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475 NON-INVASIVE ASSESSMENT OF SUBSTRATE CHANGE AFTER WIDE AREA CIRCUMFERENTIAL ABLATION (WACA) FOR ATRIAL FIBRILLATION DP Redfearn, AC Skanes, LJ Gula, AD Krahn, R Yee, GJ Klein BACKGROUND: The demonstrated superiority of WACA may result from 'substrate modification' perhaps related to vagal denervation. We resolved to examine this prospectively and correlate with outcome.
London, Ontario
METHODS AND RESULTS: Heart rate variability (HRV) and signal averaged P wave (SAPW) data were derived from high resolution recordings ('Spiderview' ELA Medical) made in sinus rhythm immediately before and 24 hours after WACA for atrial fibrillation (AF). An 8mm catheter was used (power 50 - 60 watts and temperature 55 degrees) with electroanatomic guidance. Absence of inducible AF and voltage reduction within ablation circles was considered a satisfactory endpoint. Electrical isolation was not attempted and vagal innervation was not directly targeted.
Thirty patients were recruited, 5 female, mean age 54±9 years. Eight presented for ablation with persistent AF precluding pre-ablation recording. Acute procedural endpoints were achieved in all pts. WACA resulted in marked substrate change as evidenced by increased P wave duration (PWD), reduction in root mean square of the terminal 30ms of the SAPW (RMS) and reduced P wave energy within 30-150Hz and 60-150Hz (P30,P60 in µV² sec). HRV parameters were also significantly influenced with heart rate rise and reduction in standard deviation of RR intervals (SD). Additionally power was reduced in high (HF) and low (LF) frequencies (table). Follow-up was available on 26 pts, mean 8.6 months (range 3-12). Symptomatic recurrence occurred in 8 (31%); documented AF in 5 (19%). Patients with recurrence demonstrated older age, 60.5±5 years vs 49.5±8 years (p=0.003), longer PWD (169.1(11)ms vs 156.3(3)ms (p=0.143)) and absence of mean heart rate rise (+1.8±12bpm vs +17.5±8bpm (p=0.007)). Age and heart rate predicted recurrence (p=0.009).
CONCLUSIONS: The SAPW exhibits marked change after WACA. Variables derived from high resolution recordings provide a measure of substrate and autonomic change. Younger age and increase in heart rate after ablation were associated with long-term success.
|
|
HR |
PWD |
P30 |
P60 |
RMS |
SD |
HF |
LF |
|
Pre |
61.7 (2.0) |
151.6 (4.8) |
19.2 (2.5) |
2.5 (0.3) |
3.8 (0.3) |
50.5 (10.8) |
4.45 (0.3) |
5.62 (0.3) |
|
Post |
74.8 (1.8) |
164.2 (4.0) |
15.7 (1.6) |
2.0 (0.2) |
2.4 (0.3) |
23.5 (3.4) |
3.33 (0.3) |
3.52 (0.3) |
|
|
0.0001 |
0.002 |
0.001 |
0.020 |
0.0001 |
0.014 |
0.046 |
0.0001 |