Nothing to say, yet
Transcription
This chapter discusses the care of cardiac patients, particularly focusing on interventional cardiology. Interventional cardiology involves procedures to assess the function of the heart, such as heart catheterization and angioplasty. These procedures have revolutionized the treatment of coronary artery disease, allowing many patients to avoid open-heart surgery. The chapter also covers the care of patients with acute myocardial infarction (heart attack) and heart failure. It explains the symptoms and diagnostic tests for heart attack, as well as the importance of prompt treatment. Additionally, it defines heart failure and highlights the importance of managing it effectively. Chapter 2 Cardiac Care. This chapter is about the care of a cardiac patient. Cardiologists care for many types of cardiac patients both young and old. This chapter is devoted to a discussion of interventional cardiology in which cardiologists specialize in doing procedures that assess the function of the heart. Two main cardiac diseases and their treatment are also discussed. The care of the acute myocardial infarction patient is discussed along with the care of the patient in heart failure. Interventional cardiology. Doctors who do interventional cardiology use catheters and similar devices to evaluate the heart for vascular or structural abnormalities. The most common procedure done by interventional cardiologists is a heart catheterization with or without an angioplasty procedure to treat blockages of the coronary blood vessels. A cardiac catheterization starts with the placement of a large catheter in the femoral artery although other arteries can be used. The catheter travels to the heart and dye is injected that will show up on x-ray. A real-time x-ray evaluation of the coronary arteries can be done under fluoroscopy. The radial artery is sometimes used and is more comfortable for the patient. Interventional procedures have radicalized the treatment of the cardiac patient so that many patients can be treated for coronary artery disease without having to go through open-heart surgery and all the complications and post-operative recovery that goes along with such surgeries. Angiography and angioplasty have become the gold standard of treatment for the patient with acute myocardial infarction and the patient with blocked coronary arteries in the absence of an acute myocardial infarction. Clots can be extracted from blocked coronary arteries and stents can be placed after balloons are inflated to open the blocked artery. The definition of angioplasty is any procedure used to dilate a blocked artery or a blocked vein. It is most commonly used on coronary arteries but can be used in peripheral arteries. Other interventional procedures include the valvuloplasty in which a catheter and balloon are used to dilate damaged valves in the heart. Congenital heart diseases can be corrected without open surgery including the correction of atrial septal defects, ventricular septal defects, and repair of a patent ductus arteriosus. Valves can be placed percutaneously. This can be done to replace the aortic valve, the pulmonary valve, or the mitral valve. If the valve needs repair instead of replacement, this can be done percutaneously as well. Catheters can be introduced into completely blocked coronary arteries and can remove thrombi that have blocked the artery so that circulation can rapidly be restored. Care of the patient with an acute myocardial infarction. An acute myocardial infarction or heart attack involves the irreversible cell death of cells in the heart muscle secondary to lack of oxygen. The most common cause of an acute myocardial infarction is the blockage with a thrombus of a major coronary artery that has previously become narrowed by hyperlipidemia. The patient with an acute myocardial infarction generally has the acute onset of chest discomfort, malaise, and fatigue. There may be shortness of breath or radiation of pain to the neck, jaw, shoulder, or left arm. The pain does not go away with rest and is usually described as a squeezing, burning, sharp, or aching pain in the sternal area. Some patients have symptoms suggestive of dyspepsia with epigastric pain and indigestion. The patient often has an increased heart rate secondary to the activation of the sympathetic branch of the sympathetic nervous system. There may be irregularities of the pulse secondary to ventricular arrhythmias. Single ectopic beats may be present along with the possibility of an accelerated idioventricular rhythm, ventricular tachycardia, atrial flutter, atrial fibrillation, or some other type of supraventricular arrhythmias. The blood pressure is usually elevated because of constriction of the peripheral arteries. If there is a severe left-sided myocardial infarction or a right-sided myocardial infarction, the patient may have hypotension or cardiogenic shock. The respiratory rate may be increased because of anxiety or congestion in the lungs. Frothy sputum production can occur with coughing and wheezing from bronchoconstriction. Laboratory studies can be done to identify elevation of the myocardial enzymes. There are several cardiac biomarkers and enzymes that could be elevated, but the gold standard for acute myocardial infarction is due to a troponin level, which is extremely sensitive but accurate. Troponin is found in the serum only when there is an actual necrosis of myocardial tissue. A complete