Your heart is a muscular organ about the size of your fist. It is located behind the lower part of your sternum (breast bone). With each beat of the heart, the heart muscle pumps and circulates blood through the body. The heart can be divided into two sides with a muscular wall separating them called the septum. Each side of the heart (R & L) have two chambers stacked on top of each other. The upper chambers are called atria and the lower chambers are called ventricles. Blood flow through the heart is a continuous action providing the body with oxygen rich blood. Every minute, at rest, the heart beats 60-80 beats per minute and pumps approximately 5 liters of blood through the body. When exercising, the heart rate and the amount of blood pumped each minute increases to meet the physical demand. The flow of blood follows a continuous loop to supply the body with needed nutrients. The valves in the heart ensure that the blood flows in one direction. Oxygen depleted blood enters the right atria from the body through the venous system (vena cava). When the atria contracts the blood is propelled into the right ventricle through the tricuspid valve. When the ventricle contracts the forward flow of blood sends the circulation through the pulmonary valve to the lungs. It is in the lungs that the blood releases carbon dioxide and picks up oxygen. The oxygen rich blood then returns to the left atria which contracts and propels the blood through the mitral valve to the left ventricle. It is the left ventricle that sends the blood through the aortic valve to the whole body. Once you understand the blood flow one can see that the ventricles are the primary pumps of the heart. The left ventricle is the largest muscle chamber in the heart with the most workload placed upon it. For the heart muscle to contract it needs a stimulation to direct it. This is done through an electrical system that is present in the muscle. Each heart muscle cell has the potential to create stimulation. In a healthy heart, the normal electrical pathways occur along fixed lines of specialized cells that produce an even contraction when stimulated. 1
Electrical stimulation starts in the top of the right atria at the sinus atrial (SA) node, which has a resting rate of 60-80 firings per minute. This node acts as a spark plug and fires a stimulation that travels through the atria resulting in contraction of the right and left atria at the same time. Because the blood needs to fill the ventricles from the atria there is a delay in the electrical charge reaching the ventricles. The electrical stimulation can only reach the ventricles through the conducting system, which consists of the atrioventricular (AV) node and the bundle of HIS and its branches. These pathways allow for quick transmission through the ventricles and a strong contraction results. The electrical system in the heart is well balanced and relies on intact pathways. The system will respond to increased demands placed on the heart from exercise, stress or illness by increasing its firing capabilities. Disruption in the conduction system will lead to irregular stimulations, which we call arrhythmias. Like any muscle in your body the heart also needs to have oxygen to function and it does this by having its own circulatory system. Coronary arteries are blood vessels that originate off the aorta and surround your heart muscle. They feed oxygen rich blood to the heart muscle. There are two main coronary arteries the left and the right. The left artery divides into two arteries the anterior descending branch, which supplies blood to most of the left side of the heart and also the septum. The other branch is called the circumflex and it provides blood to the outer left and back of the heart. The right coronary artery supplies blood to the right side of the heart and in most people it supplies the blood to the SA and AV nodes. Over time the heart may produce additional arteries, which are called collateral circulation. These vessels increase the supply of blood through new pathways that branch off the main arteries. The coronary arteries are susceptible to a buildup of plaque inside their walls which can lead to blocking the flow of blood to the heart muscle. This is known as coronary artery disease. 2
When cardiac disease states exist the function of the heart will be impaired. It is the goal at COACH to maintain and improve cardiac health through improving risk factors to optimize the function of the heart. Cardiac Disease States Arteriosclerosis Arteriosclerosis is a chronic disease of the arteries characterized by an abnormal thickening and hardening of the vessel walls that result in a loss of elasticity. Atherosclerosis is a specific type of arteriosclerosis, but the terms are sometimes used interchangeably. Coronary arteries are particularly susceptible to atherosclerosis. In this condition, thickening of the vessel results in a buildup of plaque made up of fats, cholesterol, and other substances found in blood. The plaque causes narrowing of the vessel and can restrict blood flow. This process is known as Coronary Artery Disease (CAD). It is not usually until the diameter is decreased 70% that symptoms appear in the form of Angina or chest pain. In the coronary arteries, an unstable plaque deposit may break off resulting in a rough area on the arterial wall, which may attract the formation of a clot. It can be this clot formation that creates a 100% blockage of the coronary artery so that the flow of oxygen rich blood to the heart muscle is blocked completely. The result of this process is known as a heart attack or myocardial infarction (MI). Hypertension (High blood pressure) Blood pressure is the pressure (mmhg) exerted on the walls of the blood vessels. The pumping of the ventricle as well as the tension of the artery walls will determine the blood pressure. The systolic pressure or top number in a blood pressure result is the measure of the pressure force when your heart contracts and pushes out the blood from the ventricles. The diastolic pressure or lower number is the measure of when your heart relaxes between beats. systolic 120 80 diastolic High blood pressure or hypertension is an elevation in the blood pressure either systolic, diastolic or both and is generally felt to be present with consistent pressures over 140/85. Hypertension increases your risk of cardiac disease, heart attack, and stroke. Hypertension is one of the most controllable risk factors for coronary artery disease. It is felt to accelerate coronary artery disease and increase the workload of the heart. Monitoring and management of high blood pressure is described in Risk Factors (p.9). 3
