Ask Dr. Pat

Congestive Heart Failure in Women

To understand treatments for CHF, it is important to understand that there are two types of CHF. When most people think of CHF, they imagine an enlarged heart muscle that weakly pumps blood. Indeed, this is the type of CHF, termed CHF with a low ejection fraction (HF-Reduced EF) that has undergone the most important advances in therapy. Ejection fraction, or EF, is a simple measurement of heart strength representing the ratio of the amount of pumped blood divided by the blood in the heart prior to each heart beat. A normal ejection fraction is above 50 percent (a heart filling with 100cc of blood in diastole ejects over 50cc). In the last several years, the medical community has become aware of an increasing percentage of patients with CHF who have a preserved ejection fraction (HF-Preserved EF), over 50 percent. These patients do not have baggy weakened hearts, rather they commonly have a stiffened heart muscle due to enlargement of the muscle fibers called left ventricular hypertrophy, or LVH. Hypertension puts an added load on the heart fibers stimulating LVH, while obesity and glucose intolerance create chemical changes leading to LVH and heart stiffening. This stiffening of the heart requires a greater than normal filling pressure to force open the heart walls during diastole (sometimes called “diastolic dysfunction”) again resulting in back pressure and congestion in the lungs, similar to that noted in heart failure with reduced ejection fraction.

800px-Blausen_0165_Cardiomyopathy_DilatedIllustration of a Normal Heart vs. Heart with Dilated Cardiomyopathy (Image Source: “Blausen gallery 2014“. Wikiversity Journal of Medicine.)

 

The Gender Difference

Gender has an important impact in CHF. Women’s hearts are far more prone to develop left ventricular hypertrophy (LVH) than men’s hearts even when women have similar levels of hypertension and metabolic syndrome. As a consequence, HF-preserved EF is twice as common in women, particularly with aging. In contemporary studies over 50 percent of elderly patients presenting to an emergency room with CHF, a majority of whom are older women, have HF-Preserved EF. While the prognosis of this type of heart failure is a bit better than HF-reduced EF, it remains a serious condition with a very high rate of rehospitalization and subsequent mortality.

The gender difference in the degree of LVH may also have implications for HF-reduced EF. A woman with HF-reduced EF may have an enlarged heart but at times with more wall thickening and stiffer heart muscle than found in men with a similarly low EF. This, further raises her heart’s filling pressures and degree of congestion in the lungs. These women may become symptomatic at an earlier more treatable phase of the illness, possibly accounting for the somewhat better outcomes of women than men in HF-reduced EF.

The treatment of HF-reduced EF aims to reverse the factors that caused the abnormal heart muscle. Following a heart insult—like the heart attack suffered by you Pam, in which the muscle nourished by a blocked heart artery is damaged—the remaining normal segments have to do the work of the entire heart. The body senses the imminent heart weakness and responds by producing classic “fight or flight” chemicals. First, adrenaline, which increases the heart rate and force of contraction. Angiotensin, a powerful vessel constrictor with multiple other properties is also produced in excess. These strategies are effective in the short run, improving the circulation by acutely supporting the weakened muscle. Evolution is often short sighted, however, and in the long run, such exposure from the adrenal “fight or flight” chemicals is directly toxic to the heart muscle and damages the intricate internal protein structure of the muscle fiber, thus weakening heart muscle contraction. A vicious cycle ensues as the additional heart weakening elicits a greater response from the body, eventually culminating in a very low ejection fraction. Although damaged, the vast majority of the weakened muscle cells do not die, and with proper treatment can repair their contractile force.

 

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