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Wouter Wieling

Publications and source records attributed to Wouter Wieling.

14 recordsLinked to original sources
PubMed2004

The role of carotid chemoreceptors in the sympathetic activation by adenosine in humans.

The direct vasodilatory and negative chronotropic effects of adenosine in humans are counterbalanced by a reflex increase in sympathetic nerve traffic. A suggested mechanism for this reflex includes peripheral chemoreceptor activation. We, therefore, assessed the contribution of carotid chemoreceptors to sympatho-excitation by adenosine. Muscle sympathetic nerve activity was recorded during adenosine infusion (140 microg.kg(-1).min(-1) for 5 min) in five patients lacking carotid chemoreceptors after bilateral carotid body tumour resection (one male and four female, mean age 51 +/- 11 years) and in six healthy controls (two male and four female, mean age 50 +/- 7 years). Sympathetic responses to sodium nitroprusside injections were assessed to measure baroreceptor-mediated sympathetic activation. In response to adenosine, controls showed no change in blood pressure, an increase in heart rate (+48.2 +/- 13.2%; P<0.003) and an increase in sympathetic nerve activity (+195 +/- 103%; P<0.022). In contrast, patients showed a decrease in blood pressure (-14.6 +/- 4.9/-17.6 +/- 6.0%; P<0.05), an increase in heart rate (+25.3 +/- 8.4%; P<0.032) and no significant change in sympathetic activity. Adenosine-induced hypotension in individual patients elicited less sympathetic activation than equihypotensive sodium nitroprusside injections. In humans lacking carotid chemoreceptors, adenosine infusion elicits hypotension due to the absence of significant sympatho-excitation. Chemoreceptor activation is essential for counterbalancing the direct vasodilation by adenosine. In addition, blunting of the baroreflex sympathetic response to adenosine-induced hypotension may indicate a direct sympatho-inhibitory effect of adenosine.

Adenosine↗
PubMed2003

Baroreflex control of muscle sympathetic nerve activity after carotid body tumor resection.

Bilateral carotid body tumor resection causes a permanent attenuation of vagal baroreflex sensitivity. We retrospectively examined the effects of bilateral carotid body tumor resection on the baroreflex control of sympathetic nerve traffic. Muscle sympathetic nerve activity was recorded in 5 patients after bilateral carotid body tumor resection (1 man and 4 women, 51+/-11 years) and 6 healthy control subjects (2 men and 4 women, 50+/-7 years). Baroreflex sensitivity was calculated from changes in R-R interval and muscle sympathetic nerve activity in response to bolus injections of phenylephrine and nitroprusside. In addition, sympathetic responses to the Valsalva maneuver and cold pressor test were measured. The integrated neurogram of patients and control subjects contained a similar pattern of pulse synchronous burst of nerve activity. Baroreflex control of both heart rate and sympathetic nerve activity were attenuated in patients as compared with control subjects [heart rate baroreflex sensitivity: 3.68+/-0.93 versus 11.61+/-4.72 ms/mm Hg (phenylephrine, P=0.011) and 2.53+/-1.36 versus 5.82+/-1.94 ms/mm Hg (nitroprusside, P=0.05); sympathetic baroreflex sensitivity: 3.70+/-2.90 versus 7.53+/-4.12 activity/100 beats/mm Hg (phenylephrine, P=0.10) and 3.93+/-4.43 versus 15.27+/-10.03 activity/100 beats/mm Hg (nitroprusside, P=0.028)]. The Valsalva maneuver elicited normal reflex changes in muscle sympathetic nerve activity, whereas heart rate responses were blunted in the patients with bilateral carotid body tumor resection. Maximal sympathetic responses to the cold pressor test did not differ between the two groups. Denervation of carotid sinus baroreceptors as the result of bilateral carotid body tumor resection produces chronic impairment of baroreflex control of both heart rate and sympathetic nerve activity. During the Valsalva maneuver, loss of carotid baroreflex control of heart rate is less well compensated for by the extra carotid baroreceptors than the control of muscle sympathetic nerve activity.

Adult↗
PubMed2003

Baroreflex and chemoreflex function after bilateral carotid body tumor resection.

