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Biomedical subjects

A Kardos

Publications and source records attributed to A Kardos.

At least 19 recordsLinked to original sources
PubMed2006

Trendelenburg positioning does not prevent a decrease in cardiac output after induction of anaesthesia with propofol in children.

BACKGROUND AND OBJECTIVE: Induction of anaesthesia may cause decreased cardiac output and blood pressure. Head-down tilt is often the first clinical step to treat hypotension. The objective of this randomized single centre study was to determine, with the use of impedance cardiography (ICG), whether Trendelenburg positioning modifies the haemodynamic response to propofol/fentanyl induction of anaesthesia in ASA I children. METHODS: Thirty ASA I children aged between 7 and 16 years scheduled for elective minor orthopaedic surgery were included. After intravenous induction with propofol and fentanyl in the head-down group (HDG, n = 15), 5 min of 20 degrees head-down tilt was applied. In the supine group (SG, n = 15), no change in the supine position was made. Heart rate (HR), mean arterial blood pressure (MABP), end-tidal carbon dioxide (ETCO(2)), stroke volume index (SVI), cardiac index (CI), systemic vascular resistance index (SVRI) and Heather index (HI) were recorded before (B), at 3 (A(3)), 5 (A(5)) and 8 (A(8)) minutes after induction in each group. RESULTS: After induction, a significant decrease in CI, MABP, HR and HI was recorded in both groups. In the study group, significantly lower values of HR (66 vs. 78 beat/min) and higher values of SVI (42.9 vs. 40.6 ml/min/m(2)) were measured at A(3) compared with the control group. After induction, no difference in CI and SVRI was found between the two groups. CONCLUSION: The present study shows that cardiac performance is not improved by Trendelenburg positioning after propofol/fentanyl induction of anaesthesia in children.

Adolescent↗
PubMed2005

Heterozygous disruption of SERCA2a is not associated with impairment of cardiac performance in humans: implications for SERCA2a as a therapeutic target in heart failure.

OBJECTIVE: To verify whether a deficiency in the cardiac sarcoplasmic reticulum pump SERCA2a causes cardiac dysfunction in humans. DESIGN: Cardiac performance was measured in a serendipitous human model of primary SERCA2a deficiency, Darier's disease, an autosomal dominant skin disorder caused by mutations inactivating one copy of the ATP2A2 gene, which encodes SERCA2a. METHODS: Systolic and diastolic function and contractility were assessed by echocardiography at rest and during exercise in patients with Darier's disease with known mutations. Fourteen patients with Darier's disease were compared with 14 normal controls and six patients with dilated cardiomyopathy with stable heart failure. RESULTS: Resting systolic and diastolic function was normal in patients with Darier's disease and in controls. The increase in systolic function during exercise was not different between patients with Darier's disease and normal controls; neither was there a difference in contractility. As expected, patients with dilated cardiomyopathy had impaired diastolic and systolic function with depressed contractility at rest and during exercise. CONCLUSION: Contrary to expectations, heterozygous disruption of SERCA2a is not associated with the impairment of cardiac performance in humans. Attempts to increase SERCA2a levels in heart failure, although showing promise in rodent studies, may not be addressing a critical causal pathway in humans.

Calcium-Transporting ATPases↗
PubMed2005

Haemodynamic changes during positive-pressure ventilation in children.

