Coronary Artery Disease (CAD)

Concept of Perfusion

• Perfusion refers to the process of fluid, nutrient, and oxygen delivery to cells.

Coronary Artery Disease (CAD) Overview

• CAD is caused by impaired blood flow to the myocardium.
• It is a leading cause of death in the U.S.
• Angina pectoris is chest pain resulting from reduced coronary flow.
• Acute myocardial infarction (AMI) involves the death of myocardial cells, is life-threatening, and occurs when blood flow to part of the cardiac muscle is blocked.
• 60% of AMI deaths occur within the first hour, and 40% occur before hospitalization.

Pathophysiology and Etiology of CAD

• Atherosclerosis is the most common cause of CAD.
• Atherosclerosis is a progressive disease characterized by atheroma (plaque) formation, affecting the intimal and medial layers of arteries.
• Lipoproteins (e.g., cholesterol) and fibrous tissue accumulate.
  • High levels of LDLs and VLDLs increase risk.
  • High levels of HDLs decrease risk.
• Atheromas represent the final stage of the atherosclerotic process. -These are complex lesions consisting of lipids, fibrous tissue, collagen, calcium, cellular debris, and capillaries.
  • They can ulcerate or rupture, stimulating thrombosis.

Consequences of Coronary Artery Disease

• CAD can lead to myocardial ischemia, angina, and acute myocardial infarction.

Myocardial Ischemia

• Myocardial ischemia occurs when the tissue's oxygen supply is inadequate to meet its metabolic needs.
• It depends on coronary perfusion, which is affected by vessel occlusion, platelet aggregation, spasm of vessels and drops in BP.
• It also depends on myocardial workload, which is affected by heart rate, myocardial contractility, preload, and afterload.
• With Myocardial Ischemia:
  • Cellular ATP stores are depleted, and cells switch to anaerobic metabolism.
  • Cell membrane permeability increases, releasing histamine, kinins, and enzymes.
  • Lactic acid builds up in cells.
  • Nerve fibers in cardiac muscle are stimulated, causing pain impulses to be sent to the CNS often radiating to the upper body.
• Therapeutic strategies to reduce ischemia-related cardiac injury aim to reestablish myocardial perfusion before irreversible damage occurs.
  • Every 30-minute delay increases the risk of 1-year mortality by 8%.

Angina

• Angina is chest pain resulting from ischemia.
• Stable angina is the most common, predictable type, caused by physical exertion, exposure to cold, or stress, and is relieved by rest or nitrates.
• Prinzmetal (variant) angina occurs unpredictably, unrelated to activity, often at night, and is caused by coronary artery spasm, with or without atherosclerotic lesion.
• Unstable angina occurs with increasing frequency, severity, and duration, may occur at rest or activity, and indicates a risk for MI (myocardial infarction).
• Ischemia doesn't always cause angina.
• Class I: Mildest; doesn’t occur with ordinary activity; only occurs with strenuous, prolonged exertion.
• Class II: Develops with rapid or prolonged walking or stair climbing.
• Class III: Significantly limits ordinary physical activities.
• Class IV: Most severe; angina with rest or minimal exertion.

Acute Myocardial Infarction (MI)

• Blood flow to a portion of cardiac muscle is completely blocked, leading to prolonged tissue ischemia and irreversible cell damage (infarction = cell death).
• It is usually caused by ulceration or rupture of complicated atherosclerotic lesions.
• Lack of oxygen injures myocardial cells causing a cellular metabolism shifts to anaerobic, leading to cellular acidosis, furthering cell damage.
• Ischemia and electrolyte imbalances increase the risk for dysrhythmias.
• Stroke volume, cardiac output, blood pressure, and tissue perfusion are reduced.

Risk Factors for CAD

Nonmodifiable

• Age.
• Gender (males >45, females >55).
• Race and ethnicity including genetic and socioeconomic factors.
• Family history of first-degree relatives diagnosed at a relatively young age.

Unique to Women

• Menopause, whether natural or as a result of surgery.
• Oral contraceptive use, especially with other risk factors like smoking.

Prevention of CAD

• Focuses on modifiable risk factors: Diet, activity level, obesity, cigarette smoking, hypertension, diabetes mellitus, and hyperlipidemia.

Clinical Manifestations of CAD

• Often asymptomatic.
• Most common symptoms are angina and MI.
  • Differences can be subtle.
• Chest pain should always be assessed by an experienced healthcare professional.

