Methods and Results
This study was approved by the Institutional Review Board and data was
obtained from nine consecutive patients with drug-refractory AF
undergoing a first time catheter ablation. Bipolar electrograms of the
left atrium (LA) were recorded using a 24 pole flat array catheter (HD
Grid, Abbott technologies, Mn, USA) prior to the ablation procedure. A
total of 7 specific anatomical locations were mapped in SR and during
AF: the anterior LA appendage , the ostium of each of the four PV’s, the
posterior wall and the lower septum. A shadow of the catheter location
was created to ensure standardization of the location during both SR and
AF. During AF mean peak-to-peak bipolar voltage amplitude were computed
in time periods of 1s, 3s, 10s, 20s, and 30s for AF and compared with a
single SR beat.
The comparison of continuous variables was assessed with ANOVA test.
Correlation between the mean amplitude recorded during AF with SR was
assessed with Spearman correlation coefficients, and robust linear
regression was performed to reduce outlier effect. A p-valve of less
than 0.05 was considered statistically significant. All analysis were
performed using Matlab R2018b.
A total of 4352 electrical points were recorded, 2104 during sinus
rhythm and 2248 during AF from 16 patients (mean age 64 +/- 8 years, 5/9
female; median duration of AF 7 (3-10) months). As shown in Figure 1 the
mean AFv was significantly lower compared to SRv (0.5536 ± 0.7767mV vs
1.1373 ± 2.0497, p < 0.001). There was a moderate to strong
correlation between SRv and AFv for all the different durations of
voltage acquisition: 0.698 for 1s, 0.601 for 3s, 0.892 for 10s, 0.715
for 20s, and 0.70963 for 30s. There was an excellent correlation between
the 10 second duration recording (r=0.892; p <0.0001) and the
Srv. This relationship was seen throughout all regions of the LA.
In our study the mean voltages recorded throughout the LA were lower
during AF than SR which is in keeping with a recent study in which the
voltage recorded during AF demonstrated a better correlation than SR
when compared with a DE-MRI of the posterior wall of the LA. [5]
This study also demonstrated that AF voltage recordings tend to
stabilize after a period of 4 seconds. For the first time we have found
a linear correlation between the voltage amplitude in SR and AF with
adequate temporal sampling in the most common locations for substrate.
The disorganized wavefront activation during AF results in variability
in every peak to peak voltage amplitude but mapping during a longer
period of time showed a good correlation with the electrograms in SR.