Cardiovascular disease includes conditions that affect the structure or function of the heart and is the number one cause of death in the United States. Many conditions fall under this category: coronary artery disease, heart valve disease, myocarditis, pericarditis, endocarditis, arrhythmia, congestive heart failure.
Coronary Artery Disease (CAD)
CAD occurs when the coronary arteries become damaged or diseased due to plaque. Plaque is cholesterol- containing deposits that buildup and cause the arteries to become narrow, decreasing blood flow to the heart. Over time, the decreased blood flow can cause angina with symptoms of chest pain, shortness of breath, and arrhythmias. Such chest pain can be described as pressure, heaviness, numbness, or squeezing of the chest which could be mistaken for indigestion or heartburn. Although angina is usually felt in the chest, it can also cause pain in the shoulders, arms, neck, or back
1,2. A complete blockage can cause a heart attack.
The cause of CAD is thought to begin with an injury to the inner layer endothelial cells of a coronary artery. This injury or damage could begin as early as childhood. Injury to the inner layer of the arteries can occur from smoking, high blood pressure, high cholesterol, diabetes, infections, or a sedentary lifestyle. Once the inner layer of an artery becomes damaged, plaque accumulates at the site of the injury in a process called atherosclerosis. Normal endothelium cells produce anti-coagulation factors such as heparin and nitric oxide to prevent blood clotting formation. However, the injured endothelium cells produce pro-coagulant proteins and pro-inflammatory cytokines which can destabilize the plaque. If the plaque ruptures, platelets clump at the site of injury which can block the artery, leading to a heart attack.
Mitral Valve Prolapses
Mitral valve prolapse is one of the most common forms of valvular heart disease in which one or both mitral leaflets are stretched or prolapsed, that balloon back into the left atrium during the contraction of the left ventricle causing heart valve insufficiency. Because the valve is not able to close completely, blood flows back to the left atrium. Such reversed flow can result in thrombi formation in the left atrium causing stroke or infarctions in other places when the thrombi block the blood flow. The structure of the heart valve is similar to joint cartilage and does not contain a blood supply. Mitral valve prolapse is caused by degenerative changes of the mitral valve. Most patients are asymptomatic. A minority of patients may experience palpitations, dyspnea, or atypical chest pain. Patients with mitral valve prolapse or valvular insufficiency are at increased risk for developing infective endocarditis and sudden death caused by ventricular arrhythmias. Stroke or other systemic infarction may occur from an embolism of thrombi formed in the left atrium.
Myocarditis, Endocarditis, and Pericarditis
Myocarditis is the inflammation of the myocardium that affects the heart muscles and the electrical system, reducing the heart's ability to pump, causing abnormal heart rhythms. Inflammatory infiltrates such as lymphocytes, neutrophils, eosinophils, and granulomas have all been identified in these patients. Along with inflammation, there is also necrosis of cardiac myocyte cells.
The cause of myocarditis is usually due to a viral infection such as adenovirus, hepatitis B and C, parvovirus, and herpes simplex virus. Although viruses are the most common cause, myocarditis can also occur due to other types of infections such as a bacterial infection, parasites, or fungal infection. Pathophysiology remains a subject of research but the potential mechanism is that these infectious agents could cause direct cardiomyocyte injury. Chronic myocarditis can cause dilated cardiomyopathy, or an enlarged heart which leads to heart failure.
Symptoms can vary and some patients may not exhibit any symptoms while others may experience heart murmur, shortness of breath, chest pain, and poor sleep. Symptoms of heart failure include fatigue, dyspnea, and edema of the legs and feet.
Endocarditis is the inflammation of the inner lining of the heart chambers and valves, the endocardium. It is usually caused by an infection from pathogenic microorganisms other than viruses that lodge in the heart valves and infect the endocardium. Such microorganisms include bacteria, fungi, and intracellular parasites. These types of pathogenic microorganisms typically spread from the mouth or another part of the body and enter into the bloodstream where they travel to and attach to abnormal or damaged valves or tissues of the heart.
Deformity of the heart valves due to rheumatic heart disease, mitral valve prolapses, and aortic stenosis with uneven surfaces increases the risk greatly because the germs can adhere to the uneven surface more easily. The heart valves are made of cartilage and do not have a blood supply and therefore have poor protection from the immune system rendering them vulnerable to all kinds of infections.
