Regional patterns of myocardial sympathetic denervation in dilated cardiomyopathy: an analysis using carbon-11 hydroxyephedrine and positron emission tomography.
OBJECTIVE: To assess presynaptic function of cardiac autonomic innervation in patients with advanced congestive heart failure using positron emission tomography (PET) and the recently developed radiolabelled catecholamine analogue carbon-11 hydroxyephedrine (HED) as a marker for neuronal catecholamine uptake function. DESIGN AND PATIENTS: 29 patients suffering from dilated cardiomyopathy with moderate to severe heart failure were compared with eight healthy controls. Perfusion scan was followed by HED dynamic PET imaging of cardiac sympathetic innervation. The scintigraphic results were compared with markers of disease severity and the degree of sympathetic dysfunction assessed by means of heart rate variability. RESULTS: In contrast to nearly normal perfusions, mean (SD) HED retention in dilated cardiomyopathy patients was abnormal in 64 (32)% of the left ventricle. Absolute myocardial HED retention was 10.7 (1.0)%/min in controls v 6.2 (1.6)%/min in dilated cardiomyopathy patients (p < 0.001). Moreover, significant regional reduction of HED retention was demonstrated in apical and inferoapical segments. HED retention was significantly correlated with New York Heart Association functional class (r = -0.55, p = 0. 002) and ejection fraction (r = 0.63, p < 0.001), but not, however, with plasma noradrenaline concentrations as well as parameters of heart rate variability. CONCLUSIONS: In this study, using PET in combination with HED in patients with dilated cardiomyopathy, not only global reduction but also regional abnormalities of cardiac sympathetic tracer uptake were demonstrated. The degree of abnormality was positively correlated to markers of severity of heart failure. The pathogenetic mechanisms leading to the regional differences of neuronal damage as well as the prognostic significance of these findings remain to be defined. (+info)
A possible mode of cardiovascular actions of dopamine in dogs.
A possible mode of cardiovascular actions of dopamine was studied using ephedrine. In the dog pretreated with repeated administrations of ephedrine (total dose, 40 or 80 mg/kg, i.v.) or with combined administrations of ephedrine (total dose, 90 mg/kg, s.c. and i.v.) and reserpine (2 mg/kg, s.c., 24 hr previously), pressor responses to dopamine were eliminated and reversed to depressor responses whereas depressor responses to dopamine were potentiated. Positive chronotropic effects of dopamine were almost eliminated. Pressor and positive chronotropic effects of tyramine were almost abolished. Sympathomimetic effect of noradrenaline and adrenaline were potentiated while those of isoprenaline were inhibited. In the heart-lung preparation of ephedrine-treated dogs (total dose, 40 mg/kg, i.v.), cardiac stimulating effects of dopamine and tyramine were strongly depressed, and those of noradrenaline, adrenaline and isoprenaline were reduced to some extent. In the open-chest dogs, after pretreatment of cocaine (4 mg/kg, i.v.), pressor, positive inotropic and chronotropic effects of noradrenaline were potentiated, whilst those of tyramine were inhibited. Those of dopamine were not visibly altered, but depressor, negative chronotropic and inotropic effects of dopamine appeared at small doses. In the ephedrine-pretreated dogs, these sympathomimetic effects of dopamine and tyramine after cocaine were strongly depressed and those of noradrenaline were inhibited to a certain degree. The results obtained with ephedrine suggest that dopamine differs from other catecholamines and tyramine in the mode of cardiovascular actions. (+info)
Heterogeneous cardiac sympathetic denervation and decreased myocardial nerve growth factor in streptozotocin-induced diabetic rats: implications for cardiac sympathetic dysinnervation complicating diabetes.
