Regionalisation of steep restitution slopes and ventricular tachycardia circuits

Sunni, N., Yue, A., Michael, K., Allen, S., Roberts, P. and Morgan, J. (2006) Regionalisation of steep restitution slopes and ventricular tachycardia circuits. Heart, 92 (Supplement 2), A57-A58.

Abstract

Introduction: Electrical instability and arrhythmogenesis have been linked to the steepness of the action potential duration restitution curve slope in experimental and animal models. Inducibility of re-entry ventricular tachycardia may be associated with the steepness of the restitution slopes but this is yet to be established in pathological human hearts.
Methods: Global activation recovery interval (ARI) restitution curves were constructed from virtual unipolar electrograms from 16 sites in the right or left ventricle of 7 patients (age 49 (21) years, 4 male) with ischaemic (2), nonischaemic (2) cardiomyopathies and fascicular ventricular tachycardia (3) and a mean ejection fraction of 48% (22)%. All patients had inducible sustained monomorphic ventricular tachycardia and underwent ventricular tachycardia ablation with the Ensite 3000 noncontact mapping (NCM) system. Standard S1-S2 restitution curves were constructed from pacing at the right ventricular apex. Maximum slopes (Smax) for the ARI restitution curves were formulated using the overlapping linear segments method. Dispersion of Smax was defined by the standard deviation.
Results: 1680 beats were analysed; mean ARI at steady state was 213 (SD 33) ms and at shortest coupling interval 183 (32) ms, mean overall Smax was 0.89 (0.25). The Smax was >1 at 20% of the sites. Dispersion of Smax 0.35 (0.14). However, the distribution of Smax was not uniform and appeared regionalised. In 6 of the 7 patients; ventricular segments at which ablation was successful in terminating the VT demonstrated the steepest ARI restitution slopes. The mean Smax for ventricular segments with the ablated sites was 1.64 (0.5). The mean distance between sites where Smax were determined and successful ablation sites was 19 (13) mm.
Conclusion: Steep ARI restitution slopes are regionalised in pathological hearts. Regional differences in electrical restitution may be masked by global analysis. There may be an association between critical pathways of ventricular tachycardia circuits and steep ARI restitution slopes.

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