Biomedical subjects

H van Langen

Publications and source records attributed to H van Langen.

At least 19 recordsLinked to original sources

PubMed2000

Intima-media thickness of peripheral arteries in asymptomatic cigarette smokers.

BACKGROUND AND PURPOSE: Although it is known that smoking is associated with an increase in arterial wall thickness, most studies have been performed in heterogeneous groups of older age, already suffering from atherosclerotic diseases or having additional cardiovascular risk factors. The purpose of this study is to assess the effect on arterial wall thickness of the carotid and femoral artery in cigarette smokers. METHODS: In a cross-sectional study, intima-media thickness of the common and internal carotid artery, carotid bulb and common femoral artery was determined with the use of a B-mode ultrasound device, in 184 (44.3+/-9.0 years) cigarette smokers for whom smoking is the single cardiovascular risk factor. Comparisons were made with 56 non-smokers, matching in age and gender. RESULTS: The posterior walls of both carotid bulbs (right: P=0.0005; left: P=0.02) and of the internal carotid arteries (right: P=0.004; left: P=0.003) as well as the posterior wall of the right common carotid artery (P=0.02) and of the right common femoral artery (P<0.0001) were thicker in smokers. CONCLUSIONS: Cigarette smoking as the single cardiovascular risk factor causes wall thickening of the carotid and femoral arteries, which indicates that early atherosclerosis is already present in smokers entering middle age.

Adult↗

PubMed2000

The effect of cholesterol lowering on carotid and femoral artery wall stiffness and thickness in patients with familial hypercholesterolaemia.

BACKGROUND: Early in the process of atherosclerosis, changes in vessel wall stiffness and thickness may occur. The present study evaluates the effect of cholesterol reduction on artery wall stiffness and intima media thickness in patients with familial hypercholesterolaemia (FH). MATERIALS AND METHODS: Forty-five patients with familial hypercholesterolaemia (mean age 46+/-10 years) with untreated LDL cholesterol concentration > 9 mmol L(-1), were studied before and after one year of cholesterol lowering therapy with statins (simvastatin, atorvastatin 40-80 mg day(-1). The distensibility (DC in 10-3 kPa(-1) and compliance (CC in mm2. kPa(-1) of the common carotid artery (CCA) (right and left side) and common femoral artery (CFA) (right side) were determined by a wall track system (Pie Medical). The intima media thickness (IMT) (both right and left) of the CCA, bulb (BUL), internal carotid artery (ICA) and CFA were measured in mm by high-resolution ultrasound (Biosound). RESULTS: The mean concentration of total cholesterol (TC), LDL-cholesterol (LDL-C) and triglycerides (TG) were reduced significantly by 43%, 51% and 25%, respectively, whereas HDL-cholesterol (HDL-C) increased by 13% (P<0.001). In the CFA, the DC and CC increased significantly (DC from 7.9+/-3.0 to 9.1+/-3.7 in 10(-3) kPa(-1); CC 0.5+/-0.2-0.6+/-0.3 in mm2. kPa(-1), whereas the DC and CC did not change in the CCA. In contrast, the IMT of the CCA decreased significantly in both men and women whereas an IMT decrease was also seen in the BUL and ICA in premenopausal women. A LDL-cholesterol reduction of 44.8% and 45.4% was necessary to induce significant decreases in IMT and increases in DC and CC. CONCLUSIONS: One year of cholesterol lowering therapy in FH decreases the wall stiffness in the CFA and the arterial wall thickness in the CCA.

Adult↗

PubMed1999

The postthrombotic syndrome in relation to venous hemodynamics, as measured by means of duplex scanning and strain-gauge plethysmography.

