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OBJECTIVE: To determine in arrhythmogenic right ventricular cardiomyopathy the value of QT interval dispersion for identifying the induction of sustained ventricular tachycardia in the electrophysiological study or the risk of sudden cardiac death. METHODS: We assessed QT interval dispersion in the 12-lead electrocardiogram of 26 patients with arrhythmogenic right ventricular cardiomyopathy. We analyzed its association with sustained ventricular tachycardia and sudden cardiac death, and in 16 controls similar in age and sex. RESULTS: (mean +/- SD). QT interval dispersion: patients = 53.8+/-14.1 ms; control group = 35.0+/-10.6 ms, p = 0.001. Patients with induction of ventricular tachycardia: 52.5+/-13.8 ms; without induction of ventricular tachycardia: 57.5+/-12.8 ms, p =0.420. In a mean follow-up period of 41+/-11 months, five sudden cardiac deaths occurred. QT interval dispersion in this group was 62.0+/-17.8, and in the others it was 51.9+/-12.8 ms, p = 0.852. Using a cutoff > or =60 ms to define an increase in the degree of the QT interval dispersion, we were able to identify patients at risk of sudden cardiac death with a sensitivity of 60%, a specificity of 57%, and positive and negative predictive values of 25% and 85%, respectively. CONCLUSION: Patients with arrhythmogenic right ventricular cardiomyopathy have a significant increase in the degree of QT interval dispersion when compared with the healthy population. However it, did not identify patients with induction of ventricular tachycardia in the electrophysiological study, showing a very low predictive value for defining the risk of sudden cardiac death in the population studied.

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The Brugada syndrome is a rare condition, and due to its mutating manner of presentation it may be difficult to diagnose. We report one case and discuss the diagnostic aspects and the clinical outcome of one patient with characteristic findings of this syndrome. These findings are especially defined by J-ST elevation in the right leads of serial electrocardiographic records, wide oscillations of J points and ST segments during 24-hour Holter monitoring, and nocturnal sudden death. We stress the importance of the Holter monitor findings for diagnostic complementation. Through this method it is possible to establish a correlation between vigil activities and sleep and the variability of the degree of impairment in ventricular repolarization.

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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.

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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

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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.

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PURPOSE: To evaluate the role of a 12 month alcohol abstinence period in patients with moderate left ventricular dysfunction treated with anticongestive therapy. METHODS: Prospective observational study with 20 patients with alcoholic cardiomyopathy (ACM), 9 (45%) in functional class (FC) II and 11 (55%) in FC III, 16 (80%) men, mostly black (55%), from 35 to 56 (x = 45) years old, heavy alcohol users (> 80 g ethanol for 51 to 112 (x = 88) months. At the beginning, all agreed to participate with psychotherapy and clinical evaluation. After 12 months, they were divided in G-I, formed by those who remained abstemious and G-II of non-abstemious. RESULTS: After 12 months, among the 11 (55%) who remained in psychotherapy, 8 were in G-I, among those who did not 9 (45%), only 2 (22.22%) remained abstemious (G-I). At the end of the evaluation period, both groups had the same number of patients. Comparing them, we observed: a) lower mean systolic and diastolic left ventricular diameters in G-I; b) more hospitalizations in G-II (3); c) more patients with stable or better clinical evaluation in G-I. CONCLUSION: Despite the initial will, only 50% reached abstinence. When it was reached, patients had a better evolution in left ventricular systolic diameter and abstinence should always be tried even in the presence of moderate left ventricular dysfunction.

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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.

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OBJETIVO - Avaliar o papel da doença coronária (DAC) com comprometimento da artéria descendente anterior (ADA) na cardiomiopatia hipertrófica (CMH) e sua repercussão na evolução, visto ser controverso o significado da necrose e fibrose do septo interventricular (SIV) nesta cardiomiopatia. MÉTODOS - Entre 158 pacientes com CMH, selecionados 6 (3,79 'por cento') com CMH e DAC com lesão obrigatória de ADA, sendo 4 homens, entre 52 e 70 (x=65,16) anos, 4 com a forma obstrutiva da CMH. O tempo de diagnóstico da CMH foi de 78 a 182 (x=141) meses e da DAC de 1 dia a 106 (x=42) meses. Os pacientes foram acompanhados com avaliaçöes clínicas e exames complementares periódicos. RESULTADOS - A forma de apresentação da DAC foi em 5 com angina instável e um com infarto do miocárdio. A ADA estava comprometida entre 60 a 100 'por cento', sendo em um lesão única e nos 5 restaurantes com lesão em 2 ou mais vasos. Na evolução, 3 foram submetidos a revascularização miocárdica (RM), um associada a miomectomia septal, um a angioplastia e 2 somente a tratamento clínico. No período de observação de 76 a 124 meses após o diagnóstico da DAC, ocorreu um óbito. No fim do estudo observamos redução nos valores médios do SIV de 1,53 para 1,40cm, gradiente de pressão entre o corpo e a via de saída do ventrículo esquerdo (VE) de 56 para 15,75mmHg, com discreto aumento no diâmetro diastólico do VE de 4,55 para 4,85cm e do diâmetro sistólico de 2,83 para 3,13cm, sem alterar a dimensão do átrio esquerdo (4,13cm). CONCLUSÄO - A DAC da ADA é bem tolerada na CMH septal assimétrica, participando do processo fibrótico septal e melhorando o desempenho cardíaco, não representando problema adverso na evolução da CMH

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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.

