The sinus node electrogram in patients with and without sick sinus syndrome: techniques and correlation between directly measured and indirectly estimated sinoatrial conduction time.

Abstract

SUMMARY Sinus node electrograms (SNEs) were recorded in 44 patients using a standard quadripolar electrode catheter (USCI #6) with 10-mm interelectrode distance. In 23 patients, the catheter was positioned at the junction of the superior vena cava (SVC) and right atrial (RA) wall so that the concave curve of the catheter was facing the concave surface of the RA wall. The distal poles of the catheter were close to but not in direct contact with the RA endocardium underlying the anatomic location of the sinus node (method 1). In 21 patients, the catheter was looped in the RA and advanced to the junction of the SVC-RA wall so that the distal poles of the catheter were in direct contact with the RA endocardium underlying the area of the sinus node (method 2). Stable SNEs could be obtained in 10 of 23 patients (43%) by method 1 and in 18 of 21 (86%) by method 2. SNEs by both methods showed two negatively directed deflections (diastolic and upstroke slope of the sinus node) of low frequency and amplitude occurring after the deflections of the T and U waves but before the P wave and intraatrial electrograms from various atrial sites. Unlike method 1, atrial activation by method 2 was characterized by an atrial injury potential. SNEs by method 2 were more stable and less prone to baseline drifts.Carotid sinus massage performed in 10 patients resulted in prolongation of the onset of the upstroke slope to atrial activation. In one patient, it resulted in marked first-degree sinoatrial block. SNEs were recorded in one patient during and after a run of spontaneous atrial flutter. After termination of atrial flutter, sinoatrial conduction time (SACT) prolonged for the first postflutter sinus beat and normalized by the third sinus beat.Direct SACTwas assessed on the SNE in all 28 patients, 12 of whom had sick sinus syndrome (SSS). SACT was also estimated indirectly by continuous pacing in 28 patients and by premature stimulation in 20 patients. Direct SACT was significantly (p < 0.001) longer in patients with SSS (135 30 msec, mean SD) than in patients without SSS (87 12 msec). There was a good correlation between direct SACT and SACT by continuous pacing (r = 0.843, n = 28) and direct SACT and SACT by premature stimulation (r = 0.778, n = 18). However, in certain patients, there were appreciable differences and direct SACTwas longer than estimated SACT by continuous pacing or premature stimulation. We conclude that (1) the success rate of stable SNEs with no appreciable baseline drift is increased with direct contact of the catheter with atrial endocardium underlying the sinus node area (method 2); (2) carotid sinus massage results in depression of sinus node automaticity and prolongation of SACT; (3) direct SACT is significantly longer in patients with SSS and can separate most patients with from those without SSS; and (4) there is a good correlation between direct SACT and indirectly estimated SACT, although the latter underestimates the actual SACT.UNTIL RECENTLY, direct sinus node recordings were not possible in man. Thu...

Comparison between intracellular and extracellular direct current recordings of sinus node activity for evaluation of sinoatrial conduction time.

“…Results of later studies, however, showed longer values of sinoatrial conduction time measured by DC electrograms and a good correlation with values obtained by atrial pacing methods. 6 Our study is the first to systematically map sinoatrial spread of activation with intracellular and extracellular electrodes. A major problem for measurement of sinoatrial conduction time in previous studies was the difficulty to precisely determine the onset of the upstroke slope in the DC electrogram.…”

Low-frequency extracellular potentials recorded from the sinoatrial node

“…Any difference in transmembrane potential between electrodes was first introduced into clinical electrophysiolelectrically coupled cells would, therefore, cause a current ogy in the beginning of 1980s [1][2][3][4]. This technique was through the cell interior, across the cell membrane and expected to have an advantage over indirect atrial pacing along the extracellular conductors, giving rise to a voltage methods in assessment of the conduction disturbance from gradient in the extracellular environment.…”

“…This filter setting is 2. Methods comparable to those employed in clinical electrophysiology to record extracellular SA node potentials [1][2][3][4][5][6][7]. This investigation conforms with the Guide for the care Activation time at the recording site was identified by the and use of laboratory animals published by the US initial negative deflection in each electrogram.…”

Holter monitoring, sinoatrial conduction time, prognosis

“…Final multivariate Cox regression models for events occurring during the follow-up: sinus node disease, pacemaker implantation and death. Entry variables are: age, gender, structural heart disease, and baseline sinoatrial conduction time (SACT) value > 150 ms. methods of SACT measurement (both Strauss' and Narula') with directly recorded SACT have shown a good correlation of the results obtained from these methods in patients without and with sinus node dysfunction [8][9][10]. A comparison of SACT values derived from 24-h Holter monitoring with SACT estimated by the Strauss' method during invasive electrophysiological testing was also performed in our study in a series of 52 patients referred to electrophysiological testing as a part of a diagnostic work-up.…”