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Biomedical subjects

G A van Montfrans

Publications and source records attributed to G A van Montfrans.

At least 19 recordsLinked to original sources
PubMed2006

[The most recent study into blood pressure lowering by amlodipine: the beginning of the end for the beta-blockers].

In the 'Anglo-Scandinavian cardiac outcomes trial-blood pressure lowering arm' (ASCOT-BPLA), a regimen ofamlodipine and perindopril was compared with a classic regimen of atenolol and bendroflumethiazide in over 19,000 hypertensive subjects. Most likely related to a lower systolic blood pressure, a better metabolic profile and inferiority of the comparator atenolol, the trial showed better outcomes for total and cardiovascular mortality, fatal and nonfatal stroke and cardiovascular events and procedures for the combination of newer agents. Additionally, the newer combination was associated with a 30% reduction in new-onset diabetes mellitus. It is expected that these newer drugs will quickly replace the beta-blockers as the medication for patients with high blood pressure.

Adrenergic beta-Antagonists↗
PubMed2005

[Atenolol or metoprolol as beta-blocker in the treatment of hypertension].

Recently the guideline committee of the Dutch College of General Practitioners advocated the use of metoprolol instead of atenolol in patients with an indication for beta-blockers. This recommendation was based on a recent meta-analysis in The Lancet in which no effect was observed in favour ofatenolol compared with placebo on all-cause mortality, cardiovascular mortality and myocardial infarction. Atenolol also had a higher total mortality and stroke risk compared with other antihypertensive agents. Apart from the presence of statistical heterogeneity and the inappropriate use of a fixed-effect model, the studies referred to in this meta-analysis were also clinically heterogeneous. Furthermore, in most studies, only older patients were included. In older patients with hypertension, it is known that beta-blockers are less effective than diuretics or calcium antagonists. Comparative trials between atenolol and metoprolol in the treatment of hypertension have not been performed with regard to cardiovascular endpoints. We conclude that there is no evidence that atenolol is better or worse than metoprolol in the treatment of the hypertensive patient. For the treatment of patients with heart failure, however, lipophilic beta-blockers such as metoprolol may be preferred, as these drugs have been more thoroughly evaluated for this indication.

Adrenergic beta-Antagonists↗
PubMed2004

[The practice guideline 'Hypertension' (third revision) from the Dutch College of General Practitioners; a response from the perspective of internal medicine].

The revised practice guideline on hypertension from the Dutch College of General Practitioners is a useful document for the management of hypertension. The decision to limit antihypertensive treatment to patients with at least a 20% risk of developing cardiovascular disease within 10 years may, however, be criticised. Prolonged untreated mild hypertension may lead to macro- and microvascular myocardial sclerosis and disturbed systolic and diastolic function of the left ventricle. A 10% risk is preferred. On the other hand, case-finding and treatment of patients with hypertension will increasingly be a major time-consuming activity in general practice. This calls for a change in organisation: well-trained vascular assistants should be employed to fulfill most of this task.

Antihypertensive Agents↗
PubMed2004

[Routine funduscopic examination in hypertensive patients not useful].

Funduscopic examination according to the classification of Keith, Wagener and Barker has been used since 1939 to assess retinal damage in patients with hypertension. Improved treatment possibilities and the screening of patients with hypertension seem to have led to a decrease in the incidence and severity of the retinal abnormalities found. The following findings have been published during the past ten years. The assessment of retinopathy is subject to a large interobserver-variability, especially with respect to venous-crossings and arteriolar narrowing of retinal vessels. The positive and negative predictive value of retinopathy for high blood pressure is low. The association of retinopathy with other predictive indicators for organ damage is inconsistent and its association with cardiovascular complications is weak. These findings indicate that the usefulness of funduscopic examination as an instrument for assessing organ damage in patients with hypertension is limited. Therefore it should not be used as a routine diagnostic tool unless a hypertensive crisis is indicated.

Female↗
PubMed2004

[Hypertension in young adults: indication for possible aortic coarctation].

Three adult patients, a woman aged 37 and two men aged 22 and 23 years respectively, were admitted due to an unexplained hypertension. After a significant delay, the diagnosis of aortic coarctation was established for these patients. In two of them the abnormality was operatively corrected and the blood pressure subsequently normalised; the third patient is on the waiting list for the operation. In all three patients an earlier diagnosis could have been established, had accurate blood-pressure measurements of both arms and at least one leg been performed. Late detection and treatment of aortic coarctation have a profound detrimental effect on survival. Therefore it is extremely important to accurately measure the blood pressure in the limbs of young patients with hypertension.