PURPOSE: Venous hemodynamics were evaluated in relation to the postthrombotic syndrome (PTS) 7 to 13 years after deep venous thrombosis (DVT). METHODS: The presence of flow, reflux, and compressibility of 1394 vein segments in 82 patients was assessed by means of duplex scanning. The venous outflow resistance was measured by means of strain-gauge plethysmography. The venous hemodynamics were related to the clinical severity of the PTS, characterized by the CEAP (clinical, etiologic, anatomic, pathophysiologic) classification. RESULTS: In patients with severe clinical symptoms of PTS, the prevalence of reflux was significantly higher. There was no relationship between the severity of the PTS and the noncompressibility or the combination of reflux and noncompressibility or an increased venous resistance. By means of multiple regression analysis with the variables of age, gender, reflux, and venous resistance, age and reflux were shown to be the main contributors to the severity of PTS. Significantly more patients (64%) with severe signs of PTS had a combination of deep and superficial reflux. In each of the traceable vein segments, the mean of the CEAP classification was calculated for the vein segments with and without reflux. In the proximal superficial femoral vein (P <.001), distal superficial femoral vein (P <.05), and popliteal vein (P <.05), a significantly higher mean CEAP classification was found in the veins with reflux, whereas in the distal, long, and short saphenous veins, no such relationship was found. CONCLUSION: Most patients with severe PTS had a combination of deep and superficial reflux. Reflux in the deep proximal veins contributes significantly to the PTS.

Adult↗

PubMed1999

Venous duplex scanning of the leg: range, variability and reproducibility.

Despite the many studies on venous haemodynamics using duplex, only a few evaluated the normal values, variability and reproducibility. Therefore, the range and variability of venous diameter, compressibility, flow and reflux were measured. To obtain normal values, 42 healthy individuals (42 limbs, 714 vein segments) with no history of venous disease were scanned by duplex. To determine the reproducibility the intra-observer variability was measured in 11 healthy individuals (187 vein segments) and the inter-observer variability in 15 healthy individuals (255 vein segments) and 13 patients (169 vein segments) previously diagnosed with deep venous thrombosis. Of the 714 normal vein segments, 708 (99%) were traceable, including the crural veins. Of the traceable vein segments, 675 (95%) were compressible and in 696 (98%) flow was present. Of the 42 common femoral vein segments, in 25 (60%) the reflux duration exceeded 1.0 s, but in the other proximal vein segments the reflux duration was less than 1.0 s (95% confidence interval 3.0-10.0). With the exception of the distal long saphenous vein, in the distal vein segments the reflux duration was less than 0.5 s (95% confidence interval 3.5-8.2). The coefficient of variation of the diameter measurements ranged from 14 to 50% and that of the reflux measurements from 28 to 60%. The kappa-coefficient of the inter-observer variability in the classification of compressibility measurements in the patients was 0. 77 and that of the reflux measurements was 0.86. This study shows that almost all veins were compressible in healthy individuals, except the distal femoral veins. In healthy individuals the duration of reflux of the proximal veins was less than 1.0 s and in the distal veins it was less than 0.5 s. The inter-observer variability of the reflux and compressibility measurements in the patients was good.

Adult↗

PubMed1998

Changes in venous hemodynamics after renal transplantation.

To explain an occasionally observed transient swelling of the ipsilateral leg in renal transplant recipients in the absence of deep vein thrombosis, we took serial measurements of venous outflow resistance and duplex examinations of both legs. Fourteen recipients of a living related donor kidney graft were submitted to strain gauge plethysmography and duplex examination before transplantation and 1 and 6 weeks thereafter. Venous outflow resistance and venous flow were measured and the veins were assessed for thrombosis. Strain gauge plethysmography showed a significant increase in venous outflow resistance in the leg on the side of the renal transplant 1 week after transplantation [0.28 +/- 0.13 vs 0.40 +/- 0.15 mmHg.s (ml/100 ml)-1; P < 0.05]. Six weeks later, the venous outflow resistance had returned to preoperative values [0.30 +/- 0.11 mmHg.s (ml/100 ml)-1; P = NS]. On the contralateral side, no significant differences were found. Duplex examinations showed no signs of thrombosis. Venous flow measurements in the common femoral vein showed no significant differences. We conclude that the additional blood supply to the iliac veins results in an increase in venous outflow resistance in the ipsilateral leg, which can explain the observed swelling of this leg and may have implications for the preferred method of diagnosis of venous thrombosis after renal transplantation.

Adult↗

PubMed1998

Duplex ultrasound in the hemodynamic evaluation of the late sequelae of deep venous thrombosis.

