Unstable Angina (Part III)
From Richard N. Fogoros, M.D.
What drugs are used to “stabilize” unstable angina?
Both the Wait and See and the Aggressive approaches involve the intensive use of medication to stabilize or eliminate the cardiac ischemia. These medications are generally aimed at either protecting the jeopardized heart muscle, or preventing further progression of the blood clot.
In the former category are beta blockers and intravenous nitroglycerin, both of which are started immediately. Beta blockers reduce the effect of adrenalin on the heart muscle, and nitroglycerin reduces the cardiac workload by lowering cardiac muscle tension. Both of these effects reduce the amount of blood flow needed by the cardiac muscle. In “clot stabilizing” category are either heparin or enoxaparin (drugs that inhibit the thrombin clotting system) and aspirin and/or IIb/IIIa inhibitors (drugs that inhibit platelets).
What is the Wait and See approach?
Using this approach, patients are carefully observed in the coronary care unit for signs of continuing ischemia. Such signs include more chest discomfort, further changes in the ECG, or continuing rises in cardiac enzymes.
If there are no further signs of ischemia, then patients are converted to an all-oral drug regimen they can continue at home. Before discharge from the hospital, a stress and thallium study is done to assess the patient’s potential for developing further ischemia. If the stress test is favorable, they are discharged to home. If, on the other hand, signs of early ischemia are seen on the treadmill test, they are sent for catheterization and angiography, in order to be evaluated for possible revascularization (angioplasty and/or stent, or bypass surgery.)
Using the Wait and See approach, approximately half the patients are discharged from the hospital without receiving catheterization.
What is the aggressive approach?
The aggressive approach begins the same way as the Wait and See approach, that is, with intensive drug therapy to stabilize the ischemia. But while this is being done, arrangements are being made to perform catheterization and angiography, with the clear goal in mind of doing angioplasty and/or stent. This procedure is performed as soon as it can be done practically.
Which approach is better?
This has been a very controversial question. Many patients do very well with the more conservative Wait and See approach to unstable angina.
What can we say about the appropriateness of the conservative approach vs. the aggressive approach? Thanks to data accumulated over the past year or two, we can say the following regarding therapy given to patients with unstable angina:
1) In patients with ECG changes and elevated troponin levels, early interventional therapy yields a significantly reduced incidence of full-blown myocardial infarction, and of death. In these patients, the Aggressive approach should now be considered as standard.
2) In patients with no ECG changes and with normal troponin levels, there is no evidence to date that aggressive early catheterization yields better results. In these patients, the Wait and See approach is entirely appropriate.
Summary
We now know that in most patients, unstable angina represents an acute deterioration in a previously stable atherosclerotic plaque. Indeed, the essential difference between unstable angina and a classic myocardial infarction is simply that in unstable angina, the acute blood clot only partially occludes the coronary artery instead of completely occluding it. For this reason, and because patients who are “stabilized” using medical therapy are now known to have a high incidence of having a classic heart attack in the near future, unstable angina probably is best thought of as being an “incomplete myocardial infarction. This fact justifies an aggressive early approach in many patients with unstable angina.
At this point in time, many doctors in many emergency rooms have not yet gotten “up to speed” in the appropriate treatment of unstable angina. They still think of unstable angina in terms of being somewhat-worse-than-usual angina, instead of being a somewhat-milder-than-usual heart attack. This is a problem. Even the Wait and See approach to unstable angina is far more aggressive than the treatment used for routine angina. Patients whose doctors who do not treat unstable angina with sufficient respect are at extremely high risk for a poor outcome.
What drugs are used to “stabilize” unstable angina?
Both the Wait and See and the Aggressive approaches involve the intensive use of medication to stabilize or eliminate the cardiac ischemia. These medications are generally aimed at either protecting the jeopardized heart muscle, or preventing further progression of the blood clot.
In the former category are beta blockers and intravenous nitroglycerin, both of which are started immediately. Beta blockers reduce the effect of adrenalin on the heart muscle, and nitroglycerin reduces the cardiac workload by lowering cardiac muscle tension. Both of these effects reduce the amount of blood flow needed by the cardiac muscle. In “clot stabilizing” category are either heparin or enoxaparin (drugs that inhibit the thrombin clotting system) and aspirin and/or IIb/IIIa inhibitors (drugs that inhibit platelets).
What is the Wait and See approach?
Using this approach, patients are carefully observed in the coronary care unit for signs of continuing ischemia. Such signs include more chest discomfort, further changes in the ECG, or continuing rises in cardiac enzymes.
If there are no further signs of ischemia, then patients are converted to an all-oral drug regimen they can continue at home. Before discharge from the hospital, a stress and thallium study is done to assess the patient’s potential for developing further ischemia. If the stress test is favorable, they are discharged to home. If, on the other hand, signs of early ischemia are seen on the treadmill test, they are sent for catheterization and angiography, in order to be evaluated for possible revascularization (angioplasty and/or stent, or bypass surgery.)
Using the Wait and See approach, approximately half the patients are discharged from the hospital without receiving catheterization.
What is the aggressive approach?
The aggressive approach begins the same way as the Wait and See approach, that is, with intensive drug therapy to stabilize the ischemia. But while this is being done, arrangements are being made to perform catheterization and angiography, with the clear goal in mind of doing angioplasty and/or stent. This procedure is performed as soon as it can be done practically.
Which approach is better?
This has been a very controversial question. Many patients do very well with the more conservative Wait and See approach to unstable angina.
What can we say about the appropriateness of the conservative approach vs. the aggressive approach? Thanks to data accumulated over the past year or two, we can say the following regarding therapy given to patients with unstable angina:
1) In patients with ECG changes and elevated troponin levels, early interventional therapy yields a significantly reduced incidence of full-blown myocardial infarction, and of death. In these patients, the Aggressive approach should now be considered as standard.
2) In patients with no ECG changes and with normal troponin levels, there is no evidence to date that aggressive early catheterization yields better results. In these patients, the Wait and See approach is entirely appropriate.
Summary
We now know that in most patients, unstable angina represents an acute deterioration in a previously stable atherosclerotic plaque. Indeed, the essential difference between unstable angina and a classic myocardial infarction is simply that in unstable angina, the acute blood clot only partially occludes the coronary artery instead of completely occluding it. For this reason, and because patients who are “stabilized” using medical therapy are now known to have a high incidence of having a classic heart attack in the near future, unstable angina probably is best thought of as being an “incomplete myocardial infarction. This fact justifies an aggressive early approach in many patients with unstable angina.
At this point in time, many doctors in many emergency rooms have not yet gotten “up to speed” in the appropriate treatment of unstable angina. They still think of unstable angina in terms of being somewhat-worse-than-usual angina, instead of being a somewhat-milder-than-usual heart attack. This is a problem. Even the Wait and See approach to unstable angina is far more aggressive than the treatment used for routine angina. Patients whose doctors who do not treat unstable angina with sufficient respect are at extremely high risk for a poor outcome.
posted by Heart Scan @ 12:42 AM
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