Heart rate variability in patients with tetralogy of Fallot

Background

Heart rate variability (HRV) can be used to evaluate cardiac autonomic nervous system activity. In the adult population decreased HRV has been associated with increased mortality in patients with cardiac disease, however, application of HRV in patients with congenital heart disease is not well established.

Purpose

To describe and compare HRV parameters obtained by clinical Holter monitoring in patients with Tetralogy of Fallot (TOF) and healthy controls and to evaluate its association with different clinical outcomes.

Methods

Data from 489 patients were obtained; 150 had undergone repair of TOF and 339 were healthy controls. Using propensity score matching (PSM), 149 TOF patients were matched for sex, age at Holter,body mass index, use of beta-blockers, and ectopic beats with 149 healthy patients. Minimum, maximum, average heart rate and time domain HRV parameters (ASDNN5, SDANN5, SDNN, RMSSD, PNN50) and clinical outcomes (arrhythmias, hospital admission for cardiac disease, and functional class) were compared between groups using simple and multiple linear regression models as well as logistic regression analysis.

Results

No significantdifference was found in time domain HRV parameters between the two groups, though average (−7.0253, p=0.000) and maximum (−15.8585, p=0.000) heart rate values were significantly lower in patients with TOF compare with controls. Logistic regression analysis showed an association between maximum heart rate values and the development of arrhythmias (OR=0.9817, p=0.013), as well as the functional class (OR=0.9706, p=0.03).

Conclusion

Average and maximum heart rates are significantly lower in patients with repaired TOF compared to the control population. Time domain HRV parameters were not associated with clinical outcomes in patients with TOF when compared to healthy controls. Further investigation assessing frequency domain parameters may provide further insight.

Funding Acknowledgement

Type of funding sources: None.

A practical radial basis function equalizer

A radial basis function (RBF) equalizer design process has been developed in which the number of basis function centers used is substantially fewer than conventionally required. The reduction of centers is accomplished in two-steps. First an algorithm is used to select a reduced set of centers that lie close to the decision boundary. Then the centers in this reduced set are grouped, and an average position is chosen to represent each group. Channel order and delay, which are determining factors in setting the initial number of centers, are estimated from regression analysis. In simulation studies, an RBF equalizer with more than 2000-to-1 reduction in centers performed as well as the RBF equalizer without reduction in centers, and better than a conventional linear equalizer.

Patterning the early zebrafish by the opposing actions of bozozok and vox/vent

Fish and frog embryos are patterned along the dorsal-ventral axis during the gastrula stage by opposing gradients of Bmps and Bmp inhibitory proteins. Three transcriptional repressors with partially overlapping expression domains have been proposed to be important mediators of Bmp function in Xenopus. We find that two related factors are expressed in the early zebrafish embryo. Although these factors are considerably divergent from the related Xenopus genes, they are expressed in domains similar to those of their Xenopus relatives throughout embryogenesis. Both of the zebrafish genes, which we have named vox and vent, are potent ventralizing factors in both zebrafish and Xenopus embryos. Using mutants in the Bmp pathway, we find that there are Bmp-dependent and Bmp-independent domains of vox expression, whereas vent is mostly dependent upon Bmp signaling. We show that ectopic vox or vent negatively regulates expression of the early dorsal gene bozozok (boz) and that ectopic boz eliminates vox and vent expression. Moreover, the normal exclusion of vox and vent from the organizer region is lost in boz mutant embryos. Our results show that boz and vox/vent are mutually antagonistic and indicate that the early establishment of the size of the organizer domain is dependent on an interplay between these early expressed transcriptional repressors.

Evidence that the slowing caused by acute hypoxia is modality dependent

BACKGROUND

AFM (Additive Factors Method) experiments conducted with visual stimuli suggest that the slowing produced by acute hypoxia is located at the earliest preprocessing stage of information processing and that later stages are unaffected (the bottleneck hypothesis).

METHODS

To determine the contribution of degraded visual functioning to slowing, we bypassed this modality and measured reaction time in an AFM paradigm to auditory (Experiment 1) and kinesthetic (Experiment 2) stimuli. In both experiments hypoxia was induced with low oxygen mixtures and arterial blood oxygen saturation (SaO2) was controlled at 65%. Task difficulty was manipulated in Experiment 1 with tones that differed in intensity and in Experiment 2 with lifted cylinders that differed in weight.

RESULTS

The results for Experiment 1 showed an interaction between task difficulty and hypoxia, indicating slowing of the preprocessing stage. Slowing was not found in Experiment 2. The absence of slowing in Experiment 2 is surprising and indicates that slowing may be confined to vision and audition and may not involve later, more central, stages. We discuss the need to measure cerebral oxygenation in order to understand the sharp differences between the the bottleneck hypothesis, developed by controlling SaO2, and the more traditional behavioral model which postulates multiple cognitive deficits.

Painless acute aortic dissection presenting as left lower extremity numbness

Acute aortic dissection may have variable presentations, making the diagnosis clinically challenging. Acute neurologic syndromes secondary to dissection of the aorta are uncommon. However, including aortic dissection in the differential diagnosis is imperative. This report describes the first reported case of an acute thoracic aortic dissection presenting with the chief complaint of unilateral lower extremity numbness. Peripheral ischemic neuropathy as the result of vascular occlusion is uncommon. The pathophysiology and clinical manifestations of ischemic neuropathies in the setting of acute aortic dissection are discussed.

