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Low Blood Pressure (low + blood_pressure)
Selected AbstractsEthnic (Black-White) Contrasts in 24-Hour Heart Rate Variability in Male Adolescents with High and Low Blood Pressure: The Bogalusa Heart StudyANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2000Elaine M. Urbina M.D. Background: Heart rate variability (HRV) has been used to study autonomic effects on the heart. The time-domain measure RMSSD (root mean square of successive differences) represents high frequency (HF) changes in HRV reflecting parasympathetic nervous system activity (PS). The frequency-domain ratio of low to high power (LF/HF) represents sympathetic (SYMP) to PS balance. In adults, increased SYMP tone has been found in hypertensive as compared to normals. The present study was performed to look for differences in HRV by race and between young subjects with high and low levels of diastolic blood pressure (DBP). Methods: Subjects included 34 healthy males age 13,17 years (53% white). Half were selected with K4 DBP < 85th% for height (HT) measured twice, 3,5 years apart. Half had DBP < 15th% for HT. Subjects underwent a physical examination including BP, HT, WT, and ECG prior to Holter monitor application. HRV data was analyzed from 24-hour Holter recordings obtained during normal activity. Results: The RMSSD was lower in whites compared to blacks for day, night, and 24-hour average (P , 0.05) with day-time measurements showing the largest racial difference. This suggests increased PS tone in blacks especially with activity. The LF/HF ratio was higher in whites for all times, reaching significance during the day (all P , 0.05) suggesting SYMP predominance in whites during activity. Subjects with higher levels of DBP had lower RMSSD and higher LF/HF ratio for all times, but these did not reach statistical significance. Conclusions: There is a trend towards SYMP predominance in children with higher DBP. Healthy white adolescents exhibit increased SYMP tone compared to blacks when measured during normal daytime activity. [source] Vascular reactivity to angiotensin II alone or combined with a thromboxane A2 mimetic in the isolated perfused kidney of Lyon hypertensive ratsFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 1 2002Valérie Oréa The aim of this study was to evaluate whether thromboxane A2 -prostaglandin H2 (TP) receptor activation potentiates the renal vasoconstrictor effect of Angiotensin II (Ang II) in genetically hypertensive rats of the Lyon strain (LH). Concentration-response curves (CRCs) to Ang II (5 pM to 10 nM), to the specific TP receptor agonist U46619 (7.5,960 nM) and to a mixture of Ang II + U46619 (fixed molar ratio of 1 : 9) were obtained in single-pass perfused kidneys isolated from 8 week-old LH and low blood pressure (LL) control rats. Baseline vascular resistance was significantly increased in LH compared to LL kidneys. Comparison of the CRCs obtained for Ang II and U46619 showed that, in both strains, Ang II was about 100 times more potent than U46619. For both drugs, the pD2 or slope values did not differ among the two strains. Co-activation of TP receptors, analyzed with the method of Pöch and Holzmann, tended to potentiate the effects of Ang II in LH but not in LL kidneys. In conclusion, isolated perfused kidneys of LH rat did not exhibit an increased vascular sensitivity to acute infusion of Ang II or U46619 compared to control LL ones. In addition, the results suggest that the interactions between Ang II and TP receptor agonist may differ among the two strains. [source] Improvement in "uremic" cardiomyopathy by persistent ultrafiltrationHEMODIALYSIS INTERNATIONAL, Issue 1 2007Hüseyin TÖZ Abstract Some patients with end-stage renal disease suffer severe cardiac dilatation with functional disturbances, notably low ejection fraction (EF) and valvular regurgitation. They often have normal or low blood pressure, and tolerate ultrafiltration (UF) poorly. The aim of our study was to investigate to what extent this condition can still be improved by persistent slow UF. Twelve patients with cardiothoracic index >0.54 and EF <0.45 but otherwise uncomplicated were treated by slow, prolonged UF during hemodialysis (3 times a week) sessions, if necessary supplemented by isolated UF sessions on a separate day. Repeated chest X-rays and Doppler echocardiography were applied. During treatment periods varying from 20 to 120 days, all of the patients lost weight (12±10 kg) and became edema free. Cardiothoracic index decreased in all patients from a mean of 0.59±0.04 to 0.47±0.03. Blood pressure decreased when it had been elevated and increased when it was below normal. Ejection fraction increased in all of them from a mean of 0.31±0.9 to 0.50±0.9. Mitral and tricuspid regurgitation were found in every patient and disappeared or improved in all of them. Striking improvement of cardiac dilatation and dysfunction can be achieved by carefully monitored persistent UF in the majority of patients with seemingly intractable dilated cardiomyopathy. [source] Cerebral white matter blood flow and arterial blood pressure in preterm infantsACTA PAEDIATRICA, Issue 10 2010Klaus Børch Abstract It is generally assumed that one reason why white matter injury is common in preterm infants is the relatively poor vascular supply. Aim:, To examine whether blood flow to the white matter is relatively more reduced at low blood pressure than is blood flow to the brain as a whole. Methods:, Thirteen normoxic preterm infants had blood flow imaging on 16 occasions with single-photon emission computed tomography (SPECT) using 99Tc labelled hexa-methylpropylenamide oxime (HMPAO) as the tracer. Gestational age was 26,32 weeks. Transcutaneous carbon dioxide was between 4.7 and 8.5 kPa and mean arterial blood pressure between 22 and 55 mmHg. Results:, There was no statistically significant direct relation between white matter blood flow percentage and any of the variables. Using non-linear regression, however, assuming a plateau over a certain blood pressure threshold and a positive slope below this threshold, the relation to white matter flow percentage was statistically significant (p = 0.02). The threshold was 29 mmHg (95% confidence limits 26,33). Conclusion:, Our analysis supports the concept of periventricular white matter as selectively vulnerable to ischaemia during episodes of low blood pressure. [source] Corticosteroid-binding globulin gene polymorphisms: clinical implications and links to idiopathic chronic fatigue disordersCLINICAL ENDOCRINOLOGY, Issue 2 2007D. J. Torpy Summary Corticosteroid-binding globulin (CBG) binds cortisol with high affinity, facilitating transport of cortisol in blood, although tissue-specific CBG,cortisol interactions have long been postulated. There are three heritable, human CBG gene mutations that can reduce CBG,cortisol binding affinity and/or reduce circulating CBG levels. In some families, fatigue and low blood pressure have been associated with affinity altering or CBG level reducing mutations. The limited numbers of reports raise the possibility of ascertainment bias as many cases presented with features suggesting cortisol deficiency. The recent description of a genetically CBG-deficient mouse listed fatigue, manifest as reduced activity levels, as part of the phenotype, which also included immune aberrations. Severe CBG mutations may produce fatigue, but one study suggests that these are a rare cause of idiopathic fatigue. A mechanism for the effect of CBG mutations on fatigue is not readily apparent because free cortisol levels are normal, although we speculate that CBG may have an effect on cortisol,brain transport. [source] | ||||||||||