A new method for measurement of sinoatrial conduction time.

Abstract

This study describes a new method (NM) for estimation of sinoatrial conduction time (SACT), which utilizes constant atrial pacing (AP) instead of the premature atrial beats (PABs) used in the method reported in 1973 by Strauss et al. The SACTs were obtained by both methods in 20 patients. The SACT by the Strauss method (SM) was calculated as A2A3 minus A1A1. The NM consists of high right AP for a train of eight consecutive beats at rates less than or equal to 10 beats/min faster than the sinus rhythm. The interval between the last paced atrial electrogram (Ap) and the first escape atrial electrogram (A) of sinus origin (Ap-A) was measured along with several post pacing sinus cycles. The SACT by the NM was calculated as follows: SACT = Ap-A minus A1A1. The effect of AP at higher rates was also analyzed. In two patients, the SACT with the SM could not be defined, as all the A2A3 intervals were fully compensatory; with the NM the SACT was 217 and 320 msec. In the remaining 18 patients the SACT was obtainable by both methods. With SM, the SACT ranged 105--452 msec (mean 219 +/- 102 SD) and with the NM it was 85--492 msec (mean 201 +/- 112 SD), and the difference was statistically significant (P = 0.0162). The coefficient of correlation between the two methods was r = 0.97. During AP at faster rates, a rate related increment in Ap-A intervals and also post pacing sinus cycles was noted. This study describes a new and simple method for measurement of SACT in man.

New application of direct sinus node recordings in man: assessment of sinus node recovery time.

“…Sinus node depression ( + 80 to + 680 msec) was observed after pacing at cycle lengths of 700, 400, and 300 msec, whereas there was no change in sinus node automaticity after pacing at a cycle length of 500 msec. 30 Conventionally SNRT is measured from the last paced beat to the atrial electrogram in the region of the high right atrium. SNRT thus obtained was taken as a measure of sinus node automaticity.…”

Acceleration of sinus rhythm during slow-rate atrial pacing.

“…The pacemaker site was identified by extensive mapping of the endocardial sinus node area using 40-60 intracellular impalements as previously described.3 Dominant pacemaker fibers exhibit marked phase 4 depolarization, a smooth transition between phase 4 and phase 0 of the action potential, and the longest latency between activity of the cell and the atrium.…”

“…I Subsequent experimental studies have shown several inherent inadequacies of this technique.2 3 Using constant atrial pacing at rates slightly faster than sinus rhythm, Narula et al 4 found a simpler and quicker approach for measuring SACT. Data obtained by constant atrial pacing have been used to characterize sinus node function in man5-7 and also have been compared for validation with the results of independent method of direct extracellular direct-current recordings of sinus node activity.…”

Cardiovascular effects of a new phenoxyalkylamine derivative, 2-isopropyl-5-(3-(2-methoxyphenoxy)propylamino)-2-(3,4,5-trimethoxyphenyl)valeronitrile fumarate (HV-525), in cross-circulated dog atrial preparations.

“…Developed tension was isometrically measured with a force displacement transducer (Nihon Kohden AP620G) connected to a part of the atrial muscle with a silk thread. Sinoatrial conduction time (SACT) was estimated using constant atrial pacing consisting of a train of 8 cycles at a rate 10 beats/min faster than the spontaneous rate (Narula et al, 1978). 6) Kobayashi et al7) reported that there was a good correlation between the SACT measured by the continuous atrial pacing method and by the premature atrial stimulation method (Strauss et al, 1973)8) using the isolated dog atrial preparation.…”