Lecture 10: Cardiac Output Flashcards
What is the Cardiac cycle?
The cardiac cycle includes all events associated with ONE heartbeat
The cardiac cycle Forces blood from areas of high pressure to areas of Low pressure (HP–>LP)
What is the need for Cardiac Output?
Demand –> Supply
Organ Use –> Oxygen Demand
Tissues, muscles, organs(head,lungs) demand energy and therefore oxygen.
Biochemical processes need energy and circle demand. The heart SUPPLIES THIS DEMAND (Cardiac Output)
The heart generates pressure to Mediate Flow INTO the AORTA
Cardiac Output = heart rate x stroke volume
CO = HR x SV
= can be FASTER, and can increase in VOLUME PER cycle
Why does the heart do during CO and why?
Heart Generates Pressure, in order to Mediate Flow into the Aorta
What is cardiac output?
“the volume of blood ejected into the aorta (from LV) per min”
units = mLmin-1
The heart generates pressure to Mediate Flow INTO the AORTA
Cardiac Output = heart rate x stroke volume
CO = HR x SV
What is the Cardiac Output at rest?
At rest, this cardiac output is between 4-7 mLmin-1 (close to total blood volume)
Venous return of blood = volume of blood returning from the Vasculature to –> the heart every minute
Venous return of blood is linked to CO
What is linked to CO?
Venous Return of clod (Blood Vol from Vasculature –> heart, per min)
What is Stroke Volume?
the volume of blood ejected by the ventricle during each contraction
What is Heart rate?
the number of heartbeats per minute
units = beats per min
Increase in demand of O2 = increase in HR
What is the percentage of the population which dies of Cardiovascular disease?
50% of population
high burden = economic cost to county = decrease working = social impact of premature family loss = focus of work and research
CDV= includes heart attacks, strokes, heart failure, renal failure= all cardiovascular disease
What are you feeling from your pulse?
Pressure wave, pushing against the artery wall, as the LV traps down and squirts blood into the aorta
pushes blood like a piston
60-80 beats per minute
What is the hearts job?
To supply tissues (brain) with oxygen, nutrients into the blood stream
at Rest = demand for O2 is not high
What happens with demand with Exercise?
As air began to move muscles, there were receptors in joint which sensed muscle movement, and these receptor provided input into CNS, telling that you are beginning to exercise, therefore your oxygen levels WILL (not have) go up.
therefore Even Before Oxygen deficit, the CNS was signalling the heart to INCREASE HR as DEMAND is going to go up.
Hearts job was to supply O2
“at rest, cardiac output is about 5L/min and during exercise can be lifted up to about 20L/min”
What happens in the car example regarding increased output?
Faster put foot on accelerator.
(increases revolutions of engine per minute)
HR of the car increased to increase output power(1L engine max)
But different from the car engine, the heart can pump FASTER (HR) and can pump MORE(SV) per cycle
What does an increase in heart rate lead to?
Increase in CO
more volume of blood returning to the heart per minute
after exercise CO= 150 x 130 = 19.5L/min
can effectively Almost Double resting heart rate (4x blood volume pumped per minute)
Why could cardiac output decrease?
Cellular Metabolic Need is reduced
therefore the workload of heart decreases
resting CO= 75 x 70 = 5.25L/min
Why could cardiac output increase?
Demand for O2 increases
therefore CO increases to compensate
What is the cardiac reserve?
Cardiac reserve is the difference between a persons maximum cardiac output and their cardiac output at rest
and average persons cardiac reserve is 4-6 resting volume
Fit person 7-8x cardiac reserve, compared to resting
Severe heart disease has little of no cardiac reserve, as they have breathlessness
What is the cardiac reserve of a fit person?
7-8x CR compared to Resting CO
What is the cardiac reserve of someone with severe heart disease?
Little or no cardiac reserve
as they have breathlessness (symptom of heart failure)
Due to congestion around the lungs
Exercising tissues, demands O2, but with impaired heart function , the Supply of O2 doesn’t math the demand = resulting in breathlessness
Heart failure such that heart doesn’t work efficiently anymore
What is maximum heart rate?
220 beats per min