BACKGROUND: Positive-pressure ventilation may alter cardiac function. Our objective was to determine with the use of impedance cardiography (ICG) whether altering airway pressure modifies the central haemodynamics in mechanically ventilated children with no pulmonary pathology. Central venous saturation (S(cv)O(2)) was measured as an indicator of tissue perfusion. METHODS: Twelve children between 7 and 65 months of age, requiring mechanical ventilation as a consequence of a non-pulmonary disease, were enrolled in the study. All patients had a central venous line as a part of their routine management. Using pressure controlled ventilation (PCV) the baseline PEEP value of 5 cmH(2)O (P(b5)) was increased to 10 cmH(2)O (P(i10)) and then to 15 cmH(2)O (P(i15)). After P(i15), PEEP was decreased to 10 (P(d10)) and then to 5 cmH(2)O (P(d5)). Each time period lasted 5 min heart rate (HR), mean arterial blood pressure (MABP), central venous pressure (CVP), end-tidal carbon dioxide (ETCO(2)), mean airway pressure (P(aw)), stroke volume index (SVI), cardiac index (CI) and central venous oxygen saturation (S(cv)O(2)) were recorded at the end of the five periods. RESULTS: The values of CI did not change when 10 and 15 cmH(2)O of PEEP were applied. Elevation of PEEP and thus P(aw) caused slight but not significant reductions in SVI and S(cv)O(2) as compared to the baseline (T(b5)). After reducing PEEP in T(d5) we found statistically significant elevations of SVI and CI, as compared to T(i15) heart rate, ETCO(2) and MABP remained unchanged. CONCLUSION: We did not find significant haemodynamic changes following PEEP elevation in ventilated children, as measured using impedance cardiography. Reducing the value of PEEP to 5 cmH(2)O resulted in statistically significant SVI elevations. The values of S(cv)O(2) remained unaffected.

Air Pressure↗
PubMed2002

Electrocardiographic measures of left ventricular hypertrophy show greater heritability than echocardiographic left ventricular mass.

AIMS: To assess the heritability (i.e. relative contribution of genetic factors to the variability) of continuous measures of left ventricular hypertrophy determined by electrocardiography and echocardiography. METHODS AND RESULTS: We studied 955 members of 229 Caucasian families, ascertained through a hypertensive proband. Electrocardiographic measurements were performed manually on resting 12-lead electrocardiograms, and echocardiographic measurements were made on M-mode images. Sex-specific residuals for the left ventricular phenotypes were calculated, adjusted for age, systolic blood pressure, weight, height, waist-hip ratio, and presence of diabetes. Heritability was estimated in two ways: firstly, from familial correlations with adjustment for spouse resemblance; and secondly by using variance components methods with ascertainment correction for proband status. The heritability estimates (given as a range derived from the two methods) were higher for Sokolow-Lyon voltage (39-41%) than for echocardiographic left ventricular mass (23-29%). Electrocardiographic left ventricular mass, Cornell voltage, and Cornell product had heritability estimates of 12-18%, 19-25%, and 28-32%, respectively. CONCLUSIONS: Genetic factors may explain a substantial proportion of variability in quantitative electrocardiographic and echocardiographic measures of left ventricular hypertrophy. The greater heritability of Sokolow-Lyon voltage suggests that electrocardiographic phenotypes may be particularly important for the molecular investigation of the genetic susceptibility to cardiac hypertrophy.

Echocardiography↗
PubMed2001

Identification of higher brain centres that may encode the cardiorespiratory response to exercise in humans.

1. Positron emission tomography (PET) was used to identify the neuroanatomical correlates underlying 'central command' during imagination of exercise under hypnosis, in order to uncouple central command from peripheral feedback. 2. Three cognitive conditions were used: condition I, imagination of freewheeling downhill on a bicycle (no change in heart rate, HR, or ventilation, V(I)): condition II, imagination of exercise, cycling uphill (increased HR by 12 % and V(I) by 30 % of the actual exercise response): condition III, volitionally driven hyperventilation to match that achieved in condition II (no change in HR). 3. Subtraction methodology created contrast A (II minus I) highlighting cerebral areas involved in the imagination of exercise and contrast B (III minus I) highlighting areas activated in the direct volitional control of breathing (n = 4 for both; 8 scans per subject). End-tidal P(CO(2)) (P(ET,CO(2))) was held constant throughout PET scanning. 4. In contrast A, significant activations were seen in the right dorso-lateral prefrontal cortex, supplementary motor areas (SMA), the right premotor area (PMA), superolateral sensorimotor areas, thalamus, and bilaterally in the cerebellum. In contrast B, significant activations were present in the SMA and in lateral sensorimotor cortical areas. The SMA/PMA, dorso-lateral prefrontal cortex and the cerebellum are concerned with volitional/motor control, including that of the respiratory muscles. 5. The neuroanatomical areas activated suggest that a significant component of the respiratory response to 'exercise', in the absence of both movement feedback and an increase in CO(2) production, can be generated by what appears to be a behavioural response.

