The cardiovascular system consists of the heart and all the blood vessels of the body. There are 6-8 liters of blood continuously circulating in this system. The heart is a four-chambered muscular organ located slightly to the left of the central thoracic cavity. It is located behind the sternum and between the two lungs, protected by the thorax. The upper two chambers of the heart are called the atria and the bottom two chambers are called the ventricles. A thick, fibrous tissue wall further divides the heart into left and right parts. There are four valves in the heart. These valves act as valves to ensure the direction and amount of blood flow that circulates through the heart. Functions of the heart The function of the heart is to pump, or circulate, blood through the blood vessels into the various parts of the body. Blood provides nutrients and oxygen to the body. All cells need oxygen to survive. Blood vessels are divided into arteries and veins. Arteries transport blood that is rich in oxygen. The aorta is the largest artery in the body. Arteries emanate from the aorta like tree branches to all parts of the body, providing them with oxygen-rich blood. The veins transport the low oxygenated or deoxygenated blood used by the cells. Deoxygenated blood flows from the small veins to the largest veins, the superior and inferior vena cava. The veins carry the deoxygenated blood back to the right heart, where it is replenished with oxygen through the pulmonary circulation. The heart beats 60-100 times per minute and continues to do so for the rest of your life. This contraction is stimulated and controlled by the heart’s natural pacing points. When the current starts, it causes simultaneous contractions of the right and left atria, followed by simultaneous contractions of the right and left ventricles. This synchronized electrical stimulation causes the heart to pump and circulate blood. This blood flow can be sensed by your pulse. The electrical activity of the heart as it pumps can also be traced by an electrocardiogram. Coronary arteries The heart requires a large supply of oxygen and nutrients. This is necessary for its pumping function to be effective and efficient. The heart does not absorb the blood that circulates through it. The coronary arteries provide the special network of blood vessels necessary to supply the heart with food and oxygen. The coronary arteries are the first level branches of the aorta and are located on the surface of the heart. Cardiovascular surgery Coronary artery disease Coronary artery is a state caused by atherosclerosis (hardening of the arteries) of the coronary arteries. A common type of atherosclerosis is the deposition of fat in the coronary arteries (atherosclerosis). This process usually takes many years to occur and is not detected until symptoms appear. Like the process of depositing rust in the pipes, these blockages reduce the blood flow to the coronary arteries and reduce the oxygen and substances available to the heart muscle. As a result, the heart muscle lacks the oxygen and food necessary for its proper function. When the blockage is severe enough, it usually results in “angina symptoms”. Angina is the medical term used to describe the pain and discomfort in the chest caused by a lack of oxygen and nutrients to the heart muscle. Patients may complain of tightness, heaviness, burning, fullness or sharp pain in the chest. These discomforts may radiate to the arms, neck, jaw and posterior regions. They usually last for a few minutes, occur with various activities and stress, and resolve with rest or nitroglycerin. Prolonged anginal events may lead to a cardiac event (myocardial infarction), which is the necrosis of a portion of the heart. There may be times when there are severe obstructive lesions in the coronary arteries with little to no angina symptoms. Shortness of breath, fatigue or indigestion may be a sign of reduced blood supply to the heart muscle. The causes of coronary artery disease are not known. However, certain physical conditions and lifestyle habits that we refer to as risk factors can increase the chances of developing this disease. Risk factors are divided into 2 categories: 1) modifiable (habits that can be controlled and changed) and 2) unmodifiable (personalities that cannot be changed or adjusted, etc.). Modifiable categories: 1) smoking; 2) hypertension; 3) diabetes; 4) high fat diet/high cholesterol levels; 5) overweight status; 6) lack of exercise; 7) stress; Non-modifiable categories: 8) family history of heart disease; 9) gender; 10) increasing age. Coronary artery disease can occur in individuals with few or no high-risk factors. Those with several high-risk factors can greatly double their chances of developing atherosclerosis and subsequent coronary artery disease. Coronary artery disease cannot be cured with drugs or surgery. Modification of high-risk factors may control and delay the onset of coronary artery disease. Coronary artery bypass surgery Coronary artery bypass surgery is the surgical treatment of diseased coronary arteries. A section of vein is usually taken from the lower extremity and anastomosed at one end to the distal end of the obstructed coronary artery and at the other end to the aorta. This vein graft bypasses the obstructed part of the coronary artery and can improve blood flow to the myocardium that is not adequately supplied with oxygen. Multiple segments of the vein can be applied for multiple obstructions. The arterial obstruction is usually not removed or cleared. In short, bypass surgery is like a detour due to traffic congestion. In individual cases, a portion of the obstruction may be surgically removed from the artery; this is called endarterectomy. The remaining veins of the lower extremity can gradually increase their