Chapter 22 - Guyton Flashcards
Define heart failure.
failure of the heart to pump enough blood to satisfy the needs of the body
What two main effects occur immediately as a result of myocardial infarction?
reduced cardiac output and damming of blood in the veins resulting in increased venous pressure
What occurs after acute cardiac failure to compensate for reduced cardiac output?
strong sympathetic stimulation with parasympathetic inhibition (heart becomes stronger pump and mean systemic filling pressure increases–>increased venous return)
How long does it take for the sympathetic reflex to kick in after a myocardial infarction?
The sympathetic reflexes become maximally developed in about 30 seconds.
After the first few minutes of an acute heart attack, a prolonged semi-chronic state begins, characterized mainly by two events:
retention of fluid by the kidneys and (2) varying degrees of recovery of the heart itself over a period of weeks to months
In what two ways can fluid retention be helpful in a patient with cardiac failure?
it increases the mean systemic filling pressure, which increases the pressure gradient for causing venous flow of blood toward the heart; second, it distends the veins, which reduces the venous resistance and allows even more ease of flow of blood to the heart
What are some of the detrimental effects of excessive fluid retention in severe cardiac failure?
overstretching of the heart, thus weakening the heart still more; filtration of fluid into the lungs, causing pulmonary edema and consequent deoxygenation of the blood; and development of extensive edema in most parts of the body
What is compensated heart failure?
chronic compensations resulting from partial heart recovery and renal retention of fluid (several days to several weeks later)
Many people, especially older people, have ______ resting cardiac outputs but mildly to moderately ________ right atrial pressures because of various degrees of “compensated heart failure.”
normal; elevated (increase in right atrial pressure can maintain normal cardiac output despite continued weakness of the heart - these individuals have a diminished cardiac reserve)
The main cause of decompensated heart failure is:
failure of the heart to pump sufficient blood to make the kidneys excrete daily the necessary amounts of fluid.
What are some treatment options for decompensated heart failure (otherwise the patient will die from fluid retention)?
strengthening the heart in any one of several ways, especially by administration of a cardiotonic drug, (digitalis); administering diuretic drugs to increase kidney excretion while at the same time reducing water and salt intake
What is the mechanism of action for digitalis?
strengthen heart contraction by increasing the quantity of calcium ions in muscle fibers (depresses the calcium pump that normally pumps calcium out)
In unilateral left heart failure, why could pulmonary edema result?
mean pulmonary filling pressure rises because of shift of large volumes of blood from the systemic circulation into the pulmonary circulation–>pulmonary edema
Why does acute cardiac failure typically NOT result in immediate peripheral edema?
severe acute cardiac failure often causes a fall in peripheral capillary pressure rather than a rise
Once a person develops _________ shock, the survival rate is often less than 15 per cent.
cardiogenic or cardiac
After the first day or so of overall heart failure or of right-ventricular heart failure, peripheral edema does begin to occur principally because of:
fluid retention by the kidneys
Three known causes of the reduced renal output of urine during cardiac failure:
- Decreased glomerular filtration; 2. Activation of the renin-angiotensin system and increased reabsorption of water and salt by the renal tubules; 3. Increased aldosterone secretion
Excess ____________ is one of the most powerful stimuli known for aldosterone secretion, and the ___________ concentration rises in response to reduced renal function in cardiac failure.
potassium
______ __________ ______ is a hormone released by the atrial walls of the heart when they become stretched.
Atrial natriuretic factor (ANF) - this prevents extreme congestive symptoms during cardiac failure by increasing excretion of salt and water at the kidneys
What are some treatment options for acute pulmonary edema occurring in a patient with late-stage heart failure (act quick or pt. is dead within 20 min - 1 hour)?
putting tourniquets on both arms and legs to sequester much of the blood in the veins; bleeding the patient; giving a rapidly acting diuretic, such as
furosemide; giving the patient pure oxygen to breathe (reverse the blood oxygen desaturation); giving the patient a rapidly acting cardiotonic drug, such as digitalis, to strengthen the heart
The maximum percentage that the cardiac output can increase above normal is called the _______ _______.
cardiac reserve
If a person is unable to increase cardiac output (low cardiac reserve), what symptoms will they have as soon as they start to exercise or stress the heart?
dyspnea, extreme muscle fatigue, excessive increase in HR
The normal state of the circulation is a cardiac output and venous return of __ L/min and a right atrial pressure of __ mm Hg.
5; 0
During the ensuing week after an acute heart attack, the cardiac output and venous return curves rise further because of:
1) some recovery of the heart and 2) renal retention of salt and water, which raises the mean systemic filling pressure
Two days after an acute heart attack, a patient has a cardiac output rises to 4.2 L/min and the right atrial pressure to 7 mm Hg. What is the prognosis for this patient?
buh-bye, The reason the patient will die is decompensated heart failure has resulted from the fact that the cardiac output curve never rises to the critical level of 5 L/min needed to re-establish normal kidney excretion of fluid that would be required to cause balance between fluid input and output.
Two types of high-output cardiac failure?
arteriorvenous fistula (excessive venous return but pumping capability of heart not depressed); beriberi (venous return is greatly increased because of diminished systemic vascular resistance, but pumping capability of the heart is depressed)
