The bradycardic response to the Valsalva manoeuvre in normal man

To elucidate whether the Valsalva manoeuvre (VM) can produce a bradycardia instead of well-known tachycardia, a systemic study of the influence of various degrees of strain pressure and lung volumes was undertaken. Six basic patterns beat-to-beat heart rate response (HRR) were seen during the inspiratory graded VM straining with a duration of 25 sec in 75 healthy male subjects (undergraduates) aged 19-28 years. Two patterns were bradycardic, three patterns tachycardic, and one intermediate. The conditions favouring within-strain bradycardia included: completely expanded lungs, low expiratory strain pressure, and a vagotonic state of autonomic reactivity. In order to explore the mechanisms for the bradycardia-type response, in an additional subset of six subjects the instantaneous changes in the arterial mean pressure and vascular resistance were studied. Despite of conspicuous bradycardia the well-known classical four-phase course in blood pressure appeared (Hamilton et al., 1936. J. Am. Med. Assoc. 107, 853-856). We suggest that the nature of HRR to inspiratory VM is determined by the balance between two reflex influences -a vagal reflex from slowly adapting pulmonary stretch receptors and a sympathetic reflex from arterial baroreceptors. It was concluded that the bradycardic HRR to inspiratory VM is a normal event in men with parasympathetic reactivity, particularly when strain pressure is low.