blood cell count can be done to check for anemia or white blood cell changes. A comprehensive metabolic panel may be done along with a lipid profile. The electrocardiogram is an invaluable tool in the initial evaluation and management of a patient suspected of having an acute myocardial infarction. It can accurately confirm the diagnosis in about 80% of documented myocardial injuries. Patients with a confirmed heart attack or highly suspected heart attack can have a coronary angiography, which can be both diagnostic of an acute myocardial infarction and can improve the outcome of an acute myocardial infarction. Patients with chest pain seen by the emergency medicine personnel should have an immediate intravenous access performed along with oxygen, particularly if the oxygen saturation is less than 90%. Aspirin should be given in the ambulance along with nitroglycerin sublingually or by spray. An electrocardiogram should be done urgently and sent by telemetry to the emergency room doctor if possible. Patients with continued chest pains should receive additional nitroglycerin and a beta blocker to control heart rate and decrease the oxygen demands on the heart. If the patient has had their symptoms for less than 90 minutes, they should be taken to the angiography department to have an emergency cardiac catheterization and possible angioplasty. If the patient has had their symptoms longer than two hours, then emergency fibrinolysis should be performed. Patients with EKG evidence of FT segment elevation are not good candidates to receive thrombolytic agents but should have an angioplasty as soon as possible after admission. After emergency department treatment, the patient should be transferred to the coronary care unit for further management. Things like emergency defibrillation, the giving of thrombotic agents and the use of angioplasty have been found to decrease the extent of the myocardial infarction by re-canalizing arteries that have become blocked. This can salvage myocardial tissue that is ischemic but not yet necrotic. The diagnosis of acute myocardial infarction is made when the troponin level is elevated and there is evidence of ischemia by symptoms, FT segment or T wave changes, the new onset of a left bundle branch block, Q waves on EKG, imaging showing loss of wall motion movement or angiogram documented thrombus in the coronary arteries. An acute MI can be diagnosed in cases of sudden death with a history suggestive of myocardial hypoxia. Acute coronary syndrome is defined as a spectrum of cardiac conditions that happen because of ischemia or infarction of myocardial tissue from a sudden loss of circulation. There can be non-ST segment myocardial infarctions and ST segment elevation myocardial infarctions. The patient is defined as having unstable angina if they have cardiac ischemia symptoms, no ST segment changes and a lack of documented cardiac ischemia by biomarker evaluation. Anytime there is elevation of biomarkers such as troponin, cardiac necrosis can be proven. The clear majority of acute myocardial infarctions come from atherosclerosis. About 90% of acute myocardial infarctions are the direct effect of a thrombus in a coronary artery. The artery is usually already narrowed from atherosclerotic disease and a plaque may or may not have ruptured. The rupture of a plaque can lead to platelet activation, the aggregation of platelets and the activation of the coagulation pathway. This can cause vasoconstriction which worsens the cardiac ischemia already bad from clot formation. Acute myocardial infarction can happen in the absence of atherosclerosis. Things like vasculitis, heart trauma, vasospasm, coronary artery emboli, drug use, arteritis, aneurysms of the coronary arteries, hyperthyroidism, heavy exertion or severe anemia can lead to cardiac ischemia significant enough to cause necrosis of cardiac tissue. There can be hypoxia from an aortic dissection, pulmonary problems and carbon monoxide poisoning. Rarely, children can have an MI from certain uncommon pediatric diseases. Patients with an acute myocardial infarction have a 30% chance of death. Half the time, the death occurs before the patient reaches the hospital. About 5 to 10 percent recover initially but die in the year following their heart attack. Half of all MI patients return to the hospital with another event or complication of their MI in the year following the MI. Patients do better if they have early reperfusion or fibrinolysis as soon as they are identified as having an acute MI. Patients with good ventricular function do better and patients who receive aspirin, beta blockers and ACE inhibitors after their heart attack have a better prognosis. A poor prognosis is associated with concomitant diabetes, other vascular diseases, delayed reperfusion, advanced age. Patients with ongoing depression have a poor prognosis. Poor left ventricular function after the event and evidence of congestive heart failure after the event. Patients with ongoing depression have a poor prognosis. Care of the heart failure patient. Heart failure is defined as having poor pump function of either the left or right ventricles or both. The heart dysfunction is usually due to muscle damage from an acute MI or ongoing ischemia. Rarely a patient will present with heart failure without having had a previous myocardial infarction. Overall heart failure is common and is the leading cause of hospitalization in patients older than 65 years