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Biomedical subjects

E C Barbosa

Publications and source records attributed to E C Barbosa.

13 recordsLinked to original sources
PubMed2002

Clinical assessment of the effect of digital filtering on the detection of ventricular late potentials.

Ventricular late potentials are low-amplitude signals originating from damaged myocardium and detected on the body surface by ECG filtering and averaging. Digital filters present in commercial equipment may interfere with the ability of arrhythmia stratification. We compared 40-Hz BiSpec (BI) and classical 40- to 250-Hz band-pass Butterworth bidirectional (BD) filters in terms of impact on time domain variables and diagnostic properties. In a transverse retrospective age-adjusted case-control study, 221 subjects with sinus rhythm without bundle branch block were divided into three groups after signal-averaged ECG acquisition: GI (N = 40), clinically normal controls, GII (N = 158), subjects with coronary heart disease without sustained monomorphic ventricular tachycardia (SMVT), and GIII (N = 23), subjects with heart disease and documented SMVT. Conventional variables analyzed from vector magnitude data after averaging to 0.3 micro V final noise were obtained by application of each filter to the averaged signal, and evaluated in pairs by numerical comparison and by diagnostic agreement assessment, using conventional and optimized thresholds of normality. Significant differences were found between BI and BD variables in all groups, with diagnostic results showing significant disagreement between both filters [kappa value of 0.61 (P<0.05) for GII and 0.31 for GIII (P = NS)]. Sensitivity for SMVT was lower with BI than with BD (65.2 vs 91.3%, respectively, P<0.05). Filters provided significantly different numerical and diagnostic results and the BI filter showed only limited clinical application to risk stratification of ventricular arrhythmia.

Age Distribution↗
PubMed2001

The frequency analysis of signal-averaged ECG of P wave as predictor of efficacy of class III antiarrhythmic drugs to maintain sinus rhythm in recurrent idiopathic atrial fibrillation.

BACKGROUND: The use of class III antiarrhythmic drugs (ADIII) has been considered a good predictor of sinus rhythm in patients post-cardioversion from atrial fibrillation (AF). Several studies using frequency domain analysis of signal-averaged ECG (FDSAECG) of the P wave were able to identify patients at risk for AF. The aim of this study was to assess the FDSAECG in predicting recurrence of idiopathic persistent AF (IPAF) in patients under ADIII therapy. METHODS: In 33 patients with two or more previous symptomatic episodes of IPAF, despite classes I and II therapy, the FDSAECG of the P wave was performed during sinus rhythm and free-drug state. The parameters were the mean and standard deviation of the frequency intersegmentar spectral correlation and the standard deviation of the signal frequency edge track. During the follow-up of 30 +/- 18 months, all patients received either amiodarone or sotalol. RESULTS: During the follow-up, the patients were divided into two groups: Group I-frequent recurrence (>or= three events/year; 16 patients), and Group II-infrequent recurrence (< three events/year; 17 patients). With appropriate cutoff points for each parameter analyzed, intense fragmented electrical activity defined by the presence of at least two abnormal criteria were observed in 13 of 16 patients group I and in 3 of 17 patients group II (P = 0.0003). Sensitivity, specificity, positive and negative predictive values for frequent recurrence were 81.3, 82.4, 81.3, and 82.4, respectively. CONCLUSIONS: The results suggested that FDSAECG analysis of the P wave accurately predicted patients whose ADIII therapy will be effective in maintaining the sinus rhythm without frequent recurrence of IPAF.

Aged↗
PubMed2001

Atrial activation during sinus rhythm in patients with rheumatic and non-rheumatic paroxysmal atrial fibrillation. Frequency-domain analysis using signal-averaged electrocardiography.

