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Biomedical subjects

K Narkiewicz

Publications and source records attributed to K Narkiewicz.

At least 55 records · Page 3Linked to original sources
PubMed1998

Contribution of tonic chemoreflex activation to sympathetic activity and blood pressure in patients with obstructive sleep apnea.

BACKGROUND: Muscle sympathetic nerve activity (MSNA) is increased in patients with obstructive sleep apnea (OSA). We tested the hypothesis that tonic activation of excitatory chemoreceptor afferents contributes to the elevated sympathetic activity in OSA. METHODS AND RESULTS: Using a double-blind, randomized, vehicle-controlled design, we examined the effects of chemoreflex deactivation (by comparing effects of breathing 100% oxygen for 15 minutes with effects of breathing room air for 15 minutes) on MSNA, heart rate, blood pressure, and minute ventilation in 14 untreated patients with OSA and in 12 normal subjects matched for age and body mass index. All control subjects underwent overnight polysomnography to exclude the existence of occult OSA. Baseline MSNA was markedly elevated in the patients with OSA compared with the control subjects (44+/-4 versus 30+/-3 bursts per minute; P=.01). In both control subjects and patients with OSA, heart rate decreased during administration of 100% oxygen but did not change during administration of room air. By contrast, both MSNA (P=.008) and mean arterial pressure (P=.02) were significantly reduced during chemoreflex deactivation by 100% oxygen only in patients with OSA but not in control subjects. CONCLUSIONS: Tonic activation of excitatory chemoreflex afferents may contribute to increased efferent sympathetic activity to muscle circulation in patients with OSA.

Adult↗
PubMed1998

Baroreflex control of sympathetic nerve activity and heart rate in obstructive sleep apnea.

-Patients with obstructive sleep apnea are at increased risk for hypertension. The mechanisms underlying this increased risk are not known. We tested the hypothesis that obstructive sleep apnea, independent of factors such as hypertension, obesity, and age, is characterized by impairment of baroreflex sensitivity. We measured muscle sympathetic nerve activity (MSNA) and heart rate responses to activation and deactivation of baroreceptors in newly diagnosed, never treated, normotensive patients with obstructive sleep apnea. These responses were compared with those obtained in healthy control subjects closely matched for age, body mass index, and blood pressure. Heart rate and MSNA changes during infusion of phenylephrine (baroreceptor activation) were similar in the control subjects and patients with sleep apnea. Infusion of nitroprusside (baroreceptor deactivation) elicited similar decreases in mean arterial pressure (MAP) but lesser MSNA increases in patients with sleep apnea than in control subjects. Calculation of DeltaMSNA/DeltaMAP ratio revealed that baroreflex regulation of sympathetic activity for similar blood pressure changes was diminished in patients with sleep apnea in comparison to normal control subjects (P=0.01). However, increases in heart rate during nitroprusside infusion were comparable in both groups. Sympathetic, blood pressure and heart rate responses to the cold pressor test were also similar in the 2 groups. Our results indicate that normotensive patients with sleep apnea have a selective impairment of the sympathetic response to baroreceptor deactivation but not to baroreceptor activation or to the cold pressor test. The impairment of baroreflex sympathetic modulation in patients with sleep apnea is not accompanied by any impairment of baroreflex control of heart rate.

Airway Obstruction↗
PubMed1998

Ambulatory systolic blood pressure is related to the deletion allele of the angiotensin I converting enzyme gene in young normotensives with parental history of hypertension.

The aim of the present study was to evaluate the relationship between the angiotensin I converting enzyme (ACE) gene polymorphism and ambulatory blood pressure in young normotensive males with (n=45) and without (n=100) family history of hypertension. Twenty-four hour and daytime systolic blood pressure was significantly higher in subjects with a parental history of hypertension. Ambulatory blood pressure values did not differ significantly across ACE genotypes in subjects with negative family history of hypertension. In subjects with a parental history of hypertension, there was a significant positive association between the D allele of the ACE gene polymorphism and 24-h, daytime and nighttime systolic blood pressure. For twenty-four hour systolic blood pressure there was an average 9 mmHg difference between subjects with DD and II genotypes. The results indicate that in normotensive subjects with a genetic predisposition to hypertension, ambulatory systolic blood pressure is related to the D allele of the ACE gene.

Adult↗
PubMed1998

[Polymorphism of the ACE gene and left ventricular morphology and function in patients with borderline, mild and moderate hypertension].

