cardiovascular system ch 5
heart surgeries
All surgical procedures carry risks, and surgery on the heart is certainly no exception. The least dangerous procedure is pacemaker insertion, which stimulates the heart with an electrical pulse. At the high end of surgical risk is heart transplantation, which requires a donor heart, the use of the heart lung machine (cardiopulmonary bypass), and powerful immunosuppressant drugs. Coronary artery bypass graft (CABG), or heart bypass surgery as it is commonly known, uses a blood vessel taken from another part of the body to route blood around a blockage in a coronary artery. Thus blood flow is restored to the myocardium which improves heart function. Joining two ends of blood vessels (or other tube-like structures) is called anastomosis. Pacemaker and pacemaker inserted under chest muscle
The cardiac exercise stress test does indeed place stress on the patient's heart while walking on a treadmill. The heart and blood pressure are monitored during the test. The treadmill angle increases throughout the test causing the heart to work harder. A more complex procedure is cardiac catheterization. A small plastic tubing, or catheter, is inserted into a vein and threaded through the vein into the heart. Pressure readings are taken and a dye is injected so that the heart chambers can be seen. Done on the right side, pressures in the right heart are measured. If the catheter is inserted on the left side, the dye outlines the coronary arteries and their condition can be noted. Sometimes follow-up procedures are necessary if those arteries have any type of blockage. During a cardiac cath, dye can be injected to outline the chambers, show congenital defects, or show narrowed areas.
Angiography is a general term for any procedure that injects a radiopaque dye into a vessel, whether that vessel is an artery, vein, or other type of vessel. Arteriography and venography then are more specific for the type of vessels tested. Arteriography is useful for finding aneurysms or arterial blockages, while venography reveals the state of the vein's valves or dilated walls. Echocardiography uses ultrasound waves to create an image of the heart chambers and functioning of the valves. Doppler ultrasonography determines the amount of blood flow through a blood vessel. Other complex radiologic and nuclear procedures, such as the myocardial perfusion scan, give detailed information about the heart's structure, blood output, and blood flow to the heart's myocardium. It's time to take a moment to check what you know.
Arterial Surgical Procedures The interesting term for removing a dangerous aneurysm is aneurysmectomy. Sometimes an artificial artery is used to replace the defective segment. While plaque in the coronary arteries is dangerous because it could lead to a heart attack, plaque in the carotid arteries restricts blood flow to the brain. Carotid endarterectomy is an effective surgical procedure for enlarging the lumen of these important arteries. Other methods for opening the lumens of plaque-filled arteries are balloon angioplasty and inserting a stent.
Do you remember the danger involved with pericarditis—that of cardiac tamponade? The surgical procedure, pericardiocentesis, removes excess fluid from the pericardial sac using a needle. This gives the heart more room to fill with blood and to pump more effectively. Valve replacement is a good solution when a diseased valve does not open sufficiently or close completely, which interferes with proper blood flow. Usually, an artificial valve is placed in the heart. Sometimes, a valve just needs a bit of reconstructive surgery, called valvoplasty. During many open heart surgeries, it is important that the heart be still. In that case, a cardiopulmonary bypass is used.
Valves of the Left Heart After blood goes to the lungs, it returns to the left heart with a fresh load of oxygen, and much less carbon dioxide. This fresh blood re-enters the heart on the left side now. 1. Blood enters through the opening in the wall of the left atrium. Then it goes through the ________ valve (or bicuspid valve) into the left ventricle. As you can tell from the word bicuspid, this valve only has two cusps. On the right side, there are three lobes in the lung and three valve cusps; on the left side, there are two lobes in the lung and two cusps in the mitral valve. 2. Blood leaving the left ventricle passes through another valve—the ________ valve. Again, the name of this valve tells you where the blood is going—into the aorta.
MITRAL AORTIC
emergency cardiac arrest drug
One of the most important drugs is epinephrine (Adrenalin) that is used to start the heart stopped by cardiac arrest.
Mediastinum The heart and pericardial sac lie between the lungs in the mediastinum. Also in this space are the major blood vessels that enter and leave the heart and the trachea, esophagus, and thymus gland. These major blood vessels are also referred to as the great vessels. They are:
Superior vena cava and inferior vena cava Pulmonary arteries and pulmonary veins Aorta
Valves of the Right Heart The valve between the right atrium and right ventricle is the ___________ valve. It has three small cusps or leaflets of tissue that open and close. The cusps allow the blood to flow from the atrium into the ventricle, but not in reverse. From the right ventricle, the blood passes through another valve—the __________ valve—on its way to the lungs. The name of the valve tells you where the blood is going—to the lungs to get rid of carbon dioxide and pick up oxygen.
TRICUSPID PULMONARY
Chambers of the Heart
The heart is like a duplex building that has an inside wall that divides it into two houses (right and left) and each house contains two rooms. The rooms in the heart are called chambers, which is actually an old word for a room. The right side of the heart has two chambers, and the left side of the heart has two chambers. Each top chamber is an atrium (atria is the plural). Each lower chamber is a ventricle.
