Prof. Paulo Roberto Benchimol Barbosa's Home Page

FORUM OF ELECTROCARDIOLOGY

Welcome to Prof. Paulo Barbosa's HOME PAGE. Prof. Paulo Barbosa is Medical Doctor and Biomedical Engineer. He is medical staff of the Department of Cardiology of Rio de Janeiro State University Hospital CCU, since 1988, and Phisician and Medical staff of the Intensive Care Unit of the Rio de Janeiro State Fire Department Hospital, since 1986. Prof. Paulo Barbosa is specially interested in High Resolution Electrocardiography (HRECG) and Heart Rate Variability Analysis (HRVA). This HOME PAGE is under construction and is devoted to be a forum for debates on concepts and advances in non-invasive electrocardiology. It is open to anyone who is involved with these subjects and wants to share knowledge and developments.

Suggestions for debate are :

Diagnostic significance of HRECG in the assessmentt of patients at risk of sustained ventricular tachycardia/sudden death.Does it have a better diagnostic performance than measurement of the ejection fraction ?
Diagnostic significance of HRVA in the assessment of patients at risk of sustained ventricular tachycardia/sudden death.
Correlation between HRECG and HRAV in the assessment of patients at risk of sustained ventricular tachycardia/sudden death.
Commons physiological substrata for HRECG and HRVA.
BiSpec (TM) Filter vs. Butterworth Bi-directional Filter (SIMSOM) : Can both be used to evaluate ventricular late potentials (VLP) in time domain with the same diagnostic value ?
P wave HRECG and paroxysmal atrial fibrillation : Does HRECG in the time and in the frequency domain improve diagnostic accuracy when compared to the measurement of the P wave width in conventional 12 lead ECG ?
HRECG and HRVA in Human Immunodeficiency virus (HIV) infection : Are VLP and low heart rate variability associated with poor outcome in this group of patients ?

Whether you want to discuss or share opinions about non-invasive electrocardiology, please write to my e-mail. If you wish, your opinion can be exposed for peers discussion.

Thank you for your interest.

Comments and discussions, write to ecgar@ecgar.com

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Current Researches of Dr. Barbosa

Comparative Study between BiSpec(TM) and Bi-directional Filters applied to Ventricular Late Potential Identification

Analysis of the Ventricular Late Potentials in HIV Positive Patients Based on the RR Interval Histogram

A New Method for Noise Rejection in SAECG

Comparison of BiSpec (TM) filter at 40 Hz high-pass with Butterworth bi-directional 4 poles 40 Hz high-pass and 2 poles 250 Hz low-pass for analysis of late potentials in Chagas' Disease : Does BiSpec(TM) overestimate late potentials ?

Paulo Roberto Benchimol Barbosa, MD

Medical Staff of the Department of Cardiology of the Rio de Janeiro State University Hospital.

Phisician and Medical staff of the ICU of the Rio de Janeiro Central Fire Department Hospital

BiSpec (TM) filter was designed to be standard default in Predictor II (ART, Austin, Texas, USA.) Signal-Averaged System Analysis, and have been proposed to be as efficient as Butterworth bi-directional (SIMSON's Filter) filter in detecting late potentials. However, few data are currently available performing comparison between these filters. One of these suggests BiSpec(TM) filter may cause unpredictable results when compared with Butterworth bi-directional because of high standard deviation in LAS40 analysis. This work intends to analyze BiSpec(TM) filter comparing it with Butterworth bi-directional using Predictor II software and observe its effect in late potential detection accuracy, taking as standard the bi-directional filter endorsed by the American College of Cardiology, the American Heart Association and the European Society of Cardiology.

A group of 28 patients with Chagas' Disease was analyzed comparing the effect of BiSpec(TM) 40 Hz (BS) filter with Butterworth bi-directional 40 Hz Hi-pass 4 poles and 250 Hz low-pass 2 poles (BWBD). The group was composed of 28 sequential patients with Chagas' Disease, attending to the ambulatory of cardiomyopathies for routine evaluation. All patients provided consent for this evaluation and they were also part of a study in progress in our Department of Cardiology.