It has been reported that the allel D of an insertion/deletion (I/D) polymorphism of the angiotensin I converting enzyme (ACE) gene is associated with the conditions of increased cardiovascular risk, including the left ventricular hypertrophy and the dysfunction. We examined the relation between the genotype of ACE gene and the left ventricular function in normotensives and in borderline, mild and moderate hypertensives. We investigated 128 subjects, 47 first-diagnosed untreated hypertensives and 81 normotensives. The M-mode and Doppler echocardiography were used to quantify LV mass and function. The insertion/deletion ACE polymorphism was identified using polymerase chain reaction. Left ventricular indexes of the morphology and function were analyzed. We compared ambulatory blood pressure profiles between all genotypes in both groups. There were no significant differences in indexes of the left ventricular hypertrophy in studied normotensives and borderline to mild hypertensives. Our results indicate that allel I might be associated with selected parameters of diastolic function, while allel D with selected parameters of systolic function, of the left ventricle. Results of this study suggest also probable relation between allel D and variability of the diastolic arterial pressure in both investigated groups.

Adult↗
PubMed1998

[The influence of 5-week relaxation therapy on arterial blood pressure in patients with borderline hypertension].

The present study was performed to evaluate the influence of 5-week relaxation therapy on office and ambulatory blood pressure in young borderline hypertensives. Thirty patients were studied. The office blood pressure decreased significantly after 5 weeks of relaxation therapy (P < 0.001 for both systolic and diastolic blood pressure). Ambulatory monitoring revealed only a slight decrease of 24-hour blood pressure (P = 0.02). Our results indicate limited efficacy of relaxation therapy in treatment of borderline hypertensives.

Adult↗
PubMed1998

[The influence of 5-week relaxation therapy on psychological state of patients with borderline hypertension].

The aim of the present was to evaluate the influence of 5-week relaxation therapy on psychic state of patients with borderline hypertension. The study group consisted of 30 hypertensives. We observed significant changes in anxiety scale, defensiveness, self-confidence, intraception, nurturance, affiliation, heterosexuality, change and succorance scales. In conclusion, 5-week relaxation changes significantly psychological status of patients with borderline hypertension.

Adult↗
PubMed1997

Genetic influences on insulinemia in normotensive twins.

The aim of this study was to establish the contribution of genetic factors to the variance of plasma insulin concentration in healthy, normotensive twins. Seventeen pairs of monozygotic (MZ) and 17 pairs of dizygotic (DZ) twins were investigated. The test of genetic variance revealed a significantly larger within-pair variance of fasting plasma insulin (FPI) and a relative insulin resistance (RIR) in the DZ twins, in comparison with the MZ twins. Both FPI and RIR had a higher intraclass correlation coefficient in the MZ twins than in the DZ twins; the corresponding heritability estimates were 0.54 for FPI and 0.66 for RIR. Adjusting for age, gender, and body mass index did not affect heritability estimates for either FPI or RIR. Our data indicate that genetic factors are important determinants of insulinemia in normal subjects, independent of body mass index.

Adolescent↗
PubMed1997

No effect of genetic variation at the angiotensinogen locus on ambulatory blood pressure level in normotensive subjects.

The aim of the study was to evaluate the potential association between ambulatory blood pressure and the molecular variants T174M and M235T of the angiotensinogen gene in a random sample of young normotensive men (n = 145). The two point mutations were detected using restriction digests of a mispairing polymerase chain reaction product. Twenty-four-hour ambulatory blood pressure monitoring was performed with a SpaceLabs 90207 device. Ambulatory blood pressure levels did not vary according to T174M and M235T genotypes. When the subjects were grouped according to their blood pressure level (as indicated by tertiles of their 24-h ambulatory blood pressure), no significant differences in allele frequencies between the three groups were found. Our results indicate that the T174M and M235T molecular variants of the angiotensinogen gene have no major influence on ambulatory blood pressure in young normotensive subjects.

Adult↗
PubMed1997

The sympathetic nervous system and obstructive sleep apnea: implications for hypertension.

