Wavelength and atrial vulnerability: an endocavitary approach in humans.

If atrial vulnerability parameters are well defined, wavelength (WL) measurement (conduction velocity x refractory period), has never been assessed through an endocavitary electrophysiological exam. We investigated 30 patients (14 female, mean age 63.4 +/- 13 y.o.), 10 with paroxysmal atrial fibrillation (PAF group), 10 with ischemic cerebral injury (ICI group) by comparison with 10 controls (C group). The upper to lower right atrium conduction time and velocity were measured in the right atrium with a decapolar electrode catheter applied along the free wall. Others parameters correlated to atrial excitability were also taken into account: effective (ERP) and functional refractory periods (FRP); spontaneous or paced atrial electrogram (A1) or extrastimulated atrial electrogram (A2) widths, ERP/A2 ratio, provocative atrial testing. Measurements were taken in sinus rhythm and in 600-460 ms paced cycle lengths. If ERP, FRP, A1 widths are the same in the 3 groups, PAF and ICI groups have a significant increased conduction time and lower conduction velocity, leading to a shorter A1 WL during 600 and 460 ms paced rhythms (p < 0.05) and A2 WL during 460 ms paced rhythm. The provocative testing was positive in 60% of PAF and ICI groups, and there is a significant correlation between arrhythmia induction and 600 ms A1 WL or 460 ms A2 WL. This electrophysiological study suggests the possibility of an approach in humans of wavelength concept and proves the presence of correlation between a short wavelength and atrial spontaneous or induced arrhythmias. A no-arrhythmia band (A1 WL > 17 cm during 600 ms paced rhythm, A1 WL > 16 cm or A2 WL > 12 cm during 460 ms paced rhythm) and a fibrillation-band (A1 WL < 12 cm during 600 and 460 ms pacing, A2 WL < 7 cm during 460 ms pacing) can be defined. Therefore, the ICI group has the same atrial pattern as the AF group.