Tension hydrothorax due to ventriculopleural shunting

Tension hydrothorax is rare, with few cases reported in the literature dating back to the late 1960s. We report a case of tension hydrothorax in a patient with a ventriculopleural shunt who improved dramatically after thoracentesis. The discussion includes a brief review of ventriculopleural shunts and pleural physiology.

Service utilization and costs of care for severely mentally ill clients in an intensive case management program

OBJECTIVE

The study evaluated the effects of an intensive case management model on clients' use of inpatient and outpatient psychiatric care and on the costs of care.

METHODS

Ninety clients of a county mental health system who were frequent users of inpatient services were randomly assigned to either an intensive case management group, a traditional case management group, or a control group who received no particular services. Outcome variables measured over a two-year period were number of units used by clients and costs of inpatient care in county and private facilities and various types of outpatient care, including day treatment and use of an emergency psychiatric unit.

RESULTS

Clients who received intensive case management had fewer inpatient days and reduced overall costs for mental health services.

CONCLUSIONS

Assertive outreach and intensive case management can reduce hospitalizations of clients who are frequent users of inpatient care and can reduce overall mental health care costs. Mental health consumers employed as case management aides can play an important role in the delivery of mental health services, particularly with frequent users of inpatient care.

Inter-rater reliability of a paediatric outcome measure in Nepal

The Hospital and Rehabilitation Centre for Disabled Children (HRDC) in Nepal identified the need to evaluate their in-hospital and community programmes. An instrument was developed to provide information regarding the functional level of the children treated by the HRDC as well as to provide information regarding care-givers' attitudes towards disability. Inter-rater reliability of the measure was tested in three regions of Nepal with 49 children. Six HRDC field workers travelled in pairs to the childrens' homes and alternated in roles as test administrator and observer. Correlations between the scores documented by the administrator and observer were used to estimate inter-rater reliability. Inter-rater reliability coefficients, calculated using a weighted kappa statistic, varied from 0.60 to 1.0. We conclude that the instrument demonstrated an acceptable level of inter-rater reliability in the field setting. Future studies to measure construct and concurrent validity, test-retest reliability and responsiveness of the instrument are recommended as well as testing the instrument in different cultures.

Electron migration along 5-bromouracil-substituted DNA irradiated in solution and in cells

Solvated electrons generated in aqueous solution after exposure to ionizing radiation can be scavenged by DNA and then transferred along the DNA molecule. This mechanism of charge transfer provides an opportunity for radiation damage to be targeted to certain regions in the DNA molecule and is a mechanism by which single-strand breaks contribute to locally multiply damaged sites to enhance cell lethality. Experiments were performed in which different amounts of 5-bromouracil (5-BrU) were substituted for thymine in Escherichia coli DNA. The amount of bromide released was assayed after quantitative reaction of radiation-induced solvated electrons with 5-BrU in DNA samples irradiated in solution and irradiated in the cellular environment. By varying the amount of 5-BrU incorporated in the DNA, the average distance between 5-BrU molecules was systematically changed and, because the number of 5-BrU/electron reactions was monitored by the amount of bromine released, the maximum average electron migration distance along the 5-BrU DNA could be estimated. Using this approach, the maximum average electron migration distance in aqueous solutions of 5-BrU DNA was about 6.5 to 10 base distances in nonhybrid 5-BrU DNA (assuming only intrastrand migration). Similar methods revealed charge migration in 5-BrU DNA incorporated into E. coli, and the maximum average migration distance was about 5 to 6 base distances (assuming only intrastrand migration). Only 11-16% of the electrons produced during radiolysis were scavenged by 5-BrU DNA in aqueous solution, and only 1% resulted in the release of bromide from 5-BrU-DNA inside E. coli.

Electrocardiogram of pure left ventricular hypertrophy and its differentiation from lateral ischaemia

In routine reporting of electrocardiograms, a frequent problem is presented by the presence of repolarisation abnormalities (ST depression and/or T wave inversion) in the lateral leads without the accepted QRS voltage criterion of left ventricular hypertrophy. To help resolve this problem, the electrocardiograms of 41 patients with severe aortic stenosis who had no evidence of coronary disease were compared with the electrocardiograms of 20 patients with lateral myocardial infarction who had no clinical evidence of left ventricular hypertrophy. Nine of the patients with aortic stenosis were found to show repolarisation abnormalities in the lateral leads without the standard voltage criterion of left ventricular hypertrophy. The repolarisation pattern of aortic stenosis could frequently be distinguished from that of coronary disease by the presence of one or more of the following five features: depression of the J point, asymmetry of the T wave with rapid return to the baseline, terminal positivity of the T wave ("over-shoot"), T inversion in V6 greater than 3 mm, and T inversion greater in V6 than in V4.

Raised plasma oestradiol and oestrone levels in young survivors of myocardial infarction

Of 35 male survivors of myocardial infarction, aged 24-48 years, 34 had higher plasma-oestradiol levels than age-matched controls. 29 of the 35 had higher oestrone levels than controls.