Exam 2 – Cardio Ch 20 Flashcards
How can you improve heart pumping?
Nervous simulation
Hypertrophy of cardiac muscle secondary to increased work load
How can nervous stimulation improve heart pumping?
Sympathetic stimulation (increases heart rate) Parasympathetic inhibition (decreases heart rate)
How does hypertrophy of cardiac muscle secondary to increased work load improve heart pumping?
Increased size
Increased strength
What can cause decreased cardiac function?
Damage to cardiac muscle Inhibition of nervous control Arrhythmias Valvular heart disease Increased arterial pressure or hypertension Congenital heart disease Myocarditis/inflammation
What is the cardiac output for a horse? Arterial pressure?
25-40 L/min
115 mmHg
What is the cardiac output for a cow? Arterial pressure?
25-39 L/min
150 +/- 27 mmHg
What is the cardiac output for a dog? Arterial pressure?
3-5 L/min/m^2
Less than 160 mmHg
What is the cardiac output for a cat? Arterial pressure?
100 ml/kg/min
114-137 mmHg
What are non-cardiac factors that cause decreased cardiac output?
Decreased blood volume
Acute venous dilation
Obstruction of large vessels
Decreased tissue mass
How can cardiac output be measured?
Oxygen Fick method
Indicator dilution method
Echocardiography
Electromagnetic flowmeter
What is the Oxygen Fick method?
Measures oxygen levels in right heart and left heart
Measures disappearance of oxygen from inhaled air
What is the indicator dilution method?
Dyes
Thermal (cold solution)
What is the most used indicator dilution method?
Cold solution
What is the most used method of measuring cardiac output?
Echocardiography
What is cardiac output influenced by?
Metabolic rate
Fitness
Age
Size
What does the cardiac index express?
Cardiac output in relation to body size
Does the heart or peripheral circulation control cardiac output?
Peripheral circulation
What is cardiac output?
The sum of all tissue flows and is affected by their regulation
What is cardiac output proportional to?
Tissue O2 use
1/TPR when arterial pressure is constant
Look at cardiac output curves
Look at cardiac output curves
What is the plateau of the cardiac output curve determined by?
Heart strength
Wha does sympathetics do to the plateau?
Increases it
If parasympathetics decrease, what happens plateau?
Increases it
What does heart hypertrophy do to the plateau?
Increases it
What does myocardial infarction do to the plateau?
Decreases it
What does valvular disease do to the plateau?
Decreases it
What does myocarditis do to the plateau?
Decreases it
What does cardiac tamponade do to the plateau?
Decreases it
What does metabolic damage do to the plateau?
Decreases it
What does the pericardial sac act as?
A protectant and lubricant so that the heart can be without friction
What is tamponade?
When the pericardial sac fills with fluid
What does decreased cardiac output cause for tamponade?
Less tamponade
What are effects of intrapleural pressure on cardiac output curve?
Changes in thorax which prevent blood from returning to the heart
Pressure in right atrium must be less than pressure in the great veins for flow to occur
Pressure in veins are slow to rise
What happens if the pressure in the right atrium is not less than the great veins?
There will be a back up so that the great veins can get a pressure that is higher than that of the right atrium
Look at the effects of intrapleural pressure on cardiac output curve
Look at the effects of intrapleural pressure on cardiac output curve
What is the mean systemic filing pressure?
What the pressure is coming from the jugular vein to the right atrium and how it responds as the right atrium pressure goes up
If resistance is decreased and blood is left in the periphery, what happens to cardiac return?
It increases
If resistance is increased, what happens?
More blood is left to sit on the venous side and pressure will have to be built up enough to overcome the mean systemic filling pressure
What happens if cardiac output does not equal venous return?
Blood would either accumulate or be removed from the chest
If left ventricle output equals 6 and venous return is equal to 5, what happens to blood?
It would be shifted to the periphery
How do you calculate the return of blood to the left heart?
(Mean pulmonic filling pressure – left atrial pressure) / pulmonary vascular resistance
If the left heart fails and the right heart keeps pumping, what happens to mean pulmonic filling pressure and mean systemic filling pressure? What does that cause?
Increases MPFP
Decreases MSFP (because blood is being removed from systemic circulation)
Overloads the pulmonary system
What does left atrial pressure have to be less than?
What is coming from the lungs
What happens once the left heart starts failing?
Blood starts backing up into the lungs, which will very quickly start backing up into the right heart and cause right heart failure
Which is worse clinically, left heart or right heart failure?
Left heart. You can live longer with right heart failure