Adult↗
PubMed2004

Serial assessment of cardiovascular control shows early signs of developing pre-eclampsia.

PURPOSE: To evaluate whether differences in autonomic cardiovascular control between normal pregnant women and women who develop pre-eclampsia later in pregnancy can be detected even before or early in pregnancy. DESIGN: We studied 42 women, 21 multigravid with a history of pre-eclampsia and 21 primigravid, before pregnancy, at 6, 8, 12, 16, 20 and 32 weeks gestation and 15 weeks after delivery. METHODS: The outcome of pregnancy was classified after delivery as normal pregnancy (NP group) or pre-eclampsia (PE group). Continuous heart rate and blood pressure were recorded by Portapres (TNO, Amsterdam, The Netherlands) during orthostatic stress, during rest in a supine and sitting position, and during paced breathing for periods of 1 min at breathing frequencies of 6, 10 and 15 breaths/min. Baroreflex gain from heart rate and blood pressure variability and the phase angle between both signals at low (approximately 0.1 Hz) and high frequency (respiratory rate) were analyzed by spectral analysis. RESULTS: Eight women were diagnosed with pre-eclampsia. Subgroups did not differ in age, weight or height. The PE group showed a significantly higher mean arterial pressure before and during pregnancy [analysis of variance (ANOVA), P = 0.001], a significantly larger initial blood pressure drop to orthostatic stress before and in the first half of pregnancy (ANOVA, P = 0.002) and a significantly larger negative phase difference during supine rest at low frequency from 8 weeks onward (ANOVA P = 0.003). CONCLUSIONS: These findings are compatible with increased resting sympathetic activity and decreased circulating volume, already present before and early in pregnancy, in women who will later develop pre-eclampsia.

Adult↗
PubMed2003

Home versus Office blood pressure MEasurements: Reduction of Unnecessary treatment Study: rationale and study design of the HOMERUS trial.

The Home versus Office MEasurements, Reduction of Unnecessary treatment Study (HOMERUS) is a multicentre prospective study, primarily designed to examine in subjects with mild to moderate hypertension whether treatment decisions based on home blood pressure measurements can lead to reduction in the use of antihypertensive drugs and the associated costs, compared to office blood pressure measurements. After inclusion, 360 patients are randomized to two groups. In one group, antihypertensive therapy is based on blood pressure measured in the outpatient clinic: the office pressure (OP) group. In the other group, antihypertensive therapy is based on home blood pressure measurements: the self-pressure (SP) group. All readings, both in OP and in SP, are obtained with the same validated oscillometric device, the Omron 705 CP. Treatment decisions are taken by an independent physician at the coordinating centre, who is unaware whether the patient belongs to the SP or OP group. Following a standardized treatment schedule, blood pressure is targeted at 120-139 mmHg for systolic and 80-89 mmHg for diastolic pressure. Patients are followed for 1 year. At the start and at the end of the study, ambulatory blood pressure measurements are obtained as a reference. Microalbuminuria and echocardiography are assessed to evaluate the possible development of target organ damage. It is expected that, at the end of the trial, patients in both groups will have the same blood pressure, at the expense of more medication in the OP group. Therefore, a cost-minimization analysis will be performed first. If short-term effects appear not to be comparable for OP and SP, a cost-effectiveness analysis will be performed to assess the value of the SP strategy in comparison to standard practice. In addition, medication compliance is recorded within random subgroups of the SP and OP groups by means of Medication Event Monitoring System (MEMS) V TrackCaps.

Algorithms↗
PubMed2001

Circadian rhythms in systemic hemodynamics and renal function in healthy subjects and patients with nephrotic syndrome.

BACKGROUND: The resemblance of the circadian rhythm of glomerular filtration rate (GFR) to that of arterial blood pressure (BP) suggests that systemic hemodynamic factors contribute to this variation. In the present study, this was investigated using continuous BP monitoring and pulse wave analysis. The study was performed in eight healthy subjects and in seven patients with nephrotic syndrome who had normal or reversed rhythms of GFR. METHODS: Circadian variations of renal function (continuous infusion of inulin/paraaminohippuric acid), noninvasive finger arterial pressure (Portapres), and vasoactive hormone levels were monitored during 27 hours. With stepwise backward regression analysis, the contributions of the measured variables to the circadian variation of GFR were investigated. RESULTS: Both groups showed a reduction of BP at night. In the controls, this was related to a drop in cardiac output, while in the patients, total peripheral resistance decreased at night. None of the hemodynamic variables explained the circadian GFR variation in both groups. In the controls, only 6% of the effective renal plasma flow (ERPF) rhythm was associated with variations in cardiac output (P = 0.03). In the patients, atrial natriuretic peptide and plasma renin activity were responsible for 36% of the variation in GFR (P < 0.01). CONCLUSIONS: These results indicate that the circadian variation of GFR does not result directly from changes in BP or cardiac output. An inverted GFR rhythm in patients with nephrotic syndrome may originate from hormonal mechanisms rather than directly from the hemodynamic effects of edema mobilization.