OBJECTIVE: To investigate whether bilateral carotid body tumor resection invariably and chronically affects arterial baroreflex or peripheral chemoreflex function. METHODS: We studied eight consecutive patients (two men and six women; ages 48.1 +/- 11.8 years), a median time of 3.4 years (range 1.3-20.6 years) after bilateral carotid body tumor resection, and 12 healthy control individuals (eight men and four women; ages 53.7 +/- 10.1 years). Baroreflex sensitivity (phenylephrine), blood pressure and its variability (24 h Spacelabs and 5 h Portapres recordings), responses to standard cardiovascular reflex tests and the ventilatory responses to normocapnic and hypercapnic hypoxia were assessed. RESULTS: Baroreflex sensitivity was lower in patients (6.4 +/- 7.2 ms/mmHg) than in controls (14.7 +/- 6.6 ms/mmHg; P +/- 0.011). Mean office blood pressure and heart rate were normal in patients (123.3 +/- 11.9/79.0 +/- 7.3 mmHg and 67.5 +/- 9.4 beats/min, respectively) and controls (117.8 +/- 10.6/74.0 +/- 6.8 mmHg and 61.1 +/- 9.2 beats/min, respectively). Blood pressure variability was increased during ambulatory measurements. Three patients exhibited orthostatic hypotension. The Valsalva ratio, an index of baroreflex-mediated cardiovagal innervation, was lower in patients (1.4 +/- 0.2) than in controls (1.8 +/- 0.5; P +/- 0.008). The normocapnic ventilatory response to hypoxia was absent in all patients, whereas a small residual response to hypoxia was observed under hypercapnic conditions in two patients. CONCLUSIONS: Bilateral carotid body tumor resection results in heterogeneous expression of arterial baroreflex dysfunction, whereas the normocapnic hypoxic drive is invariably abolished as a result of peripheral chemoreflex failure.

Adult↗
PubMed2003

Syncope, cerebral perfusion, and oxygenation.

During standing, both the position of the cerebral circulation and the reductions in mean arterial pressure (MAP) and cardiac output challenge cerebral autoregulatory (CA) mechanisms. Syncope is most often associated with the upright position and can be provoked by any condition that jeopardizes cerebral blood flow (CBF) and regional cerebral tissue oxygenation (cO(2)Hb). Reflex (vasovagal) responses, cardiac arrhythmias, and autonomic failure are common causes. An important defense against a critical reduction in the central blood volume is that of muscle activity ("the muscle pump"), and if it is not applied even normal humans faint. Continuous tracking of CBF by transcranial Doppler-determined cerebral blood velocity (V(mean)) and near-infrared spectroscopy-determined cO(2)Hb contribute to understanding the cerebrovascular adjustments to postural stress; e.g., MAP does not necessarily reflect the cerebrovascular phenomena associated with (pre)syncope. CA may be interpreted as a frequency-dependent phenomenon with attenuated transfer of oscillations in MAP to V(mean) at low frequencies. The clinical implication is that CA does not respond to rapid changes in MAP; e.g., there is a transient fall in V(mean) on standing up and therefore a feeling of lightheadedness that even healthy humans sometimes experience. In subjects with recurrent vasovagal syncope, dynamic CA seems not different from that of healthy controls even during the last minutes before the syncope. Redistribution of cardiac output may affect cerebral perfusion by increased cerebral vascular resistance, supporting the view that cerebral perfusion depends on arterial inflow pressure provided that there is a sufficient cardiac output.

Cerebrovascular Circulation↗
PubMed2003

Prevalence and clinical outcomes of patients with multiple potential causes of syncope.

OBJECTIVE: To determine the prevalence, predictors, and prognosis of patients with multiple potential causes of syncope. PATIENTS AND METHODS: This is a retrospective cohort study with prospective follow-up of consecutive patients with syncope of uncertain cause who were referred to the electrophysiology service for syncope evaluation from January 1, 1996, through December 31, 1998. The main outcome measures were prevalence of multiple potential causes of syncope, survival of patients with multiple potential causes of syncope compared with survival of patients with a single cause, and clinical predictors of multiple potential causes of syncope. RESULTS: A total of 987 patients were studied (mean +/- SD age, 58.0 +/- 21.4 years; male, 550 [55.7%]). Multiple potential causes were present in 182 patients (18.4%). Patients with multiple potential causes of syncope had a lower survival rate at 4 years, 73.1% (95% confidence interval, 64.6%-82.8%), vs those with a single cause, 89.3% (95% confidence interval, 86.4%-92.2%) (P < .001). Multivariate predictors of multiple potential causes were older age, atrial fibrillation, use of cardiac medications, and New York Heart Association classification II, III, and IV. CONCLUSION: Of the patients evaluated for syncope, 18.4% had multiple potential causes. The presence of multiple potential causes was an independent predictor of increased mortality among patients with syncope.

