Treating Unstable Angina and NSTEMI

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Acute Coronary Syndrome. SCIENCE PHOTO LIBRARY/Getty Images

Unstable angina and Non-ST Segment Elevation Myocardial infarction (NSTEMI) are two closely related forms of Acute Coronary Syndrome (ACS). They are both caused by a ruptured plaque in a coronary artery - and therefore, they are both treated as medical emergencies.

With either of these conditions, the doctor must rapidly administer medical therapy aimed both at stabilizing the cardiac ischemia being produced by the plaque rupture, and at stabilizing the ruptured plaque itself.

Simultaneously, it is critical for the doctor to do a rapid risk assessment to determine whether this medical therapy is sufficient to keep the heart from sustaining permanent damage - or whether a more invasive approach is required, including cardiac catheterization (generally, with the idea of placing a stent).

Initial Medical Therapy

If you have unstable angina or NSTEMI, the doctor will immediately begin intensive medical therapy to stabilize your heart.

The goals of this stabilization effort are to eliminate cardiac ischemia, and to prevent further growth of the blood clot that accompanies plaque rupture, and that obstructs blood flow.

Eliminating Acute Ischemia

Cardiac ischemia means that a portion of the heart muscle is not getting enough oxygen, and that cell death may be imminent. So it is critical to relieve cardiac ischemia.

With unstable angina or NSTEMI, several medical treatments are given immediately to stop ongoing ischemia.

These generally include oxygen, morphine (especially if pain is intense or continuous), nitroglycerin (to reduce the workload of the heart by lowering tension on the heart muscle), and beta blockers (which reduce the effect of adrenalin on the heart muscle). These steps usually will relieve most of the cardiac ischemia within minutes.

In addition, treatment with a high-dose statin is begun as soon as possible. While statins are commonly used to reduce cholesterol levels, in the case of ACS their primary benefit is apparently to help stabilize ruptured plaques and to reduce the inflammation that is a component of plaque rupture. Hence, treatment with a statin is begun in patients with unstable angina or NSTEMI regardless of their cholesterol levels.

Stopping Blood Clot Formation

Plaque rupture commonly causes a blood clot to form within the affected artery. To prevent the blood clot from growing, aspirin is given along with Plavix, and in many cases, one of the IIb/IIIa inhibitors (either Integrilin or Reopro) is given as well.

All these drugs together powerfully inhibit the blood platelets. Finally, most doctors also add a drug (either heparin, Lovenox, or Arixtra) to inhibit the thrombin clotting system. These measures, taken together, strongly reduce the risk of further blood clotting.

    Avoid the “Clot Busters”

    With a full-blown myocardial infarction (STEMI) the blood clot has essentially stopped all flow through the affected coronary artery. In patients with STEMI powerful “clot-busting” drugs (that is, thrombolytic therapy such as streptokinase) are often used to attempt to dissolve this severe clot.

    However, in unstable angina and NSTEMI - where the artery is not completely occluded by the clot - "clot-busting" drugs have been shown to increase risk without adding measurable benefit. These drugs, therefore, are not used with unstable angina and NSTEMI.

    Rapid Risk Assessment - The TIMI Score

    In addition to this medical therapy, early cardiac catheterization with angioplasty and stenting is recommended in many patients with unstable angina and NSTEMI.

    To decide whether an invasive approach to therapy is advisable, cardiologists use the TIMI score (derived by a series of clinical trials called the “TIMI trials”) to assess the patient’s odds of a good outcome with medical treatment alone.

    The TIMI score is determined by looking for the following seven clinical features:

    • Age 65 years or older
    • Presence of at least three risk factors for CHD (hypertension, diabetes, high lipids, smoking, or family history of early MI)
    • Prior coronary blockage of > 50%
    • Presence of ST segment deviation on admission ECG
    • At least two angina episodes in prior 24 hours
    • Elevated cardiac enzymes
    • Use of aspirin in prior seven days

    In patients who have have two or fewer of these seven risk factors (that is, a TIMI score of 2 or less), the outcomes with medical therapy alone is generally good. So, as long as their clinical situation stabilizes quickly with medical treatment, invasive procedures may be avoided.

    In patients with higher TIMI scores, outcomes are significantly better with immediate catheterization and stenting.

    For patients who do not have immediate invasive therapy, most cardiologists will want to do stress testing prior to hospital discharge. If there are signs of continued cardiac ischemia on stress testing despite medical therapy, invasive therapy is generally recommended.

    Hospital Discharge

    Prior to discharge, anyone with unstable angina or NSTEMI will need to be instructed on reducing their risk of future episodes. They will need careful instruction on exercise, diet, smoking cessation, maintaining optimal weight, blood pressure control, and optimization of lipid levels.

    Long-term drug therapy after unstable angina or NSTEMI will include aspirin, Plavix (for at least 6 to 12 months, and often indefinitely), beta blockers, and statins. Nitrates may be prescribed if there is any residual stable angina. A formal cardiac rehabilitation program can help patients get back to a normal activity level - and often, to an increased baseline activity level.

    Of course, patients who also have some degree of heart failure, arrhythmias, or other cardiac conditions, will require additional medical therapy.

    The schedule for returning to normal activities must be individualized. But most people who have unstable angina or NSTEMI, and who respond well to treatment, can expect to return to a normal activity level within two to three weeks after hospital discharge.

    Sources:

    Amsterdam EA, Wenger NK, Brindis RG, et al. 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation 2014; 130:2354.

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