HEART DISORDERS
Conditions Affecting the Heart’s Rhythm
The heart may be affected by normal physiologic factors (e.g., sleep, exercise) and medications (digoxin, calcium channel blockers, beta blockers), which can cause a disturbance in the regularity of the heartbeat. In some cases, the irregularity can be the result of a disturbance in the heart’s electrical conduction system.
Cardiac Dysrhythmias
Dysrhythmia, an irregularity in the heartbeat’s rhythm, is a complication of numerous disorders, such as MI, electrolyte imbalances (especially, potassium), and other heart and circulatory disorders. It may also result from severe trauma or electric shock. (Commonly, the term arrhythmia is used in place of dysrhythmia. Technically, arrhythmia means “without heartbeat” [i.e., cardiac standstill]. Dysrhythmia is the correct term, meaning “irregularity in heartbeat.”) Dysrhythmias are typically categorized according to their origination sites in the atria, septum, or ventricles. Abnormal electrical impulses occur in the SA node, AV node, bundle branches, or the Purkinje’s network.
Three common dysrhythmias are:
• Sinus tachycardia: Heartbeat is greater than 100 beats per minute. (This rate is normal in children.) It can be present postoperatively and in instances of high fever, decreased oxygenation, excessive fluid or blood loss, extreme emotion, overactive thyroid, or strenuous exercise.
FIGURE 81-6 · Electrocardiogram (ECG) tracings of ventricular dysrhythmias. With premature ventricular contractions (PVCs) (top tracing), the QRS complex is distorted because the impulse is originating from an ectopic focus. Because the ventricle usually cannot repolarize sufficiently to respond to the next impulse that arises in the sinoatrial node, a PVC frequently is followed by a compensatory pause. With ventricular tachycardia (middle tracing), the ventricular rate is extremely rapid, ranging from |00 to 250 beats per minute; P waves also are not seen. In ventricular fibrillation (bottom tracing), there are no regular or effective ventricular contractions, and the ECG tracing is totally disorganized.
• Sinus bradycardia: Heartbeat is less than 60 beats per minute. (This rate may occur in athletes normally.) Sinus bradycardia can occur with digitalization (administration of digoxin) or it can be a symptom of heart block (an abnormal situation discussed below).
• Premature ventricular contraction (PVC) is an irregularity in the heart’s ventricular rhythm. As the name indicates, a PVC is a contraction that is initiated in the ventricles that is premature. In other words, it occurs before the normal SA node-conducted beat. PVCs can be relatively benign; indicators of early cardiac problems; or progress to more malignant ventricular dysrhythmias.
Figure 81-6 depicts a few more common dysrhythmias.
Atrioventricular Heart Block
Heart block is not a disease in itself, but is associated with many types of heart disease, especially diseases of the coronary arteries and rheumatic heart disease. In atrioventricular (AV) heart block, heart contractions are weak and lack sufficient force to send blood from the atria into the ventricles. Pulse rate may be as low as 30 beats per minute.
An electronic pacemaker may be used to provide external stimulus to the heart. The electronic pacemaker stimulates heart contractions by means of wires connected to electrodes, which are inserted into the heart (Fig. 81-7). A pacemaker may be external, which is generally temporary, or internal, which is considered necessary for life-sustaining cardiac rhythms.
FIGURE 81-7 · Pacemaker therapy. The pacemaker delivers an electrical impulse to the heart at specified intervals, causing the heart to beat.
Clients who experience frequent difficulty with heart contractions may have a permanent pacemaker implanted. The problem with contractions may be result from a lack of initiation of electrical activity (e.g., heart block) or uncontrolled episodes of irregular or paroxysmal cardiac electrical conduction (e.g., assorted cardiac dysrhythmias) in either the atria or ventricles. A portable pacemaker about the size of a cellular phone or an MP3 device is used in the clinical setting. If a permanent pacemaker is indicated, the surgeon implants the pacemaker pack underneath the client’s skin, usually in the subclavian or lower abdominal area.
Some clients can discontinue use of a pacemaker gradually, depending on the heart’s rhythm and etiology of the cardiac disruption. Other clients cannot live without it. For internal pacemakers, a battery replacement may be required every 5 to 10 years, which can often be done in an outpatient setting.
Nursing Alert Use of rubber (latex) gloves is recommended when handling pacemaker terminals or generators. Rationale: Care is necessary to prevent an electrical shock, which could upset the heart rate or stop the pacemaker. First, be sure to determine latex allergy in the client.
The critical observation period is 3 days after the pacemaker’s insertion. After a client has had a pacemaker implanted, do the following:
• Carry out routine postoperative care.
