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

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.

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.

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).

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).