PURPOSE: The use of duplex ultrasound scanning to evaluate the hemodynamic outcome of deep venous thrombosis 7 to 13 years after the original diagnosis. METHODS: Duplex ultrasound was used to re-examine 1212 segments of vein from 72 patients (49 men, 23 women) with deep venous thrombosis previously diagnosed by means of phlebography to detect reflux and obstruction and evaluate flow; 611 segments were initially thrombosed and 601 segments were open. To define reflux, reversed flow in 31 healthy persons was measured. RESULTS: In a review of all veins of the 72 patients, 8 patients (11%) had completely normal duplex results in all veins, 33 (46%) had reflux, 6 (8%) had at least one noncompressible vein segment, and 25 (35%) had a combination of both. In the proximal vein segments without initial thrombosis a higher percentage was normal (73%) than in segments with initial thrombosis (46%). There was a significantly higher frequency of reflux (46%, p = 0.05) and noncompressibility (12%, p < 0.01) in initially thrombosed proximal vein segments than in vein segments without initial thrombosis (reflux 25%, noncompressibility 3%). Distal to the knee 125 (17%) of 720 vein segments were not traceable. Significantly more initially thrombosed vein segments were not traceable (p < 0.01). In distal vein segments there was no significant difference in reflux (7% versus 5%) and noncompressibility (10% versus 5%) between vein segments with and without initial thrombosis. Flow was present in 99% of the 611 previously thrombosed proximal and distal segments. CONCLUSIONS: Most patients with deep venous thrombosis still had venous abnormalities 7 to 13 years after the initial diagnosis. The most common abnormality was reflux. Significantly more abnormalities were found in initially thrombosed segments. The abnormalities were found in the proximal vein segments and in the distal vein segments, although less frequently in the latter.

Adult↗

PubMed1998

Dynamic vessel wall properties and their reproducibility in subjects with increased cardiovascular risk.

OBJECTIVE: To determine reproducibility figures of dynamic arterial wall properties such as cross-sectional compliance (CC) and distensibility (DC) in subjects with increased cardiovascular risk, in comparison with healthy adults. METHODS: A total of 34 persons were divided into three groups with varying cardiovascular risk factors. Diameters (D) and diameter changes (deltaD) during the heart cycle of both common carotid (CCA) and right common femoral (CFA) arteries were measured by a vessel wall movement detector system. Blood pressures (BP) were recorded non-invasively by a semi-automated oscillometric device. CC (=piD(deltaD/2deltaP) in unit mm2/kPa) and DC (=2deltaD/D)/deltaP in unit 10(-3)/kPa) were calculated from the above-mentioned parameters. Measurements were performed twice during one visit and twice again with a time interval of at least 3 days to determine intra-observer intra- and intersession variability. RESULTS: Reproducibility figures of CC and DC of the CCA varied between 8 and 12%, and between 13 and 22% for the CFA. Intra-observer intra- and intersession variability were similar in the three groups. CONCLUSIONS: In our studies the reproducibility of dynamic vascular wall properties determined by ultrasound was good. Despite differences in the absolute values for CC and DC in groups with increased cardiovascular risk, mean reproducibility figures remained at a similar level (8-12%) as in healthy volunteers.

Adult↗

PubMed1998

A prospective randomized comparison between fixed rate response programming and automatic rate response optimization in activity-triggered DDDR pacemakers. Thera Pacemaker Study Group.

Activity rate response programming depends on the physician's experience and on the limited knowledge of patient's daily activities. The present investigation compares a new continuous automatic adjustment of the activity rate response called rate response optimization (OPT) with fixed activity rate response programming (FIXED). At hospital discharge 37 patients with Thera DR pacemakers (Medtronic) were randomized either to FIXED (n = 20; 65 +/- 12 years, male n = 12) or to OPT (n = 17; 65 +/- 12 years, male n = 13). After 1 month's follow-up occurrence of complaints related to rate-responsive pacing and the percentage of pacing were assessed. Other activity sensor parameters were programmed according to clinical judgement and similarly distributed in the two groups. Activity rate response was 7.1 +/- 1.4 (FIXED) and 7.2 +/- 1.7 (OPT), activity threshold was medium in 9 (FIXED) and 8 (OPT), and medium/low in 11 (FIXED) and 9 (OPT) patients, respectively. No patient with FIXED had any complaints with respect to activity-triggered rate response. One patient with OPT reported palpitations due to rapid changes in the pacing rate leading to reprogramming of the pacemaker. Atrium and ventricle were paced in 56 +/- 31% (FIXED) and in 58 +/- 35% (OPT; not significant) and the atrium only in 4 +/- 10% (FIXED) and 0% (OPT; not significant), respectively. In the 17 patients programmed to OPT the pacemaker increased activity rate response in 5 and decreased activity rate response in 3 patients. In conclusion, as only 1 (3%) patient had complaints related to the activity rate response and fixed rate response programming according to clinical judgement already resulting in symptom-free DDDR pacing, no differences could be detected between the fixed rate response programming and rate response optimization.