Angina Angina is the medical term applied to lack of blood flow to the heart muscle (ischemia) causing pain or discomfort. It occurs when the heart muscle is not getting enough oxygen. This can result from either a lack of supply of blood through the coronary arteries to the heart muscle cell and/or an increased demand for oxygen to the heart muscle cells from exercise, stress or illness. Coronary artery blockages are the primary cause of angina. The pain or discomfort felt is quite individual and can include vague sensations, feelings or aches in the chest area. Often people describe angina as a sense of pressure or burning, squeezing, heaviness, and frequently indigestion. The pain can radiate to your neck, shoulders or arms. There are primarily two types of angina. Stable angina is the type that occurs from an increased demand for oxygen. It usually occurs consistently with a certain level of exertion and is relieved by rest and/or taking the medication nitroglycerine. Unstable angina is defined as chest pain/discomfort occurring at rest or if the pattern of angina changes. This is a more serious form of angina as it may indicate a large blockage in the coronary arteries. It can be due to coronary artery spasm or plaque rupture (unstable angina). Treatment for angina is primarily medical through the use of medications and can sometimes include interventional such as angioplasty, stents, or coronary artery bypass surgery. Aneurysms An aneurysm is a ballooning or bulging of a blood vessel due to weakening of the wall from disease, injury or an abnormality from birth. Often aneurysms occur due to high blood pressure placed on the weakened area. Aneurysms can occur in vessels in many vessels including those in and out of heart (aorta), coronary arteries, and the arteries in the brain. Management includes blood pressure control or surgery to correct the aneurysm. Myocardial Infarction or Heart Attack A myocardial infarction commonly known as a heart attack happens when the blockage of blood flow (oxygen) to the heart muscle is of sufficient intensity and duration to cause recognizable death (necrosis) to the heart muscle tissue. It is usually the result of a blocked coronary artery by a plaque or blood clot. An area of dead muscle surrounding the blockage cannot be regenerated and instead scar tissue forms in the area. This scar tissue takes a few weeks to form depending on the size of the infarct and is non-functioning tissue. That means it cannot contract like the other muscle fiber nor can it transmit the electrical impulses in the heart. The location & size of the infarct will determine how the heart functions after. Collateral circulation (newly formed arteries) may help decrease the amount of damage and may help in the healing process. 4
Symptoms include Persistent, crushing chest pain that may radiate to arms, jaw, neck, and shoulder blades (persists > 20 minutes, often unrelieved by nitroglycerin) Pressure, tightness, or aching Nausea, indigestion Cold Sweat Shortness of breath Anxiety, feeling of impending doom Treatment Relief of symptoms (morphine, oxygen, nitroglycerin via intravenous) Blood thinners to dissolve the clot and halt heart muscle damage Risk factor modification to reduce future heart events Prompt treatment is necessary as damage occurring to the heart may be minimized if treatment is started immediately. Arrhythmias An arrhythmia is an abnormal rate or rhythm in the heart which results in a beating of the heart that is not efficient in pumping the blood. These heart rhythms can be irregular or regular and cause symptoms such as palpitations, dizziness, or fainting. Treatment can be through medications, surgery, and the use of pacemakers. Types of arrhythmias include: Premature contractions are extra beats that can originate either in the atria or ventricles. Generally these beats are not harmful and do not require treatment if they are not symptomatic. Bradycardia is an excessive slowing of the heartbeat. This can originate in the atria where the sinus (SA) node slows or lower down in the conduction system where there may be a blockage or slowing of the electrical conduction. Symptoms may include fatigue, dizziness or fainting. Treatment should be sought and may include medications or surgical implantation of a pacemaker. Tachycardia is a rapid beating of the heart. These arrhythmias can originate in the ventricles or more commonly in the atria. During these rhythms the excessively fast heart rate is not usually caused by the spark plug (sinus node) but another site or multiple sites in the atria are firing rapidly. Palpitations, dizziness, and fainting may occur. Medical attention should be sought and may consist of medications or cardioversion, which is performed in the hospital. Atrial Fibrillation occurs where the atria beats irregularly and not as one strong coordinated contraction. Blood cannot be pumped effectively into the lower chambers. Atrial fibrillation is the most common tachycardia (excessive fast rate) occurring in ~6% of individuals over 65 years of age. Treatment is directed to slowing the rate so the 5