• Check all electrical equipment in the room for grounding.
• Carefully check the client’s pulse, including cardiac rhythm and rate. The heart rate should correspond to the setting on the pacemaker. Report any deviation at once.
• Observe for neck vein distention or muffled heart sounds, which could indicate cardiac tamponade. These are serious signs that must be reported at once.
• Use sterile technique and keep the incision site clean to prevent infection.
• Provide active or passive range-of-motion exercises and incentive spirometer treatments to prevent complications.
• Reassure the client, who may find adjusting to dependence on the pacemaker difficult.
Nursing Alert If the client with a pacemaker notices any symptoms of dizziness or light-headedness, instruct him or her to move at least 6 feet away from the source of any electrical interference.
A client with a pacemaker should wear a medical alert identification tag or bracelet (MedicAlert). Teach the client how to count the pulse and to report any deviation at once. Telecommunication or teletransmission of the ECG is used for clients with pacemakers. At a prescribed time and frequency, a client uses a special modem to transmit heart rate, rhythm, and battery life to a central location (usually, a hospital or physician’s office), where heart rate and rhythm are transformed onto ECG paper for interpretation and follow-up.
Fibrillation
Fibrillation refers to a quivering of muscle fibers. A disorganized twitching of atrial muscles is known as atrial fibrillation. It is sometimes seen in clients with atherosclerosis and rheumatic heart disease. The pulse is irregular because coordination between the atria and ventricles is interrupted. Treatment depends on the cause, but unless the condition is life threatening, the physician usually prescribes digoxin, beta blockers, and calcium channel blockers to slow the transmission of electrical impulses from the atria to the ventricles. Anticoagulants may be given to prevent blood clots. Sometimes it is necessary to perform cardioversion (changing of the cardiac dysrhythmia, electrically or through medication administration). If all else fails to return the rhythm to normal, atrial ablation may be used. This procedure uses a catheter to determine the location of the abnormality; then the diseased tissue is destroyed.
Ventricular fibrillation is a twitching of the ventricular muscles of the heart. The rhythm is totally disorganized, and blood does not circulate. It is the most dangerous type of fibrillation and is a medical emergency. It is fatal if untreated because it leads to cardiac arrest.
Defibrillation. Treatment for ventricular fibrillation is electrical defibrillation, which is done by a physician or a specialized critical care nurse. In defibrillation, a high-voltage electrical current is passed through the client’s body in an attempt to shock the heart back into a regular beat. The electrical current necessary for cardioversion of atrial fibrillation is much less than that needed for ventricular fibrillation.
Nursing Alert During electrical defibrillation, everyone present must be careful not to touch the client or the bed; doing so will lead to shock and, possibly, injury
If the client experiences cardiac arrest (asystole), external cardiac compression and cardiopulmonary resuscitation (CPR) are necessary. In an emergency inside a hospital, perform CPR until the code team arrives to perform electrical defibrillation. In many public places, as well as hospitals, it is common to find specific locations for an automated external defibrillator (AED), which is a user-friendly defibrillation device.
Implantable Cardioverter-Defibrillator. The implantable cardioverter-defibrillator (ICD) or automatic implantable cardioverter-defibrillator (AICD) is an effective device in the management of lethal ventricular dysrhythmias for clients whose condition cannot be managed by drug therapy.
The ICD is a lightweight (1/2 lb) lithium battery-powered pulse generator. It is surgically implanted under the skin, usually in the pectoral or abdominal region (similar to permanent pacemaker placement). Wires (called leads) placed in the heart sense the heart’s rate and rhythm. Defibrillating heads attached to the heart deliver an electrical shock to the heart muscle when a ventricular dysrhythmia is detected. If the first shock is unsuccessful, the ICD will deliver four to seven more shocks. The latest devices also provide backup pacing of the heart, as needed.
After placement of an ICD, the postoperative period allows for close observation of how the device responds to dysrhythmias. Individuals receive continuous cardiac monitoring during this time. Assist the client with early ambulation, monitor the wound for signs of infection, and provide information and teaching about the device.
Teach the client to lie down when he or she feels a shock from the ICD. If the client is alone when this occurs, he or she should call 911 or the physician; if someone is with him or her, the client should lie down, and the other person should call the physician. When an electrical shock is delivered, it will cause a slight tingling to the individual and to anyone who touches him or her. If the person becomes unconscious, a family member or caregiver should call 911. CPR should not begin unless four to seven shocks have been noted. All family members and caregivers will need to know how to perform CPR.
The battery on the ICD needs to be checked every 2 months. Be sure the client understands the need for wearing a tag that identifies the client as wearing an ICD.
