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Biomedical subjects

A Neumann

Publications and source records attributed to A Neumann.

At least 55 records · Page 3Linked to original sources
PubMed1996

[Intensive medical monitoring with transesophageal echocardiography in fulminant pulmonary embolism].

HISTORY AND FINDINGS: A 60-year-old man underwent a continence-preserving anterior rectal resection for a high rectal carcinoma. After mobilisation on the 5th postoperative day dyspnoea and cyanosis suddenly developed requiring emergency intubation and mechanical ventilation. INVESTIGATIONS: His heart rate was 160/min, blood pressure 80/50 mmHg, mean pulmonary artery pressure by indwelling catheter was 70 mmHg. The electrocardiogram had the classical signs of acute right-heart overload. Transoesophageal echocardiography (TOE) demonstrated marked right-heart and pulmonary artery dilatation. TREATMENT AND COURSE: Despite thrombolytic treatment (bolus of 50 mg r-TPA; one day later bolus of 1 million IU urokinase followed by 100,000 IU/h) a new thromboembolus was seen by TOE to straddle the pulmonary artery bifurcation. After the urokinase dosage had been raised to 200,000 IU/h TOE on the 6th day no longer showed the embolus and documented a reduction in right-heart dilatation associated with improved haemodynamics. CONCLUSION: TOE is an ideal method for the rapid diagnosis and for monitoring the response to treatment of fulminant pulmonary arterial embolism. As it can also diagnose thromboembolism without significant haemodynamic consequences it is possible to adjust fibrinolytic treatment accordingly.

Acute Disease↗
PubMed1996

Interstitial deletion of chromosome 6q: precise definition of the breakpoints by microdissection, DNA amplification, and reverse painting.

Routine chromosomal analysis using GTG-banding alone showed a mosaic terminal deletion of 6q in a 14-week-old boy with developmental retardation, facial anomalies, agenesis of corpus callosum, cleft palate, hypotonia, short neck and pterygium colli, and minor anomalies of hands and feet. Discrepancies between the clinical findings on our patient and those described in the literature on patients having terminal deletions led to a more precise analysis of the karyotype. Reverse painting was performed on normal G-banded metaphases for exact determination of the breakpoints and on metaphases of the patient for evaluation of mosaicism. A DNA library that was obtained by microdissection of three deleted chromosomes 6 was used as a painting probe. Subsequent DNA amplification was performed with the help of topoisomerase-pretreated degenerate oligonucleotide primers. Unexpectedly, the hybridization pattern on normal metaphase chromosomes revealed an interstitial deletion with breakpoints at 6q25.1 and 6q27 instead of a terminal deletion. Hybridization on metaphases of the patient showed one deleted chromosome 6 in all metaphases analyzed at a higher resolution rather than mosaicism as previously assumed [karyotype, 46,XY,del(6)(q25.1 --> q27)]. We assume that in the single cases of 6q- described in the literature the deletions are misclassified. This might be due to difficulties in distinguishing between interstitial and terminal deletions at 6q and in precisely defining chromosomal breakpoints after GTG-banding alone.

Abnormalities, Multiple↗
PubMed1996

The effect of esmolol pretreatment on the incidence of regional wall motion abnormalities during electroconvulsive therapy.

Electroconvulsive therapy (ECT) is associated with dramatic increases in arterial blood pressure and heart rate (HR) that may precipitate new left ventricular regional wall motion abnormalities (RWMAs) suggestive of myocardial ischemia. The purpose of this study was to investigate the effect of pretreatment with esmolol on the incidence of RWMAs after ECT. Thirteen patients served as their own controls and, in a random fashion, received a standard succinylcholine/methohexital anesthetic for one of two ECT sessions, and an identical anesthetic with esmolol 1 mg/kg for their other ECT session. Systolic (SBP), diastolic (DBP), mean arterial pressures (MAP) and HR were recorded after drug administration and before ECT and at 1-, 2-, 4-, 5-, 10-, and 15-min intervals after ECT. Echocardiograms were obtained at baseline, after drug administration, 1 min after ECT, and at recovery 15 min later. All patients had significant increases in SBP, DBP, and MAP at 1, 2 and 4 min after ECT versus baseline, whereas HR was significantly faster at all times in the control sessions. HR was significantly slower after anesthetic induction until 2 min after ECT in the esmolol versus the control group (P < 0.05). New RWMAs were seen in only 1 of 26 (4%) ECT sessions, despite the presence of baseline RWMAs in 31% of the patients. We conclude that contrary to previously reported data, new RWMAs after ECT are uncommon. Consequently, this study was unable to demonstrate any beneficial effect of pretreatment with esmolol on the incidence of ECT-induced RWMAs.