OBJECTIVE: Using P-wave signal-averaged electrocardiography, we assessed the patterns of atrial electrical activation in patients with idiopathic atrial fibrillation as compared with patterns in patients with atrial fibrillation associated with structural heart disease. METHODS: Eighty patients with recurrent paroxysmal atrial fibrillation were divided into 3 groups as follows: group I - 40 patients with atrial fibrillation associated with non-rheumatic heart disease; group II - 25 patients with rheumatic atrial fibrillation; and group III - 15 patients with idiopathic atrial fibrillation. All patients underwent P-wave signal-averaged electrocardiography for frequency-domain analysis using spectrotemporal mapping and statistical techniques for detecting and quantifying intraatrial conduction disturbances. RESULTS: We observed an important fragmentation in atrial electrical conduction in 27% of the patients in group I, 64% of the patients in group II, and 67% of the patients in group III (p=0.003). CONCLUSION: Idiopathic atrial fibrillation has important intraatrial conduction disturbances. These alterations are similar to those observed in individuals with rheumatic atrial fibrillation, suggesting the existence of some degree of structural involvement of the atrial myocardium that cannot be detected with conventional electrocardiography and echocardiography.

Adult↗
PubMed1998

[High resolution electrocardiogram in frequency domain. Use of statistical techniques of spectral correlation for identification of patients with sustained monomorphic ventricular tachycardia].

PURPOSE: To evaluate the diagnostic accuracy of monomorphic ventricular tachycardia (MVT), in patients with structural heart diseases and episodes of sustained MVT, using the signal-averaged ECG (SAECG) in the time (TD) and the frequency domain (FD) with statistical techniques of spectral correlation. METHODS: Twenty seven patients with at least one episode of sustained MVT, 30 patients with structural heart diseases and no evidence of ventricular arrhythmias and 80 subjects with no evidence of heart disease have been studied. SAECG was performed in all patients with the following parameters: duration of the filtered QRS, RMS 40 and LAS40 in TD and the mean and the standard deviation of both signal energy intersegmentar spectral correlation and energy frequency edge track in FD. RESULTS: The sensitivity(S) and positive predict value (PPV) of the SAECG in TD, in FD and combined analysis of both domains were: S = 59.3%, 63.0%, 81.5% and PPV = 80.0%, 81.0%, 84.6%, respectively. CONCLUSION: The combined analysis of SAECG in TD and in FD improves the diagnostic accuracy in patients with S sustained MVT.

Adult↗
PubMed1998

[Evaluation of fragmented potentials in right bundle branch block without structural myocardium abnormalities. Study made by signal-averaged electrocardiogram on time and frequency domain].

PURPOSE: To evaluate if the presence of right bundle branch block (RBBB), without structural myocardial abnormalities (SMA) can generate fragmented potentials (FP) and spectral turbulence on signal-averaged electrocardiogram (SAECG). METHODS: Twelve children with atrial septal defect (ASD) and incomplete right bundle branch block (IRBBB without SMA (group I) were compared to 17 children with post-operative tetralogy of Fallot (TF) with CRBBB, all with SMA, 5 with ventricular premature beats and 2 with sustained ventricular tachycardia (group II). All had SAECG on time (TD) and frequency domain (FD) with 5 variables analysed. RESULTS: All patients of group I had normal variables, in contrast with group II which presented abnormal variables suggesting FP and ST. CONCLUSION: In ASD without SMA, the isolated IRBBB did not generate FP and ST.

Bundle-Branch Block↗
PubMed1997

[Depressed electrical atrial activity in hypertrophic and dilated cardiomyopathies. An electrocardiographic, vectorcardiographic and echocardiographic study].