Conditions Affecting the Heart’s Pumping Function
Congestive Heart Failure
Congestive heart failure (CHF), also known as heart failure, cardiac decompensation, cardiac insufficiency, and cardiac incompetence, means that the heart is failing and unable to do its work; it has lost its pumping efficiency. This is called decompensation. CHF is a syndrome (a group of symptoms) that affects individuals in different ways and to different degrees. The heart will try to keep up with demands made on it; treatment is aimed at helping the heart adjust to the demands placed on it. This is termed compensation. Abnormal conditions in the heart may make continued treatment necessary; otherwise, the signs of heart failure will reappear.
Congestive heart failure results from excessive strain on the heart. This may be caused by an MI, infection of valves or of heart muscle itself, blood vessel disease, HTN, renal insufficiency, congenital defects, hyperthyroidism (which speeds up heart action), cardiomyopathy, or rheumatic fever (which damages heart valves). Older people are subject to heart failure because of arteriosclerosis.
Signs and Symptoms. The main cause of right-sided heart failure is left-sided heart failure.
With left-sided heart failure, the left ventricle is not able to pump the blood out to the systemic circulation effectively. Pressure in the left ventricle increases, leading to an increase in pressure in the left atrium. As a result, blood flow from the pulmonary vessels into the left atrium decreases, causing increased pressure in the pulmonary vessels and blood congestion in the lungs (pulmonary edema). If the body cannot compensate for these changes, pressure increases in the right ventricle.
Failure of the right ventricle to pump results in increased congestion in the systemic circulation, ultimately leading to right-sided heart failure. In short, if a client has failure of one side of the heart, he or she will eventually have failure on the other side, unless treatment is successfully initiated.
The first noticeable signs of a failing heart are excessive fatigue, dyspnea, and orthopnea; the person may have to rest after walking halfway up a flight of stairs or may need two pillows at night to breathe comfortably. These initial symptoms may develop gradually and not be considered medically important as the client can rationalize that fatigue is a normal sign of aging. Nursing observations and client teaching are important considerations when fatigue is identified in seniors.
The feet or ankles may swell during the day and, although this swelling disappears overnight, it recurs as soon as the person is on the feet again (dependent edema). In addition, when a finger presses on the swollen area, an indentation is left that lasts longer than normal (pitting edema). An accumulation of fluid in the tissues may cause sudden weight gain. Other symptoms include numbness or tingling in the fingers, albuminuria (the presence of albumin in the urine), cyanosis, engorgement and visible pulsation of neck veins (referred to as jugular venous distention, which can indicate elevated central venous pressure), and engorgement of the liver, with or without jaundice. The heart attempts to compensate for this excess fluid congestion by dilation, hypertrophy, and tachycardia.
Many affected individuals develop a persistent cough, which indicates the start of pulmonary edema—the most serious symptom, which results from left-sided heart failure. When the left side of the heart pumps ineffectively, the pulmonary circuit becomes congested. Symptoms of pulmonary edema include cough, gurgling or crackling lung sounds, dyspnea, and heart palpitations. The person may sound as if he or she has asthma. Sputum may be pink and frothy or blood streaked. Acute pulmonary edema is a medical emergency and is treated with intravenous (IV) morphine sulfate, diuretics, supplemental oxygen, and a high Fowler’s position.
Diagnostic Tests. The usual tests for detecting heart disease, such as ECG, x-ray examination, echocardiography, and in some cases cardiac catheterization, are performed. Circulation time and arterial and venous blood pressure also are measured. Evaluation of urine reveals a diminished output (oliguria), elevated specific gravity, albuminuria, and the presence of blood (hemoglobinuria) and casts (tiny mineral deposits). Blood chemistry shows nitrogen retention by elevated blood urea nitrogen (BUN), uric acid, and creatinine concentrations.
Hemodynamic Monitoring. Heart pressures are increased, and a special kind of monitoring, called hemodynamic monitoring, is required. In hemodynamic monitoring, an arterial catheter, such as a Swan-Ganz catheter, is used to measure internal pressures. Placement of the catheter is an invasive procedure and is not without risk. The catheter measures the pressures in the heart and its vessels.
Medical Treatment. Treatment focuses on easing the workload of the heart. Rest, sedation, and proper diet are important. A cardiotonic glycoside (digoxin) is often used to slow the heart’s rate, increase the force of systole (an inotropic effect), and decrease the heart’s size. Digoxin is a cardiotonic glycoside that is given to slow and regulate the heart rate and to strengthen the heartbeat. Angiotensin-converting enzyme (ACE) inhibitors or other vasodilators should be added, as tolerated. These agents expand the blood vessels and decrease vascular resistance. Beta blockers can be given because they improve left ventricular function. Diuretics help rid the body of excess fluid and salts. Salt (sodium) in the diet is restricted. Fluids also may be restricted, depending on the client’s fluid balance status. If these measures are successful, systemic circulation will improve, increasing urinary output and reducing dyspnea and edema.
