RESUMO
Sinus and atrioventricular (A-V) nodal reentry are shown to coexist in the same patient, and the following conclusions are drawn: (1) Reentry at one nodal site may mask reentry at the other nodal site, (2) concealed reentry at either site may become manifest reentry under the appropriate conditions, (3) manifest sinus nodal reentry may alternate with manifest A-V nodal reentry, and (4) a Wenckebach type phenomenon manifest in the A-V node and concealed in the sinus node may in some instances be the basis for coexistent sinus and A-V nodal reentry in man.
Assuntos
Nó Atrioventricular/fisiopatologia , Eletrocardiografia , Sistema de Condução Cardíaco/fisiopatologia , Nó Sinoatrial/fisiopatologia , Taquicardia/fisiopatologia , Idoso , Arritmia Sinusal/complicações , Cateterismo Cardíaco , Bloqueio Cardíaco/complicações , Humanos , Masculino , Marca-Passo Artificial , Taquicardia/complicações , Taquicardia Paroxística/fisiopatologiaRESUMO
Sinus node re-entry (SNR) usually appears as a single beat. Tachycardias (SNRT) consistent with sustained SNR were seen in six patients and were initiated by premature stimulation of the high right atrium (six patients) and coronary sinus (four patients), and after continuous pacing from the high right atrium (four patients) or right ventricle (one patient) at rates of 130 to 200 per minute. During SNRT: (1) atrial beats exhibited a high-to-low atrial activation sequence, (2) the P-waves were similar in morphology to P-waves during sinus rhythm, and (3) re-entry in the A-V node or at the site of stimulation could be excluded. The cycle length of SNRT ranged from 625 to 320 msec. and SNRT either terminated spontaneously (six patients) or after premature atrial capture and/or vagal maneuvers (two patients). The electrophysiologic characteristics of SNRT and differentiation of SNRT from A-V nodal re-entry are discussed.
Assuntos
Nó Sinoatrial/fisiopatologia , Taquicardia Paroxística/fisiopatologia , Idoso , Nó Atrioventricular/fisiopatologia , Cateterismo Cardíaco , Eletrocardiografia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Marca-Passo ArtificialRESUMO
The effect of digoxin on sinus reentry was examined in 20 open chest mongrel dogs during infusion of digoxin at a rate of 2.5 mu g/kg per min. The extrinsic cardiac nerve supply was removed acutely in 10 dogs and was left intact in the remaining 10 dogs. Sinus nodal reentry was relatively unaffected by digoxin in 18 of 20 dogs. In these 18 dogs, digitalis toxicity developed before reentry was abolished and was manifested as increased atrial and ventricular automaticity in 14 and as advanced atrioventricular (A-V) block in four. In the remaining two dogs, sinus nodal reentry was relatively sensitive to digoxin and was abolished before toxicity became manifest as advanced A-V block. The knowledge of the relative insensitivity of sinus nodal reentry to digoxin, at least in this experimental model, contrasts with the previously reported sensitivity of sinus nodal reentry to quinidine, and may be important in the management of sinus nodal reentry in man.