of age. Patients suspected of having heart failure should have a blood test for B-type natriuretic peptide or BNP. This is found to be elevated in most cases of heart failure. If the heart failure has a sudden onset, the patient should have a trans thoracic Doppler echocardiogram to evaluate the function of the heart. After the patient has been stabilized and is in the intensive care unit, they need to have beta blocker treatment unless the heart rate is less than 50 beats per minute or they have EKG evidence of a second or third degree atrioventricular block. Patients with shock should not have beta blocker treatment. The patient should be stable prior to receiving beta blocker therapy. Angiotensin converting enzyme inhibitors or ACE inhibitors should be given to the patient to maintain a low blood pressure. Aldosterone antagonists should be started if there is evidence of reduced left ventricular ejection fraction. If the patient can't tolerate an ACE inhibitor or angiotensin receptor blocker, they should be given an aldosterone antagonist. Upon admission to the coronary care unit, all patients should have a complete physical, chest x-ray, and electrocardiography. Blood testing for B-type neutriuretic hormone should be done to evaluate the severity of the heart failure. The higher the level, the greater is the degree of heart failure. A Doppler echocardiogram can establish areas of wall movement abnormalities or other cardiac anomalies. The treatment of acute heart failure involves giving intravenous diuretic therapy to reduce the workload of the heart. Opiates should be avoided as this can depress the cardiorespiratory system. Patients already on a diuretic should receive an increased dose of the same or different diuretic. Renal function, urine output, and weight are evaluated regularly during diuretic treatments. Nitrates are not necessary unless there is evidence of ongoing ischemia. Nitrates should also be used if there is severe hypertension or regurgitation of the aortic or mitral valves. Sodium nitroprusside should be avoided, as well as any vasopressor medications. Vasopressors should only be used if there is evidence of reversible cardiogenic shock. The patient should be artificially ventilated in cases of respiratory failure, physical exhaustion, or decreased level of consciousness. Unless these things are present, the patient generally does not have to be intubated and can just receive supplemental oxygen to maintain normal oxygenation. Patients with heart failure secondary to severe aortic stenosis should be considered candidates for aortic valve replacement as a treatment for their heart failure. This can involve replacement by means of a catheter rather than open-heart surgery. Patients with evidence of ischemia should be considered candidates for revascularization. If mitral valve regurgitation seems to be the cause of the heart failure, then a mitral valve replacement through a catheter should be considered. Those patients with reversible heart failure or who are candidates for a heart transplant may be placed on mechanical assist devices. Some patients fail to adequately respond to diuretic therapy, either because they have severe renal insufficiency or are having poor renal perfusion because of heart failure. In such cases, the patient can be started on low-dose dopamine therapy to increase the vasodilation of the renal arteries, improving their blood flow. Thiazide diuretics may be added to improve diuresis and decrease fluid volume, thereby reducing the work of the heart. If the patient has heart failure because of low perfusion of the cardiac muscle, they may be candidates for an intra-aortic balloon counterpulsation pump. This is used as an alternative to the use of intravenous inotropic drugs to decrease the work of the diseased heart. It can correct left ventricular systolic failure and resultant hypoperfusion of the systemic vasculature. There are multiple drugs the heart failure patient can be started on to improve heart function or to decrease the work of the heart. Almost any kind of antihypertensive medication can be tried, including calcium channel blockers, beta blockers, diuretics, ACE inhibitors, angiotensin receptor blockers, or peripheral vasodilators. Digoxin is often given to increase cardiac output in patients with diffuse hypofunction of the heart muscle. Surgical procedures that can be attempted in the treatment of heart failure include coronary bypass surgery or angioplasty with stent placement if there is coronary artery disease. Valves can be repaired or replaced if they are dysfunctional. A door procedure can be done in which a thinning area of heart muscle is removed to prevent a cardiac aneurysm. Left ventricular assist devices can be used when the heart failure is expected to be temporary. In rare cases, a person may need a heart transplant if the heart is too diseased and the patient is otherwise healthy and not elderly. Key takeaways. Interventional cardiology involves using catheters to evaluate the coronary arteries, repair blockage to the coronary arteries, or repair damaged valves. Patients with a heart attack often present with typical signs and symptoms of cardiac ischemia but can present atypically with epigastric pain or indigestion. Half of all myocardial infarction deaths happen prior to arrival at the emergency room and are due to a lethal cardiac arrhythmia. Myocardial infarction patients are treated with aspirin therapy. Patients