Adult↗
PubMed2001

Use of impedance cardiography to monitor haemodynamic changes during laparoscopy in children.

METHODS: Haemodynamic changes were measured noninvasively using impedance cardiography (ICG) in 30 ASA I children during laparoscopic varicocelectomy under general anaesthesia. After induction and intubation, mechanical ventilation was started, then pneumoperitoneum (PP) was created. During the course of anaesthesia, values of endtidal CO2 pressue (PECO2), peak inspiratory airway pressure (PIP), heart rate (HR), mean arterial blood pressure (MABP), stroke volume index (SVI), cardiac index (CI) and systemic vascular resistance index (SVRI) were recorded at 1 min intervals. We analysed four periods: T1, before induction; T2, after induction; T3, during PP; T4, after desufflation of PP until awake. RESULTS: After induction of anaesthesia a significant reduction of HR, MABP and CI was recorded. Creating PP together with the use of a 15 degrees head down tilt resulted in a further drop in CI, mainly caused by the reduction of SVI, and an elevation of MABP and SVRI. We measured a 25% total decrease of CI. CONCLUSION: Our patients tolerated this significant reduction of cardiac output well. We have demonstrated that ICG can be used to track the haemodynamic changes caused by PP in children, and suggest that this type of monitoring is useful in this group of age during laparoscopy.

Adolescent↗
PubMed2001

Mechanisms of respiratory sinus arrhythmia in patients with mild heart failure.

The high-frequency (HF) component of the heart rate variability (HRV) is regarded as an index of cardiac vagal responsiveness. However, when vagal tone is decreased, nonneural mechanisms could account for a significant proportion of the HF component. To test this hypothesis, we examined the HRV spectral power in 20 patients with mild chronic heart failure (CHF) and 11 controls before and during ganglion blockade with trimethaphan camsylate (3-6 mg/min iv). A small HF component was still present during ganglion blockade, and its amplitude did not differ between CHF patients and controls. The average contribution of nonneural oscillations to the HF component was 15% (range 1-77%) in patients with CHF and 3% (range 0. 7-30%) in healthy controls (P < 0.005). During controlled breathing at 0.16 Hz, however, it decreased to 1% (range 0.2-13%) in healthy controls and 5% (range 1-44%) in CHF patients. Our results indicate that the HF component can significantly overestimate cardiac vagal responsiveness in patients with mild CHF. This bias is improved by controlled breathing, since this maneuver increases the vagal contribution to HF without affecting its nonneural component.

Arrhythmia, Sinus↗
PubMed2001

Determinants of spontaneous baroreflex sensitivity in a healthy working population.

Baroreflex sensitivity (BRS) by the spontaneous sequence technique has been widely used as a cardiac autonomic index for a variety of pathological conditions. However, little information is available on determinants of the variability of spontaneous BRS and on age-related reference values of this measurement in a healthy population. We evaluated BRS as the slope of spontaneous changes in systolic blood pressure (BP) and pulse interval from 10 minutes BP (Finapres) and ECG recordings in 1134 healthy volunteers 18 to 60 years of age. Measurement of BRS could be obtained in 90% of subjects. Those with unmeasurable spontaneous BRS had a slightly lower heart rate but were otherwise not different from the rest of the population. BRS was inversely related to age (lnBRS, 3.24-0.03xage; r(2)=0.23; P:<0.0001) in both genders. In addition, univariate analysis revealed a significant inverse correlation between BRS and heart rate, body mass index, and BP. Sedentary lifestyle and regular alcohol consumption were also associated with lower BRS. However, only age, heart rate, systolic and diastolic BP, body mass index, smoking, and gender were independent predictors of BRS in a multivariate model, accounting for 47% of the variance of BRS. The present study provides reference values for spontaneous BRS in a healthy white population. Only approximately half of the variability of BRS could be explained by anthropometric variables and common risk factors, which suggests that a significant proportion of interindividual differences may reflect genetic heterogeneity.

