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J Freitas

Publications and source records attributed to J Freitas.

At least 55 records · Page 3Linked to original sources
PubMed1995

[The spectral analysis of heart rate variability. A comparative study between nonparametric and parametric spectral analysis in short series].

OBJECTIVE: to compare parametric (AR) and non parametric (FFT) spectral analysis results obtained in 512 beats series. INTERVENTIONS: 104 healthy subjects with normal physical examination and electrocardiogram were studied. The Ecg was recorded at rest, with controlled breathing at 15 cycles/min., and sampled at 300 Hz. The spectral VLF, LF and HF were calculated with FFT algorithm. For the same series, an auto-regressive analysis (AR) with optimized choice of the order of the model (AIC criterion) have been computed, VLF, LF and HF components were identified by AR spectral decomposition. RESULTS: In both groups, athletes and sedentary, there were no statistically differences between VLF, LF, HF and LF/HF spectral indices computed by the two methods. CONCLUSION: the results suggest that with controlled breathing it does not seems to exist any advantage in the use of AR spectral analysis to compute spectral components of heart rate variability, which is much more laborious that fixed bands non parametric FFT analysis.

Adolescent↗
PubMed1994

Esophageal motility disorders in patients with Sjögren's syndrome.

Esophageal motility was studied in 21 patients with Sjögren's syndrome, and in 25 normal volunteers, in order to record the prevalence and type of esophageal motor abnormalities. Esophageal motor abnormalities were detected in seven of the 21 patients (33.3%). These esophageal abnormalities did not correlate with the presence of dysphagia, the extraglandular involvement, or the presence of autoantibodies.

Deglutition Disorders↗
PubMed1994

Odontoid fractures. Review of 150 cases and practical application for treatment.

A total of 150 odontoid fractures was treated over a 12-year period, 43 by anterior screw fixation. The rate of pseudarthrosis dropped from 20% to 5% in type II unstable fractures. Thus, anterior screw fixation seems to be safe and efficient, and may be more widely used to treat all type II and some type III fractures. Odontoid pseudarthrosis is usually tolerated quite well and therefore requires no correction. If necessary, anterior grafting with fixation can be proposed as an alternative for posterior fusion.

Bone Screws↗
PubMed1994

Heart rate variability in 24-hour Holter recordings. Comparative study between short- and long-term time- and frequency-domain analyses.

Mean hourly parameters obtained from all beats (long series) were compared with those obtained from a sample of 512 beats extracted each hour (short series) in nine presumably normal subjects. For both the short and long series, the spectral components, very low frequency, (VLF), low frequency (LF), and high frequency (HF), and time-domain indices (such as the Ewing statistic [PNN50] and RR standard deviation [SD-RR]), have been estimated. The spectral components LF and HF, estimated from the short and long series, were not significantly different, whereas significant differences were found between VLF, SD--RR, and PNN50. In both the short and long series, a strong correlation was found between LF and SD-RR and between HF and PNN50. The results suggest that, over a period of 24 hours, hourly LF and HF spectral components can be obtained using a single series of 512 beats every hour, with a great advantage over the evaluation of the mean hourly parameters. This method would be particularly useful in the study of circadian heart rate spectral analysis in Holter recordings with multiple artifacts or ectopic beats, and in general, when analysis of the entire 24-hour series is not feasible.

Adult↗
PubMed1994

[The ambulatory recording of the long-term electrocardiogram].

In the past 5 years, a new approach was developed to evaluate the patient with sporadic symptoms as is the patient with syncope--the long-term ambulatory loop electrocardiogram monitoring. This method allow to assure the heart rate and rhythm at the moment of the symptoms hardly to be able with the other diagnostic tools disposable. The long-term ambulatory loop electrocardiogram monitoring was not to replace the actual tools, but complement them. Newer devices are smaller and too light, and have the ability of registry some minutes before and after the symptom. In the near future, the devices will be able to detected and store arrhythmias and to possess an easy and accessible management. With continued and profitable work that has been done in this area, a large proportion of patients with the diagnosis of "syncope of unknown etiology" can have a diagnostic and specify therapeutic and we will be able to assert with more strictness if the symptoms related by the patient are or not of cardiovascular origin.

Arrhythmias, Cardiac↗
PubMed1994

[Sudden death in athletes].

Identifying all athletes at risk for exercise-related sudden death is difficult because systematic reliable screening is expensive. Nevertheless, if a perfect screening method existed, an appreciable number of athletes at increase risk for sudden death would not be identified. We think that a careful history designed to identify symptomatic athletes and a rigorous family history of congenital heart disease may be the most practical screening method.

Adolescent↗
PubMed1994

[Syncope: how to deal with it?].

Syncope is a frequent symptom, with an expensive protocol of difficult evaluation in face of its diverse causes. The authors describe the proper use of the tests available, particularly the tilt test, and conclude that nowadays only few syncopal episodes would remain unexplained.

Diagnosis, Differential↗
PubMed1993

[Malignant vasovagal syncope: a case of prolonged asystole induced by the "tilt" test and aggravated by therapy with a beta blocker (a clinical case and diagnostic, physiopathologic and therapeutic review)].