Patients with obstructive sleep apnea experience repetitive apneic events during sleep, with consequent hypoxia and hypercapnia. Hypoxia and hypercapnia, acting via the chemoreflexes, elicit increases in sympathetic nerve activity. The sympathetic responses to hypoxia and hypercapnia are potentiated during apnea, when the sympathetic inhibitory influence of the thoracic afferent nerves is eliminated. As a consequence of the sympathetic vasoconstrictor response to apneic events, patients with obstructive sleep apnea manifest marked increases in blood pressure during sleep, especially evident at the end of the apnea. The increases in sympathetic activity and blood pressure during sleep in these patients appear to carry over into the daytime such that patients with sleep apnea have an increased prevalence of hypertension and high levels of sympathetic nerve activity. Although the mechanism underlying the persistent elevation in sympathetic activity during the daytime is not known, it is likely that the increased sympathetic drive is implicated in the higher daytime blood pressures in these patients. Whereas patients with sleep apnea have an increased prevalence of hypertension, in those patients with sleep apnea who do have hypertension, the sympathetic response to apneic events may be potentiated. This may be secondary to impaired baroreflex sensitivity, since the baroreflexes exert an inhibitory influence on the chemoreflex responses to hypoxia. Treatment with continuous positive airway pressure results in an acute reduction in blood pressure and sympathetic activity during sleep. Prolonged effective treatment of sleep apnea may also reduce daytime blood pressure levels. This review examines the physiology of the chemoreflex responses to hypoxia, hypercapnia and apnea, as well as the physiologic responses to sleep in normal humans. These physiologic responses are compared with the pathophysiologic sympathetic and hemodynamic responses that characterize obstructive sleep apnea. Increases in sympathetic activity and blood pressure in patients with obstructive sleep apnea may play a role in linking sleep apnea to hypertension and cardiac and vascular events.

Baroreflex↗
PubMed1997

Endurance training in mild hypertension - effects on ambulatory blood pressure and neural circulatory control.

This review examines the effects of a single bout of exercise and of endurance training on blood pressure in patients with hypertension. Possible autonomic mechanisms that mediate these changes in blood pressure are reviewed briefly. Blood pressure rises during exercise. During the second half hour after exercise blood pressure is lower. This p;ost-exercise reduction in blood pressure is associated with a decrease in muscle sympathetic nerve activity, an increase in baroreflex gain and a reduction in the level of blood pressure (set point) at which baroreflex activation occurs. The post-exercise fall in blood pressure appears to be limited to several hours and is not likely to explain any chronic reduction in blood pressure from endurance training. Endurance training elicits modest (approximately 4-5 mmHg) reductions in blood pressure. Because of the intrinsic variability of blood pressure, the decreases in blood pressure after endurance training is evident, especially when multiple measurements of blood pressure are obtained. Studies using 24 h blood pressure measurements suggest that, although endurance training lowers daytime blood pressure, blood pressure during sleep remains unchanged. The mechanism underlying the reduction in blood pressure in endurance training is not known. Although physical fitness is known to attenuate the sympathetic response to acute exercise, whether resting sympathetic drive is decreased with endurance training remains controversial. The slowing of heart rate that accompanies endurance training is also associated with an increase in variability of heart rate. The slower heart rate, increased variability of heart rate and lower blood pressure after endurance training are accompanied by an increase in baroreflex sensitivity. Even though the antihypertensive effect of endurance training is modest, the favourable effects of physical fitness on other risk factors for cardiovascular disease make exercise training an important approach in the management of hypertensive patients, particularly for sedentary patients with borderline and mild hypertension.

Journal Article↗
PubMed1996

[Significant negative correlation between fasting plasma insulin and ambulatory blood pressure in patients on chronic hemodialysis].

