Women and Heart Disease

From Journal for Nurse Practitioners

Sandra A. Carey, APN-BC; Jennifer R. Gray, PhD

A Diagnostic Challenge

Posted: 06/28/2012; Journal for Nurse Practitioners. 2012;8(6):458-463. © 2012 

Abstract and Introduction

Abstract

Diagnosing and managing women who are at risk or have known coronary heart disease (CHD) continues to be a challenge, despite advancing imaging technologies and recent public awareness campaigns. This challenge persists as a result of many contributing factors that all too often go unrecognized. The aim of this article is to establish the extent and possible causes of gender disparities related to CHD and explore 2 obstacles of diagnosing women with or at risk: subclinical coronary disease and noninvasive diagnostic imaging.

Introduction

More women in the United States die from cardiovascular disease (CVD) than men do. In 2007, coronary heart disease (CHD) was the number 1 killer of women in all age groups. Nearly 1 in 3 women die from CHD, compared to nearly 1 in 5 from cancer.^[1] Although women develop CHD later in their lives, women younger than 65 are also twice as likely to die from an acute myocardial infarction (MI) compared to men with comparable age and risk factors.^[2] In fact, over 9,000 US women under 45 had an MI in 2009.^[3] Early diagnosis increases the probability that a woman with CHD will have positive treatment outcomes and live longer.

Early diagnosis of CHD in women is difficult when many providers are unaware of the risk of a CHD death in their female patients.^[4] In reality, 38.2 million US women (34%) are living with some form of CVD. The population of women at risk is even larger.^[4] Advanced imaging technologies have given providers a wide range of diagnostic modes to determine CHD in women. However, accuracy and limitations of stress testing in women remain areas of significant confusion.^[5]

The aim of this article is to establish the extent and possible causes of gender disparities related to CHD and explore 2 obstacles to diagnosing women with or at risk for heart disease: subclinical coronary disease and noninvasive diagnostic imaging.

Noninvasive Testing in Women

Multiple tools have been developed to identify atherosclerotic disease at its preclinical stages in order to help modify disease progression. Imaging modes have demonstrated gender differences. The high prevalence of nonobstructive CHD and single vessel disease in women results in an observed decreased accuracy in diagnostic testing that often results in higher false-positive rates.^[25]Presently, the ACC/AHA guidelines recommend that women who are asymptomatic with a normal echocardiogram (ECG) undergo routine exercise stress treadmill testing as the initial screening for heart disease. Unfortunately, ECG changes during exercise are frequent with women and diminish the accuracy of the interpretation. Subsequently, specificity in the literature has been reported as low as 61% for women undergoing exercise stress testing without imaging.^[26] Stress echocardiography has demonstrated better accuracy for detecting or excluding significant disease with a mean sensitivity of 81% and specificity of 86%. However, most echocardiography studies have predominantly included men. Additionally, women who are referred for exercise testing are often older or obese and unable to reach target heart rates required for accurate assessment.^[26]

In patients who cannot exercise, dobutamine is the most common stress agent used for stress echocardiography. The sensitivity and specificity of exercise echocardiography in women is reported to be 80%–90% and 82%–86%. Stress echo has been reported as the most sensitive imaging mode for women. Although great strides have been made in the field of harmonic imaging and contrast echocardiography, female patients often present challenges. A significant amount of expertise is required for interpretation of images, especially in the obese or larger-breasted patient. Additionally, detection of single vessel disease found more common in women is better detected with myocardial perfusion imaging (MPI).^[27] MPI with exercise or pharmacological stress has also been shown to be of value in risk stratification in women with an intermediate likelihood of CHD.^[28]

Regadenoson, a new A_2A adenosine receptor agonist, has become the preferred pharmacological agent. This coronary vasodilator is a single bolus intravenous injection that negates the requirement for infusion. Regadenoson stress tests are not affected by the presence of beta blockers, and total testing time has been reduced to 4 minutes.^[29]

A comprehensive meta-analysis looking at the accuracy of thallium imaging (21 studies, N 5 4,113 women) revealed that accuracy in men was higher than women (sensitivity and specificity 5 85% vs 64%–78%). Breast attenuation is frequently reported as problematic as it creates a false positive and interferes with the imaging of the territory in the left anterior descending coronary artery. The advent of gated single photon emission computed tomography (SPECT) has assisted in differentiating attenuation artifacts from infarcts. Two studies using gated SPECT imaging reported an improvement of sensitivity (91%–92%) for detection of a stenosis < 50%; however, only women who had a high pretest probability for CHD were included in these studies.^[28]

Coronary calcium score (CAC) assessed by cardiac computed tomography (CT) is currently being used for a method of early detection for atherosclerosis. Evidence exists that CAC is an independent predictor of cardiac events and mortality, beyond traditional risk factor assessment.^[30] The data are strongest for white, non-Hispanic men. Although superior to Framingham risk index predictions, CAC scoring may fail to detect the soft or mixed plaques frequently seen in women.^[30]

Coronary angiography using multi-slice spiral CT holds significant promise. Coronary CT angiography (CTA) is a safe and reliable procedure. This technology has proved to be accurate, especially in vessels without heavy calcifications that are 1.5 mm or more in diameter. The key reported advantage to this technology is the negative predictive value (95%–100%) among patients with low to intermediate risk for CAD. However, only small studies have included women (N, 400).^[30] More research using coronary CTA in women with subclinical disease could provide improved strategies for identifying asymptomatic women who may benefit from more aggressive primary preventive care.

Conclusion

The number of deaths as a result of CVD in women is rising but declining in men. This disease process is responsible for overall mortality of 49% in women. This problem is expected to escalate because of the aging population, obesity, metabolic syndrome, and diabetes, as it affects women disproportionately.^[31] Incomplete understanding of the pathophysiological mechanisms, such as microvascular dysfunction, as well as bias in patient care that is not seen for male patients, may explain the continued poor outcomes in women. Surveys and quality improvement initiatives have consistently highlighted the underuse of evidence-based guidelines for women.^[31] Gender-based discrepancies exist in the availability, use, and accuracy in diagnostic testing in women. Nonobstructive CAD is a consistent finding in women undergoing angiography, yet performance of cardiac imaging tests is based on demand ischemia to detect obstructive disease and only facilitates accurate risk stratification for women in the near term (2- to 5-year event-free survival).^[32]

A consensus needs to be reached on an appropriate algorithmic approach to diagnostic testing in women. Newer technologies that show promise for increased sensitivity and specificity for women with obstructive and nonobstructive disease need to be globally accepted as standard of care. Large longitudinal studies analyzing subclinical disease in women are needed. Improved understanding of the earlier phase of disease could lead to prevention and limit the major cardiac events that continue to ensue. This burden of disease will continue unless understanding and appreciation of gender-specific pathophysiology with regard to CHD is actualized.^[32]

The role of the nurse practitioner (NP) has successfully been implemented in the cardiology community in response to alleviating gaps in heart failure management. Additionally, many NPs are first-line providers for women. As providers we excel in patient education and health promotion—arguably more successfully than our physician colleagues. The number of NPs practicing in primary care and cardiology will continue to grow. With strength in our numbers, NPs will play a pivotal role in both improved patient and provider awareness and adherence to recommended clinical guidelines for women with or at risk for CHD.