Hemodynamics & Auscultation Flashcards
event responsible for the first heart sound
closure of the AV valves
event responsible for 75% of ventricular filling
rapid early filling in diastole
event responsible for 10-30% of ventricular filling
end-diastole atrial contraction/atrial kick/late filling
percentage of filling provided by early filling
75%
percentage of filling provided by atrial contraction
10-30%
event responsible for the second heart sound
closure of the semilunar valves
cardiac phase that lengthens and shortens with heart rate
diastasis
hibernation
reversible ischemia of a segment of heart wall
normal amount of concentric thickening and contraction expected during systole
30%
normal BP
120/80 mmHg
high BP threshold
140/90 mmHg, taken on two occasions
borderline high BP
130/85 mmHg
low BP threshold
90/60 mmHg
phase responsible for 2/3 of cardiac cycle
diastole
phase responsible for 1/3 of cardiac cycle
systole
fraction of cardiac cycle occupied by diastole
2/3
fraction of cardiac cycle occupied by systole
1/3
describe pulse pressure
difference in arterial blood pressure between systole and diastole
formula for pulse pressure
BPsystole - BPdiastole
describe mean arterial pressure
average arterial blood pressure over one full cardiac cycle
formula for MAP
diastolic method: BPdiastole + (pulse pressure)/3
=BPdiastole + 1/3(BPsystole-BPdiastole)
systolic method: BPsystole + 2/3(BPdiastole)
MAP
mean arterial pressure
simplified Bernoulli’s equation
4v^2
describe pressure gradient
difference in pressures btwn two adjacent locations in the heart, within the same cardiac phase
formula for change in pressure along a flow path
simplified Bernoulli’s = 4v^2
normal LV blood pressures, systole/diastole
100-140 / 3-12 mmHg
normal RV blood pressures, systole/diastole
15-30 / 2-8 mmHg
normal LA blood pressures
mean 2-12 mmHg
normal RA blood pressures
mean 2-8 mmHg
describe stroke volume
blood volume leaving ventricle per contraction
formula for stroke volume using volumes
EDV-ESV
describe cardiac output
blood volume leaving ventricle per minute
formula for cardiac output
SV x HR
describe cardiac index
blood volume leaving the ventricle per minute, relative to body size
formula for cardiac index
CO/BSA
BSA
body surface area
normal stroke volume
70-100 mL
normal cardiac output
4-8 L/min
normal cardiac index
3-4 L/min^2
formula for BSA
root of [weight(kg) x height(cm)]/60
formula for stroke volume using LVOT measurements
CSA x VTI = πr^2 x VTI
preload
end-diastolic volume and how it affects the length-tension relationship
Frank-Starling Law
relates ability to stretch to contractility
more preload = larger ventricle = increased longitudinal stretching of the myocardial fibres = increased tension -> greater contractile force required for ejection
What relationship is demonstrated by the Frank-Starling Law?
Length-Tension relationship of the ventricle
formula for cross sectional area
πr^2
Length-Tension relationship of the ventricle
relates ability to stretch to contractility
more preload = larger ventricle = increased longitudinal stretching of the myocardial fibres = increased tension -> greater contractile force required for ejection
afterload
systemic resistance that the ventricles must pump against
Interval-Strength relationship of the ventricle
relates time for ventricle to fill vs strength contraction required (interval-strength)
affects HR: longer interval btwn heartbeats = increased preload, results in stronger contraction required for ejection
describe inotropic force
relates contractile force to contractile speed (force-velocity):
force required for ejection affects the velocity of ventricle muscle fibre contraction
describe chronotropic force
relates time for ventricle to fill vs strength contraction required (interval-strength)
affects HR: longer interval btwn heartbeats = increased preload, results in stronger contraction required for ejection
Which maneuver can be used to decrease venous return, stroke volume, and cardiac output?
Valsalva maneuver
Which maneuver can be used to increase venous return, stroke volume, and cardiac output?
amyl nitrate inhalation
Force-Velocity relationship of the ventricle
relates contractile force to contractile speed (force-velocity):
force required for ejection affects the velocity of ventricle muscle fibre contraction
factors that affect afterload
viscosity arterial resistance (systemic BP, HTN) vascular geometry (stenosis, structural anomalies) valvular geometry (stenosis, structural anomalies)
factors that affect contractility/inotropic force
increased inotropic force: medications
decreased inotropic force: disease, hypertrophic or fibrosed heart muscle, hypoxia
factors that affect chronotropic force
increased chronotropic force: adrenaline (sympathetic nervous system)
decreased chronotropic force: medications, relaxation, high fitness level
phases of systole
isovolumic contraction time, ventricular systole
phases of diastole
isovolumic relaxation time, early filling, diastasis, late filling
normal IVCT
30-50 ms
normal systolic ejection time
300 ms
In which direction does the muscle contraction progress through the ventricle during systole?
apex to base
normal aortic blood pressure, systole/diastole
100-140 / 60-90 mmHg (systole matches LV pressures)
What marks the transition between IVCT and systole, causing the aortic valve to open?
The LV to aorta pressure gradient must be exceeded.
The rising IVCT pressures in the LV exceed the diastolic aortic pressure (Ao dia 60-90 mmHg, usually around 80)
What marks the transition between systole and IVRT, causing the aortic valve to close?
The LV to aorta pressure gradient must fall.
The risen systolic pressures in the Ao exceed the emptied LV pressure (Ao sys 100-140 mmHg)
normal IVRT
50-100 ms
What marks the transition between IVRT and diastole, causing the mitral valve to open?
The LA to LV pressure gradient must be exceeded.
The rising filling pressures in the LA exceed the LV pressure (LA mean 2-12)
What marks the transition between diastole and IVCT, causing the mitral valve to close?
The LA to LV pressure gradient must fall.
The risen IVCT pressures in the LV exceed the emptied LA pressures.
normal early filling time
150-250 ms
What occurs during diastasis?
atrioventricular pressure gradient equalizes very briefly, dependant on heart rate
normal diastasis time
variable, dependant on heart rate
normal late filling time
???
normal pulmonary artery pressure, systole/diastole
15-30 / 4-12 mmHg
normal RVSP
under 35 mmHg
