RESUMO
His bundle and right ventricular apical endocardial electrograms were recorded in 18 patients, ages five to 17 years, of whom ten had atrial septal defect of the secundum type and eight had mild aortic stenosis. The H-RVA interval was assumed to approximate conduction time from the level of the His bundle along the RBB to the site of earliest activation in the right ventricle at the RVA. The H-V interval was normal in all patients (less than or equal to 40 msec). All patients in the ASD group had an rsR' or rSr' pattern in Vl with a mean duration of 99 +/- 9 msec (86 to 116 msec); the mean duration of the H-RVA intervals was 54 +/- 6 msec in this group. In patients with AS, the surface electrocardiograms were normal, with a mean QRS duration of 82 +/- 8 msec (70 to 95 msec); the H-RVA intervals averaged 52 +/- 6 msec. The difference in the H-RVA intervals in the two groups was not statistically significant (P greater than 0.50) despite the fact that patients with ASD had significant prolongation of QRS duration (P greater than 0.001). Moreover, when functional RBB block was induced by premature atrial stimulation in the ASD group, the prolongation of QRS duration was accompanied by an increase in H-RVA interval, indicating relatively intact function of the RBB. It is concluded that the rsR' or rSr' pattern in ASD is likely to be a manifestation of right ventricular overload rather than a true conduction delay in the RBB.
Assuntos
Bloqueio de Ramo/etiologia , Eletrocardiografia , Comunicação Interatrial/etiologia , Adolescente , Estenose da Valva Aórtica/fisiopatologia , Fascículo Atrioventricular/fisiopatologia , Bloqueio de Ramo/fisiopatologia , Criança , Pré-Escolar , Eletrofisiologia , Comunicação Interatrial/fisiopatologia , HumanosRESUMO
The analysis of the common bundle and of the ventrical filtered electrograms has incrased our knowledge of the intraventricular conduction following the simulation of the PVS as well as the different types or reciprocating that can be produced by premature beats. 2. The positive QRS complexes in V1 produced from PVD by St2 can be explained as a greater degree of incomplete recuperation of the right ventricular wall than in the interventricular septum. In contrast with what happened in the basal beats, where the front took longer to reach the TSVD than the VI. 3. The refractarines of the transitional tissues that serve as the phisiological banier was longer than the banal myocardium. The intraventricular propagation, and therefore the morphology and direction of QRS, depended of this one; while the moment of arrival of activation retrogradly to the common bundle was conditioned by the transitional tissues. 4. Episodes of ventricular taquicardies with QRS positive complexes in V1 can be due to a re-entry throught the bundle branches or in (or around) an area that has been recently injured.
Assuntos
Fascículo Atrioventricular/fisiologia , Eletrocardiografia , Sistema de Condução Cardíaco/fisiologia , Função Ventricular , Estimulação Elétrica , Humanos , Taquicardia/diagnósticoRESUMO
His bundle electrograms recorded during atrial stimulation with the extrastimulus technique permitted the analysis of the so called gaps in bundle branch conduction. Three different types of gaps were identified each with a distinct electrophysiological mechanism. In type I gap a CLBBB pattern disappeared at shorter coupling (A1-A2) intervals because the more premature impulses encountered a greater degree of the delay at the A-V node therefore reaching the left bundle branch after its effective refractory period had ended. During this part of the cycle the H1-H2 were longer and H2-V2 intervals shorter than when CRBBB was present. In type II gap a CRBBB pattern disappeared at shorter coupling intervals because the premature impulses met a greater delay in the proximal portions of the His-Purkinje system. In consequence, they arrived at the right bundle branch when its effective refractory period had expired. When this occurred the H1-H2 interval were shorter and the H2-V2 longer than those at which CRBBB had been present. The patient with type III gap had CLBBB. A-V conduction was possible through the right bundle branch very late in the cycle. However, it could not occur at shorter coupling intervals finally reappearing at even shorter coupling intervals. True supernormal conduction or vagal pulsatile discharges could have been present. Yet, we favor, as the most likely possibility, the existence of 2:1 phase 4 block with latent or abortive escapes not recorded in the surface leads.