Coronary microvascular dysfunction with INOCA predicts poor outcomes
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In patients with ischemia and no obstructive coronary arteries, known as INOCA, the level of nonobstructive coronary stenosis does not affect the prognostic impact of coronary microvascular dysfunction, researchers reported.
“A significant proportion (more than 50%) of symptomatic INOCA patients without coronary stenotic lesions have coronary microvascular dysfunction (CMD) that contributes to myocardial ischemia,” Wenliang Che, MD, PhD, of the department of cardiology at Shanghai Tenth People’s Hospital and Tongji University School of Medicine in Shanghai, and colleagues wrote in the study background. “The presence of CMD indicates an increased risk of a worse prognosis. However, it is yet unclear whether nonobstructive coronary stenosis affects the prognostic significance of CMD in INOCA.”
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In a retrospective, observational study, Che and colleagues analyzed data from 151 adults with INOCA (mean age, 61 years; 59% women) who underwent invasive coronary angiography, assessed by coronary angiography‐derived index of microcirculation resistance (caIMR). Researchers stratified patients as having no stenosis (0% stenosis) or nonobstructive stenosis (< 50% stenosis). Patients also underwent cadmium-zinc-telluride single-photon emission CT myocardial perfusion imaging (MPI) during stress and rest periods.
The primary endpoint was a composite of major CV adverse events, including CV death, nonfatal MI, unplanned coronary revascularization, HF, stroke and anginal‐associated rehospitalization, assessed during a median follow-up of 35 months.
The findings were published in Clinical Cardiology.
Within the cohort, 47% of patients had no stenosis and 53% had nonobstructive stenosis. The mean caIMR was 32.7. CMD, defined by a caIMR of at least 25, was more prevalent among patients with no stenosis (76.1%) than those with nonobstructive stenosis (48.8%; P = .001). Similarly, CMD was more prevalent among those with an abnormal vs. normal MPI (39.4% vs. 22.5%; P = .024).
During follow-up, 30.5% of patients had a major adverse CV event; the rates did not differ between the no‐stenosis and nonobstructive stenosis groups (P = .122).
Additionally, among all patients with INOCA, rate of the major adverse CV events was higher for those with CMD vs. without (40% vs. 13.8%; P < .001). Those with CMD and no stenosis had the worst prognosis, according to researchers.
In Cox regression analysis, researchers found that CMD (HR = 2.726; 95% CI, 1.162-6.396; P = .021) and abnormal MPI (HR = 1.979; 95% CI, 1.03-3.801; P = .041) predicted risk for major adverse CV events for all patients with INOCA and no stenosis; however, no stenosis and nonobstructive stenosis were not predictors of major adverse CV events in INOCA (P = .18).
The researchers noted the findings suggest CMD could independently predict poor outcomes in INOCA, particularly in patients with no stenosis.
“The finding of visually normal‐appearing coronary arteries by angiography does not totally rule out the presence of functional or structural disorders of the coronary system, such as CMD,” the researchers wrote. “These findings suggest that comprehensive efforts should be made to search for underlying etiologies of ischemia by functional (noninvasive or invasive) tests.”
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