Cardiovascular anatomy 2 Flashcards
Wall tension equation
Wall tension = pressure x radius
Wall stress equation
Wall stress = pressure x radius / 2x wall thickness
Ejection fraction equation
EF = SV / EDV = (EDV - ESV) / EDV
What is LV ejection fraction an index of?
Left ventricular ejection fraction is an index of ventricular contractility
EF AKA
Ejection Fraction
EF in systolic HF
EF is decreased in systolic HF However, EF is normal in HF with preserved ejection fraction
Starling’s law
Force of contraction is proportional to end-diastolic length of cardiac muscle fiber (preload) The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction (the end diastolic volume), when all other factors remain constant.
Factors that Increase contractility
Catecholeamines Positive ionotropes (e.g. digoxin)
Factors that decrease contractility
Loss of myocardium (e.g. MI) B-blockers (acutely) Non-dihydropyridine Ca channel blockers Dilated cardiomyopathy
Resistance equation
R = ΔP/Q = 8η x L / πr4
Flow equation
Q = ΔP/R
Pressure equation
ΔP = Q x R
Volumetric flow rate equation
Q = flow velocity (v) x cross-sectional area (A)
Resistance in series
R = R1 + R2 + R3 •••
Resistance in parallel
R = 1/R1 + 1/R2 + 1/R3•••
What vessels have the highest cross-sectional area?
Capillaries
What vessels have the lowest flow velocity?
Capillaries
How does the pressure gradient determine flow?
The pressure gradient drives flow from high to low pressure
What vessels have the account for the highest TPR?
Arterioles account for most of the TPR
What vessels contain the most blood volume?
Veins provide most of the blood storage capacity
What is the largest determinant of blood viscosity (η)?
Blood viscosity depends mostly on hematocrit
What factors increase blood viscosity?
Polycythemia Viscosity is increased in hyperproteinemic states (e.g. multiple myeloma)
What factors reduce blood viscosity?
Anemia
Compliance equation
Compliance = ΔV/ΔP
What is ionotropy?
Changes in contractility -> altered CO for a given RA pressure (preload)
What is venous return?
Changes in circulating volume or venous tone -> altered RA pressure for a given CO Mean systemic pressure changes with volume/venous tone
What is total peripheral resistance?
At a given mean systemic pressure and RA pressure, changes in TPR -> altered CO
Factors that increase venous return
Fluid infusion Sympathetic activity
Factors that decrease venous return
Acute hemorrhage Spinal anesthesia Nitroglycerin
Vasopressors effect on TPR
Increase
Exercise effect on TPR
Decreased
AV shunt effect on TPR
Decreased
Figures on cardiac and vascular function curves
Pg 281
Pressure-volume loops and the cardiac cycle
Pg. 282
S1 heart sound is caused by?
Mitral and tricuspid valve closure
S1 heart sound is loudest at?
Mitral area
S2 heart sound is caused by?
Aortic and pulmonary valve closure
S2 heart sound is loudest?
Left upper sternal border
S3 heart sound is caused by?
In early diastole during rapid ventricular filling phase and is associated with increased filling pressures (e.g. mitral regurgitation, HF) and more common in dilated ventricles (but can be normal in children, young adults and pregnant women)
S3 heart sound is best heard?
Left-lateral decubitus with the bell side of the stethoscope at the apex of the heart along the 5th intercostal space at the midclavicular line
What phase of the cardiac-cycle has the highest O2 consumption?
Isovolumetric contraction
Describe the isovolumetric contraction phase of the cardiac cycle
Period between mitral valve closing and aortic valve opening, this is also the period of greatest O2 consumption
Describe the systolic ejection phase of the cardiac cycle
Period between aortic valve opening and closing
Describe the isovolumetric relaxation phase of the cardiac cycle
Period between aortic valve closing and mitral valve opening
Describe the rapid filling phase of the cardiac cycle
Period just after mitral valve reopening
Describe the reduced filling phase of the cardiac cycle
Period just before mitral valve closing
JVP AKA
Jugular venous pulse
Describe the jugular venous pulse
A wave -> c wave -> x descent -> v wave -> y descent
Describe the a-wave of the jugular venous pulse
Atrial contraction
The a-wave of jugular venous pulse is absent in?
Atrial fibrillation
Describe the c-wave of the jugular venous pulse
RV contraction (closed tricuspid valve bulging into the atrium)
The x-descent of jugular venous pulse is absent in?
Reduced or absent in tricuspid regurgitation and right HF because pressure gradients are reduced
