August 30, 20196 yr Good question! This systematic review on heart rates in children clearly shows the decline: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3789232/ To be honest, I don't know exactly the underlying mechanisms behind, but I suppose it may be related to both the autonomic drive (symp/parasymp), and that HR is a more important factor for cardiac output during infancy than later in life. Anyone else knowing more of basic physiology than I do ?
August 31, 20196 yr Author On 8/30/2019 at 1:50 PM, Stefan Johansson said: Good question! This systematic review on heart rates in children clearly shows the decline: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3789232/ To be honest, I don't know exactly the underlying mechanisms behind, but I suppose it may be related to both the autonomic drive (symp/parasymp), and that HR is a more important factor for cardiac output during infancy than later in life. Anyone else knowing more of basic physiology than I do ? Thanks for your reply, i just wonder if this physiology involves the frank starling mechanism? or maybe the stroke volume in babies comparing the heart size is small, so to maintain cardiac output they need to increase the heart rate (that's why the pulse is faster) and as the child grows older the stroke volume gets bigger as the heart size is bigger, and the heart rate reduces (pulse slower) to maintain the required cardiac output?
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