Electrical behavior of T-wave polarity alternans in patients with congenital long QT syndrome.

OBJECTIVES: This study was designed to evaluate the incidence and characteristics of onset of T-wave polarity alternans (TWPA) in patients with long QT syndrome. BACKGROUND: The T-wave alternans is a phenomenon that consists of beat-to-beat variability in the amplitude, morphology, and sometimes polarity of the T-wave, and it may trigger life-threatening arrhythmias. METHODS: The 24-h Holter recordings of 11 patients with congenital long QT syndrome were studied. Episodes of TWPA with 10 or more consecutive cycles were selected and analyzed as follows: 1) mean cycle length (MCL) and QTc interval duration (QTcI) of the episodes of TWPA and the 10 cycles preceding and succeeding the TWPA; 2) MCL and QTcI of the third, second, and first minute before onset (Mn_3, Mn_2, Mn_1); 3) MCL and QTcI from the tenth to the first cycle immediately preceding the onset of TWPA (R_10 to R_1); 4) MCL and QTcI from the first to the fourteenth cycle during alternans (R0 to R14); 5) MCL and QTcI from the first to the tenth cycle immediately succeeding TWPA (R+1 to R+10); 6) linear correlation (Lnc) between QT interval and cycle length (CL) (LncQT/CL) during alternans and for the 10 preceding cycles; 7) Lnc between the first three alternans cycles and episode duration (Lnc 3CL/EpD); and 8) difference between the longest and shortest QTc interval. We also selected episodes consisting of four or more consecutive cycles in order to analyze daily rhythms of the phenomenon. RESULTS: The TWPA was observed in 5 (45%) out of the 11 patients studied. The alternans process is initiated by a sudden shortening of the first alternans cycle without previous heart rate changes and ends at the moment when prolongation of the cycle tends to occur. LncQT/ CL-alternans: r = 0.38 +/- 0.2 (p = 0.20); without alternans: r = 0.81 +/- 0.06 (p = 0.01). Lnc 3CL/EpD: r = 0.002 (p = 0.992). The QTc difference during alternans: 312.0 +/- 52.1 ms; without alternans: 86.0 +/- 36.4 ms (p = 0.001). Daily rhythm: 71% of the episodes occurred between 8 AM and 8 PM, with higher incidence during the morning. CONCLUSIONS: The TWPA was dependent on the cardiac CL; there was loss of the LncQT/CL and an increase in the QT interval variability. Like other biological variables, T-wave polarity alternans has a higher density during the morning.

[Contribution of dynamic electrocardiography by Holter monitoring in the evaluation of congenital long QT syndrome patients]. / Contribuição de eletrocardiografia dinâmica pelo sistema Holter na avaliação de pacientes com a síndrome congênita do QT longo.

PURPOSE: The purpose of this study was to evaluate the value of ambulatory electrocardiogram as a clinical tool to assess ventricular repolarization in patients with the congenital long QT syndrome. METHODS: The study population comprised six patients and their data were compared to a control group of six patients matched in age and gender. The QT interval (ms), corrected by the heart rate, was measured in the first minute of each hour using two monitoring leads, with the mean of six consecutive complexes. The data obtained include the morphologic pattern of T wave, the mean 24-h QTc interval, relation between QT and cardiac cycle, QTc variability (assessed calculating hourly standard deviation of the interval and then obtaining the global 24-h mean), QTc dispersion (difference between the longest and shortest QTc interval). RESULTS: In all patients abnormal patterns of T waves were detected with frequent episodes of T wave alternans. Mean 24-h QTc--patients: 598.2 +/- 73.8 ms; controls: 436.1 +/- 8.9 ms (p = 0.000). Linear correlation and regression between QT and heart rate-patients: r = 0.812; controls: r = 0.967 (p = 0.000). QTc variability-patients: 36.9 +/- 17.2 ms; controls: 14.7 +/- 2.1 ms (p = 0.01). QTc dispersion-patients: 168.3 +/- 70.2 ms; controls: 53.3 +/- 8.1 ms (p = 0.000). CONCLUSION: The data showed increased hourly QTc variability. QTc dispersion and worse correlation between QT and heart rate. This data may reflect an abnormally augmented ventricular vulnerability.