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PURPOSE: The significance of necrosis and fibrosis of the interventricular septum in hypertrophic cardiomyopathy (HCM) is controversial. The purpose of this study was then to evaluate the clinical impact of left anterior descending artery (LAD) disease in HCM. METHODS: Among 158 patients presenting with HCM, 6 (3.79%) had LAD disease. Mean age was 65.16 years (52 to 70), 4 were men and 4 had the obstructive form of HCM. All patients were submitted to complete clinical and laboratory evaluation. Mean time of the diagnosis was 141 months (ranging from 78 to 182) for HCM and 42 months (ranging from one day to 106 months) for LAD disease. RESULTS: Five patients had unstable angina and one had myocardial infarction. LAD disease (60 to 100% coronary narrowing) was present in all patients; one patient had single vessel disease and 5 multivessel disease. During follow-up, 3 patients had coronary artery bypass grafting (CABG), one with associated septal myectomy; one was submitted to coronary angioplasty and 2 were submitted to medical treatment. During a follow-up period ranging from 76 to 124 months after LAD disease diagnosis, one patient died. At the end of the study, a reduction of the thickness of the interventricular septum from 1.53 to 1.40 cm was observed and left ventricular outflow pressure gradient decreased from 56 to 16 mmHg. Left ventricular diastolic diameter increased from 4.55 to 4.85 cm and systolic diameter from 2.83 to 3.13 cm. Left atrium diameter was unchanged. CONCLUSION: LAD disease is well tolerated in the asymmetrical form of HCM and may contribute to septal fibrosis, improving cardiac function. It does not represent an adverse factor in the evolution of HCM.

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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.

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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.

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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.

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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.

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PURPOSE: To evaluate retrospectively clinical features of repetitive monomorphic ventricular tachycardia (RMVT). METHODS: Files of 11 patients with RMVT were analyzed (9 females, mean-age 37 +/- 17 years). All patients were submitted to clinical evaluation, ECG, Holter monitoring stress test, high-resolution ECG and echocardiogram; they were treated with antiarrhythmic drugs. RESULTS: Patients were in NYHA class I or II, 9 asymptomatics and 2 with palpitations. The ECG was normal in all of them. Cardiac memory was observed in 3. A left bundle branch block with inferior axis deviation in the frontal plane was present during RMVT in all patients (right ventricular outflow tract focus). Holter monitoring revealed mean of 12031 +/- 8345 isolated PVC/24h; 2892 +/- 234 ventricular couplets/24h and 1367 +/- 890 VTs/24h (mainly nonsustained). In 6 patients RMVT was suppressed during maximal exercise treadmill. High-resolution ECG was negative in all group. Five patients had a normal echocardiogram while 5 showed mitral valve prolapse. One patient developed tachycardiomyopathy. The arrhythmia was controlled with 320mg of oral sotalol in 3 of 4 that used this drug and with 120mg oral propranolol in one of 6 that used this drug. Drug resistance was present in the others. The mean follow-up period was 38 +/- 16 months. CONCLUSION: The results demonstrate that RMVT is a benign form of VT with no detectable anatomic substract by the currently used methods. It is probably induced by nonreentrant mechanism and frequently drug resistance is observed. Among the antiarrhythmic drugs commonly used, sotalol showed to be the most effective.

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PURPOSE: To analyse the effects of thrombolysis on the integrity of the autonomic nervous system, in patient with acute myocardial infarction (AMI) of the anterior wall, using the determination of the heart rate variability. METHODS: We prospectively evaluated the R-R variability of the 31 consecutive patients with anterior AMI submitted to coronary thrombolysis (25 males; mean age 59 +/- 14 years) from Holter tapes. An algorithm in a 286 computer program was used for heart rate variability (HRV). With this system, R-R variations during sinus rhythm and for a five consecutive minutes periods was determined. The results were expressed as the mean of the total determined periods; the standard deviation of the mean of all determined periods and the mean of the standard deviation. The reperfusion criteria was the early enzymatic rise of the CKMB activity levels (< or = 12 h) combined with a 50% or more reduction in the ST segment elevation within the first hour after thrombolytic therapy and the presence of an accelerated idioventricular rhythm at the same time. The reperfused group (group 1 = 16 patients) and non-reperfused group (group 2 = 15 patients) were compared in terms of R-R variability. RESULTS: Mean R-R: group 1 = 716 +/- 84 ms (540-820 ms); group 2 = 595 +/- 115 ms (390-870 ms)-p < 0.02. ms (34-92 ms); group 2 = 50 +/- 14 ms (23-77 ms)-p < 0.01. HRV 50 ms: group 1 = 2 patients; group 2 = 5 patients. Means SD of the R-R: group 1 = 44 +/- 14 ms (26-65 ms); group 2 = 39 +/- 17 ms (19-69 ms)-p: ns. CONCLUSION: Patients with anterior AMI and thrombolytic therapy demonstrate greater HRV; this finding suggested better integrity of the autonomic nervous system, with possible effects on prognosis.

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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.

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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.

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