[Evaluation of the vagal activity by the Deep-Breathing test]

The Deep-Breathing (DB) test is of major importance in the evaluation of the vagal response (VR). We applied this test to assess the VR in a group of subjects with functional (neurological, cardiovascular or digestive) symptoms unexplained by standard cardiac examination and to compare it with the VR measured in a group of healthy controls.

The following groups were considered: a C-Group of healthy controls (n=50), and three groups each consisting of 50 symptomatic patients (S1, S2, S3). Subjects in the S1-Group had a postural orthostatic tachycardia syndrome (POTS), while members of the S2-Group had arterial hypertension, and members of S3-Group had neither POTS nor arterial hypertension. The VR was expressed as a percentage variation of RR intervals 100x[(RR(max)-RR(min))/RR(min)], and was correlated with age and sex in the C-Group before any comparison.

In controls the VR was 31.0%+/-8.2. It was negatively correlated with age (r=-0.42, p=0.003) and there was no significant difference between males (31.2%+/-5.7) and females (30.9%+/-9.0) (p=0.12). Compared to the C-Group, the VR was 51.6%+/-20.4 in the S1-Group (p<0.001), 26.9%+/-11.3 in the S2-Group (p<0.001), and 47.2%+/-22.7 in the S3-Group (p<0.001).

The VR was independent of sex but was negatively correlated with age. In comparison with healthy controls, it was significantly increased in the patients with POTS and significantly decreased in hypertensives.