[Sinus node modification by catheter using radiofrequency current in a patient with inappropriate sinus tachycardia. Evaluation of early and late results]. / Modificação do nódulo sinusal via cateter por energia de radiofreqüência em paciente com taquicardia sinusal inapropriada. Avaliação dos resultados imediatos e tardios.

This article reports the early and late results of a patient in whom radiofrequency current was used to ablate an incessant inappropriate sinus tachycardia. During successful radiofrequency application there was a sudden change of rate and subsequent emergence of a stable rhythm with the same sinus node P wave characteristics. During follow-up, normal cardiac cycles were still present after six months of the procedure, although the patient still complained of palpitations, suggesting no correlation with the heart rate.

Contribuição de eltrocardiografia dinâmica pelo sistema holter na avaliação de pacientes com a síndrome congênita do QT longo / Contribution of the dynamic electrocardiography by holter monitoring in the evaluation of congenital long QT syndrome patients

OBJETIVO - Avaliar pelo Holter-24h a dinâmica da repolarização ventricular de pacientes com a síndrome congênita do QT longo. MÉTODOS - Foram incluídos seis pacientes, sendo os resultados confrontados com os observados em um grupo controle semelhante em número, idade e sexo. Analisaram-se nas gravaçöes a morfologia da onda T e sua dinâmica, o intervalo QTc médio para as 24h, as relaçöes entre QT e ciclo cardíaco, a variabilidade do QTc das 24h, bem como a sua dispersão (diferença entre o maior e menor QTc observado). Todas as variáveis foram definidas a partir da medida do intervalo QT obtida no 1§ minuto de cada hora da gravação. RESULTADOS - Alteraçöes morfológicas da onda T estiveram presentes em todos os pacientes, observando-se em cindo deles freqüentes episódios de alternância da onda T, achados ausentes no controle. QTc médio para as 24h - controle: 436,1ñ8,9ms; pacientes: 598,2ñ73,8ms (p=0,000). Correlação linear entre QT e ciclo cardíaco - controle: r=0,967; pacientes: r=0,812 (p=0,000). Variabilidade do QTc para as 24h - controle: 14,7ñ2,1ms; pacientes: 36,9ñ17,1ms (p=0,01). Dispersão do QTc - controle: 53,3ñ8,1ms; pacientes: 168,3ñ70,2ms (p=0,000). CONCLUSÄO - Os resultados apresentaram ampla variabiblidade dos intervalos QTc nas 24h, menor adaptabiblidade do intervalo QT às flutuaçöes dos ciclos cardíacos e significativa dispersão da repolarização ventricular nas 24h, confirmando mais uma vez a existência de importante alteração da vulnerabilidade ventricular nesses pacientes.

Dispersäo temporal da repolarizaçäo ventricular, alternância elétrica da onda T e variabilidade dos intervalos Qt: metodologia de aquisiçäo, análise dos dados, importância clínica / Temporal dispersion of the ventricular repolarization, T wave eletrical alternans and Q-T intervals variability. Methodology analysis of data and clinical importance

No presente artigo, os autores fazem uma revisäo da metodologia e da importância clínica de alguns novos métodos de análise da repolarizaçäo ventricular pelo eletrocardiograma de superfície ou utilizando a eletrocardiograma de superfície ou utilizando a eletrocardiografia dinâmica pelo sistema Holter. Incluem,no estudo, a análise da dispersäo temporal da repolarizaçäo ventricular, a variabilidade dos intervalos Qt e a alternância elétrica da onda T. Acentuam a importância e as limitaçöes desses métodos na estratificaçäo de risco arritmogênico em algumas cardiopatias e as perspectivas dos mesmos com os estudos em andamento que tentam desenvolver programas e algoritmos que permitam uma correta determinaçäo automática das variáveis envolvidas

