Direct Relationship
Increasing contractility increasing stroke volume
What’s the relationship between afterload and stroke volume
Inverse Relationship
Increasing afterload decreases stroke volume
(Heart can usually compensate for this)
What effects does exercise have on pressure volume loop?
1) Increases sympathetic activity
- Increases venomotor tone –> increases venous return –> Increases end diastolic volume–> increases preload –> increases stroke volume
2) Increases sympathetic activity –> Increases contractility –> Increases stroke volume
When should you hear sound in a normal heart?
When valves are closing
Never when valves are opening
What does the “Lub” sound come from
S1: Closure of A-V valves (Mitral and tricuspid)
-Bottom right corner of Pressure volume loop
What does the “Dub” sound come from
S2: Closure of semilunar valves (Aortic and pulmonary)
-Top left corner of the pressure volume loop
Splitting of S2 heart sound
-Aortic closes before the pulmonary valve during inspiration
Physiological = normal - inspiration
Pathological = Conduction defects
S1 Splitting
Pathological
-Occurs in conduction defects on one side of the heart
S3 Pathological heart sounds
-Rush of blood into ventricles from atria can create a sound
S4 Pathological heart sounds
-Stiff ventricles can make a sound
What’s a Heart murmur and how does it happen
- Abnormal sounds heard during Auscultation
- Caused by faulty valves –> turbulent flow = noise
1) Stenosis
- Opened valve is narrowed
- Higher pressures needed to push blood through
2) Incompetence
- Closed valve is leaky –> Regurgitation
What causes a systolic murmur
1) Aortic stenosis
2) Mitral incompetence
What causes a diastolic murmur
1) Mitral stenosis
2) Aortic incompetence
Describe aortic stenosis and it effects
- Systolic murmur
- Difficult to eject blood through aortic valve (Narrow high resistance valve)
- Decrease stroke volume
- Increase end-systolic volume
Buzzword: “Crescendo Descendo”
Describe Mitral Incompetence and its effects
- Systolic murmur
- Ventricular systole causes blood to regurgitate back into Left atrium in murmur that extends throughout systole
- Increase stroke volume
- Decrease end-systolic volume
- Increase end-diastolic volume
Describe Aortic incompetence and its effects
- Diastolic murmur
- Aortic valves fail to close properly left ventricle pressure rises as blood regurgitates from aorta into left ventricle
- Increase stroke volume
- Increase end-diastolic volume
Describe Mitral stenosis and its effects
- Diastolic murmur
- Turbulent flow across mitral/tricuspid valve
- LA pressure is elevated
- Decrease stroke volume
- Decrease end-diastolic volume
Buzzword: “Open snap”