Aged↗

PubMed1998

Carotid and femoral artery wall thickness and stiffness in patients at risk for cardiovascular disease, with special emphasis on hyperhomocysteinemia.

Recent developments in ultrasound technology enable the noninvasive measurement of structural and functional vessel wall changes. Until now, the effect of homocysteine on the arterial wall has remained unclear: reports on intima-media thickness (IMT) yield conflicting results, whereas data on vessel wall stiffness are lacking. Because several cardiovascular risk factors result in an increased IMT or stiffness, different groups at risk for atherosclerotic disease, with special emphasis on hyperhomocysteinemia, were studied. Nineteen patients homozygous and 14 subjects heterozygous for cystathionine beta-synthase (CBS) deficiency, 21 patients with familial hypercholesterolemia (FH), 15 patients with essential hypertension, 20 smokers, and 28 control subjects were studied. The IMT values (both right and left) of the common carotid artery (CCA), bulb (BUL), internal carotid artery (ICA), and common femoral artery (CFA) were measured in millimeters by high-resolution ultrasound (Biosound). The distensibility (DC, in 10(-3). kPa-1) and compliance (CC in mm2. kPa-1) coefficients of the CCA (right and left) and CFA (right) were determined by a wall track system (Pie Medical). The mean IMT of the posterior wall in the CCA was 0.70+/-0.09 mm in healthy controls. For patients with vascular disease, FH, and hypertension and in smokers, the mean CCA IMT was larger, whereas no major differences in IMT were observed in patients either homozygous or heterozygous for CBS deficiency. The DC and CC in the right CCA were 23.5+/-6.9 (10(-3). kPa-1) and 0.9+/-0.3 (mm2. kPa-1) in healthy subjects, slightly lower in patients homozygous for CBS deficiency, and clearly lower in patients with vascular disease, FH, and hypertension. No positive correlation was found between plasma homocysteine level and either IMT, CC, or DC. Because smoking was a confounder in each risk group, a stepwise regression analysis was carried out to assess the contribution of each risk factor on IMT and arterial wall stiffness. Age explained most of the variation in IMT of the CCA (coefficient of determination R2 of 0.34), whereas R2 values for serum low density lipoprotein cholesterol, smoking (pack-years), and systolic blood pressure were 0.08, 0.07, and 0.06, respectively. Homocysteine did not contribute to variation in IMT in both the CCA and CFA. Age and smoking contributed to the variation in IMT in the CFA. The variation in DC and CC in the right CCA and right CFA could in part be explained by age, low density lipoprotein cholesterol, and blood pressure. Plasma homocysteine concentration explained only a small proportion of the variation in DC in the CCA (R2=0.02) and in CC in the CFA (R2=0.04). In this study, no relationship was found between homocysteine level and the thickness of the arterial wall, with only a marginal influence on stiffness.

Adult↗

PubMed1997

[Frequency of atrial pacing in patients with intermittent atrial fibrillation and 2nd or 3rd degree atrioventricular block. Thera DR Pacemaker Study Group].

UNLABELLED: Patients with 2nd or 3rd degree AV-block and paroxysmal atrial fibrillation could be suitable for VDDR pacemakers, if they are not or rarely paced in the atrium. We studied in 23 of these patients 1 month after DDDR pacemaker implantation, how often they were paced in the atrium with usual pacemaker programmings; patients with < 10% atrial pacing were compared with patients with > or = 10% atrial pacing. In case automatic mode switch was programmed, the number of mode switch episodes was assessed as a marker for the frequency of atrial tachyarrhythmias. Atrial pacing < 10% of the time occurred in seven, pacing from 10 to 19% in six, from 20 to 29% in two, and > or = 30% of the time in eight patients. Five of the seven patients with < 10% atrial pacing were paced in the DDD mode, but only four of 16 patients with > or = 10%. Usual clinical findings were unable to predict patients with rare atrial pacing. Patients with < 10% as well as with > or = 10% atrial pacing had < 10 mode switch episodes in 67% each. CONCLUSIONS: During short-term follow-up after DDDR pacemaker implantation 30% of the patients with paroxysmal atrial fibrillation and second or third degree AV-block, with present usual pacemaker programmings, rarely had atrial pacing, that means < 10% of the time. These patients would be probably suitable for VDDR pacemakers. Rare atrial pacing had no influence on the occurrence of automatic mode switch episodes.