Fibrilação e flutter atriais / Atrial fibrillation and flutter

No presente artigo os autores fazem uma breve revisão da clínica dos mecanismos eletrofisiológicos do Flutter e Fibrilação atriais. Procuram de forma sucinta fazer uma atualização terapêutica, uma vez que o grande avanço ocorrido na última década na área de eletrofisiologia clínica possibilitou não apenas um melhor conhecimento dos mecanismos das arritmias cardíacas e o mecanismo de ação das drogas antiarrítmicas, como também o tratamento não farmacológico das mesmas. Nesta revisão, os autores procuram abranger o tratamento farmacológico das arritmias, a indicação atual para a anticoagulação na prevenção dos fenômenos tromboembólicos e avaliar as indicaçöes atuais, sucessos e limitaçöes da terapia não farmacológica dos distúrbios do ritmo em questão.

[Relationship between mitral valve prolapse and arrhythmogenic right ventricular disease]. / Associação entre prolapso valvar mitral e doença ventricular direita arritmogênica.

PURPOSE: To evaluate some features of ventricular arrhythmias in patients with mitral valve prolapse. METHODS: We studied 25 patients (female: 19; mean age: 37 +/- 13 years) with ventricular arrhythmias, mitral valve prolapse and normal ventricular function. All patients underwent a 24h Holter and high resolution ECG (HRECG). The Qtc intervals were measured in lead II (normal < 0.44 s). In order to define the possible origin of the ventricular focus, the morphology of the ectopic beats were analysed in leads I, II, aVF, V1 using the following criteria: 1) LBBB morphology with left axis deviation in the frontal plane (FP): origin at the inflow tract of the right ventricle (RV); 2) LBBB morphology with right axis deviation in the FP: origin at the outflow tract of the RV; 3) RBBB morphology with left axis deviation in the FP: origin at the posterior region of the left ventricle (LV). RBBB morphology with right axis deviation in the FP: origin at the anterior region of the LV. RESULTS: Twenty three (92%) patients showed > 720 isolated ventricular ectopic beats/24 h. Paired ventricular response was detected in 18 (72%) patients and non-sustained VT in 15 (60%). HRECG was positive in six (24%) patients and Qtc interval was prolonged in 13 (52%). RV was the site of origin of the ventricular ectopic beats in 85% of the patients (outflow: 85%; inflow: 15%). Only five (20%) patients had arrhythmias from the LV. CONCLUSION: There was a high incidence of ventricular arrhythmias with a low incidence of positive HRECG tests, suggesting that the mechanisms of the arrhythmias do not correlate with slow intramyocardial conduction. It was noted a strong association between mitral valve prolapse, arrhythmogenic right ventricular disease and Qtc prolongation. It is possible that in some of this patients the finding could represent a global myocardial disease.

Ablaçäo de vias anômalas com conduçäo decremental

Estudos eletrofisiológicos têm comprovado a existência de vias acessórias atípicas que apresentam características funcionais semelhantes ao nó atrioventricular (AV), ou seja, propriedade de conduçäo decremental. Diferente das vias anômalas convencionais, nas quais a conduçào anterógrada e/ou retrógrada se faz de maira rápida, essas vias conduzem o estímulo elétrico de forma lenta. A presença no circuito reentrante de duas estrutras de conduçäo lenta do tipo nodal AV permite, por vezes, a manutençäoa taquiarritmia originando as formas permanentes ou incessante. Seräo revisadas as vias anômalas de conduçäo decremental anterógradas e retrógradas, apresentando o estado de arte da técnica de ablaçäo com radiofrequência (RF), em um grupo de pacientes submetidos ao procedimento em nossa institutiçäo.

Signal-averaged P wave in patients with Wolff-Parkinson-White syndrome after successful radiofrequency catheter ablation.

