226 PROLONGATION OF QT DISPERSION INDUCED BY MENTAL ARITHMETIC STRESS IN ESSENTIAL HYPERTENSIVES COMPLICATED WITH METABOLIC SYNDROME

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Objectives: Psychological stress can increase QT dispersion (QTd), thereby increasing risk for arrhythmia and sudden death especially in coronary heart disease. The present study was designed to examine stress-induced alterations of QTd in essential hypertensives (EHT) complicated with metabolic syndrome (Mets), characterized as high risk for cardiovascular disease. Design and methods: Systemic hemodynamics, plasma noradrenaline and QTd (i.e., difference between maximum and minimum QT interval on electrocardiogram) were evaluated during rest and after a 10-min arithmetic stress in 92 consecutive untreated EHT. The data were compared between 42 EHT with Mets and 50 EHT without Mets (non-Mets). Results: Blood pressure, plasma norepinephrine and QTd did not differ between Mets and non-Mets during rest, although pulse rate was higher in Mets compared with non-Mets. Following arithmetic stress, plasma norepinephrine increased in both Mets and non-Mets (228±12 to 299±13 and 217±12 to 261±12 pg/mL), but its increase was greater in Mets than in non-Mets (p<0.05 for group×stress interaction). Concomitantly, QTd increased in Mets (59±5 to 75±5 msec), but it remained unchanged in non-Mets (59±4 to 62±4 msec) (p<0.05 for group×stress interaction). Thus, stress-induced change in QTd was larger in Mets compared with non-Mets. In contrast, blood pressure and pulse rate increased to the similar extent after arithmetic stress in both groups. Conclusion: Mental arithmetic stress induced prolongation of QT dispersion along with exaggerated activation of sympathetic neural activity in EHT with Mets.

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