Blood supply of the heart
The heart is located in the chest just behind the breast bone and between the two lungs. It is composed of muscle called myocardium (heart Muscle). Myo- means muscle and cardium means heart. The heart is externally covered by a sheath called pericardium. Two third of heart is in the left side of the chest and one third on the right. Heart is a muscular organ about the size of a fist. The heart is a compact, hollow, muscular organ of a some what conical or pyramidal form possessing, therefore a base, apex, and a series of surfaces and borders. An average adult heart measures about 12 cm from base to apex, 8 to 9 cm transversely at its broadest part, and 6 cm from base to backwards. Its weight, in the male, varies from 280 to 340 gm (average 300gm), while in the female, from 230 to 280 gm (average 250gm). The adult weight is achieved between 17 and 20 years (1). The heart is divided by vertical septa into four chambers, the right and left atria and the right and left ventricles. In simple way, atrium means blood receiving chambers and ventricles means pumping chambers. Right heart chambers (both right atria and right ventricle deal with deoxygenated impure) blood and left sided chambers (both left atrium and ventricle) deal with oxygenated (pure) blood. The impure blood arrives in right ventricle by way of right atrium and right ventricle pumps the blood in the lung circulation through pulmonary artery. The impure blood gets pure in the lungs and comeback to left ventricle through left atrium. Then left heart pumps the pure blood through out the body.
Heart also have four values, they are mistral value or bicuspid valve (bicuspid means two doors), tricuspid valve, aortic valve and pulmonary valve. Valves are not affected by coronary artery disease. Heart disease may involve coronary artery or it may involve the valves. But one should not confuse coronary artery disease with valvular heart disease. They are two separate entities. Valvular heart disease is the end result of rheumatic heart disease but coronary artery disease means the obstruction in the coronary blood flow.
Heart also have four values, they are mistral value or bicuspid valve (bicuspid means two doors), tricuspid valve, aortic valve and pulmonary valve. Valves are not affected by coronary artery disease. Heart disease may involve coronary artery or it may involve the valves. But one should not confuse coronary artery disease with valvular heart disease. They are two separate entities. Valvular heart disease is the end result of rheumatic heart disease but coronary artery disease means the obstruction in the coronary blood flow.
Blood supply of the heart
There are two coronary arteries which supply blood (nutrition) to heart muscle. They are right coronary artery and left coronary artery. Left coronary artery is further divided into two big branches, Left anterior descending artery and left circumflex artery (LCX). So, in reality heart is supplied by three big arteries, right coronary artery (RCA), left anterior descending artery (LAD) and left circumflex artery (LCX). When your doctor tells about IHD he means that some of your coronary artery is not functioning well due to blockage. All the three big arteries are equally important for all person. Even a significant block in one artery may cause severe symptoms. When patients visit his doctor for consultation, doctor off and on uses the terms single, double and triple vessel disease. What does it mean? If one of your artery is significantly blocked it is called single vessel disease (SVD), if two of your arteries are blocked it is called double vessel disease (DVD) and if all of your three arteries are blocked then it is called triple vessel disease (TVD). Left ventricular ejection is very important for the longevity of the patients with heart disease. What does ejection fraction actually mean? In a simple way it implies the strength of the left ventricle. During each heart beat left ventricle pumps certain amount of blood to other parts of the body. This is called ejection fraction. Ejection fraction indicates the strength of your heart, how efficiently your heart can pump blood. During diastole (when ventricle relaxes) blood collects inside the ventricle. The amount of blood that collects inside the ventricle at the end of diastole is about 130 ml. During heart contraction heart pumps about 65% of this incoming volume. Normal ejection fraction (EF) varies from 55% to 75%. If EF is less than 50% it indicates early impairment of heart muscle strength. If EF is in between 35 to 45%, heart function is moderately impaired and if EF is less than 35%, it means that heart pumping is severely impaired.Does all chest pain come from heart?If you get chest pain, it is not always true that you are having heart disease. Your chest does not only contain heart. In fact chest comprises a number of structures other than heart and all of them may cause pain. Some of them mimic heart pain. A number of different conditions may cause chest pain; some are harmless while others are serious. Pain that is not originating from the heart the heart is called no cardiac chest pain. The source of pain may be from any structure within the chest cavity such as the esophagus (food cannal; through which food from the mouth enters into the stomach), lungs of airways. The most common source of chest pain is the chest wall. Typically such pains are transient, lasting form few minutes to few days, reaching peak intensity within few hours, are often produced by certain positions of the body, relieved or intensified by movement of the chest such as breathing, and tender (painful to touch) and this type of pain is usually sharply localized (1). This type of pain is not associated with significant breathlessness, sweating or vomiting. Sometimes viral infection may cause chest pain. Such pain is usually accompanied by low grade fever, dry cough and prostration, which are unusual in heart pain. Ischaemic heart pains usually do not produce fever at its inception. Some times pain usually do not esophagus mimics cardiac pain. Esophagus pain is one of the important causes of chest pain. But this type of pain is burning in nature, has got relation with food intake, typically occurs while the subject is at rest rather than during exercise and is usually relieved by antacid. In addition, the patient often has accompanying symptoms such as gas and acid eructation (2-4). Chest pain originating from within the chest may be from the lungs or from the pleura (covering membrane of the lungs) (5). Breathing deeply intensifies such type of pain. If patient holds breathing pain disappears. Usually there are other clues that it is coming from the lungs; often the patient has a cough or an illness with fever. Chest muscle pain is also some times confused with heart pain. If pain originates from the muscle it is called myalgia chest. This type of pain is localized without any radiation, intensifies with change of body posture and surrounding area is painful to touch. Such pain promptly respond to simple analgesic like paraectamol, aspirin or other NSAID eg indomethacin, diclofenac , ketoprofen etc. Some times pain may be felt in the area where rib bone meets with the cartilage. This is called costochondritis (1). It is much localized pain and the overlying skin sometimes becomes reddish. Chest pain also may originate from the nerve roots coming out of the spinal cord. Each of these sources of chest pain has its own characteristics; however some general features of non cardiac chest should be brought to your attention. So the doctor must exclude the possibilities of no cardiac pain during evaluation of a patient with chest pain.
References
References
1. Ahmed ZU, Chakraborty B, Siddique AM. Evaluation of chest pain –an update. Bangladesh Armed Forces Med J 1997; 21: 163-79.
2. Ayres RCS, Robertson DAF, Naylor K et al. Stress and esophageal motility in normal subject’s patients with irritable bowel syndrome. Gut 1989; 301540-3.
3. Pope CE. Acid-reflux disorders. N Engl J Med 1994; 331 : 656-60.
4. Lam HG, Breumalhof R, Henegouwen GPB et al. Temporal relationships between episodes of non-cardiac chest pain and abnormal esophageal function. Gut 1994; 35: 733-6.
5. Douglas PS. Characteristics of typical and atypical angina pectoris. N Engl J Med 1996; 334; 1311-5.