OBJECTIVES: We attempted to establish a relation between the atrial conduction time assessed by the signal-averaged P wave electrocardiogram and episodes of paroxysmal atrial fibrillation in patients with the Wolff-Parkinson-White syndrome. BACKGROUND: The incidence of paroxysmal atrial fibrillation is higher in patients with the Wolff-Parkinson-White syndrome than in normal persons. However, the role of intraatrial conduction delay in precipitating the disorganization of atrial rhythm is not completely understood. METHODS: The total duration of the signal-averaged P wave and the P wave in standard lead II was evaluated after successful radiofrequency catheter ablation in 28 patients with the Wolff-Parkinson-White syndrome. The data obtained from 17 patients (61%) with a documented history of prior paroxysmal atrial fibrillation (group I) were compared with those obtained from 11 patients (39%) without a history of atrial fibrillation (group 2). Both groups were further compared with a normal control population. RESULTS: The mean +/- SD signal-averaged P wave duration in group 1 was 141.94 +/- 9.47 ms (range 130.0 to 171.0). Fourteen patients (82%) in this group showed a P wave duration > 135.0 ms. In group 2, the signal-averaged P wave duration was 126.64 +/- 8.72 ms (range 111.0 to 136.0). Only one patient in this group (9%) showed a P wave duration > 135.0 ms (p < 0.000, group 1 vs. group 2). The signal-averaged P wave duration in the control group was 124.46 +/- 4.49 ms (range 115.0 to 129.5; p < 0.000, group 1 vs. the control group; p < 0.454, group 2 vs. the control group). The P wave duration in lead II was 92.06 +/- 8.85 ms in group 1 and 92.27 +/- 7.86 ms in group 2 (p < 0.949). Using a cutoff value of < 135.0 ms for a normal signal-averaged P wave duration, the method had a sensitivity and specificity and positive and negative predictive values of 82%, 91%, 93% and 77%, respectively, for identifying patients with clinical paroxysmal atrial fibrillation. CONCLUSIONS: In the current study, the signal-averaged P wave showed a prolonged intraatrial conduction time in patients with the Wolff-Parkinson-White syndrome and paroxysmal atrial fibrillation. These patients can be differentiated from those with the pre-excitation syndrome without clinical atrial fibrillation as well as from normal subjects. The prolonged intraatrial conduction time may serve as an atrial substratum for development and maintenance of the fibrillatory state.

[Mechanisms and dynamics of episodes of progression of of 2:1 atrioventricular to high degree atrioventricular block]. / Mecanismos e dinâmica da progressão dos episódios de bloqueio atrioventricular 2:1 para bloqueio atrioventricular de alto grau.

PURPOSE: To evaluate the mechanisms and dynamics of episodes of progression to high degree (HD) atrioventricular (AV) block (B) analyzed during incremental atrial pacing (St), in patients with previous 2:1 His-Purkinje (HP) AVB. METHODS: Data from 4 patients were analyzed. All of them with history of syncope and ECG exhibiting 2:1 AVB with wide QRS pattern. The AVB was in the HP system (HPS) in all. Every patient was submitted to electrophysiologic study with incremental atrial pacing, by which the conduction sequences and the AV conduction ratios (AVR) were analyzed. The basal (B) cycle length (CL) was defined as the shortest interval between two conducted beats (spontaneous or pacing-induced). The incremental atrial stimulation was performed beginning with CL 10 msec shorter than BCL until reaching 250 msec. RESULTS: Nineteen episodes of progression to HD-AVB were seen. A) With StCL between 31 and 26% of BCL, AVR were 3:1, 4:1 and 5:1, with only one blocking zone (BZ) in the HPS; B) with StCL between 24 and 22% of BCL, AVR were 5:1, 7:2, 9:2e11:3. In this situation a 2nd BZ ensues-on proximal, site of a decremental conduction, situated in the AV node (AVN) or in the HPS, and the other (distal level) always in HPS; C) with StCL between 24 and 16% of BCL, AVR were 5:1, 6:1, 10:2, 11:2 and 12:3. Here, these AVR were explained by postulating 3 BZ where 2 were in AVN and 1 in HPS, or inversely with 1 in AVN and 2 in HPS. The decremental conduction occurred in 1 or 2 out 3 BZ and an integral conduction (like 2:1 or 3:1) in the others. CONCLUSION: The BCL is the determinant of the AVR observed. As the StCL is shortened (< 26% BCL) a 2nd or 3rd BZ in the AVN or in the HPS ensues. These observations suggest that the mechanisms and dynamics of progression to HD-AVB apply only during incremental atrial pacing and there is a clear difference with what has been observed with the progression occurring exclusively at AV node.

