Cardiac Output Flashcards
MAP is proportional to?
HRSVSVR
CO=
HR*SV
Preload is defined as?
The amount of passive tension of the ventricular myocytes in the ventricles by the volume of blood just prior to contraction
Preload is proportional to?
LVEDV/P
Tension is proportional to?
Radius and pressure
Preload is defined by the law of __
Laplace
Stroke volume is dependent on which 3 factors?
Contractility, Preload, and (inversely proportional) to Afterload
Increasing preload does what to stroke volume?
It increases stroke volume only up until a certain point of optimal sarcomere length
Nitrates have what effects on HR, Preload, Afterload, contractility, Tone, and flow
Nitrates will do the following: HR: Increase Preload: DECREASE Afterload: Decrease CTY: No change Tone: Decrease or no change Flow: Increase or no change
B-blockers have what effects on HR, Preload, Afterload, contractility, Tone, and flow
B-blockers will do the following: HR: Decrease Preload: No change Afterload: No change CTY: Decrease Tone: Increase Flow: No change
Calcium channel-blockers have what effects on HR, Preload, Afterload, contractility, Tone, and flow
CCBs will do the following: HR: Decrease or no change Preload: No change Afterload: Decrease CTY: Decrease Tone: Decrease Flow: Increase
Increasing preload has what effect on oxygen demand?
Increasing preload will increase oxygen demand, thus myocardial oxygen demand is defined by preload
How is preload regulated?
- Venous tone (sympathetic activity increases tension in walls of veins and venules, thus increasing preload by forcing blood from veins into the heart)
- Blood volume (increasing blood volume through fluid intake, neurohormonal mechanisms (RAAS, sympathetic nervous system, ADH)
- Body position: Gravity affects venous return. Preload decreases when you stand up
Myocardial demand is proportional to
preload, which is proportional to stroke volume. So in a way, myocardial demand is also proporitonal to stroke volume
Afterload is determined by what 3 factors
- Systemic vascular resistance (Systolic bp)
- Aortic compliance
- Aortic valve resistance