Characterisation of Direction-dependent Conduction Abnormalities Predisposing to Atrial Arrhythmias

Abstract

Methods:Mappingwasperformed in eight sheeps, 60± 54 weeks post-MI. Twenty multielectrode needles were deployed at thoracotomy in the left ventricle within and surrounding scar. Needles were located using EnsiteTM. Endocardial contact (needle) and noncontact unipolar electrograms were recorded simultaneously during SR and multisite pacing. DSM maps were calculated as a ratiometric consensus of peak negative voltage (PNV). ADSM maps were calculated using a root mean square consensus of peak–peak voltage (P2PV). Scar was quantified histologically and correlated with mapping criteria using receiver operator curves with 50% scar density cutoff. Results: All modalities could identify scar (symbols †p 2mA=29± 8%, AUC=0.93†) and conduction delay (ADSM%, ≤30ms= 63± 19%, >30ms= 45± 23%, AUC=0.72‡) were associated with decreased ADSM%. ADSM sensitivity was improved with limited distance from the array (r< 40mm, AUC=0.74†). Conclusions: ADSM is more reliable in detecting scar p< 0.001); delayed activation in the high-posterior (78± 14ms vs. 46± 15ms, p< 0.05), high-septal (81± 27ms vs. 46± 7ms, p< 0.05) and low-septal RA (87± 41ms vs. 42± 13ms, p< 0.05); greater proportion of DP/FS (48% vs. 7%, p< 0.001) and lower regional voltage (1.4± 0.3mV vs. 2.1± 0.5mV, p< 0.005) compared to SR. Anatomical regions of FS correlated with regions of low voltage (r=−0.63, p= 0.01). Septal-paced and SR-maps showed lines of block at: the crista terminalis (10 vs. 11), septum (8 vs. 2, p= 0.02), lateral RA (4 vs. 1), eustachian ridge (2 vs. 0) and appendage (1 vs. 0). Septal-paced maps identified significantly more lines (25 vs. 14, p= 0.03) of greater length (60± 27mm vs. 43± 12mm, p< 0.05). Additionally, the crista terminalis identified in septal-paced maps was significantly longer (80± 24mm vs. 42± 10mm, p< 0.001). Conclusions: Direction-dependent analysis revealed significant changes in regional conduction velocities, voltage and fractionation. These heterogeneous changes suggest ectopy from septal sites may be more likely to initiate arrhythmiabyconductingaroundareasof functionalblock to promote re-entry. doi:10.1016/j.hlc.2008.05.283