Diastolic function in congestive heart failure

Article Abstract:

Heart failure is the inability of the heart to meet the demands placed upon it. Congestive heart failure is such an important type of heart failure that the two terms are sometimes used interchangeably. The primary defect in congestive heart failure may lie either in the systole, the contraction of the ventricles, or in the diastole, the ventricular relaxation. In primary systolic failure, the contraction of the ventricles may fail to expel a sufficient quantity of blood into the arterial system, resulting in backing up of blood in the lungs and the venous system. In primary diastolic failure, the filling of the ventricles by blood in preparation for the next systole may be inadequate. Although most cases of congestive heart failure involve some degree of abnormal diastolic function, in as many as 40 percent of cases the systole is normal and the defect lies in the in the diastole. The author provides a detailed review of the underlying physiological mechanisms of diastolic heart failure as well as some insights into pathological mechanisms occurring at the molecular level. Diastolic failure may result from structure damage such as constrictive pericarditis, which impedes the flow of blood into the ventricles during their relaxation. The abnormalities may also be physiological. For example, the ability of the heart muscle to relax may be impaired. Ventricular hypertrophy is common among patients with heart failure. Damaged heart muscle often responds to the workload by increasing in size; this hypertrophy can result in both structural alterations that impede blood flow and also to impaired relaxation. Some of the pathological effects observed in congestive heart failure may be the result of altered expression of ion pumps in the membranes of individual heart muscle cells themselves. (Consumer Summary produced by Reliance Medical Information, Inc.)

Congestive heart failure, Diastole (Cardiac cycle)

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Abnormal intracellular modulation of calcium as a major cause of cardiac contractile dysfunction

Article Abstract:

The correct balance of calcium in the cells is necessary for the normal functioning of the heart. The physiology of the action of calcium is discussed, as are methods of monitoring calcium levels. Drugs can be used to regulate the effects of calcium by increasing or decreasing its availability to the cells. Drugs such as beta blockers, used to control blood pressure, are positively inotropic (increase the availability of calcium within the cells during heart contraction). Other blood pressure lowering drugs, such as propranolol and the calcium-channel blockers, are negatively inotropic (decrease the uptake of calcium in the cells.) The physiological aspects of these drugs are described. How calcium inside the cells affects heart failure is also discussed. The role of calcium in the physiology of the heart and subsequent treatment implications provide a strong argument for combined therapy. However, the effectiveness of these drugs may diminish as heart failure worsens, because the action of the drugs is dependent on the production of cyclic AMP, which is impaired in heart failure. Evidence suggests that some positively inotropic agents that increase intracellular calcium adversely affect the survival and quality of life of heart failure patients. The effects of the actions of these various types of agents are not yet totally clear. (Consumer Summary produced by Reliance Medical Information, Inc.)

Heart, Heart contraction, Adrenergic beta blockers, Adrenergic beta-antagonists, Calcium, Calcium (Chemical element), Calcium channel blockers

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The clinical implications of venous carbon dioxide tension

Article Abstract:

Carbon dioxide produced as a result of food metabolism circulates in the blood to the lungs where it is removed. The kidneys control the amount of bicarbonate circulating in the blood. These two organs function together to keep the blood maintained at a certain pH (measure of acidity and alkalinity; acid-base levels). The amount of carbon dioxide, oxygen, bicarbonate and pH define blood gases. When the acid-base balance is disturbed, disease can result. The measurement of oxygen in the blood can be determined by using arterial blood samples. Venous blood is used to measure carbon dioxide and bicarbonate levels. It is suggested that in severe circulatory failure both arterial and venous blood samples must be used.

Analysis, Hypercapnia, Blood gases, Blood gas analysis, editorial

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