Learning Objectives:
•At the end of the lecture, the students should be able to:
•Define cardiac failure
•Explain the pathophysiology and clinical manifestations of cardiac failure
•Discuss the different types of cardiac failure
•Discuss the physiology of treatment of cardiac failure
Cardiac Failure?
when the heart is unable to pump sufficiently to maintain blood flow to meet the body’s needs
ACUTE EFFECTS OF MODERATE CARDIAC FAILURE
•If a heart suddenly becomes severely damaged, such as by myocardial infarction, the pumping ability of the heart is immediately depressed due to two main effects
(1)reduced cardiac output
(2)damming of blood in the veins, resulting in increased venous pressure
Sympathetic reflexes compensate immediately
CHRONIC EFFECTS OF MODERATE CARDIAC FAILURE
•After the first few minutes of an acute heart attack, a prolonged semi-chronic state begins, characterized mainly by two events:
(1) Retention of fluid by the kidneys
(2) Varying degrees of recovery of the heart itself over a period of weeks to months.
Renal Retention of Fluids in Chronic Failure
What if the heart’s pumping capacity is further reduced
Blood flow to the kidneys finally becomes too low and kidneys are unable to excrete enough salt and water
The extreme fluid retention can lead to:
(1)Increasing the workload on the damaged heart
(2)Overstretching of the heart, which further weakens the heart
(3)Filtration of fluid into the lungs, causing pulmonary edema and consequent deoxygenationof the blood
(4)Development of extensive edema in most parts of the body.
Summary: Acute Cardiac Failure
(1) The instantaneous effect of the cardiac damage leading to sudden drop in cardiac output
(2) Compensation by the sympathetic nervous system, which occurs mainly within the first 30 seconds to 1 minute
(3) Chronic compensations resulting from partial heart recovery and renal retention of fluid.
Compensated Heart Failure
The Point D shows that the body has compensated
An increase in right atrial pressure can maintain the cardiac output at a normal level despite continued weakness of the heartheading to “compensated heart failure.”
But, any attempt to perform heavy exercise usually causes immediate return of the symptoms of acute heart failure because the heart is not able to increase its pumping capacity to the levels required for the exercise.
Severe Cardiac Failure
•Severe damage leads to excessively weakened heart
•The cardiac output cannot rise high enough to make the kidneys excrete normal quantities of fluid.
•Fluid continues to be retained, the person develops more and more edema which leads to
•Progressive elevation of the mean systemic filling pressure, which causes
•Progressive elevation of the right atrial pressure until
•Finally the heart is so overstretched or edematous that it cannot pump even moderate quantities of blood and, fails completely.
Can we treat Decompensation?
1.Sstrengthening the heart, so that the heart becomes strong enough to pump adequate quantities of blood required to make the kidneys function normally again,
- Administering diuretic drugs to increase kidney excretion
- Reducing water and salt intake,
This stops the decompensationprocess by re-establishing normal fluid balance so that at least as much fluid leaves the body as enters it.
Edema in Cardiac Failure
Acute Cardiac Failure
•Acute left cardiac failure can lead to pulmonary edema, even death within minutes to hours.
•Either, Right and left cardiac failure are slow to cause peripheral edema.
•What leads to edema than?
LONGTERM FLUID RETENTION BY THE KIDNEYS CAUSES PERIPHERAL EDEMA
Reduced renal output of urine during cardiac failure has several known causes:
•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.
Treatment options of Pulmonary Edema
1.Tourniquets on both arms and legs
2.Administering a rapidly acting diuretic, such as furosemide
3.Giving the patient pure oxygen to breathe to reverse the blood oxygen desaturation
4.Administering a rapidly acting cardiotonicdrug, such as digitalis,
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