Cardiac Physiology Flashcards
What is cardiac output?
The blood ejected by each ventricle in 1 minute.
How is cardiac output calculated?
Stroke volume x heart rate
What is a normal cardiac output?
4 - 6 litres per minute
What is stroke volume?
The volume of blood pumped out of each ventricle with each beat
What are the 3 factors than influence stroke volume?
- Preload
- Afterload
2 Contractility
What is preload?
The amount of blood entering the ventricles during diastole
What is afterload?
The resistance the ventricles must overcome to circulate blood
What is meant by contractility of the heart?
How hard the myocardium can contract
What is the difference between a chronotrope and an inotrope?
Chronotrope - drug that changes the heart rate
Inotrope - drug that changes the force of myocardial contraction.
What is the frank starling law?
The stroke volume of the heart increases in response to an increase in the volume of blood filling the heart - this is due to the length tension relationship in myocardial sarcomeres
What is ejection fraction?
Measurement (expressed as a percentage) of how much blood the left ventricle pumps out with each contraction. It is calculated by dividing the stroke volume/end diastolic LV volume.
What is BNP?
A hormone produced mainly by the left ventricular myocardium in response to strain.
It acts as a vasodilator, diuretic and supresses both sympathetic tone and the RAAS.
What causes heart sound S1?
Closure of the mitral and tricuspid valve
What causes heart should S2?
Closure of the aortic and pulmonary valve
What causes a loud S2?
Hypertension (systemic or pulmonary)
Hyperdynamic states
Atrial septal defect without pulmonary hypertension