Diagnostic Heart Procedures
The most common procedure, which you might even have had at some time, is electrocardiography, abbreviated either as ECG or EKG. The "K" in EKG comes from the Greek word for heart, kardia. The printed record of electrical heart activity is an electrocardiogram. The printout is on long pieces of narrow paper, and sometimes a printout is called a rhythm strip. A Holter monitor is used to record a 24-hour electrocardiogram. This allows the physician to note differences in heart rate and rhythm during daily activities. The patient keeps a record of these activities as well as a diary of meals and symptoms. Telemetry is another method of recording heart rate and rhythm in a continuous format on a monitor. Telemetry is usually used in a hospital setting such as an Intensive Care or Coronary Care Unit, or even the Emergency Department.
medical procedures
The simplest medical procedure is one you have probably experienced—auscultation. The physician can learn a lot about the heart's rhythm, rate, and state of the heart valves just by listening with a stethoscope. Another procedure done for all patients who visit the doctor's office is the taking of vital signs, which includes TPR (temperature, pulse, and respirations) and blood pressure (BP or B/P). Typically, the pulse part of TPR is taken at the radial artery in the wrist, although the pulse can be taken at other pulse points, such as the carotid pulse used at times by paramedics. The apical pulse requires a stethoscope. Other pulse points include the femoral artery, popliteal artery, or the dorsalis pedis artery in the foot. The systolic (higher number when the heart is pumping) and diastolic (lower number when the heart is resting) blood pressures are measured with a sphygmomanometer. Cardioversion is a much more serious procedure used to restore a normal rhythm for a person with an arrhythmia. Defibrillation is a procedure using a defibrillator to stop the rapid and ineffective pulse of ventricular fibrillation
a heart that receives no starting stimulus from the SA node for each heartbeat has asystole, also known as cardiac arrest. Perhaps, like a car starter that works intermittently (it always seems to work at the repair shop), the heart's pacemaker works erratically, resulting in bradycardia or tachycardia. Or even more interestingly, the heart can have sick sinus syndrome, in which these two disorders alternate, sometimes with bradycardia and sometimes with tachycardia. An electrical rhythm disorder, such as just described, is known as an arrhythmia or the alternate term, dysrhythmia. Do you know why the first term has two r's and the second term only has one? I'll tell you on the next page.
The term arrhythmia has two r's because the suffix -rhythmia is preceded by a vowel. If the suffix is not preceded by a vowel, the r is not doubled, as in dysrhythmia. Two very serious forms of tachycardia are flutter and fibrillation, which can occur in the atria or ventricles, but are more serious in the ventricles. The chambers do not have time to fill with sufficient blood before they have to contract again. The number of beats ranges from 250 per minute for flutter to 400 for fibrillation. With the latter, the heart is just quivering like a bowl of gelatin and is not really pumping blood. Emergency procedures, such as defibrillation, are necessary. Premature contractions, especially ventricular ones, are frequently felt by a person as palpitations. When the electrical impulses from the SA node cannot reach the Purkinje fibers to contract the ventricles, the disorder is heart block. This block can occur in varying degrees on one side of the heart or the other. A pacemaker may alleviate the problem.
inferior point of the heart is the
apex
digitalis drugs
are very old, but very good, drugs that are used for congestive heart failure. These drugs are called cardiotonic because they increase the strength of the heartbeat and also slow the beat so the heart can recover. A diuretic drug is called a "water pill" by nonmedical people. Again, there are several categories of diuretics, depending on their strength, manner of administration, or method of working to eliminate excess water from the body by way of increasing urine output. Like digitalis, a nitrate drug is very old but very useful. The nitrates treat angina pectoris by opening the coronary arteries. Aspirin is useful in small doses, for people not allergic or sensitive to aspirin, in helping to prevent blood from forming clots. Nitrate drugs, such as nitroglycerin, are placed under the tongue where they dissolve and are quickly absorbed into the blood.
blood tests
blood tests are crucial when diagnosing chest pain. Cardiac enzymes and troponin levels rise when myocardial cells die. A lipid profile test determines the levels of HDL and LDL in the blood. HDL is the "happy" or good cholesterol level that should be high, while the LDL is the "lousy" or harmful cholesterol level that should be low to be healthy. A C-reactive protein (CRP) test reveals the presence of inflammation in the body. Inflammation of blood vessels can result from inflammation anywhere else in the body. Inflamed coronary blood vessel walls become rough, which is a good place for a blood clot to form, possibly leading to a myocardial infarction.
Heart Layers The heart is a pump and it takes muscle tissue to make this pump work. This specialized tissue is called the ____________, which is made of cardiac muscle cells. With so much blood continuously flowing through the heart, it is important that the lining of the heart is very smooth and the endocardium is this smooth layer. Around the outside of the heart is the PERICARDIUM, which is composed of two layers, like the pleura of the lungs. And also, like the pleura, the two layers of the pericardium create a small amount of pericardial fluid between them, which prevents friction as the heart beats.
myocardium
The arteries are not the only blood vessels to develop medical conditions. The veins too can cause pain and possibly contribute to a fatal condition. Phlebitis and thrombophlebitis are potentially serious conditions, as a blood clot may dislodge and travel to the lungs, threatening a person's life. Remember the saphenous vein? This is the one that is frequently the site of thrombophlebitis. Although varicose veins are not a fatal disorder, they can cause considerable pain and disfigurement. Whether caused by pregnancy, standing for long periods of time, sitting at desk jobs, or crossing the feet or legs for a long time, the dilation of varicose veins cannot be reversed.
persons with hyperlipidemia may have an elevated cholesterol level, elevated triglyceride level, or both. These elevated blood levels can contribute to the development of peripheral artery disease (PAD). A diagnostic sign is claudication, pain in the calf of the leg while walking. Raynaud's disease, a type of peripheral vascular disease (PVD), produces pain in the fingers and toes due to arterial spasms.
The heart is divided into right and left sides by its dividing wall or
septum
antihypertensive drugs
which all work to reduce blood pressure, but in different ways. Angiotensin-converting enzyme (ACE) inhibitors interfere with the stress response, thus dilating blood vessels and reducing blood pressure. Beta-blocker drugs are useful antihypertensives as well as a treatment for angina. Calcium channel blocker drugs are another category of antihypertensive drugs. This type can also be used for angina as well.