Heterogeneous myocardial sympathetic denervation complicating diabetes has been invoked as a factor contributing to sudden unexplained cardiac death. In subjects with diabetic autonomic neuropathy (DAN), distal left ventricular (LV) denervation contrasts with preservation of islands of proximal innervation, which exhibit impaired vascular responsiveness. The aims of this study were to determine whether this heterogeneous pattern of myocardial sympathetic denervation occurs in a rat model of diabetes and to explore a potential association with regional fluctuations in myocardial nerve growth factor (NGF) protein. Myocardial sympathetic denervation was characterized scintigraphically using the sympathetic neurotransmitter analog C-11 hydroxyephedrine ([11C]HED) and compared with regional changes in myocardial NGF protein abundance and norepinephrine content after 6 and 9 months in nondiabetic (ND) and streptozotocin-induced diabetic (STZ-D) rats. In ND rats, no difference in [11C]HED retention or norepinephrine content was detected in the proximal versus distal myocardium. After 6 months, compared with ND rats, myocardial [11C]HED retention had declined in the proximal segments of STZ-D rats by only 9% (NS) compared with a 33% decrease in the distal myocardium (P < 0.05). Myocardial norepinephrine content was similar in both ND and STZ-D rats. At 6 months, LV myocardial NGF protein content in STZ-D rats decreased by 52% in the proximal myocardial segments (P < 0.01 vs. ND rats) and by 82% distally (P < 0.01 vs. ND rats, P < 0.05 vs. proximal segments). By 9 months, [11C]HED retention had declined in both the proximal and distal myocardial segments of the STZ-D rats by 42% (P < 0.01 vs. ND rats), and LV norepinephrine content and NGF protein were decreased in parallel. Therefore, 6 months of STZ-induced diabetes results in heterogeneous cardiac sympathetic denervation in the rat, with maximal denervation occurring distally, and is associated with a proximal-to-distal gradient of LV NGF protein depletion. It is tempting to speculate that regional fluctuations of NGF protein in the diabetic myocardium contribute to heterogeneous cardiac sympathetic denervation complicating diabetes. (+info)
Herbal remedies: adverse effects and drug interactions.
A growing number of Americans are using herbal products for preventive and therapeutic purposes. The manufacturers of these products are not required to submit proof of safety and efficacy to the U.S. Food and Drug Administration before marketing. For this reason, the adverse effects and drug interactions associated with herbal remedies are largely unknown. Ginkgo biloba extract, advertised as improving cognitive functioning, has been reported to cause spontaneous bleeding, and it may interact with anticoagulants and antiplatelet agents. St. John's wort, promoted as a treatment for depression, may have monoamine oxidase-inhibiting effects or may cause increased levels of serotonin, dopamine and norepinephrine. Although St. John's wort probably does not interact with foods that contain tyramine, it should not be used with prescription antidepressants. Ephedrine-containing herbal products have been associated with adverse cardiovascular events, seizures and even death. Ginseng, widely used for its purported physical and mental effects, is generally well tolerated, but it has been implicated as a cause of decreased response to warfarin. Physicians must be alert for adverse effects and drug interactions associated with herbal remedies, and they should ask all patients about the use of these products. (+info)
Serial assessment of sympathetic reinnervation after orthotopic heart transplantation. A longitudinal study using PET and C-11 hydroxyephedrine.
BACKGROUND: Little is known about the progressiveness of sympathetic reinnervation late after cardiac transplantation (HTX). The aim of the present study was to describe individual growth of sympathetic terminals after HTX by a longitudinal quantitative assessment. METHODS AND RESULTS: In 20 patients after HTX, dynamic PET with C-11 hydroxyephedrine (HED) was performed twice within 3.0+/-0.5 years. According to the time interval between HTX and first PET, subgroups of patients early (group A, <1.5 years; n=7), intermediate (group B, 1.5 to 7 years; n=7) and late (group C, >7 years; n=6) after HTX were defined. At the time of first HED PET, 10 patients were completely denervated (7 in group A, 2 in group B, and 1 in group C). Only 3 remained denervated at second PET. A significant increase of reinnervated myocardium between first and second PET was found in all 3 groups (0% to 9+/-9% of left ventricle for group A, P<0.05; 13+/-12% to 23+/-17% for group B, P<0.05; 21+/-21% to 37+/-23% for group C, P<0.05). The magnitude of increase was similar between groups. Reinnervation was first surveyed in the basal anterior region, then toward apex, septal, and lateral wall. Inferior wall remained denervated. The largest reinnervated area surveyed in an individuum was 66% of the left ventricle. CONCLUSIONS: The present data confirm the low likelihood of sympathetic reinnervation within 18 months after HTX. Once the reinnervation process is initiated, a continuous growth is observed even late after HTX, suggesting a progressive nature of reinnervation. Reinnervation, however, remained regionally heterogeneous, and a complete restoration was not found until 15 years after HTX. (+info)
Acute effect of ephedrine on 24-h energy balance.
