Effects of moderate exercise training on plasma volume, baroreceptor sensitivity and orthostatic tolerance in healthy subjects.
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The effect of physical training on an individual's ability to withstand an orthostatic stress is unclear. This study was undertaken to determine the effects on orthostatic tolerance in healthy volunteers of training at a level appropriate for unfit subjects and cardiorespiratory patients. In 11 asymptomatic, untrained subjects the following assessments were made: plasma volume by Evans Blue dye dilution and blood volume derived from haematocrit; carotid baroreceptor sensitivity from the slope of the regression of change in cardiac interval against pressure applied to a neck chamber; orthostatic tolerance as time to presyncope in a test of head-up tilting combined with lower body suction; exercise test relating heart rate to oxygen consumption. Subjects were then given a training schedule (5BX/XBX, Royal Canadian Air Force) involving 11-12 min of mixed exercises per day until an age/sex related 'target' was reached. Following training all subjects showed evidence of improved fitness, seen as decreases in heart rate at an oxygen uptake (Vo2) of 1.5 1 min-1 and in the elevation of the regression line between heart rate and Vo2. All also had increases in plasma and blood volumes and decreases in baroreceptor sensitivity. Seven of the subjects showed increases in orthostatic tolerance. Improvement in orthostatic tolerance was related to a low initial tolerance, and was associated with increases in plasma volume and decreases in baroreceptor sensitivity. These results show that moderate exercise training increases orthostatic tolerance in subjects who do not already have a high initial tolerance and suggest that training may be of value in the management of untrained patients with attacks of syncope due to orthostatic intolerance. (+info)
The misdiagnosis of epilepsy and the management of refractory epilepsy in a specialist clinic.
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We assessed the frequency, causes and consequences of erroneous diagnosis of epilepsy, and the outcome of patients referred with 'refractory epilepsy', by retrospective analysis of the case records of 324 patients. The sample was divided into those exposed to anti-epileptic drugs (n = 184), of whom 92 were said to have refractory seizures, and those who had not received treatment (n = 140). The latter group is reported elsewhere. The overall misdiagnosis rate was 26.1% (46/184), with incomplete history-taking and misinterpretation of the EEG equally responsible. Side-effects were reported by 19/40, while unnecessary driving restrictions and employment difficulties were encountered by 12/33 and 5/33, respectively. Of those labelled 'refractory epilepsy', 12 did not have epilepsy. Sixteen were rendered seizure-free and 25 significantly improved by the optimal use of anti-epileptic drugs or surgery. Diagnostic and management services for patients with suspected and established epilepsy are suboptimal, with psychological and socio-economic consequences for individual patients. The resulting economic burden on the health and welfare services is probably substantial. (+info)
Comparing two different protocols for tilt table testing: sublingual glyceryl trinitrate versus isoprenaline infusion.
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OBJECTIVE: To assess the diagnostic value and safety of sublingual glyceryl trinitrate tilt testing compared with isoprenaline infusion in patients with unexplained syncope. DESIGN: Glyceryl trinitrate and isoprenaline tilt tests were performed in two successive days on a random basis in cases and controls. SETTING: Outpatient cases with syncope referred to Shahid Rajaii Heart Hospital. SUBJECTS: 65 consecutive patients with unexplained syncope after thorough work up; 20 healthy volunteers. RESULTS: Positive responses were observed in 20 patients during the passive phase. Of the other 45 patients, positive responses occurred in 25 cases during the glyceryl trinitrate phase and in 26 cases during the isoprenaline phase. In the control group, positive responses during the passive, glyceryl trinitrate, and isoprenaline phases occurred in one, one, and two cases, respectively. The sensitivity and specificity of the protocols were 55% and 94.7%, respectively, for glyceryl trinitrate v 58% and 89.4% for isoprenaline. Owing to discordant responses in 75% of the cases, the sequential use of the tests (if one was negative) would increase the sensitivity to 84% while decreasing the specificity slightly (to 84%). Side effects were less frequent with glyceryl trinitrate. CONCLUSIONS: Sublingual glyceryl trinitrate tilt testing is an effective and safe alternative to the isoprenaline infusion test and can be used as a complementary test. (+info)
Hypokalemia with syncope caused by habitual drinking of oolong tea.
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A 61-year-old woman developed hypokalemia, atrioventricular block and ventricular tachycardia with syncope after habitual drinking 2 to 3 liters of oolong tea per day. She had been suffering from rheumatoid arthritis and Sjogren's syndrome and her serum albumin was decreased (2.9 g/dl). Oolong tea contains caffeine at approximately 20 mg/dl. Great quantities of caffeine can induce hypokalemia. The serum protein binding caffeine is albumin. Accordingly, in patients with hypoalbuminemia, caffeine is apt to induce hypokalemia. This case suggested that great quantities of oolong tea, one of the so-called "healthy" drinks, result in serious symptoms for patients with hypoalbuminemia. (+info)
Carotid sinus hypersensitivity--a modifiable risk factor for fractured neck of femur.