Age Factors↗
PubMed2002

Management of vasovagal syncope: controlling or aborting faints by leg crossing and muscle tensing.

BACKGROUND: Posture-related vasovagal syncope is by far the most frequent cause of transient loss of consciousness, and present pharmacological and cardiac pacing treatment remains unsatisfactory. A simple maneuver to prevent or diminish vasovagal reactions would be beneficial. METHODS AND RESULTS: Twenty-one patients with recurrent syncope (age 17 to 74 years, 11 males) who were referred for routine tilt-table testing and had a positive test were included. They were instructed to perform leg crossing and muscle tensing for at least 30 seconds at the onset of a tilt table-provoked impending faint. Continuously measured blood pressure and heart rate at nadir and during the maneuver were compared. Ten months after the test, a telephone follow-up was performed. The physical counter-maneuver, performed in 20 of 21 subjects, increased blood pressure and heart rate. Systolic blood pressure rose from 65+/-13 to 106+/-16 mm Hg (mean+/-SD, P<0.001), and diastolic blood pressure rose from 43+/-9 to 65+/-10 mm Hg (P<0.001). During the maneuver, prodromal symptoms disappeared in all patients, and none lost consciousness. After terminating the maneuver, symptoms did not return in 5 subjects during the test. At follow-up, 13 of 20 patients reported that they applied the maneuver in daily life and benefited from it. CONCLUSIONS: Leg crossing combined with tensing muscles at the onset of prodromal symptoms can postpone and in some subjects prevent vasovagal syncope.

Adolescent↗
PubMed2002

Arterial baroreflex and peripheral chemoreflex function after radiotherapy for laryngeal or pharyngeal cancer.

PURPOSE: Denervation of the carotid sinus causes baroreflex and chemoreflex failure, resulting in labile hypertension and loss of hypoxic responsiveness. We investigated whether radiation therapy for laryngeal or pharyngeal cancer affects baroreflex and chemoreflex function. METHODS AND MATERIALS: Twelve patients were studied after radiation therapy for locally advanced laryngeal or pharyngeal cancer (11 male, 1 female, age: 56.0 +/- 7.9 years), 3.3 years (median; range 1.0-4.7) after radiotherapy and 15 healthy controls (11 male, 4 female, 53.4 +/- 9.2 years). We measured baroreflex sensitivity (phenylephrine), blood pressure level and variability (24-h Spacelabs and 5-h Portapres recordings), responses to cardiovascular reflex tests, and the ventilatory responses to normocapnic and hypercapnic hypoxia. RESULTS: Baroreflex sensitivity was lower in patients (9.7 +/- 7.8 ms/mm Hg) than in controls (17.5 +/- 10.3 ms/mm Hg, p = 0.011). Mean office blood pressure was significantly higher in patients (141.5 +/- 27.8/89.2 +/- 10.6 mm Hg, 63.3 +/- 12.3 bpm) than in controls (117.3 +/- 10.1/75.1 +/- 6.8 mm Hg, 61.8 +/- 10.8 bpm). Blood pressure variability was not different between groups, nor were the responses to reflex tests. The normo/hypercapnic ventilatory response to hypoxia was similar in patients (0.21 +/- 0.10/1.37 +/- 0.60 L/min/%) and controls (0.22 +/- 0.16/1.19 +/- 0.78 L/min/%). CONCLUSIONS: Radiation therapy for laryngeal or pharyngeal carcinoma does not affect chemoreflex function, but results in an attenuated baroreflex sensitivity. Clinically relevant blood pressure lability is absent however.

Baroreflex↗
PubMed2002

Long-term effects of carotid sinus denervation on arterial blood pressure in humans.