Adrenergic beta-Antagonists↗
PubMed1996

Effect of left atrial size on recurrence of atrial fibrillation after electrical cardioversion: atrial dimension versus volume.

UNLABELLED: There are conflicting reports on the relationship between left atrial dimension (LAD) determined by echo-cardiography and the incidence of atrial fibrillation (AF) recurrence after electrical cardioversion (EC). We hypothesized that left atrial volume (LAV) by echocardiography might better differentiate patients who will have recurrence of AF after EC. METHODS: Forty-one patients having EC for AF were prospectively studied by echocardiography. LAD was measured by American Society of Echocardiography guidelines as the anterior-posterior dimension in the parasternal view. LAV was measured by Simpson's method using an off-line analysis system and reported as the average of values from the apical four-chamber and two-chamber views. RESULTS: (Data are mean +/- SEM): Patient follow-up was 15 +/- 10 months. No cutoff value of LAV predicted AF recurrence, but all three patients with LAD greater than 65 mm had AF recurrence. Compared with patients maintaining normal sinus rhythm (NSR) (N = 18), the AF group (N = 23) had a lower percentage of antiarrhythmic drug use, especially type IA agents (p < .02). Patients who stayed in NSR tended to have shorter AF duration before EC (16 +/- 15 v 63 +/- 122 weeks, p = .08) but did not differ in age (53 +/- 27 v 58 +/- 23 years), LAD (51.1 +/- 7.7 v 54.2 +/- 9.4 mm) or LAV (85.1 +/- 24.3 v 95.1 +/- 33.3 mL). CONCLUSIONS: (1) LAV by echocardiography does not improve identification of patients at risk for recurrence of AF after EC, (2) patients with LAD up to 65 mm may maintain NSR after EC, (3) LAD greater than 65 mm is associated with AF recurrence, and (4) use of antiarrhythmic drugs and the duration of AF before EC may be better predictors of maintenance of NSR than echocardiographic measures of left atrial parameters.

Atrial Fibrillation↗
PubMed1995

A unique left-to-right shunt characterized by multimodality cardiac imaging.

We describe the first reported patient with a persistent left superior vena cava that communicates directly with the left atrium as an isolated congenital defect. She developed mitral stenosis and physiologic conditions that favored left-to-right shunting--a modified Lutembacher's syndrome. Noninvasive cardiac imaging completely elucidated her cardiac anatomy and physiology.

Coronary Angiography↗
PubMed1994

The influence of nicotine on performance, mood, and physiological parameters as related to smoking habit, gender, and suggestibility.

Based on previous observations that sensory suggestibility might be related to cholinergic drug effects, and that individual susceptibility to nicotine as defined by response differences to various doses is lower in males, nonsmokers, and highly suggestible subjects, the present study investigated whether nicotine serum blood levels, cardiovascular responses, and sensory suggestibility show differences according to gender and smoking habit, and whether differences in nicotine susceptibility measured by a discrimination task by subjective ratings on activation can be reproduced in the direction predicted by the previous data. In a double-blind threefold cross-over design 48 subjects divided according to smoking habit, gender, and sensory suggestibility were tested in balanced order under the influence of an oral dose of 0, 0.014, or 0.028 mg/kg body weight of nicotine. Results revealed higher serum levels of nicotine in males and smokers, a dose-dependent increase in heart rate and systolic and diastolic blood pressure, partly interacting with gender or smoking habit (females and nonsmokers showing larger increase with the low doses), and a change in suggestibility in the expected direction (decrease with the low dose, increase with the large one only in female nonsmokers). A fourfold interaction among dose, smoking habit, gender, and suggestibility for the discrimination task partly reproduced the observations of higher nicotine susceptibility in females and non-smokers, whereas suggestibility did not seem to reveal the expected changes. Also, on a subjective level larger doses were necessary to make male smokers feel activated, while the other groups showed the biphasic response pattern to the two nicotine doses. In conclusion, the data justify further research on the concept of nicotine susceptibility defined by biphasic effects of nicotine on vigilance.