Adult↗

PubMed1997

Decreased ankle/brachial indices in relation to morbidity and mortality in patients with peripheral arterial disease.

To determine the relationship between ankle/brachial indices (ABIs) and morbidity and mortality in patients with peripheral arterial disease (PAD), a historical cohort study was performed. A total of 154 patients who had undergone noninvasive arterial assessment of the lower extremities in 1989 and 1990 were selected for this purpose. Selection criteria were age > 40 years at the time of investigation, a resting ABI < 0.90 and the availability of an ABI after exercise or arterial occlusion. Mortality and vascular events were recorded after an average follow-up period of 6 years. A vascular event was defined as an intervention because of PAD, the occurrence of a nonfatal myocardial infarction or stroke, a transient ischaemic attack or a coronary artery bypass graft (CABG) or percutaneous transluminal coronary angioplasty (PTCA) procedure. During the period studied, 44 patients died and 111 patients suffered a vascular event. The relative risk for mortality was 3.1 per 0.50 decrease of the ABI at rest (95% confidence interval (CI) 1.1-8.7, p = 0.03) and 2.4 per 0.50 decrease of the ABI after exercise or arterial occlusion (95% CI 0.9-6.4, p = 0.08). The relative risk for mortality or the occurrence of a vascular event was 3.3 per 0.50 decrease of the resting ABI (95% CI 1.7-6.3, p < 0.001) and 2.5 per 0.50 decrease of the ABI after exercise or occlusion (95% CI 1.5-4.4, p < 0.001). After standardization, the prognostic power of the two types of ABIs was equivalent. The cumulative survival after 5 years was 63% for patients with resting ABIs < 0.50, 71% for patients with ABIs 0.50-0.69 and 91% for those with ABIs of 0.70-0.89. There were obvious differences between the mean initial ABIs of patients who suffered a vascular event and/or died and those of survivors, who did not suffer an event. A relatively simple measurement like the determination of the resting ABI can give valuable information about the prognosis for vascular related morbidity and mortality. This can be of help in the approach of patients with PAD and assist in therapeutical decision making. Determination of the ABI after exercise or occlusion has no additional value for this purpose.

Adult↗

PubMed1997

D-dimer determination to assess regression of deep venous thrombosis.

A number of studies evaluating deep venous thrombosis (DVT) have demonstrated that plasma levels of thrombotic and fibrinolytic parameters change during treatment, but the relationship between thrombus regression and evolution of these markers remains unknown. The objective of the present study was to correlate levels of D-Dimer (DD) with thrombus regression as assessed by duplex scanning. From 44 patients treated for acute DVT, DD were determined at diagnosis and at the end of initial heparin therapy of at least 5 days. Thrombus regression was measured by repeated duplex scanning at diagnosis and after 1 and 3 months. DD significantly decreased during heparin treatment as compared with values at presentation. DD levels were significantly higher in the group of patients without normalization of the DVT after 3 months (p = 0.003). A ninefold excess tendency was seen for DD levels > 1200 ng/ml at the end of initial treatment to be associated with poor resolution of the DVT [odds ratio 9.0, 0.95 confidence interval (CI) 2.3-35.4]. When the patients with an established malignancy were excluded, the differences were even more significant (p = 0.0004 for DD levels after initial treatment and an odds ratio of 17.5, 0.95 CI 3.3-92.5). These results suggest that increased DD levels after the initial phase of treatment are related to poor resolution of DVT after 3 months. These findings contribute to further insight into the process of thrombus regression. Furthermore high DD levels might help to identify the patients with a poor prognosis and could be useful to judge the efficacy of anticoagulant treatment.

Adult↗

PubMed1996

[Low stimulation impedance in pacemaker patients with cardiac diseases. The Thera Pacemaker Study Group].

