Horses and Zebras: Multimodality Imaging in the Evaluation of Chest Pain in Women
Dr. Emily Lau presented during the April 7th session Sex-Based Differences in Cardiovascular Imaging: Females Are Not Small Males at the 2024 American College of Cardiology Scientific Sessions in Atlanta, Georgia. In this discussion, she talks with Rebecca Kapur, Managing Editor of Cath Lab Digest, about her presentation, "Horses and Zebras: Multimodality Imaging in the Evaluation of Chest Pain in Women."
"Even in 2024, we are continuing to see pretty striking gender disparities in health outcomes between men and women, especially with ischemic heart disease," says Dr. Lau. "And there remains, I think, still a lack of understanding or awareness that ischemic heart disease is very much a woman's disease. There are true differences in disease epidemiology and disease phenotype that we really need to be aware of as cardiovascular providers."
Listen/watch to hear more from Dr. Lau:
The transcript below has been lightly edited for clarity:
How is ischemic heart disease in women unique?
Dr. Emily S. Lau: I really think of ischemic heart disease in women as a unique phenotype. Specifically, we know from an anatomic perspective that women have smaller epicardial coronary arteries than men do. And functionally, we know that there are a lot of differences between men and women too.
For example, coronary remodeling is greater within women. There's greater endothelial shear stress. And altogether, when we put these collectively, look at all of these differences, it's not surprising that women with ischemia are more likely to have nonobstructive coronary disease. What are some of the noninvasive strategies for evaluating women? We have such a rich selection of options of noninvasive imaging modalities that can help evaluate chest pain in women. And I would say that we really should be guided by the woman's pre-test probability that their symptoms are related to coronary disease to help us pick which strategy is the right modality. So for example, in low to intermediate risk women who can exercise and have a normal ECG, the recommended noninvasive test of choice is actually an exercise ECG without imaging. Now for higher risk women, that's definitely not true.
The addition of imaging is really important. So things like myocardial perfusion imaging spec studies, PET studies, and cardiac MRIs with the assessment of things like myocardial blood flow reserve are important diagnostic modalities for the evaluation of ischemia with nonobstructive coronary arteries, including coronary microvascular dysfunction.
And so there really is a broad array of noninvasive options to evaluate women with chest pain and we should be guided by how women with chest pain you think is driving our patient's symptoms and what is her pre-test probability of having obstructive coronary disease?
Are we becoming more aware of women with nonobstructive heart disease and what happened in the past to these women?
I think absolutely that they've existed always. It seems if we look at cohort studies now as it looks like the prevalence of nonobstructive coronary artery seems to be rising and that may be true epidemiologically, but it probably relates to the fact that it was really underdiagnosed in the past.
So there's definitely been greater recognition of the importance of diagnosing ischemia and MI with nonobstructive coronary arteries in both men and women, because of course it can affect both men and women, even though it's more prevalent among women. And I think what was happening before was these individuals were sort of being told "Well, your chest pain is not cardiac in nature, it's GI, it's in your head," and they're sort of being dismissed. But we know actually that patients with INOCA have greater cardiovascular events than patients who do not have ischemia with nonobstructive coronary artery disease, so it's important that we're diagnosing these patients with what they actually have.
I'm wondering how often is nonobstructive coronary artery disease found in the cath lab? And if it is found, what are the next steps?
I think you highlighted an important point, which is that probably a lot of patients with INOCA are not being diagnosed. They're not necessarily being brought to the cath lab. But we are seeing, if we look at some of the cohort studies that up to two thirds of women who have stable chest pain, who go to the cath lab, actually have nonobstructive coronary arteries.
And I think it's important that we can establish this diagnosis just because there are some medical therapies that can help improve symptoms, including things like calcium channel blockers or nitrates. And it also helps to have diagnostic certainty.
If we're essentially attributing chest pain to something that's not cardiac without doing a full evaluation, we really may be missing an opportunity to help improve the symptoms for our patients and functional status for these patients and even clinicians. clinical outcomes.
