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Spatial characterization of electrogram morphology from transmural recordings in the intact normal heart.

Pouliopoulos J, Chik W, Byth K, Wallace E, Kovoor P, Thiagalingam A - PLoS ONE (2014)

Bottom Line: Increasing distance from the pacing sites led to significant (p<0.01) attenuation of UEs (V-P = 7.0±0.5%; VP-P = 5.4±0.3% per cm).Attenuation of BE with distance was insignificant (Vp-p unfiltered = 2.2±0.5%; filtered = 1.7±1.4% per cm).Independent of pacing depth, significant (p<0.01) transmural electrophysiological gradients were observed, with highest amplitude occurring at epicardial layers for UE and endocardial layers for BE.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology, Westmead Hospital, Sydney, Australia; The University of Sydney, Sydney, Australia.

ABSTRACT

Purpose: Unipolar (UE) and bipolar electrograms (BE) are utilized to identify arrhythmogenic substrate. We quantified the effect of increasing distance from the source of propagation on local electrogram amplitude; and determined if transmural electrophysiological gradients exist with respect to propagation and stimulation depth.

Methods: Mapping was performed on 5 sheep. Deployment of >50 quadripolar transmural needles in the LV were located in Cartesian space using Ensite. Contact electrograms from all needles were recorded during multisite bipolar pacing from epicardial then endocardial electrodes. Analysis was performed to determine stimulus distance to local activation time, peak negative amplitude (V-P), and peak-peak amplitude (VP-P) for (1) unfiltered UE, and (2) unfiltered and 30 Hz high-pass filtered BEs. Each sheep was analysed using repeated ANOVA.

Results: Increasing distance from the pacing sites led to significant (p<0.01) attenuation of UEs (V-P = 7.0±0.5%; VP-P = 5.4±0.3% per cm). Attenuation of BE with distance was insignificant (Vp-p unfiltered = 2.2±0.5%; filtered = 1.7±1.4% per cm). Independent of pacing depth, significant (p<0.01) transmural electrophysiological gradients were observed, with highest amplitude occurring at epicardial layers for UE and endocardial layers for BE. Furthermore, during pacing, propagation was earlier at the epicardium than endocardial layer by 1.6±2.0 ms (UE) and 1.4±2.8 ms (BE) (all p>0.01) during endocardial stimulation, and 2.3±2.4 ms (UE) and 1.8±3.7 ms (BE) during epicardal stimulation (all p<0.01).

Conclusions: Electrogram amplitude is inversely proportional to propagation distance for unipolar modalities only, which affected V-P>VP-P. Conduction propagates preferentially via the epicardium during stimulation and is believed to contribute to a transmural amplitude gradient.

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Two representative stained histological sections using haematoxylin-eosin of normal myocardium from different sites in the Ovine left ventricle.Left: unprocessed image. Right: convolved images identifying transmural anisotropy vectors in two dimensions from multiple sites indicated (circles) within each section. Circles arranged from epicardium (top) to endocardium (bottom). Anisotropy vectors orientated vertically at epicardial layer with distinct transitioning to horizontal orientation at the mid myocardial layer followed by diagonal orientation at the endocardial layer.
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pone-0110399-g006: Two representative stained histological sections using haematoxylin-eosin of normal myocardium from different sites in the Ovine left ventricle.Left: unprocessed image. Right: convolved images identifying transmural anisotropy vectors in two dimensions from multiple sites indicated (circles) within each section. Circles arranged from epicardium (top) to endocardium (bottom). Anisotropy vectors orientated vertically at epicardial layer with distinct transitioning to horizontal orientation at the mid myocardial layer followed by diagonal orientation at the endocardial layer.

Mentions: Upon histological examination of the left ventricular wall, three distinct orientations of the myofibre architecture were observed (Figure 6). Tissue processing resulted in an approximate 10% reduction in volume. The cellular orientations were readily observable because the reduction in volume post processing resulted in separation of myocytes at cleavage sites, thus revealing two orthogonal bands of myofibres. At the epicardial layers, the myofibres were distinctly organised in a normal (epicardial-endocardial) vector to the plane of the myocardial layers. In contrary, fibre orientations were distinctly parallel at the mid myocardium while anisotropy at the endocardium level displayed greater inhomogeneity.


