Inflammation and Microvascular Dysfunction in Cardiac Syndrome X Patients Without Conventional Risk Factors for Coronary Artery Disease
Are coronary microvascular dysfunction (CMD) and inflammation related in the cardiac syndrome X (CSX)?
The study consisted of 21 CSX patients without traditional cardiovascular risk factors and 21 matched apparently healthy control subjects. Positron emission tomography was used to measure myocardial blood flow (MBF) and coronary flow reserve (CFR) in response to intravenous adenosine, and high-sensitivity C-reactive protein (CRP) was measured to assess inflammation. Patients were subdivided a priori into two groups according to CRP concentrations at study entry (i.e., ≤3 or >3 mg/L).
Mean age was 52 ±10 years of age, and 17 were women. The only difference between groups was a CRP >3 mg/dl in 8/21 in CSX patients, with none in the controls. There were no differences in resting (1.20 ± 0.23 ml/min/g vs. 1.14 ± 0.20 ml/min/g; p = 0.32) or hyperemic MBF (3.28 ± 1.02 ml/min/g vs. 3.68 ± 0.89 ml/min/g; p = 0.18) between CSX patients and the control group, whereas CFR was mildly reduced in CSX patients compared with the control group (2.77 ± 0.80 vs. 3.38 ± 0.80; p = 0.02). Patients with CRP >3 mg/L had more severe impairment of CFR (2.14 ± 0.33 vs. 3.16 ± 0.76; p = 0.001) and more ischemic electrocardiographic changes during adenosine administration than patients with lower CRP, and a negative correlation between CRP levels and CFR (r = -0.49; p = 0.02) was found in CSX patients.
CSX patients with elevated CRP levels had a significantly reduced CFR compared with the control group, which is indicative of CMD. The study thus suggests a role for inflammation in the modulation of coronary microvascular responses in patients with CSX.
The investigators are pioneers in the study of microvascular angina or CSX. The majority of patients with CSX have at least one of the major cardiac risk factors including smoking, hypertension, and the insulin resistance syndrome, each of which is associated with an elevated CRP. The patients were well characterized as having ‘typical angina,’ but the frequency was not recorded. It would be interesting to investigate whether clinical worsening is associated with a change in CRP.
Keywords: Inflammation, C-Reactive Protein, Biological Markers, Microvascular Angina, Positron-Emission Tomography
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