[High-resolution P-wave electrocardiogram in patients with a history of paroxysmal atrial fibrillation]. / O eletrocardiograma de alta resolução da onda P em pacientes com história de fibrilação atrial paroxística.

PURPOSE: To study by using the signal-averaged P wave, the atrial activation of patients with documented episodes of paroxysmal atrial fibrillation (PAF). METHODS: This study enrolled a total of 20 patients with documented episodes of paroxysmal atrial fibrillation (males 14; mean age 58.4 +/- 10.6 years). The signal-averaged P wave was recorded with a Corazonix Predictor II system. The total P wave duration was determined from the combined filtered x,y,z vector-magnitude and used for analysis. The results were compared with a normal group of 10 patients, matched in age. RESULTS: In the control group, the total P wave duration ranged from 120.0 to 135.0 (mean = 128.3 +/- 5.8) ms. In the group of PAF, the total P wave duration ranged from 118.0 to 168.5 (mean = 151.5 +/- 13.7) ms (p < 0.000). Sixteen (80%) of this patients showed a P wave duration > 140.0 ms. With a cut < 140.0 ms for the normal atrial activation, the sensitivity was 76%, specificity was 100%, positive and negative predictive value were 100% and 60% respectively for the method detected patients with PAF. CONCLUSION: Patients with PAF showed a prolonged signal-averaged P wave duration and should be differentiated by this method from the normal population.

[Ablation therapy of type I atrial flutter with radiofrequency]. / Terapia ablativa do flutter atrial tipo I com radiofreqüência.

PURPOSE--To present initial experience on radiofrequency (RF) ablation of atrial flutter (AFL) guided by anatomic and electrophysiologic parameters. METHODS--Eight patients (six males), mean-age of 42 +/- 17.5 years with chronic type I AFL (mean cycle length of 251 +/- 14.3 msec, range 240 to 280 msec) were undergone to RF catheter ablation applied between inferior vena cava (IVC) and tricuspid annulus (TA). Two had persistent and two the paroxysmal form. Two had surgical corrected congenital heart disease (atrial septal defect in 2 and ventricular septal defect in 1). Four had systolic dysfunction and 2, an atrial tachycardia associated with the AFL. RESULTS--Areas of slow conduction represented by fractionated potentials were recorded between IVC and TA in all patients. RF ablation was successful in 8/8 patients (100%). The mean number of RF applications was 9.2 +/- 6.2 (4-24). The successful ablation site was located in the isthmus between IVC and TA in seven patients and in the lateral wall in the patient with ASD. Successful sites had an early atrial activation preceding the atrial electrogram (range from -65 to -82 ms). In one patient the RF energy was successfully delivered between the atriotomy scar (AS) and IVC. After three months follow-up six remained free of recurrent AFL. One pt had type 1 AFL recurrence and one with ASD had a type II AFL. The Type II AFL was successfully ablated between AS and IVC. CONCLUSION--Fractionated potentials were commonly observed between IVC and T; AFL ablation can be guided by anatomic landmarks or electrophysiologic parameters; electrograms recorded at successful sites were early and never fractionated; the long-term evaluation must be analyzed prospectively.

[The electrocardiogram of high resolution during ventricular tachycardia]. / O eletrocardiograma de alta resolução durante taquicardia ventricular.