BACKGROUND AND AIM OF THE STUDY: As increasing impedance of the pacing impulse decreases pacing current, high pacing impedance lowers pacing current and subsequently prolongs pacemaker longevity. The present assumption of a standard 500 ohms impedance disregards interindividual differences. In the present study, the interindividual range of pacing impedance was assessed at implantation. Additionally clinical parameters of patients with low pacing impedance were compared to those of patients with high values. PATIENTS AND METHODS: The same lead and the same pacemaker (CapSure VDD; Thera VDD; Medtronic) were implanted in 126 patients (79 men, 47 women, mean age 65 +/- 16 years). Patients with an impedance below or similar to the median were compared to patients with an impedance above the median in respect to clinical (age, gender, arterial hypertension, cardiac diseases such as coronary heart disease, valvular heart disease, cardiomyopathy) and electrical parameters (pacing threshold at 0.5 ms pulse duration, R-wave amplitude). RESULTS: Mean impedance was 687 +/- 121 ohms with a range from 333 to 1040 ohms and a median of 670 ohms. 64 patients had an impedance < or = 670 ohms and 62 patients > 670 ohms. Mean age, gender and the occurrence of arterial hypertension were similar in the two groups. Cardiac diseases occurred significantly (P < 0.01) more often in patients with lower (n = 23) than with higher impedance (n = 9). Intraoperative pacing thresholds and R-wave amplitudes were not different between the two groups. CONCLUSIONS: The range of pacing impedance was 707 ohms for the studied lead. Under consideration of permanent pacing with 2.5 V pulse amplitude and 0.5 ms pulse duration this would vary expected longevity of the implanted pacemaker from 7.8 to 9.3 years. Patients with lower impedance more often had cardiac diseases than patients with higher impedance.

Adult↗

PubMed1996

[Intermittent atrial fibrillation/flutter: contraindication for implantation of a dual chamber pacemaker?].

UNLABELLED: The programming of dualchamber pacemakers to DDD(R) mode is not recommended in patients with paroxysmal atrial fibrillation/flutter, because the pacemaker detects atrial fibrillation/flutter and paces the ventricle up to the pacemaker's upper tracking rate. Some newer pacemakers have the feature to switch automatically from DDD(R) to DDIR mode at the onset of atrial tachyarrhythmias. The aim of the study was to assess how many patients who received such a new DDDR pacemaker with automatic mode switch can be programmed to DDD(R) mode during follow-up. The dual-chamber pacemaker Thera DR (Medtronic) was implanted for clinical evaluation in 142 patients (65 +/- 16 years, male n = 86; female n = 56). Paroxysmal atrial fibrillation/flutter was present in 54 patients, with an additional 2nd or 3rd degree AV-block in 13 and no high-degree AV block in 22 cases; an AV node ablation was performed in 19 patients. Pacemakers were programmed to DDD(R) mode at discharge in 52 of 53, at month 1 in 44 of 46, and at month 3 in 28 of 30 cases. In respect to the programming to DDD(R) mode there were no statistically significant differences to patients without paroxysmal atrial fibrillation/flutter. CONCLUSION: Paroxysmal atrial fibrillation/flutter was present in 38% of the studied patients. During follow up more than 90% of the patients were paced in the DDD(R) mode.

Aged↗

PubMed1996

[Comparison of active and passive fixation of steroid emitting atrial electrodes].

UNLABELLED: Steroid-eluting screw-in leads (CapSure Fix 4068, Medtronic; n = 14) were compared to the same lead as a J-shaped tined electrode (CapSure SP 4524, Medtronic; n = 27, implanted in the atrium in patients receiving dual-chamber pacemakers. Follow-up were at discharge and after 1 month. Implantation (screw-in lead: 84 +/- 18 min; tined lead: 81 +/-29 min) and fluoroscopy times (screw-in lead: 7.3 +/- 4.9 min; tined lead 9.2 +/- 7.0 min) were similar in the two groups. At implant, P-wave amplitudes were similar with 4.8 +/- 1.6 mV (screw-in lead) and 4.0 +/- 2.6 mV (tinted lead), respectively. Compared to tined leads, the screw-in leads had higher pacing thresholds at 0.5 ms pulse duration (screw-in lead: 0.74 +/- 0.32 V; tined lead: 0.55 +/- 0.15 V; p = 0.02) as well as higher impedance (screw-in lead: 566 +/- 93 ohms; tined lead: 470 +/- 99 ohms; p = 0.01). Pulse duration thresholds at 2.5 V pulse amplitude were neither different at discharge (screw-in lead: 0.07 +/- 0.04 ms; tined lead: 0.06 +/- 0.05 ms) nor after 1 month (screw-in lead: 0.09 +/- 0.04 ms; tined lead: 0.06 +/- 0.06 ms). P-wave amplitudes > or = mV were observed at discharge in 14/14 (screw-in lead) 21/27 patients (tined lead), respectively, and after 1 month in 13/14 (screw-in lead) and 22/27 (tined lead) patients, respectively. Impedance of the screw-in lead was significantly higher with 693 +/- 84 ohms at discharge and 691 +/- 79 ohms after 1 month compared to the tined lead with 520 +/- 81 and 574 +/- 62 ohms (p = 0.001). No lead dislodgment was reported during follow-up. CONCLUSIONS: For the studied steroid-eluting leads active and passive fixation had neither at implantation nor during 1-month follow up any influence on P-wave amplitude. At similar pulse duration thresholds, impedance of the screw-in lead was significantly higher than for the tined lead. Higher impedance additionally reduces pacing current, if similar pacing impulses are delivered.

