Quantitative relationship between atrial refractoriness and the dispersion of refractoriness in atrial vulnerability.

We investigated the quantitative relationship between the atrial refractory period and the dispersion of refractoriness with respect to atrial vulnerability in 19 adult mongrel dogs. The atrial effective refractory period (AERP) was measured at the sinus node area (SNA), the low posterior right atrium (LRA), and the distal coronary sinus. The study was performed under the following conditions: (1) control status; (2) hypothermia (30 degrees C); (3) vagus nerve stimulation; and (4) a combination of (2) and (3). The subjects were separated into two groups: atrial fibrillation (AF) (+) group (n = 23), which developed AF by atrial extrastimulus due to increased vulnerability, and AF (-) group (n = 39), which did not develop AF. The mean AERP was 97 +/- 21 msec (mean +/- SD) in the AF (+) group and 124 +/- 23 msec in the AF (-) group, with a significantly shorter refractory period seen in the former (P less than 0.001). The dispersion of refractoriness was 59 +/- 24 msec in the AF (+) group and 29 +/- 18 msec in the AF (-) group, with a significant increase noted in the former (P less than 0.001). On X-Y coordinates (where X denotes the AERP, and Y denotes the dispersion of refractoriness) the data from the AF (+) group were clustered in the upper left region of the graph while the data from the AF (-) group were clustered in the lower right region. These two groups were separated by a linear equation of Y = 0.86X - 57 with a predictability of 90.3%.(ABSTRACT TRUNCATED AT 250 WORDS)