PubMed Health⌕ Search

Biomedical subjects

C T Paul Krediet

Publications and source records attributed to C T Paul Krediet.

11 recordsLinked to original sources
PubMed2007

Initial orthostatic hypotension: review of a forgotten condition.

Several studies have shown that standing up is a frequent (3-10%) trigger of loss of consciousness both in young and old subjects. An exaggerated transient BP (blood pressure) fall upon standing is the underlying cause. IOH (initial orthostatic hypotension) is defined as a transient BP decrease within 15 s after standing, >40 mmHg SBP (systolic BP) and/or >20 mmHg DBP (diastolic BP) with symptoms of cerebral hypoperfusion. It differs distinctly from typical orthostatic hypotension (i.e. BP decrease >20 mmHg SBP and/or >10 mmHg DBP after 3 min of standing) as the BP decrease is transient. Only continuous beat-to-beat BP measurement during an active standing-up manoeuvre can document this condition. As IOH is only associated with active rising, passive tilting is of no diagnostic value. The pathophysiology of IOH is thought to be a temporal mismatch between cardiac output and vascular resistance. The marked decrease of vascular resistance during rising is similar to that observed at the onset of leg exercise and is absent during head-up tilting. It is attributed to vasodilatation in the working muscle through local mechanisms. Standing up causes an initial increase in venous return through the effects of contraction of leg and abdominal muscles. The consequent sudden increase in right atrial pressure may contribute to the fall in systemic vascular resistance through a reflex effect. This review alerts clinicians and clinician scientists to a common, yet often neglected, condition that occurs only upon an active change of posture and discusses its epidemiology, pathophysiology and management.

Cardiac Output↗
PubMed2006

Leg crossing improves orthostatic tolerance in healthy subjects: a placebo-controlled crossover study.

Vasovagal syncope is the most common cause of transient loss of consciousness, and recurrent vasovagal fainting has a profound impact on quality of life. Physical countermaneuvers are applied as a means of tertiary prevention but have so far only proven useful at the onset of a faint. This placebo-controlled crossover study tested the hypothesis that leg crossing increases orthostatic tolerance. Nine naïve healthy subjects [6 females, median age 25 yr (range 20-41 yr), mean body mass index 23 (SD 2)] were subjected to passive head-up tilt combined with a graded lower body negative pressure challenge (20, 40, and 60 mmHg) determining orthostatic tolerance thrice, in randomized order: 1) control, 2) with leg crossing, and 3) with oral placebo. Blood pressure (Finometer), heart rate, and changes in thoracic blood volume (impedance), stroke volume, and cardiac output (Modelflow) were followed during orthostatic stress. Primary outcome was time to presyncope (systolic blood pressure </=85 mmHg, heart rate >/=140 beats/min). With leg crossing, orthostatic tolerance increased from 26 +/- 2 to 34 +/- 2 min (placebo 23 +/- 3 min, P < 0.001). During leg crossing, mean arterial pressure (81 vs. 81 mmHg) and cardiac output (95 vs. 94% supine) remained unchanged; heart rate increase was lower (13 vs. 18 beats/min, P < 0.05); stroke volume was higher (79 vs. 74% supine, P < 0.05); and there was a trend toward lower thoracic impedance. Leg crossing increases orthostatic tolerance in healthy human subjects. As a measure of prevention, it is a worthwhile addition to the management of vasovagal syncope.

Adult↗
PubMed2005

Syncope during exercise, documented with continuous blood pressure monitoring during ergometer testing.

A 27-year old female had one episode of transient loss of consciousness and several of near-unconsciousness during strenuous exercise and sexual activity. Episodes started with abdominal discomfort or nausea and light headedness. Unconsciousness never exceeded one minute. When trying to stand up, she felt she would lose consciousness again. We performed a bicycle ergometer exercise test, continuously monitoring blood pressure via non-invasive finger photoplethysmography (Finometer, FMS, The Netherlands). Beat-to-beat changes in stroke volume, cardiac output and total peripheral resistance were calculated using Modelflow (FMS, The Netherlands). At a power of 140 W, the patient reported being near exhaustion; shortly after this she reported nausea. She stopped cycling 30 s later, then saw "black spots" and felt an oncoming loss of consciousness. Dismounting the ergometer and squatting provided immediate relief from symptoms. Symptoms during the test were similar to those during previous episodes. The diagnosis was exercise-induced vasovagal reactions. This is the first report that documents the beat-to-beat changes in blood pressure, stroke volume and total peripheral resistance during exercise-induced vasovagal syncope. It illustrates the usefulness of combining exercise testing with continuous non-invasive blood pressure monitoring in the diagnostic work-up of exercise-induced syncope, and shows the therapeutic value of squatting to prevent loss of consciousness in exercise-related vasovagal syncope.