18 patients were female and the age ranged from 24 to 74 with a mean+-SD 51.1+-10.7 years. The exams were obtained with patients lying in decubitus dorsalis and took a mean+-SD of 778+-386 heart beats, and achieved a final noise of mean+-SD of 0.31+-0.04 uV. The skin was prepared with alcohol and slightly abraded to provide good electrical conduction. The leads employed were Frank XYZ.

Among patients analyzed, 17 patients had intra-ventricular conduction disturbance, been 5 left and 12 right complete bundle branch block either with or without left antero-superior divisional hemi-block. These patients were included in the study because conduction disturbances bear a perfect late potentials behavior and provide an extended condition for comparison. The group of all patients (group I) was divided into two small groups of patients with (group II) and without (group III) conduction disturbances. The parameters drawn for comparison were Terminal QRS RMS40, LAS40 and Total QRS DURation (QRSDUR), RMS and INTegral. All these parameters were measured in both filters and in all patients using only auto-measure facility option. The statistical procedure employed for analysis was the paired "t" Student test with alfa error level at 5%. Using the BWBD as a gold standard and establishing at least two of RMS40, LAS40 and Total QRS DURation positive parameters as indicative of pathologic LP in non-conduction disturbance patients group and both RMS40 and LAS40 positive as pathologic LP in conduction disturbance patients group, it was set sensitivity, specificity, positive and negative predictive values and total accuracy, for BS filter. The cutting edges employed as diagnostic of a positive exam were <20 uV for RMS40, >38 ms for LAS40 and >114 for Total QRS duration.

The comparisons were conducted in the group of all patients and the groups with and without conduction disturbances. Tables I, II and III display the results comparing the differences for each parameter between BWBD and BS, and also displaying diagnostic value parameters.

Table I - Comparison of time domain parameters between BWBD and BS filters in group I (n=28)

Parameter	RMS40	LAS40	QRSDUR	RMS Total	Integral
Mean	3.3	-10.7	0.2	19.7	1.3
SD	11.7	19.6	4.5	13.7	0.9
Calculated "t" Student	1.5	-2.9	0.2	7.6	8.3
probability level	0.15	<0.05	0.82	<<0.05	<<0.05
results	-	*	-	*	*

Table II - Comparison of time domain parameters between BWBD and BS filters in group II (n=11)

Parameter	RMS40	LAS40	QRSDUR	RMS Total	Integral
Mean	4.4	-0.9	-0.4	21.2	1.0
SD	19.1	5.5	6.1	17.0	0.8
Calculated "t" Student	0.7	-0.5	-0.2	4.0	4.1
probability level	0.49	0.64	0.84	<<0.05	<<0.05
results	-	-	-	*	*

Table III - Comparison of time domain parameters between BWBD and BS filters in group III (n=17)

Parameter	RMS40	LAS40	QRSDUR	RMS Total	Integral
Mean	2.3	-17.4	0.5	16.7	1.5
SD	4.5	22.6	3.7	8.2	0.9
Calculated "t" Student	2.1	-3.2	0.6	8.4	7.0
probability level	0.05	<0.05	0.56	<<0.05	<<0.05
results	-	*	-	*	*

observations : 1) amplitude values are in uV. 2) duration values are in ms. 3) p is the "probability of greater value for the "t" calculated. 4) "*" means statistically significant, and "-" is not significant. 5) group I - all patients. 6) group II - non-conduction disturbance group. 7) group III - conduction disturbance group.

Table IV - Diagnostic value of BS filter in relation to BWBD in group I (n=28)

SENSITIVITY	SPECIFICITY	POSITIVE	NEGATIVE	TOTAL ACCUARCY
93%	85%	88%	86%	89%

Table V - Diagnostic value of BS filter in relation to BWBD in group II (n=11)

SENSITIVITY	SPECIFICITY	POSITIVE	NEGATIVE	TOTAL ACCUARCY
100%	100%	100%	100%	100%

Table VI - Diagnostic value of BS filter in relation to BWBD in group III (n=17)

SENSITIVITY	SPECIFICITY	POSITIVE	NEGATIVE	TOTAL ACCUARCY
92%	60%	85%	75%	79%

observation : 1) POSITIVE = POSITIVE PREDICTIVE VALUE. 2) NEGATIVE = NEGATIVE PREDICTIVE VALUE.

