Lecture 4 - Jan 28 Flashcards
What is a mixed vasodilator?
A mixed vasodilator dilates both arteries and veins in the systemic circulation.
What is an example of a mixed vasodilator?
Sodium nitroprusside (nipride) is a mixed vasodilator and a nitric oxide donor.
What effect does a mixed vasodilator have on systemic filling pressure?
It drops the systemic filling pressure and reduces the resistance to venous return.
What is the primary effect of venous vasodilators like nitroglycerin?
They relax the veins more than the arteries, reducing preload and metabolic demands of the heart.
True or False: Nitroglycerin is always the best medication for heart attacks.
False
What is the primary action of ACE inhibitors?
ACE inhibitors primarily reduce afterload.
What makes hydralazine an arterial vasodilator?
It is almost entirely arterial specific, relaxing arteries, though its mechanism of action is unknown.
What is the role of phenylephrine in the circulatory system?
Phenylephrine is a vasoconstrictor that constricts both veins and arteries.
What is the effect of increased preload due to phenylephrine?
It helps the heart pump and increases blood pressure.
What happens to cardiac output after a myocardial infarction (MI)?
Cardiac output decreases, moving from a normal state to a lower output state.
What compensatory mechanisms occur after an MI?
Increased venous tone and stronger heart contractions due to sympathetic nervous system activation.
What is preload?
Preload is the pressure available to fill the heart with blood.
What is afterload?
Afterload is the pressure the heart must pump against, typically the blood pressure outside the aortic valve.
What defines contractility in the heart?
Contractility is the difference in stroke volume while maintaining constant preload and afterload.
Fill in the blank: The body compensates for cardiac failure by _______ venous compliance.
reducing
Fill in the blank: Increased systemic vascular resistance (SVR) makes it _______ to return blood to the heart.
more difficult
What happens to right atrial pressure during cardiac failure?
It increases due to high filling pressures and the heart’s struggle to pump efficiently.
What is the significance of catecholamines in heart function after an MI?
They help maintain heart function but can predispose to arrhythmias if activity is too high.
What occurs as the body retains more fluid after an MI?
Sympathetic activity decreases as blood volume expands.
True or False: High sympathetic activity is ideal for long-term heart function.
False
What is the expected right atrial pressure in a patient dependent on volume?
It is expected to be higher than normal, often around 8 mmHg.
What is afterload?
The force that the heart has to pump against, equivalent to the pressure in the aorta before the aortic valve opens.
Afterload is influenced by systemic vascular resistance and can affect stroke volume.
How does an increase in afterload affect the heart?
It makes it harder for the heart to pump blood, requiring more pressure to open the aortic valve and potentially reducing stroke volume.
Increased afterload can lead to longer duration in the isovolumetric contraction phase.
Define contractility.
A measure of the heart’s ability to contract and is reflected in the change in stroke volume when preload and afterload are held constant.
Increased contractility leads to a greater stroke volume and lower end systolic volume.