Adult↗
PubMed2005

Leg crossing, muscle tensing, squatting, and the crash position are effective against vasovagal reactions solely through increases in cardiac output.

Tensing of lower body muscles without or with leg crossing (LBMT, LCMT), whole body tensing (WBT), squatting, and sitting with the head bent between the knees ("crash position", HBK) are believed to abort vasovagal reactions. The underlying mechanisms are unknown. To study these interventions in patients with a clinical history of vasovagal syncope and a vasovagal reaction during routine tilt table testing, we measured blood pressure (BP) continuously with Finapres and derived heart rate, stroke volume, cardiac output (CO), and total peripheral resistance using Modelflow. In series A (n = 12) we compared LBMT to LCMT. In series B (n = 9), WBT was compared with LCMT. In series C (n = 14) and D (n = 9), we tested squatting and HBK. All maneuvers caused an increase in BP, varying from a systolic rise from 77 +/- 8 to 104 +/- 18 mmHg (P < 0.05) in series A during LBMT to a rise from 70 +/- 10 to 123 +/- 9 mmHg (P < 0.05) in series B during LCMT. In each maneuver, the BP increase started within 3-5 s from start of the maneuver. In all maneuvers, there was an increase in CO varying from 54 +/- 12% of baseline to 94 +/- 21% in WBT to a rise from 65 +/- 17% to 110 +/- 22% in LCMT in series A. No maneuver caused significant change in total peripheral resistance. We conclude that the mechanism underlying the effects of these maneuvers is exclusively an increase in CO.

Adolescent↗
PubMed2004

Exercise related syncope, when it's not the heart.

Syncope or pre-syncope in association with physical exercise may be the first indication of a dangerous underlying cardiovascular condition. Thus, the diagnostic workup of patients presenting with exercise-related syncope must include assessment of the risk for acute cardiac death. When potentially lethal conditions have been ruled out, several hypotensive syndromes that are associated with exercise should be considered. This review aims to give a concise overview of several forms of exercise- related functional hypotensive syndromes causing syncope, including the physiology of post-exercise hypotension. The focus is on underlying mechanisms, clinical considerations, and outlining treatment strategies for these syndromes.

Autonomic Nervous System Diseases↗
PubMed2004

Nonpharmacological treatment of reflex syncope.

Reflex syncope is a common medical problem. Vasovagal reflex syncope is the most frequent form. Although the prognosis of the disorder is excellent, it may impose substantial changes in life style and cause profound psychological distress. Thus, management of this disorder is an important issue. This chapter, based on a review of the literature and the authors' clinical experience, encompasses the non-pharmacological measures used in the management of reflex syncope. The cornerstone of the non-pharmacological management of patients with reflex syncope is education and reassurance regarding the benign nature of the condition. Patients should be instructed to avoid potential triggers. A tilt table test can be employed to teach the patient to recognize early premonitory symptoms. There are several physical maneuvers (e. g., leg crossing, muscle tensing and squatting) that are effective in combating orthostatic intolerance. For the majority of patients this approach is adequate. Patients with frequent attacks of reflex syncope are advised to increase their dietary salt intake. Exercise training also increases orthostatic tolerance. In highly motivated patients with recurrent syncope, raising the head of the bed to permit gravitational exposure during sleep and prolonged periods of enforced maintenance of the upright posture (tilt-training) can be considered. Preliminary data suggest that water drinking may improve orthostatic tolerance. Abdominal belts may also be effective in highly symptomatic subjects with reflex syncope.

Abdomen↗
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↗