Saturday, January 28, 2017
Coronary Artery Disease
Introduction: In the United States, a person dies of coronary heart disease every 39 seconds. Coronary heart disease is a manifestation of atherosclerotic disease and has many modifiable risk factors. Patients with and without coronary heart disease should be advised to stop smoking, maintain normal blood pressure and cholesterol levels, exercise, achieve or maintain a normal weight, and control diabetes mellitus if present.
Pathophysiology: Coronary Heart Disease (CHD) is one of several manifestations of atherosclerotic disease, which begins with endothelium dysfunction.
• Endothelium, when normal, balances vasoconstrictors and vasodilators, impedes platelet aggregation, and controls fibrin production.
• Dysfunctional endothelium encourages macrophage adhesion, plaque growth, and vasoconstriction by recruiting inflammatory cells into the vessel walls, the initiating step of atherosclerosis.
• The vessel wall lesions develop a cap of smooth muscle cells and collagen to become fibroadenomas.
• The vessels with these lesions undergo enlargement, allowing progression of the plaque without compromising the lumen.
• Plaque disruption and thrombus formation, instead of progressive narrowing of the coronary artery lumen, is responsible for twothirds of acute coronary events.
• Plaques most likely to rupture (high-risk plaques) have a large core of lipids, many macrophages, decreased vascular smooth muscle cells, and a thin fibrous cap.
• After plaque rupture, the exposed lipid core triggers a superimposed thrombus that occludes the vessel.
• Increased thrombosis is triggered by known cardiac risk factors including elevated low-density lipoprotein (LDL) cholesterol, cigarette smoking, and hyperglycemia.
• The other one-third of acute coronary events occurs at the site of very stenotic lesions.
Risk Factors: include:
• Family history of premature paternal or sibling myocardial infarction
• Tobacco use and second hand smoke exposure increase the risk of CHD and smoking cessation reduces risk.
• High total cholesterol, high LDL, and/or low high-density lipoprotein (HDL) are independent risk factors.
• Physical inactivity
• Overweight and obesity
• Diabetes mellitus
• Typical angina is chest pain or pressure, brought on by exertion or stress, and relieved with rest or nitroglycerin.
• Atypical angina has two of the three features of typical angina; however, women with coronary artery disease report more neck, throat, or jaw pain.
• Noncardiac chest pain has zero to one of the three features of typical angina.
Diagnosis And Laboratory Workup:
• Risk factor assessment—Lipid profile and fasting blood glucose.
• Acute coronary syndrome—Cardiac-specific troponin is now preferred.
• Exercise treadmill testing
• Stress echocardiogram
• Stress thallium
Differential Diagnosis: Chest pain can be caused by several other conditions including:
• Cardiac—Pericarditis—slower onset of pain, pain aggravated by movement or inspiration, characteristic ECG changes.
• Respiratory—Pneumothorax—acute onset with shortness of breath and characteristic radiographic findings;
Pneumonia— often accompanied by fever, cough, shortness of breath/hypoxia, and/or radiographic findings; pulmonary embolism—acute onset of shortness of breath, positive ventilation-perfusion scan, or spiral CT.
• GI—Gastroesophageal reflux—related to eating, responds to H2 blockers or proton pump inhibitor.
• Musculoskeletal—Costochondritis—chest muscles tender to palpation.
1.Advise patients with coronary artery disease to stop smoking.
2. Recommend 30 minutes of physical activity 5 to 7 days per week.
3.Advise patients in weight management with a goal body mass index (BMI) of 18.5 to 24.9.7
Managing risk factors:
• Lower LDL cholesterol using lifestyle modification and HMG-CoA reductase inhibitors .
• Lower blood pressure to 140/90 or 130/80 mm Hg (with diabetes or chronic renal disease); treat patients who are post-MI with a β-blocker, thiazide diuretic, or aldosterone antagonist.
• Prescribe aspirin in patients with prior ST elevation or non-ST elevation acute coronary event or chronic stable angina. Prescribe clopidogrel alone in chronic stable angina or with aspirin in non-ST
elevation acute coronary syndrome.
• Nitroglycerin sublingual or spray for immediate relief of angina.
• Long-acting nitrates or calcium antagonists if β-blockers are contraindicated, do not control symptoms, or have unacceptable side effects.
When To Refer:
• Refer patients with positive noninvasive testing to be evaluated for cardiac catheterization.
• Consult with cardiologists and cardiothoracic surgeons to determine optimal management.
• Traditionally, patients with greater than 50% stenosis of left main, proximal stenosis of three major arteries, or significant stenosis of the proximal left anterior descending and one other major artery
have been treated with coronary bypass surgery.
• Advancements with drug-eluting stents may increase the numbers and types of patients who benefit from stenting.