ATRIAL PACING TO ESTIMATE SINOATRIAL CONDUCTION TIME IN CHILDREN

Abstract

Studies in adults have shown a strong correlation between indirect total sinoatrial conduction time (TSACT) using extrastimulus (ES) and atrial pacing (P). No data using P in children exist. To compare P vs. ES, and to examine the effect of different P rates in children, we studied 55 pts.—age 0.2-18.5 yrs—using P and ES. Because children exhibit a wide range of age-related cycle lengths, P was performed using a train of 9 paced right atrial beats normalized to 88-92% (90%),(n=32) or 93-97% (95%),(n=38) of the sinus cycle length (SCL); 15 patients had P determined at both paced cycle lengths. Sinus node (SN) suppression was estimated by recovery CL/SCL × 100(%)(REC). In 13/55 pts ES TSACT was indeterminant. There was no significant difference (X̄±SD) in SCL (576±152 vs. 574±149 msec), REC (101.9±1.7 vs. 104.4±6.1%), and TSACT (128±40 vs 126±74 msec) (n=26) between ES and P at 90%SCL. ES vs P TSACT correlation was r=0.82 (p<0.001). Similarly with P at 95%SCL, there was no significant difference in SCL (572±129 vs. 576±125 msec), or REC (101.3±1.9 vs. 102.9 ±5.7%); however, TSACT was greater by ES than P (137±38 vs. 105 ± 58 msec; p<0.001) (n=29) with r=0.82 (p<0.001). Intrapatient variation was wide at both pacing rates: coefficient of variance was 33% and 42%, respectively. We conclude that TSACT by P in children, as in adult studies, shows wide intrapatient variability but corresponds well with ES. TSACT by P at 90%SCL approximates ES TSACT in children better than P at 95%SCL perhaps related to more complete SN capture and less pacemaker focus shift. For TSACT by P in children we recommend pacing at 90%SCL.

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