BACKGROUND: After experimental carotid sinus denervation in animals, blood pressure (BP) level and variability increase markedly but normalize to preoperative levels within 10 to 14 days. We investigated the course of arterial BP level and variability after bilateral denervation of the carotid sinus baroreceptors in humans. METHODS AND RESULTS: We studied 4 women (age 41 to 63 years) who were referred for evaluation of arterial baroreflex function because of clinical suspicion of carotid sinus denervation attributable to bilateral carotid body tumor resection. The course of BP level and variability was assessed from repeated office and 24-hour ambulatory measurements (Spacelabs/Portapres) during 1 to 10 years of (retrospective) follow-up. Rapid cardiovascular reflex adjustments to active standing and Valsalva's maneuver were assessed. Office BP level increased from 132/86 mm Hg (range, 118 to 148/80 to 92 mm Hg) before bilateral surgery to 160/105 mm Hg (range, 143 to 194/90 to 116 mm Hg) 1 to 10 years after surgery. During continuous 24-hour noninvasive BP recording (Portapres), a marked BP variability was apparent in all 4 patients. Initial symptomatic hypotension on change to the upright posture and abnormal responses to Valsalva's maneuver were observed. CONCLUSIONS: Acute carotid sinus denervation, as a result of bilateral carotid body tumor resection, has a long-term effect on the level, variability, and rapid reflex control of arterial BP. Therefore, in contrast to earlier experimental observations, the compensatory ability of the baroreceptor areas outside the carotid sinus seems to be of limited importance in the regulation of BP in humans.

Adult↗
PubMed2002

Orthostatic intolerance after space flight.

Physiologists have always been challenged by the adjustments of the human body to hostile environments. The set of papers in this issue of The Journal of Physiology (Cox et al. 2002; Ertl et al. 2002; Levine et al. 2002) fits into the tradition of the study of human responses to extreme physical circumstances. The Neurolab project represents a huge undertaking that required major contributions from many different collaborators, and the coordination of efforts at different institutions. The studies succeeded because of the dedication and years of work of the astronauts involved. The manuscripts present the fundamental findings from the first direct recordings of sympathetic vasoconstrictor nerves and noradrenaline kinetics in humans during microgravity. Despite the difficulties of performing such measurements on the space shuttle and the small numbers of astronauts involved, unique data are set forth that represent a major advance in our understanding of the physiology of space flight.

Adaptation, Physiological↗
PubMed2002

Variable day/night bias in 24-h non-invasive finger pressure against intrabrachial artery pressure is removed by waveform filtering and level correction.

BACKGROUND Twenty-four-hour finger arterial pressure (FAP) recordings show a negative bias against intrabrachial artery pressure (BAP) and the bias is greater during the night, thereby overestimating the nocturnal blood pressure dip. We have available a methodology with which to reconstruct BAP from FAP by waveform filtering (transfer function) and generalized level (bias) correction that reduces the bias for short-term blood pressure records. OBJECTIVE To investigate if this methodology also decreases the extra bias during the night, thereby yielding a better estimate of the nocturnal dip. METHODS Twenty-four-hour FAP and BAP blood pressure recordings were simultaneously obtained in eight healthy normotensive volunteers and 14 patients with hypertension (ages 19-60 years), during standardized scheduled activities. The data were analysed off-line, applying the brachial reconstruction technique (reBAP) consisting of a waveform filter and level correction. Simultaneous beats yielded systolic, diastolic and mean pressures that were averaged per 30 min, per day, per night, per activity, over the 24-h period, and for volunteers and patients separately. RESULTS Over the full 24 h, FAP systolic, diastolic and mean values for the total group differed from BAP by +1 +/- 10, -8 +/- 7 and -10 +/- 8 mmHg (mean +/- SD), respectively. Similarly, reBAPs differed by +1 +/- 11, -2 +/- 7 and -2 +/- 7 mmHg. BAPs dipped by 20 +/- 8, 13 +/- 6 and 15 +/- 6 mmHg, respectively, during the night. These dips were overestimated by +8, +4 and +4 mmHg by FAP, but not by reBAP: -1, +1 and +1 mmHg. The volunteer and the patient groups showed slight differences in results, but these were not statistically significant. CONCLUSIONS The generalized reconstruction technique to obtain near-brachial pressure from non-invasive FAP almost completely removed bias over the full 24-h day-night period and improved tracking of diurnal changes for all three blood pressure values.

Adult↗