Alterations Of Cardiovascular Function II Flashcards
What is a definition of cardiac output?
Cardiac output is the volume of blood pumped by the left ventricle in a minute.
Cardiac output (CO) is a clinical variable used to measure heart function. It is measured in ml/minute.
What is a definition of preload?
The pressure of the blood in the ventricle at the end of diastole.
At the end of diastole, the volume of blood in the ventricle has a pressure. This pressure is called the end-diastolic-pressure or the preload. This one of the pressures that the ventricle has to contract against in order to eject the blood. If the preload increases, the ventricle has to contract harder in order to eject the blood.
One factor that would increase left ventricular afterload is:
primary hypertension.
Primary hypertension is by definition, elevated blood pressure in the systemic arteries and is the primary cause of evaluated left ventricular afterload.
An effect of beta-1 receptor stimulation is to:
Increase heart rate.
When stimulated by the presence of catecholamines (epinephrine and norepinephrine) released by the sympathetic nervous system, beta-1 receptors cause an increase in heat rate. Beta-1 receptors also cause an increase in ventricular contractility, but in many cases of heart failure the ventricles cannot respond.
How does activation of the sympathetic nervous system help the body maintain blood pressure in left ventricular failure (LVF)?
Norepinephrine stimulates alpha-1 receptors which results in arterial vasoconstriction.
Beta-1 receptors increase the heart rate
What is the main cause of fluid retention in left ventricular failure (LVF)?
Release of aldosterone
In LVF, a drop in cardiac output leads to a temporary drop in blood pressure. This drop in blood pressure activates the renin-angiotensin-aldosterone system leading eventually to the secretion of aldosterone from the adrenal cortex. Aldosterone stimulates sodium reabsorption (i.e., retention) in the kidneys, and water follows the sodium. Therefore aldosterone causes fluid retention in an attempt to raise blood pressure. Unfortunately fluid retention of LVF causes an increase in LV preload and can worsen pulmonary edema.
What is the most common cause of left ventricular failure that is systolic in nature?
Coronary artery disease leading to myocardial ischemia
Myocardial ischemia leads to myocardial hypoxia, and when the ventricles do not receive enough oxygen they are unable to contract effectively.
Other cause is myocardial infraction
Why does long term primary (systemic) hypertension eventually lead to left ventricular failure?
Increased afterload leads to left ventricular hypertrophy and diastolic dysfunction
primary hypertension causes an increase in left ventricular afterload. The ventricle responds to the high afterload by contracting with greater force. This eventually leads to the development of myocardial hypertrophy. When the wall of the ventricle becomes very think, it often has difficulty relaxing and filling, which is the definition of diastolic dysfunction.
In left ventricular failure, the symptoms of tachypnea, dyspnea and cough are related to:
pulmonary edema.
Left ventricular failure causes pressures backs up from the left atrium to the pulmonary veins, to the pulmonary capillaries. The elevated pulmonary capillary pressures causes water to seep out to the capillaries into the lung tissue causing pulmonary edema. Pulmonary edema results in decreased oxygen transport from the alveoli to the pulmonary capillaries resulting in hypoxemia. Hypoxemia leads to tachypnea (increased respiratory rate) and dyspnea (shortness of breath) as the respiratory centers in the brainstem sense the lack of oxygen. The cough occurs when the edema either collapses alveoli or alveolar ducts, or seeps into the alveoli, stimulating cough receptors in the respiratory tract. Individuals with severe pulmonary edema often cough up a frothy sputum - air mixed with water.
Patients with left ventricular failure often have cool hands and feet. Which of the following statements best describes the pathophysiology underlying this clinical manifestations?
The effects of alpha-1 receptors causes vasonctriction of the peripheral arteries and arterioles.
The arteries and arterioles out in our extremities all have alpha-1 receptors. This vasoconstriction reduces blood flow to the extremities which makes the hands and feet feel cool to the touch. With severe heart failure we see severe vasoconstriction which can make the limbs feel cold, look discolored (blue or purple and often mottled), and can cause ulcerations or gangrene.
What are the causes of right ventricular failure?
left ventricular failure.
primary pulmonary hypertension.
chronic pulmonary disease.
Why do individuals with right ventricular failure develop edema in their lower legs?
Right ventricular failure causes pressures to back up into the veins of the lower extremities
Which of the following blood vessels will experience an increase in pressures with right ventricular failure?
External jugular veins
Right ventricular failure causes pressures to back up into the right atrium and eventually the superior and inferior vena cavas. As the right ventricular failure progresses, pressures can back up further. From the superior vena cava, blood pressures will back up into the jugular veins (internal and external). The back up of blood into the external jugular veins can be visualized, and is a sign of right ventricular failure.
In left ventricular failure, decreased ventricular contractility leads to:
Increased residual volumes in the left ventricle
Pulmonary edema in left ventricular failure is caused by:
Pressures that back up from the left atrium to the pulmonary capillaries.
