Second-degree Wenckebach type AV block due to block within the atrium.

Abstract

Two patients with a history of paroxysmal supraventricular tachycardia were analysed by His bundle and intra-atrial recordings. The electrocardiogram showed sinus bradycardia in I patient and sinus bradycardia with sino-atrial Wenckebach in the other. The conduction times through the A V node and His Purkinje system were normal in both cases. The intra-atrial conduction time was slightly prolonged (55 msec) in one and normal (40 msec) in the other during normal sinus rhythm. In both cases with atrial pacing from high right atrium, the conduction time from the pacing impulse (PI) to atrial activation in the area of the A Vjunction (PI-A) progressively lengthened with increase in atrial pacing rate and finally classical second-degree Wenckebach type of block was manifested at cycle lengths of 460 and 465 msec. The pacing impulse to QRS interval (PI-R) showed a progressive increase before the blocked stimulus. The lengthening of the PI-R interval was due to progressive increase in the intra-atrial (PI-A) conduction time. In the dropped beats, thepacing impulse was notfollowed by an A deflection. This observation indicated Type I block within the atrium. Similarly, during induced premature atrial beats, the PI-A time progressively lengthened as the coupling interval was shortened. These findings were reproducible and were seen despite a fourfold increase in stimulus strength and changes in electrodes and site of stimulation along the lateral right atrial border. This study (I) shows second-degree Wenckebach block within the atrium; (2) supports the existence of sinoatrial Wenckebach; and (3) suggests the atrium as another possible site for re-entry and a cause for supraventricular tachycardia because of the degree of delay and block exhibited within the atrium.

Wenckebach cycle length: A novel predictor for AV block in AVNRT patients treated with ablation

“…A critical parameter obtained from atrial pacing is WCL, defined as the atrial pacing period at which AV nodal conduction degenerates to Wenckebach Rhythm 15 . Normal values range between 450 and 250 ms or 130 to 240 bpm in terms of HR 16 . Although more studies might be required to confirm this finding, our findings strongly suggest that WCL should be assessed in all patients treated with RFCA for AVNRT.…”

Ibutilide Induced Intraatrial Wenckebach Periodicity in the Neonatal Canine Heart

“…Previous examples of intraatrial Wenckebach periodicity have been reported in adults usually with documented intraatrial disease, clinical atrial tachycardias, or with evidence of extensive conduction system disease. [1][2][3][4][5][6][7] The neonatal hearts reported in this study were ostensibly "normal." Also, the puppies studied were obtained from two different litters, making a rare "familial" phenomenon or tendency to observe atrial Wenckebach periodicity "by chance" less likely.…”

Dissimilar atrial rhythms. A patient with interatrial block.

“…Early descriptions of the atrial Wenckebach phenomenon in man were made by Phibbs (1963), Scherf and Cohen (1964), and Schamroth (1967). Narula et al (1971Narula et al ( , 1972 documented the occurrence of intra-atrial Wenckebach block in man using intracardiac recordings. They reported patients with abnormal high right to low right atrial conduction times who showed progressive prolongation of this interval during atrial pacing.…”