Adult↗
PubMed2001

Comparison of the time courses and potencies of the vasodilator effects of nifedipine and felodipine in the human forearm.

In a previous study we investigated the differential time courses of the vasodilator effect of various calcium antagonists (CA) in small isolated rat mesenteric arteries (van der Lee et al., Fundam Clin Pharmacol, 1998: 12: 607-12). We concluded that the differences observed could be due to differences in lipophilicity between the CA studied. A measure for lipophilicity is the logarithm of the membrane-partition coefficient (log P). The log P values of nifedipine and felodipine are 2.50 and 4.46, respectively. It was the aim of the present study to compare the time courses of nifedipine and felodipine effects by means of forearm venous occlusion plethysmography in healthy subjects. Healthy male non-smoking volunteers (age 31 +/- 7 years, n = 14) were studied. Informed consent was obtained prior to each experiment from all subjects. The study commenced with the vehicle of either CA (NaCl 0.9% or a PEG400-solution for nifedipine and felodipine, respectively). In four subsequent runs, increasing concentrations of CA were studied for 20 min each, at an infusion rate of 0.3 ml/min. During experiments both hands were excluded from the circulation using small wrist cuffs, inflated to at least 40 mmHg over systolic blood pressure. Mean arterial pressure remained stable in all subjects (88 +/- 3 and 83 +/- 3 mmHg for nifedipine and felodipine, respectively), thus a systemic effect of the CA was not likely. Log IC50 values were -7.46 +/- 0.17 and -8.47 +/- 0.14 for nifedipine and felodipine, respectively (p < 0.01). Averaged KD values were 4.3 +/- 0.6 and 4.6 +/- 0.6 for nifedipine and felodipine, respectively (n.s.). In this model, felodipine appears to be a more potent vasodilator than nifedipine. The 100-fold difference in lipophilicity between the two CA tested is apparently not sufficient to cause major differences in K(D) values in the plethysmography experimental set-up.

Adolescent↗
PubMed2001

Maternal nutrition during gestation and blood pressure in later life.

OBJECTIVE: To assess the link between maternal diet during pregnancy and blood pressure of the offspring. DESIGN: Follow-up study. SETTING: A university hospital in Amsterdam, The Netherlands. PARTICIPANTS: People born at term as singletons between November 1943 and February 1947. MAIN OUTCOME MEASURE: Blood pressure at adult age. RESULTS: Adult blood pressure was not associated with protein, carbohydrate or fat intake during any period of gestation. We found, however, after adjustment for sex that the systolic blood pressure decreased by 0.6 mmHg (0.1-1.1) for every 1% increase in protein/carbohydrate ratio in the third trimester. This association was present both in people who had been exposed to the famine during gestation as well as in those who had not been exposed. The association between protein/carbohydrate ratio in the third trimester and adult blood pressure was furthermore independent of maternal weight gain and final weight, and birth weight [increase for every 1% increase in protein/carbohydrate ratio 0.6 mmHg (0.0-1.2)]. Adjustment for adult characteristics such as body mass index, smoking and socio-economic status did not affect the observed association appreciably [adjusted increase 0.5 mmHg (0.0-1.0)]. CONCLUSION: Adult blood pressure seems to be affected by small variations in the balance of macro-nutrients in the maternal diet during gestation rather than by relatively large variations in the absolute amounts.

Adult↗
PubMed2001

Oscillometric blood pressure measurement: progress and problems.

