Endothelial dysfunction and features of nociceptive sensitivity in patients with microvascular angina

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): фГБ ОУ ВО СЗГМУ им. И.И. Мечникова Introduction. The pathogenesis of microvascular angina pectoris (MVA) is not completely clear to the end, some authors consider the violation of pain (nociceptive) sensitivity to be an important cause of this disease. The purpose of this study was to study the perception of pain and serum endothelin-1 in patients with MVA. Materials and methods. The criteria for inclusion in the group with MVA (49 patients): chest pain, positive stress test, unchanged coronary artery  according to coronary angiography, the presence of a violation of myocardial perfusion and a decrease in the coronary reserve according to the positron emission tomography (PET) of the myocardium in rest, with a sample with adenosine and a cold test. Pain in the chest was noted in all 49 patients. Assessment of the nature of the pain syndrome was carried out using a 10-point visual-analogue scale (VAS), verbal rank scale (VRS). All subjects underwent a study of the functional activity of nociceptive and antinociceptive systems using the nociceptive flexor reflex method on the Nicolet VikingSelect expert class equipment, the pain threshold (Pb), the threshold of the reflex (Pr), and ratio coefficient (Pb / Pr), which in healthy people is approximately 0.9-1.0. The content of endothelin-1 in the serum of peripheral blood was determined by the method of enzyme immunoassay using test systems "Endotelin 1-21" (the normal values are up to 0.26 fmol / l) Fresh samples immediately after collection of blood were placed on ice and centrifuged during the day. Results. The intensity of pain in the usual attacks in patients with MVA according to the VAS data (5.51 ± 0.2) in most cases was moderate and none of the subjects reached the maximum possible values. According to VRS, moderate pain was described by 60% of patients with MVA, strong - 34.3%.In the study of NFR in patients with MVA, the group as a whole showed a decrease in the pain threshold, the threshold of the reflex, and the ratio coefficient (Pb / Pr) as compared with normal values. In the MVA group, Pb was equal to 9.5 ± 0.58 mA; Pr = 12.1 ± 0.58 mA; Pb / Pr = 0.78 ± 0.02. When studying the level of endothelin-1 in patients with MVA  the level of this peptide was raised to 2.9 ± 0.82 fmol / l. According to the correlation analysis between endothelin-1 and the parameters of NFR, an inverse correlation was observed: between endothelin-1 and pain threshold (r = -0.4; p <0.01); between the level of endothelin-1 and the ratio coefficient of PB / PR (r = -0.9; p <0.01). Based on the results of the correlation analysis of the pain intensity index on the VAS scale and endothelin-1 level in patients with MVA, a significant relationship was found (r = 0.6, p <0.01) Conclusions. In patients with MVA, a decrease in the pain threshold and an elevated level of endothelin-1 were found. Thus, the severity of endothelial dysfunction in patients with MVA was interrelated with the process of perception of pain.