Disease 101: Acute Coronary Syndromes

Acute myocardial infarction (MI), including ST-segment elevation MI (STEMI) and non-ST-segment elevation MI (NSTEMI), and unstable angina are now recognized as part of a group of clinical diseases called acute coronary syndromes (ACSs). Rupture or erosion of plaque--an unstable and lipid-rich substance--initiates almost all coronary syndromes. The rupture results in platelet adhesions, fibrin clot formation, and activation of thrombin.

Mortality is high when treatment is delayed, and almost one-half of sudden deaths caused by an MI occur before hospitalization or within 1 hour of the onset of symptoms. The prognosis improves if vigorous treatment begins immediately.

Causes

Atherosclerosis
Embolus

Risk factors

Diabetes
Elevated homocysteine, C-reactive protein, and fibrin levels
Excessive alcohol consumption
Family history of heart disease
High-fat, high-carohydrate diet
Hyperlipoproteinemia
Hypertension
Obesity
Postmenopausal status
Sedentary lifestyle
Smoking
Stress

Signs and symptoms

Angina

Burning, squeezing, and crushing tightness in the substernal or precordial chest that may radiate to the left arm or shoulder blade, the neck, or the jaw
Pain after physical exertion, emotional excitement, exposure to the cold or consumption of a large meal

Uncomfortable pressure, squeezing, burning, severe persistent pain or fullness in the center of the chest lasting several minutes (usually longer than 15 minutes)
Pain radiating to the shoulders, neck, arms, or jaw or pain in the back between the shoulder blades
Lightheadedness or fainting
Sweating
Nausea
Shortness of breath
Anxiety or a feeling of impending doom

Diagnostic tests

Electrocardiography helps determine which area of the heart and which coronary arteries are involved.
Serial cardiac enzymes and protein levels may show a characteristic rise in CK-MB, the proteins troponin T and I, and myoglobin.
Laboratory testing may reveal elevated white blood cell count and erythrocyte sedimentation rate and changes in electrolyte levels.
Echocardiography may show ventricular wall motion abnormalities and may detect septal or papillary muscle rupture.
Transesophageal echocardiography may reveal areas of decreased heart muscle wall movement, indicating ischemia.
Chest X-rays may show left-sided heart failure, cardiomegaly, or other noncardiac causes of dyspnea and chest pain.
Nuclear imaging scanning using thallium 201 or technetium 99m can be used to identify areas of infarction and areas of viable muscle cells.
Cardiac catheterization may be used to identify the involved coronary artery as well as to provide information on ventricular function and pressures and volumes within the heart

Viewing the coronary arteries

Acute coronary syndrome commonly results when a thrombus progresses and occludes blood flow through a coronary artery. This illustration shows the major coronary vessels that may be involved.

For the patient with STEMI, treatment includes the above initial interventions and also:

thrombolytic therapy (unless contraindicated) within 12 hours of onset of symptoms to restore vessel patency and minimize necrosis.
heparin I.V. to promote patency in the affected coronary artery.
a glycoprotein IIb/IIa inhibitor to minimize platelet aggregation.
an angiotensin-converting enzyme (ACE) inhibitor to reduce afterload and preload and prevent remodeling (begin 6 hours after admission or when the patient's condition is stable)
PTCA, stent placement, or CABG surgery to open blocked or narrowed arteries.

Nursing considerations

Institute continuous cardiac monitoring and frequently monitor the electrocardiogram (ECG) to detect rate changes or arrhythmias. Place rhythm strips in the patient's chart periodically according to yourfacility's policy.
Monitor and record the patient's blood pressure, temperature, and heart and breath sounds.
Explain the importance of reporting pain immediately.
Obtain a 12-lead ECG during episodes of chest pain.
Assess and record location, severity, and duration of pain.
Give prescribed analgesics and other medications.
Check the patient's blood pressure after giving nitroglycerin, especially after the first dose.
Monitor intake and output closely.
Monitor the patient for crackles, cough, tachypnea, and edema, which may indicate impending left-sided heart failure.
If the pateint has undergone PTCA, provide sheath care. Maintain strict bed rest and keep the leg with the sheath insertion site immobile. Monitor the site closely for bleeding. Check peripheral pulses in the affected leg frequently.
Provide emotional support, and help to reduce stress and anxiety.
Initiate cardiac rehabilitation, according to your facility's protocol.
Review dietary restrictions with the patient. If he must follow a low-cholesterol, low-sodium, low-fat, high-fiber diet, provide a list of foods that he should avoid. Ask the dietitian to speak to the patient and his family.
Refer the patient to a smoking-cessation program, if needed.
Thoroughly explain the patient's treatment regimen. Warn the patient about adverse reactions to drugs, and advise him to report them to his practitioner.
Refer the patient to a weight-reduction program, if needed.
Counsel the patient to resume sexual activity progressively.