PURPOSE: To evaluate the "normal" or low-voltage P wave of the 12-leads conventional electrocardiogram (ECG), in patients with serious electric ventricular disturbances in hypertrophic (HC) and dilated (DC) cardiomyopathies. METHODS: Twenty cases of cardiomyopathies, 11 HC and 9 DC, ages ranging from 23 to 73 (x = 41) years have been studied. The analysis of the P wave was performed with ECG, amplified ECG at 1 mv = 20 mm and speed-paper at 50 mm/sec (ECG2), and the Frank-system vector-cardiogram (VCG). Voltage, delays and shapes of the P wave were evaluated by ECG2 and amplified VCG with gain at 1 mv = 160 mm. All electrical data were correlated with dimension of the left atrium (LA), dimension of left ventricular diastolic diameter (LVDD), dimension of left ventricular systolic diameter (LVSD), interventricular septal thickness (IST), posterior wall thickness ((PWT) and ejection fraction (EF) of the left ventricle of bidimensional echocardiogram (ECHO). RESULTS: Changes in morphologies and delays on the the P wave were best observed only on ECG2 and VCG. The mean voltage of P wave on ECG was 0.1 mv and the mean duration of the P loop on VCG was 133.7 msec in HC and 145.2 msec in DC, with mean terminal delay of 49.2 msec and 46.8 msec, respectively, due to slow atrial depolarization. CONCLUSION: In HC and DC with severe electric ventricular changes, the low-voltage and increased duration of P wave, are attributed to intraatrial-block due to structural changes of the atrial myocardium.

Adult↗
PubMed1992

[Hypocalcemia causing heart failure].

A 39-year-old female patient with refractory heart failure has been studied. On February, 1982 she was submitted to right lobar thyroidectomy for remotion of the left thyroid lobe. Following the surgery, she had signs of hypocalcemia and the diagnosis of secondary hypoparathyroidism and heart failure had been made. Seven months after she had acute pulmonary edema, cardiomegaly III (cardiothoracic index = 0.58) with predominant left atrial and left ventricular hypertrophy, which were confirmed by echocardiogram (ECO). The ECO also demonstrated low contractility of the left ventricle. The QT interval was increased on the electrocardiogram (QTc = 0.50 s), the calcium was 5.0 mg/dl with calciuria of 28 mg/day; phosphatemia was 4.8 mg/dl and phosphaturia of 214 mg/day. The level of thyroid hormones (T3 and T4) were in the normal ranges despite the TSH was increased in the beginning of the disease. She was first treated with digitalis, diuretic and vasodilator drugs, thyroid hormone and oral calcium. She had progressive hemodynamic improvement when higher doses of calcium were given with D3 vitamin. The most significant result of this treatment was reduction of the heart size that come back to normal. At the present time patient is treated with thyroid hormone, calcium and D3 vitamin only.

Acute Disease↗
PubMed1991

[Significance of prolonged PR interval in patients with His bundle branch block, bifascicular type].

PURPOSE: Evaluation of the prolonged PR interval and its predictive value for trifascicular block in individuals with bifascicular His bundle branch block. PATIENTS AND METHODS: 55 patients, 36 male and 19 female aged 57 + 15.8 years with bifascicular bundle branch block type have been studied. 11 cases had complete left bundle branch block and 44 cases had complete right bundle branch block with left anterior and superior division block. His bundle electrogram and atrial stimulation were performed in all patients. The atrial stimulation rate originating the Wenckebach phenomenon (SP) of the A-V conduction, and the A-H and H-V intervals were compared with the PR interval of the surface electrocardiogram. Patients were divided into three groups according to the PR interval: group I, Pr less than 200 ms, group II, PR between 190-280 ms and group III, PR greater than or equal to 280 ms. RESULTS: There was not linear correlation between the PR interval and WP in the three groups. There was a weak linear ascending correlation between the PR and A-H intervals in groups I and II (r + 0.59 and + + 0.43, respectively) and there was a descending correlation in the group III (r. - 0.64, P less than 0.05). In relation to the H-V interval there was not linear correlation with the PR interval in groups I and II, but there was a good ascending linear correlation in the group III (r 0.84, P less than 0.01). The incidence of prolonged A-H and H-V intervals increased as the PR interval was larger. CONCLUSION: The prolonged PR interval with bifascicular bundle branch block means, in the majority of cases, diffuse damage of the conduction system involving the A-V node and the infranodal region; starting from 280 ms, the delayed PR interval suggests involvement predominantly below the A-V node: to a higher PR interval corresponds a higher H-V interval and also, to a relatively shortest A-H interval.

Bundle of His↗
PubMed1991

[Evaluation of syncope in patients with chronic Chagas heart disease].