The standard deviation of RMS40 and QRSDUR of groups I and III are displayed in tables I and II. They are at least 4 times greater than the mean indicating the dispersion of the results are very elevated These data are consistent with those published by Metha et al., the inventors of BS filter. In spite of the "t" test provided statistically not significant differences in results, it could be stressed the results are inconsistent because the dispersion of individual differences for each of the parameters is very elevated. LAS40, in counterpart, presented a statistically significant difference for patients in groups I and III, but not in group II.

In all three groups, the RMS and the Integral of Total QRS are significantly lower in BS filter setting than BWBD. The reduction of the total QRS energy by the BS filter indicates that the BS significantly underestimate the filtered voltage of the signal. It clearly denotes BS lowers down the energy producing therefore a systematic bias. The reduction in RMS40 voltage, therefore and increase in LAS40 duration are expected in BS filter when compared with BWBD.

The elevated dispersion is also observed in RMS40 parameter and virtually all parameters analyzed, by at least 4 times the mean, in all groups. It means BS filter deforms the QRS complex in a very unpredictable form.

Diagnostic parameters are very enthusiastic when observed in table V. However, tables IV and VI suggests the BS filter may cause errors in interpretation of the results, specially in groups where late potential are adequately mimicked.

The conditions evaluated here may have harmful implications. Considering the filter setting was factory default in former Corazix Predictor IIc software, the bias detected may have consequences in diagnostic and further medical invasive procedures. Whether the false detection of late potentials by BS filter may lead to unnecessary electrophysiologic invasive procedures with associated morbidity, has yet to be proved. On the other hand, lack of detection of late potentials may have direct prognostic implications.

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Analysis of the Ventricular Late Potentials Based on the RR Interval Histogram in HIV Positive Patients

Paulo Roberto B. Barbosa1,2, Carlos Alberto Morais de Sá2, José Barbosa Filho2, Jurandir Nadal1.

1Biomedical Engineering Program, COPPE-UFRJ. 2Dept. of Immunology, Uni-Rio, Brazil

Ventricular late potentials (VLP) are fragmented electrical activities which originate in regions with delayed conduction in the damaged myocardium, and are markers of ventricular arrhythmia due to reentry. The infection of the myocardial fibers and the dendritic cells by the HIV virus and the presence of VLP in HIV positive patients has already been reported. The presence of VLP reinforces the arrhythmic mechanism underlying the infection. This study was conducted to assess the prevalence of VLP in HIV positive patients, and to evaluate whether VLP shows any influence of the heart rate. Fourteen patients (three male), 35±7 (mean ± SD) years old, under clinical follow up in the Gafrée e Guinle University Hospital were admitted for SAECG evaluation. Five were CDC Class II and 9 were CDC Class IV. Seven of the CDC Class IV were taking anti-viral drugs. The SAECG signals were acquired over 20 minutes with a system previously reported, using the XYZ Frank leads. The histograms of the normal RR intervals were constructed and the QRS complexes separated into three classes: modal, pre-modal (shorter RR) and post-modal (larger RR). The normal heart beats were all averaged together, and then separately for each of the RR interval classes, from which the vector magnitudes were calculated. The parameters then analyzed were the filtered QRS complex duration (QRSF), the RMS40 and the LAS40. Five exams were VLP positive in the ensemble class. When pre-modal, modal and post-modal classes were considered separately, eight patients became VLP positive, from five exams in the pre-modal, one in the modal and six in the post-modal class. Two patients were VLP positive exclusively in the pre-modal, none in the modal and one in the post-modal class (p = 0.048). These results show that VLP is highly prevalent in the group under study and suggest that VLP occurrence in HIV positive patients may be dependent on the instantaneous heart rate, or masked by heart rate variability.

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