[Direct measurement of sinoatrial conduction time in man. Correlation with sinus cycle length]

Recent reports have shown that it is possible to record sinus node potential (SNP) using a transvenous electrode catheter technique in animals and in man. We applied similar techniques to record sinoatrial activity in 24 normal subjects and in 6 patients with sick sinus syndrome. We used bipolar recordings, with one interelectrode distance of 1 cm, low-pass filters of 0.1-50 Hz and high-amplification (up to 100 microV/cm). Validation of the source of the sinus node electrograms (SNE) was obtained by using ad hoc criteria. Like SNE recorded in animals, human SNE shows a smooth, low-frequency upstroke slope that begins before and merges into atrial activation. Sinus node potential is separated from preceding T wave by an isoelectric plateau. In 24 subjects with normal sinus node function, the directly recorded sinoatrial conduction time (D-SACT) was 82.9 +/- 17.9 msec. Correlation with the SACT estimated by Narula's method was excellent (r = 0,84). In 12 patients with sinus arrhythmia on SNE, SACTs were directly measured as were the associated P-P intervals. When SACT at each sinus cycle length (SCL) was plotted against SCL for all subjects grouped together, the average change of SAT per 100 msec change of SCL was 15 msec. In 6 patients with sick sinus syndrome, D-SACT was 150.4 +/- 67.4 msec. When SACT at each SCL was plotted against SCL, the average change of SACT per 100 msec change of SCL was 39 msec. In the same patients the SACT estimated by Narula's method was 129 +/- 17 msec.