Heart disease that results from another physiological disorder is considered secondary disease, differentiated from primary myocardial diseases that result from inherent problems in the cardiac tissue. When the heart no longer functions efficiently, the strain leads to degrading processes that ultimately result in heart failure.
Heart Valve Disorders
The heart has valves between its chambers to prevent a backflow of blood, called regurgitation. This maintains the pressure and cardiac output. Deformed or obstructed valves can increase a chamber’s workload, usually the ventricle, requiring more mechanical force to push blood through the system.
Valves can undergo stenosis, the stiffening of the leaflets, or prolapse, a stretching and floppiness leading to regurgitation. Stenosis can be caused by growths or scarring. Inflammation, called valvulitis, can lead to such scarring. Stenotic valves are not as flexible and may shrink, resulting in a hole between the chambers, and requiring replacement. Growths on the valves are actually deposited particles, and the condition is called endocarditis. They may be calcium deposits or vegetative growths (infective endocarditis).
Infective endocarditis is caused by infectious agents like bacteria, although vegetative growth can also be non-infectious/sterile and due to autoimmune reactions. An example of an autoimmune disorder leading to endocarditis is systemic lupus erythematosus (SLE), and the endocarditis is given the more specific name of Libman-Sacks.
Pericardial Disease
The heart is surrounded by a membrane called the pericardium. Pericarditis is inflammation of the pericardium and is most often due to infection, usually viral in nature. In the case of lymphatic obstruction, the inflammation may lead to pericardial effusion, the secretion of excess fluid around the heart. The heart muscle then strains to pump against the pressure of the membrane.
As the inflammation clears, the pericardium may scar in the process of fibrosis, resulting in constrictive pericarditis. Such a restriction of the heart leads to cardiac tamponade. The presence of blood in the effusion is called hemopericardium, and it is often due to hemorrhage.
Myocardial Infarction – Heart Attack
The outer part of the heart and pericardium receives oxygen and nutrients via the coronary arteries. When the supply of oxygen is cut off to the coronary arteries, often by blockage by cholesterol and atherosclerotic plaques, it results in a myocardial infarction (an infarct). The immediate effect of the infarct on heart function is known as a heart attack. Resuming blood flow through the coronary arteries as soon as possible is the sought intervention.
If the infarct is chronic, ischemic injury may occur, resulting in scars and compromised heart function. Thus, the complications of a heart attack can include ischemic heart disease, where portions of the heart cannot receive enough oxygen and do not function, reducing the efficiency of the muscle. Scarring may disrupt valve control, cause pericarditis and restrictive effusions, result in mural thrombi, and the wall of the heart can rupture against the strain of the extra workload.
Some information provided by Kumar, Cotran, Robbins. Basic Pathology, 7th ed. Saunders.
