The Role of Nuclear Cardiology in the Diagnosis and Risk Stratification of Women With Ischemic Heart Disease

Attenuation correction in myocardial perfusion imaging affects the assessment of infarct size in women with previous inferior infarct

BACKGROUND

Myocardial perfusion imaging is a well-established diagnostic tool in patients with known or suspected coronary artery disease. Numerous clinical trials have shown that attenuation correction (AC) in single photon emission computed tomography (SPECT) improves the diagnostic accuracy of myocardial perfusion imaging over non-AC SPECT, differentiating between scar and attenuation artifacts. We have previously shown that attenuation artifacts produce an overestimation of the size of inferior infarcts in the male population. It is assumed that women are less affected by inferior attenuation artifacts than men.

PURPOSE

The aim of this study is to evaluate the role of AC in the assessment of infarct size in female patients with a history of myocardial inferior infarct.

PATIENTS AND METHODS

We studied a population of 66 consecutive women, with a history of previous inferior myocardial infarct, by SPECT/computed tomography (CT) with 370+370 MBq of technetium-99m labeled compounds by a 2-day stress-rest protocol. Both AC and uncorrected gated-SPECT/CT studies were reconstructed after scatter and motion correction by ordered-subset expectation maximization iterative reconstruction and resolution recovery. The coregistration of the transmission and emission scans was verified for all patients; any misalignment was realigned manually. Uncorrected and corrected SPECT images were analyzed by software QPS/QGS package using a 17-segment model. For each segment, perfusion and wall motion were quantified using a five-point score according to the American Society of Nuclear Cardiology guidelines. Summed stress, summed rest score (SRS), and summed difference score of the inferior left ventricle wall (inferior, inferoseptal, inferolateral, and apical inferior segments) were calculated. A linear correlation was used to assess the relationship between perfusion and the regional wall motion score as determined by uncorrected gated-SPECT.

RESULTS

The results of quantitative analysis of non-AC and CT-AC SPECT images, respectively, were as follows: summed stress score: 9.47±5.01 and 6.58±4.77% (P<0.001); SRS was 6.05±5.02 and 4.14±4.12% (P<0.001); the summed difference score was 2.92±2.74 and 2.52±2.63% (P=NS), respectively. The correlation between corrected and uncorrected SRS and the regional summed wall motion score of the same segment was R=0.31 versus R=0.34.

CONCLUSION

In the female population, like in men, attenuation artifacts affect the calculation of the infarct size of the inferior wall, with overestimation of the infarct size in uncorrected images. The AC regional perfusion score (SRS) better correlates with the regional wall motion score of the inferior wall in women with previous inferior infarct.

Utility of Imaging in Risk Stratification of Chest Pain in Women

OPINION STATEMENT

Recent decades have seen a growing recognition that the understanding of sex differences in cardiovascular disease (CVD) is vital to optimal diagnosis and management, particularly of women (Mosca et al. Circulation 124:2145-54, 2011). There is simultaneously an increasing appreciation of the multifactorial nature of ischemic heart disease (IHD) in many patients, in whom disease may extend beyond the epicardial coronaries. While obstructive coronary artery disease (CAD) remains underdiagnosed in women and still represents a major burden of disease, women also present with nonobstructive CAD more commonly than men (Patel et al. N Engl J Med 362:886-95, 2010). Indeed, microvascular dysfunction, coronary artery vasospasm, and coronary dissections contribute to a larger proportion of IHD in women than men (Bairey Merz et al. J Am Coll Cardiol 47:S21-9, 2006). Here, we review the symptom presentation of women with IHD and the noninvasive modalities used to risk stratify women with suspected IHD.

Advanced Imaging and Diagnostic Methods in the Assessment of Suspected Ischemic Heart Disease in Women

Although differences diminish with age, outcomes are overall worse for women compared to men who present with suspected acute coronary syndrome. The reasons for this discrepancy are multifactorial, including sex-related differences in atherosclerosis biology and fluid dynamics, as well as a premature conclusion by providers that chest pain must be noncardiac in the absence of obstructive coronary artery disease. In this review of existing literature, we explore the diverse differential diagnosis in this unique set of patients. Especially in women with persistent symptoms, absence of occlusive disease should prompt consideration for subangiographic plaque disruption, epicardial or microvascular endothelial dysfunction, transient neurohormonal imbalance predisposing to Takotsubo cardiomyopathy or spontaneous coronary artery dissection, underlying systemic inflammatory conditions, thromboembolic disease, myocarditis, and sequelae of congenital heart disease. As always, a thorough history and attentive physical exam will help guide further work-up, which in many cases may warrant noninvasive imaging, such as contrast-enhanced echocardiography, cardiac magnetic resonance imaging, or positron emission tomography, with their respective means of measuring myocardial perfusion and myocardial tissue pathology. Lastly, intracoronary imaging such as intravascular ultrasound and optical coherence tomography and invasive diagnostic methods such as coronary reactivity testing continue to add to our understanding that what appear to be atypical presentations of ischemic heart disease in women may in fact be typical presentations of pathologic cousin entities that remain incompletely defined.