Cardiac Syndrome X: assessment of endothelial function by peripheral arterial tonometry

Background: Cardiac Syndrome X (CSX) is characterized by the presence of typical chest pain, a positive exercise test result and normal coronary arteries upon angiographic examination. The development of this syndrome is thought to be heterogeneous, involving many pathogenic mechanisms. Among other mechanisms, impaired endothelial function may predominantly contribute to the pathogenesis of symptoms in CSX patients. In this work we prospectively evaluated the role of endothelial function, using non-invasive peripheral arterial tonometry, in a cohort of patients which included healthy patients, patients with coronary artery disease and patients with CSX, from Italian-speaking Switzerland. Methods: We examined systemic endothelial function in a cohort of 37 patients: 8 healthy patients, 15 patients with coronary artery disease and 14 CSX patients. The latter were identified from the Swiss-Italian cohort of the “Italian registry of patients with Cardiac Syndrome X” (“Registro italiano dei pazienti con Sindrome X”). Endothelial function was assessed using peripheral arterial tonometry, a validated and FDA (U.S. Food and Drug Administration) approved tool for the examination of systemic and coronary endothelial function in humans [1-5]. Results: The average values for the two main indexes measured, the “Endopat index” and the “Endopat index according to Bonetti”, were over the discriminatory value of 1.67 for all studied groups. A value of less than 1.67 indicates the presence of endothelial dysfunction. Statistical analysis failed to demonstrate a significant difference between studied groups (p value of 0.442 and 0.417 respectively). Larger differences could be extrapolated in some selected subgroups, but in our study, the number of patients was too small to allow statistical analysis of the significance of the results. Conclusion: Our results, based on a relatively small sample of patients with CSX, do not show a significant difference in endothelial function, measured by peripheral arterial tonometry, between patients with CSX and patients with coronary artery disease. The interpretation of these results, which contrast with some previous studies, is not absolute. The multitude of mechanisms involved in the development of this syndrome makes investigation of this condition, and, in particular, interpretation of results yielded from small cohorts, challenging. Moreover, the impact of the methodology used for the measurement of endothelial function, and the similar prevalence of risk factors in the two “non-healthy” patient groups (coronary artery disease patients and CSX patients) may have contributed to the neutrality of the data in our study