Mechanical Events Of The Cardiac Cycle Flashcards
Is the aortic semilunar valve open during ventricular systole ?
No because the aortic pressure is greater than the ventricular pressure
Why is the AV valve open during ventricular diastole ?
Because atrial pressure is greater than ventricular pressure
- causes blood returning via the vena cava to passively enter right ventricule
How much of ventricular filling occurs passively ?
70%
What happens when ventricular pressure exceeds atrial pressure?
Av valves shut creating first heart beat sound - lub
What is the isovolumic phase of contraction?
Both the av valves and semilunar valves are shut creating a little chamber
When do the semilunar valves open ?
When ventricular pressure exceeds arterial pressure enabling blood to be ejected
What causes the closure of the semilunar valves?
The back flow of blood in the aorta and the reduced ventricular pressure
Closure causes the 2nd heart sound dup
What is the dichrotic notch ?
There is a slight rise in aortic pressure due to closure of semilunar valves causing the blood to rebound off the closed cusps
What is isovolumic relaxation ?
After ejection of blood from the ventricles the semilunar valves close and currently the av valves are also closed creating another ventricular chamber
How long is atrial systole ?
0.1 seconds
How long is ventricular systole ?
0.3 seconds
How long is the heart quiescent ?
0.4 seconds
What is the systemic blood pressure average ?
120/80
What is the pulmonary blood pressure ?
25/10
What causes coronary artery disease ?
Accumulation of atherosclerotic plaques in coronary arteries which restrict blood flow
What are the risk factors of coronary artery disease ?
High blood cholesterol Diabetes Smoking Genetic predisposition High blood pressure Obesity Sedentary lifestyle
What is injected into patients with CAD ?
Streptokinase - break up blood clots
What is used to detect blockages in coronary arteries ?
Angiography
What are 2 routine procedures used to treat CAD ?
Percutaneous transluminal coronary angioplasty
Coronary artery bypass graft
What is angioplasty ?
Inflate a balloon in coronary vessels to stretch the walls and squash plaques to widen the lumen
BUT damaged vessels can close again which is why stents are sometimes put in
How does bypass grafting work ?
Usually use saphenous vein from leg
Put 2 to 4 grafts to bypass the blocked arteries
What is ventricular septal defect ?
Hole in the interventricular septum - 1/500 births
What is coarction of the aorta ?
Part of aorta is narrowed which increases load on left ventricle -1/1500 births
What is tetralogy of fallot ?
Four simultaneous defects
- pulmonary trunk too narrow
- pulmonary valve stenosed
- aorta arises from both ventricles
- ventricular septal defect