with a short duration of symptoms are offered angioplasty to correct the occlusion. Patients with a long duration of symptoms are given thrombolytic therapy. Most deaths from myocardial infarction are due to an arrhythmia but some are due to secondary pump failure. Heart failure patients can be identified by echocardiogram, chest x-ray, clinical findings, and measurement of the B-type natriuretic hormone which is elevated in cases of heart failure. Most heart failure patients can be treated with diuretic therapy, digoxin to improve pump function, beta blockers to reduce the work of the heart, and anti hypertensive medication. Quiz. Number one. A patient presents to the emergency department with classical signs and symptoms of a heart attack of one hour's duration. The EKG shows no ST segment elevation. The troponin level is elevated. How should this patient be managed? A. Aspirin therapy with serial cardiac enzymes to document myocardial necrosis. B. Emergency angiogram and possible angioplasty. C. Tissue plasminogen activator by intravenous means. D. Left ventricular assist device. Answer. B. The patient has presumptive myocardial infarction by history and elevated troponin level. As the duration of symptoms is less than 90 minutes, they should be offered angioplasty to reverse any ischemia that may otherwise go on to necrosis. Number two. Most interventional cardiologists use a catheter to evaluate and treat the heart. The catheter is usually inserted where? A. The radial artery. B. The left subclavian vein. C. The femoral artery. D. The femoral vein. Answer. C. Most catheters for angioplasty are initially placed in the femoral artery. Sometimes the radial artery is used. Number three. What is the gold standard blood test to be done to confirm cardiac muscle necrosis? A. CPK MB. B. CPK MM. C. SGOT. D. Troponin. Answer. D. All of these can be elevated in myocardial necrosis except the CPK MM level which originates in non cardiac muscle. The troponin level is the best of coronary muscle necrosis and is the test most often used to evaluate an acute myocardial infarction. Number four. Why is aspirin a standard of care in acute myocardial infarction patients? A. It causes the blood to be thinner decreasing clot formation. B. It helps dissolve coronary artery blood clots. C. It prevents platelet aggregation decreasing further clot formation. D. It negatively feeds back on the coagulation system of the body. Answer. C. Aspirin is given to myocardial infarction patients because it prevents platelet aggregation decreasing further clot formation. Number five. Which EKG finding is pathognomonic of cardiac necrosis? A. Frequent premature ventricular beats. B. Atrial fibrillation. C. ST segment elevation. D. ST segment depression. Answer. C. ST segment elevation on electrocardiogram is pathognomonic of cardiac necrosis. The other findings may be present in the absence of necrosis of the cardiac muscle. Number six. The patient presents to the emergency department with chest pain suggestive of cardiac ischemia, a negative EKG, and a negative troponin elevation. How should they be treated? A. They should receive aspirin, nitroglycerin, and be admitted for probable myocardial infarction. B. They should have serial EKGs to evaluate for progression of their disease as they are probably going to have changes suggestive of an MI in the near future. C. They should be sent to interventional cardiology for angiogram and possible angioplasty as they likely have unstable angina. D. They should receive tissue plasminogen activator to prevent a completed myocardial infarction. Answer. C. The patient has clinical evidence of unstable angina. A myocardial infarction can be averted if the patient has a successful angioplasty procedure. Number seven. Heart failure patients often receive diuretic therapy. Why is this done? A. It increases renal perfusion. B. It decreases blood volume, decreasing the work of the heart. C. It lowers blood pressure, which helps strengthen the heart. D. It decreases preload of the heart. Answer. B. Diuretics decrease the total blood volume, thereby decreasing the work on the heart. Number eight. Heart failure patients often receive beta blocker therapy. When is beta blocker therapy not recommended? A. EKG evidence of ST segment elevation. B. First-degree atrioventricular block. C. Tachycardia. D. Third-degree atrioventricular block. Answer. D. Beta blocker therapy is recommended in all cases shown except for third-degree atrioventricular block. Other cases in which it is not recommended include shock, second-degree atrioventricular block, and heart rate less than 50. Number nine. What imaging test is most likely to yield valuable information in cases of heart failure? A. CT scan of the chest. B. PA chest X-ray. C. Doppler echocardiogram. D. Angiogram. Answer. C. A Doppler echocardiogram is recommended in cases of heart failure as it can tell if there are structural abnormalities of the heart and can tell the pump functioning of the heart. Number ten. When do heart failure patients receive a left ventricular assist device? A. When their ejection fraction is extremely low. B. When their pump function is low enough to cause hypotension. C. When their heart failure is expected to reverse itself. D. When they have a valvular problem causing their heart failure. Answer. C. Heart failure patients can receive a left ventricular assist device when their heart failure is expected to be temporary.
