Reproducibility of the heart rate response to low-strain Valsalva manoeuvre in healthy subjects.

To elucidate whether the intrastrain cardio-acceleration and cardio-deceleration responses to low-strain Valsalva manoeuvre at expiratory pressures 10 and 20 mmHg (VM10,VM20) are reproducible, a beat-to-beat heart rate study was undertaken in 46 subjects (40 male undergraduates aged 19-25 years and six laboratory workers (four females and two males aged 28-55 years). The intensity of the heart rate response (HRR) was assessed by a ratio of the mean value of the pre-strain heart rate (Valsalva means' ratio VMR). In each subject the HRR to VM10 and VM20 was measured by repeating each manoeuvre three times. Reproducibility was evaluated on a short-term (1 h), medium-term (1 and 6 months), and long-term (6 and 11 years) basis. With the individual differences the initial short-term reproducibility study revealed either an cardio-acceleration or cardio-deceleration response to VM10 and VM20, which persisted well in the repeated tests. On the ground of this result three individual modes of HRRs to VM10 and VM20 were distinguished: (i) Mode A, a deceleration response appeared both to VM10 and VM20; (ii) Mode B, a deceleration response appeared to VM10 and an acceleration response to VM20; (iii) Mode C, an acceleration response appeared both to VM10 and VM 20. All of these modes, as well as the separate acceleration and deceleration responses, were well reproducible at any cited time points. We suggest that the individual modes of HRR are induced by different states of autonomic cardiovascular reactivity: Mode A probably expresses a parasympathotonic (vagotonic), Mode C--a sympathotonic, and Mode B--an intermediate autonomic state. Thus, the individual modes of HRR to VM10 and to VM20 could be used as a method of non-invasive determination of cardiovascular autonomic reactivity. Copyright 2002 Elsevier Science B.V.