The authors describe a case of a middle-age male with recurrent syncope, in whom the tilt test was useful in the diagnosis and therapeutic evaluation. Malignant criteria of vasovagal syncope were established and the beta blocking worsening effect was documented, in spite of the general agreement of the first choice drug.

Adult↗
PubMed1993

Spectral analysis of heart rate variability in athletes.

The objectives of the study were to characterize power spectrum pattern of the heart rate variability and assessment of the relative contributions of sympathetic and parasympathetic cardiac nervous system control in athletes. Thirty-three male athletes, swimming (1), canoeing (10), cycling (6), athletics (4), football (3), roller-skating (2) and volleyball (7) aged 23.4 +/- 5.5 years, with a mean athletic level of 18 hours/week (8-45) and 33 sedentary healthy control subjects were included. Ecg signals were recorded after a period of 15 minutes in supine rest with controlled breathing at 15 cycles/min. Signal acquisition was done at 300 samples/sec. From 512 consecutive heart beats, we calculated mean average, standard deviation, maximum and minimum R-R intervals and, after computing the fast Fourier transform, total spectrum power, low frequency (LF), high frequency (HF) components and its ratio (LF/HF). The average R-R interval was 987.7 +/- 168.8 ms and 762.7 +/- 125.3 ms, the variance was 5.44 and 2.51 ms2 and ratio of R-R interval maximum/minimum (E/I ratio) 1.53 +/- 0.16 and 1.41 +/- 0.16, respectively for athletes and control group. Differences between groups were significant (p < 0.01) for all parameters, with higher variability in the athletes. Both spectral bands (LF and HF) had higher power in athletes (LF = 925 +/- 920 and HF = 2258 +/- 2349 ms2) than in the control group (LF = 442 +/- 446 and HF = 1179 +/- 1542 ms2) (p < 0.01). There were no significant differences for LF/HF ratio, or normalized LF (LF%) or normalized HF (HF%) between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Study of the autonomous nervous system with heart rate spectral analysis in acute myocardial infarction].

OBJECTIVES: Characterize power spectrum pattern of heart rate variability (HRV) and assessment of relative cardiac nervous system in patients with acute myocardial interaction of sympathetic and parasympathetic infarction. We also compared the spectral power with some known prognostic risk variables. STUDY DESIGN: Study of patients with acute myocardial infarction (AMI) and sedentary healthy subjects sex matched. SUBJECT AND METHODS: 19 postinfarction patients aged 55.7 +/- 10.5 years and 19 healthy subjects controls aged 53.9 +/- 11.0. ECG signals were recorded after 15 minutes of supine rest with controlled breathing at 15 cycles/min. Signal acquisition was done at 300 samples/sec. From 512 consecutive sinus beats, we calculated the average, standard deviation, maximum and minimum values and rate between the longest and shortest R-R interval (E/I). We also calculated, after computing the fast Fourier transform, the total spectrum power, low frequency component (LF, from 0.01 to 0.15 Hz), high frequency component (HF, from 0.15 to 0.50 Hz) and its ratio (LF/HF). Thereafter, we correlated these results with radionuclide ejection fraction, duration of treadmill test, Holter ventricular premature complex and localization of infarction. RESULTS: The average R-R interval was 757.9 +/- 116.3 and 850.9 +/- 133.9 msec (p less than 0.05), the R-R corrected standard deviation was 15.3 +/- 6.0 and 38.2 +/- 8.5 msec (p less than 0.001) and ratio E/I was 1.13 +/- 0.06 and 1.32 +/- 0.09 (p less than 0.001) in AMI and control group, respectively. In AMI group, low frequency spectral band was very decreased (LF = 0.03 +/- 0.02 sec2) and high frequency was virtually absent (HF = 0.01 +/- 0.01 sec2) compared with control group (LF = 0.13 +/- 0.06 and HF = 0.14 +/- 0.15 sec2), p less than 0.001; ratio LF/HF was increased in AMI group. There were no significant differences between groups for normalized LF (LF%) and HF (HF%). CONCLUSIONS: These results showed that spectral pattern in AMI patients had very low LF and HF power density. Decreased HRV in that group was mainly due to diminished parasympathetic influence in cardiac regulation; nevertheless ratio LF/HF was increased which represents an imbalance of sympatho-vagal activity with predominance of sympathetic tone. We found poor correlation between frequency domain indices and other risk variable; best correlation was between total spectral power and radionuclide ejection fraction (r = 0.642, p less than 0.01), which could express independent prognostic value in AMI patients risk stratification.

Autonomic Nervous System↗
PubMed1991

[Spectrum analysis of the variability of heart rate in athletes].

