Mental stress, heart rate and endothelial function in patients with syndrome X.

Background: The aim of the study was to determine whether the baseline heart rate (HR) and changes in HR after mental stress (MS) can influence endothelial function in syndrome X.

Methods: Forty four patients with syndrome X (F/M: 21/23, mean age: 55.4 +/- 10.7 years) were examined. The endothelium-dependent flow-mediated dilation (FMD) was defined as the percentage change in the brachial artery diameter during reactive hyperaemia related to baseline (%FMD). The %FMD was assessed before and after (at 10, 30, and 45 min) standardised three-minute MS. HR and blood pressure were monitored simultaneously. The %FMD values were compared between subgroups characterised by baseline HR, maximum HR and DHR, and HR after MS below and over the median values.

Results: The values of %FMD measured at 10, 30 and 45 min after MS (4.39 +/- 5.4%, 4.99 +/- 3.9%, 4.03 +/- 3.5%, respectively; p < 0.001) were significantly lower than baseline values (7.73 +/- 4.9%). Impaired vasodilatation after MS was observed in the following subgroups of patients: those with baseline HR below the median (< 71.5 bpm; baseline: 8.35 +/- 5.8%; 10 min: 2.87 +/- 3.6%, 45 min: 4.56 +/- 3.9%; p < 0.001); those with HR after MS below the median (< 76.5 bpm; baseline: 8.19 +/- 5.5; 10 min: 3.88 +/- 4.3%, 45 min: 4.59 +/- 3.7%; p < 0.01); and those with maximum HR after MS below the median (< 84 bpm; baseline: 8.88 +/- 5.6%; 10 min: 3.88 +/- 3.8%, 30 min: 5.88 +/- 3.9%, 45 min: 4.51 +/- 3.8; p < 0.01).

Conclusion: The stress-induced endothelial dysfunction syndrome X is related to the baseline HR and the changes in HR after MS, suggesting that the autonomic nervous system plays a part in its pathogenesis. (Cardiol J 2007; 14: 180-185).