Administration, Oral↗
PubMed1994

Tetrachloroethene metabolism of Dehalospirillum multivorans.

Dehalospirillum multivorans is a strictly anaerobic bacterium that is able to dechlorinate tetrachloroethene (perchloroethylene; PCE) via trichloroethene (TCE) to cis-1,2-dichloroethene (DCE) as part of its energy metabolism. The present communication describes some features of the dechlorination reaction in growing cultures, cell suspensions, and cell extracts of D. multivorans. Cell suspensions catalyzed the reductive dechlorination of PCE with pyruvate as electron donor at specific rates of up to 150 nmol (chloride released) min-1 (mg cell protein)-1 (300 microM PCE initially, pH 7.5, 25 degrees C). The rate of dechlorination depended on the PCE concentration; concentrations higher than 300 microM inhibited dehalogenation. The temperature optimum was between 25 and 30 degrees C; the pH optimum at about 7.5. Dehalogenation was sensitive to potential alternative electron acceptors such as fumarate or sulfur; nitrate or sulfate had no significant effect on PCE reduction. Propyl iodide (50 microM) almost completely inhibited the dehalogenation of PCE in cell suspensions. Cell extracts mediated the dehalogenation of PCE and of TCE with reduced methyl viologen as the electron donor at specific rates of up to 0.5 mumol (chloride released) min-1 (mg protein).-1 An abiotic reductive dehalogenation could be excluded since cell extracts heated for 10 min at 95 degrees C were inactive. The PCE dehalogenase was recovered in the soluble cell fraction after ultracentrifugation. The enzyme was not inactivated by oxygen.

Biodegradation, Environmental↗
PubMed1994

Noninvasive method for determination of arterial compliance using Doppler echocardiography and subclavian pulse tracings. Validation and clinical application of a physiological model of the circulation.

BACKGROUND: The Poiseuillian model of the arterial system currently applied in clinical physiology does not explain how arterial pressure is maintained during diastole after cessation of pulsatile aortic inflow. Arterial pressure-flow relations can be more accurately described by models that incorporate arterial viscoelastic properties such as arterial compliance. Continuous pressure and flow measurements are needed to evaluate these properties. Since the techniques used to date to acquire such data have been invasive, physiological models of the circulation that incorporate these properties have not been widely applied in the clinical setting. The purpose of this study was (1) to validate noninvasive methods for continuous measurement of central arterial pressure and flow and (2) to determine normal reference values for arterial compliance using physiological models of the circulation applied to the noninvasively acquired pressure and flow data. METHODS AND RESULTS: Simultaneously acquired invasive and noninvasive aortic pressures (30 patients), flows (8 patients), and arterial mechanical properties (8 patients) were compared. Pressure was measured by high-fidelity catheter aortic micromanometer (invasive) and calibrated subclavian pulse tracing (noninvasive). Aortic inflow was determined from thermodilution-calibrated electromagnetic flow velocity data (invasive) and echo-Doppler data (noninvasive). Arterial compliance was determined for two- and three-element windkessel models of the circulation using the area method and an iterative procedure, respectively. Once validated, the noninvasive methodology was used to determine normal compliance values for a reference population of 70 subjects (age range, 20 to 81 years) with normal 24-hour ambulatory blood pressures and without Doppler-echocardiographic evidence for structural heart disease. The limits of agreement between invasive and noninvasive pressure data, compared at 10% intervals during ejection and nonejection, were narrow over a wide range of pressures, with no significant differences between methods. Invasive and noninvasive instantaneous aortic inflow values differed slightly but significantly at the start of ejection (P < .05), but during the latter 90% of ejection, values for the two methods were similar, with narrow limits of agreement. Total vascular resistance and arterial compliance values derived from invasive and noninvasive data were similar. Arterial compliance values for the normal population using the two-element model (C2E) ranged from 0.74 to 2.44 cm3/mm Hg (mean, 1.57 +/- 0.38 cm3/mm Hg), with a beat-to-beat variability of 5.2 +/- 3.9%. C2E decreased with increasing age (r = -.73, P < .001) and tended to be higher in men (1.67 +/- 0.41 cm3/mm Hg) than in women (1.51 +/- 0.35 cm3/mm Hg, P = .07). Compliance values for the three-element model (C3E) were predictably smaller than for the two-element model (mean, 1.23 +/- 0.30; range, 0.59 to 2.16 cm3/mm Hg, P < .001 versus C2E) but correlated with C2E values (r = .81, P < .001) and were also inversely related to age (r = -.56, P < .001). Ridge regression and principal component analyses both showed the compliance value to be a composite function whose variation could be best predicted by consideration of simultaneous values for five major hemodynamic determinants: heart rate, mean flow, mean aortic pressure, minimal diastolic pressure, and end-systolic pressure. Multivariate analysis revealed age and sex to be independent predictors of compliance (P < .01 for both). There were no differences in compliance between black and white subjects. CONCLUSIONS: Noninvasive methods can be used to acquire the hemodynamic data necessary for clinical application of physiological models of the circulation that incorporate arterial viscoelastic properties such as arterial compliance. The strong inverse linear relation between model-based compliance estimates and age mandates incorporation of this demographic parameter in