Spatial characterization of electrogram morphology from transmural recordings in the intact normal heart.

Pouliopoulos J, Chik W, Byth K, Wallace E, Kovoor P, Thiagalingam A - PLoS ONE (2014)

Two representative stained histological sections using haematoxylin-eosin of normal myocardium from different sites in the Ovine left ventricle.Left: unprocessed image. Right: convolved images identifying transmural anisotropy vectors in two dimensions from multiple sites indicated (circles) within each section. Circles arranged from epicardium (top) to endocardium (bottom). Anisotropy vectors orientated vertically at epicardial layer with distinct transitioning to horizontal orientation at the mid myocardial layer followed by diagonal orientation at the endocardial layer.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4215922&req=5

pone-0110399-g006: Two representative stained histological sections using haematoxylin-eosin of normal myocardium from different sites in the Ovine left ventricle.Left: unprocessed image. Right: convolved images identifying transmural anisotropy vectors in two dimensions from multiple sites indicated (circles) within each section. Circles arranged from epicardium (top) to endocardium (bottom). Anisotropy vectors orientated vertically at epicardial layer with distinct transitioning to horizontal orientation at the mid myocardial layer followed by diagonal orientation at the endocardial layer.
Mentions: Upon histological examination of the left ventricular wall, three distinct orientations of the myofibre architecture were observed (Figure 6). Tissue processing resulted in an approximate 10% reduction in volume. The cellular orientations were readily observable because the reduction in volume post processing resulted in separation of myocytes at cleavage sites, thus revealing two orthogonal bands of myofibres. At the epicardial layers, the myofibres were distinctly organised in a normal (epicardial-endocardial) vector to the plane of the myocardial layers. In contrary, fibre orientations were distinctly parallel at the mid myocardium while anisotropy at the endocardium level displayed greater inhomogeneity.

Bottom Line: Increasing distance from the pacing sites led to significant (p<0.01) attenuation of UEs (V-P = 7.0±0.5%; VP-P = 5.4±0.3% per cm).Attenuation of BE with distance was insignificant (Vp-p unfiltered = 2.2±0.5%; filtered = 1.7±1.4% per cm).Independent of pacing depth, significant (p<0.01) transmural electrophysiological gradients were observed, with highest amplitude occurring at epicardial layers for UE and endocardial layers for BE.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology, Westmead Hospital, Sydney, Australia; The University of Sydney, Sydney, Australia.

ABSTRACT

Purpose: Unipolar (UE) and bipolar electrograms (BE) are utilized to identify arrhythmogenic substrate. We quantified the effect of increasing distance from the source of propagation on local electrogram amplitude; and determined if transmural electrophysiological gradients exist with respect to propagation and stimulation depth.

Methods: Mapping was performed on 5 sheep. Deployment of >50 quadripolar transmural needles in the LV were located in Cartesian space using Ensite. Contact electrograms from all needles were recorded during multisite bipolar pacing from epicardial then endocardial electrodes. Analysis was performed to determine stimulus distance to local activation time, peak negative amplitude (V-P), and peak-peak amplitude (VP-P) for (1) unfiltered UE, and (2) unfiltered and 30 Hz high-pass filtered BEs. Each sheep was analysed using repeated ANOVA.

Results: Increasing distance from the pacing sites led to significant (p<0.01) attenuation of UEs (V-P = 7.0±0.5%; VP-P = 5.4±0.3% per cm). Attenuation of BE with distance was insignificant (Vp-p unfiltered = 2.2±0.5%; filtered = 1.7±1.4% per cm). Independent of pacing depth, significant (p<0.01) transmural electrophysiological gradients were observed, with highest amplitude occurring at epicardial layers for UE and endocardial layers for BE. Furthermore, during pacing, propagation was earlier at the epicardium than endocardial layer by 1.6±2.0 ms (UE) and 1.4±2.8 ms (BE) (all p>0.01) during endocardial stimulation, and 2.3±2.4 ms (UE) and 1.8±3.7 ms (BE) during epicardal stimulation (all p<0.01).

Conclusions: Electrogram amplitude is inversely proportional to propagation distance for unipolar modalities only, which affected V-P>VP-P. Conduction propagates preferentially via the epicardium during stimulation and is believed to contribute to a transmural amplitude gradient.

Show MeSH