Contribuição da análise eletrofisiológica e anatômica do circuito atípico da taquicardia atrioventricular nodal / Contribution of the electrophysiological and anatomical analysis of the atypical atrioventricular nodal tachycardia circuit

OBJETIVOS: Analisar a condução retrógrada durante os episódios de ritmo juncional ectópico acelerado (JET) e avaliar a existência da relação entre a presença de um bloqueio retrógrado e o risco de desenvolvimento de bloqueio atrioventricular (BAV) durante os procedimentos de ablação por radiofreqüência de pacientes portadores de taquicardia atrioventricular nodal (TAVN). MÉTODOS: Foram 145 pacientes portadores de TAVN, de ambos os sexos, com 16 a 84 anos submetidos à ablação com cateter de radiofreqüência na região póstero-septal do átrio direito. Critérios avaliados: localização anatômica e comportamento eletrofisiológico da condução retrógrada durante TAVN (definindo a taquicardia como típica ou atípica) e monitorização da condução retrógrada durante o JET para eventos de risco para BAV. RESULTADOS: Dos 145 pacientes estudados, 132 (91 por cento) preencheram critérios eletrofisiológicos e anatômicos da forma típica da TAVN e 13 (9 por cento), da atípica. Durante a ablação, 5,3 por cento do grupo das típicas e 30,8 por cento das atípicas apresentaram eventos de risco para BAV. Complicações após ablação foram um episódio de BAV total e outro de BAV de primeiro grau nas típicas e um de BAV de primeiro grau nas atípicas. Os três episódios foram precedidos de eventos de risco que resultaram em uma injúria nodal após procedimento. CONCLUSÃO: Portadores de TAVN atípica apresentaram porcentualmente mais eventos preditores de risco para BAV do que os da típica (p = 0,021), sendo fundamental a observação criteriosa da condução retrógrada durante o JET, afim de se evitar permanente da condução nodal, como o BAVT, após o procedimento ablativo.

OBJECTIVES: To analyze retrograde conduction during junctional ectopic tachycardia (JET) episodes and investigate the existence of a relationship between the presence of a retrograde block and the risk of atrioventricular block (AVB) development during radiofrequency ablation procedures in patients with nodal atrioventricular tachycardia (NAVT). METHODS: 145 male and female patients aged 16-84 years, with NAVT who had undergone radiofrequency catheter ablation in the posteroseptal region of the right atrium were studied. Evaluation criteria were anatomical location and electrophysiological behavior of retrograde conduction during NAVT, in order to understand the nodal reentrant circuit (classifying the tachycardia as typical or atypical), and monitoring of retrograde conduction during JET episodes for risk-predicting AVB events. RESULTS: Of the 145 patients studied, 132 (91 percent) met electrophysiological and anatomical criteria of the typical form of NAVT, and 13 (9 percent) of atypical form. During the ablation, 5.3 percent with the typical form and 30.8 percent of the atypical form presented risk events for AVB. After the ablation, complications were a total AVB episode in one patient and a first-degree AVB episode in another in the typical group, and one first-degree AVB in the atypical group. All three episodes were preceded by risk events and resulted in permanent nodal injury. CONCLUSION: Patients with atypical NAVT presented higher percentages of risk events for atrioventricular block than did patients with the typical form (p=0.021).A careful observation of retrograde conduction during JET episodes is vital in order to avoid permanent damage in AV nodal conduction, such as TAVB, after the ablation procedure.

O desfibrilador externo semi-automático na parada cardiorrespiratória fora do hospital, quando cada segundo conta na sobrevivência / Automated external defibrilation, when every minute counts

Desde o final da década de 1960, os desfibriladores têm sido efetivos e apresentam sensibilidade de mais de 70 'por cento' a 80 'por cento' a reversäo de taquicardia ventricular ou fibrilaçäo ventricular. A falha na desfibrilaçäo sempre foi mais frequente na fibrilaçäo ventricular fixa, a qual é também chamada de assistolia grosseira. Entretanto, todas as modificaçöes técnicas presentes nos desfibriladores externos semi-automáticos têm permitido maior eficiência na desfibrilaçäo. Adicionalmente, com a diminuiçäo do peso, do tamanho e do custo, tais unidades podem ser disseminadas em ambientes públicos, permitindo acesso mais precosse à desfibrilaçäo. Näo devemos impedir que profissionais näo-médicos possam estar aptos a utilizar um dos desfibriladores externos semi-automático e liberar um choque terapêutico a tempo, tanto no ambiente intra como extra-hospitalar pois cada minuto é importante e preditror de sucesso ou recuperaçäo do paciente com parada cardiorrespiratória.

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

Säo apresentados os resultados imediatos e tardios, observados com a modificaçäo do nódulo sinusial via cateter, usando-se energia de radiofreqüência, em portadora de taquicardia sinusal inapropriada. O procedimento normalizou os níveis de freqüência cardíaca nas 24h seguintes e após seis seis meses, mostrando-se, portanto,efetivo e seguro. Apesar da reduçäo da freqüência cardíaca a níveis normais, houve manutençäo dos sintomas apresentados pela paciente, sugerindo que näo säo decorridos, exclusivamente, do processo taquicárdico.

Mecanismos e dinâmica da progressão dos episódios de bloqueio atrioventricular 2: 1 para bloqueio atrioventricular de alto grau / Mechanisms and dynamics of episades of progression of 2:1 A-V block to high degree A-V

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.

Terapia ablativa do flutter atrial tipo I com radiofreqüência / Type I Atrial Flutter Ablation Therapy with Radiofrequency

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.

Ablaçäo por radiofrequência de taquicardia supraventricular incessante por via anômala de conduçäo retrógrada decremental / Radiofrequency Ablation of Incessant Supraventricular Tachycardia Due to Decremental Retrograde Conduction Via Anomalous Pathways

Woman, 46 years-old with incessant supraventricular tachycardia and tachycardiomyopathy. The diagnosis of a concealed retrograde long conduction time accessory pathway was obtained with the delay of the next atrial activation by delivering a ventricular premature beat during His bundle refratoriness. During electrophysiologic investigation the earliest atrial activation was found to be within the coronary sinus ostium. Two 25 watts applications of radiofrequency were followed by the interruption of the incessant supraventricular tachycardia. The patient has remained symptom free without recurrence for 60 days. Radiofrequency was effective for the treatment of this tachycardia