Differential impact of metabolic syndrome on arterial stiffness and wave reflections: focus on distinct definitions.

Background: Arterial stiffness and wave reflections are independent predictors of cardiovascular disease. Metabolic syndrome (MS) is related to increased aortic stiffness in several populations. However, it is unclear whether the association of MS with aortic stiffness differs according to the considered definition. Moreover, data regarding the association of wave reflections with MS are limited. For this purpose, we examined the relationship of arterial stiffness and wave reflections with MS by using four current definitions and a score.

Methods: We studied 732 never treated, non-diabetic hypertensive patients. Metabolic syndrome was defined by Adult Treatment Panel III, American Heart Association, World Health Organization (WHO), International Diabetes Federation criteria and MS (GISSI) score. Arterial stiffness was assessed by measuring carotid-femoral pulse wave velocity (PWVc-f). Heart rate-corrected augmentation index (AIx(75)) was estimated as a measure of wave reflections.

Results: By all definitions, hypertensive patients with MS had higher PWVc-f compared to hypertensives without MS. On the contrary, no significant difference was observed in AIx(75) between patients with and those without MS except when MS was defined by WHO criteria. An independent association emerged between PWVc-f and GISSI score and MS components (p=0.038 and 0.033 respectively) in patients with MS, after adjustment for age, gender, LDL cholesterol and smoking. Nevertheless, after further adjustment for systolic blood pressure or body mass index, the strength of this association was reduced to a non-significant level.

Conclusion: Arterial stiffness is increased in patients with metabolic syndrome irrespective of the definition criteria. On the contrary, metabolic syndrome has no effect on wave reflections, except when this is defined by WHO criteria. Regarding the high prognostic significance of both arterial stiffness and wave reflections, these findings might have important clinical implications.