The effect of metabolic syndrome on heart rate turbulence in non-diabetic patients

BACKGROUND: Metabolic syndrome (MetS), which includes a cluster of risk factors, is being increasingly recognized as a new risk factor for cardiovascular disease. Heart rate turbulence (HRT) is a Holter-based non-invasive method for detecting cardiac autonomic imbalance and is an independent, powerful predictor of cardiac arrhythmias and sudden cardiac death in different patient groups. This study evaluated the effect of MetS on HRT in non-diabetic patients. METHODS: This study included 80 non-diabetic MetS subjects and 50 healthy subjects. All 130 subjects underwent a 24-h ambulatory Holter electrocardiogram recording. Two indices of HRT were analyzed: turbulence onset (TO) and turbulence slope (TS). HRT values were classified into 3 categories for risk stratification: 1) Category 0, TO and TS were normal; 2) Category 1, either TO or TS was abnormal; 3) Category 2, both TO and TS were abnormal. RESULTS: When we compared MetS rates in the HRT risk stratification groups, there were significant differences for all groups as compared with the controls (Category 0 = MetS 28.8%, n = 15, Control 71.2%, n = 37, p 〈 0.001; Category 1 = MetS 80.8%, n = 42, Control 19.2%, n = 10, p 〈 0.001; Category 2 = MetS 88.5%, n = 23, Control 11.5%, n = 3, p 〈 0.001). In addition, TO and TS abnormalities were correlated with the number of MetS components (r = 0.608, p 〈 0.001; r = -0.388, p 〈 0.001, respectively). CONCLUSIONS: To our knowledge, this is the first study to establish a relationship between HRT and MetS. These findings suggest that MetS adversely affects HRT scores. In addition, the number of MetS components is related to impaired HRT scores.