Patho HF & Valvular Disorders

cardiac output

the volume of blood pumped through the body in 1 minute

cardiac output =

stroke volume x heart rate

stroke volume

volume of blood pumped out of the left ventricle with each beat

what is the body’s goal

to maintain consistent CO

what primarily influences HR

• hormones

• ANS

preload

• filling

• stretch on the heart muscle right before it contracts from the volume of blood filling the ventricles

what effects preload

the amount of blood returning to the heart

afterload

• resistance

• the resistance the heart must fight against to open the valves and pump blood

more stretch =

higher SV

more resistance =

lower SV

contractility

• squeeze

• the intrinsic muscle strength & force of the heart’s contraction

what effects contractility

• disease

• prolonged ischemia

• MI

higher contractility =

higher SV

frank-starlings law

• increased stretch only inc stroke volume to a certain point

• too much preload → overstretch → dec SV and CO

heart failure

• an abnormality in cardiac structure or function leads to the failure of the heart to pump enough blood to meet the body’s oxygen requirements

• a state or syndrome, not one disease

• cardiac abnormality is required for heart to fail

what does heart failure result in

insufficient CO

what causes HF

other diseases

normal blood flow

unidirectional (valves)