Quantification of spatial inhomogeneity in conduction and initiation of reentrant atrial arrhythmias

Abstract

In isolated superfused left atria of the rabbit, inhomogeneity in conduction was quantified using the activation times measured with a high-density mapping system. At each recording site, the maximal difference with neighboring activation times (i.e., phase difference) was calculated. Local phase differences were plotted in a phase map, revealing the spatial distribution of inhomogeneities in conduction, and from each map a total index of inhomogeneity was calculated. During slow pacing (2 Hz) local differences in conduction velocity, depending on the direction of propagation, were found already. Inhomogeneity in conduction increased significantly during single early premature beats (inhomogeneity index increased from 2.3 to 3.1; P less than 0.001). The application of multiple premature beats further increased inhomogeneity in conduction, whereas rapid pacing induced the highest level of inhomogeneity (inhomogeneity index 5.3; P less than 0.001). An analysis of the spatial distribution of maximal phase differences revealed that during premature beats inhomogeneities in conduction were limited to an area of 6 mm around the point of origin of the premature impulse, whereas during rapid pacing inhomogeneities in conduction were found throughout the whole preparation. Phase maps constructed during the initiation of reentrant tachyarrhythmias showed that reentry occurred at sites with the highest phase differences. Quantification of spatial inhomogeneities in conduction is a useful tool to evaluate the vulnerability of the myocardial substrate for reentrant arrhythmias.

Development of a Substrate of Atrial Fibrillation During Chronic Atrioventricular Block in the Goat

“…This increased spatial heterogeneity in conduction may support the perpetuation of AF. 7 Interestingly, interstitial fibrosis was not seen in the present model. Also, the expression of Cx40 and Cx43 was unchanged.…”

“…The heterogeneity index was expressed as the 95th percentile minus the 5th percentile of the phase difference distribution (p95Ϫp5) divided by the median phase difference (p50). 7 …”

“…Conduction times (between neighboring electrodes) and phase differences (largest difference in activation in a square of 4 electrodes) were plotted. 7 Local velocities of conduction were calculated from conduction vectors measured in surface areas of 2.4ϫ2.4 mm. 4 -6 Amount of heterogeneity in conduction was determined by analysis of distribution of conduction times, phase differences, and conduction velocities.…”

Promotion of Atrial Fibrillation by Heart Failure in Dogs

“…9 To evaluate spatial conduction inhomogeneities, phase maps were constructed based on previously reported methods. 10 Figure 2A shows activation during RAA pacing at a BCL of 150 ms in a control dog. For each electrode, the phase differences (activation time difference between the central electrode and each of the surrounding sites) were determined ( Figure 2B) and divided by interelectrode distances.…”

“…The variation coefficient (P 5-95 /P 50 ) was used as a heterogeneity index to express heterogeneity independently of CV, as previously described. 10 We calculated AF cycle length (AFCL) at each epicardial recording site by counting the number of activations over a 5-second recording. We assessed regional variability in AFCL by calculating the SD of the mean AFCL in each of the 8 zones in which ERP was measured directly, ie, RAA, RA-PW, RA-IW, RA-BB, LAA, LA-PW, LA-IW, and LA-BB (Figure 1).…”