Ephedrine is used to help achieve weight control. Data on its true efficacy and mechanisms in altering energy balance in human subjects are limited. We aimed to determine the acute effect of ephedrine on 24-h energy expenditure, mechanical work and urinary catecholamines in a double-blind, randomized, placebo-controlled, two-period crossover study. Ten healthy volunteers were given ephedrine (50 mg) or placebo thrice daily during each of two 24-h periods (ephedrine and placebo) in a whole-room indirect calorimeter, which accurately measures minute-by-minute energy expenditure and mechanical work. Measurements were taken of 24-h energy expenditure, mechanical work, urinary catecholamines and binding of (+/-)ephedrine in vitro to human beta1-, beta2- and beta3-adrenoreceptors. Twenty-four-hour energy expenditure was 3.6% greater (8965+/-1301 versus 8648+/-1347 kJ, P<0.05) with ephedrine than with placebo, but mechanical work was not different between the ephedrine and placebo periods. Noradrenaline excretion was lower with ephedrine (0.032+/-0.011 microg/mg creatinine) compared with placebo (0.044+/-0.012 microg/mg creatinine) (P<0.05). (+/-)Ephedrine is a relatively weak partial agonist of human beta1- and beta2-adrenoreceptors, and had no detectable activity at human beta3-adrenoreceptors. Ephedrine (50 mg thrice daily) modestly increases energy expenditure in normal human subjects. A lack of binding of ephedrine to beta3-adrenoreceptors and the observed decrease in urinary noradrenaline during ephedrine treatment suggest that the thermogenic effect of ephedrine results from direct beta1-/beta2-adrenoreceptor agonism. An indirect beta3-adrenergic effect through the release of noradrenaline seems unlikely as urinary noradrenaline decreased significantly with ephedrine. (+info)
PET imaging of oxidative metabolism abnormalities in sympathetically denervated canine myocardium.
This study was designed to test the hypothesis that regional sympathetic denervation produces perfusion and metabolic alterations in myocardial tissue under resting conditions. METHODS: PET studies of myocardial sympathetic innervation, myocardial perfusion and oxygen utilization using [11C]hydroxyephedrine (HED), [13N]ammonia and 1-[11C]acetate, respectively, were performed before and approximately 2 and 8 wk after surgical left thoracotomy and regional chemical sympathetic denervation (n = 5). A second group of animals underwent the same surgical procedure but, so that they could serve as a sham control group, were not sympathetically denervated (n = 5). The second group of animals was imaged before and 2 wk after surgery. Images of the retention of [11C]HED taken from 50 to 60 min postinjection were used to differentiate sympathetically innervated and denervated regions of the left ventricle. Regions of interest were defined on polar plots of the [11C]HED retention, including the sympathetically denervated territory and normally innervated regions. Regions defined on the HED polar plots were then transferred to the [13N]ammonia and 1-[11C]acetate image data, and tracer kinetic models were fit to the regional time-activity curves to generate estimates of myocardial perfusion and oxidative metabolism. RESULTS: The average percentage of the left ventricle denervated in the group I animals was 13.1% +/- 7.3%. Significant reductions in oxidative metabolism were observed in the sympathectomized tissue both at 2 and 8 wk after surgery (22% and 15% reductions, respectively). Significant alterations in regional perfusion were not observed. No significant changes in oxidative metabolism or perfusion were observed in the sham control group. CONCLUSION: Regional sympathetic denervation alters oxidative metabolism but not perfusion in the denervated region of the heart. (+info)
Combined epidural-spinal opioid-free anaesthesia and analgesia for hysterectomy.
Postoperative nausea and vomiting (PONV) are major problems after gynaecological surgery. We studied 40 patients undergoing total abdominal hysterectomy, allocated randomly to receive opioid-free epidural-spinal anaesthesia or general anaesthesia with continuous epidural bupivacaine 15 mg h-1 or continuous bupivacaine 10 mg h-1 with epidural morphine 0.2 mg h-1, respectively, for postoperative analgesia. Nausea, vomiting, pain and bowel function were scored on 4-point scales for 3 days. Patients undergoing general anaesthesia had significantly higher nausea and vomiting scores (P < 0.01) but significantly lower pain scores during rest (P < 0.05) and mobilization (P < 0.01). More patients undergoing general anaesthesia received antiemetics (13 vs five; P < 0.05), but fewer received supplementary opioids on the ward (eight vs 16; P < 0.05). We conclude that opioid-free epidural-spinal anaesthesia for hysterectomy caused less PONV, but with less effective analgesia compared with general anaesthesia with postoperative continuous epidural morphine and bupivacaine. (+info)