1. Unit Four: The Circulation
Chapter 22: Cardiac Failure
Guyton and Hall, Textbook of Medical Physiology, 12 edition

2. Circulatory Dynamics in Cardiac Failure
Acute Effects of Moderate Cardiac Failure
Reduced cardiac output
Damming of blood in the veins, resulting in
increased venous pressure

3. Circulatory Dynamics in Cardiac Failure
Compensation for Acute Cardiac Failure by
Sympathetic Nervous Reflexes
Baroreceptor reflex
Chemoreceptor reflex
Fig. 22.1

4. Circulatory Dynamics in Cardiac Failure
Chronic Stage of Failure
Retention of fluid by the kidneys-normal urine
output does not occur until the CO and arterial
pressure are back to normal
b. Various degrees of recovery by the heart (Fig. 22.1;
light green line

5. Circulatory Dynamics in Cardiac Failure
Moderate Fluid Retention Can Be Beneficial
Increases the mean systemic filling pressure which
increases the pressure gradient for causing venous flow
toward the heart
b. Distends the veins which reduces the venous resistance

6. Circulatory Dynamics in Cardiac Failure
Detrimental Effects of Excess Fluid Retention
Increases the workload on the damaged heart
Overstretching of the heart causing further damage
Filtration of fluid into the lungs, causing edema and
deoxygenation of the blood
Development of extensive edema in other parts of
the body

7. Circulatory Dynamics in Cardiac Failure
Recovery of the Myocardium after Myocardial Infarction
New collateral blood supply penetrates the periphery of
the infarcted area
Undamaged musculature hypertrophies
c. Degree of recovery depends on the amount of damage

8. Circulatory Dynamics in Cardiac Failure
Decompensated Heart Failure
If severely damaged, no amount of compensation can
make the heart pump a normal output
Fig. 22.2

9. Circulatory Dynamics in Cardiac Failure
Treatment of Decompensation
Strengthening the heart by cardiotonic drugs, such as
digitalis
b. Administering diuretic drugs to increase kidney excretion

10. Unilateral Left Heart Failure
Blood continues to be pumped by the right side with
usual vigor
Therefore, the mean pulmonary filling pressure rises
Volume of blood in the lung increases and results in:
a. Pulmonary vascular congeston
b. Pulmonary edema

11. Low-Output Cardiac Failure—Cardiogenic Shock
Circle of Cardiac Deterioration Leading to Shock
and Death
Treatment
a. Surgically removing the clot in the coronary artery
b. Catheterizing the blocked coronary and infusion
with chemicals to dissolve the clot

12. Edema in Patients with Cardiac Failure
Inability of Acute Cardiac Failure to Cause Peripheral
Edema
Decreased glomerular filtration rate
Activation of the renin-angiotensin system and increased
reabsorption of water and salt by the renal tubules
Increased aldosterone secretion
Activation of the sympathetic nervous system
Role of ANP to Delay Onset of Cardiac Decompensation
Direct effect on kidneys to increase excretion of salt
and water

13. Maximum percentage that the CO can increase above normal
Cardiac Reserve
Maximum percentage that the CO can increase
above normal
Fig Cardiac reserve in different conditions, showing less than zero reserve for two of the conditions