Relationships between myocardial activity and potentials on the ventricular surfaces.
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Action Potentials↗
Biomedical subjects
B B Punske
Publications and source records attributed to B B Punske.
A comparison of simulated QRS isointegral maps resulting from pacing at adjacent sites: implications for the spatial resolution of pace mapping using body surface potentials.
The precise localization of ventricular tachycardia (VT) foci is a prerequisite for the successful radiofrequency catheter ablation in patients. The purpose of this study was to systematically quantify over what distance adjacent sites in the right ventricular (RV) and left ventricular (LV) epicardium and LV endocardium could be distinguished by inspecting morphological features of QRS isointegral maps using statistical methods. We investigated the spatial resolution of QRS isointegral maps by means of an anatomically accurate computer model of the human ventricular myocardium that incorporates a bidomain model for simulating the realistic activation sequences and the oblique dipole model in combination with the boundary element method for calculating extracardiac potentials. In this model, we initiated activation sequences at a total of 183 epicardial and 75 LV endocardial pacing sites, positioned in three levels (basal, middle, and apical). For each of the 258 pacing sites, we calculated a set of 10 QRS isointegral maps with added Gaussian noise at 117 leads (covering the anterior and posterior torso) and at 32 leads (covering only the anterior torso), respectively. Sets of maps were then cross correlated and root-mean-square (RMS) values of difference maps were calculated for all possible pairs of pacing sites on the same level. We applied the nonparametric unpaired Kolmogorov-Smirnov test and defined the spatial resolution as the pacing site separation at which the differences in correlation coefficients and RMS differences were significant (level P < .05). We observed significant differences in maps when the distances between pacing sites were on average (+/- SD) greater than 4.3 +/- 1.0 mm. In more than 90% of pacing sites, the significant differences in maps were observed within 4 mm even when using a 32-lead mapping system. The findings of our study provide theoretical evidence that QRS isointegral maps may offer noninvasive means for preinterventional planning of the ablative treatment in localizing both endocardial and epicardial sites of origin of VT.
Body Surface Potential Mapping↗
Useful lessons from body surface mapping.
Useful Lessons from Body Surface Mapping. Body surface potential maps (BSMs) depict the time varying distribution of cardiac potentials on the entire surface of the torso. Hundreds of studies have shown that BSMs contain more diagnostic and prognostic information than can be elicited from the 12-lead ECG. Despite these advantages, body surface mapping has not become a routinely used clinical method. One reason is that visual examination and sophisticated analysis of BSMs do not permit inferring the sequence of excitation and repolarization in the heart with a sufficient degree of certainty and detail. These limitations can be partially overcome by implementing inverse procedures that reconstruct epicardial potentials, isochrones, and ECGs from body surface measurements. Furthermore, ongoing experimental work and simulation studies show that a great deal of information about intramural events can be elicited from measured or reconstructed epicardial potential distributions. Interpreting epicardial data in terms of deep activity requires extensive knowledge of the architecture of myocardial fibers, their anisotropic properties, and the role of rotational anisotropy in affecting propagation and the associated potential fields.
Body Surface Potential Mapping↗
Quantitative characterization of epicardial wave fronts during regional ischemia and elevated extracellular potassium ion concentration.
This study applied zero-delay wave number spectral estimation as a means of quantifying the changes in activation and recovery sequences of propagating plane waves on the epicardial surface of in situ porcine hearts during regional hyperkalemia and ischemia. Unipolar electrograms (104) were recorded from the left ventricular surface of nine hearts using a plaque electrode array with 1 mm spatial sampling intervals. The objectives were (1) to define a set of parameters capable of quantifying the spatial and temporal changes in measured extracellular potentials associated with localized ischemia prior to the onset of conduction block; (2) to elevate regional levels of extracellular potassium ion concentration and quantify potential changes due to this known physiologic manipulation; and (3) to use quantitative parameters to make statistical comparisons in order to distinguish wave fronts during normal, ischemic and hyperkalemic conditions. Results showed that the parameters of wave number and average temporal frequency and the associated power, as determined from the wave number spectrum, provided statistically significant (p<0.05) quantification of changes in wave front features during normal and ischemic or hyperkalemic conditions. The results were consistent with results obtained from conventional time-space domain methods like isochronal mapping and electrograms, with the advantage of a quantitative result enabling simple comparisons and trend analysis for large numbers of heart beats.
Animals↗