OBJECTIVES: Characterize power spectrum pattern of the heart rate variability and assessment of the relative contributions of sympathetic and parasympathetic cardiac nervous system control in athletes. STUDY DESIGN: Prospective study of athletes and sedentary healthy control group sex and age matched. SUBJECT AND METHODS: 8 athletes, 3 female and 5 male, swimming (4), canoeing (2) and cycling (2), aged 17.4 +/- 3.6 years, and 8 sedentary healthy controls. ECG signals were recorded after a period of 15 minutes in supine rest with controlled breathing at 15 cycles/min. Signal acquisition was done at 300 samples/sec. From 512 consecutive heart beats, we calculated the average, the standard deviation, the maximum and the minimum values and the rate between the longest and the shortest R-R interval (E/I). We also calculated, after computing the fast Fourier transform, the total spectrum power, the low frequency component (LF, from 0.01 to 0.15 Hz) and the high frequency component (HF, greater than 0.15 Hz) and its ratio (LF/HF). RESULTS: The average R-R interval was 921 +/- 154.2 msecs and 673.2 +/- 98 msecs, the standard deviation was 72.5 and 29.4 msecs and the ratio E/I 1.63 +/- 0.14 and 1.28 +/- 0.08, respectively for athletes and control group. Differences between groups were significant (p less than 0.01) for all parameters, with higher variability in the athletes. Both spectral bands (LF and HF) and higher power in athletes (LF = 0.54 +/- 0.23 and HF = 0.76 +/- 0.14) than in the control group (LF = 0.14 +/- 0.10 and HF = 0.18 +/- 0.15) (p less than 0.001). There were no significant differences for LF/HF ratio, or normalized LF (LF%) or normalized HF (HF%) between groups. CONCLUSIONS: The present results indicates higher power of both spectral bands (LF and HF) and higher amplitude of the respective peaks in athletes when compared with healthy sedentary, with a clear predominance of the HF band in the total spectral power density, which suggest that the higher heart rate variability observed in athletes reveals the predominance of parasympathetic activity, without reduction of the sympathetic tone.

Adolescent↗
PubMed1991

[High resolution electrocardiogram and late potential monitoring].

The signal-averaged ECG became an important noninvasive method for identifying life-threatening ventricular arrhythmias. It is most accurate in patients with coronary artery disease and can be helpful in predicting whether a patient with an unexplained syncope or nonsustained VT is at risk of developing sustained ventricular tachycardia or not. A patient with an entirely normal signal-averaged ECG is at very low risk of sustained VT. In contrast, an abnormal signal-averaged ECG should raise suspicion about VT, and prompt further studies, including electrophysiological testing. Signal-averaged ECG can also be used repeatedly with acceptable reproducibility. Technological advances and improvements in the frequency analysis of the averaged signal may increase the predictive accuracy of the technique and consequently enhance its clinical applications.

Electrocardiography↗
PubMed1988

The measurement of D,L-2,3-butanediol in controls and patients with alcoholic cirrhosis.

Plasma D,L-2,3-butanediol was measured in 53 controls and 50 patients with alcoholic cirrhosis, none of whom had measurable amounts of blood ethanol. Thirteen of 50 samples from patients with alcoholic cirrhosis had measurable D,L-2,3-butanediol. (range less than 5-154 microM). In one patient with alcoholic cirrhosis who had been abstinent from ethanol for over 5 years plasma levels of D,L-2,3-butanediol ranged between 154 and 211 microM over a one-year period. Only one of the 53 control subjects had detectable levels of D,L-2,3-butanediol. Although it has previously been reported that 2,3-butanediol is present in alcoholics consuming distilled spirits (Rutstein et al. (1983) Lancet ii, 534), this is the first report of the persistent presence of these compounds in alcoholics in the absence of ethanol. Clearly in abstinent alcoholics the presence of 2,3-butanediol is not due to the ingestion of undistilled spirits nor is it likely to arise directly from the metabolic products of ethanol. The presence of D,L-2,3-butanediol in patients with alcoholic cirrhosis and its absence in control subjects suggests that this compound may be a marker of some forms for alcoholism.

Biomarkers↗
PubMed1983

Cholescintigraphy in cholecystic cancer.

Two case reports of nonvisualization of the gallbladder by hepatobiliary scintigraphy in patients with carcinoma of the gallbladder are described. A hypothesis regarding the pathogenesis of gallbladder nonvisualization in cholecystic cancer is offered. The possible clinical utility of hepatobiliary scintigraphy in these patients is discussed.

Adenocarcinoma↗
PubMed1983

Value of bowel preparation in adrenocortical scintigraphy with NP-59.

The use of radiolabeled cholesterol derivatives for functional imaging of the adrenal cortex may be rendered inaccurate or impossible because of the excretion of activity by the liver and its subsequent appearance in the colon. A simple bowel preparation (bisacodyl 5 or 10 mg nightly) significantly reduced bowel background activity during 6 beta-[I-131]iodomethyl-19-norcholesterol (NP-59) adrenal cortical scintigraphy. Activity interfering with image interpretability was present less frequently in patients taking bisacodyl: three days after injection 22% compared with 59%; five days after injection 23% compared with 35%. As bisacodyl acts only on the colon and does not disturb the enterohepatic circulation of cholesterol or bile acids, it is ideal for use with a tracer of cholesterol metabolism.

19-Iodocholesterol↗