Adolescent↗
PubMed1994

Correlation of antiphospholipid antibodies and protein S deficiency with thrombosis in HIV-infected men.

Antiphospholipid antibodies (aPL) and free protein S (PSF) deficiency have been associated with clinical thrombosis. Previous reports described a high prevalence of these abnormalities in HIV-infected individuals, but suggested there was little associated clinical thrombosis. A cohort of 74 HIV-infected men were studied for aPL, PSF deficiency and the development of thrombosis. aPL, predominantly anticardiolipin antibodies (aCL), were detected in 86% and PSF deficiency in 33%. While 42% of men with aPL also had low PSF levels, there was no correlation between aCL titres or most measures of aPL and PSF levels. However, a strong correlation was noted between a subset of aPL that reacted to phosphatidylethanolamine by hexagonal array assay and low PSF levels. There was no significant correlation between aPL, PSF deficiency and clinical features (medication use, opportunistic infection, CD4 cell count) of HIV in 60 patients for whom clinical information was available. The overall incidence of thrombosis in this group was 18%, and thrombosis developed in 6.6% of those followed prospectively over a median follow-up of 12 months. Development of thrombosis was not significantly correlated with aPL or PSF deficiency, but the high prevalence of these abnormalities may necessitate larger study groups to determine the risk associated with these coagulation changes. Study of a larger group with careful analysis of subsets of aPL, especially those associated with low PSF levels, and longer clinical follow-up could identify the HIV-infected individuals at risk for thrombosis.

Adult↗
PubMed1993

Noninvasive assessment of the direct action of oral nifedipine and nicardipine on left ventricular contractile state in patients with systemic hypertension: importance of reflex sympathetic responses.

OBJECTIVES: This study was designed to noninvasively assess the direct action of calcium channel blockers on left ventricular contractility in humans and to establish a framework for determining the importance of reflex sympathetic responses to any pharmacologic intervention. BACKGROUND: Assessment of left ventricular contractility in patients taking calcium channel blockers by using traditional indexes of systolic performance is difficult because of the after-load-reducing and reflex sympathetic effects of the drugs. METHODS: Fifteen hypertensive patients (mean blood pressure 127 +/- 15 mm Hg) were studied with Doppler echocardiography and calibrated subclavian pulse tracings while receiving placebo and 1 week after randomization to treatment with oral nifedipine (20 mg three times daily; n = 7) or nicardipine (30 mg three times daily; n = 8). Left ventricular circumferential end-systolic wall stress versus rate-corrected velocity of shortening (Vcfc) relations were generated over a range of loads using nitroprusside. Data were acquired before and during esmolol infusion, thereby allowing assessment of hemodynamic responses with the sympathetic nervous system functionally intact as well as ablated. The adequacy of sympathetic blockade was confirmed with isoproterenol challenges. In each case, left ventricular contractile state was measured relative to placebo and esmolol data as delta Vcfc at a common end-systolic wall stress. Increased and decreased contractility were defined as delta Vcfc > 0 and delta Vcfc < 0, respectively. RESULTS: Nifedipine and nicardipine equally decreased blood pressure and end-systolic wall stress and increased left ventricular percent fractional shortening and stroke volume. Neither drug alone consistently altered ventricular contractility compared with placebo. Ablation of reflex sympathetic tone with esmolol unmasked a negative inotropic effect for nifedipine (p = 0.03 vs. esmolol alone) but not nicardipine (p = 0.68 vs. esmolol alone). The difference between the contractility effects of nifedipine plus esmolol versus those of nicardipine plus esmolol approached statistical significance (p = 0.07). CONCLUSIONS: Totally noninvasive techniques showed a differential effect on left ventricular contractility between nifedipine and nicardipine when alterations in afterload and reflex sympathetic responses were eliminated as confounding variables. This diagnostic approach, based on the use of pharmacologic probes, should have wide applicability for assessing the direct inotropic effect of any agent, even in the presence of complex primary and secondary physiologic modes of action.