Administration, Topical↗

PubMed1994

Ultrasound determination of the effect of progestogens on the endometrium in postmenopausal women receiving hormone replacement therapy.

Progestogen challenge tests were performed in 81 postmenopausal women receiving hormone replacement therapy (HRT) with progestogen addition as required. The number of tests carried out totalled 159. The effect of progestogen use on endometrial thickness was determined by vaginosonography. The endometrial shedding caused by progestogen was correlated with the withdrawal bleeding pattern. As expected, in the majority of cases (145 out of 159), progestogen brought about endometrial shedding. In most but not all cases, shedding was attended by withdrawal bleeding. The intensity and the duration of withdrawal bleeding were positively correlated with endometrial shedding. No correlation was found between endometrial shedding and the onset of withdrawal bleeding.

Adult↗

PubMed1993

Dynamic response of a neonatal catheter-manometer system in situ.

OBJECTIVE: The purpose of this study was to develop, validate, and apply a flush-pulse method to determine the dynamic response of a neonatal catheter-manometer system (CMS) in situ. METHODS: In the flush-pulse method, the opened fast-flush valve of the CMS is closed; as a result, the fluid column in the CMS is impacted. This procedure can be done without affecting the net flow of infusion fluid. We validated the method in laboratory conditions by comparing 14 paired results obtained with this method to the results obtained using a generally accepted step-response method. The measurable values are the resonance frequency (fr) and the damping coefficient (delta). The analysis of the flush-pulse method in situ is complicated by the patient's blood pressure wave. A remedy for this problem that is based on the first derivative of the pressure signal has been developed. The flush-pulse method is applied 14 times in situ. RESULTS: In laboratory settings, the fr ranged from 12.5 to 64.0 Hz and delta ranged from 0.14 to 0.32. The correlation coefficient was 0.99 for fr and 0.91 for delta. We found four overdamped systems in situ (delta > 1). In other systems fr values between 8.5 and 41.0 Hz and delta values between 0.16 and 0.72 were observed. The dynamic response in situ appeared to deteriorate with time due to routine intensive care procedures. CONCLUSIONS: The flush-pulse method proved to be a valid test for determining the dynamic response. The results obtained in situ emphasize the need for a regular evaluation of the dynamic response of the neonatal CMS in order to assess the shape of the pressure wave.

Blood Pressure↗

PubMed1992

Monitoring of oestrogen replacement therapy by vaginosonography of the endometrium.

To prevent hyperplasia and carcinoma of the endometrium during oestrogen replacement therapy (ORT), the addition of progestogens once a month is considered mandatory. However, there is no sound scientific basis for this assumption. As the addition of progestogens has several disadvantages, it is important to minimize the frequency of progestogen addition. Vaginosonography is a rather new technique which has not yet been used for monitoring ORT. In this study the increase in endometrial thickness, as measured by vaginosonography, was taken as an indicator of stimulation of the endometrium by oestrogens. Oestrogen treatment was started in post-menopausal women with little endometrium (thickness less than 3 mm). As long as there was virtually no increase during oestrogen treatment, no progestogen was added, but where considerable growth occurred (greater than 3 mm) progestogen was administered. By means of vaginosonography the growth of the endometrium can be monitored precisely on an individual basis. It is thus possible to distinguish women with a slow growing endometrium from those with an endometrium that grows fast. In this way it will perhaps become possible to minimize progestogen addition during ERT by tailoring dosage to individual requirements.

Endometrial Neoplasms↗