SUBPRESSOR CALCIUM INFUSION INCREASES ISOVOLUMIC LEFT VENTRICULAR RELAXATION TIME AND ATRIAL NATRIURETIC PEPTIDE IN HUMANS |
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Authors: | Wendy L. Finn Richard D. Gordon Basil I. Seneviratne Terry J. Tunny Shelley A. Klemm |
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Affiliation: | University of Queensland Department of Medicine, Greenslopes Hospital, Brisbane, Australia. |
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Abstract: | 1. Subpressor calcium infusion for 1 h, which raised calcium levels to the upper limit of normal in normal subjects, increased plasma and urinary levels of atrial natriuretic peptide (ANP). 2. Heart rate fell, presumably due to carotid baroreflex stimulation (supported by the fall in noradrenaline) and the resultant fall in cardiac output prevented the expected rise in blood pressure due to the rise in total peripheral resistance (TPR). Thus the increase in ANP was not explained by an increase in blood pressure or noradrenaline. 3. There was no evidence for increased atrial stretch (no increase in atrial area or early velocity of left ventricular filling) as a mechanism for increased ANP. 4. Isovolumic left ventricular relaxation time increased, early velocity of ventricular filling decreased and TPR increased, consistent with increased tone in left ventricular and arteriolar muscle. 5. This suggests a direct effect of calcium on the atrial myocyte, stimulating ANP either through contractile or secretory mechanisms. |
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Keywords: | atrial natriuretic peptide blood pressure calcium infusion cardiac output Doppler echocardiography heart rate isovolumic relaxation time stroke volume total peripheral resistance ventricular fitting. |
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