Oscillometric blood pressure measurement has become very popular, but although a number of devices have now passed both the Association for the Advancement of Medical Instrumentation and British Hypertension Society criteria, complacency with the state of the technique is as yet premature. In individual subjects, a substantial number of readings may deviate more than a clinically relevant 5 mmHg in devices that have earned a British Hypertension Society grade A rating. The marketing of pressure-wave-simulating devices is a welcome development as monitors can now be tested for reproducibility; an intra-device standard deviation of less than 2 mmHg has been proposed as the limit. Authors suggest that these simulators are currently better suited to intra- than between-device testing since they are not yet fully confident that the simulated waveforms are indistinguishable from the man-made pressure waves. Simulators should, however, be incorporated into our standard validation protocols in order eventually to obviate the human, fallible, factor in the validation protocols. The currently employed maximal amplitude algorithm has many drawbacks as the parameter identification points for systolic and diastolic pressure depend on many factors, for example pulse pressure, heart rate and arterial stiffness. These errors have now been demonstrated in clinical studies. Modern pattern recognition algorithms are being constructed but have not yet produced convincing results. As repeatedly stated, the development of a more robust and more widely applicable algorithm than the maximal amplitude approach should be allocated a high priority.

Algorithms↗
PubMed2000

Silent ischaemia and hypertension.

For many years now, silent ischaemia has been recognized as a distinct clinical entity, and its relevance in different patient groups has been established. However, a number of basic questions have not been answered. In explaining the pathophysiology of silent ischaemia, factors affecting both the demand and the supply side are now being recognized. With the exception of certain well-defined groups, it is not clear why some patients are mostly symptomatic, while other patients are predominantly asymptomatic. There appear to be many factors influencing the ischaemic pain threshold. Studies investigating the prevalence of silent ischaemia show a remarkably high prevalence of silent ischaemia in different patient groups. Patients with hypertension but without coronary artery disease form a specific and vulnerable high-risk population that is particularly prone to silent ischaemia. Since changes at the macrovascular level are not responsible, various factors negatively influencing either cardiac supply or demand have been investigated. A reduced coronary reserve is central in explaining the increased prevalence of silent ischaemia in hypertensives. Left ventricular hypertrophy renders meaningful detection of ST segment changes difficult, but a possible solution dealing with this problem is offered by applying more stringent criteria in terms of minimal ST depression in the definition of ischaemia. The treatment of silent ischaemia is largely the same as for angina pectoris, but whether therapy should be directed at elimination of all ischaemic episodes or only of symptomatic episodes depends on further prospective work addressing this question.

Humans↗
PubMed2000

Is greater tissue activity of creatine kinase the genetic factor increasing hypertension risk in black people of sub-Saharan African descent?

We postulate that the genetic factor increasing the propensity of black people of sub-Saharan African descent to develop high blood pressure is the relatively high activity of creatine kinase, predominantly in vascular and cardiac muscle tissue. Such greater activity of creatine kinase has been reported in skeletal muscle of black untrained subjects has been reported to be almost twice the activity found in white subjects. Creatine kinase, a key enzyme of cellular energy metabolism, increases the capacity of the cell to function under high demands. The enzyme regulates, buffers and transports, via phosphocreatine and creatine, energy produced by glycolysis and oxidative phosphorylation to sites of energy consumption such as myofibrils and membrane ion pumps. At these cellular locations, it is involved in the contraction process and active trans- membranous transport by readily providing the ATP needed for these processes. In addition, creatine kinase is increasingly reported to be involved in trophic responses. Furthermore, by using H+ and ADP to synthesize ATP, creatine kinase prevents acidification of the cell, providing relative protection against the effects of ischaemia. Greater creatine kinase activity in cardiovascular muscle and other tissues with high energy demands could increase cardiovascular contractile reserve, enhance trophic responses and increase renal tubular ability to retain salt. This could facilitate the development of arterial hypertension under chronic provocative circumstances, with higher mean blood pressures, more left ventricular hypertrophy and relatively fewer ischaemic events. Therefore, greater cellular activity of creatine kinase might explain the greater hypertension risk and the clinical characteristics of hypertensive disease observed in the black population.

Africa, Southern↗
PubMed2000

Coronary heart disease after prenatal exposure to the Dutch famine, 1944-45.

