The function of the
cardiovascular system is to circulate blood. The heart as a pump is a
significant part of the system but the flow of blood is also
dependent on the vascular system. When the cardiovascular system does
not provide enough flow to meet demand then the system is
insufficient. The delivery of oxygen is the most critical function of
the circulatory system and the first to be noticed if flow is
insufficient.
Life depends on the circulation of blood. It can be inadequate only temporarily. The hallmark of Circulatory Insufficiency is the accumulation of lactic acid from anaerobic metabolism which results from inadequate oxygen delivery. Anaerobic metabolism is a short term solution to the problem of inadequate supply or excessive demand. The accumulation of lactic acid cannot continue indefinitely. The usual solution is reducing demand by limiting activity, resting. Heart Failure is a Syndrome with Characteristics of Fluid Retention. This takes time to develop and typically lasts for months to years.
Circulatory Insufficiency is the functional concept of insufficient blood flow to meet demand. The heart as a pump is a significant part of the functioning of the cardiovascular system. The vascular system is also a significant part. High resistance in the vascular system and intense vasoconstriction can limit the flow of blood and is sometimes a part of insufficiency. Circulatory Insufficiency can also develop temporarily in states of high demand in normal individuals such as athletes. When the demand for blood and oxygen exceeds the supply and the tissues are starved of blood and oxygen the circulatory system is insufficient regardless to weather the flow of blood is withing normal or near normal parameters.
Acute Heart Failure is similar to Circulatory Insufficiency with an emphasis on the heart as a pump. When the heart suffers an acute insult such as a large infarction of myocardial tissue the flow of blood may be compromised to become insufficient to meet demand. This generally causes acidemia and shortness of breath. There may also be symptoms referable to the acute heart illness. In the case of acute myocardial infarction there may also be symptoms associated with the infarction of the myocardium such as chest pain.
Circulatory Insufficiency becomes significant when the demand for oxygen exceeds that which can be delivered by the circulatory system. This can occur in normal individuals and is not necessarily pathological. An athlete exercising at or near the limit of their capability will quickly exceed the capacity of their cardiovascular system to deliver oxygen. This can only occur for a limited time but is useful for bursts of strenuous activity. While this is occurring aerobic metabolism will be supplemented by anaerobic metabolism which causes a limited accumulation of lactic acid and a decrease in the pH of the blood. This is not a pathological condition as it is an adaptation and a normal part of strenuous activity.
The acidemia of the blood that occurs in high oxygen demand can be easily reduced and eliminated simply by resting. For this reason anaerobic metabolism in an exercising individual is an entirely different situation than in disease states where the imbalance between supply and demand for oxygen delivery may be difficult to reverse. It is true that short bursts of intense exercise cause anaerobic metabolism to produce lactate and a decrease in blood pH, an acidemia. At the same time increased frequency and depth of respiration will lower CO2 levels and reduce the effect of anaerobic metabolism and limit the acidemia that develops.
The amount of blood flow, that is cardiac output cannot be measured in any convenient way. Measurement requires an invasive catheter in the central circulation or sophisticated imaging. Edema of the lungs is a secondary result of the less effective circulation of blood and easily observed. Edema can be identified by physical signs and a plain film chest X-ray. To rely on what is easily seen leads to the common misunderstanding. Edema of the lungs is only a part of the reason for dyspnea. The proximate cause of the dyspnea comes from the tissues being starved of oxygen due to a deficiency in the delivery of oxygen. This is a cardiovascular disease. The most observable of evidence, the edema is misleading.
While blood provides may nutrients, hormones, and other substances to include any medications, etc. it is oxygen which critically requires adequate flow. Even the removal of CO2 is not so dependent on flow as oxygen is. Oxygen requirements are dramatically influenced by activity. An athlete exercising at the limit of their ability will be limited by the delivery of oxygen which can easily be exceeded by intense metabolic demand.
Cardiovascular insufficiency causes a feeling of shortness of breath as the tissues of the body cannot distinguish between tissue hypoxia due to a lack of blood flow and tissue hypoxia due to the lack of oxygen due to pulmonary disease. People afflicted with cardiovascular insufficiency will not say “my blood is not circulating adequately” which would be correct. They will complain of shortness of breath which suggests something it is not, a pulmonary abnormality when in reality it is an inadequate circulation of blood.
Blood pressure in Circulatory Insufficiency can be either high, low or normal depending on the systemic resistance to blood flow. The flow of blood is dependent on the pressure driving it vs the resistance it encounters. Many people with long standing high blood pressure have very high resistance to blood flow and can develop insufficiency when a sudden increase in resistance is encountered. This may occur with the introduction of drugs with vasoconstrictor properties. Other causes of increased vascular tone such as emotional or physical stress can also cause a sudden increase in vascular resistance. Hypotension often accompanies Circulatory Insufficiency when is it precipitated by infarction of the myocardium or other acute cardiac insult such and sudden valvular insufficiency.
Cyanosis and pallor are not features typical of cardiovascular
insufficiency.
The skin is not a highly metabolic tissue. The imbalance of supply and demand for oxygen primarily affects the muscles and other metabolic tissues. Anerobic metabolism from metabolic tissues such as the muscle causes a general condition of acidemia for the lactic acid produced.