What do we know about coronary microvascular dysfunction? And then there's the term MINOCA. How do they relate?
You know, there's, I think, a new sort of jargon related to nonobstructive coronary arteries. I kind of call them the “-NOCAs†because there's angina with nonobstructive coronary arteries (ANOCA). These are individuals who are experiencing chest pain or symptoms related to not getting enough oxygen into their hearts who have nonobstructive coronary arteries with coronary artery disease. Then there's ischemia with nonobstructive coronary arteries, or INOCA, which is where we have objective evidence that there is an area of the heart that is truly ischemic. And that's usually through some sort of functional testing, like a SPECT or a PET study. And then there's MINOCA, or MI with nonobstructive coronary arteries, where we see true evidence of myocardial injury through, for example, high sensitivity troponin or biomarker testing. And this really is, I think, a spectrum of disorders, and it's an umbrella term for a number of different etiologies. Now, coronary microvascular dysfunction is one of the causes of ANOCA, INOCA, and MINOCA, but it's only one of the many causes.
There are plenty of other different etiologies, including things like spontaneous coronary artery dissection and coronary spasm. But I think coronary microvascular dysfunction is sort of thought of almost equivalent to INOCA because it can be noninvasively assessed. So if you have a patient for whom you suspect who has INOCA and you really want to try to understand what is going on, why are they having these symptoms? Why do they have evidence of ischemia on their functional testing? You can have them undergo a stress PET or stress cardiac MRI and assess their myocardial blood flow reserve to help make the diagnosis of coronary microvascular dysfunction.
Does that calculate it for you or is that something done by the physician who's reviewing that?
Myocardial blood flow reserve or coronary flow reserve otherwise known as CFR is really the ratio of myocardial blood flow at max hyperemia to normal, to resting myocardial blood flow. In other words, it's basically the maximum increase in coronary blood flow relative to the normal resting volumes. And so it can be assessed through cardiac stress PET or with cardiac MRI. And it is one of the parameters that's ascertained by the study. And of course, then it is together with the software that is used to interpret these studies. The physician then provides a quantitative number, essentially, for what your coronary flow reserve is. So a CFR of greater than or equal to two. Two is normal. A CFR of less than two is reduced and helps make a diagnosis of coronary microvascular dysfunction.
You talked a bit about steps and types of imaging. Are these in line with the current guidelines?
What is really exciting about the most recent chest pain guidelines is that they actually recommend further diagnostic testing beyond coronary angiography for patients with suspected MINOCA, really to help get at this point, to establish a diagnosis of coronary microvascular dysfunction and to help risk stratify these patients.
And this is different than in the past because for these patients, often they were given... a sort of empiric diagnosis or presumptive diagnosis of INOCA, but after they got their cath and there was no obstructive coronary arteries, often people would not take the diagnostic testing further. So you were sort of left with, well, they have INOCA, could be coronary microvascular dysfunction, could be spasm, could be something else.
And I think that this really allows us to more precisely tailor our therapies to our patients. and even to help restratify them.
Is there anything I didn't ask about that you wanted to bring up or mention?
Even in 2024, we are continuing to see pretty striking gender disparities in health outcomes between men and women, especially with ischemic heart disease. And there remains, I think, still a lack of understanding or awareness that ischemic heart disease is very much a woman's disease. There are true differences in disease epidemiology and disease phenotype that we really need to be aware of as cardiovascular providers and that our role as cardiovascular providers is to advocate for these patients to actually establish a diagnosis even when it's not sort of the run-of-the-mill obstructive coronary disease.
Excellent. Thank you so much for talking with me. I appreciate you taking the time.
This has been wonderful. Thank you very much. Thank you.
Emily S. Lau, MD, MPH, FACC
Director, Cardiometabolic Health & Hormones Clinic; Corrigan Women’s Heart Health Program, Massachusetts General Hospital; Assistant Professor of Medicine, Harvard Medical School
Dr. Emily S. Lau is on X at @emilyswlau
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