Adrenergic beta-Antagonists↗
PubMed1993

Cardiovascular consequences of correction of the anemia of renal failure with erythropoietin.

The purpose of this study was to define the physiologic responses of the heart and peripheral circulation to chronic anemia using noninvasive measurements while eliminating confounding biochemical, pharmacologic and physiologic variables. Stable chronic hemodialysis patients were studied at the University Hospital based chronic dialysis unit and echocardiography laboratory before and after therapy with human recombinant erythropoietin (rHuEPO). Subjects included maintenance hemodialysis patients free of left ventricular regional wall motion abnormalities discernible by echocardiography, rhythm disturbance, significant valvular or ischemic heart disease. Two-dimensional echocardiograms and simultaneous targeted M-mode echocardiograms, phonocardiograms and externally acquired subclavian artery pulse tracings were used to measure whole blood viscosity, arterial blood gases and ionized calcium, complete blood count, electrolytes, creatinine, blood urea nitrogen (BUN), and inorganic phosphate. All measurements were made immediately post-dialysis before and after therapy with rHuEPO. The interval between pre- and post-rHuEPO studies was 8.3 +/- 2.3 months. We found that post-dialysis hematocrit rose from 24.7 +/- 0.9 to 36.4 +/- 0.9%, hemoglobin from 83 +/- 3 to 121 +/- 3 g/liter and whole blood viscosity from 2.87 +/- 0.11 to 3.71 +/- 0.18 centipoise (all, P < 0.001 after therapy with rHuEPO). The remaining biochemical measurements did not change. Heart rate fell from 83 +/- 3 to 77 +/- 3 beats/min (P = 0.013). Left ventricular preload and afterload were not statistically different before and after rHuEPO. Total vascular resistance rose from 1313 +/- 84 to 1568 +/- 129 dynes.sec.cm-5, P = 0.029. Cardiac output and cardiac index fell by 12 and 15% (P = 0.024 and 0.030), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Transfusion-associated transmission of human T-lymphotropic virus types I and II: experience of a regional blood center.

During a 22-month period, 78,000 blood donors were screened for human T-lymphotropic virus types I and II (HTLV-I/II) at Belle Bonfils Memorial Blood Center (Denver, Colorado). Positive donors and the living recipients of their previously donated blood components were evaluated for risk factors and symptoms related to HTLV-I infection, were screened by enzyme immunoassay, confirmed by Western blot for HTLV-I/II, and subsequently tested by polymerase chain reaction and peptide enzyme immunoassay to distinguish between HTLV-I and -II infection. Six seropositive blood donors (0.008%) were identified; four were typed as having HTLV-I infection and two as having HTLV-II. Of 18 living recipients of components from seropositive donors, none had risk factors for HTLV-I infection prior to transfusion and none had signs or symptoms of HTLV-I infection at follow-up. The mean time from transfusion to testing was 6.4 years. Seven recipients of HTLV-I-infected components were HTLV seropositive; all were typed as having HTLV-I. A possible case of posttransfusion HTLV-I-associated myelopathy was identified in one patient who died before complete evaluation. One possible case of transfusion-associated HTLV-II was identified. These data further support the continued screening of blood donors for HTLV-I/II.

Adult↗
PubMed1993

Fluorescence in-situ hybridisation and molecular studies used in the characterisation of a Robertsonian translocation (13q15q) in Prader-Willi syndrome.