Depending on the virulence of the microorganism, the manifested symptoms usually cover a wide range of symptoms and aren't always severe. Symptoms may develop slowly over time. In the early stages, the symptoms are similar to many other illnesses including the flu or general infections such as pneumonia and many cases go undiagnosed. In acute cases, patients may experience symptoms that appear suddenly including pale skin, fever, chills, night sweats, muscle or joint pain, nausea, decreased appetite, full or pressure feeling in the upper-left part of the stomach. In severe cases, symptoms include swollen feet and legs, shortness of breath, cough, heart murmur, blood in the urine, and broken blood vessels that appear as red spots on the chest or on the whites of the eyes.
Pericarditis refers to the inflammation of the two thin layers of a sac-like tissue that surround the heart, called the pericardium. The pericardium, separated from the heart by a small amount of fluid, holds the heart in place and helps with heart function. In pericarditis, the inflammation can cause the tissue to rub up against the heart which causes chest pain, a common symptom. Pericarditis can be either acute or chronic and can be caused by viral, bacterial, or fungal infections. In reoccurring pericarditis cases, it is usually the result of an autoimmune condition that causes systemic inflammation such as lupus or rheumatoid arthritis.
Other health disorders can also cause pericarditis such as kidney failure or other chronic heart conditions. In these cases, pericardial effusions can occur in which there is a gradual or sudden increase of fluid accumulation in the pericardial sac. The amount of liquid can increase from 30-50mL to as large as 1000mL. Fluid accumulation can cause symptoms of chest pain, lightheadedness, heart palpitations, shortness of breath, coughing, and fatigue.
Arrhythmia - Bradycardia and Tachycardia
An arrhythmia is an abnormal rate or rhythm of a heartbeat. This typically falls under a heart that beats too quickly (tachycardia), too slowly (bradycardia), or has an irregular pattern with missing heartbeat or premature heartbeat. The most common type of arrhythmia is atrial fibrillation (AFib), which causes a fast heartbeat or tachycardia of more than 100 bpm. In AFib, the hearts atria beat irregularly and out of coordination from the ventricles. This causes symptoms of heart palpitations, shortness of breath, and weakness. The major concern with AFib is the potential to form blood clots within the atria which may then circulate to other organs and lead to ischemia.
Bradycardia is a slowed heart rate of less than 60 bpm at rest. Bradycardia usually occurs due to problems with the sinoatrial node, otherwise known as the hearts natural pacemaker. Problems within the conduction pathways of the heart may also cause a slowed heart rate. Metabolic issues, damage to the heart and certain heart medications can also cause bradycardia. Symptoms include dizziness, shortness of breath, fatigue, chest pain, and heart palpitations.
Heart Failure
Heart failure is a condition in which the heart can no longer pump enough blood to meet the body's needs for oxygen and nutrients. There are three main types of heart failure which include left-sided heart failure, right-sided heart failure, and congestive heart failure.
Left-sided heart failure is a result of heart diseases such as heart attack, hypertension, mitral or aortic valve disease, and primary myocarditis. Early-stage symptoms include breathlessness and cough as the blood transudate into the lung causing pulmonary congestion and edema. As further impairment develops, patients experience dyspnea when lying down because of increased venous return from the lower extremities and elevation of the diaphragm. Symptoms can be relieved by sitting or standing and patients usually sleep while sitting upright. In severe cases, patients may be awakening from sleep with attacks of extreme dyspnea or suffocation.
Right-sided heart failure usually occurs as a result of left-sided failure. Pure right-sided heart failure is caused by pulmonary congestion due to pulmonary disease including COPD, emphysema and pulmonary fibrosis. Symptoms include peripheral edema, portal vein congestion with enlarged spleen and liver, pleural effusion and ascites.
Congestive heart failure occurs when the blood flowing out of the heart slows and blood returning through the veins backs up which causes congestion in the body's tissues. Fluid can eventually collect in the lungs and interfere with breathing, causing shortness of breath. Other symptoms of congestive heart failure include enlarged heart, tachycardia and AFib.
References:
1. R. Dechend, M. Maass, J. Gieffers, et al. Chlamydia pneumoniae Infection of Vascular Smooth Muscle and Endothelial Cells Activates NF-?B and Induces Tissue Factor and PAI-1 Expression, Circulation. 1999; 100: 1369-1373.
2. Joshi R., Khandelwal B., Deepti Joshi D. et al. Chlamydophila Pneumoniae Infection and Cardiovascular Disease, N Am J Med Sci. 2013 Mar; 5(3): 169-181.
