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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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Spatial representation of sub-endocardial electrogram parameters during sub-endocardial pacing from the apex (left panels) and base of the left ventricle (right panels).Two dimensional space is based on spherical coordinates derived from needle locations, representing elevation (−1 =  apex to +1 =  base), and azimuth (−2 =  mid lateral to +2 =  anterior). Numbered contours represent parameters derived from unipolar contact electrograms represented in milliseconds (ms) for activation time (AT) and millivolts (mV) for V-P and VP-P corresponding to panels from top to bottom respectively. Solid arrows represent preferential path of activation. Dotted arrows represent the approximate electrophysiological gradient of V-P and VP-P away from the stimulus site.
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pone-0110399-g004: Spatial representation of sub-endocardial electrogram parameters during sub-endocardial pacing from the apex (left panels) and base of the left ventricle (right panels).Two dimensional space is based on spherical coordinates derived from needle locations, representing elevation (−1 =  apex to +1 =  base), and azimuth (−2 =  mid lateral to +2 =  anterior). Numbered contours represent parameters derived from unipolar contact electrograms represented in milliseconds (ms) for activation time (AT) and millivolts (mV) for V-P and VP-P corresponding to panels from top to bottom respectively. Solid arrows represent preferential path of activation. Dotted arrows represent the approximate electrophysiological gradient of V-P and VP-P away from the stimulus site.

Mentions: Propagation distance affected unipolar V-P to a greater extent than VP-P, amounting to a relative amplitude reduction of 56% and 43% respectively, at distances of 8 cm from the stimulus source. In contrast, unfiltered and filtered bipolar electrograms exhibited a relatively minor 18% and 14% reduction in amplitudes of V-P and VP-P respectively, recorded at the same distances. Representation of unipolar V-P, and VP-P during pacing from the cardiac apex and base is illustrated in figure 4. Corresponding to the sequence of activation during stimulation from the apex, attenuation of these parameters is observed towards the base, whereas the converse occurred during basal pacing.


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)

Spatial representation of sub-endocardial electrogram parameters during sub-endocardial pacing from the apex (left panels) and base of the left ventricle (right panels).Two dimensional space is based on spherical coordinates derived from needle locations, representing elevation (−1 =  apex to +1 =  base), and azimuth (−2 =  mid lateral to +2 =  anterior). Numbered contours represent parameters derived from unipolar contact electrograms represented in milliseconds (ms) for activation time (AT) and millivolts (mV) for V-P and VP-P corresponding to panels from top to bottom respectively. Solid arrows represent preferential path of activation. Dotted arrows represent the approximate electrophysiological gradient of V-P and VP-P away from the stimulus site.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0110399-g004: Spatial representation of sub-endocardial electrogram parameters during sub-endocardial pacing from the apex (left panels) and base of the left ventricle (right panels).Two dimensional space is based on spherical coordinates derived from needle locations, representing elevation (−1 =  apex to +1 =  base), and azimuth (−2 =  mid lateral to +2 =  anterior). Numbered contours represent parameters derived from unipolar contact electrograms represented in milliseconds (ms) for activation time (AT) and millivolts (mV) for V-P and VP-P corresponding to panels from top to bottom respectively. Solid arrows represent preferential path of activation. Dotted arrows represent the approximate electrophysiological gradient of V-P and VP-P away from the stimulus site.
Mentions: Propagation distance affected unipolar V-P to a greater extent than VP-P, amounting to a relative amplitude reduction of 56% and 43% respectively, at distances of 8 cm from the stimulus source. In contrast, unfiltered and filtered bipolar electrograms exhibited a relatively minor 18% and 14% reduction in amplitudes of V-P and VP-P respectively, recorded at the same distances. Representation of unipolar V-P, and VP-P during pacing from the cardiac apex and base is illustrated in figure 4. Corresponding to the sequence of activation during stimulation from the apex, attenuation of these parameters is observed towards the base, whereas the converse occurred during basal pacing.

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