The Cardiac Cycle Flashcards
Define venous return
Blood returning to the heart from the systemic circulation and pulmonary circulation. Passes through the atrioventricular valves under its own pressure
Define isovolumetric contraction
Ventricles contract, but the pressure is to yet enough to open the semilunar valves therefore ventricular volume remains constant
Define ventricular ejection
Exit of the blood from the heart
Define isovolumetric relaxation
Ventricles relax, but pressure is too much to allow the atrioventricular valves to open but not enough to keep the semi lunar valves open. So all the valves are shut and ventricular volume doesn’t change
Define ventricular filling
Blood enters the ventricles for the atria
What is aortic pressure
A blood pressure measurement
Why is there a decline in aortic pressure?
As the blood is leaving the aorta
When is aortic pressure at its lowest point?
When the aortic valves close in diastole
When does aortic pressure increase?
when the aortic valves open during systole
When is aortic pressure at its maximum? During diastole or systole?
Systole
What causes the formation of the diacritic notch?
It is caused by the shutting of the aortic valve
What is the average aortic pressure = to?
Mean arterial pressure (MAP)
What is usually the value of the diastolic pressure?
80mmHg
What is usually the value of the systolic pressure?
120mmHg
How do you calculate pulse pressure (PP)?
Systolic pressure-Diastolic pressure
SP-DP= PP
E.g. 120-80=40mmHg
What does a high pulse pressure indicate
Can indicate hardening of arteries (Reduced elasticity)
How do you calculate mean arterial pressure (MAP)?
Diastolic pressure + (Pulse pressure/3)
DP+(PP/3)= MAP
E.g. 80+(40/3)=93.3
Why is mean arterial pressure NOT an average of the diastolic and systolic pressure?
Because aortic pressure in a cardiac cycle is closer to the diastolic for more time than the systolic values
What is end diastolic volume (EDV)?
Volume of blood in ventricles at the end of diastole
What is end systolic volume (ESV)?
Volume of blood in the ventricles at the end of systole
How do you calculate stroke volume (SV)?
End diastolic volume - end systolic volume
(EDV-ESV= SV)
E.g. 135-65= 70ml
What is the ejection fraction (EF)?
It is the ratio of volume ejected in one beat to volume immediately prior to ejection
Volume ejected :volume before ejection
How do you calculate the ejection fraction (EF)?
Stroke volume / end diastolic volume
(SV/EDV= EF)
E.g. 70/135= 0.52
Which is 52%
What creates the first heart sound?
First sound occurs at the start of systole when atrioventricular valves close
What creates the second heart sound?
Second heart sound occurs at the start of diastole when the semi lunar valves close
What actually is a heart sound?
Turbulent rush of blood through valves as they narrow and close
What is coronary artery disease?
It is due to the accumulation of atherosclerotic plaque in the coronary arteries
The plaque restricts blood flow to the myocardium
It can lead to chest pain (angina pectoris) and heart attack
Name some of the risk factors associated with coronary artery disease
Genetics Diabetes Obesity High blood pressure High blood cholesterol Sedentary lifestyle Smoking
How do doctors detect coronary artery disease?
Before 1999 injected patients with steptokinase to break up blood clots
Now we use primary angioplasty to detect narrowing of coronary arteries. This involves injecting a radio opaque dye into the coronary circulation and detecting narrowing areas with X-ray imaging
State the 2 routine procedures used to treat coronary artery disease
- Percutaneous transluminal coronary angioplasty (PTCA)
2. Coronary artery bypass graft (CABG)
Describe what a percutaneous transluminal coronary angioplasty entails (PTCA)
A balloon catheter with an uninflected balloon is threaded into the obstructed are in the artery
The balloon is then inflated, it stretches out the arterial walls and squashes any atherosclerosis plaque
After lumen is widened, balloon is deflated and catheter is withdrawn
What are the problems associated with percutaneous transluminal coronary angioplasty (PTCA)?
Balloon inflation induces ischaemia (Restriction of blood supply to tissues) in heart
Damage to the vessel may lead to closure of artery again in 3-6 months. To solve this problem a Stent is introduces to stop the arteries narrowing again
What word describes the renarrowing of arteries?
Restenosing
Describe what a coronary artery bypass graft (CABG) entails
Normally the saphenous vein from the legs is used (sometimes LIMA is used)
It is routine to have between 2-4 grafts to bypass a blocked artery
What are the problems associated with a coronary artery bypass graft (CABG)?
Involves open heart surgery
Involves stopping the heart
Grafts can restenose
Define acyanotic
Blood to systemic circulation has normal levels of oxygen carried
Deine cyanotic
Blood to systemic circulation has reduced level of oxygen carriage, hence darker blood colour and visible cyanosis
What is a septal defect?
Allows blood to flow directly left to right
Give an example of a septal defect?
Ventricular septal defect
What causes ventricular septal defect?
It is caused by incomplete development of the septum. Causes oxygenated and deoxygenated blood to mix
Occurs in 1:500 births
Name some congenital heart diseases
Ventricular septal defect
Coarctation of the aorta
Patent ductus arteriosus
Tetraology of fallot
What is coarctation of the aorta?
Narrowing of the aorta
Which reduces blood flow
Results in the left ventricle to pump harder
So higher blood pressure
What does the ductus arteriosus do?
Allows for oxygen expanse to occur in utero
What is patent ductus arteriosus?
When the blood vessel between the pulmonary trunk and aorta (the ductus arteriosus) remains open after birth.
This results in blood destined for the aorta flowing instead to the pulmonary trunk as it has a lower blood pressure.
This increases the trunk blood pressure and overworks the ventricles
What is Tetralogy of fallot?
It is a combination of 4 defects: ventral septal defect "over riding" aorta Stenosed pulmonary valve Enlarged right ventricle
Results on very little blood reaching the pulmonary circulation leading to cyanosis
What is another name for the teratology of fallot and how common is it?
“Blue Baby”
Occurs in 1:2000 births
What is an “over riding” aorta?
When the aorta takes output from both ventricles
What is the plaque that causes coronary arteries disease called?
atherosclerotic plaque