Adolescent↗
PubMed2000

Sympathetic denervation of the upper limb improves forearm exercise performance and skeletal muscle bioenergetics.

BACKGROUND: Sympathetic activation may limit exercise performance by restraining muscle blood flow or by negatively affecting skeletal muscle metabolic behavior. To test this hypothesis, we studied the effect of thoracoscopic sympathetic trunkotomy (TST) on forearm exercise duration, blood flow, and muscle bioenergetics in 13 patients with idiopathic palmar hyperhidrosis. METHODS AND RESULTS: Heart rate and beat-by-beat mean arterial pressure were recorded at rest and during right and left rhythmic handgrip before and 4 to 7 weeks after right TST. Forearm blood flow was measured bilaterally at rest and on the right during exercise. Right forearm muscle phosphocreatine content and intracellular pH were assessed by (31)phosphorus magnetic resonance spectroscopy. After right TST, exercise duration increased from 8.9+/-1.4 to 13.4+/-1.8 minutes (P<0.0001) with the right forearm and from 5.7+/-0.4 to 7.6+/-0.9 minutes (P<0.05) with the left (P<0.05 for the interaction between treatment and side). Right forearm blood flow at rest was 66% higher (P<0.01) after right TST, but this difference decreased as the exercise progressed. After right TST, a significant reduction occurred in muscle acidification and phosphocreatine depletion during ipsilateral forearm exercise. This was associated with a significantly reduced mean arterial pressure response to right handgrip, whereas the pressor response to left handgrip did not change. CONCLUSIONS: Sympathetic denervation of the upper limb significantly improves forearm skeletal muscle bioenergetics and exercise performance in patients with idiopathic palmar hyperhidrosis.

Adult↗
PubMed1999

Effect of exogenous nitric oxide on baroreflex function in humans.

Nitric oxide (NO) donors inhibit sympathetic neurotransmission and baroreceptor activity and can directly stimulate heart rate (HR) in vitro. To assess whether exogenous NO affects cardiovascular autonomic control in humans, we tested the baroreceptor-cardiac reflex [baroreflex sensitivity (BRS)] and the arterial blood pressure (BP) and HR variability during an infusion of the NO donor sodium nitroprusside (SNP, 2 micrograms . kg(-1). min(-1)) or 5% glucose in 16 healthy subjects. The hypotensive action of SNP was prevented by phenylephrine (PE, 0.9 +/- 0.15 micrograms . kg(-1). min(-1)). The SNP + PE infusion did not affect BRS or HR variability, but it caused a significant reduction in the diastolic and systolic BP low-frequency power. In addition, SNP + PE caused a sustained 12% increase in HR in the absence of changes in brachial and aortic BP. In conclusion, SNP had no effect on the cardiac-vagal limb of the baroreflex in humans but caused a substantial reduction in BP low-frequency power consistent with a decreased baroreflex/sympathetic control of peripheral resistance. The increase in HR in the absence of baroreceptor downloading confirms our previous finding of a direct positive chronotropic effect of NO donors.

Adult↗
PubMed1999

Hormone replacement therapy and ischaemic heart disease among postmenopausal women.

The beneficial effect of hormone replacement treatment (HRT) on osteoporosis and menopausal symptoms has been well documented in randomised trials, but the impact of oestrogen-mediated metabolic changes on the risk of ischaemic heart disease (IHD) is still debated. Randomised studies have shown that HRT increases levels of high-density lipoprotein cholesterol while causing a reduction in the levels of low-density lipoprotein cholesterol, serum fibrinogen, plasminogen activator inhibitor and homocysteine. In addition, HRT increases insulin sensitivity in both normoglycaemic and diabetic women. Unlike oral contraceptives, HRT has not been associated with an increase in arterial blood pressure, whereas a small increase in the risk of breast cancer and of venous thromboembolism appears to occur with both treatments. Interestingly, some data suggest that oestrogen preparations may have different effects on lipids. For instance, the beneficial effect on cholesterol metabolism observed with oral conjugated oestrogen does not occur with transdermal oestradiol, suggesting that the first-pass effect through the portal circulation may be necessary to achieve the full metabolic effect of oestrogen treatment. Nevertheless, although a wealth of observational studies show that HRT is associated with a significant reduction in morbidity and mortality from IHD, the only randomised data available to date do not support these findings in postmenopausal women with established coronary artery disease.