Nursing Considerations. Key components of nursing care include measuring intake and output (I&O) and weighing the client daily to determine the client’s fluid balance status and extent of edema. Give oxygen if the blood is not receiving enough from the lungs. The high Fowler’s position usually aids breathing.
Pressure-reducing devices often are used because the client with CHF is at risk for skin breakdown. Dyspnea and fatigue can interfere with the client’s ability to move. Plus, circulation is decreased in areas where edema is present.
Another key aspect of nursing care is administering the prescribed medications to the client and monitoring the client for the effectiveness of therapy. In Practice: Nursing Care Guidelines 81-1 highlights important areas for cardiotonic medication administration.
Nursing Alert Some medications have similar names. Look at the following list of commonly used drugs that are used to treat disorders of the circulatory system, such as hypertension, dysrhythmias, or thrombophlebitis. Note the similarities of brand names. Using the wrong drug could be lethal. Always check your medication at least three times before giving it to your client.
• carvedilol (Coreg), beta blocker
• nadolol (Corgard), beta blocker
• amiodarone (Cordarone), class III antiarrhythmic
• captopril (Capoten), ACE inhibitor
• doxazosin (Cardura), alpha-blocking agent
• diltiazem (Cardizem), calcium channel blocker
• verapamil (Calan), calcium channel blocker
• warfarin (Coumadin), anticoagulant
IN PRACTICE :NURSING CARE GUIDELINES 81-1
ADMINISTERING THE CARDIOTONIC DRUG DIGOXIN (LANOXIN)
• Remember, the first administration of digoxin will be larger (loading dose) than later doses. The dosage will gradually be decreased, until the amount needed to stabilize the heartbeat (maintenance dose) is found. If the dosage is too large, undesirable side effects will occur. When the medication slows the heart rate sufficiently the client is said to be digitalized.
• Before administering digoxin, take the client’s apical pulse for 1 full minute. Do not give the medication if the pulse is below 60 bpm (70 for a child), and report such a finding immediately Rationale: Low pulse may indicate over digitalization.
• Be alert for possible side effects and adverse reactions of digitalization, including gastrointestinal symptoms, headache, and blurred vision. The client may say that everything has a yellow appearance. Bradycardia also occurs when digoxin slows the heart too much. For this reason, count the client’s apical pulse before giving each dose. In some facilities, two nurses check digoxin dosages before giving such drugs to clients.
• If the client is discharged from the healthcare facility and prescribed digoxin, teach the client how to count the pulse rate, the symptoms of digoxin toxicity and the significance of notifying the physician of any changes or symptoms. Document all teaching.
Cardiomyopathy
Cardiomyopathy is a very serious disease that interferes with the ability of the heart to pump adequately. The heart muscle usually becomes enlarged, stretched, and weakened owing to a variety of causes. Primary cardiomyopathy cannot be attributed to any specific cause, such as HTN, CAD, heart valve diseases, or congenital heart defects. Secondary cardiomyopathy is attributed to a specific cause or disease.
The most common form of cardiomyopathy is dilated or congestive cardiomyopathy. The heart cavity becomes enlarged or dilated and usually the condition progresses to CHF. Dysrhythmias and blood clots may also be problematic because blood flows more slowly through an enlarged heart. Treatment with anticoagulants and antiarrhythmics can help. Vasodilators may be given to relax the arteries, lower the blood pressure, and decrease the workload of the left ventricle. If the disease progresses despite medical treatment, a heart transplant may be necessary.
Hypertropic cardiomyopathy, another form of the disease, is hereditary in more than half of those diagnosed. The left ventricle hypertrophies, which may decrease the flow of blood from the left ventricle into the aorta. It may also cause mitral valve leakage. Symptoms include dyspnea, dizziness, and angina. Some people have dysrhythmias. Often, a heart murmur can be heard. This form of cardiomyopathy is usually treated with a beta blocker or calcium channel blocker, antiarrhythmics, as needed, or surgical treatment if medication treatment fails.
A less common form of the disease is called restrictive cardiomyopathy. The ventricles of the heart become rigid, making it difficult for blood to flow. This form of the disease causes fatigue, dyspnea on exertion, and peripheral edema. Another disease process usually causes this type of cardiomyopathy.