OBJECTIVE: To assess the effect of prenatal exposure to maternal malnutrition on coronary heart disease in people born around the time of the Dutch famine, 1944-45. DESIGN: Historical cohort study. SETTING: Community study. PATIENTS: Singletons born alive between November 1943 and February 1947 for whom detailed birth records were available. DESIGN: The prevalence of coronary heart disease was compared between those exposed to famine in late gestation (n = 120), in mid-gestation (n = 108), or in early gestation (n = 68), and those born in the year before the famine or those conceived in the year after the famine (non-exposed subjects, n = 440). MAIN OUTCOME MEASURES: Prevalence of coronary heart disease, defined as the presence of angina pectoris according to the Rose questionnaire, Q waves on the ECG, or a history of coronary revascularisation. RESULTS: The prevalence of coronary heart disease was higher in those exposed in early gestation than in non-exposed people (8.8% v 3.2%; odds ratio adjusted for sex 3.0, 95% confidence interval (CI) 1.1 to 8.1). The prevalence was not increased in those exposed in mid gestation (0.9%) or late gestation (2.5%). People with coronary heart disease tended to have lower birth weights (3215 g v 3352 g, p = 0.13), and smaller head circumferences at birth (32.2 cm v 32.8 cm, p = 0.05), but the effect of exposure to famine in early gestation was independent of birth weight (adjusted odds ratio 3.2, 95% CI 1.2 to 8.8). CONCLUSIONS: Although the numbers are very small, this is the first evidence suggesting that maternal malnutrition during early gestation contributes to the occurrence of coronary heart disease in the offspring.

Birth Weight↗
PubMed1999

Effects of treatment of obstructive sleep apnea on circadian hemodynamics.

INTRODUCTION: The role of obstructive sleep apnea syndrome (OSAS) in the etiology of daytime hypertension is still an issue of debate, which is fed by the high prevalence of the syndrome in hypertensive patients. In this study the anti-hypertensive effect of short-term treatment of obstructive sleep apnea with nasal continuous positive airway pressure (nCPAP) was assessed. PATIENTS AND METHODS: In eight patients with documented OSAS (mean apnea index 62 apneas/h), two 24-h continuous finger blood pressure registrations (Portapres) were performed. At baseline and after 3 weeks of treatment with nCPAP. Ten hypertensive control subjects were studied. Stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) were assessed by pulse contour analysis. RESULTS: Hemodynamics were highly reproducible in the controls. nCPAP therapy improved apnea-activity in all OSAS patients. This was associated with a reduction of nighttime systolic (SBP), mean arterial (MAP) and diastolic blood pressure (DBP). Treatment also reduced daytime MAP by -11 mm Hg (ranging from -27 to 1; P < 0.05), and DBP by -7 mm Hg (-24 to 3; P < 0.05). CO was significantly increased in daytime by 9% (-4 to 25; P < 0.05), whereas TPR was reduced by -15% (-34 to 3; P < 0.05). CONCLUSIONS: Treatment of OSAS caused a reduction in daytime MAP and DBP, associated with a reduction of vascular resistance. These findings are consistent with the hypothesis of a reduced sympathetic outflow at night after therapy of obstructive sleep apnea, carrying over to the day.

Adult↗
PubMed1999

Blood pressure in adults after prenatal exposure to famine.

BACKGROUND: Many studies have shown that low birth weight is associated with high blood pressure. The composition of the diet of pregnant women has also been found to affect blood pressure in their children. We assessed the effect of prenatal exposure to the Dutch famine of 1944-1945, during which the caloric intake from protein, fat and carbohydrate was proportionally reduced, on blood pressures in adults now aged about 50 years. METHODS AND RESULTS: We measured blood pressures at home and in the clinic among people born at term in one hospital in Amsterdam, The Netherlands, between November 1 1943 and February 28 1947, for whom we had detailed birth records. Blood pressures of people exposed to famine during late (n = 120), mid-(n = 109) or early gestation (n = 68) were compared with those of people born in the year before or conceived in the year after the famine (unexposed subjects, n = 442). No effect of prenatal exposure on systolic and diastolic blood pressure was observed. The mean systolic blood pressure taken in the clinic in those exposed in late gestation, and adjusted for sex and age, was 1.3 mmHg higher than in the unexposed group (95% confidence interval -1.9 to 4.4). The mean systolic blood pressure differed by -0.6 mmHg (95% confidence interval -3.9 to 2.7) for those exposed in mid-gestation and -1.7 mmHg (95% confidence interval -5.6 to 2.2) for those exposed in early gestation. People who were small at birth had higher blood pressures. A 1 kg increase in birth weight was associated with a decrease of 2.7 mmHg (95% confidence interval 0.3 to 5.1) in systolic blood pressure. Analyses of blood pressures measured at home gave similar results. CONCLUSION: High blood pressure was not linked to prenatal exposure to a balanced reduction of macronutrients in the maternal diet. However, it was linked to reduced fetal growth. We postulate that it might be the composition rather than the quantity of a pregnant woman's diet that affects her child's blood pressure in later life.

Adult↗