Is age correlated with dynamic atrial decremental conduction properties?

Atrial fibrillation (AF) has been associated with premature beats and decreased atrial conduction velocities. On the other hand, prevalence of AF is increased in the elderly. The aim is to evaluate and analyze the relation between age, atrial size and a new index of dynamic interatrial conduction time (iaCT) in a homogeneous population of patients (pts) with structurally normal heart without AF.

45 patients (pts) without structural heart disease aged 53 +/- 20 years referred for electrophysiologic study were analyzed. To examine the atrial electrophysiologic characteristics we studied interatrial conduction time (iaCT), double potentials and fragmented atrial activity during premature stimulation of high right atrium; prior to investigation, all antiarrhythmic drugs were withdrawn for an appropriate period of time. The following parameters were assessed: baseline iaCT (iaCTb) between high right atrium (HRA) and distal coronary sinus (CS), iaCT during HRA pacing S1S1 600ms (iaCTS1), maximum prolongation of iaCT during S2 and S3 delivery (iaCTS2, iaCTS3). We calculated a derived parameter: maximum prolongation iaCT/decremental index (DI)= iaCT S3-ia CTS1/iaCTS1%. The following echocardiograhic parameters were assessed: left atrial dimensions and surface (LAs), right atrial dimension and surface (RAs), total atrial surface (TAs=LAs+RAs) and left atrial volume (LAv) calculated using ellipse formula.

iaCT ranged from 42 to 87ms; DI ranged from 16 to 52%. Simple regression analysis demonstrated a statistically significant linear correlation between the age of pts and HRA DI (r = 0.76, r2 = 0.55, p <0.0001). A trend toward a significant correlation was found between TAs and DI (r=0.64, r2=0.41, p<0.0001) LAv and DI (r=0.59, r2=0.35, p<0.0001). No significant correlation was found in this group between age and iaCT. Atrial double potentials and fragmentated electrograms were recorded using HRA stimulation in CS leads in 7 pts (15%) all aged >35 years. Pts were divided into two groups: 17 pts with normal electrophysiologic findings and 28 pts with junctional reentrant tachycardia. There were no significant differences between subgroups concerning the main studied parameters.

This study shows a direct better correlation for age than atrial size in the relation with the dynamic behaviour interatrial conduction, suggesting that higher incidence in AF in the elderly might be also a consequence of the higher incidence of atrial conduction disturbances.