PURPOSE: To evaluate causes of syncope in patients with Chagas' disease and intraventricular conduction disturbances. METHODS: Nine patients have been studied, being seven males. Average of 49 years. The studied consisted of His Bundle electrogram, determination of Wenckebach period (WP), sinus node recovery time (SNRT), atrial stability and programmed ventricular stimulation (PVS). RESULTS: Monomorphic ventricular tachycardia (VT) was induced in five patients (55.5%), WP depression was observed in three cases, H-V interval prolongation occurred in three cases and the SNRT was normal in hall patients. In one case the electrophysiological study was completely normal. Among five patients with induced VT, with a mean follow-up period of seven months, one died suddenly, three became asymptomatic with antiarrhythmic drugs and one went on a non pharmacological therapy. In the other four patients with a mean follow-up period of 21 months, three are asymptomatic and one presents occasional dizziness (patient with a normal study). Among the patients with VT four presented recurrent syncope while in the group of patients without VT (four patients) all had only one syncopal episode. CONCLUSION: Patients with intraventricular disturbances, Chagas' disease and syncope, VT may be responsible for the symptoms in approximately 44% of cases. The PVS must be considered as a routine in the investigation of these patients.

Adult↗
PubMed1991

[Evaluation of the PR intervals in normal and prolonged maximum limit with short QRS].

PURPOSE: Evaluation of the A-V node function by determining the Wenckebach period (WP) and atropine response in cases of normal PR interval, PR interval at maximum normal range and prolonged PR interval, all with short QRS. PATIENTS AND METHODS: 129 patients, 79 male and 50 female, aged 17 to 84 years (mean 59), asymptomatic or with complaints of palpitations, dizziness, presyncope or syncope has been studied. ECG showed supra-ventricular tachycardia, first degree A-V block or intermittent Mobitz I type A-V block and sick sinus syndrome. Preexcitation (WPW) syndrome and longitudinal A-V dissociation were excluded. Electrical transoesophageal atrial stimulation was performed in all patients for evaluating the PR interval and WP. Atropine test was performed in a group of 16 patients. Based on the values of the WP, patients were divided into three groups: group I, WP greater than or equal to 125 ppm (N = 88); group II, WP ranging 125-110 ppm (N = 16) and group III, WP less than or equal to 110 ppm (N = 25). RESULTS: There was a good decreasing lineal correlation between the PR interval and the WP only in the group III (r = 0.76, p less than 0.01). PR interval greater than 240 ms had greatest and significant incidence in the group III in relation to the other groups in which the number of WP post-atropine normalization was observed. CONCLUSION: There is a strong linear decreasing correlation between the PR interval of the ECG and the WP in individuals with WP less than or equal to 110 ppm. PR interval greatest than 0.24 ms corresponds better to WP below 110 ppm (mean 90 ppm) and the majority of these patients do not normalize the WP with the atropine. We suggest the term "first degree A-V block" for those cases with PR interval greater than 240 ms and "A-V depression" for the cases with PR interval shorter than 240 ms when recorded on the surface electrocardiogram and have been normalized with atropine.

Adolescent↗
PubMed1989

[Significance and prognosis of ventricular extrasystole induced by exertion in patients with arterial hypertension with a normal electrocardiogram].

We studied 13 patients with systemic arterial hypertension and normal electrocardiograms so as to evaluate the significance and prognosis of frequent and complex ventricular premature beats (VPB) induced by exercise testing. After a period of 9 to 33 months of follow-up (mean = 17.6 months), we repeated the exercise testing with the same protocol in all cases. In nine patients (69.2%), the arrhythmia disappeared during exercise, two increased the number of VPB and two others reduced the number of the arrhythmia. Complications, such as sustained ventricular tachycardia, were not seen in any case. The appearance of frequent and complex VPB with stress testing does not seem enhance the risk of sudden death or episodes of spontaneous ventricular tachycardia in patients with arterial hypertension but without electrocardiographic signs of cardiac hypertrophy.

Adult↗