efficiency and can compensate for the function of the missing veins. Surgery of the lower extremity does not interfere with walking and normal use of the legs. In some cases, the left and right internal mammary arteries, located on either side of the sternum, can also be used for bypass. Coronary bypass surgery does not cure coronary heart disease. However, improved blood flow to the heart muscle can help relieve angina, allow you to do more activity and can improve your heart’s ability to pump blood. Valvular heart disease occurs when one or more of the heart’s valves function abnormally. Rheumatic fever, bacterial infections, congenital anomalies, degenerative valve disease or aging are common causes of valve function changes. Thickening or scarring of the valves can lead to abnormal valve function, with the end result being abnormal valve opening or closing. The most common types of valvular heart disease include valves that fail to open completely (obstruction) or fail to close completely (incomplete closure). A valve that does not close completely can increase pressure in the emptying of the heart chambers because of incomplete antegrade blood flow. A valve that does not close completely can overload the emptying chamber. This is because blood flow passes back and forth through the valve as if it were a bi-directional open door. Leakage of blood flow through an abnormal functioning valve can be heard as a heart murmur on physical examination, and obstruction and incomplete closure of the valve can increase the workload of the heart. Surgical repair of the diseased valve (valvuloplasty) or valve replacement may allow the heart to work more efficiently. If valve replacement is needed, the diseased valve needs to be removed and an artificial valve prosthesis used. The prosthetic valve may be a mechanical or tissue valve. Your surgeon will discuss with you the type of valve he thinks is most appropriate for your type of valve defect. A subset of patients after valve replacement require anticoagulation therapy to retard clotting. This treatment reduces the likelihood of clots as the blood flows through the valve. Anticoagulation needs to be monitored closely with blood tests, and a nurse specializing in thoracic surgery will discuss this and other information about heart valve surgery with you in detail at the time of your discharge. Atrial septal defect An atrial septal defect is a common type of congenital heart disease (a defect that is present at birth). The two upper chambers of the heart are called the atria. An atrial septal defect is an abnormal opening of the septum of these two chambers. This opening (hole) can be repaired by patching or by direct suturing. If a patch is applied, a synthetic material or a piece of pericardial tissue (the sac outside the heart) is usually used. Ventricular septal defect A ventricular septal defect is an opening (hole) in the bottom two chambers of the heart. It can be the result of congenital heart disease (anomalies at birth) or myocardial infarction (heart attack). This opening can be closed with an artificial patch or a portion of the pericardium (the sac on the outside of the heart). Ventricular wall tumor A ventricular wall tumor is a weakened part of the wall of the heart muscle. It occurs in the ventricle (the cavity at the bottom of the heart) and forms a small ball-like protrusion outward. It is usually the result of a decrease in blood supply to the heart muscle after a heart attack (myocardial infarction). The necrotic part of the myocardium heals after a heart attack by forming a scar. If the area of scarred myocardium is large, a ventricular wall tumor may form. Large ventricular wall tumors can interfere with the pumping function of the ventricles, which can lead to heart failure. Some ventricular tumors may also cause arrhythmias. Surgical repair of ventricular wall tumors may be recommended to improve ventricular pumping and reduce arrhythmias. Arrhythmia surgery The heart beats 60-100 times per minute, providing continuous pumping throughout the body. This regular contraction is controlled by a natural pacemaker called the sinoatrial node (SA node) located in the upper right atrium. From there, an electric current is sent to the atrioventricular node (AV node) and then to the bundle branches and Purkinje fibers, which trigger the heart’s consistent pumping function. Disturbances in the regular rhythm of the heart are called arrhythmias. Arrhythmias are caused by disturbances in the cardiac conduction pathway. A short circuit in this electrical pathway interferes with the natural pacemaker heartbeat. There are many different types of arrhythmias. Some arrhythmias can slow the heartbeat and others can make it faster. These irregular heartbeats can be detected by an electrocardiogram. Sometimes they can be detected by escape beats or by feeling for a pulse. Many patients have irregular heart rhythms (arrhythmias) but do not need treatment or medication. Others need medication or a pacemaker to control the abnormal heartbeat. Severe arrhythmias may affect the heart’s ability to pump blood after a period of time. If the heart cannot pump adequately, blood pressure and the circulation of blood and oxygen cannot be maintained. This type of arrhythmia is more dangerous and is known as a fatal arrhythmia. In arrhythmias, there may be confusion, transient blackness, dizziness, loss of consciousness, or even cardiac arrest. Usually medications are able to control the arrhythmia. Usually medications can control the arrhythmia and accompanying symptoms. When medications do not work, then the arrhythmia may have to be controlled by surgery, and there are various procedures for arrhythmias. Your cardiologist will discuss with you in detail the type of arrhythmia surgery you need.