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What Happens in a Normal Cardiac Cycle?
There are two phases in a normal cardiac cycle – the relaxation phase (diastole) and the contraction phase (systole). In the diastolic phase blood filling of the ventricles occur and during the systolic phase blood is squeezed out into the circulation. The significance of a normal left ventricular diastolic relaxation is that a sufficient amount of blood needed to supply the rest of the body with each heart beat fills the chamber and is ready to be pumped out during systole. This is also the period when the heart muscles are perfused with oxygen-carrying blood from the coronary arteries.
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What Happens in an Abnormal Left Ventricle Diastole?
Abnormal left ventricular diastolic relaxation can occur when there is a stiffness of the left ventricular wall. There is an increase in resistance to filling and as a result the blood that is supposed to normally fill the ventricle is dammed back to the atrium and into lungs. This in turn produces signs and symptoms of lung congestion, hence the disease is referred to as congestive heart failure (CHF).
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Causes of CHF
Heart diseases that result in CHF are usually related to old age, hypertension (high blood pressure), obesity and cardiac ischemia (lack of oxygen). Abnormality in diastolic function of the heart is more common in elderly women. Factors that increase the risk for CHF are strenuous exercise, increased heart rate and blood pressure, a diet rich in salt, anemia, fever, infection, thyroid disease and irregularities in heart beats.
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Symptoms of Heart Failure
Abnormal diastolic relaxation of the left ventricle leads to pulmonary or lung congestion. Failure of the heart to deliver normal amounts of blood to the circulation with each heart beat results in a decrease in oxygenation of the rest of the body. Symptoms of this condition include:
- Shortness of breath
- Difficulty in lying flat on bed
- Sudden awakening from sleep
- Fatigue and weakness
- Reduced tolerance to exercise
- Edema or swelling of the feet, legs and later, the abdomen
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Diagnosis and Treatment of CHF
Clinical history and physical examination usually give the physician a picture of heart failure. Several diagnostic tests may be done to ascertain the cause and stage of heart disease. These tests may include blood and urine tests, imaging exams, ECG, echocardiography and cardiac catheterization.
Treatment begins with recommendations for certain changes in lifestyle such as:
- Stop smoking.
- Shift to a low fat, low sugar and low calorie diet. Lose weight if necessary.
- Limit alcohol intake.
- Reduce strenuous exercise; activities of daily living should be suited to the patient’s capabilities.
Medical therapy should focus on aggressive control of hypertension and blood sugar levels (if increased), reduction of fluids from the lungs and feet by dieresis and control of heart rate. The underlying cause of left ventricular dysfunction should be addressed to improve its function. Medications for heart failure often prescribed are used to relieve symptoms of congestion and poor blood circulation, including antihypertensives, diuretics, blood thinners and others. Early diagnosis and management of the disease are needed to prevent end stage heart disease.
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American Academy of Family Physicians, “Diagnosis and Management of Diastolic Dysfunction and Heart Failure” http://www.aafp.org/afp/2006/0301/p841.html
Richard E. Klabunde, "Cardiac Cycle" http://www.cvphysiology.com/Heart%20Disease/HD002.htm