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S126 Abstracts Heart, Lung and Circulation2008;17S:S1–S209

300Reversal of Chronic Atrial Stretch in Humans: Implica-tions for the Atrial Fibrillation Substrate

Bobby John 1,∗, Martin Stiles 1, Sunil Chandy 2, PawelKuklik 1, Anthony Brooks 1, Dennis Lau 1, Hany Dimitri 1,Muyad Alasady 1, Daryl Leong 1, Glenn Young 1, JonathanKalman 3, Prashanthan Sanders 1

1 Cardiovascular Research Centre, Royal Adelaide Hospital,Disciplines of Medicine and Physiology, University of Ade-laide, Adelaide, South Australia, Australia; 2 Christian MedicalCollege, Vellore, Tamil Nadu, India; 3 Department of Cardiol-ogy, Royal Melbourne Hospital and Discipiline of Medicine,University of Melbourne, Melbourne, Victoria, Australia

Introduction: Chronic atrial stretch is a determinant foratrial fibrillation (AF). Whether relief of stretch reversesthe substrate predisposing to AF is unknown.Methods: Twenty-one patients with mitral stenosis (MS;MVA 0.89 ± 0.1 cm2) undergoing mitral commissurotomy(MC) were studied before and after MC. Catheters placedat the lateral RA, crista terminalis (CT), coronary sinus(CS), septal RA and LA to determine: 10 ERP sites at 600and 450 ms; conduction time along LA roof, inferior LA, CSand lateral RA; CSNRT; and conduction along CT (DP/FS).Bi-atrial electroanatomic maps created in sinus rhythmfurther evaluated conduction and structural changes. In 14patients, RA studies were repeated ≥6 months after MC.

301Acute Effect of Chronic Stretch Reversal on PulmonaryVein Remodeling

Bobby John ∗, Martin Stiles, Pawel Kuklik, Dennis Lau,Hany Dimitri, Anthony Brooks, Lauren Wilson, GlennYoung, Prashanthan Sanders

Cardiovascular Research Centre, Royal Adelaide Hospital, andDisciplines of Medicine and Physiology, University of Adelaide,Adelaide, South Australia, Australia

Introduction: Chronic atrial stretch has been implicated asa cause for atrial fibrillation in humans. Whether reversalof stretch is associated with reversal of pulmonary vein(PV) remodelling is not known.Methods: Ten patients (29 ± 8 years) with rheumatic mitralstenosis (MS) (area 0.83 ± 0.1 cm2) undergoing percuta-neous mitral commissurotomy (MC) were studied. Amulti-electrode basket catheter performed high-densitymapping of the PV. The effective refractory period (ERP)and conduction time (CT) were determined by proxi-mal and distal PV pacing. Intra-PV conduction block (CB;≥30 ms between adjacent bipoles) was assessed by creat-ing an activation map.Results: Following MC, mitral valve area increased(2.1 ± 0.4 cm2, p < 0.0001) with reduction of left atrialpressure (31 ± 4 mmHg–15 ± 4 mmHg, p < 0.0001) and vol-ume (70 ± 25 mL–53 ± 21 mL, p = 0.01) This was associated

Results: Following MC, MVA increased (2.1 ± 0.3 cm2,p < 0.0001) with decreased LA pressure (23 ± 8 to10 ± 4 mm Hg, p < 0.0001); PA pressures (38 ± 17 to27 ± 14 mm Hg, p < 0.0001) and LA volume (75 ± 12 to52 ± 13 mL, p < 0.0001). There was reduction in P-waveduration (PWD) (139 ± 19 to 135 ± 20 ms, p = 0.047),increase in conduction velocity (CV) in LA (1.3 ± 0.3to 1.7 ± 0.2 m/s, p = 0.005) and increase in LA voltage(1.7 ± 0.6 to 2.5 ± 1.0 mV, p = 0.05) but with no change inERP and number of DP/FS along CT. Late after MC, therewas further decrease in PWD and ERP, with increasein CV (1.0 ± 0.1 to 1.3 ± 0.2 m/s, p = 0.01) and voltage(1.7 ± 0.7 to 2.8 ± 0.6 mV, p = 0.004) with no change in otherparameters.Conclusion: The electrophysiologic and electroanatomicabnormalities within the atria that result from MS arereversed after MC. These observations suggest that thesubstrate predisposing to atrial arrhythmias may bereversed.

PRE MC, n = 14 FOLLOW UP, n = 14 P-value (ANOVA)

PWD (ms) 136.9 ± 22.1 113.2 ± 19.1 0.04

RA ERP (ms) 227.9 ± 18.8 204.8 ± 21.6 0.0006

Number cristaDP/FS (LRApacing)

7.8 ± 1.6 5.4 ± 2.2 0.3

Crista DP/FSduration (LRApacing)

82.2 ± 25.7 68.9 ± 13.6 0.14

RA CV (m/s) 1.0 ± 0.1 1.3 ± 0.2 0.01

RA voltage (mV) 1.7 ± 0.7 2.8 ± 0.6 0.004

doi:10.1016/j.hlc.2008.05.301

with no change in ERP or intra-PV CB, but with sig-nificant reduction in conduction time both in sinusrhythm (41 ± 9 ms–34 ± 9 ms, p = 0.04) and when pac-ing distal PV. Additionally, bipolar voltage increased(1.2 ± 0.4 mV–1.5 ± 0.6 mV, p = 0.007).Conclusion: Reversal of stretch is characterized byimprovement in conduction time and an increase in bipo-lar voltage of the PV. These findings suggest that stretchreversal may alter the triggers of AF.

Pre-MC Post-MC P value

Distal ERP (ms) 278 ± 37 259 ± 34 0.9

Proximal ERP (ms) 270 ± 39 253 ± 18 1.0

Distal conduction time (ms) 63 ± 8 53 ± 9 0.01

Proximal conduction time (ms) 54 ± 15 46 ± 12 0.03

Intra-PV CB proximal S2 (ms) 55 ± 34 60 ± 19 0.9

Intra-PV CB distal S2 (ms) 59 ± 24 48 ± 12 0.09

doi:10.1016/j.hlc.2008.05.302