Better understanding of coronary pathophysiology needed to improve CV outcomes in women
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Obstructive CAD is not always the best predictor of CV events, especially in women, so a better characterization of coronary pathophysiology is necessary, according to a speaker.
Cardiologists need to “recognize limitations of conventional diagnostic and management approaches for stable ischemic heart disease, particularly in women,” Viviany R. Taqueti, MD, MPH, FACC, FASNC, director of the cardiac stress laboratory at Brigham and Women’s Hospital and Harvard Medical School, said at the American Society for Preventive Cardiology Congress on CVD Prevention.
Conventional diagnostic testing was designed to find obstructive CAD, so it “can lead to overtesting without differentiating who is truly at risk,” she said. “This is especially true for women. This may partly be the case because obstructive CAD is just one phenotype for ischemic heart disease. Diffuse nonobstructive CAD and coronary microvascular dysfunction can also play a very important role in outcomes. To assess these disease processes, we need a different toolbox ... to quantify blood flow and coronary flow reserve.”
Coronary microvascular dysfunction may be the culprit in patients who have refractory angina without obstructive CAD, Taqueti said.
“The coronary microcirculation is much too small to be evaluated in vivo, so it must be evaluated indirectly by perturbing function,” she said, noting that this has historically been done through invasive techniques, but now noninvasive techniques such as PET are being used.
Coronary microvascular dysfunction should be suspected if the patient has symptoms of myocardial ischemia but no obstructive or flow-limiting CAD and objective impairment of coronary microvascular function as indicated by coronary flow reserve less than 2, index of microvascular resistance greater than 25 or inducible microspasm, Taqueti said.
CV risk “rises exponentially as coronary flow reserve values decrease,” she said. “This may occur in a manner that is independent of obstructive CAD.” Coronary microvascular dysfunction is associated with worse CV prognosis even in patients with a coronary artery calcium score of 0, she noted.
Among symptomatic patients, at least half have coronary microvascular dysfunction, and those with it are more likely to have events than those without it, Taqueti said.
“When severely impaired, coronary flow reserve is even more prognostically significant in women,” she said. “This is despite the fact that these same patients are much less likely to have obstructive CAD than men with similarly low coronary flow reserves.”
Currently, there are no therapies specifically targeting coronary microvascular dysfunction, so management has focused on relieving anginal symptoms and prescribing secondary prevention medications in those with coexisting atherosclerosis, according to the presentation.
“Unfortunately, available therapeutic trials have been limited by variable patient selection, lack of a standardized diagnosis to date, small sample sizes and insufficient demonstrations of improvement,” Taqueti said.
Recently, 1-year results of the carefully conducted CorMicA study were encouraging, as patients who received medical therapy based on results of invasive coronary function testing had improved angina severity, she said.
“The focus on obstructive CAD is no longer adequate; this is particularly relevant for our female patients,” Taqueti said. “Effective diagnostic testing needs to identify patients that are at high risk of events (not necessarily anatomically obstructive CAD per se), but without overtesting those who are at low risk. Whether a functional or an anatomic strategy is pursued first, unexplained symptoms do merit consideration of testing for coronary microvascular dysfunction. Characterization of the underlying pathophysiology is important so that we can better diagnose disease, define prognosis and, ultimately, tailor new management strategies to individual patients.”
References:
- Ford TJ, et al. JACC Cardiovasc Interv. 2020;doi:10.1016/j.jcin.2019.11.001.
- Taqueti VR, et al. Circulation. 2017;doi:10.1161/CIRCULATIONAHA.116.023266.
- Taqueti VR, et al. J Am Coll Cardiol. 2018;doi:10.1016/j.jacc.2018.09.042.
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Taqueti VR. Coronary microvascular dysfunction in women. Presented at: American Society for Preventive Cardiology Congress on CVD Prevention; July 25-26, 2020 (virtual meeting).
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