Cardiovascular anatomy & physiology 3 Flashcards
Which variables are related by the Frank-Starling mechanism?
a. left ventricular end-diastolic pressure and systemic vascular resistance
b. contractility and cardiac output
c. pulmonary artery occlusion pressure and stroke volume
d. central venous pressure and mean arterial pressure
c. pulmonary artery occlusion pressure and stroke volume
The _____________ is the functional unit of the contractile tissue in the heart.
Sarcomere
The Frank-Starling law says that the heart
will eject a large stroke volume if it’s filled to a higher volume at the end of diastole
Clinical indices of ventricular preload include
CVP
PAD
PAOP
LAP
LVEDP
LVEDV
RVEDV
Clinical indices of ventricular output include
CO
SV
LV stroke work
RV stroke work
______________- contributes 20-30% of the cardiac output
Atrial contraction (atrial kick)
A non-compliant ventricle is stiff, so it is more dependent on a well-timed
atrial kick to fill the ventricle and generate a sufficient stroke volume
Conditions associated with reduced myocardial compliance include
myocardial hypertrophy
fibrosis
aging
heart failure with preserved ejection fraction (diastolic failure)
Patients with reduced myocardial compliance are more likely to experience _____________- in the setting of atrial fibrillation and junctional rhythm.
hypotension
The amount of tension that each sarcomere can generate is directly related to
the number of cross-bridges that can be formed before contraction
Preload is the
ventricular wall tension at the end of diastole (just before contraction)
What factors influence preload?
blood volume
atrial kick
venous tone
intrapericardial pressure
intrathoracic pressure
body position
valvular regurgitation
Atrial kick is lost in the patient with
atrial fibrillation
LVEDP, LAP, and PAOP are all surrogate measures of:
LVEDV
Which conditions impair inotropy? (select 3)
a. hyperkalemia
b. hypovolemia
c. hypoxia
d. hypercalcemia
e. hypocapnia
f. hypercapnia
a. hyperkalemia
c. hypoxia
f. hypercapnia
_______________ is the ability of the myocardial sarcomeres to perform work (shorten and produce force)
Contractility (inotropy)
Inotropy is independent of
preload and afterload
Things that increase contractility include
SNS stimulation
catecholamines
digitalis
PDE inhibitors
Things that decrease contractility (myocardial depression) include
myocardial ischemia
severe hypoxia
acidosis
hypercapnia
hyperkalemia
hypocalcemia
volatile anesthetics
propofol
beta blockers
and some calcium channel blockers
Hyperkalemia _________ contractility by locking the voltage-gated sodium channels in their ______________
impairs; closed-inactive state
____________ affect Contractility particularly _____________
Chemicals; Calcium —> think of the three C’s
How does beta-1 stimulation increase contractility?
activates the enzyme adenylate cyclase which converts ATP to cAMP
cAMP increases activation of protein kinase A (PKA)
Activated PKA accomplishes the following three tasks:
- activation of more L-type Ca2+ channels (more Ca enters the cell)
- stimulation of the ryanodine-2 receptor to release more calcium
- stimulation of the SERCA2 pump to increase Ca2+ uptake with increased Ca2+ release
A reduction of which factor would MOST likely augment stroke volume?
a. preload
b. contractility
c. afterload
d mean arterial blood pressure
c. afterload
_________ is the force that the ventricle must overcome to eject its stroke volume.
Afterload
The ________ needs to overcome a much higher afterload than the _____________
left ventricle; right ventricle
Clinically, we use _______________ as a surrogate for afterload
systemic vascular resistance
The majority of the afterload is set by the
systemic vascular resistance (arteriolar tone)
__________, ____________, and __________________- can set the afterload proximal to the systemic circulation
aortic stenosis, hypertrophic cardiomyopathy, and coarctation of the aorta
We can apply _______________ to help us understand how afterload affects myocardial wall stress
the law of Laplace
Anything that increases wall stress also increases
myocardial oxygen consumption
The following reduce afterload:
arterial vasodilators (e.g. propofol, clevidipine)
sympathectomy (e.g. regional anesthesia)
Wall stress is equal to
wall stress= (intraventricular pressure x radius)/ ventricular thickness
Wall stress is reduced by
decreased intraventricular pressure
decreased radius
increased wall thickness
Which phases of the cardiac cycle are associated with an open mitral valve and closed aortic valve? (select 3)
a. isovolumetric contraction
b. rapid ventricular filling
c. ventricular ejection
d. atrial systole
e. diastasis
f. isovolumetric relaxation
b. rapid ventricular filling
d. atrial systole
e. diastasis
_____________- events always precede _____________ events
Electrical events; mechanical events
The cardiac cycle is a sequence of
electrical and mechanical events that take place from the beginning of one heartbeat to the beginning of the next
The cardiac cycle is divided into
systole (contraction) and diastole (relaxation)
What events occur during systole?
isometric ventricular contraction
ventricular ejection
What events occur during diastole?
isometric ventricular relaxation
rapid ventricular filling
reduced ventricular filling (diastasis)
atrial systole
The pressure-volume (PV) loop shows the
pressure-volume relationship in the left ventricle during one cardiac cycle- one systole and one diastole
The PV loop provides an assessment of
systolic and diastolic function as well as the integrity of the cardiac valves
The PV loop DOES NOT measure
heart rate or linear time
The most important elements of the PV loop include:
height
width
corners
area of the PV loop
The height of the PV loop correlates with
ventricular pressure
The width of the PV loop correlates with
ventricular volume
The corners of the PV loop correlates with
where valves open and close
The area of the PV loop correlates with
myocardial workload
What are the 6 events of the pressure volume loop?
Starting in bottom left corner:
1- rapid filling
2- late filling
3. atrial kick (right corner)
4. isovolumetric contraction (right upstroke)
5. ejection (top of the curve)
6. isovolumetric relaxation