heart can pump more efficiently or eliminating the fibrillation completely by having the sinus node take over again as the spark plug. This is done through medications or cardioversion. Congestive Heart Failure (CHF) CHF is the inability of the heart to function as an effective pump to meet the needs of the body. This inability to pump may be a result of a heart attack, viral infection, intravenous drug abuse or some other illness. Please see Heart Function section (purple). Cardiac Procedures Angiogram: An angiogram is a test that takes X-ray pictures of the coronary arteries and the vessels that supply blood to the heart. During the angiogram, a special dye is injected a catheter into the coronary arteries so that the blood vessels become visible. This allows the cardiologist to determine if there are any blockages in the coronary arteries. Angioplasty: An angioplasty is a procedure designed to dilate (widen or expand) narrowed coronary arteries, in order to enhance blood flow to the heart. The procedure is very similar to an angiogram. The catheter used has a balloon on its tip, which is inflated and deflated a number of times to compress the plaque and enlarge the diameter of the coronary artery. Frequently a coronary stent is inserted during the procedure to prop open the coronary artery. It is made of a mesh-like material and remains in the coronary artery. Once properly placed, stents do not move (migrate). This procedure is also known as Percutaneous Coronary Intervention (PCI). Transcatheter Aortic Valve Implantation (TAVI): A TAVI is a minimally invasive procedure that allows doctors to replace a diseased valve using a long catheter tube inserted through an artery in the groin. A new specifically designed replacement valve that is attached to a flexible stainless steel mesh is then sent up the catheter where it is implanted over the existing valve in a beating heart. This is typically a 90 minute procedure and patients are discharged from hospital as early as 3-4 days after the procedure. It is offered to patients who are considered too sick for open heart surgery. Aortic valve replacement is still considered the gold standard, with excellent outcomes that have been proven over long periods of follow-up. Coronary-Artery Bypass-Graft (CABG) Surgery: The need for CABG is determined from diagnostic tests and assessment. If the results of an angiogram show one or more vessels are significantly occluded bypass may be 6
recommended. CABG or open-heart surgery is a surgical procedure where arteries or veins are taken from one part of the body and sutured around the blockage in the coronary artery. A portion of a vein from the leg or arm or the internal mammary artery is used. During surgery these arteries or veins are connected directly to the coronary arteries on the surface of the heart beyond the blockages. This way blood can flow through them to bypass the narrowed or closed points. CABG will improve the blood flow to the heart. Exercise tolerance is improved and fatigue is reduced. Angina is often eliminated following CABG. Echocardiogram: This is an ultrasound of the heart. This enables the doctor to visualize the hearts function as a muscle, the chambers, and the valves in the heart in a noninvasive manner aiding in the diagnosis of a variety of cardiac abnormalities. Electrocardiogram (ECG): This is a graphic record of the hearts electrical system. This provides important information about the rhythm, size and electrical abnormalities of the heart, such as previous heart attacks. Heart Valve Surgery: Heart valves may need repair due to birth defects, rheumatic fever, bacterial infections or aging. If a valve does not close properly, blood can leak back through the valve. Heart valve problems increase the workload of the heart. When the heart can no longer keep up, heart failure may result. Valves can be repaired or replaced through open heart surgery. The best solution is chosen for each individual patient based on diagnostic tests. Pacemaker: This is a small battery operated device that produces the electrical impulse needed to keep the heart beating in a regular rhythm. The lead (a wire) is implanted in the wall of the heart. The pacemaker functions like a thermostat, if the pulse drops too slow the pacemaker will kick in. A pacemaker cannot remove extra beats or prevent fast rhythms and is used only for bradycardias (slow rhythms). It is usually implanted under the collarbone or in the abdomen. Nuclear Medicine Testing: This involves the use of radioactive substances to help diagnose coronary artery disease and areas of injured heart muscle. These scans are done at rest and after exercise on the treadmill. The radioactive substance is injected intravenously and absorbed in the heart. If patients are unable to exercise on a treadmill (i.e. bad hips), a chemical stress test (Persantine Cardiolite) for the heart is administered. Persantine is a medication that increases your heart rate mimicking your heart at exercise. REFERENCES: 1. American College of Sports Medicine Resource Manual for Guidelines for Exercise Testing and Prescription. 3 rd ed. Baltimore: Williams & Wilkins, 1998. 2. Andreoli K et al. Comprehensive Cardiac Care 6 th ed., C. V Mosby Co. 1987. 7
3. Canadian Guidelines for Cardiac Rehabilitation and Cardiovascular Disease Prevention. First Edition. National Guidelines Committee, James A. Stone, BZ, MSc,MD, PhD, FRCPC, Cleo Cyr, Rn CCN, ACSM Certified, et al. 3:39-47, 1999. 4. The Merck Manual. Sixteenth Edition. 25:473-522, Merck Research Laboratories, 1992. 5. Micheal D. Lemonick. Where Heart Trouble Begins. Time Magazine July 19, 1999. 6. American Heart Association. Fighting Heart Disease and Stroke. What is a heart Attack? Angina Pectoris. American Heart Association (AHA Web site), 2000. 7. Sibbald, W. Synopsis of Critical Care 3 rd ed. Williams and Wilkins., Baltimore. 1988. 8