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BACKGROUND: the potential impact on morbidity, mortality and health care economics makes it important to identify patients at risk of fracture, in particular fractured neck of femur (FNOF). Older patients with carotid sinus hypersensitivity (CSH) are more likely to have unexplained falls and to experience fractures, particularly FNOF. Our objective was to determine the prevalence of CSH in patients with FNOF. DESIGN: case-controlled prospective series. METHODS: consecutive cases were admissions over 65 years with FNOF. Controls were consecutive patients admitted for elective hip surgery, frail elderly people admitted to hospital medical wards and day-hospital patients. All patients had a clinical assessment of cognitive function, physical abilities and history of previous syncope, falls and dizziness, in addition to repeated carotid sinus massage with continuous heart rate and phasic blood pressure measurement. RESULTS: heart rate slowing and fall in systolic blood pressure was greater for patients with FNOF than those admitted for elective hip surgery (P < 0.05 and P < 0.001). CSH was present in 36% of the FNOF group, none of the elective surgery group, 13% of the acutely ill controls and 17% of the outpatients. It was more likely to be present in FNOF patients with a previous history of unexplained falls or an unexplained fall causing the index fracture. The heart rate and systolic blood pressure responses to carotid sinus stimulation were reproducible. CONCLUSION: older patients with an acute neck of femur fracture who do not give a clear history of an accidental fall or who have had previously unexplained falls are likely to have CSH. CSH may be a modifiable risk factor for older patients at risk of hip fracture. (+info)
Outcome of patients with nonischemic dilated cardiomyopathy and unexplained syncope treated with an implantable defibrillator.
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OBJECTIVES: The purpose of this study was to determine the outcome of patients with nonischemic dilated cardiomyopathy, unexplained syncope and a negative electrophysiology test who are treated with an implantable defibrillator. BACKGROUND: Patients with nonischemic cardiomyopathy and unexplained syncope may be at high risk for sudden cardiac death, and they are sometimes treated with an implantable defibrillator. METHODS: This study prospectively determined the outcome of 14 consecutive patients who had a nonischemic cardiomyopathy, unexplained syncope and a negative electrophysiology test and who underwent defibrillator implantation (Syncope Group). Nineteen consecutive patients with a nonischemic cardiomyopathy and a cardiac arrest who were treated with a defibrillator (Arrest Group) served as a control group. RESULTS: Seven of 14 patients (50%) in the Syncope Group received appropriate shocks for ventricular arrhythmias during a mean follow-up of 24+/-13 months, compared with 8 of 19 patients (42%) in the Arrest Group during a mean follow-up of 45+/-40 months (p = 0.1). The mean duration from device implantation until the first appropriate shock was 32+/-7 months (95% confidence interval [CI], 18 to 45 months) in the Syncope Group compared to 72+/-12 months (95% CI, 48 to 96 months) in the Arrest Group (p = 0.1). Among patients who received appropriate shocks, the mean time from defibrillator implantation to the first appropriate shock was 10+/-14 months in the Syncope Group, compared with 48+/-47 months in the Arrest Group (p = 0.06). Recurrent syncope was always associated with ventricular tachyarrhythmias. CONCLUSIONS: The high incidence of appropriate defibrillator shocks and the association of recurrent syncope with ventricular arrhythmias support the treatment of patients with nonischemic cardiomyopathy, unexplained syncope and a negative electrophysiology test with an implantable defibrillator. (+info)
Neurally mediated cardiac syncope: autonomic modulation after normal saline infusion.
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OBJECTIVES: This study assessed the heart variability response to orthostatic stress during tilt table testing before and after normal saline administration. BACKGROUND: The efficacy of sodium chloride and mineralocortoid in the treatment of neurally mediated cardiac syncope is attributed to intravascular volume expansion; however, their modulation of autonomic nervous system activity has not been evaluated. METHODS: Heart rate variability analysis was performed on 12 adolescents with a history of syncope or presyncope (mean age 15.2+/-0.7 years) during tilt table testing. Subjects were upright 80 degrees for 30 min or until syncope. After normal saline administration, the patient was returned upright for 30 min. Heart rate variability analysis data were analyzed by an autoregression model (Burg method). RESULTS: All subjects reproducibly developed syncope during control tilt table testing; median time to syncope was 9.4+/-2.1 min. After normal saline infusion, none of the subjects developed syncope after 30 min upright. In the control tilt, there was an initial increase followed by a progressive decrease in low frequency power until syncope. Repeat tilt after normal saline administration demonstrates that low frequency power increased but the magnitude of initial change was blunted when compared with control. In addition, low frequency power increased during normal saline tilt sequence compared with the control tilt, during which it decreased. CONCLUSIONS: Normal saline blunted low frequency power stimulation and prevented paradoxical low frequency power (sympathetic) withdrawal. Increasing intravascular volume with normal saline alters autonomic responses that may trigger neurally mediated syncope reflexes. (+info)
Poor reproducibility of false-positive tilt testing results in healthy volunteers.
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Positive responses to head-up tilt testing occur in healthy subjects. However, the reproducibility of "false-positive" tilt testing results has not been clarified. To study the reproducibility of "false-positive" responses, we prospectively performed 2 tilt tests separated by 1 to 10 (mean 3.2) weeks in 20 healthy males aged 23 to 40 years (mean 30 years). The baseline tilt test (80 degrees for 30 minutes) ended positive in 4 (20%) subjects on the initial test and 2 (10%) on the second test with only 1 (5%) who had consecutive positive responses. No additional positive responses were noted during the isoproterenol (0.01 microgram/kg/min)-tilt test for 10 minutes. We demonstrated that a false-positive response occurred in 5 (25%) of 20 young males who underwent 2 tilt tests, however, only 1 (5%) subject had consecutive positive responses. Poor reproducibility may be characteristic of false-positive responses in head-up tilt testing. (+info)