Positive correlation between blood pressure and insulin is well established in patients with essential hypertension. The aim of the present study was to examine the relationship between fasting plasma insulin level and ambulatory blood pressure (ABPM) in patients with chronic renal failure. The study group consisted of 20 patients (11 females, 9 males, mean age 39 +/- 12 years) on chronic haemodialysis (mean 2.5 years). Fasting plasma insulin (FPI) was measured by radioimmunoassay. The patients were investigated before and after haemodialysis. FPI significantly increased after haemodialysis from 18.4 +/- 12.0 to 40.1 +/- 31.9 mIU/l (p < 0.01), while creatinine concentration decreased from 1158 +/- 130 to 910 +/- 159 mumol/l (p < 0.001). Night-time systolic blood pressure (SBP) was significantly lower during the day of haemodialysis (141.9 +/- 19.6 mmHg vs. 136 +/- 27.7 mmHg, p < 0.05). 24-hour and daytime SBP was nonsignificantly lower after haemodialysis. 24-hour diastolic blood pressure (DBP) was significantly lower during the day of haemodialysis (92.9 +/- 12.5 mmHg vs. 87.3 +/- 14.3 mmHg, p < 0.05), as well as daytime (94.9 +/- 12.1 mmHg vs. 88.8 +/- 14.6 p < 0.05) and night-time DBP (88.9 +/- 16.0 mmHg vs. 83.8 +/- 17.4 mmHg p < 0.05). FPI was found to be significantly negatively correlated with 24-hour, daytime and night-time SBP on the day of haemodialysis (r = -0.63, p < 0.005; r = 0.64, (p < 0.005 and r = -0.54, p < 0.05, respectively). The significant negative correlation between FPI and 24-hour SBP suggests that insulin could reveal its hypotensive effect after the haemodialysis.

Adult↗
PubMed1996

Awareness and treatment of arterial hypertension in Poland.

In order to find out the general public's opinion on blood pressure (BP) control in Poland a poll was conducted on a representative sample of 2080 randomly selected subjects. Overall 71% of the subjects were aware of their BP level. The awareness of BP level increased progressively with age and education level. Among those who were aware of their BP level, 21% had hypertension. Only 43% of hypertensives were treated on a regular basis. Cigarettes were smoked by 33% of the patients. Only 16% of the hypertensives used a low-salt diet, and only 31% tried to reduce animal fat in their diet. More than a half of the hypertensives did not adjust their lifestyle and daily habits to the disease. In conclusion, these results indicate that the prevention and treatment of hypertension in Poland should be urgently improved.

Adolescent↗
PubMed1996

Ambulatory blood pressure and insulinaemia in different clinical conditions.

The aim of our study was to examine the relation between insulin and ambulatory blood pressure (ABPM) in several clinical conditions. ABPM monitoring was performed with Spacelabs device. Fasting plasma insulin (FPI) was measured by radioimmunoassay. In young, non-obese normotensive subjects (n = 32) there were correlations between FPI and both asleep (r = 0.61, p < 0.001), and awake systolic ABPM (r = 0.44, p < 0.01). We have not observed any significant correlation between FPI and ABP in borderline hypertensives or in patients with established hypertension. In a group of 21 hypertensive type 2 diabetics (age 52 +/- 8 years) there was no significant correlation between FPI and ABPM. Among 14 normotensive type 1 diabetics (age 31 +/- 7 years, diabetes duration > 10 years) there was a significant negative correlation between the daily dose of insulin and 24-h systolic ABPM (r =-0.63, p < 0.02). In 20 patients with renal failure on chronic haemodialysis we have found a significant negative correlation between FPI and 24-h systolic APBM (r = 0.80, p < 0.001) and 24-h diastolic ABPM (r = -0.55, p < 0.05). Similar negative correlations were found in 20 nondialysed subjects with moderate chronic renal failure. Taken together, our results suggest that insulin could reveal its hypertensive or vasodilatory effect which depends on a clinical condition of the studied subjects.

Adult↗
PubMed1995

Ambulatory blood pressure in mild hypertensive women taking oral contraceptives. A case-control study.

The aim of the present study was to compare the ambulatory blood pressure levels in mild (stage 1) hypertensive women using oral contraceptives and respective values in nonusers of oral contraceptives with similar office blood pressure. The study group consisted of 24 mild hypertensive patients taking low dosage estrogen-progestogen oral contraceptives. Seventy women of similar age and body mass index who had never used oral contraceptives served as a control group. Both daytime and nighttime systolic blood pressure values were significantly higher in oral contraceptive users. There was an average 8.3 mm Hg difference (95% confidence interval, 3.0 to 13.7 mm Hg; P = .003) for the daytime and 6.1 mm Hg difference (95% confidence interval, 0.4 to 11.8 mm Hg; P = .04) for the nighttime. No significant differences in ambulatory diastolic blood pressure between the two groups were found. These data provide evidence that hypertensive oral contraceptive users with the same office blood pressure as that in hypertensive noncontraceptive users have a significantly higher ambulatory systolic blood pressure. Our results support the opinion that alternative methods of contraception should be considered for hypertensive women in place of oral contraceptives.

