Opening any pathology textbook to the Heart chapter provides a long list of things that can go wrong with this essential organ. There are congenital diseases, which are present from birth; heart disease that occurs as we age and is due to the presence of other disease or risk factors; there is congestive heart failure due to problems with the circulation and lungs; there are electrical conductance problems leading to heart beat rhythm changes; pericardial diseases and infections; and problems with the inside of the heart itself, the valves. The heart’s complexity makes for complex disease. What follows is a basic list of heart diseases.
Congestive Heart Failure
Congestive heart failure is the endpoint for many types of heart disease. When the heart is no longer able to eject blood through the aorta, called forward failure, the heart fills and backs up the venous system, called backward failure. Left-sided failure is most often caused by hypertension, ischemic heart disease (heart attack), mitral or aortic valve disease, and primary myocardial diseases. Right-sided failure is most often caused by left-sided heart failure.
The series of events is most often the inability of the heart to pump out blood due to a variety of reasons, as are explained in the following paragraphs. This forward failure results in kidney and liver problems. The blood remaining in the heart causes a congestion of the blood vessels in the lungs, leading to pulmonary edema. This domino effect of congestion results in backward failure and a dilation of the heart chambers as they fill with blood. Compensated heart failure is a maintenance of some output despite the dilation. Decompensated heart failure is an inability to meet the output demand, resulting in death.
Myocardial Infarction Heart Attack
A myocardial infarction is due to a lack of oxygen through the coronary arteries. Ischemic injury may occur, meaning that a lack of oxygen damaged the tissue, resulting in scars and compromised heart function. The coronary artery is often blocked by cholesterol or atherosclerotic plaques.
The complications of a heart attack can include ischemic heart disease, where portions of the heart cannot receive enough oxygen. The scars 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 working tissue against the scar tissue.
Primary Myocardial Diseases
Primary myocardial diseases are diseases of the heart itself. If inflammation has injured the heart tissue, it is called myocarditis. If it is a defect in the heart tissue itself it is called a cardiomyopathy.
There are three main types of cardiomyopathies: dilated, hypertrophic, and restrictive. Dilated cardiomyopathy has progressive contractile dysfunction with both dilation and hypertrophy of the chambers. It occurs with alcohol abuse, toxicity, viral infections, and genetic mutations. Dilation can be pictured as a balloon being stretched out.
Hypertrophic cardiomyopathy presents with pronounced hypertrophy of the left ventricle and interventricular septum, mitral valve thickening, outflow obstruction, and abnormal diastolic filling. Restrictive cardiomyopathy can be explained as the thickening of the heart. Its most common form is a tropical childhood disease called endomyocardial fibrosis. The ventricles eventually become noncompliant.
Cor Pulmonale
Cor pulmonale is a secondary pulmonary heart disease of the right side of the heart caused by pulmonary hypertension or disease. Chronic obstructive pulmonary disease (COPD) is the most common cause of chronic cor pulmonale. This disorder is another cause of right-sided heart failure.
Valve Disorders
Deformed or blocked valves can obstruct a chamber, increasing its workload to force blood through; they are more susceptible to infection; and can result in regurgitation, blood flowing backwards into the wrong chamber.
Valves can undergo stenosis or prolapse. Inflammation, called valvulitis, can lead to a scarring and stenosis. Stenotic valves are not as flexible, may shrink leaving a hole between the chambers, and require replacement. The stenosis can also be due to calcium deposits or vegetative growths (infective endocarditis). Prolapse is a stretching of the valves, leaving them “floppy,” and leads to regurgitation.
Endocarditis is the deposition of particles along the valves. It can be infectious, nonbacterial thrombotic, or sterile vegetations in patients with systemic lupus erythematosus or other autoimmune disorders (known as Libman-Sacks)
Rheumatic fever is an immune reaction against group A Streptococcus. If strep throat is not appropriately treated in can cause rheumatic heart disease among other problems due to the antibodies the immune system produces against it. This results in fibrosis of the valves, among other tissues, hindering their performance and eventually leading to cardiac failure.
Pericardial Disease
The pericardium is the membrane surrounding the heart. Inflammation of the pericardium, called pericarditis, is most often due to infection. In most cases, the infectious agent is a virus. If the inflammation leads to effusions due to lymphatic obstruction, the heart can be strained to pump against the pressure of its membrane. The pericardium can scar as the inflammation clears and lead to fibrosis resulting in constrictive pericarditis. Restriction of the heart leads to what is known as a cardiac tamponade. Another type of effusion is blood. This is called hemopericardium and usually occurs in the presence of other problems, like hemorrhage.
Congenital Heart Disease
A congenital disorder is one present at birth. The heart has a flap that must close when we take our first breath of air outside the womb. The hole is called the foramen ovale. An atrial septal defect, or “hole in the heart,” is present if the flap does not close the hole. The blood is shunted from the left side of the heart to the right and oxygenated blood does not make it out to the body at an appropriate pressure.
Another left to right shunt caused by “holes” in the heart is a ventricular septum. This is the most common congenital heart defect and the holes usually spontaneously close during childhood. The holes are caused by defects in the membrane along the intraventricular muscular ridge.
There is also a channel present in unborn babies that diverts blood from the pulmonary artery to the aorta that normally closes and shrinks after birth. This is the ductus arteriosus. Patent, or persistant, ductus arteriosus is when this channel remains open and blood is not passed through the lungs for oxygenation.
A different kind of defect is a right to left shunt. It results in what is referred to as a “blue baby,” that is a lack of oxygen to the body results in cyanosis and the pink tinge is lost from the baby’s complexion. The shunt occurs as either a transposition of the great vessels, which is the aorta and pulmonary artery being attached to the wrong side of the heart due to a lack of proper formation and growth, or as the Tetralogy of Fallot. The tetralogy is so-named because it consists of four things: a septal defect with a dextraposed aorta overriding it, right ventricle hypertrophy, ventricular septal defect, and a narrowed (and thus obstructed) pulmonary artery or valve.
A narrowing of the aorta, called coarctation, is another defect. If it occurs in infancy it is preductal, if it occurs in the adult it is postductal.
