Systolic Heart Failure And Diastolic Heart Failure
Systolic heart failure and diastolic heart failure are the two main types of heart failure. A combination of the two is also seen.
In systolic heart failure, the less forceful contraction of the heart causes some of the blood in the heart to remain in the ventricles or the lower chambers of the heart. This leads to accumulation of blood in the lungs and in the veins.
In diastolic heart failure, the stiffness of the heart prevents it from relaxing after each contraction, which decreases its capacity to fill with blood. If the contraction of the heart is normal, it keeps pumping out the normal amount of blood, making up for its decreased capacity to fill up. But, gradually, the blood returning to the heart gets accumulated in the lungs and veins. Often, both types of heart failure occur concurrently.
Causes
Any heart disorder, previously existing or which has developed over a period of time can cause heart failure. Some disorders that have an indirect effect on heart function can also result in heart failure. It can develop gradually over a period of time or it can happen all of a sudden. It could be either systolic heart failure or diastolic heart failure or, as in the case of high blood pressure and heart valve disorders, it can be both type of heart failure.
Systolic Heart failure: Disorders that cause systolic heart failure may damage the entire heart or a portion of it, so that, the heart cannot contract normally. Usually, several factors work together to precipitate heart failure.
Coronary artery disease reduces the flow of oxygen-rich blood to the heart muscle. Since oxygen is required for normal contraction of the heart, its deprivation leads to systolic heart failure. Blockage of an artery supplying blood to the heart muscles (coronary artery) can cause a heart attack that destroys an area of heart muscle. That area becomes unable contract normally. Damage caused to large areas of heart muscle due to coronary heart disease or a heart attack can be the cause of heart failure.
Myocarditis, in which heart muscles become inflamed due to bacterial or viral infection can damage them, adversely affecting the heart’s ability to pump blood. Certain drugs used in treatment of cancer and substances like alcohol can also damage heart muscles. Some drugs, such as NSAIDs (nonsteroidal anti-inflammatory drugs), may cause to fluid retention in the body, increasing the workload of the heart resulting in heart failure.
A congenital defect in the connections between the chambers of the heart, causing abnormal recirculation of blood within the heart, increases its workload resulting in heart failure. Heart valve disorders such as stenosis or narrowing of valve, obstruct smooth flow of blood, and cause regurgitation or backward leakage of blood through a valve. It can be stressful to the heart, causing enlargement over a period of time and subsequently, heart failure.
When heart rhythm changes due to faulty electrical conduction system, the heart is unable to pump blood efficiently. Fast or irregular heart rhythms over an extended period can result in heart failure.
A large blood clot (pulmonary embolism), or many smaller blood clots in the pulmonary artery can block it, resulting in sudden heart failure. The blockage in the artery makes it hard for the heart to pump blood into the pulmonary arteries difficult. The extra effort required to pump blood into the blocked pulmonary arteries can result in the enlargement the right side of the heart and causing the walls of the right ventricle to become thick and stiff. It results in right-sided heart failure. A very large clot is a life threatening situation requiring immediate intervention.
Certain disorders of the lung, such as pulmonary hypertension which damages pulmonary arteries, increasing the load on the heart. This forces the right side of the heart to work harder to pump blood into the lungs. The person develops a condition called cor pulmonale resulting in enlargement of the right ventricle. This causes right-sided heart failure.
Disorders that indirectly cause systolic heart failure are severe anemia, hyperthyroidism, hypothyroidism, and kidney failure. Anemia is the deficiency of hemoglobin, the oxygen carrying substance in the Red blood cells. Anemia can occur due to many reasons such as chronic bleeding from a stomach ulcer. Anemia reduces the amount of oxygen the blood carries, requiring heart to work harder to supply same amount of oxygen to tissues. In hyperthyroidism, the overactive thyroid gland stimulates the heart excessively, making it to pump too fast resulting in incomplete emptying with eah beat, eventually tiring it out. In hypothyroidism, the underactive thyroid gland, fails to produce enough thyroid hormones. Since muscles depend on thyroid hormones for normal functioning, the low levels of thyroid hormones make all muscles, including the heart muscles weak. In kidney failure, when kidneys do not filter out excess fluid from the blood, the resultant larger volume of blood overloads the heart causing heart failure eventually.
Diastolic Heart failure: High blood pressure which is not correctly treated is the usual cause of diastolic heart failure. High blood pressure requires the heart to pump with extra force to push blood into the arteries against the higher pressure existing there. This causes thickening of the heart’s walls (hypertrophy), which eventually becomes stiff. When the walls of the heart lose their elasticity, heart does not get filled quickly and sufficiently. When an inadequately filled heart contracts, less blood gets pumped. Diabetes also stiffens the walls of the ventricle. Natural ageing of the heart too makes the heart’s walls stiff. Diabetes and high blood pressure, combined with age-related stiffening makes heart failure extremely common among the older people.
Amyloidosis, characterized by the presence of an abnormal protein called amyloid, when present in the heart, stiffens the walls of the heart. Some tropical parasites enter into the heart muscle causing stiffening which results in heart failure even in young people.
Constrictive pericarditis is a condition where the double-walled fluid filled pericardium that envelopes the heart has become stiff preventing the normal functioning of the heart.
Compensatory Mechanisms
The body combats heart failure through various mechanisms. The body’s initial response to stress caused by heart failure is the release of hormones Epinephrine and norepinephrine. They make the heart to pump faster and more forcefully, thus increasing the amount of blood pumped out by the heart (cardiac output), this compensatory mechanism helps to make up for the decreased pumping ability of the heart at least temporarily. This is beneficial to a healthy people, enabling them to perform extra work when required. However, this additional demand on the heart, further deteriorates the condition of those who are already suffering from heart failure.
When less amount of blood is pumped out by the heart due to heart failure, body tries to maintain the blood pressure by increasing the amount of salt and water retained in the body by decreasing the urine output by the kidneys. Salt and water retention increases the volume of blood in the bloodstream and helping maintain blood pressure. However, the larger volume of blood stretches the heart muscle, enlarging the ventricles. Initially, when the heart muscle is stretched, it contracts more forcefully, improving the heart function temporarily. But, continued stretching weakens the heart’s muscles, worsening the heart failure.
Ventricular hypertrophy or enlargement of the walls of the ventricles is an important compensatory mechanism. Thicker walls can contract with more force helping to pump out more blood, but, eventually they become stiff, further worsening heart failure.
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Yasser Elnahas
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