Adolescent↗
PubMed1995

Interactive effect of cigarettes and coffee on daytime systolic blood pressure in patients with mild essential hypertension. HARVEST Study Group (Italy). Hypertension Ambulatory Recording VEnetia STudy.

OBJECTIVE: To test the hypothesis that moderate smoking (fewer than 20 cigarettes/day) and coffee consumption have an interactive effect on ambulatory blood pressure. DESIGN: A case-control study. SETTING: Patients in the multicentre Hypertension Ambulatory Venetia Study, northeastern Italy. SUBJECTS: Six hundred and forty-three men and 244 women with borderline-to-mild status (non-smokers versus smokers) and their habitual consumption of coffee (0, 1-3, or 4+ cups/day). MAIN OUTCOME MEASURES: Office blood pressure, ambulatory blood pressure, urinary adrenaline and noradrenaline levels according to smoking status, coffee consumption and their interaction. RESULTS: In the men, daytime systolic blood pressure (SBP) was significantly higher in the smokers than in the non-smokers and in the coffee drinkers than in the others. Moreover, two-way analysis of covariance revealed a significant interaction between smoking status and coffee consumption: the daytime SBP in smokers who drank 4+ cups/day of coffee was 6.0 mmHg higher than that of non-smokers who abstained from coffee. Conversely, office blood pressure was lower in the smokers than in the non-smokers and was similar in the coffee drinkers and the others. Coffee consumption had a significant effect on urinary adrenaline. Similar results were obtained in the women. CONCLUSIONS: In contrast with what is shown by office blood pressure measurement, moderate smokers and coffee drinkers with mild hypertension have significantly higher daytime SBP levels than non-smokers and those who do not drink coffee. Cigarettes and coffee have an interactive effect on daytime SBP in young patients, with mild essential hypertension.

Adolescent↗
PubMed1995

Response to orthostatic stress predicts office-daytime blood pressure difference, but not nocturnal blood pressure fall in mild essential hypertensives: results of the harvest trial.

1. The aim of the present study was to evaluate whether postural blood pressure (BP) change could predict office-day-time BP disparity and the nocturnal BP fall in young, mild essential hypertensives. We investigated 411 males aged between 18 and 45 years with never treated borderline to mild hypertension. BP was measured three times after a 5 min rest in the supine position and thereafter three times after 2 min of standing. The mean of six BP measurements obtained during two visits in the lying position was defined as office BP. 2. Twenty-four hour ambulatory BP monitoring was performed with either the A&D TM-2420 model 7 or the ICR Spacelabs 90207. BP values were averaged for day- and night-time periods. The nocturnal BP fall was defined as the difference between the average day- and night-time BP. 3. The standing-lying difference was significantly inversely correlated with the office-daytime difference for both systolic blood pressure (SBP) (r = -0.34, P < 0.001) and diastolic blood pressure (DBP) (r = -0.24, P < 0.001). These correlations did not change when the obese subjects (body mass index > 30 kg/m2) were excluded from the analysis. No significant correlation between standing-lying difference and nocturnal BP fall was found. 4. Our results indicate that white coat hypertension assessed as the office-daytime BP disparity is partially related (in a negative fashion) to the BP reaction to standing. The postural BP change does not predict nocturnal BP fall in young, mild essential hypertensives.

Adult↗
PubMed1995

Relation between family history of hypertension, overweight and ambulatory blood pressure: the HARVEST study.

The aim of the present paper was to evaluate the influence of a family history of hypertension and the degree of obesity as indicated by tertiles of body mass index on ambulatory blood pressure (BP) values in large number (n = 406) of young mild essential hypertensives. Positive family history of hypertension was associated with a significant increase in 24h ambulatory systolic blood pressure (SBP). The difference was most pronounced in the upper tertile of body mass index with almost 6 mm Hg difference between patients with and without a family history of hypertension. Both the degree of obesity and family history of hypertension had significant effects on 24h diastolic blood pressure (DBP). Twenty four hour DBP was highest in the upper tertile of body mass index in the hypertensives with a positive family history, representing an increase of 5 mm Hg compared with patients with a negative family history in the lower tertile. We conclude that mild hypertensives with a positive family history of hypertension are characterised by higher ambulatory BP than patients without parental hypertension and similar supine BP. Furthermore, our results indicate that in mild hypertensives the increase in DBP with body mass index is underestimated by conventional sphygmomanometry.

Adult↗