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A pericardial effusion is an abnormal accumulation of fluid in the pericardial cavity. The pericardium is a two-part membrane surrounding the heart: the outer fibrous connective membrane and an inner two-layered serous membrane. The two layers of the serous membrane enclose the pericardial cavity (the potential space) between them. [1]
In patients with ischemic heart disease there is an accumulation of angiogenic growth factors in the pericardial fluid. These contribute to angiogenesis (the formation of new blood vessels) and arteriogenesis (the increase in diameter of existing arterioles). This helps to prevent myocardial ischemia (lack of oxygen to the heart). [6]
Beck's triad is a collection of three medical signs associated with acute cardiac tamponade, a medical emergency when excessive fluid accumulates in the pericardial sac around the heart and impairs its ability to pump blood. The signs are low arterial blood pressure, distended neck veins, and distant, muffled heart sounds. [1]
Cardiac physiology or heart function is the study of healthy, unimpaired function of the heart: involving blood flow; myocardium structure; the electrical conduction system of the heart; the cardiac cycle and cardiac output and how these interact and depend on one another.
The blood pressure in the circulation is principally due to the pumping action of the heart. [32] The pumping action of the heart generates pulsatile blood flow, which is conducted into the arteries, across the micro-circulation and eventually, back via the venous system to the heart.
The systemic circulation is a circuit loop that delivers oxygenated blood from the left heart to the rest of the body, and returns deoxygenated blood back to the right heart via large veins known as the venae cavae. The systemic circulation can also be defined as two parts – a macrocirculation and a microcirculation.
Consequently, the heart becomes compressed due to its inability to fully relax. [21] If fluid continues to accumulate, each successive diastolic period leads to less blood entering the ventricles. Eventually, increasing pressure on the heart forces the septum to bend in towards the left ventricle, leading to a decrease in stroke volume. [12]
The heart did not pump blood around, the heart's motion sucked blood in during diastole and the blood moved by the pulsation of the arteries themselves. [93] Galen believed the arterial blood was created by venous blood passing from the left ventricle to the right through 'pores' between the ventricles. [ 90 ]