5 Cardiac Output & Atherosclerosis

what is cardiac ouput?

volume of blood each ventricle pumps out in liters per one minute

what is the formula for cardiac output?

CO = SV (stroke volume) x HR (heart rate)

what is stroke volume?

volume ejected by each ventricle with each beat

how do you measure stroke volume?

EDV-ESV

what are the three factors influencing cardiac output?

preload

afterload

myocardial contractility

the frank starling law is best related to which of the 3 influencing factors of cardiac output?

preload

what is preload?

the amount of blood in the ventricles at the end of diastole (heart’s filling phase) ; initial stretching of cardiac myocytes prior to contraction

what does the frank starling law state?

as the EDV increases, the greater the ventricular sarcomeres are stretched causing a more forceful contraction

what is the sliding filament theory

energy released during contraction depends on initial fiber length (increased EDV → increased length → more cross bridges)

what factors affect preload?

venous return

total blood volme

ventricular compliance

heart rate

atrial contraction

valvular disease

what is afterload?

force that must be overcome for the ventricle to eject its contents ; pressure in wall of LV during ventricular ejection

what are the most common pathologic processes that increase afterload?

systemic hypertension

aortic stenosis

how does the heart respond to persistent increased afterload?

the cardiac cells begin to hypertrophy (thickens)

what is contractility?

force of contraction

contractility is aka?

inotropic state

what affects contractility?

chemical hormonal influences

how does increased contractility affect force?

increased force for the same fiber length ; heart is squeezing harder

how does contracility affect stroke volume and ESV?

increases stroke volume

smaller than normal ESV (typically not all blood gets ejected after contraction but with higher contractility, more blood gets ejected out)

what is compliance?

ease by which ventricle expands with as filling pressure increases

compliance relates to

structural properties of the cardiac muscle and the state of ventricular contraction and relaxation

compliance is the ratio of

change in volume / change in pressure

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if afterload and contractility are constant and preload increases what happens to stroke volume?

increased preload → LV EDV rises → LV can adjust its SV to effectively empty its contents to match diastolic filling volume

if preload and contractility are constant and afterload increases what occurs?

pressure in LV increases → higher ventricular systolic pressure → reduced stroke volume → greater than normal LV ESV

SV rises when (preload, afterload, contractility)

increased preload

decreased afterload

increased contractility

preload is representative of

ventricular EDV

EDV is influenced by the chamber’s

compliance

ventricular ESV depends on

afterload and contractility (NOT PRELOAD)

what is atherosclerosis?

disease in which plaque builds up inside the arteries ; hardening of arteries

what are the two components of atherosclerosis?

plaque buildup

inflammatory response (to chronic injury of arteries → cells accumulate at site of injury )

what are the risk factors for atherosclerosis?

diabetes

obesity

poor diet

physical inactivity

excessive alcohol use

what is the endothelium of an artery & its purpose?

one cell layer thick that lines inside of vascular system

regulates permeability, clotting, immune function

name the 3 basic wall layers from inner to outer

tunica intima

tunica media

tunica adventitia

what is the earliest visible lesion of atherosclerosis?

fatty streak

what are fatty streaks caused by?

endothelial dysfunction ; genetic or chronic exposure to inflammatory markers

what promotes plaque progression?

smooth muscle cell in intima

what is an embolism?

detached thrombus

what is plaque disruption?

when fibrous cap covering atherosclerotic plaque breaks down and exposes the underlying thrombus core

what is plaque rupture determined by?

fibrous cap stability

what increases liklihood of plaque rupture?

localized inflammation

greater LDL cholesterol depositions

what are the complications of atherosclerosis?

calcification of atherosclerotic plaque (increases fragility of vessel wall)

rupture of ulceration (procoagulants in circulation → clots)

heorrhage into plaque

embolization

what are the major targets of atherosclerosis?

large elastic arteries (aorta, carotid, iliac) & large and medium sized muscular arteries

what are the modifiable risk factors of atherosclerosis?

high BP

smoking

lack of physical activity

excess stress

alcohol onsumption

what are the non modifiable risk factors of atherosclerosis?

gender (more common in males)

family hx

advancing age

sleep apnea

pt has a resting heart rate of 100 bpm with EDV of 150ml and ESV of 75 ml. What is the cardiac output?

7500 → 7.5L/min

atherosclerosis of coronary arteries can cause

heart attack