Cardiac Failure
Summary:nive78
The heart is describe as failing when the myocardiun of the ventricles is unable to maintain the circulation of sufficient blood to meet the needs of the body.
ACUTE CARDIAC FAILURE
A sudden diminution in output of blood from both ventricles causes acute reduction in the oxygen supply to all the tissue. Recovery from the acute phase may be followed by chronic failure, or death may be follow by chronic failure, or death may occur due to anoxia of vital centres in the brain. The commonest causes are:
1. Severe damage to an area of cardiac muscle due to ischaemia caused by sudden occlusion of one of the larger coronary arteries by atheroma or with thrombosis.
2. Pulmonary embolism
3. Acute toxic myocarditis
4. Severe cardiac arrhythmia
5. Rupture of a heart chamber or valve cusp
6. Severe malignant hypertension
CHRONIC CARDIAC FAILURE
This develops gradually and in the early stages there may be no symptoms because the heart compensates by increasing the rate and force of concentration and the ventricles dilate. Myocardial cell hypertrophy increases the strenght of the muscles. When further compensation is not possible there is a gradual decline in myocadiac effeciency. During the development of chronic failure, hypoxia and venous congestion causes changes in other system, making still greater demands on the heart, e.g, renal, endocrine, respiratory. Underlying causes include:
1. chronic hypertension, myocardial fibrosis, vavular disease, lung disease, aneamia
2. Previous acute failure
3. Degenerative changes of old age
RIGHT-SIDE OR CONGESTIVE CARDIAC FAILURE
The right ventricle fails when pressure developed within it by the contracting myocardium is less than the force needed to push blood through the lungs. This discrepancy may be caused by increased resistance in the lungs, weakness of the myocardium and / or stenosis and incompetence of valves in the heart or great vessels.
When the compensation has reached its limit and the ventricles is not emptying completely, the right atrium and venae cavae become congested with blood and this is followed by congestion throughout the systemic circulation. The organs affected first are the liver, splen and kidneys oedeme (excess interstitial fluid) of the limbs and ascites (excess fluid in the peritoneal cavity) usually follows.
Resistance to the flow of blood through the lungs
When this is increased the right ventricles has more work to do. It may be caused by:
1. The formation of fibrous tissue following inflamations
2. back pressure of blood from the left side of the heart, e.g, in the ventricular failure, when the mitral valves is stenosed and / or incompetent.
Weakness of the myocardium
This may be caused by ischaemia following numerous small myocardial infarcts.
Cardiac Failure Originally published in Shvoong: http://www.shvoong.com/medicine-and-health/1865581-cardiac-failure/
Summary:nive78
The heart is describe as failing when the myocardiun of the ventricles is unable to maintain the circulation of sufficient blood to meet the needs of the body.
ACUTE CARDIAC FAILURE
A sudden diminution in output of blood from both ventricles causes acute reduction in the oxygen supply to all the tissue. Recovery from the acute phase may be followed by chronic failure, or death may be follow by chronic failure, or death may occur due to anoxia of vital centres in the brain. The commonest causes are:
1. Severe damage to an area of cardiac muscle due to ischaemia caused by sudden occlusion of one of the larger coronary arteries by atheroma or with thrombosis.
2. Pulmonary embolism
3. Acute toxic myocarditis
4. Severe cardiac arrhythmia
5. Rupture of a heart chamber or valve cusp
6. Severe malignant hypertension
CHRONIC CARDIAC FAILURE
This develops gradually and in the early stages there may be no symptoms because the heart compensates by increasing the rate and force of concentration and the ventricles dilate. Myocardial cell hypertrophy increases the strenght of the muscles. When further compensation is not possible there is a gradual decline in myocadiac effeciency. During the development of chronic failure, hypoxia and venous congestion causes changes in other system, making still greater demands on the heart, e.g, renal, endocrine, respiratory. Underlying causes include:
1. chronic hypertension, myocardial fibrosis, vavular disease, lung disease, aneamia
2. Previous acute failure
3. Degenerative changes of old age
RIGHT-SIDE OR CONGESTIVE CARDIAC FAILURE
The right ventricle fails when pressure developed within it by the contracting myocardium is less than the force needed to push blood through the lungs. This discrepancy may be caused by increased resistance in the lungs, weakness of the myocardium and / or stenosis and incompetence of valves in the heart or great vessels.
When the compensation has reached its limit and the ventricles is not emptying completely, the right atrium and venae cavae become congested with blood and this is followed by congestion throughout the systemic circulation. The organs affected first are the liver, splen and kidneys oedeme (excess interstitial fluid) of the limbs and ascites (excess fluid in the peritoneal cavity) usually follows.
Resistance to the flow of blood through the lungs
When this is increased the right ventricles has more work to do. It may be caused by:
1. The formation of fibrous tissue following inflamations
2. back pressure of blood from the left side of the heart, e.g, in the ventricular failure, when the mitral valves is stenosed and / or incompetent.
Weakness of the myocardium
This may be caused by ischaemia following numerous small myocardial infarcts.
Cardiac Failure Originally published in Shvoong: http://www.shvoong.com/medicine-and-health/1865581-cardiac-failure/
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