Drug Therapy, Combination↗
PubMed1998

[Cardiovascular autonomic regulation following orthoptic heart transplantation].

Numerous recent observations have indicated autonomic reinnervation of transplanted human hearts. In order to assess autonomic regulation 5 patients were studied 1 to 5 years following cardiac transplantation. A series of tests were performed, including blood pressure and ECG recordings on rest, during 15/min patterned breathing, isometric handgrip exercise, and Valsalva manoeuvre. The time domain indices (SDRR, pNN50, rMSSD) and the frequency domain indices of heart rate variability were also studied. Among the five patients under study only one exhibited features compatible with both sympathetic and parasympathetic reinnervation. Traditional autonomic reflex tests and the analysis of time and frequency domain indices of HRV serve as simple tool in primary assessment of cardiac reinnervation.

Adult↗
PubMed1998

Coronary artery-descending aorta fistula as an unusual collateral in a patient with postductal coarctation.

We report on the case of a 45-year-old man with recurrent syncope and angina with shortness of breath on exertion. Invasive and noninvasive diagnostic methods revealed severely stenosed bicuspid aortic valve, postductal coarctation of the aorta, and a coronary artery-descending aorta fistula. After surgical correction of the coarctation, ligation of the fistula, and aortic valve replacement, the patient's symptoms resolved.

Aorta, Thoracic↗
PubMed1998

Lipophilic versus hydrophilic beta(1) blockers and the cardiac sympatho-vagal balance during stress and daily activity in patients after acute myocardial infarction.

OBJECTIVE: To compare the effects of a lipophilic and a hydrophilic beta(1) blocker on cardiac sympatho-vagal balance during daytime activity and stress in patients four to six weeks after myocardial infarction. DESIGN: Randomised, double blind, crossover study comparing the effect of atenolol (50 mg once daily) with metoprolol CR (100 mg once daily) with treatment periods of four weeks. SETTING: Large teaching hospital. PATIENTS: 50 patients (45 male, 5 female, age range 40 to 75 years), four to six weeks after an acute myocardial infarction. METHODS: At the end of each treatment period the 24 hour heart rate variability, heart rate variability power spectra during head up tilt and mental stress, baroreflex sensitivity, and exercise performance were evaluated. RESULTS: During daytime activity and during orthostatic and mental stress, both heart rate and the ratio between the low and high frequency spectral components of the heart rate variability were significantly lower with atenolol. Conversely, there was no difference between treatments in baroreflex sensitivity and resting plasma catecholamines. Exercise duration and peak oxygen consumption did not differ between treatments, but the heart rate during submaximal and peak exercise was significantly lower with atenolol. CONCLUSIONS: At the doses used in this study, atenolol achieved greater beta(1) adrenergic blockade than metoprolol CR and this was associated with significant inhibition of vagal withdrawal during stress. This suggests that peripheral blockade of beta(1) adrenergic receptors may be more important than central blockade in preventing stress induced vagal withdrawal in patients after myocardial infarction.

Adrenergic beta-Antagonists↗
PubMed1997

[Defecation syncope following pacemaker implantation].

A case of syncope is reported, where hemodynamic responses compatible with pacemaker syndrome occurred during defecation. A 73 year old female received a VVI pacemaker for complete heart block. Subsequently she sustained repeated episodes of defecation syncope. Hemodynamic investigations revealed an abnormal blood pressure drop occurring at the overshoot phase of the Valsalva maneuver in association with alternation of sinus and pacemaker rhythm. This modified Valsalva response in the presence of contributing factors, such as hypovolemia and nitroglycerin therapy manifested as defecation syncope. The abnormal condition was treated by eliminating the contributing factors, and by programming a low pacemaker frequency, thus precluding sinus-pacemaker alterations.

Aged↗