A patient with classical Prader-Willi syndrome was found to have a Robertsonian translocation 45,XY,t(13q15q)mat. On CBG banding, the translocation chromosome had a large centromere with one primary constriction. Using fluorescence in situ hybridisation, positive signals were obtained with chromosome 13 and chromosome 15 centromere probes, proving that the translocation was dicentric. NOR banding was negative in this chromosome, suggesting that the breakpoints were at 13p11 and 15p11. DNA studies showed that, while there was no deletion involving 15(q11-13), maternal uniparental disomy for chromosome 15 was present. We compare our findings with the five other cases of familial Robertsonian translocation PWS that have been reported.

Adult↗
PubMed1992

Effects of simultaneous alterations in preload and afterload on measurements of left ventricular contractility in patients with dilated cardiomyopathy: comparisons of ejection phase, isovolumetric and end-systolic force-velocity indexes.

OBJECTIVES: The study was designed to critically evaluate the clinical utility of ejection phase and nonejection phase indexes of contractile state in patients with severe left ventricular dysfunction. BACKGROUND: Ejection phase indexes of left ventricular systolic performance are unable to differentiate contractility changes from alterations in loading conditions. Isovolumetric and end-systolic force-velocity indexes have been proposed as alternative measurements of contractile state that are load independent. METHODS: Seventeen patients with nonischemic dilated cardiomyopathy were studied during cardiac catheterization. High fidelity central aortic and left ventricular pressure measurements were made with simultaneous echocardiographic recordings of chamber minor- and long-axis dimensions and wall thickness. Data were acquired under control conditions, during nitroprusside infusion and with dopamine (6 micrograms/kg per min). RESULTS: Patients were classified into those without (group 1, n = 10) and those with (group 2, n = 7) a decrease in end-diastolic circumferential wall stress in response to dopamine. There were no baseline differences between the groups in functional class, left ventricular chamber geometry or cardiovascular hemodynamics. Ejection phase indexes were variably altered by changes in preload, afterload and heart rate, thereby complicating physiologic interpretation of data. Dopamine increased the commonly used isovolumetric index, maximal rate of rise in left ventricular pressure (dP/dtmax), by 64% for group 1 but by only 16% for group 2 (p less than 0.001), resulting in an underestimation of contractile state change in 41% of patients. In contrast, the left ventricular end-systolic circumferential wall stress-rate-corrected velocity of fiber shortening relation, which incorporates afterload, ventricular wall mass and heart rate in its analysis, was a sensitive contractility measurement that was preload independent and equally augmented by dopamine for both groups. CONCLUSIONS: Of the left ventricular contractility indexes evaluated, the end-systolic circumferential wall stress-rate-corrected velocity of fiber shortening relation was the most physiologically appropriate for assessing pharmacologically induced changes in inotropic state that were accompanied by complex alterations in loading conditions in patients with dilated cardiomyopathy.

Cardiac Catheterization↗
PubMed1992

Influence of histamine receptors on basal left ventricular contractile tone in humans: assessment using the H2 receptor antagonist famotidine and the beta-adrenoceptor antagonist esmolol as pharmacologic probes.

Histamine has a positive inotropic action in humans. Recent controversial data have suggested that histamine2 (H2) receptor blockade depresses overall left ventricular systolic performance in healthy volunteers. To explore the possibility that H2 receptors positively influence basal left ventricular contractile tone, 10 normal subjects were studied by using imaging and Doppler echocardiography and calibrated subclavian pulse data in a blinded, randomized, two-period crossover trial with measurements obtained at the end of each 7-day period. Oral drug administration consisted of either the potent H2 antagonist famotidine (40 mg/day) or placebo. Left ventricular circumferential end-systolic wall stress-rate-corrected velocity of fiber shortening (Vcfc) relations were generated over a range of loads with methoxamine. Contractility was assessed by using Vcfc at a common end-systolic wall stress. During each study, data were obtained before and during high dose intravenous esmolol administration to determine the contributions, if any, of sympathetic reflex responses. Famotidine did not alter blood pressure, left ventricular percent fractional shortening, circumferential end-systolic wall stress, stroke volume index, cardiac index, total vascular resistance or ventricular contractile state in comparison with placebo but did decrease heart rate by 3 beats/min (p less than 0.05). With beta-adrenergic blockade, no differences in contractility were evident between esmolol alone and famotidine plus esmolol. Thus, H2 receptor blockade with famotidine does not alter myocardial mechanics or cardiac sympathetic tone, suggesting that in humans basal left ventricular contractile state is not physiologically dependent on the H2-mediated effects of histamine.

Adolescent↗