PURPOSE: To evaluate by the signal averaged-ECG (SAECG) the initial portion of the activation of the sustained ventricular tachycardia (SVT) and monomorphic repetitive ventricular tachycardia (MRVT), correlating the findings with those obtained during sinus rhythm (SR). METHODS: Ten patients was studied; five with SVT and five with MRVT. Patients with SVT presented a positive SAECG while patients with MRVT the test was negative, during SR. The findings of this two populations were compared with those obtained in a group of ten patients with advanced bundle branch block (ABBB: five RBBB and five LBBB). We analyzed in the vector-magnitude obtained during VT and ABBB, the root mean square of the initial 40 ms portion of the activation (RMS40) and the duration of the low amplitude signals < 40 microV from the beginning of the filtered QRS (LAS). To define the positiveness of the test in SR, we analyzed the final RMS40 (normal > 20 microV), the duration of the LAS < 40 microV at the end of the activation (normal < 38 ms) and the total QRS duration (QRSD-normal < 114 ms). RESULTS: (mean)-SVT in SR: RMS40 = 11.2 +/- 6.2 microV; LAS = 47.4 +/- 5.8 ms; QRSD = 131.2 +/- 8.7 ms. SVT during VT: RMS40 = 6.9 +/- 4.5 microV; LAS = 54.5 +/- 9.1 ms. RMVT in SR: RMS40 = 59.7 +/- 49.0 microV; LAS = 28.3 +/- 8.5 ms; QRSD = 93.1 +/- 13.0 ms. MRVT during VT: RMS = 25.2 +/- 8.8 microV; LAS = 28.9 +/- 11.1 ms. RBBB: RMS = 53.3 +/- 34.2 microV; LAS = 22.6 +/- 9.8 ms. LBBB: RMS = 54.7 +/- 37.3 microV; LAS = 11.4 +/- 4.6 ms. The comparison between the data from SVT and MRVT/ABBB showed p < 0.01. CONCLUSION: In the studied population, the SAECG was able to identify abnormal LAS initiating SVT, that were not present in MRVT and ABBB. This signals probably represents intra-myocardial slow conduction, as a portion of a re-entry circuit. There was an excellent correlation between the findings during SVT and MRVT with those obtained in SR.

[Study of the autonomic behavior of escape rhythms in congenital atrioventricular block]. / Estudo do comportamento autonômico dos ritmos de escape no bloqueio atrioventricular congênito.

PURPOSE: To study the autonomic behavior of the escape rhythm in congenital complete heart block (CCHB), using heart rate variability (HRV). METHODS: A group of 10 asymptomatic patients with CCHB and narrow QRS was studied, 7 females; mean age = 14 +/- 9 years. The following time domain indexes were analyzed from a 24 hour Holter monitoring. The mean of all RR intervals (NN); the standard deviation of the mean (CLV5); the mean of all standard deviations (SDNN); the percent of successive differences longer than 50 ms (pNN50); the shortest cycle (CC) and the longest cycle (CL). The results were compared with a control group, using the Wilcox test for statistical analysis. RESULTS: The results were: NN = 1016 +/- 276 ms in CHB and 725 +/- 121 ms in control (p < 0.01); CLV5 = 184 +/- 97 ms in CHB and 125 +/- 38 ms in control (p = NS); SDNN = 102 +/- 32 ms in CHB and 88 +/- 29 ms in control (p = NS); rMSSD = 113 +/- 69 ms in CHB and 78 +/- 28 ms in control (p = NS); pNN50 = 43 +/- 26% in CHB and 33 +/- 12% in control (p = NS); CC = 582 +/- 129 ms in CHB and 333 +/- 49 ms in control (p = 0.05). CONCLUSION: No statistical difference was noted by comparing HRV indexes in CHB with control subjects, showing that the autonomic behavior of the escape rhythm in CCHB is similar to the sinus node in asymptomatic patients. The differences in NN, CC and CL are probably related to intrinsic properties of each command.