Diagnostic Tests for Cad-hypertension
- By:Robert Baird Baird
A physician uses certain tests to assess the patient's risk of CAD, others to indicate whether he has CAD, and still others to determine if he has had an MI-a serious complication of CAD.
Blood Tests
A physician typically orders a serum lipid profile to assess the patient's risk of CAD. A total blood cholesterol level below 200 mg/dl indicates a relatively low risk of CAD. A level of 200 to 239 mg/dl indicates a moderate risk; one that exceeds 239 mg/dl indicates a serious risk of CAD.
High-density lipoprotein (HDL) and LDL cholesterollevels may help predict the risk of CAD more accurately than total cholesterol levels. An elevated LDL cholesterol level indicates an increased risk of CAD, but a high HDL cholesterol level indicates a lower risk.
A series of cardiac serum enzyme assays can confirm an MI. Total creatine kinase (CK) levels rise within 6 hours after the start of an Ml and peak in 12 to 24 hours after cardiac tissue death. When cardiac tissue dies, CK-MB isoenzymes, which are found only in myocardial cells, enter the bloodÂstream. Measuring their level can help determine the amount of myocardial damage. Cardiac troponin levels may be better indicators of myocardial damage than CK levels .
The lactate dehydrogenase (LD) level also can indicate an MI. The blood's LD level rises 24 to 48 hours after an MI and peaks in 3 to 6 days. Two of the five isoenzymes that make up LD-LD1 and LD2-appear primarily in the heart. Normally, the LD2 level is higher than the LD1 level. But when a patient has had an MI, the LD1 level is higher.
Other blood tests, such as aspartate aminotransferase and myoglobin protein levels, also may be used to detect an ML However, because these tests are not specific for MI, they aren't commonly used. With an MI, the level of serum aspartate aminotransferase, formerly called serum glutamic-oxaloacetic transaminase, rises. But because serum aspartate aminotransferase doesn't contain any heart-specific isoenzymes, the results aren't definitive. The myoglobin protein level is highly sensitive to myocardial injury, but an elevated level doesn't confirm an MI because trauma, inflammation, and ischemia also can increase the myoglobin protein level.
Signs and Symptoms of Coronary Artery Disease
Usually, CAD progresses for a long time without producing signs or symptoms. However, when CAD reduces blood flow so much that it no longer meets the body's need for oxygen, signs and symptoms appear. The most common symptom is angina. Typically, patients with CAD describe this pain as a feeling of tightness, squeezing, burning, or indigestion. The pain may radiate to the jaw, shoulders, arms, or back.
If your patient is experiencing angina, he also may develop nausea, anxiety, sweating, shortness of breath, or numbness of the arms. Angina rarely lasts longer than 15 minutes and usually can be relieved with rest or nitroglycerin.
Although most people with CAD feel pain, those with hypertension also may experience silent ischemia-cardiac ischemia without symptoms. As elevated blood pressure increases afterload, the heart must work harder to pump blood, resulting in an increased myocardial demand for oxygen. Because blockage and narrowing of the coronary arteries prevent the heightened oxygen demand from being met, ischemia develops. Over a prolonged period, the ischemia may trigger angina, or it may progress to a nontransmural myocardial infarction (MI).
A completely occluded coronary artery usually results in an MI. An acute MI causes severe chest pain that can't be relieved with rest or nitroglycerin. If your patient experiences heart failure, you may hear an heart sound or crackles.About the author:
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