Post 6 All Heart

Septal Defects

                The heart is slightly larger than a clenched fist and works as a pressure pump and suction.   The right side of the heart receives poorly oxygenated blood from the body via the superior and inferior vena cava and pumps it through the pulmonary trunk and arteries to the lungs for oxygenation.  The left side of the heart receives well oxygenated blood from the lungs through the pulmonary veins and pumps it into the aorta for distribution to the body.  The heart is comprised of four chambers which are the left and right atria and the left and right ventricles.  Atria receive blood and pump it into the ventricles.  The ventricles pump the blood out of the heart to the body.

                Septal defects may occur in the atrium or the ventricles.  Clinically significant atrial septal defects vary widely in size and location and may occur as part of more complex congenital heart disease.  The failure of the closure of the fossa ovalis is an atrial septal defect.  Large atrial septal defects allow oxygenated blood from the lungs to be shunted from the left atrium through the defect into the right atrium, causing enlargement of the right atrium and ventricle and dilation of the pulmonary trunk.  A common site of ventricular septal defects is the intraventricular septum.  The size of the defect varies, and it causes a left to right shunt of blood flow through the defect.  A large shunt increases pulmonary blood flow which causes severe pulmonary disease and may cause cardiac failure.  A ventricular septum defect in the muscular part of the septum is less common and frequently closes spontaneously in childhood.

Valvular Heart Disease

                There are four valves in the heart which aide the pumping of blood.   Valves open and close allowing blood flow in only one direction.  The tricuspid valve is between the right atrium and the right ventricle.  The pulmonary valve is between the right ventricle and the pulmonary artery.  The mitral valve is between the left atrium and left ventricle.  The aortic valve is between the left ventricle and the aorta.  Each valve has cusps that open and close fully under normal conditions.  A defective heart valve does not fully open or close .

                Valvular heart disease produces either stenosis or insufficiency.  Stenosis in valves is the failure of a valve to open fully, slowing blood from the chamber.  Insufficiency is regurgitation, or failure of the valve to close completely, allowing blood to flow back into the chamber it was just ejected from. Disorders involving the valves of the heart disturb the pumping efficiency of the heart and result in an increased workload for the heart.  Turbulence is produced when the high-pressure blood flow is restricted, or when regurgitation occurs.  Murmurs can be heard due to turbulence.  Valvular disease can be acute or chronic.   Damaged or defective cardiac valves can be replaced surgically with artificial or xenografted valves in a valvuloplasty procedure. 

Coronary Artery Disease

                The blood vessels of the heart comprise the coronary arteries and cardiac veins which carry blood to and from most of the myocardium.  The right coronary artery supplies blood to the right atrium, most of the right ventricle, part of the left ventricle, part of the intraventricular septum, the sinoatrial node, and the atrioventricular node via its branches.  The left coronary artery, via its branches, supplies blood to the left atrium, most of the left ventricle, part of the right ventricle, most of the intraventricular septum including the atrioventricular bundle, and the sinoatrial node.

                Coronary artery disease has many different causes, but all result in a reduced blood supply to the myocardial tissue.  A myocardial infarction occurs when area of myocardium has undergone tissue death.   This happens when a major artery that supplies the region of myocardium is blocked by an embolus. An embolus is something that travels in the blood stream and blocks a blood vessel.   The artery no longer supplies blood, and become infarcted and then undergoes necrosis which is tissue death.   The most common sites where this occurs is the anterior intraventricular branch of the left coronary artery, the right coronary artery, and the circumflex branch of the left coronary artery.   Coronary artery disease is one of the leading causes of death.

Sources

Clinically Oriented Anatomy

http://www.americanheart.org/presenter.jhtml?identifier=4598 

http://www.nhlbi.nih.gov/health/dci/images/heart_coronary_artery.gif