Time Is Important When Treating an Acute Heart Attack

The first few hours are critical

Senior with Chest Pain
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An acute heart attack (also called a myocardial infarction, or MI) is a medical emergency. Having an MI means that one of your coronary arteries has become suddenly blocked, and the heart muscle supplied by that artery is beginning to die. Early and aggressive medical therapy is necessary to stabilize your cardiovascular system and to prevent or mitigate long-term complications from the heart attack.

The Immediate Priorities of Acute Heart Attack

The first priorities after you arrive at the hospital with a possible MI are:

  • To make sure your vital signs (pulse and blood pressure) are stable
  • To prepare to deal with life-threatening conditions that may appear (such as ventricular fibrillation)
  • To decide whether or not you're actually having an MI

Diagnosing the most severe form of a heart attack — the ST-segment elevation myocardial infarction (STEMI) — is usually pretty easy for the doctors to do. It is done by looking for characteristic changes on an ECG.

If you are having the less severe form of MI, the non-STEMI (which generally means that the artery is not quite completely blocked), the diagnosis may require more testing — especially the measurement of elevations in cardiac enzymes, proteins released into the bloodstream by damaged cardiac muscle cells.

If it turns out that you are having a STEMI, immediate steps must be taken to relieve the blockage and to get the blood flowing through the coronary artery once again.

How Is the Blockage Treated?

There are two general methods for opening a blocked coronary artery: thrombolytic therapy and angioplasty with stenting.

Thrombolytic therapy consists of giving drugs (the so-called "clot-busters," such as Activase (t-PA), streptokinase, urokinase, or anistreplase), which act rapidly to dissolve the blood clot that has blocked the artery. Studies have shown that approximately 50 percent of occluded arteries can be opened by giving these drugs early in the course of a heart attack and that patients whose arteries are opened end up with significantly less heart damage and a significantly better chance of long-term survival.

In every study, the earlier the drug is given, the better the chances of success. The best results are obtained within the first three hours; relatively satisfactory results are seen between three to six hours; and some benefit is seen up to 12 hours, with little or no benefit after that.

The major side effect of thrombolytic therapy is bleeding, and this form of therapy should not be used in patients who are at relatively high risk of bleeding (for instance, if you had recent surgery, have a history of stroke due to brain hemorrhage, or have very high blood pressure).

Using angioplasty and stenting instead of thrombolytic drugs is now generally felt to be more effective in successfully opening a blocked coronary artery during an acute MI. Rapid angioplasty and stenting are successful in opening the blocked artery about 80% of the time. The disadvantages of this approach are that it is an invasive procedure, and unless the hospital is gearing up to perform emergency angioplasty rapidly and efficiently, the opening of the blood vessel may be accomplished more quickly with thrombolytic therapy.

The main point, no matter which method is used, is to open up the occluded vessel as rapidly as possible. This being the case, choosing between thrombolytic therapy and angioplasty should generally be based on circumstances.

Most cardiologists will opt for angioplasty if their catheterization lab can be rapidly mobilized, and experienced personnel are readily available. This invasive approach would also be chosen if there is a good reason to avoid thrombolytic therapy in your case.

On the other hand, if there is likely to be a substantial delay in performing angioplasty, or if there is a good reason to avoid performing an invasive procedure, then thrombolytic therapy would be the better choice.

Both methods can be highly effective if given rapidly enough. The most important thing is not which method is used, but to act quickly. Time is of the essence, and the method chosen should usually be whichever method is likely to open the artery more rapidly.

In addition to getting the blocked artery opened up as quickly as possible, there are several other treatments that need to be given during an acute MI.

What Other Therapies Should Be Given During an Acute Heart Attack?

In addition to acting quickly to open up the occluded vessel and restore blood flow to your heart muscle, several other measures should be taken in treating you during an acute MI. These include:

Aspirin: Taking an aspirin (one-half to a whole uncoated adult aspirin, chewed or crushed) as soon as possible whenever an MI (or any form of acute coronary syndrome) is suspected can significantly improve outcomes. Aspirin works by decreasing the "stickiness" of the blood platelets and thus retarding the growth of the blood clot that is causing the MI.

Heparin: Giving intravenous heparin or another blood thinner during the first 24 hours of an acute heart attack probably reduces long-term mortality. The anticoagulant drugs, of which heparin is one, help to prevent the formation of a new blood clot.

Beta blockers: Beta blockers, drugs that block the effect of adrenaline, significantly improve the survival of patients with MIs, and they should be given to all patients unless there is a strong reason not to (such as lung disease, severe heart failure, or very slow heart rates). These drugs are usually initiated the day after the heart attack.

ACE Inhibitors: Angiotensin converting enzyme (ACE) inhibitors have been shown to significantly improve the outcome of patients who have very large heart attacks or signs of heart failure. These patients should be started ACE inhibitors during the first 24 hours after a heart attack. ACE inhibitors may also be beneficial in patients with less severe heart attacks.

Statins: Therapy with statins should be started in all patients with an MI prior to hospital discharge, and probably as early as possible after the onset of the heart attack. Statins appear to improve survival after an MI regardless of cholesterol levels, probably by reducing inflammation or stabilizing coronary artery plaques in some other way.

After the First Critical 24 Hours

The first 24 hours are critical. Getting medical help as rapidly as possible is essential to preventing a cardiac arrest, preserving your heart muscle, and preventing further blood clots from forming in your coronary arteries.

But even after you have successfully negotiated that first critical day, there is still a lot of work to do. A heart attack is not simply an isolated event that, once endured, can then be forgotten. Truly surviving a heart attack requires an ongoing effort on your part, and on the part of your doctor.

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Article Sources
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  • Cannon, CP, Hand, MH, Bahr, R, et al. Critical pathways for management of patients with acute coronary syndromes: an assessment by the National Heart Attack Alert Program. Am Heart J 2002; 143:777.