The bradycardic response to the Valsalva manoeuvre in normal man

Abstract

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.