Types of Acute Coronary Syndrome
Acute coronary syndrome, commonly referred to as ACS, is one of two conditions involving coronary arteries: myocardial infarction and unstable angina. The difference in the two is based mostly on a patient's electrocardiogram (EKG), which measures the electrical activity of the heart over time.
Myocardial infarctions, better known as heart attacks, are caused by an interrupted blood supply to a part of the heart. This is most commonly due to blockage of a coronary artery following a rupture of unstable fatty acids and white blood cells in an artery wall. While ST elevation is a simple indicator of a heart attack, there are also non-ST elevation instances of myocardial infarction.
Unstable angina is a heart condition marked by bursts of uncontrollable chest pain due to reduced oxygen to the heart. It is caused by a cholesterol-rich deposit on an artery wall, along with blood clotting, possibly combined with air bubbles or vessel spasms. Unstable anginas can occur in one of three instances: during rest or minimal exertion, usually lasting less than 20 minutes; within one month of onset and with severe, frank pain; or in varying time frames and a crescendo pattern, with increased severity, length and frequency. Half of all people with unstable angina show signs of massive scarring.
Symptoms & Warning Signs
A main sign of decreased blood flow to the heart is chest pain, experienced as tightness around the chest and often radiating to the left arm and left angle of the jaw. It may also be associated with sweating, nausea, vomiting and shortness of breath. Some patients experience abnormal heartbeat or anxiety. In many cases, symptoms are "atypical," with pain experienced in a variety of ways or even absent completely. Asymptomatic ACS is more common in female patients, and in those with diabetes. While chest pain is a frequent indicator of ACS, it can also indicate other medical conditions, so consult with a doctor to find the most accurate diagnosis.
Tests & Diagnosis
To distinguish ACS as the cause of a patient's chest pain, doctors may perform regular emergency tests, such as chest X-rays, blood tests and telemetry, which monitors heart rhythm. Once the condition has been labeled as ACS, doctors may perform an EKG to determine with kind of ACS the patient has. If it indicates acute heart damage, noted by an elevated ST segment, then treatment in the form of angioplasty or thrombolysis is performed immediately. In the absence of these changes, it is not possible to distinguish between unstable angina and myocardial infarction.
Doctors may also use ACI-TIPI scores to aid diagnosis. The score predicts, although crudely, which patients are likely to have myocardial ischemia, or a lack of blood flow to the heart.
Prevention & Treatment
Acute coronary syndrome usually indicates some degree of damage to the coronaries by atherosclerosis, or a buildup of fatty acids and cholesterol deposits. Primary prevention of atherosclerosis includes lifestyle habits such as healthy eating, exercises, treatment for hypertension and diabetes, avoiding smoking and controlling cholesterol levels. Aspirin has also been shown to reduce risk.
Once ACS has been diagnosed as an ST elevation myocardial infarction (STEMI), doctors may administer thrombolytics or perform primary coronary angioplasty. In thrombolytics, doctors inject medicine that destroys blood clots obstructing the coronary arteries. For primary coronary angioplasty, a flexible catheter is passed to the heart via the femoral or radial arteries to identify any coronary blockage. Once found, a blockage can be removed with angioplasty. If a lesion is causing the damage, then a stent may be used.
If there is no ST elevation, then a doctor may not know whether the patient is suffering from a non-ST segment elevation myocardial infarction (NSTEMI) or an unstable angina. Therefore, the doctor may treat empirically, with aspirin, heparin and clopidogrel (a clot inhibitor), inducing intravenous fluids if pain persists.
Twelve hours after the onset of pain, doctors may perform a blood test for cardiac muscle inhibitors called troponins. If positive, doctors will perform a minimally invasive procedure called a coronary catheterization to access the heart. If negative, doctors may administer a treadmill test. As a last resort, doctors may perform an angioplasty to mechanically widen a narrowed or obstructed blood vessel.