General Medical · Health

Coronary Artery Disease in Women: What Are the Options When an Artery Is Blocked?

Unstable Angina

This situation is in stark contrast to that of individuals with unstable symptoms, a large portion of whom are at high short-term risk of MI and death. Early revascularization is critical in both sexes.  Unstable angina is recognized when the pattern of angina discomfort becomes unpredictable, typically in a crescendo pattern, with symptoms occurring more frequently, more painfully, and with longer duration in someone with previous stable angina—or suddenly for the first time in someone with no prior history.

Unstable angina often escalates to resting discomfort, the angina occurring without any—or with only trivial—exertion. These symptoms indicate an acute coronary syndrome (ACS).  In ACS, a thin, inflamed cap overlies an atherosclerotic plaque with a soft, cholesterol-rich core. In women this inadequate cap may erode, whereas in men it tends to rupture—in either case exposing the flowing blood to the soft plaque material, activating blood-clotting elements—namely, platelets—to adhere. This produces a blood clot (thrombus) that can then grow to partially or completely occlude the artery.  Of the 1.2 million hospital discharges for ACS yearly in this country, approximately one third of these comprised a completely occluded artery that has resulted in an acute MI. (An acute MI is referred to as a STEMI, because of elevation of the ST portion of the EKG, which indicates heart injury.) The remaining two thirds of the patients discharged suffer from a non-STEMI in which the critically blocked artery allows a minimal amount of blood flow, resulting in less heart injury. In both types of ACS, a degree of heart muscle damage is confirmed by EKG changes and detectable blood enzymes, called troponin, released by the injured heart cells.

There is widespread consensus, proven in multiple clinical trials, that early revascularization in ACS, particularly ACS with an abnormal electrocardiogram and troponin elevation, limits heart damage and saves lives. In fact, in a STEMI, “door to balloon time”—that is, the time it takes from ER admission to opening the occluded artery—is a critical determinant of the amount of heart damage and the subsequent prognosis (see figure 1).

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Untitled 2Figure 1.  Angiogram indicating a  severe obstruction of the left anterior descending, the largest of the three coronary arteries, which is treated with a drug stent deployed by balloon inflation, restoring normal blood flow. (Source: James A. Blake, M.D.)

Some studies indicate that these procedures are underutilized in women—a situation addressed in recent guidelines proposing that the preponderance of clinical evidence warrants identical treatment for women and men.  It is true that studies in both PCI and CABG indicate a higher rate of complications and mortality in women compared with men, and this may be one factor in discouraging their appropriate utilization.  However, contemporary studies indicate that the increased risk of these procedures is almost entirely attributable to more advanced age accompanied by a higher prevalence of hypertension and diabetes in women as opposed to men who require these procedures. The gender gap disappears in most studies when the results are statistically adjusted for these adverse attributes. Still, in the case of CABG and recovery from MI, unknown factors remain responsible for a slightly worse outcome for women.  The bottom line, however, is that when indicated, these procedures should never be withheld, since the improvement in prognosis in women resulting from revascularization by PCI or CABG is as good as, and sometimes better than, that in men. Furthermore, the evolution of invasive and operative techniques has diminished complications in both sexes, substantially narrowing any gender difference in outcome.

 

Women’s Response to High Blood Pressure

Some studies have suggested that smaller body size, measured by body surface area and correlated with smaller coronary arteries, accounts for this slightly increased risk among women referred for revascularization. Arterial size is important, but is more strongly determined by the total amount of coronary plaque that may scar and narrow the arteries than by body size. Perhaps a more important factor is that women have a different cardiac response to high blood pressure and elevated blood sugar, which are commonly present in women requiring these procedures.  Whereas male hearts tend to enlarge under stress, female hearts more commonly demonstrate hypertrophy (wall thickening)—which, while it helps to maintain the required force of contraction, stiffens the heart, mandating a higher pressure to fill the heart between heartbeats (diastole).  So-called “diastolic dysfunction” is more prevalent and severe in women—resulting in an increased risk of heart failure after an MI, CABG, or complex PCI—and may be a more cogent explanation for any increased risk in women.

The complexity of these procedures mandates an expert heart team to perform them.  Expertise demands not only a surgeon or interventional cardiologist who performs a high volume of procedures, but, for optimal outcomes, all members of the team must be equipped to rapidly manage any complications from invasive procedures among women and men.  An invasive cardiologist who performs at least 50 angioplasties a year and a hospital with a cardiac surgical volume of at least 200 yearly CABG procedures provide a useful minimum volume to maintain competency; however, the best outcomes are achieved in high-volume centers with several qualified operators.  University-associated heart programs provide a high level of collaboration among well-trained colleagues who are dedicated to promoting the best patient outcomes and often have the lowest available rates of complications.

Next page: The Medical Management of Stable Angina

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