[Lengthening of the direct sinoatrial conduction time: a criterion of sinus node dysfunction]. / L'allongement du temps de conduction sino-auriculaire direct: un critère de dysfonction sinusale.

In order to determine the significance of prolongation of the direct sinoatrial conduction time (DSACT), an attempt was made to record the sinus node potential in 110 patients which was successful in 84 cases. The DSACT was normal in 45 cases (Group A) and prolonged (over 130 ms) in 39 cases (Group B). The symptomatology, standard ECG and the results of investigation of sinus node function by atrial stimulation of the two groups were compared. The DSACT was prolonged in all 13 patients with paroxysmal sinoatrial block or the sick sinus syndrome, in 71% of 15 patients with permanent sinus bradycardia, in 88% of 22 patients with a corrected sinus node recovery time of over 525 ms, in 82% of 38 patients with a sinoatrial conduction time estimated by the extrastimulus method of over 130 ms or an abnormal zone II, in 80% of 39 patients with sinoatrial conduction times estimated by Narula's method of over 130 ms; therefore, 87% of the 35 patients with probable sinus node dysfunction had long DSACT. On the other hand only 2 out of 35 patients (6%) with apparently normal sinus node function had prolonged DSACT. These results indicate that prolongation of the DSACT is a sensitive and specific criterion of sinus node dysfunction. In cases of sinus node dysfunction dizziness and/or syncope without any known cause were common complaints in patients in Group B but absent in patients in Group A. A prolonged DSACT could be of prognostic significance in sinus node dysfunction.

Sinus node electrogram recording in 59 patients. Comparison with simultaneous estimation of sinoatrial conduction using premature atrial stimulation.

Directly measured sinoatrial conduction time was compared with sinoatrial conduction time assessed simultaneously by the single premature atrial stimulus technique in 59 patients: 20 with normal sinus function, 35 with sinus dysfunction, and four with sinus bradycardia but negative indirect methods. In patients with normal sinus function direct sinoatrial conduction time was 102.5 +/- 34 ms (mean +/- 2 SD) and was identical to indirect sinoatrial conduction time. Neither direct sinoatrial conduction time in the basal and return cycle, nor post-return and basal cycle lengths were different. Sinoatrial and atriosinus conduction durations were similar. In sinus dysfunction direct sinoatrial conduction time (average 160 +/- 47 ms) was longer than in normal sinus function. Prolonged direct sinoatrial conduction time may therefore be considered as a criterion of sinus dysfunction. In sinus dysfunction no significant correlation was observed between direct and indirect sinoatrial conduction times. Direct sinoatrial conduction time was equal to (17 patients), longer than (12 patients), or shorter than (six patients) indirect sinoatrial conduction time. These differences can be explained by delayed or incomplete premature depolarisation penetration into the sinus node rather than by the classical pacemaker shift.

[Evaluation of the sinoauricular conduction time: comparison of the recording of the sinus potential and Narula's method]. / Evaluation du temps de conduction sinoauriculaire: comparaison de l'enregistrement du potentiel sinusal et de la méthode de Narula.

The sino-atrial conduction time, measured by Narula's method (SACTN) is compared to the direct sino-atrial conduction time measured by recording the sinus potential (SACTD) in 55 patients, 20 with normal sinus function and 35 with sinus dysfunction. In the absence of sinus dysfunction, SACTN and SACTD are not significantly different and a significant but mediocre correlation (r = 0.57) is observed between the two parameters. Major discordances between the two methods are seen in 4 patients. In cases with sinus dysfunction, there was no correlation between SACTD and SACTN; SACTN is close to SACTD in 12 patients, but much shorter in 11 patients and much longer in 10 patients. These discordances raise the problem of the penetration of the sinus node by the extrastimulus in Narula's method. This method does not seem capable of giving a reliable evaluation of the duration of sino-atrial conduction.