Clinical Manifestations Comparison

Collaboration and Treatment Goals

• Treatment goals include relieving chest pain, reducing myocardial damage, maintaining cardiovascular stability, decreasing cardiac workload, and preventing complications.
• Long-term management focuses on slowing the progression of CAD and managing risk factors for future MI.
• Rapid assessment and diagnosis are critical ("Time is muscle").
• Treatment delays may stem from factors like age, gender, denial, limited access to medical care, solitary living arrangements, or the perception that symptoms are not serious.

Diagnostic Tests

• Subclinical (asymptomatic) CAD can be diagnosed using: C-reactive protein, exercise ECG testing, and myocardial perfusion imaging.
• AMI can be diagnosed using: Cardiac markers (creatine kinase, CK-MB; cardiac muscle troponins), CBC, ABGs, electrocardiogram, and echocardiography.

Conservative Management

• Smoking cessation.
• Diet modifications: Reducing saturated fat, cholesterol, and sodium intake; lowering LDL levels; increasing soluble fiber intake; moderate alcohol intake.
• Weight reduction if overweight or obese.
• Regular exercise: minimum of 30 minutes of moderate-intensity activity 5-6 days/week.
• Management of hypertension and diabetes.

Pharmacologic Therapy for CAD

• Drugs to lower cholesterol: used with diet and lifestyle changes, based on overall risk for CAD; consider expense vs benefit.
  • Statins (e.g., atorvastatin): First-line drug of choice, it lowers LDL.
• Drugs to treat angina:
  • Organic nitrates:
    • Short-acting (Sublingual nitroglycerin): Drug of choice for acute angina.
    • Longer-acting nitroglycerin (tablets, patches, ointment): Prescribed to prevent angina not to treat an acute attack and watch development of tolerance.
    • Common side effects include headache, nausea, dizziness, and hypotension. -Beta-adrenergic blockers (Ex: metoprolol, propranolol): First-line drugs for stable angina may be used with other meds to prevent angina.
• Drugs to treat MI:
  • Aspirin: Essential initial treatment for prevention of AMI unless contraindicated.
  • Analgesics: Sublingual/IV nitroglycerin, and Morphine sulfate in events nitroglycerin is not tolerated, also used for sedation
  • Antianxiety agents (ex: lorazepam (Ativan)) to promote rest

Pharmacologic Therapy for MI (cont'd)

• Thrombolytics (Ex: alteplase (Activase or tPA): Used when cardiac catheterization is not immediately available, early administration, use with caution.
• Antidysrhythmics: Used with altered cardiac rhythm after MI, the altered rhythm determines the drug ex: atrial fibrillation- digoxin & Symptomatic bradycardia- atropine

Surgical Interventions for CAD

• Revascularization procedures (after MI) can involve:
  • Percutaneous coronary revascularization:
  • Coronary artery bypass grafting (CABG): Uses a vein or artery section to create a connection, 90% may relieve and reduce angina but involves stopping the heart during surgery.

Lifespan Considerations

Women

• More likely to have a "silent" heart attack or present in cardiac arrest/cardiogenic shock.
• Often experience atypical symptoms like epigastric pain, indigestion, nausea, vomiting, shortness of breath, fatigue, and weakness.
• Tend to ignore symptoms, leading to worse diagnosis and treatment outcomes than men.
• Prompt diagnosis and intervention reduce mortality and morbidity.

Older Adults

• Commonly present with atypical symptoms like difficulty breathing, confusion, fainting, dizziness, abdominal pain, or cough.
• Higher prevalence of silent ischemia.
• May not seek or receive prompt treatment.
• Have a greater risk for widespread cardiac damage, complications, and death.

Nursing Actions: Implementation

• Promote balanced nutrition, assessing food intake and recommending dietary changes and refer to dietitian.
• Promote effective health maintenance by discussing risk factors, the benefits of smoking cessation, identifying sources of support and benefits of regular exercise.
• Manage acute pain with oxygen, comfort, nitroglycerin, and morphine sulfate.
• Monitor tissue perfusion, vital signs, LOC, auscultating heart and breath sounds, monitoring ECG and oxygen saturation, administering meds, and obtaining labs.
• Promote effective coping by creating caring environment/trust, acknowledge symptoms.
• Promote therapeutic regimen management by teaching about atherosclerosis and providing written medication instructions, chest pain and cardiac rehabilitation.
• Promote effective cardiac perfusion via maintaining nitroglycerin, teach medications, prophylactic, and smoking ceasing and provide oxygen.