Avaliação da atividade elétrica atrial em pacientes submetidos ao tratamento cirúrgico da valvopatia mitral

INTRODUCTION: The selection of the surgical approach to the mitral valve is a critical factor in obtaining good exposure and minimizing lesions of the surrounding structures. The classical right lateral subseptal access may sometimes provide difficult exposure, so that alternative approaches are used whose effects on atrial electrical activity are contradictory. OBJECTIVE:To standardize an investigative method to evaluate heart electrical activity post-op. METHODS: Ten consecutive adult patients with mitral valve disease were operated on. Surface electrocardiogram and continuous electrocardiographic monitoring (Holter system) pre and post-op., and epicardical cardioestimulation post-op. were used to study cardiac electric activity. RESULTS: There was no mortality. All patients with sinus rhythm presented supraventricular ectopia, with episodes of supraventricular tachycardia in 57%, atrial flutter in 10%, and junctional rhythm in 10%. All patients presented ventricular ectopia, with a low incidence in 70% of them and with unsustained ventricular tachycardia in 30%. During the postoperative period there was a 40% rate of new supraventricular arrhythmias (atrial fibrillation, junctional rhythm, low atrial rhythm, and paroxistic supraventricular tachycardia), with no ventricular arrhythmias. Post-op. sinus node function was preserved. There was a significant reduction of supraventricular ectopia, with reversal of atrial fibrillation to sinus rhythm in one patient. Although there was a significant reduction in left atrium size post-op, P wave duration, as well as ventricular ectopia rate remained unchanged. Interatrial conduction time correlated with left atrium size measured pre and post-op. CONCLUSION: The methods proved useful to evaluate atrial electric activity in patients operated upon by the classic subseptal access, thus permitting future comparisons with other surgical approaches to the mitral valve.

INTRODUÇÃO: O acesso cirúrgico por esternotomia mediana e atriotomia subseptal clássica pode, em certos casos, resultar em má exposição da valva mitral. Incisões atriais alternativas otimizam a exposição da valva mitral mas podem interferir na atividade elétrica atrial pós-operatória. OBJETIVO: Padronizar método para investigar a atividade elétrica atrial para emprego em estudos comparativos de diferentes atriotomias em cardiopatas sumetidos à cirurgia cardíaca. MÉTODOS: Análise com eletrocardiograma convencional e de 24 h (sistema Holter), pré e pós-operatória, e cardioestimulação epicárdica pós-operatória pelo método de Narula, em 10 pacientes submetidos à correção de valvopatias mitrais. RESULTADOS: No pré-op., os pacientes em ritmo sinusal apresentaram ectopias supraventriculares, com episódios de taquicardia supraventricular em 57% dos casos, "flutter" atrial em 10% e ritmo juncional em 10%. Todos apresentaram ectopias ventriculares, de baixa incidência em 70% dos casos, e taquicardia ventricular não sustentada foi detectada em 30% dos pacientes. No pós-operatório, houve 40% de novas arritmias supraventriculares (fibrilação atrial, ritmo juncional, ritmo atrial baixo e taquicardia supraventricular paroxística), mas não ocorreram arritmias ventriculares. No pós-op. a função do nó sinusal não se alterou, ocorreu redução significativa das ectopias supraventriculares, com reversão de FA para ritmo sinusal em 1 paciente, mas não houve redução significativa das ectopias ventriculares. O tempo de condução inter-atrial correlacionou-se com o tamanho do átrio esquerdo. CONCLUSÃO: A metodologia mostrou-se adequada e segura, e poderá ser empregada na comparação de diferentes incisões atriais para exposição valvar mitral.

Electrophysiologic Properties of the Atrium in Patients with Chronic and Paroxysmal Atrial Fibrillation

BACKGROUND: trial fibrillation (AF) causes electrical remodeling of the atrium that plays an important role in increasing atrial vulnerability and the perpetuation of AF. The regional variation and heterogeneities of AF-induced electrical remodeling in patients with AF remain unclear. The purpose of present study was to test the hypothesis that regional heterogeneity of the atrial electrical properties including sinus node dysfunction is more apparent in patients with chronic AF than in patients with paroxysmal AF. METHODS: The study group consisted of chronic AF (CAF, n=19), paroxysmal AF (PAF, n=19) and control group (CON, n=13). Monophasic action potential duration 90% (MAPD90) and atrial effective refractory period (AERP) were measured at 9 different sites in the right atrium using MAP catheter. Dispersion of MAPD90 and AERP were calculated from the difference between the maximum and minimum value at 9 sites, respectively. Intra-atrial conduction time (IACT) was calculated from the distance between the earliest activation and the latest one of the electrograms by 20-pole steerable catheter with 2-mm interelectrode distance which was positioned along the tricuspid annulus anterior to the crista terminalis. To evaluate sinus node function, post shock sinus node recovery time (PSRT) was measured. A rate corrected PSRT (PSRTc) was calculated from the difference between PSRT and basic sinus cycle length. RESULTS: MAPD90 significantly shortened in patients with CAF (227.0+/-32.6 ms) compared with PAF (246.8+/-38.3 ms, p<0.05) and CON (239.1+/-39.3 ms, p<0.05), but AERP was not significantly different among 3 groups. The regional changes and dispersion of MAPD90 and AERP in patients with CAF did not differ from those of PAF and CON. IACT was prolonged in CAF group (73.8+/-22.5 ms) compared with PAF (58.2+/-8.0 ms, p<0.05) and CON groups (51.6+/-12.3 ms, p<0.05). IACT in CAF group (73.8+/-22.5 ms) was significantly prolonged compared with CON groups (51.6+/-12.3 ms, p<0.05) and was longer than that of PAF groups (58.2+/-8.0 ms) without statistical significance. PSRTc was longer in CAF group (758.3+/-525.8 ms) than in PAF group (209.5+/-125.0 ms, p<0.05). CONCLUSION: Electrical changes defined as shortened MAPD90, prolonged IACT and PSRTc were more apparent in patients with CAF compared with PAF. However, these were neither accompanied by the regional variations nor dispersion of refractoriness of the atrium. These findings suggest that regional heterogeneities of electrical properties are not related to the chronicity of atrial fibrillation.

Studies of Determination of Sinus Node and A-V Conduction Systen Function in Children by Transesophageal Atrial Pacing / 昆明医科大学学报

The study group consisted of 50 normal children. The determination of Sinus node func- tions included SNRT, CSNRT, SNRTI, SACT, IHR and autonomic nervous system tone. The A-V conduction system function was evaluated by measurement of wenckeback point and 2:1 point of A-V conduction system. Each parameter was determined before and after com- bined autonomic blockade. Before combined blockade, the Wenckeback point and 2:1 point appeared at the HR of 175-220 bpm were 90% of the cases and 98% of the cases respectively, after combined block- ade, they were 98% of the cases and 100% of the cases respectively. It also showed the domi- nant vagus had effect on A-V node.