• Hypertension · Aug 2000

    Randomized Controlled Trial Clinical Trial

    Nitric oxide and cardiac autonomic control in humans.

    • S Chowdhary, J C Vaile, J Fletcher, H F Ross, J H Coote, and J N Townend.
    • Department of Cardiovascular Medicine, University of Birmingham, UK. S.Chowdhary@bham.ac.uk
    • Hypertension. 2000 Aug 1; 36 (2): 264-9.

    AbstractCardiac autonomic control is of prognostic significance in cardiac disease, yet the control mechanisms of this system remain poorly defined. Animal data suggest that nitric oxide (NO) modulates cardiac autonomic control. We investigated the influence of NO on the baroreflex control of heart rate in healthy human subjects. In 26 healthy male volunteers (mean age, 23+/-5 years), we measured heart rate variability and baroreflex sensitivity during inhibition of endogenous NO production with N(G)-monomethyl-L-arginine (L-NMMA) (3 mg/kg per hour) and during exogenous NO donation with sodium nitroprusside (1 to 3 mg/h). Increases from baseline (Delta) in high-frequency (HF) indexes of heart rate variability were smaller with L-NMMA in comparison to an equipressor dose of the control vasoconstrictor phenylephrine (12 to 42 microg/kg per hour): Deltaroot mean square of successive RR interval differences (DeltaRMSSD)=23+/-32 versus 51+/-48 ms (P<0.002); Deltapercentage of successive RR interval differences >50 ms (DeltapNN50)=5+/-15% versus 14+/-12% (P<0.05); and DeltaHF normalized power=-2+/-7 versus 9+/-8 normalized units (P<0.01), respectively. Relative preservation of these indexes was observed during unloading of the baroreflex with sodium nitroprusside compared with a matched fall in blood pressure produced by a control vasodilator, hydralazine (9 to 18 mg/h): DeltaRMSSD=-8+/-8 versus -24+/-15 ms (P<0.001); DeltapNN50=-6+/-11% versus -15+/-19% (P<0.01); DeltaHF normalized power=-7+/-13 versus -13+/-11 normalized units (P<0.05), respectively. The change in cross-spectral alpha-index calculated as the square root of the ratio of RR interval power to systolic spectral power in the HF band (although not alpha-index calculated in the same way for the low-frequency bands or baroreflex sensitivity assessed by the phenylephrine bolus method) was attenuated with L-NMMA compared with phenylephrine (Delta=4+/-8 versus 14+/-15 ms/mm Hg, respectively; P<0.02) and with sodium nitroprusside compared with hydralazine (Delta=-7+/-6 and -9+/-7 ms/mm Hg, respectively; P<0.05). In conclusion, these data demonstrate that NO augments cardiac vagal control in humans.

      Pubmed     Full text   Copy Citation     Plaintext  

      Add institutional full text...

    Notes

     
    Knowledge, pearl, summary or comment to share?
    300 characters remaining
    help        
    You can also include formatting, links, images and footnotes in your notes
    • Simple formatting can be added to notes, such as *italics*, _underline_ or **bold**.
    • Superscript can be denoted by <sup>text</sup> and subscript <sub>text</sub>.
    • Numbered or bulleted lists can be created using either numbered lines 1. 2. 3., hyphens - or asterisks *.
    • Links can be included with: [my link to pubmed](http://pubmed.com)
    • Images can be included with: ![alt text](https://bestmedicaljournal.com/study_graph.jpg "Image Title Text")
    • For footnotes use [^1](This is a footnote.) inline.
    • Or use an inline reference [^1] to refer to a longer footnote elseweher in the document [^1]: This is a long footnote..

    hide…