Acute Myocardial Infarction

July 28, 2011

Cardiovascular disease is the leading cause of death among women in the United States. In fact, according to the 2003 statistical update from the American Heart Association, cardiovascular disease kills over 7 million women annually in the United States, more than the next seven causes of death combined. Of these cardiovascular deaths, the most common cause is acute myocardial infarction (MI). An MI occurs when blood supply to the heart is suddenly interrupted for some period of time. This process may occur because of the development of a thrombus on the surface of a previously existing cholesterol plaque in the coronary arteries. If this blockage is complete and persists for some time—often greater than 30-60 min— the result may be death to the myocardium supplied by this vessel, a so-called transmural infarction. In other situations, the blockage may not completely obstruct all myocardial blood flow, yet it persists and leads to damage. The resulting infarction is termed nontransmural, indicating that the damage has not been as extensive. On occasion, MIs may also be caused by spasm of the coronary artery or very transient obstruction that cannot be identified on later angiographic evaluation.

The pathophysiology that leads to an MI is the same in women and men; however, there are important gender differences that are apparent on presentation with MI. Women are less likely than men to present with an acute transmural infarction (also called an “ST-elevation MI” because of the typical EKG pattern). Instead, women more often experience nontransmural (“non-ST-elevation”) infarctions or acute coronary symptoms not resulting in an MI. This more subtle presentation may be one reason why physicians and laypersons tended to consider coronary heart disease less as a disease of women than of men. In fact, multiple studies have shown that, compared with men, women present later to the hospital with an MI, are less likely to receive important thrombolytic drugs when appropriate, and are less likely to be referred for coronary angiography. Furthermore, because MI is often not correctly diagnosed, women are less likely to receive appropriate medications and cardiac rehabilitation.

Recent findings have effectively destroyed the myth that MI is a less important disease in women than in men. On the one hand, women have important differences from men who present with MI—on average, the women are 10-20 years older, with more elevated cholesterol levels and possibly more hypertension, but a lower prevalence of cigarette smoking. Women also are more likely to have diabetes, which is a major risk factor for poor outcome with MI and, when present, negates any gender benefit for women. In addition, women who sustain an MI are also as much as 50% more likely to die in the short term as are men. Finally, perhaps because of their older age and greater extent of other illness, women are more likely to suffer so-called mechanical complications of MI, such as cardiac rupture.

In addition to the different characteristics of women and men with MI, there are important differences in the symptoms that each gender tends to report upon presentation. The classic symptoms, such as the sudden onset of pressure centered in the chest, radiating down one or both arms, and associated with a “cold sweat” (or diaphoresis), should be considered more as the typical middle-aged male symptoms associated with MI. While both genders certainly experience a full range of symptoms, women are much less likely to have these so-called “classic” symptoms and are more likely to have a wider range of complaints, including shortness of breath (dyspnea), nausea or vomiting, and pains in the jaw, back, or even abdomen, with or without chest pain. Women are also more likely to sustain an MI without any characteristic symptoms—the socalled “silent MI.” It is now recognized that any individual—either physician or layperson—who relies on more stereotypical chest pain symptoms for diagnosis will fail to appreciate early symptoms of an MI more often in women than in men.

Good news is that the therapies for MI have, almost uniformly, provided strong benefit to both genders. Unfortunately, there is mounting evidence that women do not receive these therapies as often as men. For patients with an ST-elevation MI, the accepted beneficial therapies include thrombolytic therapy and “primary angioplasty,” which involve emergent coronary angiography to identify the occlusion and then angioplasty to open the artery. Both of these therapies work in women and men, and in the multitude of medical studies to evaluate these treatments, it appears that the benefit for women is similar to the benefit extended to men. However, because women with MI tend to be older, with greater comorbidity, and because they are on average smaller in body size than men, they may have more problems with bleeding with all therapies and may sometimes not be eligible for thrombolytic therapy. Furthermore, among older patients, there is a concern that women may have more complications with thrombolytics, and some investigators have proposed that primary angioplasty is a better treatment for women. However, it is also true that women may arrive at the hospital too late for thrombolysis, emphasizing that women, their families, and their physicians need to recognize possible signs of MI and present to emergency departments promptly so that appropriate therapy may be pursued.

Just as important as rapid treatment for STelevation MI, is appropriate therapy for non-ST-elevation MI, the more common presentation for women. While thrombolytic therapy is not an effective treatment for this condition, a wide range of medical therapies significantly reduce the risk associated with this type of infarction. Relative to management of this condition, debates within the cardiology community have recently focused on the routine use of certain medications, most notably the glycoprotein IIb/IIIa inhibitors, and the routine use of an “early aggressive strategy,” which involves early catheterization and intervention as needed for patients with non-ST-elevation MI. While there has been some evidence that women do not receive as great a benefit with IIb/IIIa inhibitors as do men, a recent study that used these agents in the evaluation of early catheterization demonstrated that the benefit of an “aggressive strategy” was just as strong in women as in men, but of particular benefit in high-risk women.

Medications that should be considered for all patients with MI provide benefits to both genders, in the setting of ST-elevation or non-ST-elevation infarction. The most important of these drugs remains aspirin, which in the early studies of ST-elevation MI provided benefit equal and in addition to that of thrombolytic therapy. Other drugs that must be considered include betablockers (which may provide even stronger benefits to women than to men), ACE inhibitors, and statin medications. The statins, which lower blood cholesterol levels, have demonstrated on average a 20% reduction in mortality in all patients with coronary disease, and there is no evidence of preferential effect by gender. One note specific to women is that the majority of evidence now indicates that hormone replacement therapy does not provide any special level of protection before or after MI.

After recognition of an appropriate therapy for MI, other procedures and treatments may be appropriate for women. Some of these, such as nuclear cardiac scans or echocardiograms, can give a better indication of individual levels of risk and guide intensity of treatment. Other treatments, such as cardiac rehabilitation, including exercise training and secondary prevention, are powerful tools that, again, physicians have been less likely to offer to women than to men.

Scientific knowledge has increased the understanding of the burden of cardiovascular disease in women. With a better appreciation of the clinical characteristics and symptoms that mark acute MI in women, we are now much more able to provide therapies of proven benefit to all patients.

SEE ALSO: Cardiovascular disease, Chest pain, Cholesterol, Diabetes, Hormone replacement therapy, Smoking

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